1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 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) 1988-2017 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 The original port to the OpenRISC 1000 is believed to be due to
550 Alessandro Forin and Per Bothner. More recent ports have been the work
551 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
555 @chapter A Sample @value{GDBN} Session
557 You can use this manual at your leisure to read all about @value{GDBN}.
558 However, a handful of commands are enough to get started using the
559 debugger. This chapter illustrates those commands.
562 In this sample session, we emphasize user input like this: @b{input},
563 to make it easier to pick out from the surrounding output.
566 @c FIXME: this example may not be appropriate for some configs, where
567 @c FIXME...primary interest is in remote use.
569 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
570 processor) exhibits the following bug: sometimes, when we change its
571 quote strings from the default, the commands used to capture one macro
572 definition within another stop working. In the following short @code{m4}
573 session, we define a macro @code{foo} which expands to @code{0000}; we
574 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
575 same thing. However, when we change the open quote string to
576 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
577 procedure fails to define a new synonym @code{baz}:
586 @b{define(bar,defn(`foo'))}
590 @b{changequote(<QUOTE>,<UNQUOTE>)}
592 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
595 m4: End of input: 0: fatal error: EOF in string
599 Let us use @value{GDBN} to try to see what is going on.
602 $ @b{@value{GDBP} m4}
603 @c FIXME: this falsifies the exact text played out, to permit smallbook
604 @c FIXME... format to come out better.
605 @value{GDBN} is free software and you are welcome to distribute copies
606 of it under certain conditions; type "show copying" to see
608 There is absolutely no warranty for @value{GDBN}; type "show warranty"
611 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
616 @value{GDBN} reads only enough symbol data to know where to find the
617 rest when needed; as a result, the first prompt comes up very quickly.
618 We now tell @value{GDBN} to use a narrower display width than usual, so
619 that examples fit in this manual.
622 (@value{GDBP}) @b{set width 70}
626 We need to see how the @code{m4} built-in @code{changequote} works.
627 Having looked at the source, we know the relevant subroutine is
628 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
629 @code{break} command.
632 (@value{GDBP}) @b{break m4_changequote}
633 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
637 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
638 control; as long as control does not reach the @code{m4_changequote}
639 subroutine, the program runs as usual:
642 (@value{GDBP}) @b{run}
643 Starting program: /work/Editorial/gdb/gnu/m4/m4
651 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
652 suspends execution of @code{m4}, displaying information about the
653 context where it stops.
656 @b{changequote(<QUOTE>,<UNQUOTE>)}
658 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
660 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
664 Now we use the command @code{n} (@code{next}) to advance execution to
665 the next line of the current function.
669 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
674 @code{set_quotes} looks like a promising subroutine. We can go into it
675 by using the command @code{s} (@code{step}) instead of @code{next}.
676 @code{step} goes to the next line to be executed in @emph{any}
677 subroutine, so it steps into @code{set_quotes}.
681 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 530 if (lquote != def_lquote)
687 The display that shows the subroutine where @code{m4} is now
688 suspended (and its arguments) is called a stack frame display. It
689 shows a summary of the stack. We can use the @code{backtrace}
690 command (which can also be spelled @code{bt}), to see where we are
691 in the stack as a whole: the @code{backtrace} command displays a
692 stack frame for each active subroutine.
695 (@value{GDBP}) @b{bt}
696 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
698 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
700 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
701 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
703 #4 0x79dc in expand_input () at macro.c:40
704 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
708 We step through a few more lines to see what happens. The first two
709 times, we can use @samp{s}; the next two times we use @code{n} to avoid
710 falling into the @code{xstrdup} subroutine.
714 0x3b5c 532 if (rquote != def_rquote)
716 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
717 def_lquote : xstrdup(lq);
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
726 The last line displayed looks a little odd; we can examine the variables
727 @code{lquote} and @code{rquote} to see if they are in fact the new left
728 and right quotes we specified. We use the command @code{p}
729 (@code{print}) to see their values.
732 (@value{GDBP}) @b{p lquote}
733 $1 = 0x35d40 "<QUOTE>"
734 (@value{GDBP}) @b{p rquote}
735 $2 = 0x35d50 "<UNQUOTE>"
739 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
740 To look at some context, we can display ten lines of source
741 surrounding the current line with the @code{l} (@code{list}) command.
747 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
749 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
752 538 len_lquote = strlen(rquote);
753 539 len_rquote = strlen(lquote);
760 Let us step past the two lines that set @code{len_lquote} and
761 @code{len_rquote}, and then examine the values of those variables.
765 539 len_rquote = strlen(lquote);
768 (@value{GDBP}) @b{p len_lquote}
770 (@value{GDBP}) @b{p len_rquote}
775 That certainly looks wrong, assuming @code{len_lquote} and
776 @code{len_rquote} are meant to be the lengths of @code{lquote} and
777 @code{rquote} respectively. We can set them to better values using
778 the @code{p} command, since it can print the value of
779 any expression---and that expression can include subroutine calls and
783 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
785 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
790 Is that enough to fix the problem of using the new quotes with the
791 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
792 executing with the @code{c} (@code{continue}) command, and then try the
793 example that caused trouble initially:
799 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
806 Success! The new quotes now work just as well as the default ones. The
807 problem seems to have been just the two typos defining the wrong
808 lengths. We allow @code{m4} exit by giving it an EOF as input:
812 Program exited normally.
816 The message @samp{Program exited normally.} is from @value{GDBN}; it
817 indicates @code{m4} has finished executing. We can end our @value{GDBN}
818 session with the @value{GDBN} @code{quit} command.
821 (@value{GDBP}) @b{quit}
825 @chapter Getting In and Out of @value{GDBN}
827 This chapter discusses how to start @value{GDBN}, and how to get out of it.
831 type @samp{@value{GDBP}} to start @value{GDBN}.
833 type @kbd{quit} or @kbd{Ctrl-d} to exit.
837 * Invoking GDB:: How to start @value{GDBN}
838 * Quitting GDB:: How to quit @value{GDBN}
839 * Shell Commands:: How to use shell commands inside @value{GDBN}
840 * Logging Output:: How to log @value{GDBN}'s output to a file
844 @section Invoking @value{GDBN}
846 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
847 @value{GDBN} reads commands from the terminal until you tell it to exit.
849 You can also run @code{@value{GDBP}} with a variety of arguments and options,
850 to specify more of your debugging environment at the outset.
852 The command-line options described here are designed
853 to cover a variety of situations; in some environments, some of these
854 options may effectively be unavailable.
856 The most usual way to start @value{GDBN} is with one argument,
857 specifying an executable program:
860 @value{GDBP} @var{program}
864 You can also start with both an executable program and a core file
868 @value{GDBP} @var{program} @var{core}
871 You can, instead, specify a process ID as a second argument, if you want
872 to debug a running process:
875 @value{GDBP} @var{program} 1234
879 would attach @value{GDBN} to process @code{1234} (unless you also have a file
880 named @file{1234}; @value{GDBN} does check for a core file first).
882 Taking advantage of the second command-line argument requires a fairly
883 complete operating system; when you use @value{GDBN} as a remote
884 debugger attached to a bare board, there may not be any notion of
885 ``process'', and there is often no way to get a core dump. @value{GDBN}
886 will warn you if it is unable to attach or to read core dumps.
888 You can optionally have @code{@value{GDBP}} pass any arguments after the
889 executable file to the inferior using @code{--args}. This option stops
892 @value{GDBP} --args gcc -O2 -c foo.c
894 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
895 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
897 You can run @code{@value{GDBP}} without printing the front material, which describes
898 @value{GDBN}'s non-warranty, by specifying @code{--silent}
899 (or @code{-q}/@code{--quiet}):
902 @value{GDBP} --silent
906 You can further control how @value{GDBN} starts up by using command-line
907 options. @value{GDBN} itself can remind you of the options available.
917 to display all available options and briefly describe their use
918 (@samp{@value{GDBP} -h} is a shorter equivalent).
920 All options and command line arguments you give are processed
921 in sequential order. The order makes a difference when the
922 @samp{-x} option is used.
926 * File Options:: Choosing files
927 * Mode Options:: Choosing modes
928 * Startup:: What @value{GDBN} does during startup
932 @subsection Choosing Files
934 When @value{GDBN} starts, it reads any arguments other than options as
935 specifying an executable file and core file (or process ID). This is
936 the same as if the arguments were specified by the @samp{-se} and
937 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
938 first argument that does not have an associated option flag as
939 equivalent to the @samp{-se} option followed by that argument; and the
940 second argument that does not have an associated option flag, if any, as
941 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
942 If the second argument begins with a decimal digit, @value{GDBN} will
943 first attempt to attach to it as a process, and if that fails, attempt
944 to open it as a corefile. If you have a corefile whose name begins with
945 a digit, you can prevent @value{GDBN} from treating it as a pid by
946 prefixing it with @file{./}, e.g.@: @file{./12345}.
948 If @value{GDBN} has not been configured to included core file support,
949 such as for most embedded targets, then it will complain about a second
950 argument and ignore it.
952 Many options have both long and short forms; both are shown in the
953 following list. @value{GDBN} also recognizes the long forms if you truncate
954 them, so long as enough of the option is present to be unambiguous.
955 (If you prefer, you can flag option arguments with @samp{--} rather
956 than @samp{-}, though we illustrate the more usual convention.)
958 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
959 @c way, both those who look for -foo and --foo in the index, will find
963 @item -symbols @var{file}
965 @cindex @code{--symbols}
967 Read symbol table from file @var{file}.
969 @item -exec @var{file}
971 @cindex @code{--exec}
973 Use file @var{file} as the executable file to execute when appropriate,
974 and for examining pure data in conjunction with a core dump.
978 Read symbol table from file @var{file} and use it as the executable
981 @item -core @var{file}
983 @cindex @code{--core}
985 Use file @var{file} as a core dump to examine.
987 @item -pid @var{number}
988 @itemx -p @var{number}
991 Connect to process ID @var{number}, as with the @code{attach} command.
993 @item -command @var{file}
995 @cindex @code{--command}
997 Execute commands from file @var{file}. The contents of this file is
998 evaluated exactly as the @code{source} command would.
999 @xref{Command Files,, Command files}.
1001 @item -eval-command @var{command}
1002 @itemx -ex @var{command}
1003 @cindex @code{--eval-command}
1005 Execute a single @value{GDBN} command.
1007 This option may be used multiple times to call multiple commands. It may
1008 also be interleaved with @samp{-command} as required.
1011 @value{GDBP} -ex 'target sim' -ex 'load' \
1012 -x setbreakpoints -ex 'run' a.out
1015 @item -init-command @var{file}
1016 @itemx -ix @var{file}
1017 @cindex @code{--init-command}
1019 Execute commands from file @var{file} before loading the inferior (but
1020 after loading gdbinit files).
1023 @item -init-eval-command @var{command}
1024 @itemx -iex @var{command}
1025 @cindex @code{--init-eval-command}
1027 Execute a single @value{GDBN} command before loading the inferior (but
1028 after loading gdbinit files).
1031 @item -directory @var{directory}
1032 @itemx -d @var{directory}
1033 @cindex @code{--directory}
1035 Add @var{directory} to the path to search for source and script files.
1039 @cindex @code{--readnow}
1041 Read each symbol file's entire symbol table immediately, rather than
1042 the default, which is to read it incrementally as it is needed.
1043 This makes startup slower, but makes future operations faster.
1046 @anchor{--readnever}
1047 @cindex @code{--readnever}, command-line option
1048 Do not read each symbol file's symbolic debug information. This makes
1049 startup faster but at the expense of not being able to perform
1050 symbolic debugging. DWARF unwind information is also not read,
1051 meaning backtraces may become incomplete or inaccurate. One use of
1052 this is when a user simply wants to do the following sequence: attach,
1053 dump core, detach. Loading the debugging information in this case is
1054 an unnecessary cause of delay.
1058 @subsection Choosing Modes
1060 You can run @value{GDBN} in various alternative modes---for example, in
1061 batch mode or quiet mode.
1069 Do not execute commands found in any initialization file.
1070 There are three init files, loaded in the following order:
1073 @item @file{system.gdbinit}
1074 This is the system-wide init file.
1075 Its location is specified with the @code{--with-system-gdbinit}
1076 configure option (@pxref{System-wide configuration}).
1077 It is loaded first when @value{GDBN} starts, before command line options
1078 have been processed.
1079 @item @file{~/.gdbinit}
1080 This is the init file in your home directory.
1081 It is loaded next, after @file{system.gdbinit}, and before
1082 command options have been processed.
1083 @item @file{./.gdbinit}
1084 This is the init file in the current directory.
1085 It is loaded last, after command line options other than @code{-x} and
1086 @code{-ex} have been processed. Command line options @code{-x} and
1087 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1090 For further documentation on startup processing, @xref{Startup}.
1091 For documentation on how to write command files,
1092 @xref{Command Files,,Command Files}.
1097 Do not execute commands found in @file{~/.gdbinit}, the init file
1098 in your home directory.
1104 @cindex @code{--quiet}
1105 @cindex @code{--silent}
1107 ``Quiet''. Do not print the introductory and copyright messages. These
1108 messages are also suppressed in batch mode.
1111 @cindex @code{--batch}
1112 Run in batch mode. Exit with status @code{0} after processing all the
1113 command files specified with @samp{-x} (and all commands from
1114 initialization files, if not inhibited with @samp{-n}). Exit with
1115 nonzero status if an error occurs in executing the @value{GDBN} commands
1116 in the command files. Batch mode also disables pagination, sets unlimited
1117 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1118 off} were in effect (@pxref{Messages/Warnings}).
1120 Batch mode may be useful for running @value{GDBN} as a filter, for
1121 example to download and run a program on another computer; in order to
1122 make this more useful, the message
1125 Program exited normally.
1129 (which is ordinarily issued whenever a program running under
1130 @value{GDBN} control terminates) is not issued when running in batch
1134 @cindex @code{--batch-silent}
1135 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1136 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1137 unaffected). This is much quieter than @samp{-silent} and would be useless
1138 for an interactive session.
1140 This is particularly useful when using targets that give @samp{Loading section}
1141 messages, for example.
1143 Note that targets that give their output via @value{GDBN}, as opposed to
1144 writing directly to @code{stdout}, will also be made silent.
1146 @item -return-child-result
1147 @cindex @code{--return-child-result}
1148 The return code from @value{GDBN} will be the return code from the child
1149 process (the process being debugged), with the following exceptions:
1153 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1154 internal error. In this case the exit code is the same as it would have been
1155 without @samp{-return-child-result}.
1157 The user quits with an explicit value. E.g., @samp{quit 1}.
1159 The child process never runs, or is not allowed to terminate, in which case
1160 the exit code will be -1.
1163 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1164 when @value{GDBN} is being used as a remote program loader or simulator
1169 @cindex @code{--nowindows}
1171 ``No windows''. If @value{GDBN} comes with a graphical user interface
1172 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1173 interface. If no GUI is available, this option has no effect.
1177 @cindex @code{--windows}
1179 If @value{GDBN} includes a GUI, then this option requires it to be
1182 @item -cd @var{directory}
1184 Run @value{GDBN} using @var{directory} as its working directory,
1185 instead of the current directory.
1187 @item -data-directory @var{directory}
1188 @itemx -D @var{directory}
1189 @cindex @code{--data-directory}
1191 Run @value{GDBN} using @var{directory} as its data directory.
1192 The data directory is where @value{GDBN} searches for its
1193 auxiliary files. @xref{Data Files}.
1197 @cindex @code{--fullname}
1199 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1200 subprocess. It tells @value{GDBN} to output the full file name and line
1201 number in a standard, recognizable fashion each time a stack frame is
1202 displayed (which includes each time your program stops). This
1203 recognizable format looks like two @samp{\032} characters, followed by
1204 the file name, line number and character position separated by colons,
1205 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1206 @samp{\032} characters as a signal to display the source code for the
1209 @item -annotate @var{level}
1210 @cindex @code{--annotate}
1211 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1212 effect is identical to using @samp{set annotate @var{level}}
1213 (@pxref{Annotations}). The annotation @var{level} controls how much
1214 information @value{GDBN} prints together with its prompt, values of
1215 expressions, source lines, and other types of output. Level 0 is the
1216 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1217 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1218 that control @value{GDBN}, and level 2 has been deprecated.
1220 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1224 @cindex @code{--args}
1225 Change interpretation of command line so that arguments following the
1226 executable file are passed as command line arguments to the inferior.
1227 This option stops option processing.
1229 @item -baud @var{bps}
1231 @cindex @code{--baud}
1233 Set the line speed (baud rate or bits per second) of any serial
1234 interface used by @value{GDBN} for remote debugging.
1236 @item -l @var{timeout}
1238 Set the timeout (in seconds) of any communication used by @value{GDBN}
1239 for remote debugging.
1241 @item -tty @var{device}
1242 @itemx -t @var{device}
1243 @cindex @code{--tty}
1245 Run using @var{device} for your program's standard input and output.
1246 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1248 @c resolve the situation of these eventually
1250 @cindex @code{--tui}
1251 Activate the @dfn{Text User Interface} when starting. The Text User
1252 Interface manages several text windows on the terminal, showing
1253 source, assembly, registers and @value{GDBN} command outputs
1254 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1255 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1256 Using @value{GDBN} under @sc{gnu} Emacs}).
1258 @item -interpreter @var{interp}
1259 @cindex @code{--interpreter}
1260 Use the interpreter @var{interp} for interface with the controlling
1261 program or device. This option is meant to be set by programs which
1262 communicate with @value{GDBN} using it as a back end.
1263 @xref{Interpreters, , Command Interpreters}.
1265 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1266 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1267 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1268 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1269 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1270 @sc{gdb/mi} interfaces are no longer supported.
1273 @cindex @code{--write}
1274 Open the executable and core files for both reading and writing. This
1275 is equivalent to the @samp{set write on} command inside @value{GDBN}
1279 @cindex @code{--statistics}
1280 This option causes @value{GDBN} to print statistics about time and
1281 memory usage after it completes each command and returns to the prompt.
1284 @cindex @code{--version}
1285 This option causes @value{GDBN} to print its version number and
1286 no-warranty blurb, and exit.
1288 @item -configuration
1289 @cindex @code{--configuration}
1290 This option causes @value{GDBN} to print details about its build-time
1291 configuration parameters, and then exit. These details can be
1292 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1297 @subsection What @value{GDBN} Does During Startup
1298 @cindex @value{GDBN} startup
1300 Here's the description of what @value{GDBN} does during session startup:
1304 Sets up the command interpreter as specified by the command line
1305 (@pxref{Mode Options, interpreter}).
1309 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1310 used when building @value{GDBN}; @pxref{System-wide configuration,
1311 ,System-wide configuration and settings}) and executes all the commands in
1314 @anchor{Home Directory Init File}
1316 Reads the init file (if any) in your home directory@footnote{On
1317 DOS/Windows systems, the home directory is the one pointed to by the
1318 @code{HOME} environment variable.} and executes all the commands in
1321 @anchor{Option -init-eval-command}
1323 Executes commands and command files specified by the @samp{-iex} and
1324 @samp{-ix} options in their specified order. Usually you should use the
1325 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1326 settings before @value{GDBN} init files get executed and before inferior
1330 Processes command line options and operands.
1332 @anchor{Init File in the Current Directory during Startup}
1334 Reads and executes the commands from init file (if any) in the current
1335 working directory as long as @samp{set auto-load local-gdbinit} is set to
1336 @samp{on} (@pxref{Init File in the Current Directory}).
1337 This is only done if the current directory is
1338 different from your home directory. Thus, you can have more than one
1339 init file, one generic in your home directory, and another, specific
1340 to the program you are debugging, in the directory where you invoke
1344 If the command line specified a program to debug, or a process to
1345 attach to, or a core file, @value{GDBN} loads any auto-loaded
1346 scripts provided for the program or for its loaded shared libraries.
1347 @xref{Auto-loading}.
1349 If you wish to disable the auto-loading during startup,
1350 you must do something like the following:
1353 $ gdb -iex "set auto-load python-scripts off" myprogram
1356 Option @samp{-ex} does not work because the auto-loading is then turned
1360 Executes commands and command files specified by the @samp{-ex} and
1361 @samp{-x} options in their specified order. @xref{Command Files}, for
1362 more details about @value{GDBN} command files.
1365 Reads the command history recorded in the @dfn{history file}.
1366 @xref{Command History}, for more details about the command history and the
1367 files where @value{GDBN} records it.
1370 Init files use the same syntax as @dfn{command files} (@pxref{Command
1371 Files}) and are processed by @value{GDBN} in the same way. The init
1372 file in your home directory can set options (such as @samp{set
1373 complaints}) that affect subsequent processing of command line options
1374 and operands. Init files are not executed if you use the @samp{-nx}
1375 option (@pxref{Mode Options, ,Choosing Modes}).
1377 To display the list of init files loaded by gdb at startup, you
1378 can use @kbd{gdb --help}.
1380 @cindex init file name
1381 @cindex @file{.gdbinit}
1382 @cindex @file{gdb.ini}
1383 The @value{GDBN} init files are normally called @file{.gdbinit}.
1384 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1385 the limitations of file names imposed by DOS filesystems. The Windows
1386 port of @value{GDBN} uses the standard name, but if it finds a
1387 @file{gdb.ini} file in your home directory, it warns you about that
1388 and suggests to rename the file to the standard name.
1392 @section Quitting @value{GDBN}
1393 @cindex exiting @value{GDBN}
1394 @cindex leaving @value{GDBN}
1397 @kindex quit @r{[}@var{expression}@r{]}
1398 @kindex q @r{(@code{quit})}
1399 @item quit @r{[}@var{expression}@r{]}
1401 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1402 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1403 do not supply @var{expression}, @value{GDBN} will terminate normally;
1404 otherwise it will terminate using the result of @var{expression} as the
1409 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1410 terminates the action of any @value{GDBN} command that is in progress and
1411 returns to @value{GDBN} command level. It is safe to type the interrupt
1412 character at any time because @value{GDBN} does not allow it to take effect
1413 until a time when it is safe.
1415 If you have been using @value{GDBN} to control an attached process or
1416 device, you can release it with the @code{detach} command
1417 (@pxref{Attach, ,Debugging an Already-running Process}).
1419 @node Shell Commands
1420 @section Shell Commands
1422 If you need to execute occasional shell commands during your
1423 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1424 just use the @code{shell} command.
1429 @cindex shell escape
1430 @item shell @var{command-string}
1431 @itemx !@var{command-string}
1432 Invoke a standard shell to execute @var{command-string}.
1433 Note that no space is needed between @code{!} and @var{command-string}.
1434 If it exists, the environment variable @code{SHELL} determines which
1435 shell to run. Otherwise @value{GDBN} uses the default shell
1436 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1439 The utility @code{make} is often needed in development environments.
1440 You do not have to use the @code{shell} command for this purpose in
1445 @cindex calling make
1446 @item make @var{make-args}
1447 Execute the @code{make} program with the specified
1448 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1451 @node Logging Output
1452 @section Logging Output
1453 @cindex logging @value{GDBN} output
1454 @cindex save @value{GDBN} output to a file
1456 You may want to save the output of @value{GDBN} commands to a file.
1457 There are several commands to control @value{GDBN}'s logging.
1461 @item set logging on
1463 @item set logging off
1465 @cindex logging file name
1466 @item set logging file @var{file}
1467 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1468 @item set logging overwrite [on|off]
1469 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1470 you want @code{set logging on} to overwrite the logfile instead.
1471 @item set logging redirect [on|off]
1472 By default, @value{GDBN} output will go to both the terminal and the logfile.
1473 Set @code{redirect} if you want output to go only to the log file.
1474 @kindex show logging
1476 Show the current values of the logging settings.
1480 @chapter @value{GDBN} Commands
1482 You can abbreviate a @value{GDBN} command to the first few letters of the command
1483 name, if that abbreviation is unambiguous; and you can repeat certain
1484 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1485 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1486 show you the alternatives available, if there is more than one possibility).
1489 * Command Syntax:: How to give commands to @value{GDBN}
1490 * Completion:: Command completion
1491 * Help:: How to ask @value{GDBN} for help
1494 @node Command Syntax
1495 @section Command Syntax
1497 A @value{GDBN} command is a single line of input. There is no limit on
1498 how long it can be. It starts with a command name, which is followed by
1499 arguments whose meaning depends on the command name. For example, the
1500 command @code{step} accepts an argument which is the number of times to
1501 step, as in @samp{step 5}. You can also use the @code{step} command
1502 with no arguments. Some commands do not allow any arguments.
1504 @cindex abbreviation
1505 @value{GDBN} command names may always be truncated if that abbreviation is
1506 unambiguous. Other possible command abbreviations are listed in the
1507 documentation for individual commands. In some cases, even ambiguous
1508 abbreviations are allowed; for example, @code{s} is specially defined as
1509 equivalent to @code{step} even though there are other commands whose
1510 names start with @code{s}. You can test abbreviations by using them as
1511 arguments to the @code{help} command.
1513 @cindex repeating commands
1514 @kindex RET @r{(repeat last command)}
1515 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1516 repeat the previous command. Certain commands (for example, @code{run})
1517 will not repeat this way; these are commands whose unintentional
1518 repetition might cause trouble and which you are unlikely to want to
1519 repeat. User-defined commands can disable this feature; see
1520 @ref{Define, dont-repeat}.
1522 The @code{list} and @code{x} commands, when you repeat them with
1523 @key{RET}, construct new arguments rather than repeating
1524 exactly as typed. This permits easy scanning of source or memory.
1526 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1527 output, in a way similar to the common utility @code{more}
1528 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1529 @key{RET} too many in this situation, @value{GDBN} disables command
1530 repetition after any command that generates this sort of display.
1532 @kindex # @r{(a comment)}
1534 Any text from a @kbd{#} to the end of the line is a comment; it does
1535 nothing. This is useful mainly in command files (@pxref{Command
1536 Files,,Command Files}).
1538 @cindex repeating command sequences
1539 @kindex Ctrl-o @r{(operate-and-get-next)}
1540 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1541 commands. This command accepts the current line, like @key{RET}, and
1542 then fetches the next line relative to the current line from the history
1546 @section Command Completion
1549 @cindex word completion
1550 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1551 only one possibility; it can also show you what the valid possibilities
1552 are for the next word in a command, at any time. This works for @value{GDBN}
1553 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1555 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1556 of a word. If there is only one possibility, @value{GDBN} fills in the
1557 word, and waits for you to finish the command (or press @key{RET} to
1558 enter it). For example, if you type
1560 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1561 @c complete accuracy in these examples; space introduced for clarity.
1562 @c If texinfo enhancements make it unnecessary, it would be nice to
1563 @c replace " @key" by "@key" in the following...
1565 (@value{GDBP}) info bre @key{TAB}
1569 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1570 the only @code{info} subcommand beginning with @samp{bre}:
1573 (@value{GDBP}) info breakpoints
1577 You can either press @key{RET} at this point, to run the @code{info
1578 breakpoints} command, or backspace and enter something else, if
1579 @samp{breakpoints} does not look like the command you expected. (If you
1580 were sure you wanted @code{info breakpoints} in the first place, you
1581 might as well just type @key{RET} immediately after @samp{info bre},
1582 to exploit command abbreviations rather than command completion).
1584 If there is more than one possibility for the next word when you press
1585 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1586 characters and try again, or just press @key{TAB} a second time;
1587 @value{GDBN} displays all the possible completions for that word. For
1588 example, you might want to set a breakpoint on a subroutine whose name
1589 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1590 just sounds the bell. Typing @key{TAB} again displays all the
1591 function names in your program that begin with those characters, for
1595 (@value{GDBP}) b make_ @key{TAB}
1596 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1597 make_a_section_from_file make_environ
1598 make_abs_section make_function_type
1599 make_blockvector make_pointer_type
1600 make_cleanup make_reference_type
1601 make_command make_symbol_completion_list
1602 (@value{GDBP}) b make_
1606 After displaying the available possibilities, @value{GDBN} copies your
1607 partial input (@samp{b make_} in the example) so you can finish the
1610 If you just want to see the list of alternatives in the first place, you
1611 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1612 means @kbd{@key{META} ?}. You can type this either by holding down a
1613 key designated as the @key{META} shift on your keyboard (if there is
1614 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1616 If the number of possible completions is large, @value{GDBN} will
1617 print as much of the list as it has collected, as well as a message
1618 indicating that the list may be truncated.
1621 (@value{GDBP}) b m@key{TAB}@key{TAB}
1623 <... the rest of the possible completions ...>
1624 *** List may be truncated, max-completions reached. ***
1629 This behavior can be controlled with the following commands:
1632 @kindex set max-completions
1633 @item set max-completions @var{limit}
1634 @itemx set max-completions unlimited
1635 Set the maximum number of completion candidates. @value{GDBN} will
1636 stop looking for more completions once it collects this many candidates.
1637 This is useful when completing on things like function names as collecting
1638 all the possible candidates can be time consuming.
1639 The default value is 200. A value of zero disables tab-completion.
1640 Note that setting either no limit or a very large limit can make
1642 @kindex show max-completions
1643 @item show max-completions
1644 Show the maximum number of candidates that @value{GDBN} will collect and show
1648 @cindex quotes in commands
1649 @cindex completion of quoted strings
1650 Sometimes the string you need, while logically a ``word'', may contain
1651 parentheses or other characters that @value{GDBN} normally excludes from
1652 its notion of a word. To permit word completion to work in this
1653 situation, you may enclose words in @code{'} (single quote marks) in
1654 @value{GDBN} commands.
1656 A likely situation where you might need this is in typing an
1657 expression that involves a C@t{++} symbol name with template
1658 parameters. This is because when completing expressions, GDB treats
1659 the @samp{<} character as word delimiter, assuming that it's the
1660 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1663 For example, when you want to call a C@t{++} template function
1664 interactively using the @code{print} or @code{call} commands, you may
1665 need to distinguish whether you mean the version of @code{name} that
1666 was specialized for @code{int}, @code{name<int>()}, or the version
1667 that was specialized for @code{float}, @code{name<float>()}. To use
1668 the word-completion facilities in this situation, type a single quote
1669 @code{'} at the beginning of the function name. This alerts
1670 @value{GDBN} that it may need to consider more information than usual
1671 when you press @key{TAB} or @kbd{M-?} to request word completion:
1674 (@value{GDBP}) p 'func< @kbd{M-?}
1675 func<int>() func<float>()
1676 (@value{GDBP}) p 'func<
1679 When setting breakpoints however (@pxref{Specify Location}), you don't
1680 usually need to type a quote before the function name, because
1681 @value{GDBN} understands that you want to set a breakpoint on a
1685 (@value{GDBP}) b func< @kbd{M-?}
1686 func<int>() func<float>()
1687 (@value{GDBP}) b func<
1690 This is true even in the case of typing the name of C@t{++} overloaded
1691 functions (multiple definitions of the same function, distinguished by
1692 argument type). For example, when you want to set a breakpoint you
1693 don't need to distinguish whether you mean the version of @code{name}
1694 that takes an @code{int} parameter, @code{name(int)}, or the version
1695 that takes a @code{float} parameter, @code{name(float)}.
1698 (@value{GDBP}) b bubble( @kbd{M-?}
1699 bubble(int) bubble(double)
1700 (@value{GDBP}) b bubble(dou @kbd{M-?}
1704 See @ref{quoting names} for a description of other scenarios that
1707 For more information about overloaded functions, see @ref{C Plus Plus
1708 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1709 overload-resolution off} to disable overload resolution;
1710 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1712 @cindex completion of structure field names
1713 @cindex structure field name completion
1714 @cindex completion of union field names
1715 @cindex union field name completion
1716 When completing in an expression which looks up a field in a
1717 structure, @value{GDBN} also tries@footnote{The completer can be
1718 confused by certain kinds of invalid expressions. Also, it only
1719 examines the static type of the expression, not the dynamic type.} to
1720 limit completions to the field names available in the type of the
1724 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1725 magic to_fputs to_rewind
1726 to_data to_isatty to_write
1727 to_delete to_put to_write_async_safe
1732 This is because the @code{gdb_stdout} is a variable of the type
1733 @code{struct ui_file} that is defined in @value{GDBN} sources as
1740 ui_file_flush_ftype *to_flush;
1741 ui_file_write_ftype *to_write;
1742 ui_file_write_async_safe_ftype *to_write_async_safe;
1743 ui_file_fputs_ftype *to_fputs;
1744 ui_file_read_ftype *to_read;
1745 ui_file_delete_ftype *to_delete;
1746 ui_file_isatty_ftype *to_isatty;
1747 ui_file_rewind_ftype *to_rewind;
1748 ui_file_put_ftype *to_put;
1755 @section Getting Help
1756 @cindex online documentation
1759 You can always ask @value{GDBN} itself for information on its commands,
1760 using the command @code{help}.
1763 @kindex h @r{(@code{help})}
1766 You can use @code{help} (abbreviated @code{h}) with no arguments to
1767 display a short list of named classes of commands:
1771 List of classes of commands:
1773 aliases -- Aliases of other commands
1774 breakpoints -- Making program stop at certain points
1775 data -- Examining data
1776 files -- Specifying and examining files
1777 internals -- Maintenance commands
1778 obscure -- Obscure features
1779 running -- Running the program
1780 stack -- Examining the stack
1781 status -- Status inquiries
1782 support -- Support facilities
1783 tracepoints -- Tracing of program execution without
1784 stopping the program
1785 user-defined -- User-defined commands
1787 Type "help" followed by a class name for a list of
1788 commands in that class.
1789 Type "help" followed by command name for full
1791 Command name abbreviations are allowed if unambiguous.
1794 @c the above line break eliminates huge line overfull...
1796 @item help @var{class}
1797 Using one of the general help classes as an argument, you can get a
1798 list of the individual commands in that class. For example, here is the
1799 help display for the class @code{status}:
1802 (@value{GDBP}) help status
1807 @c Line break in "show" line falsifies real output, but needed
1808 @c to fit in smallbook page size.
1809 info -- Generic command for showing things
1810 about the program being debugged
1811 show -- Generic command for showing things
1814 Type "help" followed by command name for full
1816 Command name abbreviations are allowed if unambiguous.
1820 @item help @var{command}
1821 With a command name as @code{help} argument, @value{GDBN} displays a
1822 short paragraph on how to use that command.
1825 @item apropos @var{args}
1826 The @code{apropos} command searches through all of the @value{GDBN}
1827 commands, and their documentation, for the regular expression specified in
1828 @var{args}. It prints out all matches found. For example:
1839 alias -- Define a new command that is an alias of an existing command
1840 aliases -- Aliases of other commands
1841 d -- Delete some breakpoints or auto-display expressions
1842 del -- Delete some breakpoints or auto-display expressions
1843 delete -- Delete some breakpoints or auto-display expressions
1848 @item complete @var{args}
1849 The @code{complete @var{args}} command lists all the possible completions
1850 for the beginning of a command. Use @var{args} to specify the beginning of the
1851 command you want completed. For example:
1857 @noindent results in:
1868 @noindent This is intended for use by @sc{gnu} Emacs.
1871 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1872 and @code{show} to inquire about the state of your program, or the state
1873 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1874 manual introduces each of them in the appropriate context. The listings
1875 under @code{info} and under @code{show} in the Command, Variable, and
1876 Function Index point to all the sub-commands. @xref{Command and Variable
1882 @kindex i @r{(@code{info})}
1884 This command (abbreviated @code{i}) is for describing the state of your
1885 program. For example, you can show the arguments passed to a function
1886 with @code{info args}, list the registers currently in use with @code{info
1887 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1888 You can get a complete list of the @code{info} sub-commands with
1889 @w{@code{help info}}.
1893 You can assign the result of an expression to an environment variable with
1894 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1895 @code{set prompt $}.
1899 In contrast to @code{info}, @code{show} is for describing the state of
1900 @value{GDBN} itself.
1901 You can change most of the things you can @code{show}, by using the
1902 related command @code{set}; for example, you can control what number
1903 system is used for displays with @code{set radix}, or simply inquire
1904 which is currently in use with @code{show radix}.
1907 To display all the settable parameters and their current
1908 values, you can use @code{show} with no arguments; you may also use
1909 @code{info set}. Both commands produce the same display.
1910 @c FIXME: "info set" violates the rule that "info" is for state of
1911 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1912 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1916 Here are several miscellaneous @code{show} subcommands, all of which are
1917 exceptional in lacking corresponding @code{set} commands:
1920 @kindex show version
1921 @cindex @value{GDBN} version number
1923 Show what version of @value{GDBN} is running. You should include this
1924 information in @value{GDBN} bug-reports. If multiple versions of
1925 @value{GDBN} are in use at your site, you may need to determine which
1926 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1927 commands are introduced, and old ones may wither away. Also, many
1928 system vendors ship variant versions of @value{GDBN}, and there are
1929 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1930 The version number is the same as the one announced when you start
1933 @kindex show copying
1934 @kindex info copying
1935 @cindex display @value{GDBN} copyright
1938 Display information about permission for copying @value{GDBN}.
1940 @kindex show warranty
1941 @kindex info warranty
1943 @itemx info warranty
1944 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1945 if your version of @value{GDBN} comes with one.
1947 @kindex show configuration
1948 @item show configuration
1949 Display detailed information about the way @value{GDBN} was configured
1950 when it was built. This displays the optional arguments passed to the
1951 @file{configure} script and also configuration parameters detected
1952 automatically by @command{configure}. When reporting a @value{GDBN}
1953 bug (@pxref{GDB Bugs}), it is important to include this information in
1959 @chapter Running Programs Under @value{GDBN}
1961 When you run a program under @value{GDBN}, you must first generate
1962 debugging information when you compile it.
1964 You may start @value{GDBN} with its arguments, if any, in an environment
1965 of your choice. If you are doing native debugging, you may redirect
1966 your program's input and output, debug an already running process, or
1967 kill a child process.
1970 * Compilation:: Compiling for debugging
1971 * Starting:: Starting your program
1972 * Arguments:: Your program's arguments
1973 * Environment:: Your program's environment
1975 * Working Directory:: Your program's working directory
1976 * Input/Output:: Your program's input and output
1977 * Attach:: Debugging an already-running process
1978 * Kill Process:: Killing the child process
1980 * Inferiors and Programs:: Debugging multiple inferiors and programs
1981 * Threads:: Debugging programs with multiple threads
1982 * Forks:: Debugging forks
1983 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1987 @section Compiling for Debugging
1989 In order to debug a program effectively, you need to generate
1990 debugging information when you compile it. This debugging information
1991 is stored in the object file; it describes the data type of each
1992 variable or function and the correspondence between source line numbers
1993 and addresses in the executable code.
1995 To request debugging information, specify the @samp{-g} option when you run
1998 Programs that are to be shipped to your customers are compiled with
1999 optimizations, using the @samp{-O} compiler option. However, some
2000 compilers are unable to handle the @samp{-g} and @samp{-O} options
2001 together. Using those compilers, you cannot generate optimized
2002 executables containing debugging information.
2004 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2005 without @samp{-O}, making it possible to debug optimized code. We
2006 recommend that you @emph{always} use @samp{-g} whenever you compile a
2007 program. You may think your program is correct, but there is no sense
2008 in pushing your luck. For more information, see @ref{Optimized Code}.
2010 Older versions of the @sc{gnu} C compiler permitted a variant option
2011 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2012 format; if your @sc{gnu} C compiler has this option, do not use it.
2014 @value{GDBN} knows about preprocessor macros and can show you their
2015 expansion (@pxref{Macros}). Most compilers do not include information
2016 about preprocessor macros in the debugging information if you specify
2017 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2018 the @sc{gnu} C compiler, provides macro information if you are using
2019 the DWARF debugging format, and specify the option @option{-g3}.
2021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2023 information on @value{NGCC} options affecting debug information.
2025 You will have the best debugging experience if you use the latest
2026 version of the DWARF debugging format that your compiler supports.
2027 DWARF is currently the most expressive and best supported debugging
2028 format in @value{GDBN}.
2032 @section Starting your Program
2038 @kindex r @r{(@code{run})}
2041 Use the @code{run} command to start your program under @value{GDBN}.
2042 You must first specify the program name with an argument to
2043 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2044 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2045 command (@pxref{Files, ,Commands to Specify Files}).
2049 If you are running your program in an execution environment that
2050 supports processes, @code{run} creates an inferior process and makes
2051 that process run your program. In some environments without processes,
2052 @code{run} jumps to the start of your program. Other targets,
2053 like @samp{remote}, are always running. If you get an error
2054 message like this one:
2057 The "remote" target does not support "run".
2058 Try "help target" or "continue".
2062 then use @code{continue} to run your program. You may need @code{load}
2063 first (@pxref{load}).
2065 The execution of a program is affected by certain information it
2066 receives from its superior. @value{GDBN} provides ways to specify this
2067 information, which you must do @emph{before} starting your program. (You
2068 can change it after starting your program, but such changes only affect
2069 your program the next time you start it.) This information may be
2070 divided into four categories:
2073 @item The @emph{arguments.}
2074 Specify the arguments to give your program as the arguments of the
2075 @code{run} command. If a shell is available on your target, the shell
2076 is used to pass the arguments, so that you may use normal conventions
2077 (such as wildcard expansion or variable substitution) in describing
2079 In Unix systems, you can control which shell is used with the
2080 @code{SHELL} environment variable. If you do not define @code{SHELL},
2081 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2082 use of any shell with the @code{set startup-with-shell} command (see
2085 @item The @emph{environment.}
2086 Your program normally inherits its environment from @value{GDBN}, but you can
2087 use the @value{GDBN} commands @code{set environment} and @code{unset
2088 environment} to change parts of the environment that affect
2089 your program. @xref{Environment, ,Your Program's Environment}.
2091 @item The @emph{working directory.}
2092 You can set your program's working directory with the command
2093 @kbd{set cwd}. If you do not set any working directory with this
2094 command, your program will inherit @value{GDBN}'s working directory if
2095 native debugging, or the remote server's working directory if remote
2096 debugging. @xref{Working Directory, ,Your Program's Working
2099 @item The @emph{standard input and output.}
2100 Your program normally uses the same device for standard input and
2101 standard output as @value{GDBN} is using. You can redirect input and output
2102 in the @code{run} command line, or you can use the @code{tty} command to
2103 set a different device for your program.
2104 @xref{Input/Output, ,Your Program's Input and Output}.
2107 @emph{Warning:} While input and output redirection work, you cannot use
2108 pipes to pass the output of the program you are debugging to another
2109 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2113 When you issue the @code{run} command, your program begins to execute
2114 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2115 of how to arrange for your program to stop. Once your program has
2116 stopped, you may call functions in your program, using the @code{print}
2117 or @code{call} commands. @xref{Data, ,Examining Data}.
2119 If the modification time of your symbol file has changed since the last
2120 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2121 table, and reads it again. When it does this, @value{GDBN} tries to retain
2122 your current breakpoints.
2127 @cindex run to main procedure
2128 The name of the main procedure can vary from language to language.
2129 With C or C@t{++}, the main procedure name is always @code{main}, but
2130 other languages such as Ada do not require a specific name for their
2131 main procedure. The debugger provides a convenient way to start the
2132 execution of the program and to stop at the beginning of the main
2133 procedure, depending on the language used.
2135 The @samp{start} command does the equivalent of setting a temporary
2136 breakpoint at the beginning of the main procedure and then invoking
2137 the @samp{run} command.
2139 @cindex elaboration phase
2140 Some programs contain an @dfn{elaboration} phase where some startup code is
2141 executed before the main procedure is called. This depends on the
2142 languages used to write your program. In C@t{++}, for instance,
2143 constructors for static and global objects are executed before
2144 @code{main} is called. It is therefore possible that the debugger stops
2145 before reaching the main procedure. However, the temporary breakpoint
2146 will remain to halt execution.
2148 Specify the arguments to give to your program as arguments to the
2149 @samp{start} command. These arguments will be given verbatim to the
2150 underlying @samp{run} command. Note that the same arguments will be
2151 reused if no argument is provided during subsequent calls to
2152 @samp{start} or @samp{run}.
2154 It is sometimes necessary to debug the program during elaboration. In
2155 these cases, using the @code{start} command would stop the execution
2156 of your program too late, as the program would have already completed
2157 the elaboration phase. Under these circumstances, either insert
2158 breakpoints in your elaboration code before running your program or
2159 use the @code{starti} command.
2163 @cindex run to first instruction
2164 The @samp{starti} command does the equivalent of setting a temporary
2165 breakpoint at the first instruction of a program's execution and then
2166 invoking the @samp{run} command. For programs containing an
2167 elaboration phase, the @code{starti} command will stop execution at
2168 the start of the elaboration phase.
2170 @anchor{set exec-wrapper}
2171 @kindex set exec-wrapper
2172 @item set exec-wrapper @var{wrapper}
2173 @itemx show exec-wrapper
2174 @itemx unset exec-wrapper
2175 When @samp{exec-wrapper} is set, the specified wrapper is used to
2176 launch programs for debugging. @value{GDBN} starts your program
2177 with a shell command of the form @kbd{exec @var{wrapper}
2178 @var{program}}. Quoting is added to @var{program} and its
2179 arguments, but not to @var{wrapper}, so you should add quotes if
2180 appropriate for your shell. The wrapper runs until it executes
2181 your program, and then @value{GDBN} takes control.
2183 You can use any program that eventually calls @code{execve} with
2184 its arguments as a wrapper. Several standard Unix utilities do
2185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2186 with @code{exec "$@@"} will also work.
2188 For example, you can use @code{env} to pass an environment variable to
2189 the debugged program, without setting the variable in your shell's
2193 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2197 This command is available when debugging locally on most targets, excluding
2198 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2200 @kindex set startup-with-shell
2201 @anchor{set startup-with-shell}
2202 @item set startup-with-shell
2203 @itemx set startup-with-shell on
2204 @itemx set startup-with-shell off
2205 @itemx show startup-with-shell
2206 On Unix systems, by default, if a shell is available on your target,
2207 @value{GDBN}) uses it to start your program. Arguments of the
2208 @code{run} command are passed to the shell, which does variable
2209 substitution, expands wildcard characters and performs redirection of
2210 I/O. In some circumstances, it may be useful to disable such use of a
2211 shell, for example, when debugging the shell itself or diagnosing
2212 startup failures such as:
2216 Starting program: ./a.out
2217 During startup program terminated with signal SIGSEGV, Segmentation fault.
2221 which indicates the shell or the wrapper specified with
2222 @samp{exec-wrapper} crashed, not your program. Most often, this is
2223 caused by something odd in your shell's non-interactive mode
2224 initialization file---such as @file{.cshrc} for C-shell,
2225 $@file{.zshenv} for the Z shell, or the file specified in the
2226 @samp{BASH_ENV} environment variable for BASH.
2228 @anchor{set auto-connect-native-target}
2229 @kindex set auto-connect-native-target
2230 @item set auto-connect-native-target
2231 @itemx set auto-connect-native-target on
2232 @itemx set auto-connect-native-target off
2233 @itemx show auto-connect-native-target
2235 By default, if not connected to any target yet (e.g., with
2236 @code{target remote}), the @code{run} command starts your program as a
2237 native process under @value{GDBN}, on your local machine. If you're
2238 sure you don't want to debug programs on your local machine, you can
2239 tell @value{GDBN} to not connect to the native target automatically
2240 with the @code{set auto-connect-native-target off} command.
2242 If @code{on}, which is the default, and if @value{GDBN} is not
2243 connected to a target already, the @code{run} command automaticaly
2244 connects to the native target, if one is available.
2246 If @code{off}, and if @value{GDBN} is not connected to a target
2247 already, the @code{run} command fails with an error:
2251 Don't know how to run. Try "help target".
2254 If @value{GDBN} is already connected to a target, @value{GDBN} always
2255 uses it with the @code{run} command.
2257 In any case, you can explicitly connect to the native target with the
2258 @code{target native} command. For example,
2261 (@value{GDBP}) set auto-connect-native-target off
2263 Don't know how to run. Try "help target".
2264 (@value{GDBP}) target native
2266 Starting program: ./a.out
2267 [Inferior 1 (process 10421) exited normally]
2270 In case you connected explicitly to the @code{native} target,
2271 @value{GDBN} remains connected even if all inferiors exit, ready for
2272 the next @code{run} command. Use the @code{disconnect} command to
2275 Examples of other commands that likewise respect the
2276 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2277 proc}, @code{info os}.
2279 @kindex set disable-randomization
2280 @item set disable-randomization
2281 @itemx set disable-randomization on
2282 This option (enabled by default in @value{GDBN}) will turn off the native
2283 randomization of the virtual address space of the started program. This option
2284 is useful for multiple debugging sessions to make the execution better
2285 reproducible and memory addresses reusable across debugging sessions.
2287 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2288 On @sc{gnu}/Linux you can get the same behavior using
2291 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2294 @item set disable-randomization off
2295 Leave the behavior of the started executable unchanged. Some bugs rear their
2296 ugly heads only when the program is loaded at certain addresses. If your bug
2297 disappears when you run the program under @value{GDBN}, that might be because
2298 @value{GDBN} by default disables the address randomization on platforms, such
2299 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2300 disable-randomization off} to try to reproduce such elusive bugs.
2302 On targets where it is available, virtual address space randomization
2303 protects the programs against certain kinds of security attacks. In these
2304 cases the attacker needs to know the exact location of a concrete executable
2305 code. Randomizing its location makes it impossible to inject jumps misusing
2306 a code at its expected addresses.
2308 Prelinking shared libraries provides a startup performance advantage but it
2309 makes addresses in these libraries predictable for privileged processes by
2310 having just unprivileged access at the target system. Reading the shared
2311 library binary gives enough information for assembling the malicious code
2312 misusing it. Still even a prelinked shared library can get loaded at a new
2313 random address just requiring the regular relocation process during the
2314 startup. Shared libraries not already prelinked are always loaded at
2315 a randomly chosen address.
2317 Position independent executables (PIE) contain position independent code
2318 similar to the shared libraries and therefore such executables get loaded at
2319 a randomly chosen address upon startup. PIE executables always load even
2320 already prelinked shared libraries at a random address. You can build such
2321 executable using @command{gcc -fPIE -pie}.
2323 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2324 (as long as the randomization is enabled).
2326 @item show disable-randomization
2327 Show the current setting of the explicit disable of the native randomization of
2328 the virtual address space of the started program.
2333 @section Your Program's Arguments
2335 @cindex arguments (to your program)
2336 The arguments to your program can be specified by the arguments of the
2338 They are passed to a shell, which expands wildcard characters and
2339 performs redirection of I/O, and thence to your program. Your
2340 @code{SHELL} environment variable (if it exists) specifies what shell
2341 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2342 the default shell (@file{/bin/sh} on Unix).
2344 On non-Unix systems, the program is usually invoked directly by
2345 @value{GDBN}, which emulates I/O redirection via the appropriate system
2346 calls, and the wildcard characters are expanded by the startup code of
2347 the program, not by the shell.
2349 @code{run} with no arguments uses the same arguments used by the previous
2350 @code{run}, or those set by the @code{set args} command.
2355 Specify the arguments to be used the next time your program is run. If
2356 @code{set args} has no arguments, @code{run} executes your program
2357 with no arguments. Once you have run your program with arguments,
2358 using @code{set args} before the next @code{run} is the only way to run
2359 it again without arguments.
2363 Show the arguments to give your program when it is started.
2367 @section Your Program's Environment
2369 @cindex environment (of your program)
2370 The @dfn{environment} consists of a set of environment variables and
2371 their values. Environment variables conventionally record such things as
2372 your user name, your home directory, your terminal type, and your search
2373 path for programs to run. Usually you set up environment variables with
2374 the shell and they are inherited by all the other programs you run. When
2375 debugging, it can be useful to try running your program with a modified
2376 environment without having to start @value{GDBN} over again.
2380 @item path @var{directory}
2381 Add @var{directory} to the front of the @code{PATH} environment variable
2382 (the search path for executables) that will be passed to your program.
2383 The value of @code{PATH} used by @value{GDBN} does not change.
2384 You may specify several directory names, separated by whitespace or by a
2385 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2386 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2387 is moved to the front, so it is searched sooner.
2389 You can use the string @samp{$cwd} to refer to whatever is the current
2390 working directory at the time @value{GDBN} searches the path. If you
2391 use @samp{.} instead, it refers to the directory where you executed the
2392 @code{path} command. @value{GDBN} replaces @samp{.} in the
2393 @var{directory} argument (with the current path) before adding
2394 @var{directory} to the search path.
2395 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2396 @c document that, since repeating it would be a no-op.
2400 Display the list of search paths for executables (the @code{PATH}
2401 environment variable).
2403 @kindex show environment
2404 @item show environment @r{[}@var{varname}@r{]}
2405 Print the value of environment variable @var{varname} to be given to
2406 your program when it starts. If you do not supply @var{varname},
2407 print the names and values of all environment variables to be given to
2408 your program. You can abbreviate @code{environment} as @code{env}.
2410 @kindex set environment
2411 @anchor{set environment}
2412 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2413 Set environment variable @var{varname} to @var{value}. The value
2414 changes for your program (and the shell @value{GDBN} uses to launch
2415 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2416 values of environment variables are just strings, and any
2417 interpretation is supplied by your program itself. The @var{value}
2418 parameter is optional; if it is eliminated, the variable is set to a
2420 @c "any string" here does not include leading, trailing
2421 @c blanks. Gnu asks: does anyone care?
2423 For example, this command:
2430 tells the debugged program, when subsequently run, that its user is named
2431 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2432 are not actually required.)
2434 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2435 which also inherits the environment set with @code{set environment}.
2436 If necessary, you can avoid that by using the @samp{env} program as a
2437 wrapper instead of using @code{set environment}. @xref{set
2438 exec-wrapper}, for an example doing just that.
2440 Environment variables that are set by the user are also transmitted to
2441 @command{gdbserver} to be used when starting the remote inferior.
2442 @pxref{QEnvironmentHexEncoded}.
2444 @kindex unset environment
2445 @anchor{unset environment}
2446 @item unset environment @var{varname}
2447 Remove variable @var{varname} from the environment to be passed to your
2448 program. This is different from @samp{set env @var{varname} =};
2449 @code{unset environment} removes the variable from the environment,
2450 rather than assigning it an empty value.
2452 Environment variables that are unset by the user are also unset on
2453 @command{gdbserver} when starting the remote inferior.
2454 @pxref{QEnvironmentUnset}.
2457 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2458 the shell indicated by your @code{SHELL} environment variable if it
2459 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2460 names a shell that runs an initialization file when started
2461 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2462 for the Z shell, or the file specified in the @samp{BASH_ENV}
2463 environment variable for BASH---any variables you set in that file
2464 affect your program. You may wish to move setting of environment
2465 variables to files that are only run when you sign on, such as
2466 @file{.login} or @file{.profile}.
2468 @node Working Directory
2469 @section Your Program's Working Directory
2471 @cindex working directory (of your program)
2472 Each time you start your program with @code{run}, the inferior will be
2473 initialized with the current working directory specified by the
2474 @kbd{set cwd} command. If no directory has been specified by this
2475 command, then the inferior will inherit @value{GDBN}'s current working
2476 directory as its working directory if native debugging, or it will
2477 inherit the remote server's current working directory if remote
2482 @cindex change inferior's working directory
2483 @anchor{set cwd command}
2484 @item set cwd @r{[}@var{directory}@r{]}
2485 Set the inferior's working directory to @var{directory}, which will be
2486 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2487 argument has been specified, the command clears the setting and resets
2488 it to an empty state. This setting has no effect on @value{GDBN}'s
2489 working directory, and it only takes effect the next time you start
2490 the inferior. The @file{~} in @var{directory} is a short for the
2491 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2492 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2493 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2496 You can also change @value{GDBN}'s current working directory by using
2497 the @code{cd} command.
2501 @cindex show inferior's working directory
2503 Show the inferior's working directory. If no directory has been
2504 specified by @kbd{set cwd}, then the default inferior's working
2505 directory is the same as @value{GDBN}'s working directory.
2508 @cindex change @value{GDBN}'s working directory
2510 @item cd @r{[}@var{directory}@r{]}
2511 Set the @value{GDBN} working directory to @var{directory}. If not
2512 given, @var{directory} uses @file{'~'}.
2514 The @value{GDBN} working directory serves as a default for the
2515 commands that specify files for @value{GDBN} to operate on.
2516 @xref{Files, ,Commands to Specify Files}.
2517 @xref{set cwd command}
2521 Print the @value{GDBN} working directory.
2524 It is generally impossible to find the current working directory of
2525 the process being debugged (since a program can change its directory
2526 during its run). If you work on a system where @value{GDBN} is
2527 configured with the @file{/proc} support, you can use the @code{info
2528 proc} command (@pxref{SVR4 Process Information}) to find out the
2529 current working directory of the debuggee.
2532 @section Your Program's Input and Output
2537 By default, the program you run under @value{GDBN} does input and output to
2538 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2539 to its own terminal modes to interact with you, but it records the terminal
2540 modes your program was using and switches back to them when you continue
2541 running your program.
2544 @kindex info terminal
2546 Displays information recorded by @value{GDBN} about the terminal modes your
2550 You can redirect your program's input and/or output using shell
2551 redirection with the @code{run} command. For example,
2558 starts your program, diverting its output to the file @file{outfile}.
2561 @cindex controlling terminal
2562 Another way to specify where your program should do input and output is
2563 with the @code{tty} command. This command accepts a file name as
2564 argument, and causes this file to be the default for future @code{run}
2565 commands. It also resets the controlling terminal for the child
2566 process, for future @code{run} commands. For example,
2573 directs that processes started with subsequent @code{run} commands
2574 default to do input and output on the terminal @file{/dev/ttyb} and have
2575 that as their controlling terminal.
2577 An explicit redirection in @code{run} overrides the @code{tty} command's
2578 effect on the input/output device, but not its effect on the controlling
2581 When you use the @code{tty} command or redirect input in the @code{run}
2582 command, only the input @emph{for your program} is affected. The input
2583 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2584 for @code{set inferior-tty}.
2586 @cindex inferior tty
2587 @cindex set inferior controlling terminal
2588 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2589 display the name of the terminal that will be used for future runs of your
2593 @item set inferior-tty [ @var{tty} ]
2594 @kindex set inferior-tty
2595 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2596 restores the default behavior, which is to use the same terminal as
2599 @item show inferior-tty
2600 @kindex show inferior-tty
2601 Show the current tty for the program being debugged.
2605 @section Debugging an Already-running Process
2610 @item attach @var{process-id}
2611 This command attaches to a running process---one that was started
2612 outside @value{GDBN}. (@code{info files} shows your active
2613 targets.) The command takes as argument a process ID. The usual way to
2614 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2615 or with the @samp{jobs -l} shell command.
2617 @code{attach} does not repeat if you press @key{RET} a second time after
2618 executing the command.
2621 To use @code{attach}, your program must be running in an environment
2622 which supports processes; for example, @code{attach} does not work for
2623 programs on bare-board targets that lack an operating system. You must
2624 also have permission to send the process a signal.
2626 When you use @code{attach}, the debugger finds the program running in
2627 the process first by looking in the current working directory, then (if
2628 the program is not found) by using the source file search path
2629 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2630 the @code{file} command to load the program. @xref{Files, ,Commands to
2633 The first thing @value{GDBN} does after arranging to debug the specified
2634 process is to stop it. You can examine and modify an attached process
2635 with all the @value{GDBN} commands that are ordinarily available when
2636 you start processes with @code{run}. You can insert breakpoints; you
2637 can step and continue; you can modify storage. If you would rather the
2638 process continue running, you may use the @code{continue} command after
2639 attaching @value{GDBN} to the process.
2644 When you have finished debugging the attached process, you can use the
2645 @code{detach} command to release it from @value{GDBN} control. Detaching
2646 the process continues its execution. After the @code{detach} command,
2647 that process and @value{GDBN} become completely independent once more, and you
2648 are ready to @code{attach} another process or start one with @code{run}.
2649 @code{detach} does not repeat if you press @key{RET} again after
2650 executing the command.
2653 If you exit @value{GDBN} while you have an attached process, you detach
2654 that process. If you use the @code{run} command, you kill that process.
2655 By default, @value{GDBN} asks for confirmation if you try to do either of these
2656 things; you can control whether or not you need to confirm by using the
2657 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2661 @section Killing the Child Process
2666 Kill the child process in which your program is running under @value{GDBN}.
2669 This command is useful if you wish to debug a core dump instead of a
2670 running process. @value{GDBN} ignores any core dump file while your program
2673 On some operating systems, a program cannot be executed outside @value{GDBN}
2674 while you have breakpoints set on it inside @value{GDBN}. You can use the
2675 @code{kill} command in this situation to permit running your program
2676 outside the debugger.
2678 The @code{kill} command is also useful if you wish to recompile and
2679 relink your program, since on many systems it is impossible to modify an
2680 executable file while it is running in a process. In this case, when you
2681 next type @code{run}, @value{GDBN} notices that the file has changed, and
2682 reads the symbol table again (while trying to preserve your current
2683 breakpoint settings).
2685 @node Inferiors and Programs
2686 @section Debugging Multiple Inferiors and Programs
2688 @value{GDBN} lets you run and debug multiple programs in a single
2689 session. In addition, @value{GDBN} on some systems may let you run
2690 several programs simultaneously (otherwise you have to exit from one
2691 before starting another). In the most general case, you can have
2692 multiple threads of execution in each of multiple processes, launched
2693 from multiple executables.
2696 @value{GDBN} represents the state of each program execution with an
2697 object called an @dfn{inferior}. An inferior typically corresponds to
2698 a process, but is more general and applies also to targets that do not
2699 have processes. Inferiors may be created before a process runs, and
2700 may be retained after a process exits. Inferiors have unique
2701 identifiers that are different from process ids. Usually each
2702 inferior will also have its own distinct address space, although some
2703 embedded targets may have several inferiors running in different parts
2704 of a single address space. Each inferior may in turn have multiple
2705 threads running in it.
2707 To find out what inferiors exist at any moment, use @w{@code{info
2711 @kindex info inferiors
2712 @item info inferiors
2713 Print a list of all inferiors currently being managed by @value{GDBN}.
2715 @value{GDBN} displays for each inferior (in this order):
2719 the inferior number assigned by @value{GDBN}
2722 the target system's inferior identifier
2725 the name of the executable the inferior is running.
2730 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2731 indicates the current inferior.
2735 @c end table here to get a little more width for example
2738 (@value{GDBP}) info inferiors
2739 Num Description Executable
2740 2 process 2307 hello
2741 * 1 process 3401 goodbye
2744 To switch focus between inferiors, use the @code{inferior} command:
2747 @kindex inferior @var{infno}
2748 @item inferior @var{infno}
2749 Make inferior number @var{infno} the current inferior. The argument
2750 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2751 in the first field of the @samp{info inferiors} display.
2754 @vindex $_inferior@r{, convenience variable}
2755 The debugger convenience variable @samp{$_inferior} contains the
2756 number of the current inferior. You may find this useful in writing
2757 breakpoint conditional expressions, command scripts, and so forth.
2758 @xref{Convenience Vars,, Convenience Variables}, for general
2759 information on convenience variables.
2761 You can get multiple executables into a debugging session via the
2762 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2763 systems @value{GDBN} can add inferiors to the debug session
2764 automatically by following calls to @code{fork} and @code{exec}. To
2765 remove inferiors from the debugging session use the
2766 @w{@code{remove-inferiors}} command.
2769 @kindex add-inferior
2770 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2771 Adds @var{n} inferiors to be run using @var{executable} as the
2772 executable; @var{n} defaults to 1. If no executable is specified,
2773 the inferiors begins empty, with no program. You can still assign or
2774 change the program assigned to the inferior at any time by using the
2775 @code{file} command with the executable name as its argument.
2777 @kindex clone-inferior
2778 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2779 Adds @var{n} inferiors ready to execute the same program as inferior
2780 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2781 number of the current inferior. This is a convenient command when you
2782 want to run another instance of the inferior you are debugging.
2785 (@value{GDBP}) info inferiors
2786 Num Description Executable
2787 * 1 process 29964 helloworld
2788 (@value{GDBP}) clone-inferior
2791 (@value{GDBP}) info inferiors
2792 Num Description Executable
2794 * 1 process 29964 helloworld
2797 You can now simply switch focus to inferior 2 and run it.
2799 @kindex remove-inferiors
2800 @item remove-inferiors @var{infno}@dots{}
2801 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2802 possible to remove an inferior that is running with this command. For
2803 those, use the @code{kill} or @code{detach} command first.
2807 To quit debugging one of the running inferiors that is not the current
2808 inferior, you can either detach from it by using the @w{@code{detach
2809 inferior}} command (allowing it to run independently), or kill it
2810 using the @w{@code{kill inferiors}} command:
2813 @kindex detach inferiors @var{infno}@dots{}
2814 @item detach inferior @var{infno}@dots{}
2815 Detach from the inferior or inferiors identified by @value{GDBN}
2816 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2817 still stays on the list of inferiors shown by @code{info inferiors},
2818 but its Description will show @samp{<null>}.
2820 @kindex kill inferiors @var{infno}@dots{}
2821 @item kill inferiors @var{infno}@dots{}
2822 Kill the inferior or inferiors identified by @value{GDBN} inferior
2823 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2824 stays on the list of inferiors shown by @code{info inferiors}, but its
2825 Description will show @samp{<null>}.
2828 After the successful completion of a command such as @code{detach},
2829 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2830 a normal process exit, the inferior is still valid and listed with
2831 @code{info inferiors}, ready to be restarted.
2834 To be notified when inferiors are started or exit under @value{GDBN}'s
2835 control use @w{@code{set print inferior-events}}:
2838 @kindex set print inferior-events
2839 @cindex print messages on inferior start and exit
2840 @item set print inferior-events
2841 @itemx set print inferior-events on
2842 @itemx set print inferior-events off
2843 The @code{set print inferior-events} command allows you to enable or
2844 disable printing of messages when @value{GDBN} notices that new
2845 inferiors have started or that inferiors have exited or have been
2846 detached. By default, these messages will not be printed.
2848 @kindex show print inferior-events
2849 @item show print inferior-events
2850 Show whether messages will be printed when @value{GDBN} detects that
2851 inferiors have started, exited or have been detached.
2854 Many commands will work the same with multiple programs as with a
2855 single program: e.g., @code{print myglobal} will simply display the
2856 value of @code{myglobal} in the current inferior.
2859 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2860 get more info about the relationship of inferiors, programs, address
2861 spaces in a debug session. You can do that with the @w{@code{maint
2862 info program-spaces}} command.
2865 @kindex maint info program-spaces
2866 @item maint info program-spaces
2867 Print a list of all program spaces currently being managed by
2870 @value{GDBN} displays for each program space (in this order):
2874 the program space number assigned by @value{GDBN}
2877 the name of the executable loaded into the program space, with e.g.,
2878 the @code{file} command.
2883 An asterisk @samp{*} preceding the @value{GDBN} program space number
2884 indicates the current program space.
2886 In addition, below each program space line, @value{GDBN} prints extra
2887 information that isn't suitable to display in tabular form. For
2888 example, the list of inferiors bound to the program space.
2891 (@value{GDBP}) maint info program-spaces
2895 Bound inferiors: ID 1 (process 21561)
2898 Here we can see that no inferior is running the program @code{hello},
2899 while @code{process 21561} is running the program @code{goodbye}. On
2900 some targets, it is possible that multiple inferiors are bound to the
2901 same program space. The most common example is that of debugging both
2902 the parent and child processes of a @code{vfork} call. For example,
2905 (@value{GDBP}) maint info program-spaces
2908 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2911 Here, both inferior 2 and inferior 1 are running in the same program
2912 space as a result of inferior 1 having executed a @code{vfork} call.
2916 @section Debugging Programs with Multiple Threads
2918 @cindex threads of execution
2919 @cindex multiple threads
2920 @cindex switching threads
2921 In some operating systems, such as GNU/Linux and Solaris, a single program
2922 may have more than one @dfn{thread} of execution. The precise semantics
2923 of threads differ from one operating system to another, but in general
2924 the threads of a single program are akin to multiple processes---except
2925 that they share one address space (that is, they can all examine and
2926 modify the same variables). On the other hand, each thread has its own
2927 registers and execution stack, and perhaps private memory.
2929 @value{GDBN} provides these facilities for debugging multi-thread
2933 @item automatic notification of new threads
2934 @item @samp{thread @var{thread-id}}, a command to switch among threads
2935 @item @samp{info threads}, a command to inquire about existing threads
2936 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2937 a command to apply a command to a list of threads
2938 @item thread-specific breakpoints
2939 @item @samp{set print thread-events}, which controls printing of
2940 messages on thread start and exit.
2941 @item @samp{set libthread-db-search-path @var{path}}, which lets
2942 the user specify which @code{libthread_db} to use if the default choice
2943 isn't compatible with the program.
2946 @cindex focus of debugging
2947 @cindex current thread
2948 The @value{GDBN} thread debugging facility allows you to observe all
2949 threads while your program runs---but whenever @value{GDBN} takes
2950 control, one thread in particular is always the focus of debugging.
2951 This thread is called the @dfn{current thread}. Debugging commands show
2952 program information from the perspective of the current thread.
2954 @cindex @code{New} @var{systag} message
2955 @cindex thread identifier (system)
2956 @c FIXME-implementors!! It would be more helpful if the [New...] message
2957 @c included GDB's numeric thread handle, so you could just go to that
2958 @c thread without first checking `info threads'.
2959 Whenever @value{GDBN} detects a new thread in your program, it displays
2960 the target system's identification for the thread with a message in the
2961 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2962 whose form varies depending on the particular system. For example, on
2963 @sc{gnu}/Linux, you might see
2966 [New Thread 0x41e02940 (LWP 25582)]
2970 when @value{GDBN} notices a new thread. In contrast, on other systems,
2971 the @var{systag} is simply something like @samp{process 368}, with no
2974 @c FIXME!! (1) Does the [New...] message appear even for the very first
2975 @c thread of a program, or does it only appear for the
2976 @c second---i.e.@: when it becomes obvious we have a multithread
2978 @c (2) *Is* there necessarily a first thread always? Or do some
2979 @c multithread systems permit starting a program with multiple
2980 @c threads ab initio?
2982 @anchor{thread numbers}
2983 @cindex thread number, per inferior
2984 @cindex thread identifier (GDB)
2985 For debugging purposes, @value{GDBN} associates its own thread number
2986 ---always a single integer---with each thread of an inferior. This
2987 number is unique between all threads of an inferior, but not unique
2988 between threads of different inferiors.
2990 @cindex qualified thread ID
2991 You can refer to a given thread in an inferior using the qualified
2992 @var{inferior-num}.@var{thread-num} syntax, also known as
2993 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2994 number and @var{thread-num} being the thread number of the given
2995 inferior. For example, thread @code{2.3} refers to thread number 3 of
2996 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2997 then @value{GDBN} infers you're referring to a thread of the current
3000 Until you create a second inferior, @value{GDBN} does not show the
3001 @var{inferior-num} part of thread IDs, even though you can always use
3002 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3003 of inferior 1, the initial inferior.
3005 @anchor{thread ID lists}
3006 @cindex thread ID lists
3007 Some commands accept a space-separated @dfn{thread ID list} as
3008 argument. A list element can be:
3012 A thread ID as shown in the first field of the @samp{info threads}
3013 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3017 A range of thread numbers, again with or without an inferior
3018 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3019 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3022 All threads of an inferior, specified with a star wildcard, with or
3023 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3024 @samp{1.*}) or @code{*}. The former refers to all threads of the
3025 given inferior, and the latter form without an inferior qualifier
3026 refers to all threads of the current inferior.
3030 For example, if the current inferior is 1, and inferior 7 has one
3031 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3032 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3033 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3034 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3038 @anchor{global thread numbers}
3039 @cindex global thread number
3040 @cindex global thread identifier (GDB)
3041 In addition to a @emph{per-inferior} number, each thread is also
3042 assigned a unique @emph{global} number, also known as @dfn{global
3043 thread ID}, a single integer. Unlike the thread number component of
3044 the thread ID, no two threads have the same global ID, even when
3045 you're debugging multiple inferiors.
3047 From @value{GDBN}'s perspective, a process always has at least one
3048 thread. In other words, @value{GDBN} assigns a thread number to the
3049 program's ``main thread'' even if the program is not multi-threaded.
3051 @vindex $_thread@r{, convenience variable}
3052 @vindex $_gthread@r{, convenience variable}
3053 The debugger convenience variables @samp{$_thread} and
3054 @samp{$_gthread} contain, respectively, the per-inferior thread number
3055 and the global thread number of the current thread. You may find this
3056 useful in writing breakpoint conditional expressions, command scripts,
3057 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3058 general information on convenience variables.
3060 If @value{GDBN} detects the program is multi-threaded, it augments the
3061 usual message about stopping at a breakpoint with the ID and name of
3062 the thread that hit the breakpoint.
3065 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3068 Likewise when the program receives a signal:
3071 Thread 1 "main" received signal SIGINT, Interrupt.
3075 @kindex info threads
3076 @item info threads @r{[}@var{thread-id-list}@r{]}
3078 Display information about one or more threads. With no arguments
3079 displays information about all threads. You can specify the list of
3080 threads that you want to display using the thread ID list syntax
3081 (@pxref{thread ID lists}).
3083 @value{GDBN} displays for each thread (in this order):
3087 the per-inferior thread number assigned by @value{GDBN}
3090 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3091 option was specified
3094 the target system's thread identifier (@var{systag})
3097 the thread's name, if one is known. A thread can either be named by
3098 the user (see @code{thread name}, below), or, in some cases, by the
3102 the current stack frame summary for that thread
3106 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3107 indicates the current thread.
3111 @c end table here to get a little more width for example
3114 (@value{GDBP}) info threads
3116 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3117 2 process 35 thread 23 0x34e5 in sigpause ()
3118 3 process 35 thread 27 0x34e5 in sigpause ()
3122 If you're debugging multiple inferiors, @value{GDBN} displays thread
3123 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3124 Otherwise, only @var{thread-num} is shown.
3126 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3127 indicating each thread's global thread ID:
3130 (@value{GDBP}) info threads
3131 Id GId Target Id Frame
3132 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3133 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3134 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3135 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3138 On Solaris, you can display more information about user threads with a
3139 Solaris-specific command:
3142 @item maint info sol-threads
3143 @kindex maint info sol-threads
3144 @cindex thread info (Solaris)
3145 Display info on Solaris user threads.
3149 @kindex thread @var{thread-id}
3150 @item thread @var{thread-id}
3151 Make thread ID @var{thread-id} the current thread. The command
3152 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3153 the first field of the @samp{info threads} display, with or without an
3154 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3156 @value{GDBN} responds by displaying the system identifier of the
3157 thread you selected, and its current stack frame summary:
3160 (@value{GDBP}) thread 2
3161 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3162 #0 some_function (ignore=0x0) at example.c:8
3163 8 printf ("hello\n");
3167 As with the @samp{[New @dots{}]} message, the form of the text after
3168 @samp{Switching to} depends on your system's conventions for identifying
3171 @kindex thread apply
3172 @cindex apply command to several threads
3173 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3174 The @code{thread apply} command allows you to apply the named
3175 @var{command} to one or more threads. Specify the threads that you
3176 want affected using the thread ID list syntax (@pxref{thread ID
3177 lists}), or specify @code{all} to apply to all threads. To apply a
3178 command to all threads in descending order, type @kbd{thread apply all
3179 @var{command}}. To apply a command to all threads in ascending order,
3180 type @kbd{thread apply all -ascending @var{command}}.
3184 @cindex name a thread
3185 @item thread name [@var{name}]
3186 This command assigns a name to the current thread. If no argument is
3187 given, any existing user-specified name is removed. The thread name
3188 appears in the @samp{info threads} display.
3190 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3191 determine the name of the thread as given by the OS. On these
3192 systems, a name specified with @samp{thread name} will override the
3193 system-give name, and removing the user-specified name will cause
3194 @value{GDBN} to once again display the system-specified name.
3197 @cindex search for a thread
3198 @item thread find [@var{regexp}]
3199 Search for and display thread ids whose name or @var{systag}
3200 matches the supplied regular expression.
3202 As well as being the complement to the @samp{thread name} command,
3203 this command also allows you to identify a thread by its target
3204 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3208 (@value{GDBN}) thread find 26688
3209 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3210 (@value{GDBN}) info thread 4
3212 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3215 @kindex set print thread-events
3216 @cindex print messages on thread start and exit
3217 @item set print thread-events
3218 @itemx set print thread-events on
3219 @itemx set print thread-events off
3220 The @code{set print thread-events} command allows you to enable or
3221 disable printing of messages when @value{GDBN} notices that new threads have
3222 started or that threads have exited. By default, these messages will
3223 be printed if detection of these events is supported by the target.
3224 Note that these messages cannot be disabled on all targets.
3226 @kindex show print thread-events
3227 @item show print thread-events
3228 Show whether messages will be printed when @value{GDBN} detects that threads
3229 have started and exited.
3232 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3233 more information about how @value{GDBN} behaves when you stop and start
3234 programs with multiple threads.
3236 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3237 watchpoints in programs with multiple threads.
3239 @anchor{set libthread-db-search-path}
3241 @kindex set libthread-db-search-path
3242 @cindex search path for @code{libthread_db}
3243 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3244 If this variable is set, @var{path} is a colon-separated list of
3245 directories @value{GDBN} will use to search for @code{libthread_db}.
3246 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3247 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3248 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3251 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3252 @code{libthread_db} library to obtain information about threads in the
3253 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3254 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3255 specific thread debugging library loading is enabled
3256 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3258 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3259 refers to the default system directories that are
3260 normally searched for loading shared libraries. The @samp{$sdir} entry
3261 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3262 (@pxref{libthread_db.so.1 file}).
3264 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3265 refers to the directory from which @code{libpthread}
3266 was loaded in the inferior process.
3268 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3269 @value{GDBN} attempts to initialize it with the current inferior process.
3270 If this initialization fails (which could happen because of a version
3271 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3272 will unload @code{libthread_db}, and continue with the next directory.
3273 If none of @code{libthread_db} libraries initialize successfully,
3274 @value{GDBN} will issue a warning and thread debugging will be disabled.
3276 Setting @code{libthread-db-search-path} is currently implemented
3277 only on some platforms.
3279 @kindex show libthread-db-search-path
3280 @item show libthread-db-search-path
3281 Display current libthread_db search path.
3283 @kindex set debug libthread-db
3284 @kindex show debug libthread-db
3285 @cindex debugging @code{libthread_db}
3286 @item set debug libthread-db
3287 @itemx show debug libthread-db
3288 Turns on or off display of @code{libthread_db}-related events.
3289 Use @code{1} to enable, @code{0} to disable.
3293 @section Debugging Forks
3295 @cindex fork, debugging programs which call
3296 @cindex multiple processes
3297 @cindex processes, multiple
3298 On most systems, @value{GDBN} has no special support for debugging
3299 programs which create additional processes using the @code{fork}
3300 function. When a program forks, @value{GDBN} will continue to debug the
3301 parent process and the child process will run unimpeded. If you have
3302 set a breakpoint in any code which the child then executes, the child
3303 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3304 will cause it to terminate.
3306 However, if you want to debug the child process there is a workaround
3307 which isn't too painful. Put a call to @code{sleep} in the code which
3308 the child process executes after the fork. It may be useful to sleep
3309 only if a certain environment variable is set, or a certain file exists,
3310 so that the delay need not occur when you don't want to run @value{GDBN}
3311 on the child. While the child is sleeping, use the @code{ps} program to
3312 get its process ID. Then tell @value{GDBN} (a new invocation of
3313 @value{GDBN} if you are also debugging the parent process) to attach to
3314 the child process (@pxref{Attach}). From that point on you can debug
3315 the child process just like any other process which you attached to.
3317 On some systems, @value{GDBN} provides support for debugging programs
3318 that create additional processes using the @code{fork} or @code{vfork}
3319 functions. On @sc{gnu}/Linux platforms, this feature is supported
3320 with kernel version 2.5.46 and later.
3322 The fork debugging commands are supported in native mode and when
3323 connected to @code{gdbserver} in either @code{target remote} mode or
3324 @code{target extended-remote} mode.
3326 By default, when a program forks, @value{GDBN} will continue to debug
3327 the parent process and the child process will run unimpeded.
3329 If you want to follow the child process instead of the parent process,
3330 use the command @w{@code{set follow-fork-mode}}.
3333 @kindex set follow-fork-mode
3334 @item set follow-fork-mode @var{mode}
3335 Set the debugger response to a program call of @code{fork} or
3336 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3337 process. The @var{mode} argument can be:
3341 The original process is debugged after a fork. The child process runs
3342 unimpeded. This is the default.
3345 The new process is debugged after a fork. The parent process runs
3350 @kindex show follow-fork-mode
3351 @item show follow-fork-mode
3352 Display the current debugger response to a @code{fork} or @code{vfork} call.
3355 @cindex debugging multiple processes
3356 On Linux, if you want to debug both the parent and child processes, use the
3357 command @w{@code{set detach-on-fork}}.
3360 @kindex set detach-on-fork
3361 @item set detach-on-fork @var{mode}
3362 Tells gdb whether to detach one of the processes after a fork, or
3363 retain debugger control over them both.
3367 The child process (or parent process, depending on the value of
3368 @code{follow-fork-mode}) will be detached and allowed to run
3369 independently. This is the default.
3372 Both processes will be held under the control of @value{GDBN}.
3373 One process (child or parent, depending on the value of
3374 @code{follow-fork-mode}) is debugged as usual, while the other
3379 @kindex show detach-on-fork
3380 @item show detach-on-fork
3381 Show whether detach-on-fork mode is on/off.
3384 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3385 will retain control of all forked processes (including nested forks).
3386 You can list the forked processes under the control of @value{GDBN} by
3387 using the @w{@code{info inferiors}} command, and switch from one fork
3388 to another by using the @code{inferior} command (@pxref{Inferiors and
3389 Programs, ,Debugging Multiple Inferiors and Programs}).
3391 To quit debugging one of the forked processes, you can either detach
3392 from it by using the @w{@code{detach inferiors}} command (allowing it
3393 to run independently), or kill it using the @w{@code{kill inferiors}}
3394 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3397 If you ask to debug a child process and a @code{vfork} is followed by an
3398 @code{exec}, @value{GDBN} executes the new target up to the first
3399 breakpoint in the new target. If you have a breakpoint set on
3400 @code{main} in your original program, the breakpoint will also be set on
3401 the child process's @code{main}.
3403 On some systems, when a child process is spawned by @code{vfork}, you
3404 cannot debug the child or parent until an @code{exec} call completes.
3406 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3407 call executes, the new target restarts. To restart the parent
3408 process, use the @code{file} command with the parent executable name
3409 as its argument. By default, after an @code{exec} call executes,
3410 @value{GDBN} discards the symbols of the previous executable image.
3411 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3415 @kindex set follow-exec-mode
3416 @item set follow-exec-mode @var{mode}
3418 Set debugger response to a program call of @code{exec}. An
3419 @code{exec} call replaces the program image of a process.
3421 @code{follow-exec-mode} can be:
3425 @value{GDBN} creates a new inferior and rebinds the process to this
3426 new inferior. The program the process was running before the
3427 @code{exec} call can be restarted afterwards by restarting the
3433 (@value{GDBP}) info inferiors
3435 Id Description Executable
3438 process 12020 is executing new program: prog2
3439 Program exited normally.
3440 (@value{GDBP}) info inferiors
3441 Id Description Executable
3447 @value{GDBN} keeps the process bound to the same inferior. The new
3448 executable image replaces the previous executable loaded in the
3449 inferior. Restarting the inferior after the @code{exec} call, with
3450 e.g., the @code{run} command, restarts the executable the process was
3451 running after the @code{exec} call. This is the default mode.
3456 (@value{GDBP}) info inferiors
3457 Id Description Executable
3460 process 12020 is executing new program: prog2
3461 Program exited normally.
3462 (@value{GDBP}) info inferiors
3463 Id Description Executable
3470 @code{follow-exec-mode} is supported in native mode and
3471 @code{target extended-remote} mode.
3473 You can use the @code{catch} command to make @value{GDBN} stop whenever
3474 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3475 Catchpoints, ,Setting Catchpoints}.
3477 @node Checkpoint/Restart
3478 @section Setting a @emph{Bookmark} to Return to Later
3483 @cindex snapshot of a process
3484 @cindex rewind program state
3486 On certain operating systems@footnote{Currently, only
3487 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3488 program's state, called a @dfn{checkpoint}, and come back to it
3491 Returning to a checkpoint effectively undoes everything that has
3492 happened in the program since the @code{checkpoint} was saved. This
3493 includes changes in memory, registers, and even (within some limits)
3494 system state. Effectively, it is like going back in time to the
3495 moment when the checkpoint was saved.
3497 Thus, if you're stepping thru a program and you think you're
3498 getting close to the point where things go wrong, you can save
3499 a checkpoint. Then, if you accidentally go too far and miss
3500 the critical statement, instead of having to restart your program
3501 from the beginning, you can just go back to the checkpoint and
3502 start again from there.
3504 This can be especially useful if it takes a lot of time or
3505 steps to reach the point where you think the bug occurs.
3507 To use the @code{checkpoint}/@code{restart} method of debugging:
3512 Save a snapshot of the debugged program's current execution state.
3513 The @code{checkpoint} command takes no arguments, but each checkpoint
3514 is assigned a small integer id, similar to a breakpoint id.
3516 @kindex info checkpoints
3517 @item info checkpoints
3518 List the checkpoints that have been saved in the current debugging
3519 session. For each checkpoint, the following information will be
3526 @item Source line, or label
3529 @kindex restart @var{checkpoint-id}
3530 @item restart @var{checkpoint-id}
3531 Restore the program state that was saved as checkpoint number
3532 @var{checkpoint-id}. All program variables, registers, stack frames
3533 etc.@: will be returned to the values that they had when the checkpoint
3534 was saved. In essence, gdb will ``wind back the clock'' to the point
3535 in time when the checkpoint was saved.
3537 Note that breakpoints, @value{GDBN} variables, command history etc.
3538 are not affected by restoring a checkpoint. In general, a checkpoint
3539 only restores things that reside in the program being debugged, not in
3542 @kindex delete checkpoint @var{checkpoint-id}
3543 @item delete checkpoint @var{checkpoint-id}
3544 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3548 Returning to a previously saved checkpoint will restore the user state
3549 of the program being debugged, plus a significant subset of the system
3550 (OS) state, including file pointers. It won't ``un-write'' data from
3551 a file, but it will rewind the file pointer to the previous location,
3552 so that the previously written data can be overwritten. For files
3553 opened in read mode, the pointer will also be restored so that the
3554 previously read data can be read again.
3556 Of course, characters that have been sent to a printer (or other
3557 external device) cannot be ``snatched back'', and characters received
3558 from eg.@: a serial device can be removed from internal program buffers,
3559 but they cannot be ``pushed back'' into the serial pipeline, ready to
3560 be received again. Similarly, the actual contents of files that have
3561 been changed cannot be restored (at this time).
3563 However, within those constraints, you actually can ``rewind'' your
3564 program to a previously saved point in time, and begin debugging it
3565 again --- and you can change the course of events so as to debug a
3566 different execution path this time.
3568 @cindex checkpoints and process id
3569 Finally, there is one bit of internal program state that will be
3570 different when you return to a checkpoint --- the program's process
3571 id. Each checkpoint will have a unique process id (or @var{pid}),
3572 and each will be different from the program's original @var{pid}.
3573 If your program has saved a local copy of its process id, this could
3574 potentially pose a problem.
3576 @subsection A Non-obvious Benefit of Using Checkpoints
3578 On some systems such as @sc{gnu}/Linux, address space randomization
3579 is performed on new processes for security reasons. This makes it
3580 difficult or impossible to set a breakpoint, or watchpoint, on an
3581 absolute address if you have to restart the program, since the
3582 absolute location of a symbol will change from one execution to the
3585 A checkpoint, however, is an @emph{identical} copy of a process.
3586 Therefore if you create a checkpoint at (eg.@:) the start of main,
3587 and simply return to that checkpoint instead of restarting the
3588 process, you can avoid the effects of address randomization and
3589 your symbols will all stay in the same place.
3592 @chapter Stopping and Continuing
3594 The principal purposes of using a debugger are so that you can stop your
3595 program before it terminates; or so that, if your program runs into
3596 trouble, you can investigate and find out why.
3598 Inside @value{GDBN}, your program may stop for any of several reasons,
3599 such as a signal, a breakpoint, or reaching a new line after a
3600 @value{GDBN} command such as @code{step}. You may then examine and
3601 change variables, set new breakpoints or remove old ones, and then
3602 continue execution. Usually, the messages shown by @value{GDBN} provide
3603 ample explanation of the status of your program---but you can also
3604 explicitly request this information at any time.
3607 @kindex info program
3609 Display information about the status of your program: whether it is
3610 running or not, what process it is, and why it stopped.
3614 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3615 * Continuing and Stepping:: Resuming execution
3616 * Skipping Over Functions and Files::
3617 Skipping over functions and files
3619 * Thread Stops:: Stopping and starting multi-thread programs
3623 @section Breakpoints, Watchpoints, and Catchpoints
3626 A @dfn{breakpoint} makes your program stop whenever a certain point in
3627 the program is reached. For each breakpoint, you can add conditions to
3628 control in finer detail whether your program stops. You can set
3629 breakpoints with the @code{break} command and its variants (@pxref{Set
3630 Breaks, ,Setting Breakpoints}), to specify the place where your program
3631 should stop by line number, function name or exact address in the
3634 On some systems, you can set breakpoints in shared libraries before
3635 the executable is run.
3638 @cindex data breakpoints
3639 @cindex memory tracing
3640 @cindex breakpoint on memory address
3641 @cindex breakpoint on variable modification
3642 A @dfn{watchpoint} is a special breakpoint that stops your program
3643 when the value of an expression changes. The expression may be a value
3644 of a variable, or it could involve values of one or more variables
3645 combined by operators, such as @samp{a + b}. This is sometimes called
3646 @dfn{data breakpoints}. You must use a different command to set
3647 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3648 from that, you can manage a watchpoint like any other breakpoint: you
3649 enable, disable, and delete both breakpoints and watchpoints using the
3652 You can arrange to have values from your program displayed automatically
3653 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3657 @cindex breakpoint on events
3658 A @dfn{catchpoint} is another special breakpoint that stops your program
3659 when a certain kind of event occurs, such as the throwing of a C@t{++}
3660 exception or the loading of a library. As with watchpoints, you use a
3661 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3662 Catchpoints}), but aside from that, you can manage a catchpoint like any
3663 other breakpoint. (To stop when your program receives a signal, use the
3664 @code{handle} command; see @ref{Signals, ,Signals}.)
3666 @cindex breakpoint numbers
3667 @cindex numbers for breakpoints
3668 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3669 catchpoint when you create it; these numbers are successive integers
3670 starting with one. In many of the commands for controlling various
3671 features of breakpoints you use the breakpoint number to say which
3672 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3673 @dfn{disabled}; if disabled, it has no effect on your program until you
3676 @cindex breakpoint ranges
3677 @cindex breakpoint lists
3678 @cindex ranges of breakpoints
3679 @cindex lists of breakpoints
3680 Some @value{GDBN} commands accept a space-separated list of breakpoints
3681 on which to operate. A list element can be either a single breakpoint number,
3682 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3683 When a breakpoint list is given to a command, all breakpoints in that list
3687 * Set Breaks:: Setting breakpoints
3688 * Set Watchpoints:: Setting watchpoints
3689 * Set Catchpoints:: Setting catchpoints
3690 * Delete Breaks:: Deleting breakpoints
3691 * Disabling:: Disabling breakpoints
3692 * Conditions:: Break conditions
3693 * Break Commands:: Breakpoint command lists
3694 * Dynamic Printf:: Dynamic printf
3695 * Save Breakpoints:: How to save breakpoints in a file
3696 * Static Probe Points:: Listing static probe points
3697 * Error in Breakpoints:: ``Cannot insert breakpoints''
3698 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3702 @subsection Setting Breakpoints
3704 @c FIXME LMB what does GDB do if no code on line of breakpt?
3705 @c consider in particular declaration with/without initialization.
3707 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3710 @kindex b @r{(@code{break})}
3711 @vindex $bpnum@r{, convenience variable}
3712 @cindex latest breakpoint
3713 Breakpoints are set with the @code{break} command (abbreviated
3714 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3715 number of the breakpoint you've set most recently; see @ref{Convenience
3716 Vars,, Convenience Variables}, for a discussion of what you can do with
3717 convenience variables.
3720 @item break @var{location}
3721 Set a breakpoint at the given @var{location}, which can specify a
3722 function name, a line number, or an address of an instruction.
3723 (@xref{Specify Location}, for a list of all the possible ways to
3724 specify a @var{location}.) The breakpoint will stop your program just
3725 before it executes any of the code in the specified @var{location}.
3727 When using source languages that permit overloading of symbols, such as
3728 C@t{++}, a function name may refer to more than one possible place to break.
3729 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3732 It is also possible to insert a breakpoint that will stop the program
3733 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3734 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3737 When called without any arguments, @code{break} sets a breakpoint at
3738 the next instruction to be executed in the selected stack frame
3739 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3740 innermost, this makes your program stop as soon as control
3741 returns to that frame. This is similar to the effect of a
3742 @code{finish} command in the frame inside the selected frame---except
3743 that @code{finish} does not leave an active breakpoint. If you use
3744 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3745 the next time it reaches the current location; this may be useful
3748 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3749 least one instruction has been executed. If it did not do this, you
3750 would be unable to proceed past a breakpoint without first disabling the
3751 breakpoint. This rule applies whether or not the breakpoint already
3752 existed when your program stopped.
3754 @item break @dots{} if @var{cond}
3755 Set a breakpoint with condition @var{cond}; evaluate the expression
3756 @var{cond} each time the breakpoint is reached, and stop only if the
3757 value is nonzero---that is, if @var{cond} evaluates as true.
3758 @samp{@dots{}} stands for one of the possible arguments described
3759 above (or no argument) specifying where to break. @xref{Conditions,
3760 ,Break Conditions}, for more information on breakpoint conditions.
3763 @item tbreak @var{args}
3764 Set a breakpoint enabled only for one stop. The @var{args} are the
3765 same as for the @code{break} command, and the breakpoint is set in the same
3766 way, but the breakpoint is automatically deleted after the first time your
3767 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3770 @cindex hardware breakpoints
3771 @item hbreak @var{args}
3772 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3773 @code{break} command and the breakpoint is set in the same way, but the
3774 breakpoint requires hardware support and some target hardware may not
3775 have this support. The main purpose of this is EPROM/ROM code
3776 debugging, so you can set a breakpoint at an instruction without
3777 changing the instruction. This can be used with the new trap-generation
3778 provided by SPARClite DSU and most x86-based targets. These targets
3779 will generate traps when a program accesses some data or instruction
3780 address that is assigned to the debug registers. However the hardware
3781 breakpoint registers can take a limited number of breakpoints. For
3782 example, on the DSU, only two data breakpoints can be set at a time, and
3783 @value{GDBN} will reject this command if more than two are used. Delete
3784 or disable unused hardware breakpoints before setting new ones
3785 (@pxref{Disabling, ,Disabling Breakpoints}).
3786 @xref{Conditions, ,Break Conditions}.
3787 For remote targets, you can restrict the number of hardware
3788 breakpoints @value{GDBN} will use, see @ref{set remote
3789 hardware-breakpoint-limit}.
3792 @item thbreak @var{args}
3793 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3794 are the same as for the @code{hbreak} command and the breakpoint is set in
3795 the same way. However, like the @code{tbreak} command,
3796 the breakpoint is automatically deleted after the
3797 first time your program stops there. Also, like the @code{hbreak}
3798 command, the breakpoint requires hardware support and some target hardware
3799 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3800 See also @ref{Conditions, ,Break Conditions}.
3803 @cindex regular expression
3804 @cindex breakpoints at functions matching a regexp
3805 @cindex set breakpoints in many functions
3806 @item rbreak @var{regex}
3807 Set breakpoints on all functions matching the regular expression
3808 @var{regex}. This command sets an unconditional breakpoint on all
3809 matches, printing a list of all breakpoints it set. Once these
3810 breakpoints are set, they are treated just like the breakpoints set with
3811 the @code{break} command. You can delete them, disable them, or make
3812 them conditional the same way as any other breakpoint.
3814 The syntax of the regular expression is the standard one used with tools
3815 like @file{grep}. Note that this is different from the syntax used by
3816 shells, so for instance @code{foo*} matches all functions that include
3817 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3818 @code{.*} leading and trailing the regular expression you supply, so to
3819 match only functions that begin with @code{foo}, use @code{^foo}.
3821 @cindex non-member C@t{++} functions, set breakpoint in
3822 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3823 breakpoints on overloaded functions that are not members of any special
3826 @cindex set breakpoints on all functions
3827 The @code{rbreak} command can be used to set breakpoints in
3828 @strong{all} the functions in a program, like this:
3831 (@value{GDBP}) rbreak .
3834 @item rbreak @var{file}:@var{regex}
3835 If @code{rbreak} is called with a filename qualification, it limits
3836 the search for functions matching the given regular expression to the
3837 specified @var{file}. This can be used, for example, to set breakpoints on
3838 every function in a given file:
3841 (@value{GDBP}) rbreak file.c:.
3844 The colon separating the filename qualifier from the regex may
3845 optionally be surrounded by spaces.
3847 @kindex info breakpoints
3848 @cindex @code{$_} and @code{info breakpoints}
3849 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3850 @itemx info break @r{[}@var{list}@dots{}@r{]}
3851 Print a table of all breakpoints, watchpoints, and catchpoints set and
3852 not deleted. Optional argument @var{n} means print information only
3853 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3854 For each breakpoint, following columns are printed:
3857 @item Breakpoint Numbers
3859 Breakpoint, watchpoint, or catchpoint.
3861 Whether the breakpoint is marked to be disabled or deleted when hit.
3862 @item Enabled or Disabled
3863 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3864 that are not enabled.
3866 Where the breakpoint is in your program, as a memory address. For a
3867 pending breakpoint whose address is not yet known, this field will
3868 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3869 library that has the symbol or line referred by breakpoint is loaded.
3870 See below for details. A breakpoint with several locations will
3871 have @samp{<MULTIPLE>} in this field---see below for details.
3873 Where the breakpoint is in the source for your program, as a file and
3874 line number. For a pending breakpoint, the original string passed to
3875 the breakpoint command will be listed as it cannot be resolved until
3876 the appropriate shared library is loaded in the future.
3880 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3881 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3882 @value{GDBN} on the host's side. If it is ``target'', then the condition
3883 is evaluated by the target. The @code{info break} command shows
3884 the condition on the line following the affected breakpoint, together with
3885 its condition evaluation mode in between parentheses.
3887 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3888 allowed to have a condition specified for it. The condition is not parsed for
3889 validity until a shared library is loaded that allows the pending
3890 breakpoint to resolve to a valid location.
3893 @code{info break} with a breakpoint
3894 number @var{n} as argument lists only that breakpoint. The
3895 convenience variable @code{$_} and the default examining-address for
3896 the @code{x} command are set to the address of the last breakpoint
3897 listed (@pxref{Memory, ,Examining Memory}).
3900 @code{info break} displays a count of the number of times the breakpoint
3901 has been hit. This is especially useful in conjunction with the
3902 @code{ignore} command. You can ignore a large number of breakpoint
3903 hits, look at the breakpoint info to see how many times the breakpoint
3904 was hit, and then run again, ignoring one less than that number. This
3905 will get you quickly to the last hit of that breakpoint.
3908 For a breakpoints with an enable count (xref) greater than 1,
3909 @code{info break} also displays that count.
3913 @value{GDBN} allows you to set any number of breakpoints at the same place in
3914 your program. There is nothing silly or meaningless about this. When
3915 the breakpoints are conditional, this is even useful
3916 (@pxref{Conditions, ,Break Conditions}).
3918 @cindex multiple locations, breakpoints
3919 @cindex breakpoints, multiple locations
3920 It is possible that a breakpoint corresponds to several locations
3921 in your program. Examples of this situation are:
3925 Multiple functions in the program may have the same name.
3928 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3929 instances of the function body, used in different cases.
3932 For a C@t{++} template function, a given line in the function can
3933 correspond to any number of instantiations.
3936 For an inlined function, a given source line can correspond to
3937 several places where that function is inlined.
3940 In all those cases, @value{GDBN} will insert a breakpoint at all
3941 the relevant locations.
3943 A breakpoint with multiple locations is displayed in the breakpoint
3944 table using several rows---one header row, followed by one row for
3945 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3946 address column. The rows for individual locations contain the actual
3947 addresses for locations, and show the functions to which those
3948 locations belong. The number column for a location is of the form
3949 @var{breakpoint-number}.@var{location-number}.
3954 Num Type Disp Enb Address What
3955 1 breakpoint keep y <MULTIPLE>
3957 breakpoint already hit 1 time
3958 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3959 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3962 You cannot delete the individual locations from a breakpoint. However,
3963 each location can be individually enabled or disabled by passing
3964 @var{breakpoint-number}.@var{location-number} as argument to the
3965 @code{enable} and @code{disable} commands. It's also possible to
3966 @code{enable} and @code{disable} a range of @var{location-number}
3967 locations using a @var{breakpoint-number} and two @var{location-number}s,
3968 in increasing order, separated by a hyphen, like
3969 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3970 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3971 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3972 all of the locations that belong to that breakpoint.
3974 @cindex pending breakpoints
3975 It's quite common to have a breakpoint inside a shared library.
3976 Shared libraries can be loaded and unloaded explicitly,
3977 and possibly repeatedly, as the program is executed. To support
3978 this use case, @value{GDBN} updates breakpoint locations whenever
3979 any shared library is loaded or unloaded. Typically, you would
3980 set a breakpoint in a shared library at the beginning of your
3981 debugging session, when the library is not loaded, and when the
3982 symbols from the library are not available. When you try to set
3983 breakpoint, @value{GDBN} will ask you if you want to set
3984 a so called @dfn{pending breakpoint}---breakpoint whose address
3985 is not yet resolved.
3987 After the program is run, whenever a new shared library is loaded,
3988 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3989 shared library contains the symbol or line referred to by some
3990 pending breakpoint, that breakpoint is resolved and becomes an
3991 ordinary breakpoint. When a library is unloaded, all breakpoints
3992 that refer to its symbols or source lines become pending again.
3994 This logic works for breakpoints with multiple locations, too. For
3995 example, if you have a breakpoint in a C@t{++} template function, and
3996 a newly loaded shared library has an instantiation of that template,
3997 a new location is added to the list of locations for the breakpoint.
3999 Except for having unresolved address, pending breakpoints do not
4000 differ from regular breakpoints. You can set conditions or commands,
4001 enable and disable them and perform other breakpoint operations.
4003 @value{GDBN} provides some additional commands for controlling what
4004 happens when the @samp{break} command cannot resolve breakpoint
4005 address specification to an address:
4007 @kindex set breakpoint pending
4008 @kindex show breakpoint pending
4010 @item set breakpoint pending auto
4011 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4012 location, it queries you whether a pending breakpoint should be created.
4014 @item set breakpoint pending on
4015 This indicates that an unrecognized breakpoint location should automatically
4016 result in a pending breakpoint being created.
4018 @item set breakpoint pending off
4019 This indicates that pending breakpoints are not to be created. Any
4020 unrecognized breakpoint location results in an error. This setting does
4021 not affect any pending breakpoints previously created.
4023 @item show breakpoint pending
4024 Show the current behavior setting for creating pending breakpoints.
4027 The settings above only affect the @code{break} command and its
4028 variants. Once breakpoint is set, it will be automatically updated
4029 as shared libraries are loaded and unloaded.
4031 @cindex automatic hardware breakpoints
4032 For some targets, @value{GDBN} can automatically decide if hardware or
4033 software breakpoints should be used, depending on whether the
4034 breakpoint address is read-only or read-write. This applies to
4035 breakpoints set with the @code{break} command as well as to internal
4036 breakpoints set by commands like @code{next} and @code{finish}. For
4037 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4040 You can control this automatic behaviour with the following commands:
4042 @kindex set breakpoint auto-hw
4043 @kindex show breakpoint auto-hw
4045 @item set breakpoint auto-hw on
4046 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4047 will try to use the target memory map to decide if software or hardware
4048 breakpoint must be used.
4050 @item set breakpoint auto-hw off
4051 This indicates @value{GDBN} should not automatically select breakpoint
4052 type. If the target provides a memory map, @value{GDBN} will warn when
4053 trying to set software breakpoint at a read-only address.
4056 @value{GDBN} normally implements breakpoints by replacing the program code
4057 at the breakpoint address with a special instruction, which, when
4058 executed, given control to the debugger. By default, the program
4059 code is so modified only when the program is resumed. As soon as
4060 the program stops, @value{GDBN} restores the original instructions. This
4061 behaviour guards against leaving breakpoints inserted in the
4062 target should gdb abrubptly disconnect. However, with slow remote
4063 targets, inserting and removing breakpoint can reduce the performance.
4064 This behavior can be controlled with the following commands::
4066 @kindex set breakpoint always-inserted
4067 @kindex show breakpoint always-inserted
4069 @item set breakpoint always-inserted off
4070 All breakpoints, including newly added by the user, are inserted in
4071 the target only when the target is resumed. All breakpoints are
4072 removed from the target when it stops. This is the default mode.
4074 @item set breakpoint always-inserted on
4075 Causes all breakpoints to be inserted in the target at all times. If
4076 the user adds a new breakpoint, or changes an existing breakpoint, the
4077 breakpoints in the target are updated immediately. A breakpoint is
4078 removed from the target only when breakpoint itself is deleted.
4081 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4082 when a breakpoint breaks. If the condition is true, then the process being
4083 debugged stops, otherwise the process is resumed.
4085 If the target supports evaluating conditions on its end, @value{GDBN} may
4086 download the breakpoint, together with its conditions, to it.
4088 This feature can be controlled via the following commands:
4090 @kindex set breakpoint condition-evaluation
4091 @kindex show breakpoint condition-evaluation
4093 @item set breakpoint condition-evaluation host
4094 This option commands @value{GDBN} to evaluate the breakpoint
4095 conditions on the host's side. Unconditional breakpoints are sent to
4096 the target which in turn receives the triggers and reports them back to GDB
4097 for condition evaluation. This is the standard evaluation mode.
4099 @item set breakpoint condition-evaluation target
4100 This option commands @value{GDBN} to download breakpoint conditions
4101 to the target at the moment of their insertion. The target
4102 is responsible for evaluating the conditional expression and reporting
4103 breakpoint stop events back to @value{GDBN} whenever the condition
4104 is true. Due to limitations of target-side evaluation, some conditions
4105 cannot be evaluated there, e.g., conditions that depend on local data
4106 that is only known to the host. Examples include
4107 conditional expressions involving convenience variables, complex types
4108 that cannot be handled by the agent expression parser and expressions
4109 that are too long to be sent over to the target, specially when the
4110 target is a remote system. In these cases, the conditions will be
4111 evaluated by @value{GDBN}.
4113 @item set breakpoint condition-evaluation auto
4114 This is the default mode. If the target supports evaluating breakpoint
4115 conditions on its end, @value{GDBN} will download breakpoint conditions to
4116 the target (limitations mentioned previously apply). If the target does
4117 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4118 to evaluating all these conditions on the host's side.
4122 @cindex negative breakpoint numbers
4123 @cindex internal @value{GDBN} breakpoints
4124 @value{GDBN} itself sometimes sets breakpoints in your program for
4125 special purposes, such as proper handling of @code{longjmp} (in C
4126 programs). These internal breakpoints are assigned negative numbers,
4127 starting with @code{-1}; @samp{info breakpoints} does not display them.
4128 You can see these breakpoints with the @value{GDBN} maintenance command
4129 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4132 @node Set Watchpoints
4133 @subsection Setting Watchpoints
4135 @cindex setting watchpoints
4136 You can use a watchpoint to stop execution whenever the value of an
4137 expression changes, without having to predict a particular place where
4138 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4139 The expression may be as simple as the value of a single variable, or
4140 as complex as many variables combined by operators. Examples include:
4144 A reference to the value of a single variable.
4147 An address cast to an appropriate data type. For example,
4148 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4149 address (assuming an @code{int} occupies 4 bytes).
4152 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4153 expression can use any operators valid in the program's native
4154 language (@pxref{Languages}).
4157 You can set a watchpoint on an expression even if the expression can
4158 not be evaluated yet. For instance, you can set a watchpoint on
4159 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4160 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4161 the expression produces a valid value. If the expression becomes
4162 valid in some other way than changing a variable (e.g.@: if the memory
4163 pointed to by @samp{*global_ptr} becomes readable as the result of a
4164 @code{malloc} call), @value{GDBN} may not stop until the next time
4165 the expression changes.
4167 @cindex software watchpoints
4168 @cindex hardware watchpoints
4169 Depending on your system, watchpoints may be implemented in software or
4170 hardware. @value{GDBN} does software watchpointing by single-stepping your
4171 program and testing the variable's value each time, which is hundreds of
4172 times slower than normal execution. (But this may still be worth it, to
4173 catch errors where you have no clue what part of your program is the
4176 On some systems, such as most PowerPC or x86-based targets,
4177 @value{GDBN} includes support for hardware watchpoints, which do not
4178 slow down the running of your program.
4182 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4183 Set a watchpoint for an expression. @value{GDBN} will break when the
4184 expression @var{expr} is written into by the program and its value
4185 changes. The simplest (and the most popular) use of this command is
4186 to watch the value of a single variable:
4189 (@value{GDBP}) watch foo
4192 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4193 argument, @value{GDBN} breaks only when the thread identified by
4194 @var{thread-id} changes the value of @var{expr}. If any other threads
4195 change the value of @var{expr}, @value{GDBN} will not break. Note
4196 that watchpoints restricted to a single thread in this way only work
4197 with Hardware Watchpoints.
4199 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4200 (see below). The @code{-location} argument tells @value{GDBN} to
4201 instead watch the memory referred to by @var{expr}. In this case,
4202 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4203 and watch the memory at that address. The type of the result is used
4204 to determine the size of the watched memory. If the expression's
4205 result does not have an address, then @value{GDBN} will print an
4208 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4209 of masked watchpoints, if the current architecture supports this
4210 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4211 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4212 to an address to watch. The mask specifies that some bits of an address
4213 (the bits which are reset in the mask) should be ignored when matching
4214 the address accessed by the inferior against the watchpoint address.
4215 Thus, a masked watchpoint watches many addresses simultaneously---those
4216 addresses whose unmasked bits are identical to the unmasked bits in the
4217 watchpoint address. The @code{mask} argument implies @code{-location}.
4221 (@value{GDBP}) watch foo mask 0xffff00ff
4222 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4226 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4227 Set a watchpoint that will break when the value of @var{expr} is read
4231 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4232 Set a watchpoint that will break when @var{expr} is either read from
4233 or written into by the program.
4235 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4236 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4237 This command prints a list of watchpoints, using the same format as
4238 @code{info break} (@pxref{Set Breaks}).
4241 If you watch for a change in a numerically entered address you need to
4242 dereference it, as the address itself is just a constant number which will
4243 never change. @value{GDBN} refuses to create a watchpoint that watches
4244 a never-changing value:
4247 (@value{GDBP}) watch 0x600850
4248 Cannot watch constant value 0x600850.
4249 (@value{GDBP}) watch *(int *) 0x600850
4250 Watchpoint 1: *(int *) 6293584
4253 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4254 watchpoints execute very quickly, and the debugger reports a change in
4255 value at the exact instruction where the change occurs. If @value{GDBN}
4256 cannot set a hardware watchpoint, it sets a software watchpoint, which
4257 executes more slowly and reports the change in value at the next
4258 @emph{statement}, not the instruction, after the change occurs.
4260 @cindex use only software watchpoints
4261 You can force @value{GDBN} to use only software watchpoints with the
4262 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4263 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4264 the underlying system supports them. (Note that hardware-assisted
4265 watchpoints that were set @emph{before} setting
4266 @code{can-use-hw-watchpoints} to zero will still use the hardware
4267 mechanism of watching expression values.)
4270 @item set can-use-hw-watchpoints
4271 @kindex set can-use-hw-watchpoints
4272 Set whether or not to use hardware watchpoints.
4274 @item show can-use-hw-watchpoints
4275 @kindex show can-use-hw-watchpoints
4276 Show the current mode of using hardware watchpoints.
4279 For remote targets, you can restrict the number of hardware
4280 watchpoints @value{GDBN} will use, see @ref{set remote
4281 hardware-breakpoint-limit}.
4283 When you issue the @code{watch} command, @value{GDBN} reports
4286 Hardware watchpoint @var{num}: @var{expr}
4290 if it was able to set a hardware watchpoint.
4292 Currently, the @code{awatch} and @code{rwatch} commands can only set
4293 hardware watchpoints, because accesses to data that don't change the
4294 value of the watched expression cannot be detected without examining
4295 every instruction as it is being executed, and @value{GDBN} does not do
4296 that currently. If @value{GDBN} finds that it is unable to set a
4297 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4298 will print a message like this:
4301 Expression cannot be implemented with read/access watchpoint.
4304 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4305 data type of the watched expression is wider than what a hardware
4306 watchpoint on the target machine can handle. For example, some systems
4307 can only watch regions that are up to 4 bytes wide; on such systems you
4308 cannot set hardware watchpoints for an expression that yields a
4309 double-precision floating-point number (which is typically 8 bytes
4310 wide). As a work-around, it might be possible to break the large region
4311 into a series of smaller ones and watch them with separate watchpoints.
4313 If you set too many hardware watchpoints, @value{GDBN} might be unable
4314 to insert all of them when you resume the execution of your program.
4315 Since the precise number of active watchpoints is unknown until such
4316 time as the program is about to be resumed, @value{GDBN} might not be
4317 able to warn you about this when you set the watchpoints, and the
4318 warning will be printed only when the program is resumed:
4321 Hardware watchpoint @var{num}: Could not insert watchpoint
4325 If this happens, delete or disable some of the watchpoints.
4327 Watching complex expressions that reference many variables can also
4328 exhaust the resources available for hardware-assisted watchpoints.
4329 That's because @value{GDBN} needs to watch every variable in the
4330 expression with separately allocated resources.
4332 If you call a function interactively using @code{print} or @code{call},
4333 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4334 kind of breakpoint or the call completes.
4336 @value{GDBN} automatically deletes watchpoints that watch local
4337 (automatic) variables, or expressions that involve such variables, when
4338 they go out of scope, that is, when the execution leaves the block in
4339 which these variables were defined. In particular, when the program
4340 being debugged terminates, @emph{all} local variables go out of scope,
4341 and so only watchpoints that watch global variables remain set. If you
4342 rerun the program, you will need to set all such watchpoints again. One
4343 way of doing that would be to set a code breakpoint at the entry to the
4344 @code{main} function and when it breaks, set all the watchpoints.
4346 @cindex watchpoints and threads
4347 @cindex threads and watchpoints
4348 In multi-threaded programs, watchpoints will detect changes to the
4349 watched expression from every thread.
4352 @emph{Warning:} In multi-threaded programs, software watchpoints
4353 have only limited usefulness. If @value{GDBN} creates a software
4354 watchpoint, it can only watch the value of an expression @emph{in a
4355 single thread}. If you are confident that the expression can only
4356 change due to the current thread's activity (and if you are also
4357 confident that no other thread can become current), then you can use
4358 software watchpoints as usual. However, @value{GDBN} may not notice
4359 when a non-current thread's activity changes the expression. (Hardware
4360 watchpoints, in contrast, watch an expression in all threads.)
4363 @xref{set remote hardware-watchpoint-limit}.
4365 @node Set Catchpoints
4366 @subsection Setting Catchpoints
4367 @cindex catchpoints, setting
4368 @cindex exception handlers
4369 @cindex event handling
4371 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4372 kinds of program events, such as C@t{++} exceptions or the loading of a
4373 shared library. Use the @code{catch} command to set a catchpoint.
4377 @item catch @var{event}
4378 Stop when @var{event} occurs. The @var{event} can be any of the following:
4381 @item throw @r{[}@var{regexp}@r{]}
4382 @itemx rethrow @r{[}@var{regexp}@r{]}
4383 @itemx catch @r{[}@var{regexp}@r{]}
4385 @kindex catch rethrow
4387 @cindex stop on C@t{++} exceptions
4388 The throwing, re-throwing, or catching of a C@t{++} exception.
4390 If @var{regexp} is given, then only exceptions whose type matches the
4391 regular expression will be caught.
4393 @vindex $_exception@r{, convenience variable}
4394 The convenience variable @code{$_exception} is available at an
4395 exception-related catchpoint, on some systems. This holds the
4396 exception being thrown.
4398 There are currently some limitations to C@t{++} exception handling in
4403 The support for these commands is system-dependent. Currently, only
4404 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4408 The regular expression feature and the @code{$_exception} convenience
4409 variable rely on the presence of some SDT probes in @code{libstdc++}.
4410 If these probes are not present, then these features cannot be used.
4411 These probes were first available in the GCC 4.8 release, but whether
4412 or not they are available in your GCC also depends on how it was
4416 The @code{$_exception} convenience variable is only valid at the
4417 instruction at which an exception-related catchpoint is set.
4420 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4421 location in the system library which implements runtime exception
4422 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4423 (@pxref{Selection}) to get to your code.
4426 If you call a function interactively, @value{GDBN} normally returns
4427 control to you when the function has finished executing. If the call
4428 raises an exception, however, the call may bypass the mechanism that
4429 returns control to you and cause your program either to abort or to
4430 simply continue running until it hits a breakpoint, catches a signal
4431 that @value{GDBN} is listening for, or exits. This is the case even if
4432 you set a catchpoint for the exception; catchpoints on exceptions are
4433 disabled within interactive calls. @xref{Calling}, for information on
4434 controlling this with @code{set unwind-on-terminating-exception}.
4437 You cannot raise an exception interactively.
4440 You cannot install an exception handler interactively.
4444 @kindex catch exception
4445 @cindex Ada exception catching
4446 @cindex catch Ada exceptions
4447 An Ada exception being raised. If an exception name is specified
4448 at the end of the command (eg @code{catch exception Program_Error}),
4449 the debugger will stop only when this specific exception is raised.
4450 Otherwise, the debugger stops execution when any Ada exception is raised.
4452 When inserting an exception catchpoint on a user-defined exception whose
4453 name is identical to one of the exceptions defined by the language, the
4454 fully qualified name must be used as the exception name. Otherwise,
4455 @value{GDBN} will assume that it should stop on the pre-defined exception
4456 rather than the user-defined one. For instance, assuming an exception
4457 called @code{Constraint_Error} is defined in package @code{Pck}, then
4458 the command to use to catch such exceptions is @kbd{catch exception
4459 Pck.Constraint_Error}.
4461 @item exception unhandled
4462 @kindex catch exception unhandled
4463 An exception that was raised but is not handled by the program.
4466 @kindex catch assert
4467 A failed Ada assertion.
4471 @cindex break on fork/exec
4472 A call to @code{exec}.
4475 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4476 @kindex catch syscall
4477 @cindex break on a system call.
4478 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4479 syscall is a mechanism for application programs to request a service
4480 from the operating system (OS) or one of the OS system services.
4481 @value{GDBN} can catch some or all of the syscalls issued by the
4482 debuggee, and show the related information for each syscall. If no
4483 argument is specified, calls to and returns from all system calls
4486 @var{name} can be any system call name that is valid for the
4487 underlying OS. Just what syscalls are valid depends on the OS. On
4488 GNU and Unix systems, you can find the full list of valid syscall
4489 names on @file{/usr/include/asm/unistd.h}.
4491 @c For MS-Windows, the syscall names and the corresponding numbers
4492 @c can be found, e.g., on this URL:
4493 @c http://www.metasploit.com/users/opcode/syscalls.html
4494 @c but we don't support Windows syscalls yet.
4496 Normally, @value{GDBN} knows in advance which syscalls are valid for
4497 each OS, so you can use the @value{GDBN} command-line completion
4498 facilities (@pxref{Completion,, command completion}) to list the
4501 You may also specify the system call numerically. A syscall's
4502 number is the value passed to the OS's syscall dispatcher to
4503 identify the requested service. When you specify the syscall by its
4504 name, @value{GDBN} uses its database of syscalls to convert the name
4505 into the corresponding numeric code, but using the number directly
4506 may be useful if @value{GDBN}'s database does not have the complete
4507 list of syscalls on your system (e.g., because @value{GDBN} lags
4508 behind the OS upgrades).
4510 You may specify a group of related syscalls to be caught at once using
4511 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4512 instance, on some platforms @value{GDBN} allows you to catch all
4513 network related syscalls, by passing the argument @code{group:network}
4514 to @code{catch syscall}. Note that not all syscall groups are
4515 available in every system. You can use the command completion
4516 facilities (@pxref{Completion,, command completion}) to list the
4517 syscall groups available on your environment.
4519 The example below illustrates how this command works if you don't provide
4523 (@value{GDBP}) catch syscall
4524 Catchpoint 1 (syscall)
4526 Starting program: /tmp/catch-syscall
4528 Catchpoint 1 (call to syscall 'close'), \
4529 0xffffe424 in __kernel_vsyscall ()
4533 Catchpoint 1 (returned from syscall 'close'), \
4534 0xffffe424 in __kernel_vsyscall ()
4538 Here is an example of catching a system call by name:
4541 (@value{GDBP}) catch syscall chroot
4542 Catchpoint 1 (syscall 'chroot' [61])
4544 Starting program: /tmp/catch-syscall
4546 Catchpoint 1 (call to syscall 'chroot'), \
4547 0xffffe424 in __kernel_vsyscall ()
4551 Catchpoint 1 (returned from syscall 'chroot'), \
4552 0xffffe424 in __kernel_vsyscall ()
4556 An example of specifying a system call numerically. In the case
4557 below, the syscall number has a corresponding entry in the XML
4558 file, so @value{GDBN} finds its name and prints it:
4561 (@value{GDBP}) catch syscall 252
4562 Catchpoint 1 (syscall(s) 'exit_group')
4564 Starting program: /tmp/catch-syscall
4566 Catchpoint 1 (call to syscall 'exit_group'), \
4567 0xffffe424 in __kernel_vsyscall ()
4571 Program exited normally.
4575 Here is an example of catching a syscall group:
4578 (@value{GDBP}) catch syscall group:process
4579 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4580 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4581 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4583 Starting program: /tmp/catch-syscall
4585 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4586 from /lib64/ld-linux-x86-64.so.2
4592 However, there can be situations when there is no corresponding name
4593 in XML file for that syscall number. In this case, @value{GDBN} prints
4594 a warning message saying that it was not able to find the syscall name,
4595 but the catchpoint will be set anyway. See the example below:
4598 (@value{GDBP}) catch syscall 764
4599 warning: The number '764' does not represent a known syscall.
4600 Catchpoint 2 (syscall 764)
4604 If you configure @value{GDBN} using the @samp{--without-expat} option,
4605 it will not be able to display syscall names. Also, if your
4606 architecture does not have an XML file describing its system calls,
4607 you will not be able to see the syscall names. It is important to
4608 notice that these two features are used for accessing the syscall
4609 name database. In either case, you will see a warning like this:
4612 (@value{GDBP}) catch syscall
4613 warning: Could not open "syscalls/i386-linux.xml"
4614 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4615 GDB will not be able to display syscall names.
4616 Catchpoint 1 (syscall)
4620 Of course, the file name will change depending on your architecture and system.
4622 Still using the example above, you can also try to catch a syscall by its
4623 number. In this case, you would see something like:
4626 (@value{GDBP}) catch syscall 252
4627 Catchpoint 1 (syscall(s) 252)
4630 Again, in this case @value{GDBN} would not be able to display syscall's names.
4634 A call to @code{fork}.
4638 A call to @code{vfork}.
4640 @item load @r{[}regexp@r{]}
4641 @itemx unload @r{[}regexp@r{]}
4643 @kindex catch unload
4644 The loading or unloading of a shared library. If @var{regexp} is
4645 given, then the catchpoint will stop only if the regular expression
4646 matches one of the affected libraries.
4648 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4649 @kindex catch signal
4650 The delivery of a signal.
4652 With no arguments, this catchpoint will catch any signal that is not
4653 used internally by @value{GDBN}, specifically, all signals except
4654 @samp{SIGTRAP} and @samp{SIGINT}.
4656 With the argument @samp{all}, all signals, including those used by
4657 @value{GDBN}, will be caught. This argument cannot be used with other
4660 Otherwise, the arguments are a list of signal names as given to
4661 @code{handle} (@pxref{Signals}). Only signals specified in this list
4664 One reason that @code{catch signal} can be more useful than
4665 @code{handle} is that you can attach commands and conditions to the
4668 When a signal is caught by a catchpoint, the signal's @code{stop} and
4669 @code{print} settings, as specified by @code{handle}, are ignored.
4670 However, whether the signal is still delivered to the inferior depends
4671 on the @code{pass} setting; this can be changed in the catchpoint's
4676 @item tcatch @var{event}
4678 Set a catchpoint that is enabled only for one stop. The catchpoint is
4679 automatically deleted after the first time the event is caught.
4683 Use the @code{info break} command to list the current catchpoints.
4687 @subsection Deleting Breakpoints
4689 @cindex clearing breakpoints, watchpoints, catchpoints
4690 @cindex deleting breakpoints, watchpoints, catchpoints
4691 It is often necessary to eliminate a breakpoint, watchpoint, or
4692 catchpoint once it has done its job and you no longer want your program
4693 to stop there. This is called @dfn{deleting} the breakpoint. A
4694 breakpoint that has been deleted no longer exists; it is forgotten.
4696 With the @code{clear} command you can delete breakpoints according to
4697 where they are in your program. With the @code{delete} command you can
4698 delete individual breakpoints, watchpoints, or catchpoints by specifying
4699 their breakpoint numbers.
4701 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4702 automatically ignores breakpoints on the first instruction to be executed
4703 when you continue execution without changing the execution address.
4708 Delete any breakpoints at the next instruction to be executed in the
4709 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4710 the innermost frame is selected, this is a good way to delete a
4711 breakpoint where your program just stopped.
4713 @item clear @var{location}
4714 Delete any breakpoints set at the specified @var{location}.
4715 @xref{Specify Location}, for the various forms of @var{location}; the
4716 most useful ones are listed below:
4719 @item clear @var{function}
4720 @itemx clear @var{filename}:@var{function}
4721 Delete any breakpoints set at entry to the named @var{function}.
4723 @item clear @var{linenum}
4724 @itemx clear @var{filename}:@var{linenum}
4725 Delete any breakpoints set at or within the code of the specified
4726 @var{linenum} of the specified @var{filename}.
4729 @cindex delete breakpoints
4731 @kindex d @r{(@code{delete})}
4732 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4733 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4734 list specified as argument. If no argument is specified, delete all
4735 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4736 confirm off}). You can abbreviate this command as @code{d}.
4740 @subsection Disabling Breakpoints
4742 @cindex enable/disable a breakpoint
4743 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4744 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4745 it had been deleted, but remembers the information on the breakpoint so
4746 that you can @dfn{enable} it again later.
4748 You disable and enable breakpoints, watchpoints, and catchpoints with
4749 the @code{enable} and @code{disable} commands, optionally specifying
4750 one or more breakpoint numbers as arguments. Use @code{info break} to
4751 print a list of all breakpoints, watchpoints, and catchpoints if you
4752 do not know which numbers to use.
4754 Disabling and enabling a breakpoint that has multiple locations
4755 affects all of its locations.
4757 A breakpoint, watchpoint, or catchpoint can have any of several
4758 different states of enablement:
4762 Enabled. The breakpoint stops your program. A breakpoint set
4763 with the @code{break} command starts out in this state.
4765 Disabled. The breakpoint has no effect on your program.
4767 Enabled once. The breakpoint stops your program, but then becomes
4770 Enabled for a count. The breakpoint stops your program for the next
4771 N times, then becomes disabled.
4773 Enabled for deletion. The breakpoint stops your program, but
4774 immediately after it does so it is deleted permanently. A breakpoint
4775 set with the @code{tbreak} command starts out in this state.
4778 You can use the following commands to enable or disable breakpoints,
4779 watchpoints, and catchpoints:
4783 @kindex dis @r{(@code{disable})}
4784 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4785 Disable the specified breakpoints---or all breakpoints, if none are
4786 listed. A disabled breakpoint has no effect but is not forgotten. All
4787 options such as ignore-counts, conditions and commands are remembered in
4788 case the breakpoint is enabled again later. You may abbreviate
4789 @code{disable} as @code{dis}.
4792 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4793 Enable the specified breakpoints (or all defined breakpoints). They
4794 become effective once again in stopping your program.
4796 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4797 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4798 of these breakpoints immediately after stopping your program.
4800 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4801 Enable the specified breakpoints temporarily. @value{GDBN} records
4802 @var{count} with each of the specified breakpoints, and decrements a
4803 breakpoint's count when it is hit. When any count reaches 0,
4804 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4805 count (@pxref{Conditions, ,Break Conditions}), that will be
4806 decremented to 0 before @var{count} is affected.
4808 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4809 Enable the specified breakpoints to work once, then die. @value{GDBN}
4810 deletes any of these breakpoints as soon as your program stops there.
4811 Breakpoints set by the @code{tbreak} command start out in this state.
4814 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4815 @c confusing: tbreak is also initially enabled.
4816 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4817 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4818 subsequently, they become disabled or enabled only when you use one of
4819 the commands above. (The command @code{until} can set and delete a
4820 breakpoint of its own, but it does not change the state of your other
4821 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4825 @subsection Break Conditions
4826 @cindex conditional breakpoints
4827 @cindex breakpoint conditions
4829 @c FIXME what is scope of break condition expr? Context where wanted?
4830 @c in particular for a watchpoint?
4831 The simplest sort of breakpoint breaks every time your program reaches a
4832 specified place. You can also specify a @dfn{condition} for a
4833 breakpoint. A condition is just a Boolean expression in your
4834 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4835 a condition evaluates the expression each time your program reaches it,
4836 and your program stops only if the condition is @emph{true}.
4838 This is the converse of using assertions for program validation; in that
4839 situation, you want to stop when the assertion is violated---that is,
4840 when the condition is false. In C, if you want to test an assertion expressed
4841 by the condition @var{assert}, you should set the condition
4842 @samp{! @var{assert}} on the appropriate breakpoint.
4844 Conditions are also accepted for watchpoints; you may not need them,
4845 since a watchpoint is inspecting the value of an expression anyhow---but
4846 it might be simpler, say, to just set a watchpoint on a variable name,
4847 and specify a condition that tests whether the new value is an interesting
4850 Break conditions can have side effects, and may even call functions in
4851 your program. This can be useful, for example, to activate functions
4852 that log program progress, or to use your own print functions to
4853 format special data structures. The effects are completely predictable
4854 unless there is another enabled breakpoint at the same address. (In
4855 that case, @value{GDBN} might see the other breakpoint first and stop your
4856 program without checking the condition of this one.) Note that
4857 breakpoint commands are usually more convenient and flexible than break
4859 purpose of performing side effects when a breakpoint is reached
4860 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4862 Breakpoint conditions can also be evaluated on the target's side if
4863 the target supports it. Instead of evaluating the conditions locally,
4864 @value{GDBN} encodes the expression into an agent expression
4865 (@pxref{Agent Expressions}) suitable for execution on the target,
4866 independently of @value{GDBN}. Global variables become raw memory
4867 locations, locals become stack accesses, and so forth.
4869 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4870 when its condition evaluates to true. This mechanism may provide faster
4871 response times depending on the performance characteristics of the target
4872 since it does not need to keep @value{GDBN} informed about
4873 every breakpoint trigger, even those with false conditions.
4875 Break conditions can be specified when a breakpoint is set, by using
4876 @samp{if} in the arguments to the @code{break} command. @xref{Set
4877 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4878 with the @code{condition} command.
4880 You can also use the @code{if} keyword with the @code{watch} command.
4881 The @code{catch} command does not recognize the @code{if} keyword;
4882 @code{condition} is the only way to impose a further condition on a
4887 @item condition @var{bnum} @var{expression}
4888 Specify @var{expression} as the break condition for breakpoint,
4889 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4890 breakpoint @var{bnum} stops your program only if the value of
4891 @var{expression} is true (nonzero, in C). When you use
4892 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4893 syntactic correctness, and to determine whether symbols in it have
4894 referents in the context of your breakpoint. If @var{expression} uses
4895 symbols not referenced in the context of the breakpoint, @value{GDBN}
4896 prints an error message:
4899 No symbol "foo" in current context.
4904 not actually evaluate @var{expression} at the time the @code{condition}
4905 command (or a command that sets a breakpoint with a condition, like
4906 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4908 @item condition @var{bnum}
4909 Remove the condition from breakpoint number @var{bnum}. It becomes
4910 an ordinary unconditional breakpoint.
4913 @cindex ignore count (of breakpoint)
4914 A special case of a breakpoint condition is to stop only when the
4915 breakpoint has been reached a certain number of times. This is so
4916 useful that there is a special way to do it, using the @dfn{ignore
4917 count} of the breakpoint. Every breakpoint has an ignore count, which
4918 is an integer. Most of the time, the ignore count is zero, and
4919 therefore has no effect. But if your program reaches a breakpoint whose
4920 ignore count is positive, then instead of stopping, it just decrements
4921 the ignore count by one and continues. As a result, if the ignore count
4922 value is @var{n}, the breakpoint does not stop the next @var{n} times
4923 your program reaches it.
4927 @item ignore @var{bnum} @var{count}
4928 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4929 The next @var{count} times the breakpoint is reached, your program's
4930 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4933 To make the breakpoint stop the next time it is reached, specify
4936 When you use @code{continue} to resume execution of your program from a
4937 breakpoint, you can specify an ignore count directly as an argument to
4938 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4939 Stepping,,Continuing and Stepping}.
4941 If a breakpoint has a positive ignore count and a condition, the
4942 condition is not checked. Once the ignore count reaches zero,
4943 @value{GDBN} resumes checking the condition.
4945 You could achieve the effect of the ignore count with a condition such
4946 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4947 is decremented each time. @xref{Convenience Vars, ,Convenience
4951 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4954 @node Break Commands
4955 @subsection Breakpoint Command Lists
4957 @cindex breakpoint commands
4958 You can give any breakpoint (or watchpoint or catchpoint) a series of
4959 commands to execute when your program stops due to that breakpoint. For
4960 example, you might want to print the values of certain expressions, or
4961 enable other breakpoints.
4965 @kindex end@r{ (breakpoint commands)}
4966 @item commands @r{[}@var{list}@dots{}@r{]}
4967 @itemx @dots{} @var{command-list} @dots{}
4969 Specify a list of commands for the given breakpoints. The commands
4970 themselves appear on the following lines. Type a line containing just
4971 @code{end} to terminate the commands.
4973 To remove all commands from a breakpoint, type @code{commands} and
4974 follow it immediately with @code{end}; that is, give no commands.
4976 With no argument, @code{commands} refers to the last breakpoint,
4977 watchpoint, or catchpoint set (not to the breakpoint most recently
4978 encountered). If the most recent breakpoints were set with a single
4979 command, then the @code{commands} will apply to all the breakpoints
4980 set by that command. This applies to breakpoints set by
4981 @code{rbreak}, and also applies when a single @code{break} command
4982 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4986 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4987 disabled within a @var{command-list}.
4989 You can use breakpoint commands to start your program up again. Simply
4990 use the @code{continue} command, or @code{step}, or any other command
4991 that resumes execution.
4993 Any other commands in the command list, after a command that resumes
4994 execution, are ignored. This is because any time you resume execution
4995 (even with a simple @code{next} or @code{step}), you may encounter
4996 another breakpoint---which could have its own command list, leading to
4997 ambiguities about which list to execute.
5000 If the first command you specify in a command list is @code{silent}, the
5001 usual message about stopping at a breakpoint is not printed. This may
5002 be desirable for breakpoints that are to print a specific message and
5003 then continue. If none of the remaining commands print anything, you
5004 see no sign that the breakpoint was reached. @code{silent} is
5005 meaningful only at the beginning of a breakpoint command list.
5007 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5008 print precisely controlled output, and are often useful in silent
5009 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5011 For example, here is how you could use breakpoint commands to print the
5012 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5018 printf "x is %d\n",x
5023 One application for breakpoint commands is to compensate for one bug so
5024 you can test for another. Put a breakpoint just after the erroneous line
5025 of code, give it a condition to detect the case in which something
5026 erroneous has been done, and give it commands to assign correct values
5027 to any variables that need them. End with the @code{continue} command
5028 so that your program does not stop, and start with the @code{silent}
5029 command so that no output is produced. Here is an example:
5040 @node Dynamic Printf
5041 @subsection Dynamic Printf
5043 @cindex dynamic printf
5045 The dynamic printf command @code{dprintf} combines a breakpoint with
5046 formatted printing of your program's data to give you the effect of
5047 inserting @code{printf} calls into your program on-the-fly, without
5048 having to recompile it.
5050 In its most basic form, the output goes to the GDB console. However,
5051 you can set the variable @code{dprintf-style} for alternate handling.
5052 For instance, you can ask to format the output by calling your
5053 program's @code{printf} function. This has the advantage that the
5054 characters go to the program's output device, so they can recorded in
5055 redirects to files and so forth.
5057 If you are doing remote debugging with a stub or agent, you can also
5058 ask to have the printf handled by the remote agent. In addition to
5059 ensuring that the output goes to the remote program's device along
5060 with any other output the program might produce, you can also ask that
5061 the dprintf remain active even after disconnecting from the remote
5062 target. Using the stub/agent is also more efficient, as it can do
5063 everything without needing to communicate with @value{GDBN}.
5067 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5068 Whenever execution reaches @var{location}, print the values of one or
5069 more @var{expressions} under the control of the string @var{template}.
5070 To print several values, separate them with commas.
5072 @item set dprintf-style @var{style}
5073 Set the dprintf output to be handled in one of several different
5074 styles enumerated below. A change of style affects all existing
5075 dynamic printfs immediately. (If you need individual control over the
5076 print commands, simply define normal breakpoints with
5077 explicitly-supplied command lists.)
5081 @kindex dprintf-style gdb
5082 Handle the output using the @value{GDBN} @code{printf} command.
5085 @kindex dprintf-style call
5086 Handle the output by calling a function in your program (normally
5090 @kindex dprintf-style agent
5091 Have the remote debugging agent (such as @code{gdbserver}) handle
5092 the output itself. This style is only available for agents that
5093 support running commands on the target.
5096 @item set dprintf-function @var{function}
5097 Set the function to call if the dprintf style is @code{call}. By
5098 default its value is @code{printf}. You may set it to any expression.
5099 that @value{GDBN} can evaluate to a function, as per the @code{call}
5102 @item set dprintf-channel @var{channel}
5103 Set a ``channel'' for dprintf. If set to a non-empty value,
5104 @value{GDBN} will evaluate it as an expression and pass the result as
5105 a first argument to the @code{dprintf-function}, in the manner of
5106 @code{fprintf} and similar functions. Otherwise, the dprintf format
5107 string will be the first argument, in the manner of @code{printf}.
5109 As an example, if you wanted @code{dprintf} output to go to a logfile
5110 that is a standard I/O stream assigned to the variable @code{mylog},
5111 you could do the following:
5114 (gdb) set dprintf-style call
5115 (gdb) set dprintf-function fprintf
5116 (gdb) set dprintf-channel mylog
5117 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5118 Dprintf 1 at 0x123456: file main.c, line 25.
5120 1 dprintf keep y 0x00123456 in main at main.c:25
5121 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5126 Note that the @code{info break} displays the dynamic printf commands
5127 as normal breakpoint commands; you can thus easily see the effect of
5128 the variable settings.
5130 @item set disconnected-dprintf on
5131 @itemx set disconnected-dprintf off
5132 @kindex set disconnected-dprintf
5133 Choose whether @code{dprintf} commands should continue to run if
5134 @value{GDBN} has disconnected from the target. This only applies
5135 if the @code{dprintf-style} is @code{agent}.
5137 @item show disconnected-dprintf off
5138 @kindex show disconnected-dprintf
5139 Show the current choice for disconnected @code{dprintf}.
5143 @value{GDBN} does not check the validity of function and channel,
5144 relying on you to supply values that are meaningful for the contexts
5145 in which they are being used. For instance, the function and channel
5146 may be the values of local variables, but if that is the case, then
5147 all enabled dynamic prints must be at locations within the scope of
5148 those locals. If evaluation fails, @value{GDBN} will report an error.
5150 @node Save Breakpoints
5151 @subsection How to save breakpoints to a file
5153 To save breakpoint definitions to a file use the @w{@code{save
5154 breakpoints}} command.
5157 @kindex save breakpoints
5158 @cindex save breakpoints to a file for future sessions
5159 @item save breakpoints [@var{filename}]
5160 This command saves all current breakpoint definitions together with
5161 their commands and ignore counts, into a file @file{@var{filename}}
5162 suitable for use in a later debugging session. This includes all
5163 types of breakpoints (breakpoints, watchpoints, catchpoints,
5164 tracepoints). To read the saved breakpoint definitions, use the
5165 @code{source} command (@pxref{Command Files}). Note that watchpoints
5166 with expressions involving local variables may fail to be recreated
5167 because it may not be possible to access the context where the
5168 watchpoint is valid anymore. Because the saved breakpoint definitions
5169 are simply a sequence of @value{GDBN} commands that recreate the
5170 breakpoints, you can edit the file in your favorite editing program,
5171 and remove the breakpoint definitions you're not interested in, or
5172 that can no longer be recreated.
5175 @node Static Probe Points
5176 @subsection Static Probe Points
5178 @cindex static probe point, SystemTap
5179 @cindex static probe point, DTrace
5180 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5181 for Statically Defined Tracing, and the probes are designed to have a tiny
5182 runtime code and data footprint, and no dynamic relocations.
5184 Currently, the following types of probes are supported on
5185 ELF-compatible systems:
5189 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5190 @acronym{SDT} probes@footnote{See
5191 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5192 for more information on how to add @code{SystemTap} @acronym{SDT}
5193 probes in your applications.}. @code{SystemTap} probes are usable
5194 from assembly, C and C@t{++} languages@footnote{See
5195 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5196 for a good reference on how the @acronym{SDT} probes are implemented.}.
5198 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5199 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5203 @cindex semaphores on static probe points
5204 Some @code{SystemTap} probes have an associated semaphore variable;
5205 for instance, this happens automatically if you defined your probe
5206 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5207 @value{GDBN} will automatically enable it when you specify a
5208 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5209 breakpoint at a probe's location by some other method (e.g.,
5210 @code{break file:line}), then @value{GDBN} will not automatically set
5211 the semaphore. @code{DTrace} probes do not support semaphores.
5213 You can examine the available static static probes using @code{info
5214 probes}, with optional arguments:
5218 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5219 If given, @var{type} is either @code{stap} for listing
5220 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5221 probes. If omitted all probes are listed regardless of their types.
5223 If given, @var{provider} is a regular expression used to match against provider
5224 names when selecting which probes to list. If omitted, probes by all
5225 probes from all providers are listed.
5227 If given, @var{name} is a regular expression to match against probe names
5228 when selecting which probes to list. If omitted, probe names are not
5229 considered when deciding whether to display them.
5231 If given, @var{objfile} is a regular expression used to select which
5232 object files (executable or shared libraries) to examine. If not
5233 given, all object files are considered.
5235 @item info probes all
5236 List the available static probes, from all types.
5239 @cindex enabling and disabling probes
5240 Some probe points can be enabled and/or disabled. The effect of
5241 enabling or disabling a probe depends on the type of probe being
5242 handled. Some @code{DTrace} probes can be enabled or
5243 disabled, but @code{SystemTap} probes cannot be disabled.
5245 You can enable (or disable) one or more probes using the following
5246 commands, with optional arguments:
5249 @kindex enable probes
5250 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5251 If given, @var{provider} is a regular expression used to match against
5252 provider names when selecting which probes to enable. If omitted,
5253 all probes from all providers are enabled.
5255 If given, @var{name} is a regular expression to match against probe
5256 names when selecting which probes to enable. If omitted, probe names
5257 are not considered when deciding whether to enable them.
5259 If given, @var{objfile} is a regular expression used to select which
5260 object files (executable or shared libraries) to examine. If not
5261 given, all object files are considered.
5263 @kindex disable probes
5264 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5265 See the @code{enable probes} command above for a description of the
5266 optional arguments accepted by this command.
5269 @vindex $_probe_arg@r{, convenience variable}
5270 A probe may specify up to twelve arguments. These are available at the
5271 point at which the probe is defined---that is, when the current PC is
5272 at the probe's location. The arguments are available using the
5273 convenience variables (@pxref{Convenience Vars})
5274 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5275 probes each probe argument is an integer of the appropriate size;
5276 types are not preserved. In @code{DTrace} probes types are preserved
5277 provided that they are recognized as such by @value{GDBN}; otherwise
5278 the value of the probe argument will be a long integer. The
5279 convenience variable @code{$_probe_argc} holds the number of arguments
5280 at the current probe point.
5282 These variables are always available, but attempts to access them at
5283 any location other than a probe point will cause @value{GDBN} to give
5287 @c @ifclear BARETARGET
5288 @node Error in Breakpoints
5289 @subsection ``Cannot insert breakpoints''
5291 If you request too many active hardware-assisted breakpoints and
5292 watchpoints, you will see this error message:
5294 @c FIXME: the precise wording of this message may change; the relevant
5295 @c source change is not committed yet (Sep 3, 1999).
5297 Stopped; cannot insert breakpoints.
5298 You may have requested too many hardware breakpoints and watchpoints.
5302 This message is printed when you attempt to resume the program, since
5303 only then @value{GDBN} knows exactly how many hardware breakpoints and
5304 watchpoints it needs to insert.
5306 When this message is printed, you need to disable or remove some of the
5307 hardware-assisted breakpoints and watchpoints, and then continue.
5309 @node Breakpoint-related Warnings
5310 @subsection ``Breakpoint address adjusted...''
5311 @cindex breakpoint address adjusted
5313 Some processor architectures place constraints on the addresses at
5314 which breakpoints may be placed. For architectures thus constrained,
5315 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5316 with the constraints dictated by the architecture.
5318 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5319 a VLIW architecture in which a number of RISC-like instructions may be
5320 bundled together for parallel execution. The FR-V architecture
5321 constrains the location of a breakpoint instruction within such a
5322 bundle to the instruction with the lowest address. @value{GDBN}
5323 honors this constraint by adjusting a breakpoint's address to the
5324 first in the bundle.
5326 It is not uncommon for optimized code to have bundles which contain
5327 instructions from different source statements, thus it may happen that
5328 a breakpoint's address will be adjusted from one source statement to
5329 another. Since this adjustment may significantly alter @value{GDBN}'s
5330 breakpoint related behavior from what the user expects, a warning is
5331 printed when the breakpoint is first set and also when the breakpoint
5334 A warning like the one below is printed when setting a breakpoint
5335 that's been subject to address adjustment:
5338 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5341 Such warnings are printed both for user settable and @value{GDBN}'s
5342 internal breakpoints. If you see one of these warnings, you should
5343 verify that a breakpoint set at the adjusted address will have the
5344 desired affect. If not, the breakpoint in question may be removed and
5345 other breakpoints may be set which will have the desired behavior.
5346 E.g., it may be sufficient to place the breakpoint at a later
5347 instruction. A conditional breakpoint may also be useful in some
5348 cases to prevent the breakpoint from triggering too often.
5350 @value{GDBN} will also issue a warning when stopping at one of these
5351 adjusted breakpoints:
5354 warning: Breakpoint 1 address previously adjusted from 0x00010414
5358 When this warning is encountered, it may be too late to take remedial
5359 action except in cases where the breakpoint is hit earlier or more
5360 frequently than expected.
5362 @node Continuing and Stepping
5363 @section Continuing and Stepping
5367 @cindex resuming execution
5368 @dfn{Continuing} means resuming program execution until your program
5369 completes normally. In contrast, @dfn{stepping} means executing just
5370 one more ``step'' of your program, where ``step'' may mean either one
5371 line of source code, or one machine instruction (depending on what
5372 particular command you use). Either when continuing or when stepping,
5373 your program may stop even sooner, due to a breakpoint or a signal. (If
5374 it stops due to a signal, you may want to use @code{handle}, or use
5375 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5376 or you may step into the signal's handler (@pxref{stepping and signal
5381 @kindex c @r{(@code{continue})}
5382 @kindex fg @r{(resume foreground execution)}
5383 @item continue @r{[}@var{ignore-count}@r{]}
5384 @itemx c @r{[}@var{ignore-count}@r{]}
5385 @itemx fg @r{[}@var{ignore-count}@r{]}
5386 Resume program execution, at the address where your program last stopped;
5387 any breakpoints set at that address are bypassed. The optional argument
5388 @var{ignore-count} allows you to specify a further number of times to
5389 ignore a breakpoint at this location; its effect is like that of
5390 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5392 The argument @var{ignore-count} is meaningful only when your program
5393 stopped due to a breakpoint. At other times, the argument to
5394 @code{continue} is ignored.
5396 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5397 debugged program is deemed to be the foreground program) are provided
5398 purely for convenience, and have exactly the same behavior as
5402 To resume execution at a different place, you can use @code{return}
5403 (@pxref{Returning, ,Returning from a Function}) to go back to the
5404 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5405 Different Address}) to go to an arbitrary location in your program.
5407 A typical technique for using stepping is to set a breakpoint
5408 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5409 beginning of the function or the section of your program where a problem
5410 is believed to lie, run your program until it stops at that breakpoint,
5411 and then step through the suspect area, examining the variables that are
5412 interesting, until you see the problem happen.
5416 @kindex s @r{(@code{step})}
5418 Continue running your program until control reaches a different source
5419 line, then stop it and return control to @value{GDBN}. This command is
5420 abbreviated @code{s}.
5423 @c "without debugging information" is imprecise; actually "without line
5424 @c numbers in the debugging information". (gcc -g1 has debugging info but
5425 @c not line numbers). But it seems complex to try to make that
5426 @c distinction here.
5427 @emph{Warning:} If you use the @code{step} command while control is
5428 within a function that was compiled without debugging information,
5429 execution proceeds until control reaches a function that does have
5430 debugging information. Likewise, it will not step into a function which
5431 is compiled without debugging information. To step through functions
5432 without debugging information, use the @code{stepi} command, described
5436 The @code{step} command only stops at the first instruction of a source
5437 line. This prevents the multiple stops that could otherwise occur in
5438 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5439 to stop if a function that has debugging information is called within
5440 the line. In other words, @code{step} @emph{steps inside} any functions
5441 called within the line.
5443 Also, the @code{step} command only enters a function if there is line
5444 number information for the function. Otherwise it acts like the
5445 @code{next} command. This avoids problems when using @code{cc -gl}
5446 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5447 was any debugging information about the routine.
5449 @item step @var{count}
5450 Continue running as in @code{step}, but do so @var{count} times. If a
5451 breakpoint is reached, or a signal not related to stepping occurs before
5452 @var{count} steps, stepping stops right away.
5455 @kindex n @r{(@code{next})}
5456 @item next @r{[}@var{count}@r{]}
5457 Continue to the next source line in the current (innermost) stack frame.
5458 This is similar to @code{step}, but function calls that appear within
5459 the line of code are executed without stopping. Execution stops when
5460 control reaches a different line of code at the original stack level
5461 that was executing when you gave the @code{next} command. This command
5462 is abbreviated @code{n}.
5464 An argument @var{count} is a repeat count, as for @code{step}.
5467 @c FIX ME!! Do we delete this, or is there a way it fits in with
5468 @c the following paragraph? --- Vctoria
5470 @c @code{next} within a function that lacks debugging information acts like
5471 @c @code{step}, but any function calls appearing within the code of the
5472 @c function are executed without stopping.
5474 The @code{next} command only stops at the first instruction of a
5475 source line. This prevents multiple stops that could otherwise occur in
5476 @code{switch} statements, @code{for} loops, etc.
5478 @kindex set step-mode
5480 @cindex functions without line info, and stepping
5481 @cindex stepping into functions with no line info
5482 @itemx set step-mode on
5483 The @code{set step-mode on} command causes the @code{step} command to
5484 stop at the first instruction of a function which contains no debug line
5485 information rather than stepping over it.
5487 This is useful in cases where you may be interested in inspecting the
5488 machine instructions of a function which has no symbolic info and do not
5489 want @value{GDBN} to automatically skip over this function.
5491 @item set step-mode off
5492 Causes the @code{step} command to step over any functions which contains no
5493 debug information. This is the default.
5495 @item show step-mode
5496 Show whether @value{GDBN} will stop in or step over functions without
5497 source line debug information.
5500 @kindex fin @r{(@code{finish})}
5502 Continue running until just after function in the selected stack frame
5503 returns. Print the returned value (if any). This command can be
5504 abbreviated as @code{fin}.
5506 Contrast this with the @code{return} command (@pxref{Returning,
5507 ,Returning from a Function}).
5510 @kindex u @r{(@code{until})}
5511 @cindex run until specified location
5514 Continue running until a source line past the current line, in the
5515 current stack frame, is reached. This command is used to avoid single
5516 stepping through a loop more than once. It is like the @code{next}
5517 command, except that when @code{until} encounters a jump, it
5518 automatically continues execution until the program counter is greater
5519 than the address of the jump.
5521 This means that when you reach the end of a loop after single stepping
5522 though it, @code{until} makes your program continue execution until it
5523 exits the loop. In contrast, a @code{next} command at the end of a loop
5524 simply steps back to the beginning of the loop, which forces you to step
5525 through the next iteration.
5527 @code{until} always stops your program if it attempts to exit the current
5530 @code{until} may produce somewhat counterintuitive results if the order
5531 of machine code does not match the order of the source lines. For
5532 example, in the following excerpt from a debugging session, the @code{f}
5533 (@code{frame}) command shows that execution is stopped at line
5534 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5538 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5540 (@value{GDBP}) until
5541 195 for ( ; argc > 0; NEXTARG) @{
5544 This happened because, for execution efficiency, the compiler had
5545 generated code for the loop closure test at the end, rather than the
5546 start, of the loop---even though the test in a C @code{for}-loop is
5547 written before the body of the loop. The @code{until} command appeared
5548 to step back to the beginning of the loop when it advanced to this
5549 expression; however, it has not really gone to an earlier
5550 statement---not in terms of the actual machine code.
5552 @code{until} with no argument works by means of single
5553 instruction stepping, and hence is slower than @code{until} with an
5556 @item until @var{location}
5557 @itemx u @var{location}
5558 Continue running your program until either the specified @var{location} is
5559 reached, or the current stack frame returns. The location is any of
5560 the forms described in @ref{Specify Location}.
5561 This form of the command uses temporary breakpoints, and
5562 hence is quicker than @code{until} without an argument. The specified
5563 location is actually reached only if it is in the current frame. This
5564 implies that @code{until} can be used to skip over recursive function
5565 invocations. For instance in the code below, if the current location is
5566 line @code{96}, issuing @code{until 99} will execute the program up to
5567 line @code{99} in the same invocation of factorial, i.e., after the inner
5568 invocations have returned.
5571 94 int factorial (int value)
5573 96 if (value > 1) @{
5574 97 value *= factorial (value - 1);
5581 @kindex advance @var{location}
5582 @item advance @var{location}
5583 Continue running the program up to the given @var{location}. An argument is
5584 required, which should be of one of the forms described in
5585 @ref{Specify Location}.
5586 Execution will also stop upon exit from the current stack
5587 frame. This command is similar to @code{until}, but @code{advance} will
5588 not skip over recursive function calls, and the target location doesn't
5589 have to be in the same frame as the current one.
5593 @kindex si @r{(@code{stepi})}
5595 @itemx stepi @var{arg}
5597 Execute one machine instruction, then stop and return to the debugger.
5599 It is often useful to do @samp{display/i $pc} when stepping by machine
5600 instructions. This makes @value{GDBN} automatically display the next
5601 instruction to be executed, each time your program stops. @xref{Auto
5602 Display,, Automatic Display}.
5604 An argument is a repeat count, as in @code{step}.
5608 @kindex ni @r{(@code{nexti})}
5610 @itemx nexti @var{arg}
5612 Execute one machine instruction, but if it is a function call,
5613 proceed until the function returns.
5615 An argument is a repeat count, as in @code{next}.
5619 @anchor{range stepping}
5620 @cindex range stepping
5621 @cindex target-assisted range stepping
5622 By default, and if available, @value{GDBN} makes use of
5623 target-assisted @dfn{range stepping}. In other words, whenever you
5624 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5625 tells the target to step the corresponding range of instruction
5626 addresses instead of issuing multiple single-steps. This speeds up
5627 line stepping, particularly for remote targets. Ideally, there should
5628 be no reason you would want to turn range stepping off. However, it's
5629 possible that a bug in the debug info, a bug in the remote stub (for
5630 remote targets), or even a bug in @value{GDBN} could make line
5631 stepping behave incorrectly when target-assisted range stepping is
5632 enabled. You can use the following command to turn off range stepping
5636 @kindex set range-stepping
5637 @kindex show range-stepping
5638 @item set range-stepping
5639 @itemx show range-stepping
5640 Control whether range stepping is enabled.
5642 If @code{on}, and the target supports it, @value{GDBN} tells the
5643 target to step a range of addresses itself, instead of issuing
5644 multiple single-steps. If @code{off}, @value{GDBN} always issues
5645 single-steps, even if range stepping is supported by the target. The
5646 default is @code{on}.
5650 @node Skipping Over Functions and Files
5651 @section Skipping Over Functions and Files
5652 @cindex skipping over functions and files
5654 The program you are debugging may contain some functions which are
5655 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5656 skip a function, all functions in a file or a particular function in
5657 a particular file when stepping.
5659 For example, consider the following C function:
5670 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5671 are not interested in stepping through @code{boring}. If you run @code{step}
5672 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5673 step over both @code{foo} and @code{boring}!
5675 One solution is to @code{step} into @code{boring} and use the @code{finish}
5676 command to immediately exit it. But this can become tedious if @code{boring}
5677 is called from many places.
5679 A more flexible solution is to execute @kbd{skip boring}. This instructs
5680 @value{GDBN} never to step into @code{boring}. Now when you execute
5681 @code{step} at line 103, you'll step over @code{boring} and directly into
5684 Functions may be skipped by providing either a function name, linespec
5685 (@pxref{Specify Location}), regular expression that matches the function's
5686 name, file name or a @code{glob}-style pattern that matches the file name.
5688 On Posix systems the form of the regular expression is
5689 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5690 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5691 expression is whatever is provided by the @code{regcomp} function of
5692 the underlying system.
5693 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5694 description of @code{glob}-style patterns.
5698 @item skip @r{[}@var{options}@r{]}
5699 The basic form of the @code{skip} command takes zero or more options
5700 that specify what to skip.
5701 The @var{options} argument is any useful combination of the following:
5704 @item -file @var{file}
5705 @itemx -fi @var{file}
5706 Functions in @var{file} will be skipped over when stepping.
5708 @item -gfile @var{file-glob-pattern}
5709 @itemx -gfi @var{file-glob-pattern}
5710 @cindex skipping over files via glob-style patterns
5711 Functions in files matching @var{file-glob-pattern} will be skipped
5715 (gdb) skip -gfi utils/*.c
5718 @item -function @var{linespec}
5719 @itemx -fu @var{linespec}
5720 Functions named by @var{linespec} or the function containing the line
5721 named by @var{linespec} will be skipped over when stepping.
5722 @xref{Specify Location}.
5724 @item -rfunction @var{regexp}
5725 @itemx -rfu @var{regexp}
5726 @cindex skipping over functions via regular expressions
5727 Functions whose name matches @var{regexp} will be skipped over when stepping.
5729 This form is useful for complex function names.
5730 For example, there is generally no need to step into C@t{++} @code{std::string}
5731 constructors or destructors. Plus with C@t{++} templates it can be hard to
5732 write out the full name of the function, and often it doesn't matter what
5733 the template arguments are. Specifying the function to be skipped as a
5734 regular expression makes this easier.
5737 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5740 If you want to skip every templated C@t{++} constructor and destructor
5741 in the @code{std} namespace you can do:
5744 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5748 If no options are specified, the function you're currently debugging
5751 @kindex skip function
5752 @item skip function @r{[}@var{linespec}@r{]}
5753 After running this command, the function named by @var{linespec} or the
5754 function containing the line named by @var{linespec} will be skipped over when
5755 stepping. @xref{Specify Location}.
5757 If you do not specify @var{linespec}, the function you're currently debugging
5760 (If you have a function called @code{file} that you want to skip, use
5761 @kbd{skip function file}.)
5764 @item skip file @r{[}@var{filename}@r{]}
5765 After running this command, any function whose source lives in @var{filename}
5766 will be skipped over when stepping.
5769 (gdb) skip file boring.c
5770 File boring.c will be skipped when stepping.
5773 If you do not specify @var{filename}, functions whose source lives in the file
5774 you're currently debugging will be skipped.
5777 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5778 These are the commands for managing your list of skips:
5782 @item info skip @r{[}@var{range}@r{]}
5783 Print details about the specified skip(s). If @var{range} is not specified,
5784 print a table with details about all functions and files marked for skipping.
5785 @code{info skip} prints the following information about each skip:
5789 A number identifying this skip.
5790 @item Enabled or Disabled
5791 Enabled skips are marked with @samp{y}.
5792 Disabled skips are marked with @samp{n}.
5794 If the file name is a @samp{glob} pattern this is @samp{y}.
5795 Otherwise it is @samp{n}.
5797 The name or @samp{glob} pattern of the file to be skipped.
5798 If no file is specified this is @samp{<none>}.
5800 If the function name is a @samp{regular expression} this is @samp{y}.
5801 Otherwise it is @samp{n}.
5803 The name or regular expression of the function to skip.
5804 If no function is specified this is @samp{<none>}.
5808 @item skip delete @r{[}@var{range}@r{]}
5809 Delete the specified skip(s). If @var{range} is not specified, delete all
5813 @item skip enable @r{[}@var{range}@r{]}
5814 Enable the specified skip(s). If @var{range} is not specified, enable all
5817 @kindex skip disable
5818 @item skip disable @r{[}@var{range}@r{]}
5819 Disable the specified skip(s). If @var{range} is not specified, disable all
5828 A signal is an asynchronous event that can happen in a program. The
5829 operating system defines the possible kinds of signals, and gives each
5830 kind a name and a number. For example, in Unix @code{SIGINT} is the
5831 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5832 @code{SIGSEGV} is the signal a program gets from referencing a place in
5833 memory far away from all the areas in use; @code{SIGALRM} occurs when
5834 the alarm clock timer goes off (which happens only if your program has
5835 requested an alarm).
5837 @cindex fatal signals
5838 Some signals, including @code{SIGALRM}, are a normal part of the
5839 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5840 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5841 program has not specified in advance some other way to handle the signal.
5842 @code{SIGINT} does not indicate an error in your program, but it is normally
5843 fatal so it can carry out the purpose of the interrupt: to kill the program.
5845 @value{GDBN} has the ability to detect any occurrence of a signal in your
5846 program. You can tell @value{GDBN} in advance what to do for each kind of
5849 @cindex handling signals
5850 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5851 @code{SIGALRM} be silently passed to your program
5852 (so as not to interfere with their role in the program's functioning)
5853 but to stop your program immediately whenever an error signal happens.
5854 You can change these settings with the @code{handle} command.
5857 @kindex info signals
5861 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5862 handle each one. You can use this to see the signal numbers of all
5863 the defined types of signals.
5865 @item info signals @var{sig}
5866 Similar, but print information only about the specified signal number.
5868 @code{info handle} is an alias for @code{info signals}.
5870 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5871 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5872 for details about this command.
5875 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5876 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5877 can be the number of a signal or its name (with or without the
5878 @samp{SIG} at the beginning); a list of signal numbers of the form
5879 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5880 known signals. Optional arguments @var{keywords}, described below,
5881 say what change to make.
5885 The keywords allowed by the @code{handle} command can be abbreviated.
5886 Their full names are:
5890 @value{GDBN} should not stop your program when this signal happens. It may
5891 still print a message telling you that the signal has come in.
5894 @value{GDBN} should stop your program when this signal happens. This implies
5895 the @code{print} keyword as well.
5898 @value{GDBN} should print a message when this signal happens.
5901 @value{GDBN} should not mention the occurrence of the signal at all. This
5902 implies the @code{nostop} keyword as well.
5906 @value{GDBN} should allow your program to see this signal; your program
5907 can handle the signal, or else it may terminate if the signal is fatal
5908 and not handled. @code{pass} and @code{noignore} are synonyms.
5912 @value{GDBN} should not allow your program to see this signal.
5913 @code{nopass} and @code{ignore} are synonyms.
5917 When a signal stops your program, the signal is not visible to the
5919 continue. Your program sees the signal then, if @code{pass} is in
5920 effect for the signal in question @emph{at that time}. In other words,
5921 after @value{GDBN} reports a signal, you can use the @code{handle}
5922 command with @code{pass} or @code{nopass} to control whether your
5923 program sees that signal when you continue.
5925 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5926 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5927 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5930 You can also use the @code{signal} command to prevent your program from
5931 seeing a signal, or cause it to see a signal it normally would not see,
5932 or to give it any signal at any time. For example, if your program stopped
5933 due to some sort of memory reference error, you might store correct
5934 values into the erroneous variables and continue, hoping to see more
5935 execution; but your program would probably terminate immediately as
5936 a result of the fatal signal once it saw the signal. To prevent this,
5937 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5940 @cindex stepping and signal handlers
5941 @anchor{stepping and signal handlers}
5943 @value{GDBN} optimizes for stepping the mainline code. If a signal
5944 that has @code{handle nostop} and @code{handle pass} set arrives while
5945 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5946 in progress, @value{GDBN} lets the signal handler run and then resumes
5947 stepping the mainline code once the signal handler returns. In other
5948 words, @value{GDBN} steps over the signal handler. This prevents
5949 signals that you've specified as not interesting (with @code{handle
5950 nostop}) from changing the focus of debugging unexpectedly. Note that
5951 the signal handler itself may still hit a breakpoint, stop for another
5952 signal that has @code{handle stop} in effect, or for any other event
5953 that normally results in stopping the stepping command sooner. Also
5954 note that @value{GDBN} still informs you that the program received a
5955 signal if @code{handle print} is set.
5957 @anchor{stepping into signal handlers}
5959 If you set @code{handle pass} for a signal, and your program sets up a
5960 handler for it, then issuing a stepping command, such as @code{step}
5961 or @code{stepi}, when your program is stopped due to the signal will
5962 step @emph{into} the signal handler (if the target supports that).
5964 Likewise, if you use the @code{queue-signal} command to queue a signal
5965 to be delivered to the current thread when execution of the thread
5966 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5967 stepping command will step into the signal handler.
5969 Here's an example, using @code{stepi} to step to the first instruction
5970 of @code{SIGUSR1}'s handler:
5973 (@value{GDBP}) handle SIGUSR1
5974 Signal Stop Print Pass to program Description
5975 SIGUSR1 Yes Yes Yes User defined signal 1
5979 Program received signal SIGUSR1, User defined signal 1.
5980 main () sigusr1.c:28
5983 sigusr1_handler () at sigusr1.c:9
5987 The same, but using @code{queue-signal} instead of waiting for the
5988 program to receive the signal first:
5993 (@value{GDBP}) queue-signal SIGUSR1
5995 sigusr1_handler () at sigusr1.c:9
6000 @cindex extra signal information
6001 @anchor{extra signal information}
6003 On some targets, @value{GDBN} can inspect extra signal information
6004 associated with the intercepted signal, before it is actually
6005 delivered to the program being debugged. This information is exported
6006 by the convenience variable @code{$_siginfo}, and consists of data
6007 that is passed by the kernel to the signal handler at the time of the
6008 receipt of a signal. The data type of the information itself is
6009 target dependent. You can see the data type using the @code{ptype
6010 $_siginfo} command. On Unix systems, it typically corresponds to the
6011 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6014 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6015 referenced address that raised a segmentation fault.
6019 (@value{GDBP}) continue
6020 Program received signal SIGSEGV, Segmentation fault.
6021 0x0000000000400766 in main ()
6023 (@value{GDBP}) ptype $_siginfo
6030 struct @{...@} _kill;
6031 struct @{...@} _timer;
6033 struct @{...@} _sigchld;
6034 struct @{...@} _sigfault;
6035 struct @{...@} _sigpoll;
6038 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6042 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6043 $1 = (void *) 0x7ffff7ff7000
6047 Depending on target support, @code{$_siginfo} may also be writable.
6049 @cindex Intel MPX boundary violations
6050 @cindex boundary violations, Intel MPX
6051 On some targets, a @code{SIGSEGV} can be caused by a boundary
6052 violation, i.e., accessing an address outside of the allowed range.
6053 In those cases @value{GDBN} may displays additional information,
6054 depending on how @value{GDBN} has been told to handle the signal.
6055 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6056 kind: "Upper" or "Lower", the memory address accessed and the
6057 bounds, while with @code{handle nostop SIGSEGV} no additional
6058 information is displayed.
6060 The usual output of a segfault is:
6062 Program received signal SIGSEGV, Segmentation fault
6063 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6064 68 value = *(p + len);
6067 While a bound violation is presented as:
6069 Program received signal SIGSEGV, Segmentation fault
6070 Upper bound violation while accessing address 0x7fffffffc3b3
6071 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6072 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6073 68 value = *(p + len);
6077 @section Stopping and Starting Multi-thread Programs
6079 @cindex stopped threads
6080 @cindex threads, stopped
6082 @cindex continuing threads
6083 @cindex threads, continuing
6085 @value{GDBN} supports debugging programs with multiple threads
6086 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6087 are two modes of controlling execution of your program within the
6088 debugger. In the default mode, referred to as @dfn{all-stop mode},
6089 when any thread in your program stops (for example, at a breakpoint
6090 or while being stepped), all other threads in the program are also stopped by
6091 @value{GDBN}. On some targets, @value{GDBN} also supports
6092 @dfn{non-stop mode}, in which other threads can continue to run freely while
6093 you examine the stopped thread in the debugger.
6096 * All-Stop Mode:: All threads stop when GDB takes control
6097 * Non-Stop Mode:: Other threads continue to execute
6098 * Background Execution:: Running your program asynchronously
6099 * Thread-Specific Breakpoints:: Controlling breakpoints
6100 * Interrupted System Calls:: GDB may interfere with system calls
6101 * Observer Mode:: GDB does not alter program behavior
6105 @subsection All-Stop Mode
6107 @cindex all-stop mode
6109 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6110 @emph{all} threads of execution stop, not just the current thread. This
6111 allows you to examine the overall state of the program, including
6112 switching between threads, without worrying that things may change
6115 Conversely, whenever you restart the program, @emph{all} threads start
6116 executing. @emph{This is true even when single-stepping} with commands
6117 like @code{step} or @code{next}.
6119 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6120 Since thread scheduling is up to your debugging target's operating
6121 system (not controlled by @value{GDBN}), other threads may
6122 execute more than one statement while the current thread completes a
6123 single step. Moreover, in general other threads stop in the middle of a
6124 statement, rather than at a clean statement boundary, when the program
6127 You might even find your program stopped in another thread after
6128 continuing or even single-stepping. This happens whenever some other
6129 thread runs into a breakpoint, a signal, or an exception before the
6130 first thread completes whatever you requested.
6132 @cindex automatic thread selection
6133 @cindex switching threads automatically
6134 @cindex threads, automatic switching
6135 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6136 signal, it automatically selects the thread where that breakpoint or
6137 signal happened. @value{GDBN} alerts you to the context switch with a
6138 message such as @samp{[Switching to Thread @var{n}]} to identify the
6141 On some OSes, you can modify @value{GDBN}'s default behavior by
6142 locking the OS scheduler to allow only a single thread to run.
6145 @item set scheduler-locking @var{mode}
6146 @cindex scheduler locking mode
6147 @cindex lock scheduler
6148 Set the scheduler locking mode. It applies to normal execution,
6149 record mode, and replay mode. If it is @code{off}, then there is no
6150 locking and any thread may run at any time. If @code{on}, then only
6151 the current thread may run when the inferior is resumed. The
6152 @code{step} mode optimizes for single-stepping; it prevents other
6153 threads from preempting the current thread while you are stepping, so
6154 that the focus of debugging does not change unexpectedly. Other
6155 threads never get a chance to run when you step, and they are
6156 completely free to run when you use commands like @samp{continue},
6157 @samp{until}, or @samp{finish}. However, unless another thread hits a
6158 breakpoint during its timeslice, @value{GDBN} does not change the
6159 current thread away from the thread that you are debugging. The
6160 @code{replay} mode behaves like @code{off} in record mode and like
6161 @code{on} in replay mode.
6163 @item show scheduler-locking
6164 Display the current scheduler locking mode.
6167 @cindex resume threads of multiple processes simultaneously
6168 By default, when you issue one of the execution commands such as
6169 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6170 threads of the current inferior to run. For example, if @value{GDBN}
6171 is attached to two inferiors, each with two threads, the
6172 @code{continue} command resumes only the two threads of the current
6173 inferior. This is useful, for example, when you debug a program that
6174 forks and you want to hold the parent stopped (so that, for instance,
6175 it doesn't run to exit), while you debug the child. In other
6176 situations, you may not be interested in inspecting the current state
6177 of any of the processes @value{GDBN} is attached to, and you may want
6178 to resume them all until some breakpoint is hit. In the latter case,
6179 you can instruct @value{GDBN} to allow all threads of all the
6180 inferiors to run with the @w{@code{set schedule-multiple}} command.
6183 @kindex set schedule-multiple
6184 @item set schedule-multiple
6185 Set the mode for allowing threads of multiple processes to be resumed
6186 when an execution command is issued. When @code{on}, all threads of
6187 all processes are allowed to run. When @code{off}, only the threads
6188 of the current process are resumed. The default is @code{off}. The
6189 @code{scheduler-locking} mode takes precedence when set to @code{on},
6190 or while you are stepping and set to @code{step}.
6192 @item show schedule-multiple
6193 Display the current mode for resuming the execution of threads of
6198 @subsection Non-Stop Mode
6200 @cindex non-stop mode
6202 @c This section is really only a place-holder, and needs to be expanded
6203 @c with more details.
6205 For some multi-threaded targets, @value{GDBN} supports an optional
6206 mode of operation in which you can examine stopped program threads in
6207 the debugger while other threads continue to execute freely. This
6208 minimizes intrusion when debugging live systems, such as programs
6209 where some threads have real-time constraints or must continue to
6210 respond to external events. This is referred to as @dfn{non-stop} mode.
6212 In non-stop mode, when a thread stops to report a debugging event,
6213 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6214 threads as well, in contrast to the all-stop mode behavior. Additionally,
6215 execution commands such as @code{continue} and @code{step} apply by default
6216 only to the current thread in non-stop mode, rather than all threads as
6217 in all-stop mode. This allows you to control threads explicitly in
6218 ways that are not possible in all-stop mode --- for example, stepping
6219 one thread while allowing others to run freely, stepping
6220 one thread while holding all others stopped, or stepping several threads
6221 independently and simultaneously.
6223 To enter non-stop mode, use this sequence of commands before you run
6224 or attach to your program:
6227 # If using the CLI, pagination breaks non-stop.
6230 # Finally, turn it on!
6234 You can use these commands to manipulate the non-stop mode setting:
6237 @kindex set non-stop
6238 @item set non-stop on
6239 Enable selection of non-stop mode.
6240 @item set non-stop off
6241 Disable selection of non-stop mode.
6242 @kindex show non-stop
6244 Show the current non-stop enablement setting.
6247 Note these commands only reflect whether non-stop mode is enabled,
6248 not whether the currently-executing program is being run in non-stop mode.
6249 In particular, the @code{set non-stop} preference is only consulted when
6250 @value{GDBN} starts or connects to the target program, and it is generally
6251 not possible to switch modes once debugging has started. Furthermore,
6252 since not all targets support non-stop mode, even when you have enabled
6253 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6256 In non-stop mode, all execution commands apply only to the current thread
6257 by default. That is, @code{continue} only continues one thread.
6258 To continue all threads, issue @code{continue -a} or @code{c -a}.
6260 You can use @value{GDBN}'s background execution commands
6261 (@pxref{Background Execution}) to run some threads in the background
6262 while you continue to examine or step others from @value{GDBN}.
6263 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6264 always executed asynchronously in non-stop mode.
6266 Suspending execution is done with the @code{interrupt} command when
6267 running in the background, or @kbd{Ctrl-c} during foreground execution.
6268 In all-stop mode, this stops the whole process;
6269 but in non-stop mode the interrupt applies only to the current thread.
6270 To stop the whole program, use @code{interrupt -a}.
6272 Other execution commands do not currently support the @code{-a} option.
6274 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6275 that thread current, as it does in all-stop mode. This is because the
6276 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6277 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6278 changed to a different thread just as you entered a command to operate on the
6279 previously current thread.
6281 @node Background Execution
6282 @subsection Background Execution
6284 @cindex foreground execution
6285 @cindex background execution
6286 @cindex asynchronous execution
6287 @cindex execution, foreground, background and asynchronous
6289 @value{GDBN}'s execution commands have two variants: the normal
6290 foreground (synchronous) behavior, and a background
6291 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6292 the program to report that some thread has stopped before prompting for
6293 another command. In background execution, @value{GDBN} immediately gives
6294 a command prompt so that you can issue other commands while your program runs.
6296 If the target doesn't support async mode, @value{GDBN} issues an error
6297 message if you attempt to use the background execution commands.
6299 To specify background execution, add a @code{&} to the command. For example,
6300 the background form of the @code{continue} command is @code{continue&}, or
6301 just @code{c&}. The execution commands that accept background execution
6307 @xref{Starting, , Starting your Program}.
6311 @xref{Attach, , Debugging an Already-running Process}.
6315 @xref{Continuing and Stepping, step}.
6319 @xref{Continuing and Stepping, stepi}.
6323 @xref{Continuing and Stepping, next}.
6327 @xref{Continuing and Stepping, nexti}.
6331 @xref{Continuing and Stepping, continue}.
6335 @xref{Continuing and Stepping, finish}.
6339 @xref{Continuing and Stepping, until}.
6343 Background execution is especially useful in conjunction with non-stop
6344 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6345 However, you can also use these commands in the normal all-stop mode with
6346 the restriction that you cannot issue another execution command until the
6347 previous one finishes. Examples of commands that are valid in all-stop
6348 mode while the program is running include @code{help} and @code{info break}.
6350 You can interrupt your program while it is running in the background by
6351 using the @code{interrupt} command.
6358 Suspend execution of the running program. In all-stop mode,
6359 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6360 only the current thread. To stop the whole program in non-stop mode,
6361 use @code{interrupt -a}.
6364 @node Thread-Specific Breakpoints
6365 @subsection Thread-Specific Breakpoints
6367 When your program has multiple threads (@pxref{Threads,, Debugging
6368 Programs with Multiple Threads}), you can choose whether to set
6369 breakpoints on all threads, or on a particular thread.
6372 @cindex breakpoints and threads
6373 @cindex thread breakpoints
6374 @kindex break @dots{} thread @var{thread-id}
6375 @item break @var{location} thread @var{thread-id}
6376 @itemx break @var{location} thread @var{thread-id} if @dots{}
6377 @var{location} specifies source lines; there are several ways of
6378 writing them (@pxref{Specify Location}), but the effect is always to
6379 specify some source line.
6381 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6382 to specify that you only want @value{GDBN} to stop the program when a
6383 particular thread reaches this breakpoint. The @var{thread-id} specifier
6384 is one of the thread identifiers assigned by @value{GDBN}, shown
6385 in the first column of the @samp{info threads} display.
6387 If you do not specify @samp{thread @var{thread-id}} when you set a
6388 breakpoint, the breakpoint applies to @emph{all} threads of your
6391 You can use the @code{thread} qualifier on conditional breakpoints as
6392 well; in this case, place @samp{thread @var{thread-id}} before or
6393 after the breakpoint condition, like this:
6396 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6401 Thread-specific breakpoints are automatically deleted when
6402 @value{GDBN} detects the corresponding thread is no longer in the
6403 thread list. For example:
6407 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6410 There are several ways for a thread to disappear, such as a regular
6411 thread exit, but also when you detach from the process with the
6412 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6413 Process}), or if @value{GDBN} loses the remote connection
6414 (@pxref{Remote Debugging}), etc. Note that with some targets,
6415 @value{GDBN} is only able to detect a thread has exited when the user
6416 explictly asks for the thread list with the @code{info threads}
6419 @node Interrupted System Calls
6420 @subsection Interrupted System Calls
6422 @cindex thread breakpoints and system calls
6423 @cindex system calls and thread breakpoints
6424 @cindex premature return from system calls
6425 There is an unfortunate side effect when using @value{GDBN} to debug
6426 multi-threaded programs. If one thread stops for a
6427 breakpoint, or for some other reason, and another thread is blocked in a
6428 system call, then the system call may return prematurely. This is a
6429 consequence of the interaction between multiple threads and the signals
6430 that @value{GDBN} uses to implement breakpoints and other events that
6433 To handle this problem, your program should check the return value of
6434 each system call and react appropriately. This is good programming
6437 For example, do not write code like this:
6443 The call to @code{sleep} will return early if a different thread stops
6444 at a breakpoint or for some other reason.
6446 Instead, write this:
6451 unslept = sleep (unslept);
6454 A system call is allowed to return early, so the system is still
6455 conforming to its specification. But @value{GDBN} does cause your
6456 multi-threaded program to behave differently than it would without
6459 Also, @value{GDBN} uses internal breakpoints in the thread library to
6460 monitor certain events such as thread creation and thread destruction.
6461 When such an event happens, a system call in another thread may return
6462 prematurely, even though your program does not appear to stop.
6465 @subsection Observer Mode
6467 If you want to build on non-stop mode and observe program behavior
6468 without any chance of disruption by @value{GDBN}, you can set
6469 variables to disable all of the debugger's attempts to modify state,
6470 whether by writing memory, inserting breakpoints, etc. These operate
6471 at a low level, intercepting operations from all commands.
6473 When all of these are set to @code{off}, then @value{GDBN} is said to
6474 be @dfn{observer mode}. As a convenience, the variable
6475 @code{observer} can be set to disable these, plus enable non-stop
6478 Note that @value{GDBN} will not prevent you from making nonsensical
6479 combinations of these settings. For instance, if you have enabled
6480 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6481 then breakpoints that work by writing trap instructions into the code
6482 stream will still not be able to be placed.
6487 @item set observer on
6488 @itemx set observer off
6489 When set to @code{on}, this disables all the permission variables
6490 below (except for @code{insert-fast-tracepoints}), plus enables
6491 non-stop debugging. Setting this to @code{off} switches back to
6492 normal debugging, though remaining in non-stop mode.
6495 Show whether observer mode is on or off.
6497 @kindex may-write-registers
6498 @item set may-write-registers on
6499 @itemx set may-write-registers off
6500 This controls whether @value{GDBN} will attempt to alter the values of
6501 registers, such as with assignment expressions in @code{print}, or the
6502 @code{jump} command. It defaults to @code{on}.
6504 @item show may-write-registers
6505 Show the current permission to write registers.
6507 @kindex may-write-memory
6508 @item set may-write-memory on
6509 @itemx set may-write-memory off
6510 This controls whether @value{GDBN} will attempt to alter the contents
6511 of memory, such as with assignment expressions in @code{print}. It
6512 defaults to @code{on}.
6514 @item show may-write-memory
6515 Show the current permission to write memory.
6517 @kindex may-insert-breakpoints
6518 @item set may-insert-breakpoints on
6519 @itemx set may-insert-breakpoints off
6520 This controls whether @value{GDBN} will attempt to insert breakpoints.
6521 This affects all breakpoints, including internal breakpoints defined
6522 by @value{GDBN}. It defaults to @code{on}.
6524 @item show may-insert-breakpoints
6525 Show the current permission to insert breakpoints.
6527 @kindex may-insert-tracepoints
6528 @item set may-insert-tracepoints on
6529 @itemx set may-insert-tracepoints off
6530 This controls whether @value{GDBN} will attempt to insert (regular)
6531 tracepoints at the beginning of a tracing experiment. It affects only
6532 non-fast tracepoints, fast tracepoints being under the control of
6533 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6535 @item show may-insert-tracepoints
6536 Show the current permission to insert tracepoints.
6538 @kindex may-insert-fast-tracepoints
6539 @item set may-insert-fast-tracepoints on
6540 @itemx set may-insert-fast-tracepoints off
6541 This controls whether @value{GDBN} will attempt to insert fast
6542 tracepoints at the beginning of a tracing experiment. It affects only
6543 fast tracepoints, regular (non-fast) tracepoints being under the
6544 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6546 @item show may-insert-fast-tracepoints
6547 Show the current permission to insert fast tracepoints.
6549 @kindex may-interrupt
6550 @item set may-interrupt on
6551 @itemx set may-interrupt off
6552 This controls whether @value{GDBN} will attempt to interrupt or stop
6553 program execution. When this variable is @code{off}, the
6554 @code{interrupt} command will have no effect, nor will
6555 @kbd{Ctrl-c}. It defaults to @code{on}.
6557 @item show may-interrupt
6558 Show the current permission to interrupt or stop the program.
6562 @node Reverse Execution
6563 @chapter Running programs backward
6564 @cindex reverse execution
6565 @cindex running programs backward
6567 When you are debugging a program, it is not unusual to realize that
6568 you have gone too far, and some event of interest has already happened.
6569 If the target environment supports it, @value{GDBN} can allow you to
6570 ``rewind'' the program by running it backward.
6572 A target environment that supports reverse execution should be able
6573 to ``undo'' the changes in machine state that have taken place as the
6574 program was executing normally. Variables, registers etc.@: should
6575 revert to their previous values. Obviously this requires a great
6576 deal of sophistication on the part of the target environment; not
6577 all target environments can support reverse execution.
6579 When a program is executed in reverse, the instructions that
6580 have most recently been executed are ``un-executed'', in reverse
6581 order. The program counter runs backward, following the previous
6582 thread of execution in reverse. As each instruction is ``un-executed'',
6583 the values of memory and/or registers that were changed by that
6584 instruction are reverted to their previous states. After executing
6585 a piece of source code in reverse, all side effects of that code
6586 should be ``undone'', and all variables should be returned to their
6587 prior values@footnote{
6588 Note that some side effects are easier to undo than others. For instance,
6589 memory and registers are relatively easy, but device I/O is hard. Some
6590 targets may be able undo things like device I/O, and some may not.
6592 The contract between @value{GDBN} and the reverse executing target
6593 requires only that the target do something reasonable when
6594 @value{GDBN} tells it to execute backwards, and then report the
6595 results back to @value{GDBN}. Whatever the target reports back to
6596 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6597 assumes that the memory and registers that the target reports are in a
6598 consistant state, but @value{GDBN} accepts whatever it is given.
6601 If you are debugging in a target environment that supports
6602 reverse execution, @value{GDBN} provides the following commands.
6605 @kindex reverse-continue
6606 @kindex rc @r{(@code{reverse-continue})}
6607 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6608 @itemx rc @r{[}@var{ignore-count}@r{]}
6609 Beginning at the point where your program last stopped, start executing
6610 in reverse. Reverse execution will stop for breakpoints and synchronous
6611 exceptions (signals), just like normal execution. Behavior of
6612 asynchronous signals depends on the target environment.
6614 @kindex reverse-step
6615 @kindex rs @r{(@code{step})}
6616 @item reverse-step @r{[}@var{count}@r{]}
6617 Run the program backward until control reaches the start of a
6618 different source line; then stop it, and return control to @value{GDBN}.
6620 Like the @code{step} command, @code{reverse-step} will only stop
6621 at the beginning of a source line. It ``un-executes'' the previously
6622 executed source line. If the previous source line included calls to
6623 debuggable functions, @code{reverse-step} will step (backward) into
6624 the called function, stopping at the beginning of the @emph{last}
6625 statement in the called function (typically a return statement).
6627 Also, as with the @code{step} command, if non-debuggable functions are
6628 called, @code{reverse-step} will run thru them backward without stopping.
6630 @kindex reverse-stepi
6631 @kindex rsi @r{(@code{reverse-stepi})}
6632 @item reverse-stepi @r{[}@var{count}@r{]}
6633 Reverse-execute one machine instruction. Note that the instruction
6634 to be reverse-executed is @emph{not} the one pointed to by the program
6635 counter, but the instruction executed prior to that one. For instance,
6636 if the last instruction was a jump, @code{reverse-stepi} will take you
6637 back from the destination of the jump to the jump instruction itself.
6639 @kindex reverse-next
6640 @kindex rn @r{(@code{reverse-next})}
6641 @item reverse-next @r{[}@var{count}@r{]}
6642 Run backward to the beginning of the previous line executed in
6643 the current (innermost) stack frame. If the line contains function
6644 calls, they will be ``un-executed'' without stopping. Starting from
6645 the first line of a function, @code{reverse-next} will take you back
6646 to the caller of that function, @emph{before} the function was called,
6647 just as the normal @code{next} command would take you from the last
6648 line of a function back to its return to its caller
6649 @footnote{Unless the code is too heavily optimized.}.
6651 @kindex reverse-nexti
6652 @kindex rni @r{(@code{reverse-nexti})}
6653 @item reverse-nexti @r{[}@var{count}@r{]}
6654 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6655 in reverse, except that called functions are ``un-executed'' atomically.
6656 That is, if the previously executed instruction was a return from
6657 another function, @code{reverse-nexti} will continue to execute
6658 in reverse until the call to that function (from the current stack
6661 @kindex reverse-finish
6662 @item reverse-finish
6663 Just as the @code{finish} command takes you to the point where the
6664 current function returns, @code{reverse-finish} takes you to the point
6665 where it was called. Instead of ending up at the end of the current
6666 function invocation, you end up at the beginning.
6668 @kindex set exec-direction
6669 @item set exec-direction
6670 Set the direction of target execution.
6671 @item set exec-direction reverse
6672 @cindex execute forward or backward in time
6673 @value{GDBN} will perform all execution commands in reverse, until the
6674 exec-direction mode is changed to ``forward''. Affected commands include
6675 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6676 command cannot be used in reverse mode.
6677 @item set exec-direction forward
6678 @value{GDBN} will perform all execution commands in the normal fashion.
6679 This is the default.
6683 @node Process Record and Replay
6684 @chapter Recording Inferior's Execution and Replaying It
6685 @cindex process record and replay
6686 @cindex recording inferior's execution and replaying it
6688 On some platforms, @value{GDBN} provides a special @dfn{process record
6689 and replay} target that can record a log of the process execution, and
6690 replay it later with both forward and reverse execution commands.
6693 When this target is in use, if the execution log includes the record
6694 for the next instruction, @value{GDBN} will debug in @dfn{replay
6695 mode}. In the replay mode, the inferior does not really execute code
6696 instructions. Instead, all the events that normally happen during
6697 code execution are taken from the execution log. While code is not
6698 really executed in replay mode, the values of registers (including the
6699 program counter register) and the memory of the inferior are still
6700 changed as they normally would. Their contents are taken from the
6704 If the record for the next instruction is not in the execution log,
6705 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6706 inferior executes normally, and @value{GDBN} records the execution log
6709 The process record and replay target supports reverse execution
6710 (@pxref{Reverse Execution}), even if the platform on which the
6711 inferior runs does not. However, the reverse execution is limited in
6712 this case by the range of the instructions recorded in the execution
6713 log. In other words, reverse execution on platforms that don't
6714 support it directly can only be done in the replay mode.
6716 When debugging in the reverse direction, @value{GDBN} will work in
6717 replay mode as long as the execution log includes the record for the
6718 previous instruction; otherwise, it will work in record mode, if the
6719 platform supports reverse execution, or stop if not.
6721 For architecture environments that support process record and replay,
6722 @value{GDBN} provides the following commands:
6725 @kindex target record
6726 @kindex target record-full
6727 @kindex target record-btrace
6730 @kindex record btrace
6731 @kindex record btrace bts
6732 @kindex record btrace pt
6738 @kindex rec btrace bts
6739 @kindex rec btrace pt
6742 @item record @var{method}
6743 This command starts the process record and replay target. The
6744 recording method can be specified as parameter. Without a parameter
6745 the command uses the @code{full} recording method. The following
6746 recording methods are available:
6750 Full record/replay recording using @value{GDBN}'s software record and
6751 replay implementation. This method allows replaying and reverse
6754 @item btrace @var{format}
6755 Hardware-supported instruction recording. This method does not record
6756 data. Further, the data is collected in a ring buffer so old data will
6757 be overwritten when the buffer is full. It allows limited reverse
6758 execution. Variables and registers are not available during reverse
6759 execution. In remote debugging, recording continues on disconnect.
6760 Recorded data can be inspected after reconnecting. The recording may
6761 be stopped using @code{record stop}.
6763 The recording format can be specified as parameter. Without a parameter
6764 the command chooses the recording format. The following recording
6765 formats are available:
6769 @cindex branch trace store
6770 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6771 this format, the processor stores a from/to record for each executed
6772 branch in the btrace ring buffer.
6775 @cindex Intel Processor Trace
6776 Use the @dfn{Intel Processor Trace} recording format. In this
6777 format, the processor stores the execution trace in a compressed form
6778 that is afterwards decoded by @value{GDBN}.
6780 The trace can be recorded with very low overhead. The compressed
6781 trace format also allows small trace buffers to already contain a big
6782 number of instructions compared to @acronym{BTS}.
6784 Decoding the recorded execution trace, on the other hand, is more
6785 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6786 increased number of instructions to process. You should increase the
6787 buffer-size with care.
6790 Not all recording formats may be available on all processors.
6793 The process record and replay target can only debug a process that is
6794 already running. Therefore, you need first to start the process with
6795 the @kbd{run} or @kbd{start} commands, and then start the recording
6796 with the @kbd{record @var{method}} command.
6798 @cindex displaced stepping, and process record and replay
6799 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6800 will be automatically disabled when process record and replay target
6801 is started. That's because the process record and replay target
6802 doesn't support displaced stepping.
6804 @cindex non-stop mode, and process record and replay
6805 @cindex asynchronous execution, and process record and replay
6806 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6807 the asynchronous execution mode (@pxref{Background Execution}), not
6808 all recording methods are available. The @code{full} recording method
6809 does not support these two modes.
6814 Stop the process record and replay target. When process record and
6815 replay target stops, the entire execution log will be deleted and the
6816 inferior will either be terminated, or will remain in its final state.
6818 When you stop the process record and replay target in record mode (at
6819 the end of the execution log), the inferior will be stopped at the
6820 next instruction that would have been recorded. In other words, if
6821 you record for a while and then stop recording, the inferior process
6822 will be left in the same state as if the recording never happened.
6824 On the other hand, if the process record and replay target is stopped
6825 while in replay mode (that is, not at the end of the execution log,
6826 but at some earlier point), the inferior process will become ``live''
6827 at that earlier state, and it will then be possible to continue the
6828 usual ``live'' debugging of the process from that state.
6830 When the inferior process exits, or @value{GDBN} detaches from it,
6831 process record and replay target will automatically stop itself.
6835 Go to a specific location in the execution log. There are several
6836 ways to specify the location to go to:
6839 @item record goto begin
6840 @itemx record goto start
6841 Go to the beginning of the execution log.
6843 @item record goto end
6844 Go to the end of the execution log.
6846 @item record goto @var{n}
6847 Go to instruction number @var{n} in the execution log.
6851 @item record save @var{filename}
6852 Save the execution log to a file @file{@var{filename}}.
6853 Default filename is @file{gdb_record.@var{process_id}}, where
6854 @var{process_id} is the process ID of the inferior.
6856 This command may not be available for all recording methods.
6858 @kindex record restore
6859 @item record restore @var{filename}
6860 Restore the execution log from a file @file{@var{filename}}.
6861 File must have been created with @code{record save}.
6863 @kindex set record full
6864 @item set record full insn-number-max @var{limit}
6865 @itemx set record full insn-number-max unlimited
6866 Set the limit of instructions to be recorded for the @code{full}
6867 recording method. Default value is 200000.
6869 If @var{limit} is a positive number, then @value{GDBN} will start
6870 deleting instructions from the log once the number of the record
6871 instructions becomes greater than @var{limit}. For every new recorded
6872 instruction, @value{GDBN} will delete the earliest recorded
6873 instruction to keep the number of recorded instructions at the limit.
6874 (Since deleting recorded instructions loses information, @value{GDBN}
6875 lets you control what happens when the limit is reached, by means of
6876 the @code{stop-at-limit} option, described below.)
6878 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6879 delete recorded instructions from the execution log. The number of
6880 recorded instructions is limited only by the available memory.
6882 @kindex show record full
6883 @item show record full insn-number-max
6884 Show the limit of instructions to be recorded with the @code{full}
6887 @item set record full stop-at-limit
6888 Control the behavior of the @code{full} recording method when the
6889 number of recorded instructions reaches the limit. If ON (the
6890 default), @value{GDBN} will stop when the limit is reached for the
6891 first time and ask you whether you want to stop the inferior or
6892 continue running it and recording the execution log. If you decide
6893 to continue recording, each new recorded instruction will cause the
6894 oldest one to be deleted.
6896 If this option is OFF, @value{GDBN} will automatically delete the
6897 oldest record to make room for each new one, without asking.
6899 @item show record full stop-at-limit
6900 Show the current setting of @code{stop-at-limit}.
6902 @item set record full memory-query
6903 Control the behavior when @value{GDBN} is unable to record memory
6904 changes caused by an instruction for the @code{full} recording method.
6905 If ON, @value{GDBN} will query whether to stop the inferior in that
6908 If this option is OFF (the default), @value{GDBN} will automatically
6909 ignore the effect of such instructions on memory. Later, when
6910 @value{GDBN} replays this execution log, it will mark the log of this
6911 instruction as not accessible, and it will not affect the replay
6914 @item show record full memory-query
6915 Show the current setting of @code{memory-query}.
6917 @kindex set record btrace
6918 The @code{btrace} record target does not trace data. As a
6919 convenience, when replaying, @value{GDBN} reads read-only memory off
6920 the live program directly, assuming that the addresses of the
6921 read-only areas don't change. This for example makes it possible to
6922 disassemble code while replaying, but not to print variables.
6923 In some cases, being able to inspect variables might be useful.
6924 You can use the following command for that:
6926 @item set record btrace replay-memory-access
6927 Control the behavior of the @code{btrace} recording method when
6928 accessing memory during replay. If @code{read-only} (the default),
6929 @value{GDBN} will only allow accesses to read-only memory.
6930 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6931 and to read-write memory. Beware that the accessed memory corresponds
6932 to the live target and not necessarily to the current replay
6935 @kindex show record btrace
6936 @item show record btrace replay-memory-access
6937 Show the current setting of @code{replay-memory-access}.
6939 @kindex set record btrace bts
6940 @item set record btrace bts buffer-size @var{size}
6941 @itemx set record btrace bts buffer-size unlimited
6942 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6943 format. Default is 64KB.
6945 If @var{size} is a positive number, then @value{GDBN} will try to
6946 allocate a buffer of at least @var{size} bytes for each new thread
6947 that uses the btrace recording method and the @acronym{BTS} format.
6948 The actually obtained buffer size may differ from the requested
6949 @var{size}. Use the @code{info record} command to see the actual
6950 buffer size for each thread that uses the btrace recording method and
6951 the @acronym{BTS} format.
6953 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6954 allocate a buffer of 4MB.
6956 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6957 also need longer to process the branch trace data before it can be used.
6959 @item show record btrace bts buffer-size @var{size}
6960 Show the current setting of the requested ring buffer size for branch
6961 tracing in @acronym{BTS} format.
6963 @kindex set record btrace pt
6964 @item set record btrace pt buffer-size @var{size}
6965 @itemx set record btrace pt buffer-size unlimited
6966 Set the requested ring buffer size for branch tracing in Intel
6967 Processor Trace format. Default is 16KB.
6969 If @var{size} is a positive number, then @value{GDBN} will try to
6970 allocate a buffer of at least @var{size} bytes for each new thread
6971 that uses the btrace recording method and the Intel Processor Trace
6972 format. The actually obtained buffer size may differ from the
6973 requested @var{size}. Use the @code{info record} command to see the
6974 actual buffer size for each thread.
6976 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6977 allocate a buffer of 4MB.
6979 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6980 also need longer to process the branch trace data before it can be used.
6982 @item show record btrace pt buffer-size @var{size}
6983 Show the current setting of the requested ring buffer size for branch
6984 tracing in Intel Processor Trace format.
6988 Show various statistics about the recording depending on the recording
6993 For the @code{full} recording method, it shows the state of process
6994 record and its in-memory execution log buffer, including:
6998 Whether in record mode or replay mode.
7000 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7002 Highest recorded instruction number.
7004 Current instruction about to be replayed (if in replay mode).
7006 Number of instructions contained in the execution log.
7008 Maximum number of instructions that may be contained in the execution log.
7012 For the @code{btrace} recording method, it shows:
7018 Number of instructions that have been recorded.
7020 Number of blocks of sequential control-flow formed by the recorded
7023 Whether in record mode or replay mode.
7026 For the @code{bts} recording format, it also shows:
7029 Size of the perf ring buffer.
7032 For the @code{pt} recording format, it also shows:
7035 Size of the perf ring buffer.
7039 @kindex record delete
7042 When record target runs in replay mode (``in the past''), delete the
7043 subsequent execution log and begin to record a new execution log starting
7044 from the current address. This means you will abandon the previously
7045 recorded ``future'' and begin recording a new ``future''.
7047 @kindex record instruction-history
7048 @kindex rec instruction-history
7049 @item record instruction-history
7050 Disassembles instructions from the recorded execution log. By
7051 default, ten instructions are disassembled. This can be changed using
7052 the @code{set record instruction-history-size} command. Instructions
7053 are printed in execution order.
7055 It can also print mixed source+disassembly if you specify the the
7056 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7057 as well as in symbolic form by specifying the @code{/r} modifier.
7059 The current position marker is printed for the instruction at the
7060 current program counter value. This instruction can appear multiple
7061 times in the trace and the current position marker will be printed
7062 every time. To omit the current position marker, specify the
7065 To better align the printed instructions when the trace contains
7066 instructions from more than one function, the function name may be
7067 omitted by specifying the @code{/f} modifier.
7069 Speculatively executed instructions are prefixed with @samp{?}. This
7070 feature is not available for all recording formats.
7072 There are several ways to specify what part of the execution log to
7076 @item record instruction-history @var{insn}
7077 Disassembles ten instructions starting from instruction number
7080 @item record instruction-history @var{insn}, +/-@var{n}
7081 Disassembles @var{n} instructions around instruction number
7082 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7083 @var{n} instructions after instruction number @var{insn}. If
7084 @var{n} is preceded with @code{-}, disassembles @var{n}
7085 instructions before instruction number @var{insn}.
7087 @item record instruction-history
7088 Disassembles ten more instructions after the last disassembly.
7090 @item record instruction-history -
7091 Disassembles ten more instructions before the last disassembly.
7093 @item record instruction-history @var{begin}, @var{end}
7094 Disassembles instructions beginning with instruction number
7095 @var{begin} until instruction number @var{end}. The instruction
7096 number @var{end} is included.
7099 This command may not be available for all recording methods.
7102 @item set record instruction-history-size @var{size}
7103 @itemx set record instruction-history-size unlimited
7104 Define how many instructions to disassemble in the @code{record
7105 instruction-history} command. The default value is 10.
7106 A @var{size} of @code{unlimited} means unlimited instructions.
7109 @item show record instruction-history-size
7110 Show how many instructions to disassemble in the @code{record
7111 instruction-history} command.
7113 @kindex record function-call-history
7114 @kindex rec function-call-history
7115 @item record function-call-history
7116 Prints the execution history at function granularity. It prints one
7117 line for each sequence of instructions that belong to the same
7118 function giving the name of that function, the source lines
7119 for this instruction sequence (if the @code{/l} modifier is
7120 specified), and the instructions numbers that form the sequence (if
7121 the @code{/i} modifier is specified). The function names are indented
7122 to reflect the call stack depth if the @code{/c} modifier is
7123 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7127 (@value{GDBP}) @b{list 1, 10}
7138 (@value{GDBP}) @b{record function-call-history /ilc}
7139 1 bar inst 1,4 at foo.c:6,8
7140 2 foo inst 5,10 at foo.c:2,3
7141 3 bar inst 11,13 at foo.c:9,10
7144 By default, ten lines are printed. This can be changed using the
7145 @code{set record function-call-history-size} command. Functions are
7146 printed in execution order. There are several ways to specify what
7150 @item record function-call-history @var{func}
7151 Prints ten functions starting from function number @var{func}.
7153 @item record function-call-history @var{func}, +/-@var{n}
7154 Prints @var{n} functions around function number @var{func}. If
7155 @var{n} is preceded with @code{+}, prints @var{n} functions after
7156 function number @var{func}. If @var{n} is preceded with @code{-},
7157 prints @var{n} functions before function number @var{func}.
7159 @item record function-call-history
7160 Prints ten more functions after the last ten-line print.
7162 @item record function-call-history -
7163 Prints ten more functions before the last ten-line print.
7165 @item record function-call-history @var{begin}, @var{end}
7166 Prints functions beginning with function number @var{begin} until
7167 function number @var{end}. The function number @var{end} is included.
7170 This command may not be available for all recording methods.
7172 @item set record function-call-history-size @var{size}
7173 @itemx set record function-call-history-size unlimited
7174 Define how many lines to print in the
7175 @code{record function-call-history} command. The default value is 10.
7176 A size of @code{unlimited} means unlimited lines.
7178 @item show record function-call-history-size
7179 Show how many lines to print in the
7180 @code{record function-call-history} command.
7185 @chapter Examining the Stack
7187 When your program has stopped, the first thing you need to know is where it
7188 stopped and how it got there.
7191 Each time your program performs a function call, information about the call
7193 That information includes the location of the call in your program,
7194 the arguments of the call,
7195 and the local variables of the function being called.
7196 The information is saved in a block of data called a @dfn{stack frame}.
7197 The stack frames are allocated in a region of memory called the @dfn{call
7200 When your program stops, the @value{GDBN} commands for examining the
7201 stack allow you to see all of this information.
7203 @cindex selected frame
7204 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7205 @value{GDBN} commands refer implicitly to the selected frame. In
7206 particular, whenever you ask @value{GDBN} for the value of a variable in
7207 your program, the value is found in the selected frame. There are
7208 special @value{GDBN} commands to select whichever frame you are
7209 interested in. @xref{Selection, ,Selecting a Frame}.
7211 When your program stops, @value{GDBN} automatically selects the
7212 currently executing frame and describes it briefly, similar to the
7213 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7216 * Frames:: Stack frames
7217 * Backtrace:: Backtraces
7218 * Selection:: Selecting a frame
7219 * Frame Info:: Information on a frame
7220 * Frame Filter Management:: Managing frame filters
7225 @section Stack Frames
7227 @cindex frame, definition
7229 The call stack is divided up into contiguous pieces called @dfn{stack
7230 frames}, or @dfn{frames} for short; each frame is the data associated
7231 with one call to one function. The frame contains the arguments given
7232 to the function, the function's local variables, and the address at
7233 which the function is executing.
7235 @cindex initial frame
7236 @cindex outermost frame
7237 @cindex innermost frame
7238 When your program is started, the stack has only one frame, that of the
7239 function @code{main}. This is called the @dfn{initial} frame or the
7240 @dfn{outermost} frame. Each time a function is called, a new frame is
7241 made. Each time a function returns, the frame for that function invocation
7242 is eliminated. If a function is recursive, there can be many frames for
7243 the same function. The frame for the function in which execution is
7244 actually occurring is called the @dfn{innermost} frame. This is the most
7245 recently created of all the stack frames that still exist.
7247 @cindex frame pointer
7248 Inside your program, stack frames are identified by their addresses. A
7249 stack frame consists of many bytes, each of which has its own address; each
7250 kind of computer has a convention for choosing one byte whose
7251 address serves as the address of the frame. Usually this address is kept
7252 in a register called the @dfn{frame pointer register}
7253 (@pxref{Registers, $fp}) while execution is going on in that frame.
7255 @cindex frame number
7256 @value{GDBN} assigns numbers to all existing stack frames, starting with
7257 zero for the innermost frame, one for the frame that called it,
7258 and so on upward. These numbers do not really exist in your program;
7259 they are assigned by @value{GDBN} to give you a way of designating stack
7260 frames in @value{GDBN} commands.
7262 @c The -fomit-frame-pointer below perennially causes hbox overflow
7263 @c underflow problems.
7264 @cindex frameless execution
7265 Some compilers provide a way to compile functions so that they operate
7266 without stack frames. (For example, the @value{NGCC} option
7268 @samp{-fomit-frame-pointer}
7270 generates functions without a frame.)
7271 This is occasionally done with heavily used library functions to save
7272 the frame setup time. @value{GDBN} has limited facilities for dealing
7273 with these function invocations. If the innermost function invocation
7274 has no stack frame, @value{GDBN} nevertheless regards it as though
7275 it had a separate frame, which is numbered zero as usual, allowing
7276 correct tracing of the function call chain. However, @value{GDBN} has
7277 no provision for frameless functions elsewhere in the stack.
7283 @cindex call stack traces
7284 A backtrace is a summary of how your program got where it is. It shows one
7285 line per frame, for many frames, starting with the currently executing
7286 frame (frame zero), followed by its caller (frame one), and on up the
7289 @anchor{backtrace-command}
7292 @kindex bt @r{(@code{backtrace})}
7295 Print a backtrace of the entire stack: one line per frame for all
7296 frames in the stack.
7298 You can stop the backtrace at any time by typing the system interrupt
7299 character, normally @kbd{Ctrl-c}.
7301 @item backtrace @var{n}
7303 Similar, but print only the innermost @var{n} frames.
7305 @item backtrace -@var{n}
7307 Similar, but print only the outermost @var{n} frames.
7309 @item backtrace full
7311 @itemx bt full @var{n}
7312 @itemx bt full -@var{n}
7313 Print the values of the local variables also. As described above,
7314 @var{n} specifies the number of frames to print.
7316 @item backtrace no-filters
7317 @itemx bt no-filters
7318 @itemx bt no-filters @var{n}
7319 @itemx bt no-filters -@var{n}
7320 @itemx bt no-filters full
7321 @itemx bt no-filters full @var{n}
7322 @itemx bt no-filters full -@var{n}
7323 Do not run Python frame filters on this backtrace. @xref{Frame
7324 Filter API}, for more information. Additionally use @ref{disable
7325 frame-filter all} to turn off all frame filters. This is only
7326 relevant when @value{GDBN} has been configured with @code{Python}
7332 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7333 are additional aliases for @code{backtrace}.
7335 @cindex multiple threads, backtrace
7336 In a multi-threaded program, @value{GDBN} by default shows the
7337 backtrace only for the current thread. To display the backtrace for
7338 several or all of the threads, use the command @code{thread apply}
7339 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7340 apply all backtrace}, @value{GDBN} will display the backtrace for all
7341 the threads; this is handy when you debug a core dump of a
7342 multi-threaded program.
7344 Each line in the backtrace shows the frame number and the function name.
7345 The program counter value is also shown---unless you use @code{set
7346 print address off}. The backtrace also shows the source file name and
7347 line number, as well as the arguments to the function. The program
7348 counter value is omitted if it is at the beginning of the code for that
7351 Here is an example of a backtrace. It was made with the command
7352 @samp{bt 3}, so it shows the innermost three frames.
7356 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7358 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7359 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7361 (More stack frames follow...)
7366 The display for frame zero does not begin with a program counter
7367 value, indicating that your program has stopped at the beginning of the
7368 code for line @code{993} of @code{builtin.c}.
7371 The value of parameter @code{data} in frame 1 has been replaced by
7372 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7373 only if it is a scalar (integer, pointer, enumeration, etc). See command
7374 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7375 on how to configure the way function parameter values are printed.
7377 @cindex optimized out, in backtrace
7378 @cindex function call arguments, optimized out
7379 If your program was compiled with optimizations, some compilers will
7380 optimize away arguments passed to functions if those arguments are
7381 never used after the call. Such optimizations generate code that
7382 passes arguments through registers, but doesn't store those arguments
7383 in the stack frame. @value{GDBN} has no way of displaying such
7384 arguments in stack frames other than the innermost one. Here's what
7385 such a backtrace might look like:
7389 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7391 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7392 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7394 (More stack frames follow...)
7399 The values of arguments that were not saved in their stack frames are
7400 shown as @samp{<optimized out>}.
7402 If you need to display the values of such optimized-out arguments,
7403 either deduce that from other variables whose values depend on the one
7404 you are interested in, or recompile without optimizations.
7406 @cindex backtrace beyond @code{main} function
7407 @cindex program entry point
7408 @cindex startup code, and backtrace
7409 Most programs have a standard user entry point---a place where system
7410 libraries and startup code transition into user code. For C this is
7411 @code{main}@footnote{
7412 Note that embedded programs (the so-called ``free-standing''
7413 environment) are not required to have a @code{main} function as the
7414 entry point. They could even have multiple entry points.}.
7415 When @value{GDBN} finds the entry function in a backtrace
7416 it will terminate the backtrace, to avoid tracing into highly
7417 system-specific (and generally uninteresting) code.
7419 If you need to examine the startup code, or limit the number of levels
7420 in a backtrace, you can change this behavior:
7423 @item set backtrace past-main
7424 @itemx set backtrace past-main on
7425 @kindex set backtrace
7426 Backtraces will continue past the user entry point.
7428 @item set backtrace past-main off
7429 Backtraces will stop when they encounter the user entry point. This is the
7432 @item show backtrace past-main
7433 @kindex show backtrace
7434 Display the current user entry point backtrace policy.
7436 @item set backtrace past-entry
7437 @itemx set backtrace past-entry on
7438 Backtraces will continue past the internal entry point of an application.
7439 This entry point is encoded by the linker when the application is built,
7440 and is likely before the user entry point @code{main} (or equivalent) is called.
7442 @item set backtrace past-entry off
7443 Backtraces will stop when they encounter the internal entry point of an
7444 application. This is the default.
7446 @item show backtrace past-entry
7447 Display the current internal entry point backtrace policy.
7449 @item set backtrace limit @var{n}
7450 @itemx set backtrace limit 0
7451 @itemx set backtrace limit unlimited
7452 @cindex backtrace limit
7453 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7454 or zero means unlimited levels.
7456 @item show backtrace limit
7457 Display the current limit on backtrace levels.
7460 You can control how file names are displayed.
7463 @item set filename-display
7464 @itemx set filename-display relative
7465 @cindex filename-display
7466 Display file names relative to the compilation directory. This is the default.
7468 @item set filename-display basename
7469 Display only basename of a filename.
7471 @item set filename-display absolute
7472 Display an absolute filename.
7474 @item show filename-display
7475 Show the current way to display filenames.
7479 @section Selecting a Frame
7481 Most commands for examining the stack and other data in your program work on
7482 whichever stack frame is selected at the moment. Here are the commands for
7483 selecting a stack frame; all of them finish by printing a brief description
7484 of the stack frame just selected.
7487 @kindex frame@r{, selecting}
7488 @kindex f @r{(@code{frame})}
7491 Select frame number @var{n}. Recall that frame zero is the innermost
7492 (currently executing) frame, frame one is the frame that called the
7493 innermost one, and so on. The highest-numbered frame is the one for
7496 @item frame @var{stack-addr} [ @var{pc-addr} ]
7497 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7498 Select the frame at address @var{stack-addr}. This is useful mainly if the
7499 chaining of stack frames has been damaged by a bug, making it
7500 impossible for @value{GDBN} to assign numbers properly to all frames. In
7501 addition, this can be useful when your program has multiple stacks and
7502 switches between them. The optional @var{pc-addr} can also be given to
7503 specify the value of PC for the stack frame.
7507 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7508 numbers @var{n}, this advances toward the outermost frame, to higher
7509 frame numbers, to frames that have existed longer.
7512 @kindex do @r{(@code{down})}
7514 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7515 positive numbers @var{n}, this advances toward the innermost frame, to
7516 lower frame numbers, to frames that were created more recently.
7517 You may abbreviate @code{down} as @code{do}.
7520 All of these commands end by printing two lines of output describing the
7521 frame. The first line shows the frame number, the function name, the
7522 arguments, and the source file and line number of execution in that
7523 frame. The second line shows the text of that source line.
7531 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7533 10 read_input_file (argv[i]);
7537 After such a printout, the @code{list} command with no arguments
7538 prints ten lines centered on the point of execution in the frame.
7539 You can also edit the program at the point of execution with your favorite
7540 editing program by typing @code{edit}.
7541 @xref{List, ,Printing Source Lines},
7545 @kindex select-frame
7547 The @code{select-frame} command is a variant of @code{frame} that does
7548 not display the new frame after selecting it. This command is
7549 intended primarily for use in @value{GDBN} command scripts, where the
7550 output might be unnecessary and distracting.
7552 @kindex down-silently
7554 @item up-silently @var{n}
7555 @itemx down-silently @var{n}
7556 These two commands are variants of @code{up} and @code{down},
7557 respectively; they differ in that they do their work silently, without
7558 causing display of the new frame. They are intended primarily for use
7559 in @value{GDBN} command scripts, where the output might be unnecessary and
7564 @section Information About a Frame
7566 There are several other commands to print information about the selected
7572 When used without any argument, this command does not change which
7573 frame is selected, but prints a brief description of the currently
7574 selected stack frame. It can be abbreviated @code{f}. With an
7575 argument, this command is used to select a stack frame.
7576 @xref{Selection, ,Selecting a Frame}.
7579 @kindex info f @r{(@code{info frame})}
7582 This command prints a verbose description of the selected stack frame,
7587 the address of the frame
7589 the address of the next frame down (called by this frame)
7591 the address of the next frame up (caller of this frame)
7593 the language in which the source code corresponding to this frame is written
7595 the address of the frame's arguments
7597 the address of the frame's local variables
7599 the program counter saved in it (the address of execution in the caller frame)
7601 which registers were saved in the frame
7604 @noindent The verbose description is useful when
7605 something has gone wrong that has made the stack format fail to fit
7606 the usual conventions.
7608 @item info frame @var{addr}
7609 @itemx info f @var{addr}
7610 Print a verbose description of the frame at address @var{addr}, without
7611 selecting that frame. The selected frame remains unchanged by this
7612 command. This requires the same kind of address (more than one for some
7613 architectures) that you specify in the @code{frame} command.
7614 @xref{Selection, ,Selecting a Frame}.
7618 Print the arguments of the selected frame, each on a separate line.
7622 Print the local variables of the selected frame, each on a separate
7623 line. These are all variables (declared either static or automatic)
7624 accessible at the point of execution of the selected frame.
7628 @node Frame Filter Management
7629 @section Management of Frame Filters.
7630 @cindex managing frame filters
7632 Frame filters are Python based utilities to manage and decorate the
7633 output of frames. @xref{Frame Filter API}, for further information.
7635 Managing frame filters is performed by several commands available
7636 within @value{GDBN}, detailed here.
7639 @kindex info frame-filter
7640 @item info frame-filter
7641 Print a list of installed frame filters from all dictionaries, showing
7642 their name, priority and enabled status.
7644 @kindex disable frame-filter
7645 @anchor{disable frame-filter all}
7646 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7647 Disable a frame filter in the dictionary matching
7648 @var{filter-dictionary} and @var{filter-name}. The
7649 @var{filter-dictionary} may be @code{all}, @code{global},
7650 @code{progspace}, or the name of the object file where the frame filter
7651 dictionary resides. When @code{all} is specified, all frame filters
7652 across all dictionaries are disabled. The @var{filter-name} is the name
7653 of the frame filter and is used when @code{all} is not the option for
7654 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7655 may be enabled again later.
7657 @kindex enable frame-filter
7658 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7659 Enable a frame filter in the dictionary matching
7660 @var{filter-dictionary} and @var{filter-name}. The
7661 @var{filter-dictionary} may be @code{all}, @code{global},
7662 @code{progspace} or the name of the object file where the frame filter
7663 dictionary resides. When @code{all} is specified, all frame filters across
7664 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7665 filter and is used when @code{all} is not the option for
7666 @var{filter-dictionary}.
7671 (gdb) info frame-filter
7673 global frame-filters:
7674 Priority Enabled Name
7675 1000 No PrimaryFunctionFilter
7678 progspace /build/test frame-filters:
7679 Priority Enabled Name
7680 100 Yes ProgspaceFilter
7682 objfile /build/test frame-filters:
7683 Priority Enabled Name
7684 999 Yes BuildProgra Filter
7686 (gdb) disable frame-filter /build/test BuildProgramFilter
7687 (gdb) info frame-filter
7689 global frame-filters:
7690 Priority Enabled Name
7691 1000 No PrimaryFunctionFilter
7694 progspace /build/test frame-filters:
7695 Priority Enabled Name
7696 100 Yes ProgspaceFilter
7698 objfile /build/test frame-filters:
7699 Priority Enabled Name
7700 999 No BuildProgramFilter
7702 (gdb) enable frame-filter global PrimaryFunctionFilter
7703 (gdb) info frame-filter
7705 global frame-filters:
7706 Priority Enabled Name
7707 1000 Yes PrimaryFunctionFilter
7710 progspace /build/test frame-filters:
7711 Priority Enabled Name
7712 100 Yes ProgspaceFilter
7714 objfile /build/test frame-filters:
7715 Priority Enabled Name
7716 999 No BuildProgramFilter
7719 @kindex set frame-filter priority
7720 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7721 Set the @var{priority} of a frame filter in the dictionary matching
7722 @var{filter-dictionary}, and the frame filter name matching
7723 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7724 @code{progspace} or the name of the object file where the frame filter
7725 dictionary resides. The @var{priority} is an integer.
7727 @kindex show frame-filter priority
7728 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7729 Show the @var{priority} of a frame filter in the dictionary matching
7730 @var{filter-dictionary}, and the frame filter name matching
7731 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7732 @code{progspace} or the name of the object file where the frame filter
7738 (gdb) info frame-filter
7740 global frame-filters:
7741 Priority Enabled Name
7742 1000 Yes PrimaryFunctionFilter
7745 progspace /build/test frame-filters:
7746 Priority Enabled Name
7747 100 Yes ProgspaceFilter
7749 objfile /build/test frame-filters:
7750 Priority Enabled Name
7751 999 No BuildProgramFilter
7753 (gdb) set frame-filter priority global Reverse 50
7754 (gdb) info frame-filter
7756 global frame-filters:
7757 Priority Enabled Name
7758 1000 Yes PrimaryFunctionFilter
7761 progspace /build/test frame-filters:
7762 Priority Enabled Name
7763 100 Yes ProgspaceFilter
7765 objfile /build/test frame-filters:
7766 Priority Enabled Name
7767 999 No BuildProgramFilter
7772 @chapter Examining Source Files
7774 @value{GDBN} can print parts of your program's source, since the debugging
7775 information recorded in the program tells @value{GDBN} what source files were
7776 used to build it. When your program stops, @value{GDBN} spontaneously prints
7777 the line where it stopped. Likewise, when you select a stack frame
7778 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7779 execution in that frame has stopped. You can print other portions of
7780 source files by explicit command.
7782 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7783 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7784 @value{GDBN} under @sc{gnu} Emacs}.
7787 * List:: Printing source lines
7788 * Specify Location:: How to specify code locations
7789 * Edit:: Editing source files
7790 * Search:: Searching source files
7791 * Source Path:: Specifying source directories
7792 * Machine Code:: Source and machine code
7796 @section Printing Source Lines
7799 @kindex l @r{(@code{list})}
7800 To print lines from a source file, use the @code{list} command
7801 (abbreviated @code{l}). By default, ten lines are printed.
7802 There are several ways to specify what part of the file you want to
7803 print; see @ref{Specify Location}, for the full list.
7805 Here are the forms of the @code{list} command most commonly used:
7808 @item list @var{linenum}
7809 Print lines centered around line number @var{linenum} in the
7810 current source file.
7812 @item list @var{function}
7813 Print lines centered around the beginning of function
7817 Print more lines. If the last lines printed were printed with a
7818 @code{list} command, this prints lines following the last lines
7819 printed; however, if the last line printed was a solitary line printed
7820 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7821 Stack}), this prints lines centered around that line.
7824 Print lines just before the lines last printed.
7827 @cindex @code{list}, how many lines to display
7828 By default, @value{GDBN} prints ten source lines with any of these forms of
7829 the @code{list} command. You can change this using @code{set listsize}:
7832 @kindex set listsize
7833 @item set listsize @var{count}
7834 @itemx set listsize unlimited
7835 Make the @code{list} command display @var{count} source lines (unless
7836 the @code{list} argument explicitly specifies some other number).
7837 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7839 @kindex show listsize
7841 Display the number of lines that @code{list} prints.
7844 Repeating a @code{list} command with @key{RET} discards the argument,
7845 so it is equivalent to typing just @code{list}. This is more useful
7846 than listing the same lines again. An exception is made for an
7847 argument of @samp{-}; that argument is preserved in repetition so that
7848 each repetition moves up in the source file.
7850 In general, the @code{list} command expects you to supply zero, one or two
7851 @dfn{locations}. Locations specify source lines; there are several ways
7852 of writing them (@pxref{Specify Location}), but the effect is always
7853 to specify some source line.
7855 Here is a complete description of the possible arguments for @code{list}:
7858 @item list @var{location}
7859 Print lines centered around the line specified by @var{location}.
7861 @item list @var{first},@var{last}
7862 Print lines from @var{first} to @var{last}. Both arguments are
7863 locations. When a @code{list} command has two locations, and the
7864 source file of the second location is omitted, this refers to
7865 the same source file as the first location.
7867 @item list ,@var{last}
7868 Print lines ending with @var{last}.
7870 @item list @var{first},
7871 Print lines starting with @var{first}.
7874 Print lines just after the lines last printed.
7877 Print lines just before the lines last printed.
7880 As described in the preceding table.
7883 @node Specify Location
7884 @section Specifying a Location
7885 @cindex specifying location
7887 @cindex source location
7890 * Linespec Locations:: Linespec locations
7891 * Explicit Locations:: Explicit locations
7892 * Address Locations:: Address locations
7895 Several @value{GDBN} commands accept arguments that specify a location
7896 of your program's code. Since @value{GDBN} is a source-level
7897 debugger, a location usually specifies some line in the source code.
7898 Locations may be specified using three different formats:
7899 linespec locations, explicit locations, or address locations.
7901 @node Linespec Locations
7902 @subsection Linespec Locations
7903 @cindex linespec locations
7905 A @dfn{linespec} is a colon-separated list of source location parameters such
7906 as file name, function name, etc. Here are all the different ways of
7907 specifying a linespec:
7911 Specifies the line number @var{linenum} of the current source file.
7914 @itemx +@var{offset}
7915 Specifies the line @var{offset} lines before or after the @dfn{current
7916 line}. For the @code{list} command, the current line is the last one
7917 printed; for the breakpoint commands, this is the line at which
7918 execution stopped in the currently selected @dfn{stack frame}
7919 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7920 used as the second of the two linespecs in a @code{list} command,
7921 this specifies the line @var{offset} lines up or down from the first
7924 @item @var{filename}:@var{linenum}
7925 Specifies the line @var{linenum} in the source file @var{filename}.
7926 If @var{filename} is a relative file name, then it will match any
7927 source file name with the same trailing components. For example, if
7928 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7929 name of @file{/build/trunk/gcc/expr.c}, but not
7930 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7932 @item @var{function}
7933 Specifies the line that begins the body of the function @var{function}.
7934 For example, in C, this is the line with the open brace.
7936 By default, in C@t{++} and Ada, @var{function} is interpreted as
7937 specifying all functions named @var{function} in all scopes. For
7938 C@t{++}, this means in all namespaces and classes. For Ada, this
7939 means in all packages.
7941 For example, assuming a program with C@t{++} symbols named
7942 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7943 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7945 Commands that accept a linespec let you override this with the
7946 @code{-qualified} option. For example, @w{@kbd{break -qualified
7947 func}} sets a breakpoint on a free-function named @code{func} ignoring
7948 any C@t{++} class methods and namespace functions called @code{func}.
7950 @xref{Explicit Locations}.
7952 @item @var{function}:@var{label}
7953 Specifies the line where @var{label} appears in @var{function}.
7955 @item @var{filename}:@var{function}
7956 Specifies the line that begins the body of the function @var{function}
7957 in the file @var{filename}. You only need the file name with a
7958 function name to avoid ambiguity when there are identically named
7959 functions in different source files.
7962 Specifies the line at which the label named @var{label} appears
7963 in the function corresponding to the currently selected stack frame.
7964 If there is no current selected stack frame (for instance, if the inferior
7965 is not running), then @value{GDBN} will not search for a label.
7967 @cindex breakpoint at static probe point
7968 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7969 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7970 applications to embed static probes. @xref{Static Probe Points}, for more
7971 information on finding and using static probes. This form of linespec
7972 specifies the location of such a static probe.
7974 If @var{objfile} is given, only probes coming from that shared library
7975 or executable matching @var{objfile} as a regular expression are considered.
7976 If @var{provider} is given, then only probes from that provider are considered.
7977 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7978 each one of those probes.
7981 @node Explicit Locations
7982 @subsection Explicit Locations
7983 @cindex explicit locations
7985 @dfn{Explicit locations} allow the user to directly specify the source
7986 location's parameters using option-value pairs.
7988 Explicit locations are useful when several functions, labels, or
7989 file names have the same name (base name for files) in the program's
7990 sources. In these cases, explicit locations point to the source
7991 line you meant more accurately and unambiguously. Also, using
7992 explicit locations might be faster in large programs.
7994 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7995 defined in the file named @file{foo} or the label @code{bar} in a function
7996 named @code{foo}. @value{GDBN} must search either the file system or
7997 the symbol table to know.
7999 The list of valid explicit location options is summarized in the
8003 @item -source @var{filename}
8004 The value specifies the source file name. To differentiate between
8005 files with the same base name, prepend as many directories as is necessary
8006 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8007 @value{GDBN} will use the first file it finds with the given base
8008 name. This option requires the use of either @code{-function} or @code{-line}.
8010 @item -function @var{function}
8011 The value specifies the name of a function. Operations
8012 on function locations unmodified by other options (such as @code{-label}
8013 or @code{-line}) refer to the line that begins the body of the function.
8014 In C, for example, this is the line with the open brace.
8016 By default, in C@t{++} and Ada, @var{function} is interpreted as
8017 specifying all functions named @var{function} in all scopes. For
8018 C@t{++}, this means in all namespaces and classes. For Ada, this
8019 means in all packages.
8021 For example, assuming a program with C@t{++} symbols named
8022 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8023 -function func}} and @w{@kbd{break -function B::func}} set a
8024 breakpoint on both symbols.
8026 You can use the @kbd{-qualified} flag to override this (see below).
8030 This flag makes @value{GDBN} interpret a function name specified with
8031 @kbd{-function} as a complete fully-qualified name.
8033 For example, assuming a C@t{++} program with symbols named
8034 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8035 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8037 (Note: the @kbd{-qualified} option can precede a linespec as well
8038 (@pxref{Linespec Locations}), so the particular example above could be
8039 simplified as @w{@kbd{break -qualified B::func}}.)
8041 @item -label @var{label}
8042 The value specifies the name of a label. When the function
8043 name is not specified, the label is searched in the function of the currently
8044 selected stack frame.
8046 @item -line @var{number}
8047 The value specifies a line offset for the location. The offset may either
8048 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8049 the command. When specified without any other options, the line offset is
8050 relative to the current line.
8053 Explicit location options may be abbreviated by omitting any non-unique
8054 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8056 @node Address Locations
8057 @subsection Address Locations
8058 @cindex address locations
8060 @dfn{Address locations} indicate a specific program address. They have
8061 the generalized form *@var{address}.
8063 For line-oriented commands, such as @code{list} and @code{edit}, this
8064 specifies a source line that contains @var{address}. For @code{break} and
8065 other breakpoint-oriented commands, this can be used to set breakpoints in
8066 parts of your program which do not have debugging information or
8069 Here @var{address} may be any expression valid in the current working
8070 language (@pxref{Languages, working language}) that specifies a code
8071 address. In addition, as a convenience, @value{GDBN} extends the
8072 semantics of expressions used in locations to cover several situations
8073 that frequently occur during debugging. Here are the various forms
8077 @item @var{expression}
8078 Any expression valid in the current working language.
8080 @item @var{funcaddr}
8081 An address of a function or procedure derived from its name. In C,
8082 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8083 simply the function's name @var{function} (and actually a special case
8084 of a valid expression). In Pascal and Modula-2, this is
8085 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8086 (although the Pascal form also works).
8088 This form specifies the address of the function's first instruction,
8089 before the stack frame and arguments have been set up.
8091 @item '@var{filename}':@var{funcaddr}
8092 Like @var{funcaddr} above, but also specifies the name of the source
8093 file explicitly. This is useful if the name of the function does not
8094 specify the function unambiguously, e.g., if there are several
8095 functions with identical names in different source files.
8099 @section Editing Source Files
8100 @cindex editing source files
8103 @kindex e @r{(@code{edit})}
8104 To edit the lines in a source file, use the @code{edit} command.
8105 The editing program of your choice
8106 is invoked with the current line set to
8107 the active line in the program.
8108 Alternatively, there are several ways to specify what part of the file you
8109 want to print if you want to see other parts of the program:
8112 @item edit @var{location}
8113 Edit the source file specified by @code{location}. Editing starts at
8114 that @var{location}, e.g., at the specified source line of the
8115 specified file. @xref{Specify Location}, for all the possible forms
8116 of the @var{location} argument; here are the forms of the @code{edit}
8117 command most commonly used:
8120 @item edit @var{number}
8121 Edit the current source file with @var{number} as the active line number.
8123 @item edit @var{function}
8124 Edit the file containing @var{function} at the beginning of its definition.
8129 @subsection Choosing your Editor
8130 You can customize @value{GDBN} to use any editor you want
8132 The only restriction is that your editor (say @code{ex}), recognizes the
8133 following command-line syntax:
8135 ex +@var{number} file
8137 The optional numeric value +@var{number} specifies the number of the line in
8138 the file where to start editing.}.
8139 By default, it is @file{@value{EDITOR}}, but you can change this
8140 by setting the environment variable @code{EDITOR} before using
8141 @value{GDBN}. For example, to configure @value{GDBN} to use the
8142 @code{vi} editor, you could use these commands with the @code{sh} shell:
8148 or in the @code{csh} shell,
8150 setenv EDITOR /usr/bin/vi
8155 @section Searching Source Files
8156 @cindex searching source files
8158 There are two commands for searching through the current source file for a
8163 @kindex forward-search
8164 @kindex fo @r{(@code{forward-search})}
8165 @item forward-search @var{regexp}
8166 @itemx search @var{regexp}
8167 The command @samp{forward-search @var{regexp}} checks each line,
8168 starting with the one following the last line listed, for a match for
8169 @var{regexp}. It lists the line that is found. You can use the
8170 synonym @samp{search @var{regexp}} or abbreviate the command name as
8173 @kindex reverse-search
8174 @item reverse-search @var{regexp}
8175 The command @samp{reverse-search @var{regexp}} checks each line, starting
8176 with the one before the last line listed and going backward, for a match
8177 for @var{regexp}. It lists the line that is found. You can abbreviate
8178 this command as @code{rev}.
8182 @section Specifying Source Directories
8185 @cindex directories for source files
8186 Executable programs sometimes do not record the directories of the source
8187 files from which they were compiled, just the names. Even when they do,
8188 the directories could be moved between the compilation and your debugging
8189 session. @value{GDBN} has a list of directories to search for source files;
8190 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8191 it tries all the directories in the list, in the order they are present
8192 in the list, until it finds a file with the desired name.
8194 For example, suppose an executable references the file
8195 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8196 @file{/mnt/cross}. The file is first looked up literally; if this
8197 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8198 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8199 message is printed. @value{GDBN} does not look up the parts of the
8200 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8201 Likewise, the subdirectories of the source path are not searched: if
8202 the source path is @file{/mnt/cross}, and the binary refers to
8203 @file{foo.c}, @value{GDBN} would not find it under
8204 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8206 Plain file names, relative file names with leading directories, file
8207 names containing dots, etc.@: are all treated as described above; for
8208 instance, if the source path is @file{/mnt/cross}, and the source file
8209 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8210 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8211 that---@file{/mnt/cross/foo.c}.
8213 Note that the executable search path is @emph{not} used to locate the
8216 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8217 any information it has cached about where source files are found and where
8218 each line is in the file.
8222 When you start @value{GDBN}, its source path includes only @samp{cdir}
8223 and @samp{cwd}, in that order.
8224 To add other directories, use the @code{directory} command.
8226 The search path is used to find both program source files and @value{GDBN}
8227 script files (read using the @samp{-command} option and @samp{source} command).
8229 In addition to the source path, @value{GDBN} provides a set of commands
8230 that manage a list of source path substitution rules. A @dfn{substitution
8231 rule} specifies how to rewrite source directories stored in the program's
8232 debug information in case the sources were moved to a different
8233 directory between compilation and debugging. A rule is made of
8234 two strings, the first specifying what needs to be rewritten in
8235 the path, and the second specifying how it should be rewritten.
8236 In @ref{set substitute-path}, we name these two parts @var{from} and
8237 @var{to} respectively. @value{GDBN} does a simple string replacement
8238 of @var{from} with @var{to} at the start of the directory part of the
8239 source file name, and uses that result instead of the original file
8240 name to look up the sources.
8242 Using the previous example, suppose the @file{foo-1.0} tree has been
8243 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8244 @value{GDBN} to replace @file{/usr/src} in all source path names with
8245 @file{/mnt/cross}. The first lookup will then be
8246 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8247 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8248 substitution rule, use the @code{set substitute-path} command
8249 (@pxref{set substitute-path}).
8251 To avoid unexpected substitution results, a rule is applied only if the
8252 @var{from} part of the directory name ends at a directory separator.
8253 For instance, a rule substituting @file{/usr/source} into
8254 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8255 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8256 is applied only at the beginning of the directory name, this rule will
8257 not be applied to @file{/root/usr/source/baz.c} either.
8259 In many cases, you can achieve the same result using the @code{directory}
8260 command. However, @code{set substitute-path} can be more efficient in
8261 the case where the sources are organized in a complex tree with multiple
8262 subdirectories. With the @code{directory} command, you need to add each
8263 subdirectory of your project. If you moved the entire tree while
8264 preserving its internal organization, then @code{set substitute-path}
8265 allows you to direct the debugger to all the sources with one single
8268 @code{set substitute-path} is also more than just a shortcut command.
8269 The source path is only used if the file at the original location no
8270 longer exists. On the other hand, @code{set substitute-path} modifies
8271 the debugger behavior to look at the rewritten location instead. So, if
8272 for any reason a source file that is not relevant to your executable is
8273 located at the original location, a substitution rule is the only
8274 method available to point @value{GDBN} at the new location.
8276 @cindex @samp{--with-relocated-sources}
8277 @cindex default source path substitution
8278 You can configure a default source path substitution rule by
8279 configuring @value{GDBN} with the
8280 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8281 should be the name of a directory under @value{GDBN}'s configured
8282 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8283 directory names in debug information under @var{dir} will be adjusted
8284 automatically if the installed @value{GDBN} is moved to a new
8285 location. This is useful if @value{GDBN}, libraries or executables
8286 with debug information and corresponding source code are being moved
8290 @item directory @var{dirname} @dots{}
8291 @item dir @var{dirname} @dots{}
8292 Add directory @var{dirname} to the front of the source path. Several
8293 directory names may be given to this command, separated by @samp{:}
8294 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8295 part of absolute file names) or
8296 whitespace. You may specify a directory that is already in the source
8297 path; this moves it forward, so @value{GDBN} searches it sooner.
8301 @vindex $cdir@r{, convenience variable}
8302 @vindex $cwd@r{, convenience variable}
8303 @cindex compilation directory
8304 @cindex current directory
8305 @cindex working directory
8306 @cindex directory, current
8307 @cindex directory, compilation
8308 You can use the string @samp{$cdir} to refer to the compilation
8309 directory (if one is recorded), and @samp{$cwd} to refer to the current
8310 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8311 tracks the current working directory as it changes during your @value{GDBN}
8312 session, while the latter is immediately expanded to the current
8313 directory at the time you add an entry to the source path.
8316 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8318 @c RET-repeat for @code{directory} is explicitly disabled, but since
8319 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8321 @item set directories @var{path-list}
8322 @kindex set directories
8323 Set the source path to @var{path-list}.
8324 @samp{$cdir:$cwd} are added if missing.
8326 @item show directories
8327 @kindex show directories
8328 Print the source path: show which directories it contains.
8330 @anchor{set substitute-path}
8331 @item set substitute-path @var{from} @var{to}
8332 @kindex set substitute-path
8333 Define a source path substitution rule, and add it at the end of the
8334 current list of existing substitution rules. If a rule with the same
8335 @var{from} was already defined, then the old rule is also deleted.
8337 For example, if the file @file{/foo/bar/baz.c} was moved to
8338 @file{/mnt/cross/baz.c}, then the command
8341 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8345 will tell @value{GDBN} to replace @samp{/foo/bar} with
8346 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8347 @file{baz.c} even though it was moved.
8349 In the case when more than one substitution rule have been defined,
8350 the rules are evaluated one by one in the order where they have been
8351 defined. The first one matching, if any, is selected to perform
8354 For instance, if we had entered the following commands:
8357 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8358 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8362 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8363 @file{/mnt/include/defs.h} by using the first rule. However, it would
8364 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8365 @file{/mnt/src/lib/foo.c}.
8368 @item unset substitute-path [path]
8369 @kindex unset substitute-path
8370 If a path is specified, search the current list of substitution rules
8371 for a rule that would rewrite that path. Delete that rule if found.
8372 A warning is emitted by the debugger if no rule could be found.
8374 If no path is specified, then all substitution rules are deleted.
8376 @item show substitute-path [path]
8377 @kindex show substitute-path
8378 If a path is specified, then print the source path substitution rule
8379 which would rewrite that path, if any.
8381 If no path is specified, then print all existing source path substitution
8386 If your source path is cluttered with directories that are no longer of
8387 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8388 versions of source. You can correct the situation as follows:
8392 Use @code{directory} with no argument to reset the source path to its default value.
8395 Use @code{directory} with suitable arguments to reinstall the
8396 directories you want in the source path. You can add all the
8397 directories in one command.
8401 @section Source and Machine Code
8402 @cindex source line and its code address
8404 You can use the command @code{info line} to map source lines to program
8405 addresses (and vice versa), and the command @code{disassemble} to display
8406 a range of addresses as machine instructions. You can use the command
8407 @code{set disassemble-next-line} to set whether to disassemble next
8408 source line when execution stops. When run under @sc{gnu} Emacs
8409 mode, the @code{info line} command causes the arrow to point to the
8410 line specified. Also, @code{info line} prints addresses in symbolic form as
8415 @item info line @var{location}
8416 Print the starting and ending addresses of the compiled code for
8417 source line @var{location}. You can specify source lines in any of
8418 the ways documented in @ref{Specify Location}.
8421 For example, we can use @code{info line} to discover the location of
8422 the object code for the first line of function
8423 @code{m4_changequote}:
8425 @c FIXME: I think this example should also show the addresses in
8426 @c symbolic form, as they usually would be displayed.
8428 (@value{GDBP}) info line m4_changequote
8429 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8433 @cindex code address and its source line
8434 We can also inquire (using @code{*@var{addr}} as the form for
8435 @var{location}) what source line covers a particular address:
8437 (@value{GDBP}) info line *0x63ff
8438 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8441 @cindex @code{$_} and @code{info line}
8442 @cindex @code{x} command, default address
8443 @kindex x@r{(examine), and} info line
8444 After @code{info line}, the default address for the @code{x} command
8445 is changed to the starting address of the line, so that @samp{x/i} is
8446 sufficient to begin examining the machine code (@pxref{Memory,
8447 ,Examining Memory}). Also, this address is saved as the value of the
8448 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8453 @cindex assembly instructions
8454 @cindex instructions, assembly
8455 @cindex machine instructions
8456 @cindex listing machine instructions
8458 @itemx disassemble /m
8459 @itemx disassemble /s
8460 @itemx disassemble /r
8461 This specialized command dumps a range of memory as machine
8462 instructions. It can also print mixed source+disassembly by specifying
8463 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8464 as well as in symbolic form by specifying the @code{/r} modifier.
8465 The default memory range is the function surrounding the
8466 program counter of the selected frame. A single argument to this
8467 command is a program counter value; @value{GDBN} dumps the function
8468 surrounding this value. When two arguments are given, they should
8469 be separated by a comma, possibly surrounded by whitespace. The
8470 arguments specify a range of addresses to dump, in one of two forms:
8473 @item @var{start},@var{end}
8474 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8475 @item @var{start},+@var{length}
8476 the addresses from @var{start} (inclusive) to
8477 @code{@var{start}+@var{length}} (exclusive).
8481 When 2 arguments are specified, the name of the function is also
8482 printed (since there could be several functions in the given range).
8484 The argument(s) can be any expression yielding a numeric value, such as
8485 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8487 If the range of memory being disassembled contains current program counter,
8488 the instruction at that location is shown with a @code{=>} marker.
8491 The following example shows the disassembly of a range of addresses of
8492 HP PA-RISC 2.0 code:
8495 (@value{GDBP}) disas 0x32c4, 0x32e4
8496 Dump of assembler code from 0x32c4 to 0x32e4:
8497 0x32c4 <main+204>: addil 0,dp
8498 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8499 0x32cc <main+212>: ldil 0x3000,r31
8500 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8501 0x32d4 <main+220>: ldo 0(r31),rp
8502 0x32d8 <main+224>: addil -0x800,dp
8503 0x32dc <main+228>: ldo 0x588(r1),r26
8504 0x32e0 <main+232>: ldil 0x3000,r31
8505 End of assembler dump.
8508 Here is an example showing mixed source+assembly for Intel x86
8509 with @code{/m} or @code{/s}, when the program is stopped just after
8510 function prologue in a non-optimized function with no inline code.
8513 (@value{GDBP}) disas /m main
8514 Dump of assembler code for function main:
8516 0x08048330 <+0>: push %ebp
8517 0x08048331 <+1>: mov %esp,%ebp
8518 0x08048333 <+3>: sub $0x8,%esp
8519 0x08048336 <+6>: and $0xfffffff0,%esp
8520 0x08048339 <+9>: sub $0x10,%esp
8522 6 printf ("Hello.\n");
8523 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8524 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8528 0x08048348 <+24>: mov $0x0,%eax
8529 0x0804834d <+29>: leave
8530 0x0804834e <+30>: ret
8532 End of assembler dump.
8535 The @code{/m} option is deprecated as its output is not useful when
8536 there is either inlined code or re-ordered code.
8537 The @code{/s} option is the preferred choice.
8538 Here is an example for AMD x86-64 showing the difference between
8539 @code{/m} output and @code{/s} output.
8540 This example has one inline function defined in a header file,
8541 and the code is compiled with @samp{-O2} optimization.
8542 Note how the @code{/m} output is missing the disassembly of
8543 several instructions that are present in the @code{/s} output.
8573 (@value{GDBP}) disas /m main
8574 Dump of assembler code for function main:
8578 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8579 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8583 0x000000000040041d <+29>: xor %eax,%eax
8584 0x000000000040041f <+31>: retq
8585 0x0000000000400420 <+32>: add %eax,%eax
8586 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8588 End of assembler dump.
8589 (@value{GDBP}) disas /s main
8590 Dump of assembler code for function main:
8594 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8598 0x0000000000400406 <+6>: test %eax,%eax
8599 0x0000000000400408 <+8>: js 0x400420 <main+32>
8604 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8605 0x000000000040040d <+13>: test %eax,%eax
8606 0x000000000040040f <+15>: mov $0x1,%eax
8607 0x0000000000400414 <+20>: cmovne %edx,%eax
8611 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8615 0x000000000040041d <+29>: xor %eax,%eax
8616 0x000000000040041f <+31>: retq
8620 0x0000000000400420 <+32>: add %eax,%eax
8621 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8622 End of assembler dump.
8625 Here is another example showing raw instructions in hex for AMD x86-64,
8628 (gdb) disas /r 0x400281,+10
8629 Dump of assembler code from 0x400281 to 0x40028b:
8630 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8631 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8632 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8633 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8634 End of assembler dump.
8637 Addresses cannot be specified as a location (@pxref{Specify Location}).
8638 So, for example, if you want to disassemble function @code{bar}
8639 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8640 and not @samp{disassemble foo.c:bar}.
8642 Some architectures have more than one commonly-used set of instruction
8643 mnemonics or other syntax.
8645 For programs that were dynamically linked and use shared libraries,
8646 instructions that call functions or branch to locations in the shared
8647 libraries might show a seemingly bogus location---it's actually a
8648 location of the relocation table. On some architectures, @value{GDBN}
8649 might be able to resolve these to actual function names.
8652 @kindex set disassembler-options
8653 @cindex disassembler options
8654 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8655 This command controls the passing of target specific information to
8656 the disassembler. For a list of valid options, please refer to the
8657 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8658 manual and/or the output of @kbd{objdump --help}
8659 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8660 The default value is the empty string.
8662 If it is necessary to specify more than one disassembler option, then
8663 multiple options can be placed together into a comma separated list.
8664 Currently this command is only supported on targets ARM, PowerPC
8667 @kindex show disassembler-options
8668 @item show disassembler-options
8669 Show the current setting of the disassembler options.
8673 @kindex set disassembly-flavor
8674 @cindex Intel disassembly flavor
8675 @cindex AT&T disassembly flavor
8676 @item set disassembly-flavor @var{instruction-set}
8677 Select the instruction set to use when disassembling the
8678 program via the @code{disassemble} or @code{x/i} commands.
8680 Currently this command is only defined for the Intel x86 family. You
8681 can set @var{instruction-set} to either @code{intel} or @code{att}.
8682 The default is @code{att}, the AT&T flavor used by default by Unix
8683 assemblers for x86-based targets.
8685 @kindex show disassembly-flavor
8686 @item show disassembly-flavor
8687 Show the current setting of the disassembly flavor.
8691 @kindex set disassemble-next-line
8692 @kindex show disassemble-next-line
8693 @item set disassemble-next-line
8694 @itemx show disassemble-next-line
8695 Control whether or not @value{GDBN} will disassemble the next source
8696 line or instruction when execution stops. If ON, @value{GDBN} will
8697 display disassembly of the next source line when execution of the
8698 program being debugged stops. This is @emph{in addition} to
8699 displaying the source line itself, which @value{GDBN} always does if
8700 possible. If the next source line cannot be displayed for some reason
8701 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8702 info in the debug info), @value{GDBN} will display disassembly of the
8703 next @emph{instruction} instead of showing the next source line. If
8704 AUTO, @value{GDBN} will display disassembly of next instruction only
8705 if the source line cannot be displayed. This setting causes
8706 @value{GDBN} to display some feedback when you step through a function
8707 with no line info or whose source file is unavailable. The default is
8708 OFF, which means never display the disassembly of the next line or
8714 @chapter Examining Data
8716 @cindex printing data
8717 @cindex examining data
8720 The usual way to examine data in your program is with the @code{print}
8721 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8722 evaluates and prints the value of an expression of the language your
8723 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8724 Different Languages}). It may also print the expression using a
8725 Python-based pretty-printer (@pxref{Pretty Printing}).
8728 @item print @var{expr}
8729 @itemx print /@var{f} @var{expr}
8730 @var{expr} is an expression (in the source language). By default the
8731 value of @var{expr} is printed in a format appropriate to its data type;
8732 you can choose a different format by specifying @samp{/@var{f}}, where
8733 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8737 @itemx print /@var{f}
8738 @cindex reprint the last value
8739 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8740 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8741 conveniently inspect the same value in an alternative format.
8744 A more low-level way of examining data is with the @code{x} command.
8745 It examines data in memory at a specified address and prints it in a
8746 specified format. @xref{Memory, ,Examining Memory}.
8748 If you are interested in information about types, or about how the
8749 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8750 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8753 @cindex exploring hierarchical data structures
8755 Another way of examining values of expressions and type information is
8756 through the Python extension command @code{explore} (available only if
8757 the @value{GDBN} build is configured with @code{--with-python}). It
8758 offers an interactive way to start at the highest level (or, the most
8759 abstract level) of the data type of an expression (or, the data type
8760 itself) and explore all the way down to leaf scalar values/fields
8761 embedded in the higher level data types.
8764 @item explore @var{arg}
8765 @var{arg} is either an expression (in the source language), or a type
8766 visible in the current context of the program being debugged.
8769 The working of the @code{explore} command can be illustrated with an
8770 example. If a data type @code{struct ComplexStruct} is defined in your
8780 struct ComplexStruct
8782 struct SimpleStruct *ss_p;
8788 followed by variable declarations as
8791 struct SimpleStruct ss = @{ 10, 1.11 @};
8792 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8796 then, the value of the variable @code{cs} can be explored using the
8797 @code{explore} command as follows.
8801 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8802 the following fields:
8804 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8805 arr = <Enter 1 to explore this field of type `int [10]'>
8807 Enter the field number of choice:
8811 Since the fields of @code{cs} are not scalar values, you are being
8812 prompted to chose the field you want to explore. Let's say you choose
8813 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8814 pointer, you will be asked if it is pointing to a single value. From
8815 the declaration of @code{cs} above, it is indeed pointing to a single
8816 value, hence you enter @code{y}. If you enter @code{n}, then you will
8817 be asked if it were pointing to an array of values, in which case this
8818 field will be explored as if it were an array.
8821 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8822 Continue exploring it as a pointer to a single value [y/n]: y
8823 The value of `*(cs.ss_p)' is a struct/class of type `struct
8824 SimpleStruct' with the following fields:
8826 i = 10 .. (Value of type `int')
8827 d = 1.1100000000000001 .. (Value of type `double')
8829 Press enter to return to parent value:
8833 If the field @code{arr} of @code{cs} was chosen for exploration by
8834 entering @code{1} earlier, then since it is as array, you will be
8835 prompted to enter the index of the element in the array that you want
8839 `cs.arr' is an array of `int'.
8840 Enter the index of the element you want to explore in `cs.arr': 5
8842 `(cs.arr)[5]' is a scalar value of type `int'.
8846 Press enter to return to parent value:
8849 In general, at any stage of exploration, you can go deeper towards the
8850 leaf values by responding to the prompts appropriately, or hit the
8851 return key to return to the enclosing data structure (the @i{higher}
8852 level data structure).
8854 Similar to exploring values, you can use the @code{explore} command to
8855 explore types. Instead of specifying a value (which is typically a
8856 variable name or an expression valid in the current context of the
8857 program being debugged), you specify a type name. If you consider the
8858 same example as above, your can explore the type
8859 @code{struct ComplexStruct} by passing the argument
8860 @code{struct ComplexStruct} to the @code{explore} command.
8863 (gdb) explore struct ComplexStruct
8867 By responding to the prompts appropriately in the subsequent interactive
8868 session, you can explore the type @code{struct ComplexStruct} in a
8869 manner similar to how the value @code{cs} was explored in the above
8872 The @code{explore} command also has two sub-commands,
8873 @code{explore value} and @code{explore type}. The former sub-command is
8874 a way to explicitly specify that value exploration of the argument is
8875 being invoked, while the latter is a way to explicitly specify that type
8876 exploration of the argument is being invoked.
8879 @item explore value @var{expr}
8880 @cindex explore value
8881 This sub-command of @code{explore} explores the value of the
8882 expression @var{expr} (if @var{expr} is an expression valid in the
8883 current context of the program being debugged). The behavior of this
8884 command is identical to that of the behavior of the @code{explore}
8885 command being passed the argument @var{expr}.
8887 @item explore type @var{arg}
8888 @cindex explore type
8889 This sub-command of @code{explore} explores the type of @var{arg} (if
8890 @var{arg} is a type visible in the current context of program being
8891 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8892 is an expression valid in the current context of the program being
8893 debugged). If @var{arg} is a type, then the behavior of this command is
8894 identical to that of the @code{explore} command being passed the
8895 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8896 this command will be identical to that of the @code{explore} command
8897 being passed the type of @var{arg} as the argument.
8901 * Expressions:: Expressions
8902 * Ambiguous Expressions:: Ambiguous Expressions
8903 * Variables:: Program variables
8904 * Arrays:: Artificial arrays
8905 * Output Formats:: Output formats
8906 * Memory:: Examining memory
8907 * Auto Display:: Automatic display
8908 * Print Settings:: Print settings
8909 * Pretty Printing:: Python pretty printing
8910 * Value History:: Value history
8911 * Convenience Vars:: Convenience variables
8912 * Convenience Funs:: Convenience functions
8913 * Registers:: Registers
8914 * Floating Point Hardware:: Floating point hardware
8915 * Vector Unit:: Vector Unit
8916 * OS Information:: Auxiliary data provided by operating system
8917 * Memory Region Attributes:: Memory region attributes
8918 * Dump/Restore Files:: Copy between memory and a file
8919 * Core File Generation:: Cause a program dump its core
8920 * Character Sets:: Debugging programs that use a different
8921 character set than GDB does
8922 * Caching Target Data:: Data caching for targets
8923 * Searching Memory:: Searching memory for a sequence of bytes
8924 * Value Sizes:: Managing memory allocated for values
8928 @section Expressions
8931 @code{print} and many other @value{GDBN} commands accept an expression and
8932 compute its value. Any kind of constant, variable or operator defined
8933 by the programming language you are using is valid in an expression in
8934 @value{GDBN}. This includes conditional expressions, function calls,
8935 casts, and string constants. It also includes preprocessor macros, if
8936 you compiled your program to include this information; see
8939 @cindex arrays in expressions
8940 @value{GDBN} supports array constants in expressions input by
8941 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8942 you can use the command @code{print @{1, 2, 3@}} to create an array
8943 of three integers. If you pass an array to a function or assign it
8944 to a program variable, @value{GDBN} copies the array to memory that
8945 is @code{malloc}ed in the target program.
8947 Because C is so widespread, most of the expressions shown in examples in
8948 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8949 Languages}, for information on how to use expressions in other
8952 In this section, we discuss operators that you can use in @value{GDBN}
8953 expressions regardless of your programming language.
8955 @cindex casts, in expressions
8956 Casts are supported in all languages, not just in C, because it is so
8957 useful to cast a number into a pointer in order to examine a structure
8958 at that address in memory.
8959 @c FIXME: casts supported---Mod2 true?
8961 @value{GDBN} supports these operators, in addition to those common
8962 to programming languages:
8966 @samp{@@} is a binary operator for treating parts of memory as arrays.
8967 @xref{Arrays, ,Artificial Arrays}, for more information.
8970 @samp{::} allows you to specify a variable in terms of the file or
8971 function where it is defined. @xref{Variables, ,Program Variables}.
8973 @cindex @{@var{type}@}
8974 @cindex type casting memory
8975 @cindex memory, viewing as typed object
8976 @cindex casts, to view memory
8977 @item @{@var{type}@} @var{addr}
8978 Refers to an object of type @var{type} stored at address @var{addr} in
8979 memory. The address @var{addr} may be any expression whose value is
8980 an integer or pointer (but parentheses are required around binary
8981 operators, just as in a cast). This construct is allowed regardless
8982 of what kind of data is normally supposed to reside at @var{addr}.
8985 @node Ambiguous Expressions
8986 @section Ambiguous Expressions
8987 @cindex ambiguous expressions
8989 Expressions can sometimes contain some ambiguous elements. For instance,
8990 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8991 a single function name to be defined several times, for application in
8992 different contexts. This is called @dfn{overloading}. Another example
8993 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8994 templates and is typically instantiated several times, resulting in
8995 the same function name being defined in different contexts.
8997 In some cases and depending on the language, it is possible to adjust
8998 the expression to remove the ambiguity. For instance in C@t{++}, you
8999 can specify the signature of the function you want to break on, as in
9000 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9001 qualified name of your function often makes the expression unambiguous
9004 When an ambiguity that needs to be resolved is detected, the debugger
9005 has the capability to display a menu of numbered choices for each
9006 possibility, and then waits for the selection with the prompt @samp{>}.
9007 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9008 aborts the current command. If the command in which the expression was
9009 used allows more than one choice to be selected, the next option in the
9010 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9013 For example, the following session excerpt shows an attempt to set a
9014 breakpoint at the overloaded symbol @code{String::after}.
9015 We choose three particular definitions of that function name:
9017 @c FIXME! This is likely to change to show arg type lists, at least
9020 (@value{GDBP}) b String::after
9023 [2] file:String.cc; line number:867
9024 [3] file:String.cc; line number:860
9025 [4] file:String.cc; line number:875
9026 [5] file:String.cc; line number:853
9027 [6] file:String.cc; line number:846
9028 [7] file:String.cc; line number:735
9030 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9031 Breakpoint 2 at 0xb344: file String.cc, line 875.
9032 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9033 Multiple breakpoints were set.
9034 Use the "delete" command to delete unwanted
9041 @kindex set multiple-symbols
9042 @item set multiple-symbols @var{mode}
9043 @cindex multiple-symbols menu
9045 This option allows you to adjust the debugger behavior when an expression
9048 By default, @var{mode} is set to @code{all}. If the command with which
9049 the expression is used allows more than one choice, then @value{GDBN}
9050 automatically selects all possible choices. For instance, inserting
9051 a breakpoint on a function using an ambiguous name results in a breakpoint
9052 inserted on each possible match. However, if a unique choice must be made,
9053 then @value{GDBN} uses the menu to help you disambiguate the expression.
9054 For instance, printing the address of an overloaded function will result
9055 in the use of the menu.
9057 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9058 when an ambiguity is detected.
9060 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9061 an error due to the ambiguity and the command is aborted.
9063 @kindex show multiple-symbols
9064 @item show multiple-symbols
9065 Show the current value of the @code{multiple-symbols} setting.
9069 @section Program Variables
9071 The most common kind of expression to use is the name of a variable
9074 Variables in expressions are understood in the selected stack frame
9075 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9079 global (or file-static)
9086 visible according to the scope rules of the
9087 programming language from the point of execution in that frame
9090 @noindent This means that in the function
9105 you can examine and use the variable @code{a} whenever your program is
9106 executing within the function @code{foo}, but you can only use or
9107 examine the variable @code{b} while your program is executing inside
9108 the block where @code{b} is declared.
9110 @cindex variable name conflict
9111 There is an exception: you can refer to a variable or function whose
9112 scope is a single source file even if the current execution point is not
9113 in this file. But it is possible to have more than one such variable or
9114 function with the same name (in different source files). If that
9115 happens, referring to that name has unpredictable effects. If you wish,
9116 you can specify a static variable in a particular function or file by
9117 using the colon-colon (@code{::}) notation:
9119 @cindex colon-colon, context for variables/functions
9121 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9122 @cindex @code{::}, context for variables/functions
9125 @var{file}::@var{variable}
9126 @var{function}::@var{variable}
9130 Here @var{file} or @var{function} is the name of the context for the
9131 static @var{variable}. In the case of file names, you can use quotes to
9132 make sure @value{GDBN} parses the file name as a single word---for example,
9133 to print a global value of @code{x} defined in @file{f2.c}:
9136 (@value{GDBP}) p 'f2.c'::x
9139 The @code{::} notation is normally used for referring to
9140 static variables, since you typically disambiguate uses of local variables
9141 in functions by selecting the appropriate frame and using the
9142 simple name of the variable. However, you may also use this notation
9143 to refer to local variables in frames enclosing the selected frame:
9152 process (a); /* Stop here */
9163 For example, if there is a breakpoint at the commented line,
9164 here is what you might see
9165 when the program stops after executing the call @code{bar(0)}:
9170 (@value{GDBP}) p bar::a
9173 #2 0x080483d0 in foo (a=5) at foobar.c:12
9176 (@value{GDBP}) p bar::a
9180 @cindex C@t{++} scope resolution
9181 These uses of @samp{::} are very rarely in conflict with the very
9182 similar use of the same notation in C@t{++}. When they are in
9183 conflict, the C@t{++} meaning takes precedence; however, this can be
9184 overridden by quoting the file or function name with single quotes.
9186 For example, suppose the program is stopped in a method of a class
9187 that has a field named @code{includefile}, and there is also an
9188 include file named @file{includefile} that defines a variable,
9192 (@value{GDBP}) p includefile
9194 (@value{GDBP}) p includefile::some_global
9195 A syntax error in expression, near `'.
9196 (@value{GDBP}) p 'includefile'::some_global
9200 @cindex wrong values
9201 @cindex variable values, wrong
9202 @cindex function entry/exit, wrong values of variables
9203 @cindex optimized code, wrong values of variables
9205 @emph{Warning:} Occasionally, a local variable may appear to have the
9206 wrong value at certain points in a function---just after entry to a new
9207 scope, and just before exit.
9209 You may see this problem when you are stepping by machine instructions.
9210 This is because, on most machines, it takes more than one instruction to
9211 set up a stack frame (including local variable definitions); if you are
9212 stepping by machine instructions, variables may appear to have the wrong
9213 values until the stack frame is completely built. On exit, it usually
9214 also takes more than one machine instruction to destroy a stack frame;
9215 after you begin stepping through that group of instructions, local
9216 variable definitions may be gone.
9218 This may also happen when the compiler does significant optimizations.
9219 To be sure of always seeing accurate values, turn off all optimization
9222 @cindex ``No symbol "foo" in current context''
9223 Another possible effect of compiler optimizations is to optimize
9224 unused variables out of existence, or assign variables to registers (as
9225 opposed to memory addresses). Depending on the support for such cases
9226 offered by the debug info format used by the compiler, @value{GDBN}
9227 might not be able to display values for such local variables. If that
9228 happens, @value{GDBN} will print a message like this:
9231 No symbol "foo" in current context.
9234 To solve such problems, either recompile without optimizations, or use a
9235 different debug info format, if the compiler supports several such
9236 formats. @xref{Compilation}, for more information on choosing compiler
9237 options. @xref{C, ,C and C@t{++}}, for more information about debug
9238 info formats that are best suited to C@t{++} programs.
9240 If you ask to print an object whose contents are unknown to
9241 @value{GDBN}, e.g., because its data type is not completely specified
9242 by the debug information, @value{GDBN} will say @samp{<incomplete
9243 type>}. @xref{Symbols, incomplete type}, for more about this.
9245 @cindex no debug info variables
9246 If you try to examine or use the value of a (global) variable for
9247 which @value{GDBN} has no type information, e.g., because the program
9248 includes no debug information, @value{GDBN} displays an error message.
9249 @xref{Symbols, unknown type}, for more about unknown types. If you
9250 cast the variable to its declared type, @value{GDBN} gets the
9251 variable's value using the cast-to type as the variable's type. For
9252 example, in a C program:
9255 (@value{GDBP}) p var
9256 'var' has unknown type; cast it to its declared type
9257 (@value{GDBP}) p (float) var
9261 If you append @kbd{@@entry} string to a function parameter name you get its
9262 value at the time the function got called. If the value is not available an
9263 error message is printed. Entry values are available only with some compilers.
9264 Entry values are normally also printed at the function parameter list according
9265 to @ref{set print entry-values}.
9268 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9274 (gdb) print i@@entry
9278 Strings are identified as arrays of @code{char} values without specified
9279 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9280 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9281 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9282 defines literal string type @code{"char"} as @code{char} without a sign.
9287 signed char var1[] = "A";
9290 You get during debugging
9295 $2 = @{65 'A', 0 '\0'@}
9299 @section Artificial Arrays
9301 @cindex artificial array
9303 @kindex @@@r{, referencing memory as an array}
9304 It is often useful to print out several successive objects of the
9305 same type in memory; a section of an array, or an array of
9306 dynamically determined size for which only a pointer exists in the
9309 You can do this by referring to a contiguous span of memory as an
9310 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9311 operand of @samp{@@} should be the first element of the desired array
9312 and be an individual object. The right operand should be the desired length
9313 of the array. The result is an array value whose elements are all of
9314 the type of the left argument. The first element is actually the left
9315 argument; the second element comes from bytes of memory immediately
9316 following those that hold the first element, and so on. Here is an
9317 example. If a program says
9320 int *array = (int *) malloc (len * sizeof (int));
9324 you can print the contents of @code{array} with
9330 The left operand of @samp{@@} must reside in memory. Array values made
9331 with @samp{@@} in this way behave just like other arrays in terms of
9332 subscripting, and are coerced to pointers when used in expressions.
9333 Artificial arrays most often appear in expressions via the value history
9334 (@pxref{Value History, ,Value History}), after printing one out.
9336 Another way to create an artificial array is to use a cast.
9337 This re-interprets a value as if it were an array.
9338 The value need not be in memory:
9340 (@value{GDBP}) p/x (short[2])0x12345678
9341 $1 = @{0x1234, 0x5678@}
9344 As a convenience, if you leave the array length out (as in
9345 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9346 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9348 (@value{GDBP}) p/x (short[])0x12345678
9349 $2 = @{0x1234, 0x5678@}
9352 Sometimes the artificial array mechanism is not quite enough; in
9353 moderately complex data structures, the elements of interest may not
9354 actually be adjacent---for example, if you are interested in the values
9355 of pointers in an array. One useful work-around in this situation is
9356 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9357 Variables}) as a counter in an expression that prints the first
9358 interesting value, and then repeat that expression via @key{RET}. For
9359 instance, suppose you have an array @code{dtab} of pointers to
9360 structures, and you are interested in the values of a field @code{fv}
9361 in each structure. Here is an example of what you might type:
9371 @node Output Formats
9372 @section Output Formats
9374 @cindex formatted output
9375 @cindex output formats
9376 By default, @value{GDBN} prints a value according to its data type. Sometimes
9377 this is not what you want. For example, you might want to print a number
9378 in hex, or a pointer in decimal. Or you might want to view data in memory
9379 at a certain address as a character string or as an instruction. To do
9380 these things, specify an @dfn{output format} when you print a value.
9382 The simplest use of output formats is to say how to print a value
9383 already computed. This is done by starting the arguments of the
9384 @code{print} command with a slash and a format letter. The format
9385 letters supported are:
9389 Regard the bits of the value as an integer, and print the integer in
9393 Print as integer in signed decimal.
9396 Print as integer in unsigned decimal.
9399 Print as integer in octal.
9402 Print as integer in binary. The letter @samp{t} stands for ``two''.
9403 @footnote{@samp{b} cannot be used because these format letters are also
9404 used with the @code{x} command, where @samp{b} stands for ``byte'';
9405 see @ref{Memory,,Examining Memory}.}
9408 @cindex unknown address, locating
9409 @cindex locate address
9410 Print as an address, both absolute in hexadecimal and as an offset from
9411 the nearest preceding symbol. You can use this format used to discover
9412 where (in what function) an unknown address is located:
9415 (@value{GDBP}) p/a 0x54320
9416 $3 = 0x54320 <_initialize_vx+396>
9420 The command @code{info symbol 0x54320} yields similar results.
9421 @xref{Symbols, info symbol}.
9424 Regard as an integer and print it as a character constant. This
9425 prints both the numerical value and its character representation. The
9426 character representation is replaced with the octal escape @samp{\nnn}
9427 for characters outside the 7-bit @sc{ascii} range.
9429 Without this format, @value{GDBN} displays @code{char},
9430 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9431 constants. Single-byte members of vectors are displayed as integer
9435 Regard the bits of the value as a floating point number and print
9436 using typical floating point syntax.
9439 @cindex printing strings
9440 @cindex printing byte arrays
9441 Regard as a string, if possible. With this format, pointers to single-byte
9442 data are displayed as null-terminated strings and arrays of single-byte data
9443 are displayed as fixed-length strings. Other values are displayed in their
9446 Without this format, @value{GDBN} displays pointers to and arrays of
9447 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9448 strings. Single-byte members of a vector are displayed as an integer
9452 Like @samp{x} formatting, the value is treated as an integer and
9453 printed as hexadecimal, but leading zeros are printed to pad the value
9454 to the size of the integer type.
9457 @cindex raw printing
9458 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9459 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9460 Printing}). This typically results in a higher-level display of the
9461 value's contents. The @samp{r} format bypasses any Python
9462 pretty-printer which might exist.
9465 For example, to print the program counter in hex (@pxref{Registers}), type
9472 Note that no space is required before the slash; this is because command
9473 names in @value{GDBN} cannot contain a slash.
9475 To reprint the last value in the value history with a different format,
9476 you can use the @code{print} command with just a format and no
9477 expression. For example, @samp{p/x} reprints the last value in hex.
9480 @section Examining Memory
9482 You can use the command @code{x} (for ``examine'') to examine memory in
9483 any of several formats, independently of your program's data types.
9485 @cindex examining memory
9487 @kindex x @r{(examine memory)}
9488 @item x/@var{nfu} @var{addr}
9491 Use the @code{x} command to examine memory.
9494 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9495 much memory to display and how to format it; @var{addr} is an
9496 expression giving the address where you want to start displaying memory.
9497 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9498 Several commands set convenient defaults for @var{addr}.
9501 @item @var{n}, the repeat count
9502 The repeat count is a decimal integer; the default is 1. It specifies
9503 how much memory (counting by units @var{u}) to display. If a negative
9504 number is specified, memory is examined backward from @var{addr}.
9505 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9508 @item @var{f}, the display format
9509 The display format is one of the formats used by @code{print}
9510 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9511 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9512 The default is @samp{x} (hexadecimal) initially. The default changes
9513 each time you use either @code{x} or @code{print}.
9515 @item @var{u}, the unit size
9516 The unit size is any of
9522 Halfwords (two bytes).
9524 Words (four bytes). This is the initial default.
9526 Giant words (eight bytes).
9529 Each time you specify a unit size with @code{x}, that size becomes the
9530 default unit the next time you use @code{x}. For the @samp{i} format,
9531 the unit size is ignored and is normally not written. For the @samp{s} format,
9532 the unit size defaults to @samp{b}, unless it is explicitly given.
9533 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9534 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9535 Note that the results depend on the programming language of the
9536 current compilation unit. If the language is C, the @samp{s}
9537 modifier will use the UTF-16 encoding while @samp{w} will use
9538 UTF-32. The encoding is set by the programming language and cannot
9541 @item @var{addr}, starting display address
9542 @var{addr} is the address where you want @value{GDBN} to begin displaying
9543 memory. The expression need not have a pointer value (though it may);
9544 it is always interpreted as an integer address of a byte of memory.
9545 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9546 @var{addr} is usually just after the last address examined---but several
9547 other commands also set the default address: @code{info breakpoints} (to
9548 the address of the last breakpoint listed), @code{info line} (to the
9549 starting address of a line), and @code{print} (if you use it to display
9550 a value from memory).
9553 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9554 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9555 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9556 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9557 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9559 You can also specify a negative repeat count to examine memory backward
9560 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9561 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9563 Since the letters indicating unit sizes are all distinct from the
9564 letters specifying output formats, you do not have to remember whether
9565 unit size or format comes first; either order works. The output
9566 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9567 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9569 Even though the unit size @var{u} is ignored for the formats @samp{s}
9570 and @samp{i}, you might still want to use a count @var{n}; for example,
9571 @samp{3i} specifies that you want to see three machine instructions,
9572 including any operands. For convenience, especially when used with
9573 the @code{display} command, the @samp{i} format also prints branch delay
9574 slot instructions, if any, beyond the count specified, which immediately
9575 follow the last instruction that is within the count. The command
9576 @code{disassemble} gives an alternative way of inspecting machine
9577 instructions; see @ref{Machine Code,,Source and Machine Code}.
9579 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9580 the command displays null-terminated strings or instructions before the given
9581 address as many as the absolute value of the given number. For the @samp{i}
9582 format, we use line number information in the debug info to accurately locate
9583 instruction boundaries while disassembling backward. If line info is not
9584 available, the command stops examining memory with an error message.
9586 All the defaults for the arguments to @code{x} are designed to make it
9587 easy to continue scanning memory with minimal specifications each time
9588 you use @code{x}. For example, after you have inspected three machine
9589 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9590 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9591 the repeat count @var{n} is used again; the other arguments default as
9592 for successive uses of @code{x}.
9594 When examining machine instructions, the instruction at current program
9595 counter is shown with a @code{=>} marker. For example:
9598 (@value{GDBP}) x/5i $pc-6
9599 0x804837f <main+11>: mov %esp,%ebp
9600 0x8048381 <main+13>: push %ecx
9601 0x8048382 <main+14>: sub $0x4,%esp
9602 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9603 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9606 @cindex @code{$_}, @code{$__}, and value history
9607 The addresses and contents printed by the @code{x} command are not saved
9608 in the value history because there is often too much of them and they
9609 would get in the way. Instead, @value{GDBN} makes these values available for
9610 subsequent use in expressions as values of the convenience variables
9611 @code{$_} and @code{$__}. After an @code{x} command, the last address
9612 examined is available for use in expressions in the convenience variable
9613 @code{$_}. The contents of that address, as examined, are available in
9614 the convenience variable @code{$__}.
9616 If the @code{x} command has a repeat count, the address and contents saved
9617 are from the last memory unit printed; this is not the same as the last
9618 address printed if several units were printed on the last line of output.
9620 @anchor{addressable memory unit}
9621 @cindex addressable memory unit
9622 Most targets have an addressable memory unit size of 8 bits. This means
9623 that to each memory address are associated 8 bits of data. Some
9624 targets, however, have other addressable memory unit sizes.
9625 Within @value{GDBN} and this document, the term
9626 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9627 when explicitly referring to a chunk of data of that size. The word
9628 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9629 the addressable memory unit size of the target. For most systems,
9630 addressable memory unit is a synonym of byte.
9632 @cindex remote memory comparison
9633 @cindex target memory comparison
9634 @cindex verify remote memory image
9635 @cindex verify target memory image
9636 When you are debugging a program running on a remote target machine
9637 (@pxref{Remote Debugging}), you may wish to verify the program's image
9638 in the remote machine's memory against the executable file you
9639 downloaded to the target. Or, on any target, you may want to check
9640 whether the program has corrupted its own read-only sections. The
9641 @code{compare-sections} command is provided for such situations.
9644 @kindex compare-sections
9645 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9646 Compare the data of a loadable section @var{section-name} in the
9647 executable file of the program being debugged with the same section in
9648 the target machine's memory, and report any mismatches. With no
9649 arguments, compares all loadable sections. With an argument of
9650 @code{-r}, compares all loadable read-only sections.
9652 Note: for remote targets, this command can be accelerated if the
9653 target supports computing the CRC checksum of a block of memory
9654 (@pxref{qCRC packet}).
9658 @section Automatic Display
9659 @cindex automatic display
9660 @cindex display of expressions
9662 If you find that you want to print the value of an expression frequently
9663 (to see how it changes), you might want to add it to the @dfn{automatic
9664 display list} so that @value{GDBN} prints its value each time your program stops.
9665 Each expression added to the list is given a number to identify it;
9666 to remove an expression from the list, you specify that number.
9667 The automatic display looks like this:
9671 3: bar[5] = (struct hack *) 0x3804
9675 This display shows item numbers, expressions and their current values. As with
9676 displays you request manually using @code{x} or @code{print}, you can
9677 specify the output format you prefer; in fact, @code{display} decides
9678 whether to use @code{print} or @code{x} depending your format
9679 specification---it uses @code{x} if you specify either the @samp{i}
9680 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9684 @item display @var{expr}
9685 Add the expression @var{expr} to the list of expressions to display
9686 each time your program stops. @xref{Expressions, ,Expressions}.
9688 @code{display} does not repeat if you press @key{RET} again after using it.
9690 @item display/@var{fmt} @var{expr}
9691 For @var{fmt} specifying only a display format and not a size or
9692 count, add the expression @var{expr} to the auto-display list but
9693 arrange to display it each time in the specified format @var{fmt}.
9694 @xref{Output Formats,,Output Formats}.
9696 @item display/@var{fmt} @var{addr}
9697 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9698 number of units, add the expression @var{addr} as a memory address to
9699 be examined each time your program stops. Examining means in effect
9700 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9703 For example, @samp{display/i $pc} can be helpful, to see the machine
9704 instruction about to be executed each time execution stops (@samp{$pc}
9705 is a common name for the program counter; @pxref{Registers, ,Registers}).
9708 @kindex delete display
9710 @item undisplay @var{dnums}@dots{}
9711 @itemx delete display @var{dnums}@dots{}
9712 Remove items from the list of expressions to display. Specify the
9713 numbers of the displays that you want affected with the command
9714 argument @var{dnums}. It can be a single display number, one of the
9715 numbers shown in the first field of the @samp{info display} display;
9716 or it could be a range of display numbers, as in @code{2-4}.
9718 @code{undisplay} does not repeat if you press @key{RET} after using it.
9719 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9721 @kindex disable display
9722 @item disable display @var{dnums}@dots{}
9723 Disable the display of item numbers @var{dnums}. A disabled display
9724 item is not printed automatically, but is not forgotten. It may be
9725 enabled again later. Specify the numbers of the displays that you
9726 want affected with the command argument @var{dnums}. It can be a
9727 single display number, one of the numbers shown in the first field of
9728 the @samp{info display} display; or it could be a range of display
9729 numbers, as in @code{2-4}.
9731 @kindex enable display
9732 @item enable display @var{dnums}@dots{}
9733 Enable display of item numbers @var{dnums}. It becomes effective once
9734 again in auto display of its expression, until you specify otherwise.
9735 Specify the numbers of the displays that you want affected with the
9736 command argument @var{dnums}. It can be a single display number, one
9737 of the numbers shown in the first field of the @samp{info display}
9738 display; or it could be a range of display numbers, as in @code{2-4}.
9741 Display the current values of the expressions on the list, just as is
9742 done when your program stops.
9744 @kindex info display
9746 Print the list of expressions previously set up to display
9747 automatically, each one with its item number, but without showing the
9748 values. This includes disabled expressions, which are marked as such.
9749 It also includes expressions which would not be displayed right now
9750 because they refer to automatic variables not currently available.
9753 @cindex display disabled out of scope
9754 If a display expression refers to local variables, then it does not make
9755 sense outside the lexical context for which it was set up. Such an
9756 expression is disabled when execution enters a context where one of its
9757 variables is not defined. For example, if you give the command
9758 @code{display last_char} while inside a function with an argument
9759 @code{last_char}, @value{GDBN} displays this argument while your program
9760 continues to stop inside that function. When it stops elsewhere---where
9761 there is no variable @code{last_char}---the display is disabled
9762 automatically. The next time your program stops where @code{last_char}
9763 is meaningful, you can enable the display expression once again.
9765 @node Print Settings
9766 @section Print Settings
9768 @cindex format options
9769 @cindex print settings
9770 @value{GDBN} provides the following ways to control how arrays, structures,
9771 and symbols are printed.
9774 These settings are useful for debugging programs in any language:
9778 @item set print address
9779 @itemx set print address on
9780 @cindex print/don't print memory addresses
9781 @value{GDBN} prints memory addresses showing the location of stack
9782 traces, structure values, pointer values, breakpoints, and so forth,
9783 even when it also displays the contents of those addresses. The default
9784 is @code{on}. For example, this is what a stack frame display looks like with
9785 @code{set print address on}:
9790 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9792 530 if (lquote != def_lquote)
9796 @item set print address off
9797 Do not print addresses when displaying their contents. For example,
9798 this is the same stack frame displayed with @code{set print address off}:
9802 (@value{GDBP}) set print addr off
9804 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9805 530 if (lquote != def_lquote)
9809 You can use @samp{set print address off} to eliminate all machine
9810 dependent displays from the @value{GDBN} interface. For example, with
9811 @code{print address off}, you should get the same text for backtraces on
9812 all machines---whether or not they involve pointer arguments.
9815 @item show print address
9816 Show whether or not addresses are to be printed.
9819 When @value{GDBN} prints a symbolic address, it normally prints the
9820 closest earlier symbol plus an offset. If that symbol does not uniquely
9821 identify the address (for example, it is a name whose scope is a single
9822 source file), you may need to clarify. One way to do this is with
9823 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9824 you can set @value{GDBN} to print the source file and line number when
9825 it prints a symbolic address:
9828 @item set print symbol-filename on
9829 @cindex source file and line of a symbol
9830 @cindex symbol, source file and line
9831 Tell @value{GDBN} to print the source file name and line number of a
9832 symbol in the symbolic form of an address.
9834 @item set print symbol-filename off
9835 Do not print source file name and line number of a symbol. This is the
9838 @item show print symbol-filename
9839 Show whether or not @value{GDBN} will print the source file name and
9840 line number of a symbol in the symbolic form of an address.
9843 Another situation where it is helpful to show symbol filenames and line
9844 numbers is when disassembling code; @value{GDBN} shows you the line
9845 number and source file that corresponds to each instruction.
9847 Also, you may wish to see the symbolic form only if the address being
9848 printed is reasonably close to the closest earlier symbol:
9851 @item set print max-symbolic-offset @var{max-offset}
9852 @itemx set print max-symbolic-offset unlimited
9853 @cindex maximum value for offset of closest symbol
9854 Tell @value{GDBN} to only display the symbolic form of an address if the
9855 offset between the closest earlier symbol and the address is less than
9856 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9857 to always print the symbolic form of an address if any symbol precedes
9858 it. Zero is equivalent to @code{unlimited}.
9860 @item show print max-symbolic-offset
9861 Ask how large the maximum offset is that @value{GDBN} prints in a
9865 @cindex wild pointer, interpreting
9866 @cindex pointer, finding referent
9867 If you have a pointer and you are not sure where it points, try
9868 @samp{set print symbol-filename on}. Then you can determine the name
9869 and source file location of the variable where it points, using
9870 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9871 For example, here @value{GDBN} shows that a variable @code{ptt} points
9872 at another variable @code{t}, defined in @file{hi2.c}:
9875 (@value{GDBP}) set print symbol-filename on
9876 (@value{GDBP}) p/a ptt
9877 $4 = 0xe008 <t in hi2.c>
9881 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9882 does not show the symbol name and filename of the referent, even with
9883 the appropriate @code{set print} options turned on.
9886 You can also enable @samp{/a}-like formatting all the time using
9887 @samp{set print symbol on}:
9890 @item set print symbol on
9891 Tell @value{GDBN} to print the symbol corresponding to an address, if
9894 @item set print symbol off
9895 Tell @value{GDBN} not to print the symbol corresponding to an
9896 address. In this mode, @value{GDBN} will still print the symbol
9897 corresponding to pointers to functions. This is the default.
9899 @item show print symbol
9900 Show whether @value{GDBN} will display the symbol corresponding to an
9904 Other settings control how different kinds of objects are printed:
9907 @item set print array
9908 @itemx set print array on
9909 @cindex pretty print arrays
9910 Pretty print arrays. This format is more convenient to read,
9911 but uses more space. The default is off.
9913 @item set print array off
9914 Return to compressed format for arrays.
9916 @item show print array
9917 Show whether compressed or pretty format is selected for displaying
9920 @cindex print array indexes
9921 @item set print array-indexes
9922 @itemx set print array-indexes on
9923 Print the index of each element when displaying arrays. May be more
9924 convenient to locate a given element in the array or quickly find the
9925 index of a given element in that printed array. The default is off.
9927 @item set print array-indexes off
9928 Stop printing element indexes when displaying arrays.
9930 @item show print array-indexes
9931 Show whether the index of each element is printed when displaying
9934 @item set print elements @var{number-of-elements}
9935 @itemx set print elements unlimited
9936 @cindex number of array elements to print
9937 @cindex limit on number of printed array elements
9938 Set a limit on how many elements of an array @value{GDBN} will print.
9939 If @value{GDBN} is printing a large array, it stops printing after it has
9940 printed the number of elements set by the @code{set print elements} command.
9941 This limit also applies to the display of strings.
9942 When @value{GDBN} starts, this limit is set to 200.
9943 Setting @var{number-of-elements} to @code{unlimited} or zero means
9944 that the number of elements to print is unlimited.
9946 @item show print elements
9947 Display the number of elements of a large array that @value{GDBN} will print.
9948 If the number is 0, then the printing is unlimited.
9950 @item set print frame-arguments @var{value}
9951 @kindex set print frame-arguments
9952 @cindex printing frame argument values
9953 @cindex print all frame argument values
9954 @cindex print frame argument values for scalars only
9955 @cindex do not print frame argument values
9956 This command allows to control how the values of arguments are printed
9957 when the debugger prints a frame (@pxref{Frames}). The possible
9962 The values of all arguments are printed.
9965 Print the value of an argument only if it is a scalar. The value of more
9966 complex arguments such as arrays, structures, unions, etc, is replaced
9967 by @code{@dots{}}. This is the default. Here is an example where
9968 only scalar arguments are shown:
9971 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9976 None of the argument values are printed. Instead, the value of each argument
9977 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9980 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9985 By default, only scalar arguments are printed. This command can be used
9986 to configure the debugger to print the value of all arguments, regardless
9987 of their type. However, it is often advantageous to not print the value
9988 of more complex parameters. For instance, it reduces the amount of
9989 information printed in each frame, making the backtrace more readable.
9990 Also, it improves performance when displaying Ada frames, because
9991 the computation of large arguments can sometimes be CPU-intensive,
9992 especially in large applications. Setting @code{print frame-arguments}
9993 to @code{scalars} (the default) or @code{none} avoids this computation,
9994 thus speeding up the display of each Ada frame.
9996 @item show print frame-arguments
9997 Show how the value of arguments should be displayed when printing a frame.
9999 @item set print raw frame-arguments on
10000 Print frame arguments in raw, non pretty-printed, form.
10002 @item set print raw frame-arguments off
10003 Print frame arguments in pretty-printed form, if there is a pretty-printer
10004 for the value (@pxref{Pretty Printing}),
10005 otherwise print the value in raw form.
10006 This is the default.
10008 @item show print raw frame-arguments
10009 Show whether to print frame arguments in raw form.
10011 @anchor{set print entry-values}
10012 @item set print entry-values @var{value}
10013 @kindex set print entry-values
10014 Set printing of frame argument values at function entry. In some cases
10015 @value{GDBN} can determine the value of function argument which was passed by
10016 the function caller, even if the value was modified inside the called function
10017 and therefore is different. With optimized code, the current value could be
10018 unavailable, but the entry value may still be known.
10020 The default value is @code{default} (see below for its description). Older
10021 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10022 this feature will behave in the @code{default} setting the same way as with the
10025 This functionality is currently supported only by DWARF 2 debugging format and
10026 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10027 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10030 The @var{value} parameter can be one of the following:
10034 Print only actual parameter values, never print values from function entry
10038 #0 different (val=6)
10039 #0 lost (val=<optimized out>)
10041 #0 invalid (val=<optimized out>)
10045 Print only parameter values from function entry point. The actual parameter
10046 values are never printed.
10048 #0 equal (val@@entry=5)
10049 #0 different (val@@entry=5)
10050 #0 lost (val@@entry=5)
10051 #0 born (val@@entry=<optimized out>)
10052 #0 invalid (val@@entry=<optimized out>)
10056 Print only parameter values from function entry point. If value from function
10057 entry point is not known while the actual value is known, print the actual
10058 value for such parameter.
10060 #0 equal (val@@entry=5)
10061 #0 different (val@@entry=5)
10062 #0 lost (val@@entry=5)
10064 #0 invalid (val@@entry=<optimized out>)
10068 Print actual parameter values. If actual parameter value is not known while
10069 value from function entry point is known, print the entry point value for such
10073 #0 different (val=6)
10074 #0 lost (val@@entry=5)
10076 #0 invalid (val=<optimized out>)
10080 Always print both the actual parameter value and its value from function entry
10081 point, even if values of one or both are not available due to compiler
10084 #0 equal (val=5, val@@entry=5)
10085 #0 different (val=6, val@@entry=5)
10086 #0 lost (val=<optimized out>, val@@entry=5)
10087 #0 born (val=10, val@@entry=<optimized out>)
10088 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10092 Print the actual parameter value if it is known and also its value from
10093 function entry point if it is known. If neither is known, print for the actual
10094 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10095 values are known and identical, print the shortened
10096 @code{param=param@@entry=VALUE} notation.
10098 #0 equal (val=val@@entry=5)
10099 #0 different (val=6, val@@entry=5)
10100 #0 lost (val@@entry=5)
10102 #0 invalid (val=<optimized out>)
10106 Always print the actual parameter value. Print also its value from function
10107 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10108 if both values are known and identical, print the shortened
10109 @code{param=param@@entry=VALUE} notation.
10111 #0 equal (val=val@@entry=5)
10112 #0 different (val=6, val@@entry=5)
10113 #0 lost (val=<optimized out>, val@@entry=5)
10115 #0 invalid (val=<optimized out>)
10119 For analysis messages on possible failures of frame argument values at function
10120 entry resolution see @ref{set debug entry-values}.
10122 @item show print entry-values
10123 Show the method being used for printing of frame argument values at function
10126 @item set print repeats @var{number-of-repeats}
10127 @itemx set print repeats unlimited
10128 @cindex repeated array elements
10129 Set the threshold for suppressing display of repeated array
10130 elements. When the number of consecutive identical elements of an
10131 array exceeds the threshold, @value{GDBN} prints the string
10132 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10133 identical repetitions, instead of displaying the identical elements
10134 themselves. Setting the threshold to @code{unlimited} or zero will
10135 cause all elements to be individually printed. The default threshold
10138 @item show print repeats
10139 Display the current threshold for printing repeated identical
10142 @item set print null-stop
10143 @cindex @sc{null} elements in arrays
10144 Cause @value{GDBN} to stop printing the characters of an array when the first
10145 @sc{null} is encountered. This is useful when large arrays actually
10146 contain only short strings.
10147 The default is off.
10149 @item show print null-stop
10150 Show whether @value{GDBN} stops printing an array on the first
10151 @sc{null} character.
10153 @item set print pretty on
10154 @cindex print structures in indented form
10155 @cindex indentation in structure display
10156 Cause @value{GDBN} to print structures in an indented format with one member
10157 per line, like this:
10172 @item set print pretty off
10173 Cause @value{GDBN} to print structures in a compact format, like this:
10177 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10178 meat = 0x54 "Pork"@}
10183 This is the default format.
10185 @item show print pretty
10186 Show which format @value{GDBN} is using to print structures.
10188 @item set print sevenbit-strings on
10189 @cindex eight-bit characters in strings
10190 @cindex octal escapes in strings
10191 Print using only seven-bit characters; if this option is set,
10192 @value{GDBN} displays any eight-bit characters (in strings or
10193 character values) using the notation @code{\}@var{nnn}. This setting is
10194 best if you are working in English (@sc{ascii}) and you use the
10195 high-order bit of characters as a marker or ``meta'' bit.
10197 @item set print sevenbit-strings off
10198 Print full eight-bit characters. This allows the use of more
10199 international character sets, and is the default.
10201 @item show print sevenbit-strings
10202 Show whether or not @value{GDBN} is printing only seven-bit characters.
10204 @item set print union on
10205 @cindex unions in structures, printing
10206 Tell @value{GDBN} to print unions which are contained in structures
10207 and other unions. This is the default setting.
10209 @item set print union off
10210 Tell @value{GDBN} not to print unions which are contained in
10211 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10214 @item show print union
10215 Ask @value{GDBN} whether or not it will print unions which are contained in
10216 structures and other unions.
10218 For example, given the declarations
10221 typedef enum @{Tree, Bug@} Species;
10222 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10223 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10234 struct thing foo = @{Tree, @{Acorn@}@};
10238 with @code{set print union on} in effect @samp{p foo} would print
10241 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10245 and with @code{set print union off} in effect it would print
10248 $1 = @{it = Tree, form = @{...@}@}
10252 @code{set print union} affects programs written in C-like languages
10258 These settings are of interest when debugging C@t{++} programs:
10261 @cindex demangling C@t{++} names
10262 @item set print demangle
10263 @itemx set print demangle on
10264 Print C@t{++} names in their source form rather than in the encoded
10265 (``mangled'') form passed to the assembler and linker for type-safe
10266 linkage. The default is on.
10268 @item show print demangle
10269 Show whether C@t{++} names are printed in mangled or demangled form.
10271 @item set print asm-demangle
10272 @itemx set print asm-demangle on
10273 Print C@t{++} names in their source form rather than their mangled form, even
10274 in assembler code printouts such as instruction disassemblies.
10275 The default is off.
10277 @item show print asm-demangle
10278 Show whether C@t{++} names in assembly listings are printed in mangled
10281 @cindex C@t{++} symbol decoding style
10282 @cindex symbol decoding style, C@t{++}
10283 @kindex set demangle-style
10284 @item set demangle-style @var{style}
10285 Choose among several encoding schemes used by different compilers to
10286 represent C@t{++} names. The choices for @var{style} are currently:
10290 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10291 This is the default.
10294 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10297 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10300 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10303 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10304 @strong{Warning:} this setting alone is not sufficient to allow
10305 debugging @code{cfront}-generated executables. @value{GDBN} would
10306 require further enhancement to permit that.
10309 If you omit @var{style}, you will see a list of possible formats.
10311 @item show demangle-style
10312 Display the encoding style currently in use for decoding C@t{++} symbols.
10314 @item set print object
10315 @itemx set print object on
10316 @cindex derived type of an object, printing
10317 @cindex display derived types
10318 When displaying a pointer to an object, identify the @emph{actual}
10319 (derived) type of the object rather than the @emph{declared} type, using
10320 the virtual function table. Note that the virtual function table is
10321 required---this feature can only work for objects that have run-time
10322 type identification; a single virtual method in the object's declared
10323 type is sufficient. Note that this setting is also taken into account when
10324 working with variable objects via MI (@pxref{GDB/MI}).
10326 @item set print object off
10327 Display only the declared type of objects, without reference to the
10328 virtual function table. This is the default setting.
10330 @item show print object
10331 Show whether actual, or declared, object types are displayed.
10333 @item set print static-members
10334 @itemx set print static-members on
10335 @cindex static members of C@t{++} objects
10336 Print static members when displaying a C@t{++} object. The default is on.
10338 @item set print static-members off
10339 Do not print static members when displaying a C@t{++} object.
10341 @item show print static-members
10342 Show whether C@t{++} static members are printed or not.
10344 @item set print pascal_static-members
10345 @itemx set print pascal_static-members on
10346 @cindex static members of Pascal objects
10347 @cindex Pascal objects, static members display
10348 Print static members when displaying a Pascal object. The default is on.
10350 @item set print pascal_static-members off
10351 Do not print static members when displaying a Pascal object.
10353 @item show print pascal_static-members
10354 Show whether Pascal static members are printed or not.
10356 @c These don't work with HP ANSI C++ yet.
10357 @item set print vtbl
10358 @itemx set print vtbl on
10359 @cindex pretty print C@t{++} virtual function tables
10360 @cindex virtual functions (C@t{++}) display
10361 @cindex VTBL display
10362 Pretty print C@t{++} virtual function tables. The default is off.
10363 (The @code{vtbl} commands do not work on programs compiled with the HP
10364 ANSI C@t{++} compiler (@code{aCC}).)
10366 @item set print vtbl off
10367 Do not pretty print C@t{++} virtual function tables.
10369 @item show print vtbl
10370 Show whether C@t{++} virtual function tables are pretty printed, or not.
10373 @node Pretty Printing
10374 @section Pretty Printing
10376 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10377 Python code. It greatly simplifies the display of complex objects. This
10378 mechanism works for both MI and the CLI.
10381 * Pretty-Printer Introduction:: Introduction to pretty-printers
10382 * Pretty-Printer Example:: An example pretty-printer
10383 * Pretty-Printer Commands:: Pretty-printer commands
10386 @node Pretty-Printer Introduction
10387 @subsection Pretty-Printer Introduction
10389 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10390 registered for the value. If there is then @value{GDBN} invokes the
10391 pretty-printer to print the value. Otherwise the value is printed normally.
10393 Pretty-printers are normally named. This makes them easy to manage.
10394 The @samp{info pretty-printer} command will list all the installed
10395 pretty-printers with their names.
10396 If a pretty-printer can handle multiple data types, then its
10397 @dfn{subprinters} are the printers for the individual data types.
10398 Each such subprinter has its own name.
10399 The format of the name is @var{printer-name};@var{subprinter-name}.
10401 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10402 Typically they are automatically loaded and registered when the corresponding
10403 debug information is loaded, thus making them available without having to
10404 do anything special.
10406 There are three places where a pretty-printer can be registered.
10410 Pretty-printers registered globally are available when debugging
10414 Pretty-printers registered with a program space are available only
10415 when debugging that program.
10416 @xref{Progspaces In Python}, for more details on program spaces in Python.
10419 Pretty-printers registered with an objfile are loaded and unloaded
10420 with the corresponding objfile (e.g., shared library).
10421 @xref{Objfiles In Python}, for more details on objfiles in Python.
10424 @xref{Selecting Pretty-Printers}, for further information on how
10425 pretty-printers are selected,
10427 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10430 @node Pretty-Printer Example
10431 @subsection Pretty-Printer Example
10433 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10436 (@value{GDBP}) print s
10438 static npos = 4294967295,
10440 <std::allocator<char>> = @{
10441 <__gnu_cxx::new_allocator<char>> = @{
10442 <No data fields>@}, <No data fields>
10444 members of std::basic_string<char, std::char_traits<char>,
10445 std::allocator<char> >::_Alloc_hider:
10446 _M_p = 0x804a014 "abcd"
10451 With a pretty-printer for @code{std::string} only the contents are printed:
10454 (@value{GDBP}) print s
10458 @node Pretty-Printer Commands
10459 @subsection Pretty-Printer Commands
10460 @cindex pretty-printer commands
10463 @kindex info pretty-printer
10464 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10465 Print the list of installed pretty-printers.
10466 This includes disabled pretty-printers, which are marked as such.
10468 @var{object-regexp} is a regular expression matching the objects
10469 whose pretty-printers to list.
10470 Objects can be @code{global}, the program space's file
10471 (@pxref{Progspaces In Python}),
10472 and the object files within that program space (@pxref{Objfiles In Python}).
10473 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10474 looks up a printer from these three objects.
10476 @var{name-regexp} is a regular expression matching the name of the printers
10479 @kindex disable pretty-printer
10480 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10481 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10482 A disabled pretty-printer is not forgotten, it may be enabled again later.
10484 @kindex enable pretty-printer
10485 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10486 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10491 Suppose we have three pretty-printers installed: one from library1.so
10492 named @code{foo} that prints objects of type @code{foo}, and
10493 another from library2.so named @code{bar} that prints two types of objects,
10494 @code{bar1} and @code{bar2}.
10497 (gdb) info pretty-printer
10504 (gdb) info pretty-printer library2
10509 (gdb) disable pretty-printer library1
10511 2 of 3 printers enabled
10512 (gdb) info pretty-printer
10519 (gdb) disable pretty-printer library2 bar:bar1
10521 1 of 3 printers enabled
10522 (gdb) info pretty-printer library2
10529 (gdb) disable pretty-printer library2 bar
10531 0 of 3 printers enabled
10532 (gdb) info pretty-printer library2
10541 Note that for @code{bar} the entire printer can be disabled,
10542 as can each individual subprinter.
10544 @node Value History
10545 @section Value History
10547 @cindex value history
10548 @cindex history of values printed by @value{GDBN}
10549 Values printed by the @code{print} command are saved in the @value{GDBN}
10550 @dfn{value history}. This allows you to refer to them in other expressions.
10551 Values are kept until the symbol table is re-read or discarded
10552 (for example with the @code{file} or @code{symbol-file} commands).
10553 When the symbol table changes, the value history is discarded,
10554 since the values may contain pointers back to the types defined in the
10559 @cindex history number
10560 The values printed are given @dfn{history numbers} by which you can
10561 refer to them. These are successive integers starting with one.
10562 @code{print} shows you the history number assigned to a value by
10563 printing @samp{$@var{num} = } before the value; here @var{num} is the
10566 To refer to any previous value, use @samp{$} followed by the value's
10567 history number. The way @code{print} labels its output is designed to
10568 remind you of this. Just @code{$} refers to the most recent value in
10569 the history, and @code{$$} refers to the value before that.
10570 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10571 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10572 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10574 For example, suppose you have just printed a pointer to a structure and
10575 want to see the contents of the structure. It suffices to type
10581 If you have a chain of structures where the component @code{next} points
10582 to the next one, you can print the contents of the next one with this:
10589 You can print successive links in the chain by repeating this
10590 command---which you can do by just typing @key{RET}.
10592 Note that the history records values, not expressions. If the value of
10593 @code{x} is 4 and you type these commands:
10601 then the value recorded in the value history by the @code{print} command
10602 remains 4 even though the value of @code{x} has changed.
10605 @kindex show values
10607 Print the last ten values in the value history, with their item numbers.
10608 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10609 values} does not change the history.
10611 @item show values @var{n}
10612 Print ten history values centered on history item number @var{n}.
10614 @item show values +
10615 Print ten history values just after the values last printed. If no more
10616 values are available, @code{show values +} produces no display.
10619 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10620 same effect as @samp{show values +}.
10622 @node Convenience Vars
10623 @section Convenience Variables
10625 @cindex convenience variables
10626 @cindex user-defined variables
10627 @value{GDBN} provides @dfn{convenience variables} that you can use within
10628 @value{GDBN} to hold on to a value and refer to it later. These variables
10629 exist entirely within @value{GDBN}; they are not part of your program, and
10630 setting a convenience variable has no direct effect on further execution
10631 of your program. That is why you can use them freely.
10633 Convenience variables are prefixed with @samp{$}. Any name preceded by
10634 @samp{$} can be used for a convenience variable, unless it is one of
10635 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10636 (Value history references, in contrast, are @emph{numbers} preceded
10637 by @samp{$}. @xref{Value History, ,Value History}.)
10639 You can save a value in a convenience variable with an assignment
10640 expression, just as you would set a variable in your program.
10644 set $foo = *object_ptr
10648 would save in @code{$foo} the value contained in the object pointed to by
10651 Using a convenience variable for the first time creates it, but its
10652 value is @code{void} until you assign a new value. You can alter the
10653 value with another assignment at any time.
10655 Convenience variables have no fixed types. You can assign a convenience
10656 variable any type of value, including structures and arrays, even if
10657 that variable already has a value of a different type. The convenience
10658 variable, when used as an expression, has the type of its current value.
10661 @kindex show convenience
10662 @cindex show all user variables and functions
10663 @item show convenience
10664 Print a list of convenience variables used so far, and their values,
10665 as well as a list of the convenience functions.
10666 Abbreviated @code{show conv}.
10668 @kindex init-if-undefined
10669 @cindex convenience variables, initializing
10670 @item init-if-undefined $@var{variable} = @var{expression}
10671 Set a convenience variable if it has not already been set. This is useful
10672 for user-defined commands that keep some state. It is similar, in concept,
10673 to using local static variables with initializers in C (except that
10674 convenience variables are global). It can also be used to allow users to
10675 override default values used in a command script.
10677 If the variable is already defined then the expression is not evaluated so
10678 any side-effects do not occur.
10681 One of the ways to use a convenience variable is as a counter to be
10682 incremented or a pointer to be advanced. For example, to print
10683 a field from successive elements of an array of structures:
10687 print bar[$i++]->contents
10691 Repeat that command by typing @key{RET}.
10693 Some convenience variables are created automatically by @value{GDBN} and given
10694 values likely to be useful.
10697 @vindex $_@r{, convenience variable}
10699 The variable @code{$_} is automatically set by the @code{x} command to
10700 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10701 commands which provide a default address for @code{x} to examine also
10702 set @code{$_} to that address; these commands include @code{info line}
10703 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10704 except when set by the @code{x} command, in which case it is a pointer
10705 to the type of @code{$__}.
10707 @vindex $__@r{, convenience variable}
10709 The variable @code{$__} is automatically set by the @code{x} command
10710 to the value found in the last address examined. Its type is chosen
10711 to match the format in which the data was printed.
10714 @vindex $_exitcode@r{, convenience variable}
10715 When the program being debugged terminates normally, @value{GDBN}
10716 automatically sets this variable to the exit code of the program, and
10717 resets @code{$_exitsignal} to @code{void}.
10720 @vindex $_exitsignal@r{, convenience variable}
10721 When the program being debugged dies due to an uncaught signal,
10722 @value{GDBN} automatically sets this variable to that signal's number,
10723 and resets @code{$_exitcode} to @code{void}.
10725 To distinguish between whether the program being debugged has exited
10726 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10727 @code{$_exitsignal} is not @code{void}), the convenience function
10728 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10729 Functions}). For example, considering the following source code:
10732 #include <signal.h>
10735 main (int argc, char *argv[])
10742 A valid way of telling whether the program being debugged has exited
10743 or signalled would be:
10746 (@value{GDBP}) define has_exited_or_signalled
10747 Type commands for definition of ``has_exited_or_signalled''.
10748 End with a line saying just ``end''.
10749 >if $_isvoid ($_exitsignal)
10750 >echo The program has exited\n
10752 >echo The program has signalled\n
10758 Program terminated with signal SIGALRM, Alarm clock.
10759 The program no longer exists.
10760 (@value{GDBP}) has_exited_or_signalled
10761 The program has signalled
10764 As can be seen, @value{GDBN} correctly informs that the program being
10765 debugged has signalled, since it calls @code{raise} and raises a
10766 @code{SIGALRM} signal. If the program being debugged had not called
10767 @code{raise}, then @value{GDBN} would report a normal exit:
10770 (@value{GDBP}) has_exited_or_signalled
10771 The program has exited
10775 The variable @code{$_exception} is set to the exception object being
10776 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10779 @itemx $_probe_arg0@dots{}$_probe_arg11
10780 Arguments to a static probe. @xref{Static Probe Points}.
10783 @vindex $_sdata@r{, inspect, convenience variable}
10784 The variable @code{$_sdata} contains extra collected static tracepoint
10785 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10786 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10787 if extra static tracepoint data has not been collected.
10790 @vindex $_siginfo@r{, convenience variable}
10791 The variable @code{$_siginfo} contains extra signal information
10792 (@pxref{extra signal information}). Note that @code{$_siginfo}
10793 could be empty, if the application has not yet received any signals.
10794 For example, it will be empty before you execute the @code{run} command.
10797 @vindex $_tlb@r{, convenience variable}
10798 The variable @code{$_tlb} is automatically set when debugging
10799 applications running on MS-Windows in native mode or connected to
10800 gdbserver that supports the @code{qGetTIBAddr} request.
10801 @xref{General Query Packets}.
10802 This variable contains the address of the thread information block.
10805 The number of the current inferior. @xref{Inferiors and
10806 Programs, ,Debugging Multiple Inferiors and Programs}.
10809 The thread number of the current thread. @xref{thread numbers}.
10812 The global number of the current thread. @xref{global thread numbers}.
10816 @node Convenience Funs
10817 @section Convenience Functions
10819 @cindex convenience functions
10820 @value{GDBN} also supplies some @dfn{convenience functions}. These
10821 have a syntax similar to convenience variables. A convenience
10822 function can be used in an expression just like an ordinary function;
10823 however, a convenience function is implemented internally to
10826 These functions do not require @value{GDBN} to be configured with
10827 @code{Python} support, which means that they are always available.
10831 @item $_isvoid (@var{expr})
10832 @findex $_isvoid@r{, convenience function}
10833 Return one if the expression @var{expr} is @code{void}. Otherwise it
10836 A @code{void} expression is an expression where the type of the result
10837 is @code{void}. For example, you can examine a convenience variable
10838 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10842 (@value{GDBP}) print $_exitcode
10844 (@value{GDBP}) print $_isvoid ($_exitcode)
10847 Starting program: ./a.out
10848 [Inferior 1 (process 29572) exited normally]
10849 (@value{GDBP}) print $_exitcode
10851 (@value{GDBP}) print $_isvoid ($_exitcode)
10855 In the example above, we used @code{$_isvoid} to check whether
10856 @code{$_exitcode} is @code{void} before and after the execution of the
10857 program being debugged. Before the execution there is no exit code to
10858 be examined, therefore @code{$_exitcode} is @code{void}. After the
10859 execution the program being debugged returned zero, therefore
10860 @code{$_exitcode} is zero, which means that it is not @code{void}
10863 The @code{void} expression can also be a call of a function from the
10864 program being debugged. For example, given the following function:
10873 The result of calling it inside @value{GDBN} is @code{void}:
10876 (@value{GDBP}) print foo ()
10878 (@value{GDBP}) print $_isvoid (foo ())
10880 (@value{GDBP}) set $v = foo ()
10881 (@value{GDBP}) print $v
10883 (@value{GDBP}) print $_isvoid ($v)
10889 These functions require @value{GDBN} to be configured with
10890 @code{Python} support.
10894 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10895 @findex $_memeq@r{, convenience function}
10896 Returns one if the @var{length} bytes at the addresses given by
10897 @var{buf1} and @var{buf2} are equal.
10898 Otherwise it returns zero.
10900 @item $_regex(@var{str}, @var{regex})
10901 @findex $_regex@r{, convenience function}
10902 Returns one if the string @var{str} matches the regular expression
10903 @var{regex}. Otherwise it returns zero.
10904 The syntax of the regular expression is that specified by @code{Python}'s
10905 regular expression support.
10907 @item $_streq(@var{str1}, @var{str2})
10908 @findex $_streq@r{, convenience function}
10909 Returns one if the strings @var{str1} and @var{str2} are equal.
10910 Otherwise it returns zero.
10912 @item $_strlen(@var{str})
10913 @findex $_strlen@r{, convenience function}
10914 Returns the length of string @var{str}.
10916 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10917 @findex $_caller_is@r{, convenience function}
10918 Returns one if the calling function's name is equal to @var{name}.
10919 Otherwise it returns zero.
10921 If the optional argument @var{number_of_frames} is provided,
10922 it is the number of frames up in the stack to look.
10930 at testsuite/gdb.python/py-caller-is.c:21
10931 #1 0x00000000004005a0 in middle_func ()
10932 at testsuite/gdb.python/py-caller-is.c:27
10933 #2 0x00000000004005ab in top_func ()
10934 at testsuite/gdb.python/py-caller-is.c:33
10935 #3 0x00000000004005b6 in main ()
10936 at testsuite/gdb.python/py-caller-is.c:39
10937 (gdb) print $_caller_is ("middle_func")
10939 (gdb) print $_caller_is ("top_func", 2)
10943 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10944 @findex $_caller_matches@r{, convenience function}
10945 Returns one if the calling function's name matches the regular expression
10946 @var{regexp}. Otherwise it returns zero.
10948 If the optional argument @var{number_of_frames} is provided,
10949 it is the number of frames up in the stack to look.
10952 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10953 @findex $_any_caller_is@r{, convenience function}
10954 Returns one if any calling function's name is equal to @var{name}.
10955 Otherwise it returns zero.
10957 If the optional argument @var{number_of_frames} is provided,
10958 it is the number of frames up in the stack to look.
10961 This function differs from @code{$_caller_is} in that this function
10962 checks all stack frames from the immediate caller to the frame specified
10963 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10964 frame specified by @var{number_of_frames}.
10966 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10967 @findex $_any_caller_matches@r{, convenience function}
10968 Returns one if any calling function's name matches the regular expression
10969 @var{regexp}. Otherwise it returns zero.
10971 If the optional argument @var{number_of_frames} is provided,
10972 it is the number of frames up in the stack to look.
10975 This function differs from @code{$_caller_matches} in that this function
10976 checks all stack frames from the immediate caller to the frame specified
10977 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10978 frame specified by @var{number_of_frames}.
10980 @item $_as_string(@var{value})
10981 @findex $_as_string@r{, convenience function}
10982 Return the string representation of @var{value}.
10984 This function is useful to obtain the textual label (enumerator) of an
10985 enumeration value. For example, assuming the variable @var{node} is of
10986 an enumerated type:
10989 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10990 Visiting node of type NODE_INTEGER
10995 @value{GDBN} provides the ability to list and get help on
10996 convenience functions.
10999 @item help function
11000 @kindex help function
11001 @cindex show all convenience functions
11002 Print a list of all convenience functions.
11009 You can refer to machine register contents, in expressions, as variables
11010 with names starting with @samp{$}. The names of registers are different
11011 for each machine; use @code{info registers} to see the names used on
11015 @kindex info registers
11016 @item info registers
11017 Print the names and values of all registers except floating-point
11018 and vector registers (in the selected stack frame).
11020 @kindex info all-registers
11021 @cindex floating point registers
11022 @item info all-registers
11023 Print the names and values of all registers, including floating-point
11024 and vector registers (in the selected stack frame).
11026 @item info registers @var{regname} @dots{}
11027 Print the @dfn{relativized} value of each specified register @var{regname}.
11028 As discussed in detail below, register values are normally relative to
11029 the selected stack frame. The @var{regname} may be any register name valid on
11030 the machine you are using, with or without the initial @samp{$}.
11033 @anchor{standard registers}
11034 @cindex stack pointer register
11035 @cindex program counter register
11036 @cindex process status register
11037 @cindex frame pointer register
11038 @cindex standard registers
11039 @value{GDBN} has four ``standard'' register names that are available (in
11040 expressions) on most machines---whenever they do not conflict with an
11041 architecture's canonical mnemonics for registers. The register names
11042 @code{$pc} and @code{$sp} are used for the program counter register and
11043 the stack pointer. @code{$fp} is used for a register that contains a
11044 pointer to the current stack frame, and @code{$ps} is used for a
11045 register that contains the processor status. For example,
11046 you could print the program counter in hex with
11053 or print the instruction to be executed next with
11060 or add four to the stack pointer@footnote{This is a way of removing
11061 one word from the stack, on machines where stacks grow downward in
11062 memory (most machines, nowadays). This assumes that the innermost
11063 stack frame is selected; setting @code{$sp} is not allowed when other
11064 stack frames are selected. To pop entire frames off the stack,
11065 regardless of machine architecture, use @code{return};
11066 see @ref{Returning, ,Returning from a Function}.} with
11072 Whenever possible, these four standard register names are available on
11073 your machine even though the machine has different canonical mnemonics,
11074 so long as there is no conflict. The @code{info registers} command
11075 shows the canonical names. For example, on the SPARC, @code{info
11076 registers} displays the processor status register as @code{$psr} but you
11077 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11078 is an alias for the @sc{eflags} register.
11080 @value{GDBN} always considers the contents of an ordinary register as an
11081 integer when the register is examined in this way. Some machines have
11082 special registers which can hold nothing but floating point; these
11083 registers are considered to have floating point values. There is no way
11084 to refer to the contents of an ordinary register as floating point value
11085 (although you can @emph{print} it as a floating point value with
11086 @samp{print/f $@var{regname}}).
11088 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11089 means that the data format in which the register contents are saved by
11090 the operating system is not the same one that your program normally
11091 sees. For example, the registers of the 68881 floating point
11092 coprocessor are always saved in ``extended'' (raw) format, but all C
11093 programs expect to work with ``double'' (virtual) format. In such
11094 cases, @value{GDBN} normally works with the virtual format only (the format
11095 that makes sense for your program), but the @code{info registers} command
11096 prints the data in both formats.
11098 @cindex SSE registers (x86)
11099 @cindex MMX registers (x86)
11100 Some machines have special registers whose contents can be interpreted
11101 in several different ways. For example, modern x86-based machines
11102 have SSE and MMX registers that can hold several values packed
11103 together in several different formats. @value{GDBN} refers to such
11104 registers in @code{struct} notation:
11107 (@value{GDBP}) print $xmm1
11109 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11110 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11111 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11112 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11113 v4_int32 = @{0, 20657912, 11, 13@},
11114 v2_int64 = @{88725056443645952, 55834574859@},
11115 uint128 = 0x0000000d0000000b013b36f800000000
11120 To set values of such registers, you need to tell @value{GDBN} which
11121 view of the register you wish to change, as if you were assigning
11122 value to a @code{struct} member:
11125 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11128 Normally, register values are relative to the selected stack frame
11129 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11130 value that the register would contain if all stack frames farther in
11131 were exited and their saved registers restored. In order to see the
11132 true contents of hardware registers, you must select the innermost
11133 frame (with @samp{frame 0}).
11135 @cindex caller-saved registers
11136 @cindex call-clobbered registers
11137 @cindex volatile registers
11138 @cindex <not saved> values
11139 Usually ABIs reserve some registers as not needed to be saved by the
11140 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11141 registers). It may therefore not be possible for @value{GDBN} to know
11142 the value a register had before the call (in other words, in the outer
11143 frame), if the register value has since been changed by the callee.
11144 @value{GDBN} tries to deduce where the inner frame saved
11145 (``callee-saved'') registers, from the debug info, unwind info, or the
11146 machine code generated by your compiler. If some register is not
11147 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11148 its own knowledge of the ABI, or because the debug/unwind info
11149 explicitly says the register's value is undefined), @value{GDBN}
11150 displays @w{@samp{<not saved>}} as the register's value. With targets
11151 that @value{GDBN} has no knowledge of the register saving convention,
11152 if a register was not saved by the callee, then its value and location
11153 in the outer frame are assumed to be the same of the inner frame.
11154 This is usually harmless, because if the register is call-clobbered,
11155 the caller either does not care what is in the register after the
11156 call, or has code to restore the value that it does care about. Note,
11157 however, that if you change such a register in the outer frame, you
11158 may also be affecting the inner frame. Also, the more ``outer'' the
11159 frame is you're looking at, the more likely a call-clobbered
11160 register's value is to be wrong, in the sense that it doesn't actually
11161 represent the value the register had just before the call.
11163 @node Floating Point Hardware
11164 @section Floating Point Hardware
11165 @cindex floating point
11167 Depending on the configuration, @value{GDBN} may be able to give
11168 you more information about the status of the floating point hardware.
11173 Display hardware-dependent information about the floating
11174 point unit. The exact contents and layout vary depending on the
11175 floating point chip. Currently, @samp{info float} is supported on
11176 the ARM and x86 machines.
11180 @section Vector Unit
11181 @cindex vector unit
11183 Depending on the configuration, @value{GDBN} may be able to give you
11184 more information about the status of the vector unit.
11187 @kindex info vector
11189 Display information about the vector unit. The exact contents and
11190 layout vary depending on the hardware.
11193 @node OS Information
11194 @section Operating System Auxiliary Information
11195 @cindex OS information
11197 @value{GDBN} provides interfaces to useful OS facilities that can help
11198 you debug your program.
11200 @cindex auxiliary vector
11201 @cindex vector, auxiliary
11202 Some operating systems supply an @dfn{auxiliary vector} to programs at
11203 startup. This is akin to the arguments and environment that you
11204 specify for a program, but contains a system-dependent variety of
11205 binary values that tell system libraries important details about the
11206 hardware, operating system, and process. Each value's purpose is
11207 identified by an integer tag; the meanings are well-known but system-specific.
11208 Depending on the configuration and operating system facilities,
11209 @value{GDBN} may be able to show you this information. For remote
11210 targets, this functionality may further depend on the remote stub's
11211 support of the @samp{qXfer:auxv:read} packet, see
11212 @ref{qXfer auxiliary vector read}.
11217 Display the auxiliary vector of the inferior, which can be either a
11218 live process or a core dump file. @value{GDBN} prints each tag value
11219 numerically, and also shows names and text descriptions for recognized
11220 tags. Some values in the vector are numbers, some bit masks, and some
11221 pointers to strings or other data. @value{GDBN} displays each value in the
11222 most appropriate form for a recognized tag, and in hexadecimal for
11223 an unrecognized tag.
11226 On some targets, @value{GDBN} can access operating system-specific
11227 information and show it to you. The types of information available
11228 will differ depending on the type of operating system running on the
11229 target. The mechanism used to fetch the data is described in
11230 @ref{Operating System Information}. For remote targets, this
11231 functionality depends on the remote stub's support of the
11232 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11236 @item info os @var{infotype}
11238 Display OS information of the requested type.
11240 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11242 @anchor{linux info os infotypes}
11244 @kindex info os cpus
11246 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11247 the available fields from /proc/cpuinfo. For each supported architecture
11248 different fields are available. Two common entries are processor which gives
11249 CPU number and bogomips; a system constant that is calculated during
11250 kernel initialization.
11252 @kindex info os files
11254 Display the list of open file descriptors on the target. For each
11255 file descriptor, @value{GDBN} prints the identifier of the process
11256 owning the descriptor, the command of the owning process, the value
11257 of the descriptor, and the target of the descriptor.
11259 @kindex info os modules
11261 Display the list of all loaded kernel modules on the target. For each
11262 module, @value{GDBN} prints the module name, the size of the module in
11263 bytes, the number of times the module is used, the dependencies of the
11264 module, the status of the module, and the address of the loaded module
11267 @kindex info os msg
11269 Display the list of all System V message queues on the target. For each
11270 message queue, @value{GDBN} prints the message queue key, the message
11271 queue identifier, the access permissions, the current number of bytes
11272 on the queue, the current number of messages on the queue, the processes
11273 that last sent and received a message on the queue, the user and group
11274 of the owner and creator of the message queue, the times at which a
11275 message was last sent and received on the queue, and the time at which
11276 the message queue was last changed.
11278 @kindex info os processes
11280 Display the list of processes on the target. For each process,
11281 @value{GDBN} prints the process identifier, the name of the user, the
11282 command corresponding to the process, and the list of processor cores
11283 that the process is currently running on. (To understand what these
11284 properties mean, for this and the following info types, please consult
11285 the general @sc{gnu}/Linux documentation.)
11287 @kindex info os procgroups
11289 Display the list of process groups on the target. For each process,
11290 @value{GDBN} prints the identifier of the process group that it belongs
11291 to, the command corresponding to the process group leader, the process
11292 identifier, and the command line of the process. The list is sorted
11293 first by the process group identifier, then by the process identifier,
11294 so that processes belonging to the same process group are grouped together
11295 and the process group leader is listed first.
11297 @kindex info os semaphores
11299 Display the list of all System V semaphore sets on the target. For each
11300 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11301 set identifier, the access permissions, the number of semaphores in the
11302 set, the user and group of the owner and creator of the semaphore set,
11303 and the times at which the semaphore set was operated upon and changed.
11305 @kindex info os shm
11307 Display the list of all System V shared-memory regions on the target.
11308 For each shared-memory region, @value{GDBN} prints the region key,
11309 the shared-memory identifier, the access permissions, the size of the
11310 region, the process that created the region, the process that last
11311 attached to or detached from the region, the current number of live
11312 attaches to the region, and the times at which the region was last
11313 attached to, detach from, and changed.
11315 @kindex info os sockets
11317 Display the list of Internet-domain sockets on the target. For each
11318 socket, @value{GDBN} prints the address and port of the local and
11319 remote endpoints, the current state of the connection, the creator of
11320 the socket, the IP address family of the socket, and the type of the
11323 @kindex info os threads
11325 Display the list of threads running on the target. For each thread,
11326 @value{GDBN} prints the identifier of the process that the thread
11327 belongs to, the command of the process, the thread identifier, and the
11328 processor core that it is currently running on. The main thread of a
11329 process is not listed.
11333 If @var{infotype} is omitted, then list the possible values for
11334 @var{infotype} and the kind of OS information available for each
11335 @var{infotype}. If the target does not return a list of possible
11336 types, this command will report an error.
11339 @node Memory Region Attributes
11340 @section Memory Region Attributes
11341 @cindex memory region attributes
11343 @dfn{Memory region attributes} allow you to describe special handling
11344 required by regions of your target's memory. @value{GDBN} uses
11345 attributes to determine whether to allow certain types of memory
11346 accesses; whether to use specific width accesses; and whether to cache
11347 target memory. By default the description of memory regions is
11348 fetched from the target (if the current target supports this), but the
11349 user can override the fetched regions.
11351 Defined memory regions can be individually enabled and disabled. When a
11352 memory region is disabled, @value{GDBN} uses the default attributes when
11353 accessing memory in that region. Similarly, if no memory regions have
11354 been defined, @value{GDBN} uses the default attributes when accessing
11357 When a memory region is defined, it is given a number to identify it;
11358 to enable, disable, or remove a memory region, you specify that number.
11362 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11363 Define a memory region bounded by @var{lower} and @var{upper} with
11364 attributes @var{attributes}@dots{}, and add it to the list of regions
11365 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11366 case: it is treated as the target's maximum memory address.
11367 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11370 Discard any user changes to the memory regions and use target-supplied
11371 regions, if available, or no regions if the target does not support.
11374 @item delete mem @var{nums}@dots{}
11375 Remove memory regions @var{nums}@dots{} from the list of regions
11376 monitored by @value{GDBN}.
11378 @kindex disable mem
11379 @item disable mem @var{nums}@dots{}
11380 Disable monitoring of memory regions @var{nums}@dots{}.
11381 A disabled memory region is not forgotten.
11382 It may be enabled again later.
11385 @item enable mem @var{nums}@dots{}
11386 Enable monitoring of memory regions @var{nums}@dots{}.
11390 Print a table of all defined memory regions, with the following columns
11394 @item Memory Region Number
11395 @item Enabled or Disabled.
11396 Enabled memory regions are marked with @samp{y}.
11397 Disabled memory regions are marked with @samp{n}.
11400 The address defining the inclusive lower bound of the memory region.
11403 The address defining the exclusive upper bound of the memory region.
11406 The list of attributes set for this memory region.
11411 @subsection Attributes
11413 @subsubsection Memory Access Mode
11414 The access mode attributes set whether @value{GDBN} may make read or
11415 write accesses to a memory region.
11417 While these attributes prevent @value{GDBN} from performing invalid
11418 memory accesses, they do nothing to prevent the target system, I/O DMA,
11419 etc.@: from accessing memory.
11423 Memory is read only.
11425 Memory is write only.
11427 Memory is read/write. This is the default.
11430 @subsubsection Memory Access Size
11431 The access size attribute tells @value{GDBN} to use specific sized
11432 accesses in the memory region. Often memory mapped device registers
11433 require specific sized accesses. If no access size attribute is
11434 specified, @value{GDBN} may use accesses of any size.
11438 Use 8 bit memory accesses.
11440 Use 16 bit memory accesses.
11442 Use 32 bit memory accesses.
11444 Use 64 bit memory accesses.
11447 @c @subsubsection Hardware/Software Breakpoints
11448 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11449 @c will use hardware or software breakpoints for the internal breakpoints
11450 @c used by the step, next, finish, until, etc. commands.
11454 @c Always use hardware breakpoints
11455 @c @item swbreak (default)
11458 @subsubsection Data Cache
11459 The data cache attributes set whether @value{GDBN} will cache target
11460 memory. While this generally improves performance by reducing debug
11461 protocol overhead, it can lead to incorrect results because @value{GDBN}
11462 does not know about volatile variables or memory mapped device
11467 Enable @value{GDBN} to cache target memory.
11469 Disable @value{GDBN} from caching target memory. This is the default.
11472 @subsection Memory Access Checking
11473 @value{GDBN} can be instructed to refuse accesses to memory that is
11474 not explicitly described. This can be useful if accessing such
11475 regions has undesired effects for a specific target, or to provide
11476 better error checking. The following commands control this behaviour.
11479 @kindex set mem inaccessible-by-default
11480 @item set mem inaccessible-by-default [on|off]
11481 If @code{on} is specified, make @value{GDBN} treat memory not
11482 explicitly described by the memory ranges as non-existent and refuse accesses
11483 to such memory. The checks are only performed if there's at least one
11484 memory range defined. If @code{off} is specified, make @value{GDBN}
11485 treat the memory not explicitly described by the memory ranges as RAM.
11486 The default value is @code{on}.
11487 @kindex show mem inaccessible-by-default
11488 @item show mem inaccessible-by-default
11489 Show the current handling of accesses to unknown memory.
11493 @c @subsubsection Memory Write Verification
11494 @c The memory write verification attributes set whether @value{GDBN}
11495 @c will re-reads data after each write to verify the write was successful.
11499 @c @item noverify (default)
11502 @node Dump/Restore Files
11503 @section Copy Between Memory and a File
11504 @cindex dump/restore files
11505 @cindex append data to a file
11506 @cindex dump data to a file
11507 @cindex restore data from a file
11509 You can use the commands @code{dump}, @code{append}, and
11510 @code{restore} to copy data between target memory and a file. The
11511 @code{dump} and @code{append} commands write data to a file, and the
11512 @code{restore} command reads data from a file back into the inferior's
11513 memory. Files may be in binary, Motorola S-record, Intel hex,
11514 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11515 append to binary files, and cannot read from Verilog Hex files.
11520 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11521 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11522 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11523 or the value of @var{expr}, to @var{filename} in the given format.
11525 The @var{format} parameter may be any one of:
11532 Motorola S-record format.
11534 Tektronix Hex format.
11536 Verilog Hex format.
11539 @value{GDBN} uses the same definitions of these formats as the
11540 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11541 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11545 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11546 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11547 Append the contents of memory from @var{start_addr} to @var{end_addr},
11548 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11549 (@value{GDBN} can only append data to files in raw binary form.)
11552 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11553 Restore the contents of file @var{filename} into memory. The
11554 @code{restore} command can automatically recognize any known @sc{bfd}
11555 file format, except for raw binary. To restore a raw binary file you
11556 must specify the optional keyword @code{binary} after the filename.
11558 If @var{bias} is non-zero, its value will be added to the addresses
11559 contained in the file. Binary files always start at address zero, so
11560 they will be restored at address @var{bias}. Other bfd files have
11561 a built-in location; they will be restored at offset @var{bias}
11562 from that location.
11564 If @var{start} and/or @var{end} are non-zero, then only data between
11565 file offset @var{start} and file offset @var{end} will be restored.
11566 These offsets are relative to the addresses in the file, before
11567 the @var{bias} argument is applied.
11571 @node Core File Generation
11572 @section How to Produce a Core File from Your Program
11573 @cindex dump core from inferior
11575 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11576 image of a running process and its process status (register values
11577 etc.). Its primary use is post-mortem debugging of a program that
11578 crashed while it ran outside a debugger. A program that crashes
11579 automatically produces a core file, unless this feature is disabled by
11580 the user. @xref{Files}, for information on invoking @value{GDBN} in
11581 the post-mortem debugging mode.
11583 Occasionally, you may wish to produce a core file of the program you
11584 are debugging in order to preserve a snapshot of its state.
11585 @value{GDBN} has a special command for that.
11589 @kindex generate-core-file
11590 @item generate-core-file [@var{file}]
11591 @itemx gcore [@var{file}]
11592 Produce a core dump of the inferior process. The optional argument
11593 @var{file} specifies the file name where to put the core dump. If not
11594 specified, the file name defaults to @file{core.@var{pid}}, where
11595 @var{pid} is the inferior process ID.
11597 Note that this command is implemented only for some systems (as of
11598 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11600 On @sc{gnu}/Linux, this command can take into account the value of the
11601 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11602 dump (@pxref{set use-coredump-filter}), and by default honors the
11603 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11604 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11606 @kindex set use-coredump-filter
11607 @anchor{set use-coredump-filter}
11608 @item set use-coredump-filter on
11609 @itemx set use-coredump-filter off
11610 Enable or disable the use of the file
11611 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11612 files. This file is used by the Linux kernel to decide what types of
11613 memory mappings will be dumped or ignored when generating a core dump
11614 file. @var{pid} is the process ID of a currently running process.
11616 To make use of this feature, you have to write in the
11617 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11618 which is a bit mask representing the memory mapping types. If a bit
11619 is set in the bit mask, then the memory mappings of the corresponding
11620 types will be dumped; otherwise, they will be ignored. This
11621 configuration is inherited by child processes. For more information
11622 about the bits that can be set in the
11623 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11624 manpage of @code{core(5)}.
11626 By default, this option is @code{on}. If this option is turned
11627 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11628 and instead uses the same default value as the Linux kernel in order
11629 to decide which pages will be dumped in the core dump file. This
11630 value is currently @code{0x33}, which means that bits @code{0}
11631 (anonymous private mappings), @code{1} (anonymous shared mappings),
11632 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11633 This will cause these memory mappings to be dumped automatically.
11635 @kindex set dump-excluded-mappings
11636 @anchor{set dump-excluded-mappings}
11637 @item set dump-excluded-mappings on
11638 @itemx set dump-excluded-mappings off
11639 If @code{on} is specified, @value{GDBN} will dump memory mappings
11640 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11641 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11643 The default value is @code{off}.
11646 @node Character Sets
11647 @section Character Sets
11648 @cindex character sets
11650 @cindex translating between character sets
11651 @cindex host character set
11652 @cindex target character set
11654 If the program you are debugging uses a different character set to
11655 represent characters and strings than the one @value{GDBN} uses itself,
11656 @value{GDBN} can automatically translate between the character sets for
11657 you. The character set @value{GDBN} uses we call the @dfn{host
11658 character set}; the one the inferior program uses we call the
11659 @dfn{target character set}.
11661 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11662 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11663 remote protocol (@pxref{Remote Debugging}) to debug a program
11664 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11665 then the host character set is Latin-1, and the target character set is
11666 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11667 target-charset EBCDIC-US}, then @value{GDBN} translates between
11668 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11669 character and string literals in expressions.
11671 @value{GDBN} has no way to automatically recognize which character set
11672 the inferior program uses; you must tell it, using the @code{set
11673 target-charset} command, described below.
11675 Here are the commands for controlling @value{GDBN}'s character set
11679 @item set target-charset @var{charset}
11680 @kindex set target-charset
11681 Set the current target character set to @var{charset}. To display the
11682 list of supported target character sets, type
11683 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11685 @item set host-charset @var{charset}
11686 @kindex set host-charset
11687 Set the current host character set to @var{charset}.
11689 By default, @value{GDBN} uses a host character set appropriate to the
11690 system it is running on; you can override that default using the
11691 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11692 automatically determine the appropriate host character set. In this
11693 case, @value{GDBN} uses @samp{UTF-8}.
11695 @value{GDBN} can only use certain character sets as its host character
11696 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11697 @value{GDBN} will list the host character sets it supports.
11699 @item set charset @var{charset}
11700 @kindex set charset
11701 Set the current host and target character sets to @var{charset}. As
11702 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11703 @value{GDBN} will list the names of the character sets that can be used
11704 for both host and target.
11707 @kindex show charset
11708 Show the names of the current host and target character sets.
11710 @item show host-charset
11711 @kindex show host-charset
11712 Show the name of the current host character set.
11714 @item show target-charset
11715 @kindex show target-charset
11716 Show the name of the current target character set.
11718 @item set target-wide-charset @var{charset}
11719 @kindex set target-wide-charset
11720 Set the current target's wide character set to @var{charset}. This is
11721 the character set used by the target's @code{wchar_t} type. To
11722 display the list of supported wide character sets, type
11723 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11725 @item show target-wide-charset
11726 @kindex show target-wide-charset
11727 Show the name of the current target's wide character set.
11730 Here is an example of @value{GDBN}'s character set support in action.
11731 Assume that the following source code has been placed in the file
11732 @file{charset-test.c}:
11738 = @{72, 101, 108, 108, 111, 44, 32, 119,
11739 111, 114, 108, 100, 33, 10, 0@};
11740 char ibm1047_hello[]
11741 = @{200, 133, 147, 147, 150, 107, 64, 166,
11742 150, 153, 147, 132, 90, 37, 0@};
11746 printf ("Hello, world!\n");
11750 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11751 containing the string @samp{Hello, world!} followed by a newline,
11752 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11754 We compile the program, and invoke the debugger on it:
11757 $ gcc -g charset-test.c -o charset-test
11758 $ gdb -nw charset-test
11759 GNU gdb 2001-12-19-cvs
11760 Copyright 2001 Free Software Foundation, Inc.
11765 We can use the @code{show charset} command to see what character sets
11766 @value{GDBN} is currently using to interpret and display characters and
11770 (@value{GDBP}) show charset
11771 The current host and target character set is `ISO-8859-1'.
11775 For the sake of printing this manual, let's use @sc{ascii} as our
11776 initial character set:
11778 (@value{GDBP}) set charset ASCII
11779 (@value{GDBP}) show charset
11780 The current host and target character set is `ASCII'.
11784 Let's assume that @sc{ascii} is indeed the correct character set for our
11785 host system --- in other words, let's assume that if @value{GDBN} prints
11786 characters using the @sc{ascii} character set, our terminal will display
11787 them properly. Since our current target character set is also
11788 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11791 (@value{GDBP}) print ascii_hello
11792 $1 = 0x401698 "Hello, world!\n"
11793 (@value{GDBP}) print ascii_hello[0]
11798 @value{GDBN} uses the target character set for character and string
11799 literals you use in expressions:
11802 (@value{GDBP}) print '+'
11807 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11810 @value{GDBN} relies on the user to tell it which character set the
11811 target program uses. If we print @code{ibm1047_hello} while our target
11812 character set is still @sc{ascii}, we get jibberish:
11815 (@value{GDBP}) print ibm1047_hello
11816 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11817 (@value{GDBP}) print ibm1047_hello[0]
11822 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11823 @value{GDBN} tells us the character sets it supports:
11826 (@value{GDBP}) set target-charset
11827 ASCII EBCDIC-US IBM1047 ISO-8859-1
11828 (@value{GDBP}) set target-charset
11831 We can select @sc{ibm1047} as our target character set, and examine the
11832 program's strings again. Now the @sc{ascii} string is wrong, but
11833 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11834 target character set, @sc{ibm1047}, to the host character set,
11835 @sc{ascii}, and they display correctly:
11838 (@value{GDBP}) set target-charset IBM1047
11839 (@value{GDBP}) show charset
11840 The current host character set is `ASCII'.
11841 The current target character set is `IBM1047'.
11842 (@value{GDBP}) print ascii_hello
11843 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11844 (@value{GDBP}) print ascii_hello[0]
11846 (@value{GDBP}) print ibm1047_hello
11847 $8 = 0x4016a8 "Hello, world!\n"
11848 (@value{GDBP}) print ibm1047_hello[0]
11853 As above, @value{GDBN} uses the target character set for character and
11854 string literals you use in expressions:
11857 (@value{GDBP}) print '+'
11862 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11865 @node Caching Target Data
11866 @section Caching Data of Targets
11867 @cindex caching data of targets
11869 @value{GDBN} caches data exchanged between the debugger and a target.
11870 Each cache is associated with the address space of the inferior.
11871 @xref{Inferiors and Programs}, about inferior and address space.
11872 Such caching generally improves performance in remote debugging
11873 (@pxref{Remote Debugging}), because it reduces the overhead of the
11874 remote protocol by bundling memory reads and writes into large chunks.
11875 Unfortunately, simply caching everything would lead to incorrect results,
11876 since @value{GDBN} does not necessarily know anything about volatile
11877 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11878 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11880 Therefore, by default, @value{GDBN} only caches data
11881 known to be on the stack@footnote{In non-stop mode, it is moderately
11882 rare for a running thread to modify the stack of a stopped thread
11883 in a way that would interfere with a backtrace, and caching of
11884 stack reads provides a significant speed up of remote backtraces.} or
11885 in the code segment.
11886 Other regions of memory can be explicitly marked as
11887 cacheable; @pxref{Memory Region Attributes}.
11890 @kindex set remotecache
11891 @item set remotecache on
11892 @itemx set remotecache off
11893 This option no longer does anything; it exists for compatibility
11896 @kindex show remotecache
11897 @item show remotecache
11898 Show the current state of the obsolete remotecache flag.
11900 @kindex set stack-cache
11901 @item set stack-cache on
11902 @itemx set stack-cache off
11903 Enable or disable caching of stack accesses. When @code{on}, use
11904 caching. By default, this option is @code{on}.
11906 @kindex show stack-cache
11907 @item show stack-cache
11908 Show the current state of data caching for memory accesses.
11910 @kindex set code-cache
11911 @item set code-cache on
11912 @itemx set code-cache off
11913 Enable or disable caching of code segment accesses. When @code{on},
11914 use caching. By default, this option is @code{on}. This improves
11915 performance of disassembly in remote debugging.
11917 @kindex show code-cache
11918 @item show code-cache
11919 Show the current state of target memory cache for code segment
11922 @kindex info dcache
11923 @item info dcache @r{[}line@r{]}
11924 Print the information about the performance of data cache of the
11925 current inferior's address space. The information displayed
11926 includes the dcache width and depth, and for each cache line, its
11927 number, address, and how many times it was referenced. This
11928 command is useful for debugging the data cache operation.
11930 If a line number is specified, the contents of that line will be
11933 @item set dcache size @var{size}
11934 @cindex dcache size
11935 @kindex set dcache size
11936 Set maximum number of entries in dcache (dcache depth above).
11938 @item set dcache line-size @var{line-size}
11939 @cindex dcache line-size
11940 @kindex set dcache line-size
11941 Set number of bytes each dcache entry caches (dcache width above).
11942 Must be a power of 2.
11944 @item show dcache size
11945 @kindex show dcache size
11946 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11948 @item show dcache line-size
11949 @kindex show dcache line-size
11950 Show default size of dcache lines.
11954 @node Searching Memory
11955 @section Search Memory
11956 @cindex searching memory
11958 Memory can be searched for a particular sequence of bytes with the
11959 @code{find} command.
11963 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11964 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11965 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11966 etc. The search begins at address @var{start_addr} and continues for either
11967 @var{len} bytes or through to @var{end_addr} inclusive.
11970 @var{s} and @var{n} are optional parameters.
11971 They may be specified in either order, apart or together.
11974 @item @var{s}, search query size
11975 The size of each search query value.
11981 halfwords (two bytes)
11985 giant words (eight bytes)
11988 All values are interpreted in the current language.
11989 This means, for example, that if the current source language is C/C@t{++}
11990 then searching for the string ``hello'' includes the trailing '\0'.
11991 The null terminator can be removed from searching by using casts,
11992 e.g.: @samp{@{char[5]@}"hello"}.
11994 If the value size is not specified, it is taken from the
11995 value's type in the current language.
11996 This is useful when one wants to specify the search
11997 pattern as a mixture of types.
11998 Note that this means, for example, that in the case of C-like languages
11999 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12000 which is typically four bytes.
12002 @item @var{n}, maximum number of finds
12003 The maximum number of matches to print. The default is to print all finds.
12006 You can use strings as search values. Quote them with double-quotes
12008 The string value is copied into the search pattern byte by byte,
12009 regardless of the endianness of the target and the size specification.
12011 The address of each match found is printed as well as a count of the
12012 number of matches found.
12014 The address of the last value found is stored in convenience variable
12016 A count of the number of matches is stored in @samp{$numfound}.
12018 For example, if stopped at the @code{printf} in this function:
12024 static char hello[] = "hello-hello";
12025 static struct @{ char c; short s; int i; @}
12026 __attribute__ ((packed)) mixed
12027 = @{ 'c', 0x1234, 0x87654321 @};
12028 printf ("%s\n", hello);
12033 you get during debugging:
12036 (gdb) find &hello[0], +sizeof(hello), "hello"
12037 0x804956d <hello.1620+6>
12039 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12040 0x8049567 <hello.1620>
12041 0x804956d <hello.1620+6>
12043 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12044 0x8049567 <hello.1620>
12045 0x804956d <hello.1620+6>
12047 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12048 0x8049567 <hello.1620>
12050 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12051 0x8049560 <mixed.1625>
12053 (gdb) print $numfound
12056 $2 = (void *) 0x8049560
12060 @section Value Sizes
12062 Whenever @value{GDBN} prints a value memory will be allocated within
12063 @value{GDBN} to hold the contents of the value. It is possible in
12064 some languages with dynamic typing systems, that an invalid program
12065 may indicate a value that is incorrectly large, this in turn may cause
12066 @value{GDBN} to try and allocate an overly large ammount of memory.
12069 @kindex set max-value-size
12070 @item set max-value-size @var{bytes}
12071 @itemx set max-value-size unlimited
12072 Set the maximum size of memory that @value{GDBN} will allocate for the
12073 contents of a value to @var{bytes}, trying to display a value that
12074 requires more memory than that will result in an error.
12076 Setting this variable does not effect values that have already been
12077 allocated within @value{GDBN}, only future allocations.
12079 There's a minimum size that @code{max-value-size} can be set to in
12080 order that @value{GDBN} can still operate correctly, this minimum is
12081 currently 16 bytes.
12083 The limit applies to the results of some subexpressions as well as to
12084 complete expressions. For example, an expression denoting a simple
12085 integer component, such as @code{x.y.z}, may fail if the size of
12086 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12087 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12088 @var{A} is an array variable with non-constant size, will generally
12089 succeed regardless of the bounds on @var{A}, as long as the component
12090 size is less than @var{bytes}.
12092 The default value of @code{max-value-size} is currently 64k.
12094 @kindex show max-value-size
12095 @item show max-value-size
12096 Show the maximum size of memory, in bytes, that @value{GDBN} will
12097 allocate for the contents of a value.
12100 @node Optimized Code
12101 @chapter Debugging Optimized Code
12102 @cindex optimized code, debugging
12103 @cindex debugging optimized code
12105 Almost all compilers support optimization. With optimization
12106 disabled, the compiler generates assembly code that corresponds
12107 directly to your source code, in a simplistic way. As the compiler
12108 applies more powerful optimizations, the generated assembly code
12109 diverges from your original source code. With help from debugging
12110 information generated by the compiler, @value{GDBN} can map from
12111 the running program back to constructs from your original source.
12113 @value{GDBN} is more accurate with optimization disabled. If you
12114 can recompile without optimization, it is easier to follow the
12115 progress of your program during debugging. But, there are many cases
12116 where you may need to debug an optimized version.
12118 When you debug a program compiled with @samp{-g -O}, remember that the
12119 optimizer has rearranged your code; the debugger shows you what is
12120 really there. Do not be too surprised when the execution path does not
12121 exactly match your source file! An extreme example: if you define a
12122 variable, but never use it, @value{GDBN} never sees that
12123 variable---because the compiler optimizes it out of existence.
12125 Some things do not work as well with @samp{-g -O} as with just
12126 @samp{-g}, particularly on machines with instruction scheduling. If in
12127 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12128 please report it to us as a bug (including a test case!).
12129 @xref{Variables}, for more information about debugging optimized code.
12132 * Inline Functions:: How @value{GDBN} presents inlining
12133 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12136 @node Inline Functions
12137 @section Inline Functions
12138 @cindex inline functions, debugging
12140 @dfn{Inlining} is an optimization that inserts a copy of the function
12141 body directly at each call site, instead of jumping to a shared
12142 routine. @value{GDBN} displays inlined functions just like
12143 non-inlined functions. They appear in backtraces. You can view their
12144 arguments and local variables, step into them with @code{step}, skip
12145 them with @code{next}, and escape from them with @code{finish}.
12146 You can check whether a function was inlined by using the
12147 @code{info frame} command.
12149 For @value{GDBN} to support inlined functions, the compiler must
12150 record information about inlining in the debug information ---
12151 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12152 other compilers do also. @value{GDBN} only supports inlined functions
12153 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12154 do not emit two required attributes (@samp{DW_AT_call_file} and
12155 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12156 function calls with earlier versions of @value{NGCC}. It instead
12157 displays the arguments and local variables of inlined functions as
12158 local variables in the caller.
12160 The body of an inlined function is directly included at its call site;
12161 unlike a non-inlined function, there are no instructions devoted to
12162 the call. @value{GDBN} still pretends that the call site and the
12163 start of the inlined function are different instructions. Stepping to
12164 the call site shows the call site, and then stepping again shows
12165 the first line of the inlined function, even though no additional
12166 instructions are executed.
12168 This makes source-level debugging much clearer; you can see both the
12169 context of the call and then the effect of the call. Only stepping by
12170 a single instruction using @code{stepi} or @code{nexti} does not do
12171 this; single instruction steps always show the inlined body.
12173 There are some ways that @value{GDBN} does not pretend that inlined
12174 function calls are the same as normal calls:
12178 Setting breakpoints at the call site of an inlined function may not
12179 work, because the call site does not contain any code. @value{GDBN}
12180 may incorrectly move the breakpoint to the next line of the enclosing
12181 function, after the call. This limitation will be removed in a future
12182 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12183 or inside the inlined function instead.
12186 @value{GDBN} cannot locate the return value of inlined calls after
12187 using the @code{finish} command. This is a limitation of compiler-generated
12188 debugging information; after @code{finish}, you can step to the next line
12189 and print a variable where your program stored the return value.
12193 @node Tail Call Frames
12194 @section Tail Call Frames
12195 @cindex tail call frames, debugging
12197 Function @code{B} can call function @code{C} in its very last statement. In
12198 unoptimized compilation the call of @code{C} is immediately followed by return
12199 instruction at the end of @code{B} code. Optimizing compiler may replace the
12200 call and return in function @code{B} into one jump to function @code{C}
12201 instead. Such use of a jump instruction is called @dfn{tail call}.
12203 During execution of function @code{C}, there will be no indication in the
12204 function call stack frames that it was tail-called from @code{B}. If function
12205 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12206 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12207 some cases @value{GDBN} can determine that @code{C} was tail-called from
12208 @code{B}, and it will then create fictitious call frame for that, with the
12209 return address set up as if @code{B} called @code{C} normally.
12211 This functionality is currently supported only by DWARF 2 debugging format and
12212 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12213 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12216 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12217 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12221 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12223 Stack level 1, frame at 0x7fffffffda30:
12224 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12225 tail call frame, caller of frame at 0x7fffffffda30
12226 source language c++.
12227 Arglist at unknown address.
12228 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12231 The detection of all the possible code path executions can find them ambiguous.
12232 There is no execution history stored (possible @ref{Reverse Execution} is never
12233 used for this purpose) and the last known caller could have reached the known
12234 callee by multiple different jump sequences. In such case @value{GDBN} still
12235 tries to show at least all the unambiguous top tail callers and all the
12236 unambiguous bottom tail calees, if any.
12239 @anchor{set debug entry-values}
12240 @item set debug entry-values
12241 @kindex set debug entry-values
12242 When set to on, enables printing of analysis messages for both frame argument
12243 values at function entry and tail calls. It will show all the possible valid
12244 tail calls code paths it has considered. It will also print the intersection
12245 of them with the final unambiguous (possibly partial or even empty) code path
12248 @item show debug entry-values
12249 @kindex show debug entry-values
12250 Show the current state of analysis messages printing for both frame argument
12251 values at function entry and tail calls.
12254 The analysis messages for tail calls can for example show why the virtual tail
12255 call frame for function @code{c} has not been recognized (due to the indirect
12256 reference by variable @code{x}):
12259 static void __attribute__((noinline, noclone)) c (void);
12260 void (*x) (void) = c;
12261 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12262 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12263 int main (void) @{ x (); return 0; @}
12265 Breakpoint 1, DW_OP_entry_value resolving cannot find
12266 DW_TAG_call_site 0x40039a in main
12268 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12271 #1 0x000000000040039a in main () at t.c:5
12274 Another possibility is an ambiguous virtual tail call frames resolution:
12278 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12279 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12280 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12281 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12282 static void __attribute__((noinline, noclone)) b (void)
12283 @{ if (i) c (); else e (); @}
12284 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12285 int main (void) @{ a (); return 0; @}
12287 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12288 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12289 tailcall: reduced: 0x4004d2(a) |
12292 #1 0x00000000004004d2 in a () at t.c:8
12293 #2 0x0000000000400395 in main () at t.c:9
12296 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12297 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12299 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12300 @ifset HAVE_MAKEINFO_CLICK
12301 @set ARROW @click{}
12302 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12303 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12305 @ifclear HAVE_MAKEINFO_CLICK
12307 @set CALLSEQ1B @value{CALLSEQ1A}
12308 @set CALLSEQ2B @value{CALLSEQ2A}
12311 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12312 The code can have possible execution paths @value{CALLSEQ1B} or
12313 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12315 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12316 has found. It then finds another possible calling sequcen - that one is
12317 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12318 printed as the @code{reduced:} calling sequence. That one could have many
12319 futher @code{compare:} and @code{reduced:} statements as long as there remain
12320 any non-ambiguous sequence entries.
12322 For the frame of function @code{b} in both cases there are different possible
12323 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12324 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12325 therefore this one is displayed to the user while the ambiguous frames are
12328 There can be also reasons why printing of frame argument values at function
12333 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12334 static void __attribute__((noinline, noclone)) a (int i);
12335 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12336 static void __attribute__((noinline, noclone)) a (int i)
12337 @{ if (i) b (i - 1); else c (0); @}
12338 int main (void) @{ a (5); return 0; @}
12341 #0 c (i=i@@entry=0) at t.c:2
12342 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12343 function "a" at 0x400420 can call itself via tail calls
12344 i=<optimized out>) at t.c:6
12345 #2 0x000000000040036e in main () at t.c:7
12348 @value{GDBN} cannot find out from the inferior state if and how many times did
12349 function @code{a} call itself (via function @code{b}) as these calls would be
12350 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12351 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12352 prints @code{<optimized out>} instead.
12355 @chapter C Preprocessor Macros
12357 Some languages, such as C and C@t{++}, provide a way to define and invoke
12358 ``preprocessor macros'' which expand into strings of tokens.
12359 @value{GDBN} can evaluate expressions containing macro invocations, show
12360 the result of macro expansion, and show a macro's definition, including
12361 where it was defined.
12363 You may need to compile your program specially to provide @value{GDBN}
12364 with information about preprocessor macros. Most compilers do not
12365 include macros in their debugging information, even when you compile
12366 with the @option{-g} flag. @xref{Compilation}.
12368 A program may define a macro at one point, remove that definition later,
12369 and then provide a different definition after that. Thus, at different
12370 points in the program, a macro may have different definitions, or have
12371 no definition at all. If there is a current stack frame, @value{GDBN}
12372 uses the macros in scope at that frame's source code line. Otherwise,
12373 @value{GDBN} uses the macros in scope at the current listing location;
12376 Whenever @value{GDBN} evaluates an expression, it always expands any
12377 macro invocations present in the expression. @value{GDBN} also provides
12378 the following commands for working with macros explicitly.
12382 @kindex macro expand
12383 @cindex macro expansion, showing the results of preprocessor
12384 @cindex preprocessor macro expansion, showing the results of
12385 @cindex expanding preprocessor macros
12386 @item macro expand @var{expression}
12387 @itemx macro exp @var{expression}
12388 Show the results of expanding all preprocessor macro invocations in
12389 @var{expression}. Since @value{GDBN} simply expands macros, but does
12390 not parse the result, @var{expression} need not be a valid expression;
12391 it can be any string of tokens.
12394 @item macro expand-once @var{expression}
12395 @itemx macro exp1 @var{expression}
12396 @cindex expand macro once
12397 @i{(This command is not yet implemented.)} Show the results of
12398 expanding those preprocessor macro invocations that appear explicitly in
12399 @var{expression}. Macro invocations appearing in that expansion are
12400 left unchanged. This command allows you to see the effect of a
12401 particular macro more clearly, without being confused by further
12402 expansions. Since @value{GDBN} simply expands macros, but does not
12403 parse the result, @var{expression} need not be a valid expression; it
12404 can be any string of tokens.
12407 @cindex macro definition, showing
12408 @cindex definition of a macro, showing
12409 @cindex macros, from debug info
12410 @item info macro [-a|-all] [--] @var{macro}
12411 Show the current definition or all definitions of the named @var{macro},
12412 and describe the source location or compiler command-line where that
12413 definition was established. The optional double dash is to signify the end of
12414 argument processing and the beginning of @var{macro} for non C-like macros where
12415 the macro may begin with a hyphen.
12417 @kindex info macros
12418 @item info macros @var{location}
12419 Show all macro definitions that are in effect at the location specified
12420 by @var{location}, and describe the source location or compiler
12421 command-line where those definitions were established.
12423 @kindex macro define
12424 @cindex user-defined macros
12425 @cindex defining macros interactively
12426 @cindex macros, user-defined
12427 @item macro define @var{macro} @var{replacement-list}
12428 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12429 Introduce a definition for a preprocessor macro named @var{macro},
12430 invocations of which are replaced by the tokens given in
12431 @var{replacement-list}. The first form of this command defines an
12432 ``object-like'' macro, which takes no arguments; the second form
12433 defines a ``function-like'' macro, which takes the arguments given in
12436 A definition introduced by this command is in scope in every
12437 expression evaluated in @value{GDBN}, until it is removed with the
12438 @code{macro undef} command, described below. The definition overrides
12439 all definitions for @var{macro} present in the program being debugged,
12440 as well as any previous user-supplied definition.
12442 @kindex macro undef
12443 @item macro undef @var{macro}
12444 Remove any user-supplied definition for the macro named @var{macro}.
12445 This command only affects definitions provided with the @code{macro
12446 define} command, described above; it cannot remove definitions present
12447 in the program being debugged.
12451 List all the macros defined using the @code{macro define} command.
12454 @cindex macros, example of debugging with
12455 Here is a transcript showing the above commands in action. First, we
12456 show our source files:
12461 #include "sample.h"
12464 #define ADD(x) (M + x)
12469 printf ("Hello, world!\n");
12471 printf ("We're so creative.\n");
12473 printf ("Goodbye, world!\n");
12480 Now, we compile the program using the @sc{gnu} C compiler,
12481 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12482 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12483 and @option{-gdwarf-4}; we recommend always choosing the most recent
12484 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12485 includes information about preprocessor macros in the debugging
12489 $ gcc -gdwarf-2 -g3 sample.c -o sample
12493 Now, we start @value{GDBN} on our sample program:
12497 GNU gdb 2002-05-06-cvs
12498 Copyright 2002 Free Software Foundation, Inc.
12499 GDB is free software, @dots{}
12503 We can expand macros and examine their definitions, even when the
12504 program is not running. @value{GDBN} uses the current listing position
12505 to decide which macro definitions are in scope:
12508 (@value{GDBP}) list main
12511 5 #define ADD(x) (M + x)
12516 10 printf ("Hello, world!\n");
12518 12 printf ("We're so creative.\n");
12519 (@value{GDBP}) info macro ADD
12520 Defined at /home/jimb/gdb/macros/play/sample.c:5
12521 #define ADD(x) (M + x)
12522 (@value{GDBP}) info macro Q
12523 Defined at /home/jimb/gdb/macros/play/sample.h:1
12524 included at /home/jimb/gdb/macros/play/sample.c:2
12526 (@value{GDBP}) macro expand ADD(1)
12527 expands to: (42 + 1)
12528 (@value{GDBP}) macro expand-once ADD(1)
12529 expands to: once (M + 1)
12533 In the example above, note that @code{macro expand-once} expands only
12534 the macro invocation explicit in the original text --- the invocation of
12535 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12536 which was introduced by @code{ADD}.
12538 Once the program is running, @value{GDBN} uses the macro definitions in
12539 force at the source line of the current stack frame:
12542 (@value{GDBP}) break main
12543 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12545 Starting program: /home/jimb/gdb/macros/play/sample
12547 Breakpoint 1, main () at sample.c:10
12548 10 printf ("Hello, world!\n");
12552 At line 10, the definition of the macro @code{N} at line 9 is in force:
12555 (@value{GDBP}) info macro N
12556 Defined at /home/jimb/gdb/macros/play/sample.c:9
12558 (@value{GDBP}) macro expand N Q M
12559 expands to: 28 < 42
12560 (@value{GDBP}) print N Q M
12565 As we step over directives that remove @code{N}'s definition, and then
12566 give it a new definition, @value{GDBN} finds the definition (or lack
12567 thereof) in force at each point:
12570 (@value{GDBP}) next
12572 12 printf ("We're so creative.\n");
12573 (@value{GDBP}) info macro N
12574 The symbol `N' has no definition as a C/C++ preprocessor macro
12575 at /home/jimb/gdb/macros/play/sample.c:12
12576 (@value{GDBP}) next
12578 14 printf ("Goodbye, world!\n");
12579 (@value{GDBP}) info macro N
12580 Defined at /home/jimb/gdb/macros/play/sample.c:13
12582 (@value{GDBP}) macro expand N Q M
12583 expands to: 1729 < 42
12584 (@value{GDBP}) print N Q M
12589 In addition to source files, macros can be defined on the compilation command
12590 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12591 such a way, @value{GDBN} displays the location of their definition as line zero
12592 of the source file submitted to the compiler.
12595 (@value{GDBP}) info macro __STDC__
12596 Defined at /home/jimb/gdb/macros/play/sample.c:0
12603 @chapter Tracepoints
12604 @c This chapter is based on the documentation written by Michael
12605 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12607 @cindex tracepoints
12608 In some applications, it is not feasible for the debugger to interrupt
12609 the program's execution long enough for the developer to learn
12610 anything helpful about its behavior. If the program's correctness
12611 depends on its real-time behavior, delays introduced by a debugger
12612 might cause the program to change its behavior drastically, or perhaps
12613 fail, even when the code itself is correct. It is useful to be able
12614 to observe the program's behavior without interrupting it.
12616 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12617 specify locations in the program, called @dfn{tracepoints}, and
12618 arbitrary expressions to evaluate when those tracepoints are reached.
12619 Later, using the @code{tfind} command, you can examine the values
12620 those expressions had when the program hit the tracepoints. The
12621 expressions may also denote objects in memory---structures or arrays,
12622 for example---whose values @value{GDBN} should record; while visiting
12623 a particular tracepoint, you may inspect those objects as if they were
12624 in memory at that moment. However, because @value{GDBN} records these
12625 values without interacting with you, it can do so quickly and
12626 unobtrusively, hopefully not disturbing the program's behavior.
12628 The tracepoint facility is currently available only for remote
12629 targets. @xref{Targets}. In addition, your remote target must know
12630 how to collect trace data. This functionality is implemented in the
12631 remote stub; however, none of the stubs distributed with @value{GDBN}
12632 support tracepoints as of this writing. The format of the remote
12633 packets used to implement tracepoints are described in @ref{Tracepoint
12636 It is also possible to get trace data from a file, in a manner reminiscent
12637 of corefiles; you specify the filename, and use @code{tfind} to search
12638 through the file. @xref{Trace Files}, for more details.
12640 This chapter describes the tracepoint commands and features.
12643 * Set Tracepoints::
12644 * Analyze Collected Data::
12645 * Tracepoint Variables::
12649 @node Set Tracepoints
12650 @section Commands to Set Tracepoints
12652 Before running such a @dfn{trace experiment}, an arbitrary number of
12653 tracepoints can be set. A tracepoint is actually a special type of
12654 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12655 standard breakpoint commands. For instance, as with breakpoints,
12656 tracepoint numbers are successive integers starting from one, and many
12657 of the commands associated with tracepoints take the tracepoint number
12658 as their argument, to identify which tracepoint to work on.
12660 For each tracepoint, you can specify, in advance, some arbitrary set
12661 of data that you want the target to collect in the trace buffer when
12662 it hits that tracepoint. The collected data can include registers,
12663 local variables, or global data. Later, you can use @value{GDBN}
12664 commands to examine the values these data had at the time the
12665 tracepoint was hit.
12667 Tracepoints do not support every breakpoint feature. Ignore counts on
12668 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12669 commands when they are hit. Tracepoints may not be thread-specific
12672 @cindex fast tracepoints
12673 Some targets may support @dfn{fast tracepoints}, which are inserted in
12674 a different way (such as with a jump instead of a trap), that is
12675 faster but possibly restricted in where they may be installed.
12677 @cindex static tracepoints
12678 @cindex markers, static tracepoints
12679 @cindex probing markers, static tracepoints
12680 Regular and fast tracepoints are dynamic tracing facilities, meaning
12681 that they can be used to insert tracepoints at (almost) any location
12682 in the target. Some targets may also support controlling @dfn{static
12683 tracepoints} from @value{GDBN}. With static tracing, a set of
12684 instrumentation points, also known as @dfn{markers}, are embedded in
12685 the target program, and can be activated or deactivated by name or
12686 address. These are usually placed at locations which facilitate
12687 investigating what the target is actually doing. @value{GDBN}'s
12688 support for static tracing includes being able to list instrumentation
12689 points, and attach them with @value{GDBN} defined high level
12690 tracepoints that expose the whole range of convenience of
12691 @value{GDBN}'s tracepoints support. Namely, support for collecting
12692 registers values and values of global or local (to the instrumentation
12693 point) variables; tracepoint conditions and trace state variables.
12694 The act of installing a @value{GDBN} static tracepoint on an
12695 instrumentation point, or marker, is referred to as @dfn{probing} a
12696 static tracepoint marker.
12698 @code{gdbserver} supports tracepoints on some target systems.
12699 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12701 This section describes commands to set tracepoints and associated
12702 conditions and actions.
12705 * Create and Delete Tracepoints::
12706 * Enable and Disable Tracepoints::
12707 * Tracepoint Passcounts::
12708 * Tracepoint Conditions::
12709 * Trace State Variables::
12710 * Tracepoint Actions::
12711 * Listing Tracepoints::
12712 * Listing Static Tracepoint Markers::
12713 * Starting and Stopping Trace Experiments::
12714 * Tracepoint Restrictions::
12717 @node Create and Delete Tracepoints
12718 @subsection Create and Delete Tracepoints
12721 @cindex set tracepoint
12723 @item trace @var{location}
12724 The @code{trace} command is very similar to the @code{break} command.
12725 Its argument @var{location} can be any valid location.
12726 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12727 which is a point in the target program where the debugger will briefly stop,
12728 collect some data, and then allow the program to continue. Setting a tracepoint
12729 or changing its actions takes effect immediately if the remote stub
12730 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12732 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12733 these changes don't take effect until the next @code{tstart}
12734 command, and once a trace experiment is running, further changes will
12735 not have any effect until the next trace experiment starts. In addition,
12736 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12737 address is not yet resolved. (This is similar to pending breakpoints.)
12738 Pending tracepoints are not downloaded to the target and not installed
12739 until they are resolved. The resolution of pending tracepoints requires
12740 @value{GDBN} support---when debugging with the remote target, and
12741 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12742 tracing}), pending tracepoints can not be resolved (and downloaded to
12743 the remote stub) while @value{GDBN} is disconnected.
12745 Here are some examples of using the @code{trace} command:
12748 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12750 (@value{GDBP}) @b{trace +2} // 2 lines forward
12752 (@value{GDBP}) @b{trace my_function} // first source line of function
12754 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12756 (@value{GDBP}) @b{trace *0x2117c4} // an address
12760 You can abbreviate @code{trace} as @code{tr}.
12762 @item trace @var{location} if @var{cond}
12763 Set a tracepoint with condition @var{cond}; evaluate the expression
12764 @var{cond} each time the tracepoint is reached, and collect data only
12765 if the value is nonzero---that is, if @var{cond} evaluates as true.
12766 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12767 information on tracepoint conditions.
12769 @item ftrace @var{location} [ if @var{cond} ]
12770 @cindex set fast tracepoint
12771 @cindex fast tracepoints, setting
12773 The @code{ftrace} command sets a fast tracepoint. For targets that
12774 support them, fast tracepoints will use a more efficient but possibly
12775 less general technique to trigger data collection, such as a jump
12776 instruction instead of a trap, or some sort of hardware support. It
12777 may not be possible to create a fast tracepoint at the desired
12778 location, in which case the command will exit with an explanatory
12781 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12784 On 32-bit x86-architecture systems, fast tracepoints normally need to
12785 be placed at an instruction that is 5 bytes or longer, but can be
12786 placed at 4-byte instructions if the low 64K of memory of the target
12787 program is available to install trampolines. Some Unix-type systems,
12788 such as @sc{gnu}/Linux, exclude low addresses from the program's
12789 address space; but for instance with the Linux kernel it is possible
12790 to let @value{GDBN} use this area by doing a @command{sysctl} command
12791 to set the @code{mmap_min_addr} kernel parameter, as in
12794 sudo sysctl -w vm.mmap_min_addr=32768
12798 which sets the low address to 32K, which leaves plenty of room for
12799 trampolines. The minimum address should be set to a page boundary.
12801 @item strace @var{location} [ if @var{cond} ]
12802 @cindex set static tracepoint
12803 @cindex static tracepoints, setting
12804 @cindex probe static tracepoint marker
12806 The @code{strace} command sets a static tracepoint. For targets that
12807 support it, setting a static tracepoint probes a static
12808 instrumentation point, or marker, found at @var{location}. It may not
12809 be possible to set a static tracepoint at the desired location, in
12810 which case the command will exit with an explanatory message.
12812 @value{GDBN} handles arguments to @code{strace} exactly as for
12813 @code{trace}, with the addition that the user can also specify
12814 @code{-m @var{marker}} as @var{location}. This probes the marker
12815 identified by the @var{marker} string identifier. This identifier
12816 depends on the static tracepoint backend library your program is
12817 using. You can find all the marker identifiers in the @samp{ID} field
12818 of the @code{info static-tracepoint-markers} command output.
12819 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12820 Markers}. For example, in the following small program using the UST
12826 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12831 the marker id is composed of joining the first two arguments to the
12832 @code{trace_mark} call with a slash, which translates to:
12835 (@value{GDBP}) info static-tracepoint-markers
12836 Cnt Enb ID Address What
12837 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12843 so you may probe the marker above with:
12846 (@value{GDBP}) strace -m ust/bar33
12849 Static tracepoints accept an extra collect action --- @code{collect
12850 $_sdata}. This collects arbitrary user data passed in the probe point
12851 call to the tracing library. In the UST example above, you'll see
12852 that the third argument to @code{trace_mark} is a printf-like format
12853 string. The user data is then the result of running that formating
12854 string against the following arguments. Note that @code{info
12855 static-tracepoint-markers} command output lists that format string in
12856 the @samp{Data:} field.
12858 You can inspect this data when analyzing the trace buffer, by printing
12859 the $_sdata variable like any other variable available to
12860 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12863 @cindex last tracepoint number
12864 @cindex recent tracepoint number
12865 @cindex tracepoint number
12866 The convenience variable @code{$tpnum} records the tracepoint number
12867 of the most recently set tracepoint.
12869 @kindex delete tracepoint
12870 @cindex tracepoint deletion
12871 @item delete tracepoint @r{[}@var{num}@r{]}
12872 Permanently delete one or more tracepoints. With no argument, the
12873 default is to delete all tracepoints. Note that the regular
12874 @code{delete} command can remove tracepoints also.
12879 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12881 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12885 You can abbreviate this command as @code{del tr}.
12888 @node Enable and Disable Tracepoints
12889 @subsection Enable and Disable Tracepoints
12891 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12894 @kindex disable tracepoint
12895 @item disable tracepoint @r{[}@var{num}@r{]}
12896 Disable tracepoint @var{num}, or all tracepoints if no argument
12897 @var{num} is given. A disabled tracepoint will have no effect during
12898 a trace experiment, but it is not forgotten. You can re-enable
12899 a disabled tracepoint using the @code{enable tracepoint} command.
12900 If the command is issued during a trace experiment and the debug target
12901 has support for disabling tracepoints during a trace experiment, then the
12902 change will be effective immediately. Otherwise, it will be applied to the
12903 next trace experiment.
12905 @kindex enable tracepoint
12906 @item enable tracepoint @r{[}@var{num}@r{]}
12907 Enable tracepoint @var{num}, or all tracepoints. If this command is
12908 issued during a trace experiment and the debug target supports enabling
12909 tracepoints during a trace experiment, then the enabled tracepoints will
12910 become effective immediately. Otherwise, they will become effective the
12911 next time a trace experiment is run.
12914 @node Tracepoint Passcounts
12915 @subsection Tracepoint Passcounts
12919 @cindex tracepoint pass count
12920 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12921 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12922 automatically stop a trace experiment. If a tracepoint's passcount is
12923 @var{n}, then the trace experiment will be automatically stopped on
12924 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12925 @var{num} is not specified, the @code{passcount} command sets the
12926 passcount of the most recently defined tracepoint. If no passcount is
12927 given, the trace experiment will run until stopped explicitly by the
12933 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12934 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12936 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12937 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12938 (@value{GDBP}) @b{trace foo}
12939 (@value{GDBP}) @b{pass 3}
12940 (@value{GDBP}) @b{trace bar}
12941 (@value{GDBP}) @b{pass 2}
12942 (@value{GDBP}) @b{trace baz}
12943 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12944 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12945 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12946 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12950 @node Tracepoint Conditions
12951 @subsection Tracepoint Conditions
12952 @cindex conditional tracepoints
12953 @cindex tracepoint conditions
12955 The simplest sort of tracepoint collects data every time your program
12956 reaches a specified place. You can also specify a @dfn{condition} for
12957 a tracepoint. A condition is just a Boolean expression in your
12958 programming language (@pxref{Expressions, ,Expressions}). A
12959 tracepoint with a condition evaluates the expression each time your
12960 program reaches it, and data collection happens only if the condition
12963 Tracepoint conditions can be specified when a tracepoint is set, by
12964 using @samp{if} in the arguments to the @code{trace} command.
12965 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12966 also be set or changed at any time with the @code{condition} command,
12967 just as with breakpoints.
12969 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12970 the conditional expression itself. Instead, @value{GDBN} encodes the
12971 expression into an agent expression (@pxref{Agent Expressions})
12972 suitable for execution on the target, independently of @value{GDBN}.
12973 Global variables become raw memory locations, locals become stack
12974 accesses, and so forth.
12976 For instance, suppose you have a function that is usually called
12977 frequently, but should not be called after an error has occurred. You
12978 could use the following tracepoint command to collect data about calls
12979 of that function that happen while the error code is propagating
12980 through the program; an unconditional tracepoint could end up
12981 collecting thousands of useless trace frames that you would have to
12985 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12988 @node Trace State Variables
12989 @subsection Trace State Variables
12990 @cindex trace state variables
12992 A @dfn{trace state variable} is a special type of variable that is
12993 created and managed by target-side code. The syntax is the same as
12994 that for GDB's convenience variables (a string prefixed with ``$''),
12995 but they are stored on the target. They must be created explicitly,
12996 using a @code{tvariable} command. They are always 64-bit signed
12999 Trace state variables are remembered by @value{GDBN}, and downloaded
13000 to the target along with tracepoint information when the trace
13001 experiment starts. There are no intrinsic limits on the number of
13002 trace state variables, beyond memory limitations of the target.
13004 @cindex convenience variables, and trace state variables
13005 Although trace state variables are managed by the target, you can use
13006 them in print commands and expressions as if they were convenience
13007 variables; @value{GDBN} will get the current value from the target
13008 while the trace experiment is running. Trace state variables share
13009 the same namespace as other ``$'' variables, which means that you
13010 cannot have trace state variables with names like @code{$23} or
13011 @code{$pc}, nor can you have a trace state variable and a convenience
13012 variable with the same name.
13016 @item tvariable $@var{name} [ = @var{expression} ]
13018 The @code{tvariable} command creates a new trace state variable named
13019 @code{$@var{name}}, and optionally gives it an initial value of
13020 @var{expression}. The @var{expression} is evaluated when this command is
13021 entered; the result will be converted to an integer if possible,
13022 otherwise @value{GDBN} will report an error. A subsequent
13023 @code{tvariable} command specifying the same name does not create a
13024 variable, but instead assigns the supplied initial value to the
13025 existing variable of that name, overwriting any previous initial
13026 value. The default initial value is 0.
13028 @item info tvariables
13029 @kindex info tvariables
13030 List all the trace state variables along with their initial values.
13031 Their current values may also be displayed, if the trace experiment is
13034 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13035 @kindex delete tvariable
13036 Delete the given trace state variables, or all of them if no arguments
13041 @node Tracepoint Actions
13042 @subsection Tracepoint Action Lists
13046 @cindex tracepoint actions
13047 @item actions @r{[}@var{num}@r{]}
13048 This command will prompt for a list of actions to be taken when the
13049 tracepoint is hit. If the tracepoint number @var{num} is not
13050 specified, this command sets the actions for the one that was most
13051 recently defined (so that you can define a tracepoint and then say
13052 @code{actions} without bothering about its number). You specify the
13053 actions themselves on the following lines, one action at a time, and
13054 terminate the actions list with a line containing just @code{end}. So
13055 far, the only defined actions are @code{collect}, @code{teval}, and
13056 @code{while-stepping}.
13058 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13059 Commands, ,Breakpoint Command Lists}), except that only the defined
13060 actions are allowed; any other @value{GDBN} command is rejected.
13062 @cindex remove actions from a tracepoint
13063 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13064 and follow it immediately with @samp{end}.
13067 (@value{GDBP}) @b{collect @var{data}} // collect some data
13069 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13071 (@value{GDBP}) @b{end} // signals the end of actions.
13074 In the following example, the action list begins with @code{collect}
13075 commands indicating the things to be collected when the tracepoint is
13076 hit. Then, in order to single-step and collect additional data
13077 following the tracepoint, a @code{while-stepping} command is used,
13078 followed by the list of things to be collected after each step in a
13079 sequence of single steps. The @code{while-stepping} command is
13080 terminated by its own separate @code{end} command. Lastly, the action
13081 list is terminated by an @code{end} command.
13084 (@value{GDBP}) @b{trace foo}
13085 (@value{GDBP}) @b{actions}
13086 Enter actions for tracepoint 1, one per line:
13089 > while-stepping 12
13090 > collect $pc, arr[i]
13095 @kindex collect @r{(tracepoints)}
13096 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13097 Collect values of the given expressions when the tracepoint is hit.
13098 This command accepts a comma-separated list of any valid expressions.
13099 In addition to global, static, or local variables, the following
13100 special arguments are supported:
13104 Collect all registers.
13107 Collect all function arguments.
13110 Collect all local variables.
13113 Collect the return address. This is helpful if you want to see more
13116 @emph{Note:} The return address location can not always be reliably
13117 determined up front, and the wrong address / registers may end up
13118 collected instead. On some architectures the reliability is higher
13119 for tracepoints at function entry, while on others it's the opposite.
13120 When this happens, backtracing will stop because the return address is
13121 found unavailable (unless another collect rule happened to match it).
13124 Collects the number of arguments from the static probe at which the
13125 tracepoint is located.
13126 @xref{Static Probe Points}.
13128 @item $_probe_arg@var{n}
13129 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13130 from the static probe at which the tracepoint is located.
13131 @xref{Static Probe Points}.
13134 @vindex $_sdata@r{, collect}
13135 Collect static tracepoint marker specific data. Only available for
13136 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13137 Lists}. On the UST static tracepoints library backend, an
13138 instrumentation point resembles a @code{printf} function call. The
13139 tracing library is able to collect user specified data formatted to a
13140 character string using the format provided by the programmer that
13141 instrumented the program. Other backends have similar mechanisms.
13142 Here's an example of a UST marker call:
13145 const char master_name[] = "$your_name";
13146 trace_mark(channel1, marker1, "hello %s", master_name)
13149 In this case, collecting @code{$_sdata} collects the string
13150 @samp{hello $yourname}. When analyzing the trace buffer, you can
13151 inspect @samp{$_sdata} like any other variable available to
13155 You can give several consecutive @code{collect} commands, each one
13156 with a single argument, or one @code{collect} command with several
13157 arguments separated by commas; the effect is the same.
13159 The optional @var{mods} changes the usual handling of the arguments.
13160 @code{s} requests that pointers to chars be handled as strings, in
13161 particular collecting the contents of the memory being pointed at, up
13162 to the first zero. The upper bound is by default the value of the
13163 @code{print elements} variable; if @code{s} is followed by a decimal
13164 number, that is the upper bound instead. So for instance
13165 @samp{collect/s25 mystr} collects as many as 25 characters at
13168 The command @code{info scope} (@pxref{Symbols, info scope}) is
13169 particularly useful for figuring out what data to collect.
13171 @kindex teval @r{(tracepoints)}
13172 @item teval @var{expr1}, @var{expr2}, @dots{}
13173 Evaluate the given expressions when the tracepoint is hit. This
13174 command accepts a comma-separated list of expressions. The results
13175 are discarded, so this is mainly useful for assigning values to trace
13176 state variables (@pxref{Trace State Variables}) without adding those
13177 values to the trace buffer, as would be the case if the @code{collect}
13180 @kindex while-stepping @r{(tracepoints)}
13181 @item while-stepping @var{n}
13182 Perform @var{n} single-step instruction traces after the tracepoint,
13183 collecting new data after each step. The @code{while-stepping}
13184 command is followed by the list of what to collect while stepping
13185 (followed by its own @code{end} command):
13188 > while-stepping 12
13189 > collect $regs, myglobal
13195 Note that @code{$pc} is not automatically collected by
13196 @code{while-stepping}; you need to explicitly collect that register if
13197 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13200 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13201 @kindex set default-collect
13202 @cindex default collection action
13203 This variable is a list of expressions to collect at each tracepoint
13204 hit. It is effectively an additional @code{collect} action prepended
13205 to every tracepoint action list. The expressions are parsed
13206 individually for each tracepoint, so for instance a variable named
13207 @code{xyz} may be interpreted as a global for one tracepoint, and a
13208 local for another, as appropriate to the tracepoint's location.
13210 @item show default-collect
13211 @kindex show default-collect
13212 Show the list of expressions that are collected by default at each
13217 @node Listing Tracepoints
13218 @subsection Listing Tracepoints
13221 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13222 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13223 @cindex information about tracepoints
13224 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13225 Display information about the tracepoint @var{num}. If you don't
13226 specify a tracepoint number, displays information about all the
13227 tracepoints defined so far. The format is similar to that used for
13228 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13229 command, simply restricting itself to tracepoints.
13231 A tracepoint's listing may include additional information specific to
13236 its passcount as given by the @code{passcount @var{n}} command
13239 the state about installed on target of each location
13243 (@value{GDBP}) @b{info trace}
13244 Num Type Disp Enb Address What
13245 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13247 collect globfoo, $regs
13252 2 tracepoint keep y <MULTIPLE>
13254 2.1 y 0x0804859c in func4 at change-loc.h:35
13255 installed on target
13256 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13257 installed on target
13258 2.3 y <PENDING> set_tracepoint
13259 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13260 not installed on target
13265 This command can be abbreviated @code{info tp}.
13268 @node Listing Static Tracepoint Markers
13269 @subsection Listing Static Tracepoint Markers
13272 @kindex info static-tracepoint-markers
13273 @cindex information about static tracepoint markers
13274 @item info static-tracepoint-markers
13275 Display information about all static tracepoint markers defined in the
13278 For each marker, the following columns are printed:
13282 An incrementing counter, output to help readability. This is not a
13285 The marker ID, as reported by the target.
13286 @item Enabled or Disabled
13287 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13288 that are not enabled.
13290 Where the marker is in your program, as a memory address.
13292 Where the marker is in the source for your program, as a file and line
13293 number. If the debug information included in the program does not
13294 allow @value{GDBN} to locate the source of the marker, this column
13295 will be left blank.
13299 In addition, the following information may be printed for each marker:
13303 User data passed to the tracing library by the marker call. In the
13304 UST backend, this is the format string passed as argument to the
13306 @item Static tracepoints probing the marker
13307 The list of static tracepoints attached to the marker.
13311 (@value{GDBP}) info static-tracepoint-markers
13312 Cnt ID Enb Address What
13313 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13314 Data: number1 %d number2 %d
13315 Probed by static tracepoints: #2
13316 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13322 @node Starting and Stopping Trace Experiments
13323 @subsection Starting and Stopping Trace Experiments
13326 @kindex tstart [ @var{notes} ]
13327 @cindex start a new trace experiment
13328 @cindex collected data discarded
13330 This command starts the trace experiment, and begins collecting data.
13331 It has the side effect of discarding all the data collected in the
13332 trace buffer during the previous trace experiment. If any arguments
13333 are supplied, they are taken as a note and stored with the trace
13334 experiment's state. The notes may be arbitrary text, and are
13335 especially useful with disconnected tracing in a multi-user context;
13336 the notes can explain what the trace is doing, supply user contact
13337 information, and so forth.
13339 @kindex tstop [ @var{notes} ]
13340 @cindex stop a running trace experiment
13342 This command stops the trace experiment. If any arguments are
13343 supplied, they are recorded with the experiment as a note. This is
13344 useful if you are stopping a trace started by someone else, for
13345 instance if the trace is interfering with the system's behavior and
13346 needs to be stopped quickly.
13348 @strong{Note}: a trace experiment and data collection may stop
13349 automatically if any tracepoint's passcount is reached
13350 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13353 @cindex status of trace data collection
13354 @cindex trace experiment, status of
13356 This command displays the status of the current trace data
13360 Here is an example of the commands we described so far:
13363 (@value{GDBP}) @b{trace gdb_c_test}
13364 (@value{GDBP}) @b{actions}
13365 Enter actions for tracepoint #1, one per line.
13366 > collect $regs,$locals,$args
13367 > while-stepping 11
13371 (@value{GDBP}) @b{tstart}
13372 [time passes @dots{}]
13373 (@value{GDBP}) @b{tstop}
13376 @anchor{disconnected tracing}
13377 @cindex disconnected tracing
13378 You can choose to continue running the trace experiment even if
13379 @value{GDBN} disconnects from the target, voluntarily or
13380 involuntarily. For commands such as @code{detach}, the debugger will
13381 ask what you want to do with the trace. But for unexpected
13382 terminations (@value{GDBN} crash, network outage), it would be
13383 unfortunate to lose hard-won trace data, so the variable
13384 @code{disconnected-tracing} lets you decide whether the trace should
13385 continue running without @value{GDBN}.
13388 @item set disconnected-tracing on
13389 @itemx set disconnected-tracing off
13390 @kindex set disconnected-tracing
13391 Choose whether a tracing run should continue to run if @value{GDBN}
13392 has disconnected from the target. Note that @code{detach} or
13393 @code{quit} will ask you directly what to do about a running trace no
13394 matter what this variable's setting, so the variable is mainly useful
13395 for handling unexpected situations, such as loss of the network.
13397 @item show disconnected-tracing
13398 @kindex show disconnected-tracing
13399 Show the current choice for disconnected tracing.
13403 When you reconnect to the target, the trace experiment may or may not
13404 still be running; it might have filled the trace buffer in the
13405 meantime, or stopped for one of the other reasons. If it is running,
13406 it will continue after reconnection.
13408 Upon reconnection, the target will upload information about the
13409 tracepoints in effect. @value{GDBN} will then compare that
13410 information to the set of tracepoints currently defined, and attempt
13411 to match them up, allowing for the possibility that the numbers may
13412 have changed due to creation and deletion in the meantime. If one of
13413 the target's tracepoints does not match any in @value{GDBN}, the
13414 debugger will create a new tracepoint, so that you have a number with
13415 which to specify that tracepoint. This matching-up process is
13416 necessarily heuristic, and it may result in useless tracepoints being
13417 created; you may simply delete them if they are of no use.
13419 @cindex circular trace buffer
13420 If your target agent supports a @dfn{circular trace buffer}, then you
13421 can run a trace experiment indefinitely without filling the trace
13422 buffer; when space runs out, the agent deletes already-collected trace
13423 frames, oldest first, until there is enough room to continue
13424 collecting. This is especially useful if your tracepoints are being
13425 hit too often, and your trace gets terminated prematurely because the
13426 buffer is full. To ask for a circular trace buffer, simply set
13427 @samp{circular-trace-buffer} to on. You can set this at any time,
13428 including during tracing; if the agent can do it, it will change
13429 buffer handling on the fly, otherwise it will not take effect until
13433 @item set circular-trace-buffer on
13434 @itemx set circular-trace-buffer off
13435 @kindex set circular-trace-buffer
13436 Choose whether a tracing run should use a linear or circular buffer
13437 for trace data. A linear buffer will not lose any trace data, but may
13438 fill up prematurely, while a circular buffer will discard old trace
13439 data, but it will have always room for the latest tracepoint hits.
13441 @item show circular-trace-buffer
13442 @kindex show circular-trace-buffer
13443 Show the current choice for the trace buffer. Note that this may not
13444 match the agent's current buffer handling, nor is it guaranteed to
13445 match the setting that might have been in effect during a past run,
13446 for instance if you are looking at frames from a trace file.
13451 @item set trace-buffer-size @var{n}
13452 @itemx set trace-buffer-size unlimited
13453 @kindex set trace-buffer-size
13454 Request that the target use a trace buffer of @var{n} bytes. Not all
13455 targets will honor the request; they may have a compiled-in size for
13456 the trace buffer, or some other limitation. Set to a value of
13457 @code{unlimited} or @code{-1} to let the target use whatever size it
13458 likes. This is also the default.
13460 @item show trace-buffer-size
13461 @kindex show trace-buffer-size
13462 Show the current requested size for the trace buffer. Note that this
13463 will only match the actual size if the target supports size-setting,
13464 and was able to handle the requested size. For instance, if the
13465 target can only change buffer size between runs, this variable will
13466 not reflect the change until the next run starts. Use @code{tstatus}
13467 to get a report of the actual buffer size.
13471 @item set trace-user @var{text}
13472 @kindex set trace-user
13474 @item show trace-user
13475 @kindex show trace-user
13477 @item set trace-notes @var{text}
13478 @kindex set trace-notes
13479 Set the trace run's notes.
13481 @item show trace-notes
13482 @kindex show trace-notes
13483 Show the trace run's notes.
13485 @item set trace-stop-notes @var{text}
13486 @kindex set trace-stop-notes
13487 Set the trace run's stop notes. The handling of the note is as for
13488 @code{tstop} arguments; the set command is convenient way to fix a
13489 stop note that is mistaken or incomplete.
13491 @item show trace-stop-notes
13492 @kindex show trace-stop-notes
13493 Show the trace run's stop notes.
13497 @node Tracepoint Restrictions
13498 @subsection Tracepoint Restrictions
13500 @cindex tracepoint restrictions
13501 There are a number of restrictions on the use of tracepoints. As
13502 described above, tracepoint data gathering occurs on the target
13503 without interaction from @value{GDBN}. Thus the full capabilities of
13504 the debugger are not available during data gathering, and then at data
13505 examination time, you will be limited by only having what was
13506 collected. The following items describe some common problems, but it
13507 is not exhaustive, and you may run into additional difficulties not
13513 Tracepoint expressions are intended to gather objects (lvalues). Thus
13514 the full flexibility of GDB's expression evaluator is not available.
13515 You cannot call functions, cast objects to aggregate types, access
13516 convenience variables or modify values (except by assignment to trace
13517 state variables). Some language features may implicitly call
13518 functions (for instance Objective-C fields with accessors), and therefore
13519 cannot be collected either.
13522 Collection of local variables, either individually or in bulk with
13523 @code{$locals} or @code{$args}, during @code{while-stepping} may
13524 behave erratically. The stepping action may enter a new scope (for
13525 instance by stepping into a function), or the location of the variable
13526 may change (for instance it is loaded into a register). The
13527 tracepoint data recorded uses the location information for the
13528 variables that is correct for the tracepoint location. When the
13529 tracepoint is created, it is not possible, in general, to determine
13530 where the steps of a @code{while-stepping} sequence will advance the
13531 program---particularly if a conditional branch is stepped.
13534 Collection of an incompletely-initialized or partially-destroyed object
13535 may result in something that @value{GDBN} cannot display, or displays
13536 in a misleading way.
13539 When @value{GDBN} displays a pointer to character it automatically
13540 dereferences the pointer to also display characters of the string
13541 being pointed to. However, collecting the pointer during tracing does
13542 not automatically collect the string. You need to explicitly
13543 dereference the pointer and provide size information if you want to
13544 collect not only the pointer, but the memory pointed to. For example,
13545 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13549 It is not possible to collect a complete stack backtrace at a
13550 tracepoint. Instead, you may collect the registers and a few hundred
13551 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13552 (adjust to use the name of the actual stack pointer register on your
13553 target architecture, and the amount of stack you wish to capture).
13554 Then the @code{backtrace} command will show a partial backtrace when
13555 using a trace frame. The number of stack frames that can be examined
13556 depends on the sizes of the frames in the collected stack. Note that
13557 if you ask for a block so large that it goes past the bottom of the
13558 stack, the target agent may report an error trying to read from an
13562 If you do not collect registers at a tracepoint, @value{GDBN} can
13563 infer that the value of @code{$pc} must be the same as the address of
13564 the tracepoint and use that when you are looking at a trace frame
13565 for that tracepoint. However, this cannot work if the tracepoint has
13566 multiple locations (for instance if it was set in a function that was
13567 inlined), or if it has a @code{while-stepping} loop. In those cases
13568 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13573 @node Analyze Collected Data
13574 @section Using the Collected Data
13576 After the tracepoint experiment ends, you use @value{GDBN} commands
13577 for examining the trace data. The basic idea is that each tracepoint
13578 collects a trace @dfn{snapshot} every time it is hit and another
13579 snapshot every time it single-steps. All these snapshots are
13580 consecutively numbered from zero and go into a buffer, and you can
13581 examine them later. The way you examine them is to @dfn{focus} on a
13582 specific trace snapshot. When the remote stub is focused on a trace
13583 snapshot, it will respond to all @value{GDBN} requests for memory and
13584 registers by reading from the buffer which belongs to that snapshot,
13585 rather than from @emph{real} memory or registers of the program being
13586 debugged. This means that @strong{all} @value{GDBN} commands
13587 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13588 behave as if we were currently debugging the program state as it was
13589 when the tracepoint occurred. Any requests for data that are not in
13590 the buffer will fail.
13593 * tfind:: How to select a trace snapshot
13594 * tdump:: How to display all data for a snapshot
13595 * save tracepoints:: How to save tracepoints for a future run
13599 @subsection @code{tfind @var{n}}
13602 @cindex select trace snapshot
13603 @cindex find trace snapshot
13604 The basic command for selecting a trace snapshot from the buffer is
13605 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13606 counting from zero. If no argument @var{n} is given, the next
13607 snapshot is selected.
13609 Here are the various forms of using the @code{tfind} command.
13613 Find the first snapshot in the buffer. This is a synonym for
13614 @code{tfind 0} (since 0 is the number of the first snapshot).
13617 Stop debugging trace snapshots, resume @emph{live} debugging.
13620 Same as @samp{tfind none}.
13623 No argument means find the next trace snapshot or find the first
13624 one if no trace snapshot is selected.
13627 Find the previous trace snapshot before the current one. This permits
13628 retracing earlier steps.
13630 @item tfind tracepoint @var{num}
13631 Find the next snapshot associated with tracepoint @var{num}. Search
13632 proceeds forward from the last examined trace snapshot. If no
13633 argument @var{num} is given, it means find the next snapshot collected
13634 for the same tracepoint as the current snapshot.
13636 @item tfind pc @var{addr}
13637 Find the next snapshot associated with the value @var{addr} of the
13638 program counter. Search proceeds forward from the last examined trace
13639 snapshot. If no argument @var{addr} is given, it means find the next
13640 snapshot with the same value of PC as the current snapshot.
13642 @item tfind outside @var{addr1}, @var{addr2}
13643 Find the next snapshot whose PC is outside the given range of
13644 addresses (exclusive).
13646 @item tfind range @var{addr1}, @var{addr2}
13647 Find the next snapshot whose PC is between @var{addr1} and
13648 @var{addr2} (inclusive).
13650 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13651 Find the next snapshot associated with the source line @var{n}. If
13652 the optional argument @var{file} is given, refer to line @var{n} in
13653 that source file. Search proceeds forward from the last examined
13654 trace snapshot. If no argument @var{n} is given, it means find the
13655 next line other than the one currently being examined; thus saying
13656 @code{tfind line} repeatedly can appear to have the same effect as
13657 stepping from line to line in a @emph{live} debugging session.
13660 The default arguments for the @code{tfind} commands are specifically
13661 designed to make it easy to scan through the trace buffer. For
13662 instance, @code{tfind} with no argument selects the next trace
13663 snapshot, and @code{tfind -} with no argument selects the previous
13664 trace snapshot. So, by giving one @code{tfind} command, and then
13665 simply hitting @key{RET} repeatedly you can examine all the trace
13666 snapshots in order. Or, by saying @code{tfind -} and then hitting
13667 @key{RET} repeatedly you can examine the snapshots in reverse order.
13668 The @code{tfind line} command with no argument selects the snapshot
13669 for the next source line executed. The @code{tfind pc} command with
13670 no argument selects the next snapshot with the same program counter
13671 (PC) as the current frame. The @code{tfind tracepoint} command with
13672 no argument selects the next trace snapshot collected by the same
13673 tracepoint as the current one.
13675 In addition to letting you scan through the trace buffer manually,
13676 these commands make it easy to construct @value{GDBN} scripts that
13677 scan through the trace buffer and print out whatever collected data
13678 you are interested in. Thus, if we want to examine the PC, FP, and SP
13679 registers from each trace frame in the buffer, we can say this:
13682 (@value{GDBP}) @b{tfind start}
13683 (@value{GDBP}) @b{while ($trace_frame != -1)}
13684 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13685 $trace_frame, $pc, $sp, $fp
13689 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13690 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13691 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13692 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13693 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13694 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13695 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13696 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13697 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13698 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13699 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13702 Or, if we want to examine the variable @code{X} at each source line in
13706 (@value{GDBP}) @b{tfind start}
13707 (@value{GDBP}) @b{while ($trace_frame != -1)}
13708 > printf "Frame %d, X == %d\n", $trace_frame, X
13718 @subsection @code{tdump}
13720 @cindex dump all data collected at tracepoint
13721 @cindex tracepoint data, display
13723 This command takes no arguments. It prints all the data collected at
13724 the current trace snapshot.
13727 (@value{GDBP}) @b{trace 444}
13728 (@value{GDBP}) @b{actions}
13729 Enter actions for tracepoint #2, one per line:
13730 > collect $regs, $locals, $args, gdb_long_test
13733 (@value{GDBP}) @b{tstart}
13735 (@value{GDBP}) @b{tfind line 444}
13736 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13738 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13740 (@value{GDBP}) @b{tdump}
13741 Data collected at tracepoint 2, trace frame 1:
13742 d0 0xc4aa0085 -995491707
13746 d4 0x71aea3d 119204413
13749 d7 0x380035 3670069
13750 a0 0x19e24a 1696330
13751 a1 0x3000668 50333288
13753 a3 0x322000 3284992
13754 a4 0x3000698 50333336
13755 a5 0x1ad3cc 1758156
13756 fp 0x30bf3c 0x30bf3c
13757 sp 0x30bf34 0x30bf34
13759 pc 0x20b2c8 0x20b2c8
13763 p = 0x20e5b4 "gdb-test"
13770 gdb_long_test = 17 '\021'
13775 @code{tdump} works by scanning the tracepoint's current collection
13776 actions and printing the value of each expression listed. So
13777 @code{tdump} can fail, if after a run, you change the tracepoint's
13778 actions to mention variables that were not collected during the run.
13780 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13781 uses the collected value of @code{$pc} to distinguish between trace
13782 frames that were collected at the tracepoint hit, and frames that were
13783 collected while stepping. This allows it to correctly choose whether
13784 to display the basic list of collections, or the collections from the
13785 body of the while-stepping loop. However, if @code{$pc} was not collected,
13786 then @code{tdump} will always attempt to dump using the basic collection
13787 list, and may fail if a while-stepping frame does not include all the
13788 same data that is collected at the tracepoint hit.
13789 @c This is getting pretty arcane, example would be good.
13791 @node save tracepoints
13792 @subsection @code{save tracepoints @var{filename}}
13793 @kindex save tracepoints
13794 @kindex save-tracepoints
13795 @cindex save tracepoints for future sessions
13797 This command saves all current tracepoint definitions together with
13798 their actions and passcounts, into a file @file{@var{filename}}
13799 suitable for use in a later debugging session. To read the saved
13800 tracepoint definitions, use the @code{source} command (@pxref{Command
13801 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13802 alias for @w{@code{save tracepoints}}
13804 @node Tracepoint Variables
13805 @section Convenience Variables for Tracepoints
13806 @cindex tracepoint variables
13807 @cindex convenience variables for tracepoints
13810 @vindex $trace_frame
13811 @item (int) $trace_frame
13812 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13813 snapshot is selected.
13815 @vindex $tracepoint
13816 @item (int) $tracepoint
13817 The tracepoint for the current trace snapshot.
13819 @vindex $trace_line
13820 @item (int) $trace_line
13821 The line number for the current trace snapshot.
13823 @vindex $trace_file
13824 @item (char []) $trace_file
13825 The source file for the current trace snapshot.
13827 @vindex $trace_func
13828 @item (char []) $trace_func
13829 The name of the function containing @code{$tracepoint}.
13832 Note: @code{$trace_file} is not suitable for use in @code{printf},
13833 use @code{output} instead.
13835 Here's a simple example of using these convenience variables for
13836 stepping through all the trace snapshots and printing some of their
13837 data. Note that these are not the same as trace state variables,
13838 which are managed by the target.
13841 (@value{GDBP}) @b{tfind start}
13843 (@value{GDBP}) @b{while $trace_frame != -1}
13844 > output $trace_file
13845 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13851 @section Using Trace Files
13852 @cindex trace files
13854 In some situations, the target running a trace experiment may no
13855 longer be available; perhaps it crashed, or the hardware was needed
13856 for a different activity. To handle these cases, you can arrange to
13857 dump the trace data into a file, and later use that file as a source
13858 of trace data, via the @code{target tfile} command.
13863 @item tsave [ -r ] @var{filename}
13864 @itemx tsave [-ctf] @var{dirname}
13865 Save the trace data to @var{filename}. By default, this command
13866 assumes that @var{filename} refers to the host filesystem, so if
13867 necessary @value{GDBN} will copy raw trace data up from the target and
13868 then save it. If the target supports it, you can also supply the
13869 optional argument @code{-r} (``remote'') to direct the target to save
13870 the data directly into @var{filename} in its own filesystem, which may be
13871 more efficient if the trace buffer is very large. (Note, however, that
13872 @code{target tfile} can only read from files accessible to the host.)
13873 By default, this command will save trace frame in tfile format.
13874 You can supply the optional argument @code{-ctf} to save data in CTF
13875 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13876 that can be shared by multiple debugging and tracing tools. Please go to
13877 @indicateurl{http://www.efficios.com/ctf} to get more information.
13879 @kindex target tfile
13883 @item target tfile @var{filename}
13884 @itemx target ctf @var{dirname}
13885 Use the file named @var{filename} or directory named @var{dirname} as
13886 a source of trace data. Commands that examine data work as they do with
13887 a live target, but it is not possible to run any new trace experiments.
13888 @code{tstatus} will report the state of the trace run at the moment
13889 the data was saved, as well as the current trace frame you are examining.
13890 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13894 (@value{GDBP}) target ctf ctf.ctf
13895 (@value{GDBP}) tfind
13896 Found trace frame 0, tracepoint 2
13897 39 ++a; /* set tracepoint 1 here */
13898 (@value{GDBP}) tdump
13899 Data collected at tracepoint 2, trace frame 0:
13903 c = @{"123", "456", "789", "123", "456", "789"@}
13904 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13912 @chapter Debugging Programs That Use Overlays
13915 If your program is too large to fit completely in your target system's
13916 memory, you can sometimes use @dfn{overlays} to work around this
13917 problem. @value{GDBN} provides some support for debugging programs that
13921 * How Overlays Work:: A general explanation of overlays.
13922 * Overlay Commands:: Managing overlays in @value{GDBN}.
13923 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13924 mapped by asking the inferior.
13925 * Overlay Sample Program:: A sample program using overlays.
13928 @node How Overlays Work
13929 @section How Overlays Work
13930 @cindex mapped overlays
13931 @cindex unmapped overlays
13932 @cindex load address, overlay's
13933 @cindex mapped address
13934 @cindex overlay area
13936 Suppose you have a computer whose instruction address space is only 64
13937 kilobytes long, but which has much more memory which can be accessed by
13938 other means: special instructions, segment registers, or memory
13939 management hardware, for example. Suppose further that you want to
13940 adapt a program which is larger than 64 kilobytes to run on this system.
13942 One solution is to identify modules of your program which are relatively
13943 independent, and need not call each other directly; call these modules
13944 @dfn{overlays}. Separate the overlays from the main program, and place
13945 their machine code in the larger memory. Place your main program in
13946 instruction memory, but leave at least enough space there to hold the
13947 largest overlay as well.
13949 Now, to call a function located in an overlay, you must first copy that
13950 overlay's machine code from the large memory into the space set aside
13951 for it in the instruction memory, and then jump to its entry point
13954 @c NB: In the below the mapped area's size is greater or equal to the
13955 @c size of all overlays. This is intentional to remind the developer
13956 @c that overlays don't necessarily need to be the same size.
13960 Data Instruction Larger
13961 Address Space Address Space Address Space
13962 +-----------+ +-----------+ +-----------+
13964 +-----------+ +-----------+ +-----------+<-- overlay 1
13965 | program | | main | .----| overlay 1 | load address
13966 | variables | | program | | +-----------+
13967 | and heap | | | | | |
13968 +-----------+ | | | +-----------+<-- overlay 2
13969 | | +-----------+ | | | load address
13970 +-----------+ | | | .-| overlay 2 |
13972 mapped --->+-----------+ | | +-----------+
13973 address | | | | | |
13974 | overlay | <-' | | |
13975 | area | <---' +-----------+<-- overlay 3
13976 | | <---. | | load address
13977 +-----------+ `--| overlay 3 |
13984 @anchor{A code overlay}A code overlay
13988 The diagram (@pxref{A code overlay}) shows a system with separate data
13989 and instruction address spaces. To map an overlay, the program copies
13990 its code from the larger address space to the instruction address space.
13991 Since the overlays shown here all use the same mapped address, only one
13992 may be mapped at a time. For a system with a single address space for
13993 data and instructions, the diagram would be similar, except that the
13994 program variables and heap would share an address space with the main
13995 program and the overlay area.
13997 An overlay loaded into instruction memory and ready for use is called a
13998 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13999 instruction memory. An overlay not present (or only partially present)
14000 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14001 is its address in the larger memory. The mapped address is also called
14002 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14003 called the @dfn{load memory address}, or @dfn{LMA}.
14005 Unfortunately, overlays are not a completely transparent way to adapt a
14006 program to limited instruction memory. They introduce a new set of
14007 global constraints you must keep in mind as you design your program:
14012 Before calling or returning to a function in an overlay, your program
14013 must make sure that overlay is actually mapped. Otherwise, the call or
14014 return will transfer control to the right address, but in the wrong
14015 overlay, and your program will probably crash.
14018 If the process of mapping an overlay is expensive on your system, you
14019 will need to choose your overlays carefully to minimize their effect on
14020 your program's performance.
14023 The executable file you load onto your system must contain each
14024 overlay's instructions, appearing at the overlay's load address, not its
14025 mapped address. However, each overlay's instructions must be relocated
14026 and its symbols defined as if the overlay were at its mapped address.
14027 You can use GNU linker scripts to specify different load and relocation
14028 addresses for pieces of your program; see @ref{Overlay Description,,,
14029 ld.info, Using ld: the GNU linker}.
14032 The procedure for loading executable files onto your system must be able
14033 to load their contents into the larger address space as well as the
14034 instruction and data spaces.
14038 The overlay system described above is rather simple, and could be
14039 improved in many ways:
14044 If your system has suitable bank switch registers or memory management
14045 hardware, you could use those facilities to make an overlay's load area
14046 contents simply appear at their mapped address in instruction space.
14047 This would probably be faster than copying the overlay to its mapped
14048 area in the usual way.
14051 If your overlays are small enough, you could set aside more than one
14052 overlay area, and have more than one overlay mapped at a time.
14055 You can use overlays to manage data, as well as instructions. In
14056 general, data overlays are even less transparent to your design than
14057 code overlays: whereas code overlays only require care when you call or
14058 return to functions, data overlays require care every time you access
14059 the data. Also, if you change the contents of a data overlay, you
14060 must copy its contents back out to its load address before you can copy a
14061 different data overlay into the same mapped area.
14066 @node Overlay Commands
14067 @section Overlay Commands
14069 To use @value{GDBN}'s overlay support, each overlay in your program must
14070 correspond to a separate section of the executable file. The section's
14071 virtual memory address and load memory address must be the overlay's
14072 mapped and load addresses. Identifying overlays with sections allows
14073 @value{GDBN} to determine the appropriate address of a function or
14074 variable, depending on whether the overlay is mapped or not.
14076 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14077 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14082 Disable @value{GDBN}'s overlay support. When overlay support is
14083 disabled, @value{GDBN} assumes that all functions and variables are
14084 always present at their mapped addresses. By default, @value{GDBN}'s
14085 overlay support is disabled.
14087 @item overlay manual
14088 @cindex manual overlay debugging
14089 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14090 relies on you to tell it which overlays are mapped, and which are not,
14091 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14092 commands described below.
14094 @item overlay map-overlay @var{overlay}
14095 @itemx overlay map @var{overlay}
14096 @cindex map an overlay
14097 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14098 be the name of the object file section containing the overlay. When an
14099 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14100 functions and variables at their mapped addresses. @value{GDBN} assumes
14101 that any other overlays whose mapped ranges overlap that of
14102 @var{overlay} are now unmapped.
14104 @item overlay unmap-overlay @var{overlay}
14105 @itemx overlay unmap @var{overlay}
14106 @cindex unmap an overlay
14107 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14108 must be the name of the object file section containing the overlay.
14109 When an overlay is unmapped, @value{GDBN} assumes it can find the
14110 overlay's functions and variables at their load addresses.
14113 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14114 consults a data structure the overlay manager maintains in the inferior
14115 to see which overlays are mapped. For details, see @ref{Automatic
14116 Overlay Debugging}.
14118 @item overlay load-target
14119 @itemx overlay load
14120 @cindex reloading the overlay table
14121 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14122 re-reads the table @value{GDBN} automatically each time the inferior
14123 stops, so this command should only be necessary if you have changed the
14124 overlay mapping yourself using @value{GDBN}. This command is only
14125 useful when using automatic overlay debugging.
14127 @item overlay list-overlays
14128 @itemx overlay list
14129 @cindex listing mapped overlays
14130 Display a list of the overlays currently mapped, along with their mapped
14131 addresses, load addresses, and sizes.
14135 Normally, when @value{GDBN} prints a code address, it includes the name
14136 of the function the address falls in:
14139 (@value{GDBP}) print main
14140 $3 = @{int ()@} 0x11a0 <main>
14143 When overlay debugging is enabled, @value{GDBN} recognizes code in
14144 unmapped overlays, and prints the names of unmapped functions with
14145 asterisks around them. For example, if @code{foo} is a function in an
14146 unmapped overlay, @value{GDBN} prints it this way:
14149 (@value{GDBP}) overlay list
14150 No sections are mapped.
14151 (@value{GDBP}) print foo
14152 $5 = @{int (int)@} 0x100000 <*foo*>
14155 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14159 (@value{GDBP}) overlay list
14160 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14161 mapped at 0x1016 - 0x104a
14162 (@value{GDBP}) print foo
14163 $6 = @{int (int)@} 0x1016 <foo>
14166 When overlay debugging is enabled, @value{GDBN} can find the correct
14167 address for functions and variables in an overlay, whether or not the
14168 overlay is mapped. This allows most @value{GDBN} commands, like
14169 @code{break} and @code{disassemble}, to work normally, even on unmapped
14170 code. However, @value{GDBN}'s breakpoint support has some limitations:
14174 @cindex breakpoints in overlays
14175 @cindex overlays, setting breakpoints in
14176 You can set breakpoints in functions in unmapped overlays, as long as
14177 @value{GDBN} can write to the overlay at its load address.
14179 @value{GDBN} can not set hardware or simulator-based breakpoints in
14180 unmapped overlays. However, if you set a breakpoint at the end of your
14181 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14182 you are using manual overlay management), @value{GDBN} will re-set its
14183 breakpoints properly.
14187 @node Automatic Overlay Debugging
14188 @section Automatic Overlay Debugging
14189 @cindex automatic overlay debugging
14191 @value{GDBN} can automatically track which overlays are mapped and which
14192 are not, given some simple co-operation from the overlay manager in the
14193 inferior. If you enable automatic overlay debugging with the
14194 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14195 looks in the inferior's memory for certain variables describing the
14196 current state of the overlays.
14198 Here are the variables your overlay manager must define to support
14199 @value{GDBN}'s automatic overlay debugging:
14203 @item @code{_ovly_table}:
14204 This variable must be an array of the following structures:
14209 /* The overlay's mapped address. */
14212 /* The size of the overlay, in bytes. */
14213 unsigned long size;
14215 /* The overlay's load address. */
14218 /* Non-zero if the overlay is currently mapped;
14220 unsigned long mapped;
14224 @item @code{_novlys}:
14225 This variable must be a four-byte signed integer, holding the total
14226 number of elements in @code{_ovly_table}.
14230 To decide whether a particular overlay is mapped or not, @value{GDBN}
14231 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14232 @code{lma} members equal the VMA and LMA of the overlay's section in the
14233 executable file. When @value{GDBN} finds a matching entry, it consults
14234 the entry's @code{mapped} member to determine whether the overlay is
14237 In addition, your overlay manager may define a function called
14238 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14239 will silently set a breakpoint there. If the overlay manager then
14240 calls this function whenever it has changed the overlay table, this
14241 will enable @value{GDBN} to accurately keep track of which overlays
14242 are in program memory, and update any breakpoints that may be set
14243 in overlays. This will allow breakpoints to work even if the
14244 overlays are kept in ROM or other non-writable memory while they
14245 are not being executed.
14247 @node Overlay Sample Program
14248 @section Overlay Sample Program
14249 @cindex overlay example program
14251 When linking a program which uses overlays, you must place the overlays
14252 at their load addresses, while relocating them to run at their mapped
14253 addresses. To do this, you must write a linker script (@pxref{Overlay
14254 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14255 since linker scripts are specific to a particular host system, target
14256 architecture, and target memory layout, this manual cannot provide
14257 portable sample code demonstrating @value{GDBN}'s overlay support.
14259 However, the @value{GDBN} source distribution does contain an overlaid
14260 program, with linker scripts for a few systems, as part of its test
14261 suite. The program consists of the following files from
14262 @file{gdb/testsuite/gdb.base}:
14266 The main program file.
14268 A simple overlay manager, used by @file{overlays.c}.
14273 Overlay modules, loaded and used by @file{overlays.c}.
14276 Linker scripts for linking the test program on the @code{d10v-elf}
14277 and @code{m32r-elf} targets.
14280 You can build the test program using the @code{d10v-elf} GCC
14281 cross-compiler like this:
14284 $ d10v-elf-gcc -g -c overlays.c
14285 $ d10v-elf-gcc -g -c ovlymgr.c
14286 $ d10v-elf-gcc -g -c foo.c
14287 $ d10v-elf-gcc -g -c bar.c
14288 $ d10v-elf-gcc -g -c baz.c
14289 $ d10v-elf-gcc -g -c grbx.c
14290 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14291 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14294 The build process is identical for any other architecture, except that
14295 you must substitute the appropriate compiler and linker script for the
14296 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14300 @chapter Using @value{GDBN} with Different Languages
14303 Although programming languages generally have common aspects, they are
14304 rarely expressed in the same manner. For instance, in ANSI C,
14305 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14306 Modula-2, it is accomplished by @code{p^}. Values can also be
14307 represented (and displayed) differently. Hex numbers in C appear as
14308 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14310 @cindex working language
14311 Language-specific information is built into @value{GDBN} for some languages,
14312 allowing you to express operations like the above in your program's
14313 native language, and allowing @value{GDBN} to output values in a manner
14314 consistent with the syntax of your program's native language. The
14315 language you use to build expressions is called the @dfn{working
14319 * Setting:: Switching between source languages
14320 * Show:: Displaying the language
14321 * Checks:: Type and range checks
14322 * Supported Languages:: Supported languages
14323 * Unsupported Languages:: Unsupported languages
14327 @section Switching Between Source Languages
14329 There are two ways to control the working language---either have @value{GDBN}
14330 set it automatically, or select it manually yourself. You can use the
14331 @code{set language} command for either purpose. On startup, @value{GDBN}
14332 defaults to setting the language automatically. The working language is
14333 used to determine how expressions you type are interpreted, how values
14336 In addition to the working language, every source file that
14337 @value{GDBN} knows about has its own working language. For some object
14338 file formats, the compiler might indicate which language a particular
14339 source file is in. However, most of the time @value{GDBN} infers the
14340 language from the name of the file. The language of a source file
14341 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14342 show each frame appropriately for its own language. There is no way to
14343 set the language of a source file from within @value{GDBN}, but you can
14344 set the language associated with a filename extension. @xref{Show, ,
14345 Displaying the Language}.
14347 This is most commonly a problem when you use a program, such
14348 as @code{cfront} or @code{f2c}, that generates C but is written in
14349 another language. In that case, make the
14350 program use @code{#line} directives in its C output; that way
14351 @value{GDBN} will know the correct language of the source code of the original
14352 program, and will display that source code, not the generated C code.
14355 * Filenames:: Filename extensions and languages.
14356 * Manually:: Setting the working language manually
14357 * Automatically:: Having @value{GDBN} infer the source language
14361 @subsection List of Filename Extensions and Languages
14363 If a source file name ends in one of the following extensions, then
14364 @value{GDBN} infers that its language is the one indicated.
14382 C@t{++} source file
14388 Objective-C source file
14392 Fortran source file
14395 Modula-2 source file
14399 Assembler source file. This actually behaves almost like C, but
14400 @value{GDBN} does not skip over function prologues when stepping.
14403 In addition, you may set the language associated with a filename
14404 extension. @xref{Show, , Displaying the Language}.
14407 @subsection Setting the Working Language
14409 If you allow @value{GDBN} to set the language automatically,
14410 expressions are interpreted the same way in your debugging session and
14413 @kindex set language
14414 If you wish, you may set the language manually. To do this, issue the
14415 command @samp{set language @var{lang}}, where @var{lang} is the name of
14416 a language, such as
14417 @code{c} or @code{modula-2}.
14418 For a list of the supported languages, type @samp{set language}.
14420 Setting the language manually prevents @value{GDBN} from updating the working
14421 language automatically. This can lead to confusion if you try
14422 to debug a program when the working language is not the same as the
14423 source language, when an expression is acceptable to both
14424 languages---but means different things. For instance, if the current
14425 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14433 might not have the effect you intended. In C, this means to add
14434 @code{b} and @code{c} and place the result in @code{a}. The result
14435 printed would be the value of @code{a}. In Modula-2, this means to compare
14436 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14438 @node Automatically
14439 @subsection Having @value{GDBN} Infer the Source Language
14441 To have @value{GDBN} set the working language automatically, use
14442 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14443 then infers the working language. That is, when your program stops in a
14444 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14445 working language to the language recorded for the function in that
14446 frame. If the language for a frame is unknown (that is, if the function
14447 or block corresponding to the frame was defined in a source file that
14448 does not have a recognized extension), the current working language is
14449 not changed, and @value{GDBN} issues a warning.
14451 This may not seem necessary for most programs, which are written
14452 entirely in one source language. However, program modules and libraries
14453 written in one source language can be used by a main program written in
14454 a different source language. Using @samp{set language auto} in this
14455 case frees you from having to set the working language manually.
14458 @section Displaying the Language
14460 The following commands help you find out which language is the
14461 working language, and also what language source files were written in.
14464 @item show language
14465 @anchor{show language}
14466 @kindex show language
14467 Display the current working language. This is the
14468 language you can use with commands such as @code{print} to
14469 build and compute expressions that may involve variables in your program.
14472 @kindex info frame@r{, show the source language}
14473 Display the source language for this frame. This language becomes the
14474 working language if you use an identifier from this frame.
14475 @xref{Frame Info, ,Information about a Frame}, to identify the other
14476 information listed here.
14479 @kindex info source@r{, show the source language}
14480 Display the source language of this source file.
14481 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14482 information listed here.
14485 In unusual circumstances, you may have source files with extensions
14486 not in the standard list. You can then set the extension associated
14487 with a language explicitly:
14490 @item set extension-language @var{ext} @var{language}
14491 @kindex set extension-language
14492 Tell @value{GDBN} that source files with extension @var{ext} are to be
14493 assumed as written in the source language @var{language}.
14495 @item info extensions
14496 @kindex info extensions
14497 List all the filename extensions and the associated languages.
14501 @section Type and Range Checking
14503 Some languages are designed to guard you against making seemingly common
14504 errors through a series of compile- and run-time checks. These include
14505 checking the type of arguments to functions and operators and making
14506 sure mathematical overflows are caught at run time. Checks such as
14507 these help to ensure a program's correctness once it has been compiled
14508 by eliminating type mismatches and providing active checks for range
14509 errors when your program is running.
14511 By default @value{GDBN} checks for these errors according to the
14512 rules of the current source language. Although @value{GDBN} does not check
14513 the statements in your program, it can check expressions entered directly
14514 into @value{GDBN} for evaluation via the @code{print} command, for example.
14517 * Type Checking:: An overview of type checking
14518 * Range Checking:: An overview of range checking
14521 @cindex type checking
14522 @cindex checks, type
14523 @node Type Checking
14524 @subsection An Overview of Type Checking
14526 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14527 arguments to operators and functions have to be of the correct type,
14528 otherwise an error occurs. These checks prevent type mismatch
14529 errors from ever causing any run-time problems. For example,
14532 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14534 (@value{GDBP}) print obj.my_method (0)
14537 (@value{GDBP}) print obj.my_method (0x1234)
14538 Cannot resolve method klass::my_method to any overloaded instance
14541 The second example fails because in C@t{++} the integer constant
14542 @samp{0x1234} is not type-compatible with the pointer parameter type.
14544 For the expressions you use in @value{GDBN} commands, you can tell
14545 @value{GDBN} to not enforce strict type checking or
14546 to treat any mismatches as errors and abandon the expression;
14547 When type checking is disabled, @value{GDBN} successfully evaluates
14548 expressions like the second example above.
14550 Even if type checking is off, there may be other reasons
14551 related to type that prevent @value{GDBN} from evaluating an expression.
14552 For instance, @value{GDBN} does not know how to add an @code{int} and
14553 a @code{struct foo}. These particular type errors have nothing to do
14554 with the language in use and usually arise from expressions which make
14555 little sense to evaluate anyway.
14557 @value{GDBN} provides some additional commands for controlling type checking:
14559 @kindex set check type
14560 @kindex show check type
14562 @item set check type on
14563 @itemx set check type off
14564 Set strict type checking on or off. If any type mismatches occur in
14565 evaluating an expression while type checking is on, @value{GDBN} prints a
14566 message and aborts evaluation of the expression.
14568 @item show check type
14569 Show the current setting of type checking and whether @value{GDBN}
14570 is enforcing strict type checking rules.
14573 @cindex range checking
14574 @cindex checks, range
14575 @node Range Checking
14576 @subsection An Overview of Range Checking
14578 In some languages (such as Modula-2), it is an error to exceed the
14579 bounds of a type; this is enforced with run-time checks. Such range
14580 checking is meant to ensure program correctness by making sure
14581 computations do not overflow, or indices on an array element access do
14582 not exceed the bounds of the array.
14584 For expressions you use in @value{GDBN} commands, you can tell
14585 @value{GDBN} to treat range errors in one of three ways: ignore them,
14586 always treat them as errors and abandon the expression, or issue
14587 warnings but evaluate the expression anyway.
14589 A range error can result from numerical overflow, from exceeding an
14590 array index bound, or when you type a constant that is not a member
14591 of any type. Some languages, however, do not treat overflows as an
14592 error. In many implementations of C, mathematical overflow causes the
14593 result to ``wrap around'' to lower values---for example, if @var{m} is
14594 the largest integer value, and @var{s} is the smallest, then
14597 @var{m} + 1 @result{} @var{s}
14600 This, too, is specific to individual languages, and in some cases
14601 specific to individual compilers or machines. @xref{Supported Languages, ,
14602 Supported Languages}, for further details on specific languages.
14604 @value{GDBN} provides some additional commands for controlling the range checker:
14606 @kindex set check range
14607 @kindex show check range
14609 @item set check range auto
14610 Set range checking on or off based on the current working language.
14611 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14614 @item set check range on
14615 @itemx set check range off
14616 Set range checking on or off, overriding the default setting for the
14617 current working language. A warning is issued if the setting does not
14618 match the language default. If a range error occurs and range checking is on,
14619 then a message is printed and evaluation of the expression is aborted.
14621 @item set check range warn
14622 Output messages when the @value{GDBN} range checker detects a range error,
14623 but attempt to evaluate the expression anyway. Evaluating the
14624 expression may still be impossible for other reasons, such as accessing
14625 memory that the process does not own (a typical example from many Unix
14629 Show the current setting of the range checker, and whether or not it is
14630 being set automatically by @value{GDBN}.
14633 @node Supported Languages
14634 @section Supported Languages
14636 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14637 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14638 @c This is false ...
14639 Some @value{GDBN} features may be used in expressions regardless of the
14640 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14641 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14642 ,Expressions}) can be used with the constructs of any supported
14645 The following sections detail to what degree each source language is
14646 supported by @value{GDBN}. These sections are not meant to be language
14647 tutorials or references, but serve only as a reference guide to what the
14648 @value{GDBN} expression parser accepts, and what input and output
14649 formats should look like for different languages. There are many good
14650 books written on each of these languages; please look to these for a
14651 language reference or tutorial.
14654 * C:: C and C@t{++}
14657 * Objective-C:: Objective-C
14658 * OpenCL C:: OpenCL C
14659 * Fortran:: Fortran
14662 * Modula-2:: Modula-2
14667 @subsection C and C@t{++}
14669 @cindex C and C@t{++}
14670 @cindex expressions in C or C@t{++}
14672 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14673 to both languages. Whenever this is the case, we discuss those languages
14677 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14678 @cindex @sc{gnu} C@t{++}
14679 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14680 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14681 effectively, you must compile your C@t{++} programs with a supported
14682 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14683 compiler (@code{aCC}).
14686 * C Operators:: C and C@t{++} operators
14687 * C Constants:: C and C@t{++} constants
14688 * C Plus Plus Expressions:: C@t{++} expressions
14689 * C Defaults:: Default settings for C and C@t{++}
14690 * C Checks:: C and C@t{++} type and range checks
14691 * Debugging C:: @value{GDBN} and C
14692 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14693 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14697 @subsubsection C and C@t{++} Operators
14699 @cindex C and C@t{++} operators
14701 Operators must be defined on values of specific types. For instance,
14702 @code{+} is defined on numbers, but not on structures. Operators are
14703 often defined on groups of types.
14705 For the purposes of C and C@t{++}, the following definitions hold:
14710 @emph{Integral types} include @code{int} with any of its storage-class
14711 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14714 @emph{Floating-point types} include @code{float}, @code{double}, and
14715 @code{long double} (if supported by the target platform).
14718 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14721 @emph{Scalar types} include all of the above.
14726 The following operators are supported. They are listed here
14727 in order of increasing precedence:
14731 The comma or sequencing operator. Expressions in a comma-separated list
14732 are evaluated from left to right, with the result of the entire
14733 expression being the last expression evaluated.
14736 Assignment. The value of an assignment expression is the value
14737 assigned. Defined on scalar types.
14740 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14741 and translated to @w{@code{@var{a} = @var{a op b}}}.
14742 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14743 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14744 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14747 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14748 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14749 should be of an integral type.
14752 Logical @sc{or}. Defined on integral types.
14755 Logical @sc{and}. Defined on integral types.
14758 Bitwise @sc{or}. Defined on integral types.
14761 Bitwise exclusive-@sc{or}. Defined on integral types.
14764 Bitwise @sc{and}. Defined on integral types.
14767 Equality and inequality. Defined on scalar types. The value of these
14768 expressions is 0 for false and non-zero for true.
14770 @item <@r{, }>@r{, }<=@r{, }>=
14771 Less than, greater than, less than or equal, greater than or equal.
14772 Defined on scalar types. The value of these expressions is 0 for false
14773 and non-zero for true.
14776 left shift, and right shift. Defined on integral types.
14779 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14782 Addition and subtraction. Defined on integral types, floating-point types and
14785 @item *@r{, }/@r{, }%
14786 Multiplication, division, and modulus. Multiplication and division are
14787 defined on integral and floating-point types. Modulus is defined on
14791 Increment and decrement. When appearing before a variable, the
14792 operation is performed before the variable is used in an expression;
14793 when appearing after it, the variable's value is used before the
14794 operation takes place.
14797 Pointer dereferencing. Defined on pointer types. Same precedence as
14801 Address operator. Defined on variables. Same precedence as @code{++}.
14803 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14804 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14805 to examine the address
14806 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14810 Negative. Defined on integral and floating-point types. Same
14811 precedence as @code{++}.
14814 Logical negation. Defined on integral types. Same precedence as
14818 Bitwise complement operator. Defined on integral types. Same precedence as
14823 Structure member, and pointer-to-structure member. For convenience,
14824 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14825 pointer based on the stored type information.
14826 Defined on @code{struct} and @code{union} data.
14829 Dereferences of pointers to members.
14832 Array indexing. @code{@var{a}[@var{i}]} is defined as
14833 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14836 Function parameter list. Same precedence as @code{->}.
14839 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14840 and @code{class} types.
14843 Doubled colons also represent the @value{GDBN} scope operator
14844 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14848 If an operator is redefined in the user code, @value{GDBN} usually
14849 attempts to invoke the redefined version instead of using the operator's
14850 predefined meaning.
14853 @subsubsection C and C@t{++} Constants
14855 @cindex C and C@t{++} constants
14857 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14862 Integer constants are a sequence of digits. Octal constants are
14863 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14864 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14865 @samp{l}, specifying that the constant should be treated as a
14869 Floating point constants are a sequence of digits, followed by a decimal
14870 point, followed by a sequence of digits, and optionally followed by an
14871 exponent. An exponent is of the form:
14872 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14873 sequence of digits. The @samp{+} is optional for positive exponents.
14874 A floating-point constant may also end with a letter @samp{f} or
14875 @samp{F}, specifying that the constant should be treated as being of
14876 the @code{float} (as opposed to the default @code{double}) type; or with
14877 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14881 Enumerated constants consist of enumerated identifiers, or their
14882 integral equivalents.
14885 Character constants are a single character surrounded by single quotes
14886 (@code{'}), or a number---the ordinal value of the corresponding character
14887 (usually its @sc{ascii} value). Within quotes, the single character may
14888 be represented by a letter or by @dfn{escape sequences}, which are of
14889 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14890 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14891 @samp{@var{x}} is a predefined special character---for example,
14892 @samp{\n} for newline.
14894 Wide character constants can be written by prefixing a character
14895 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14896 form of @samp{x}. The target wide character set is used when
14897 computing the value of this constant (@pxref{Character Sets}).
14900 String constants are a sequence of character constants surrounded by
14901 double quotes (@code{"}). Any valid character constant (as described
14902 above) may appear. Double quotes within the string must be preceded by
14903 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14906 Wide string constants can be written by prefixing a string constant
14907 with @samp{L}, as in C. The target wide character set is used when
14908 computing the value of this constant (@pxref{Character Sets}).
14911 Pointer constants are an integral value. You can also write pointers
14912 to constants using the C operator @samp{&}.
14915 Array constants are comma-separated lists surrounded by braces @samp{@{}
14916 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14917 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14918 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14921 @node C Plus Plus Expressions
14922 @subsubsection C@t{++} Expressions
14924 @cindex expressions in C@t{++}
14925 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14927 @cindex debugging C@t{++} programs
14928 @cindex C@t{++} compilers
14929 @cindex debug formats and C@t{++}
14930 @cindex @value{NGCC} and C@t{++}
14932 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14933 the proper compiler and the proper debug format. Currently,
14934 @value{GDBN} works best when debugging C@t{++} code that is compiled
14935 with the most recent version of @value{NGCC} possible. The DWARF
14936 debugging format is preferred; @value{NGCC} defaults to this on most
14937 popular platforms. Other compilers and/or debug formats are likely to
14938 work badly or not at all when using @value{GDBN} to debug C@t{++}
14939 code. @xref{Compilation}.
14944 @cindex member functions
14946 Member function calls are allowed; you can use expressions like
14949 count = aml->GetOriginal(x, y)
14952 @vindex this@r{, inside C@t{++} member functions}
14953 @cindex namespace in C@t{++}
14955 While a member function is active (in the selected stack frame), your
14956 expressions have the same namespace available as the member function;
14957 that is, @value{GDBN} allows implicit references to the class instance
14958 pointer @code{this} following the same rules as C@t{++}. @code{using}
14959 declarations in the current scope are also respected by @value{GDBN}.
14961 @cindex call overloaded functions
14962 @cindex overloaded functions, calling
14963 @cindex type conversions in C@t{++}
14965 You can call overloaded functions; @value{GDBN} resolves the function
14966 call to the right definition, with some restrictions. @value{GDBN} does not
14967 perform overload resolution involving user-defined type conversions,
14968 calls to constructors, or instantiations of templates that do not exist
14969 in the program. It also cannot handle ellipsis argument lists or
14972 It does perform integral conversions and promotions, floating-point
14973 promotions, arithmetic conversions, pointer conversions, conversions of
14974 class objects to base classes, and standard conversions such as those of
14975 functions or arrays to pointers; it requires an exact match on the
14976 number of function arguments.
14978 Overload resolution is always performed, unless you have specified
14979 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14980 ,@value{GDBN} Features for C@t{++}}.
14982 You must specify @code{set overload-resolution off} in order to use an
14983 explicit function signature to call an overloaded function, as in
14985 p 'foo(char,int)'('x', 13)
14988 The @value{GDBN} command-completion facility can simplify this;
14989 see @ref{Completion, ,Command Completion}.
14991 @cindex reference declarations
14993 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14994 references; you can use them in expressions just as you do in C@t{++}
14995 source---they are automatically dereferenced.
14997 In the parameter list shown when @value{GDBN} displays a frame, the values of
14998 reference variables are not displayed (unlike other variables); this
14999 avoids clutter, since references are often used for large structures.
15000 The @emph{address} of a reference variable is always shown, unless
15001 you have specified @samp{set print address off}.
15004 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15005 expressions can use it just as expressions in your program do. Since
15006 one scope may be defined in another, you can use @code{::} repeatedly if
15007 necessary, for example in an expression like
15008 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15009 resolving name scope by reference to source files, in both C and C@t{++}
15010 debugging (@pxref{Variables, ,Program Variables}).
15013 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15018 @subsubsection C and C@t{++} Defaults
15020 @cindex C and C@t{++} defaults
15022 If you allow @value{GDBN} to set range checking automatically, it
15023 defaults to @code{off} whenever the working language changes to
15024 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15025 selects the working language.
15027 If you allow @value{GDBN} to set the language automatically, it
15028 recognizes source files whose names end with @file{.c}, @file{.C}, or
15029 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15030 these files, it sets the working language to C or C@t{++}.
15031 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15032 for further details.
15035 @subsubsection C and C@t{++} Type and Range Checks
15037 @cindex C and C@t{++} checks
15039 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15040 checking is used. However, if you turn type checking off, @value{GDBN}
15041 will allow certain non-standard conversions, such as promoting integer
15042 constants to pointers.
15044 Range checking, if turned on, is done on mathematical operations. Array
15045 indices are not checked, since they are often used to index a pointer
15046 that is not itself an array.
15049 @subsubsection @value{GDBN} and C
15051 The @code{set print union} and @code{show print union} commands apply to
15052 the @code{union} type. When set to @samp{on}, any @code{union} that is
15053 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15054 appears as @samp{@{...@}}.
15056 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15057 with pointers and a memory allocation function. @xref{Expressions,
15060 @node Debugging C Plus Plus
15061 @subsubsection @value{GDBN} Features for C@t{++}
15063 @cindex commands for C@t{++}
15065 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15066 designed specifically for use with C@t{++}. Here is a summary:
15069 @cindex break in overloaded functions
15070 @item @r{breakpoint menus}
15071 When you want a breakpoint in a function whose name is overloaded,
15072 @value{GDBN} has the capability to display a menu of possible breakpoint
15073 locations to help you specify which function definition you want.
15074 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15076 @cindex overloading in C@t{++}
15077 @item rbreak @var{regex}
15078 Setting breakpoints using regular expressions is helpful for setting
15079 breakpoints on overloaded functions that are not members of any special
15081 @xref{Set Breaks, ,Setting Breakpoints}.
15083 @cindex C@t{++} exception handling
15085 @itemx catch rethrow
15087 Debug C@t{++} exception handling using these commands. @xref{Set
15088 Catchpoints, , Setting Catchpoints}.
15090 @cindex inheritance
15091 @item ptype @var{typename}
15092 Print inheritance relationships as well as other information for type
15094 @xref{Symbols, ,Examining the Symbol Table}.
15096 @item info vtbl @var{expression}.
15097 The @code{info vtbl} command can be used to display the virtual
15098 method tables of the object computed by @var{expression}. This shows
15099 one entry per virtual table; there may be multiple virtual tables when
15100 multiple inheritance is in use.
15102 @cindex C@t{++} demangling
15103 @item demangle @var{name}
15104 Demangle @var{name}.
15105 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15107 @cindex C@t{++} symbol display
15108 @item set print demangle
15109 @itemx show print demangle
15110 @itemx set print asm-demangle
15111 @itemx show print asm-demangle
15112 Control whether C@t{++} symbols display in their source form, both when
15113 displaying code as C@t{++} source and when displaying disassemblies.
15114 @xref{Print Settings, ,Print Settings}.
15116 @item set print object
15117 @itemx show print object
15118 Choose whether to print derived (actual) or declared types of objects.
15119 @xref{Print Settings, ,Print Settings}.
15121 @item set print vtbl
15122 @itemx show print vtbl
15123 Control the format for printing virtual function tables.
15124 @xref{Print Settings, ,Print Settings}.
15125 (The @code{vtbl} commands do not work on programs compiled with the HP
15126 ANSI C@t{++} compiler (@code{aCC}).)
15128 @kindex set overload-resolution
15129 @cindex overloaded functions, overload resolution
15130 @item set overload-resolution on
15131 Enable overload resolution for C@t{++} expression evaluation. The default
15132 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15133 and searches for a function whose signature matches the argument types,
15134 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15135 Expressions, ,C@t{++} Expressions}, for details).
15136 If it cannot find a match, it emits a message.
15138 @item set overload-resolution off
15139 Disable overload resolution for C@t{++} expression evaluation. For
15140 overloaded functions that are not class member functions, @value{GDBN}
15141 chooses the first function of the specified name that it finds in the
15142 symbol table, whether or not its arguments are of the correct type. For
15143 overloaded functions that are class member functions, @value{GDBN}
15144 searches for a function whose signature @emph{exactly} matches the
15147 @kindex show overload-resolution
15148 @item show overload-resolution
15149 Show the current setting of overload resolution.
15151 @item @r{Overloaded symbol names}
15152 You can specify a particular definition of an overloaded symbol, using
15153 the same notation that is used to declare such symbols in C@t{++}: type
15154 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15155 also use the @value{GDBN} command-line word completion facilities to list the
15156 available choices, or to finish the type list for you.
15157 @xref{Completion,, Command Completion}, for details on how to do this.
15159 @item @r{Breakpoints in functions with ABI tags}
15161 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15162 correspond to changes in the ABI of a type, function, or variable that
15163 would not otherwise be reflected in a mangled name. See
15164 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15167 The ABI tags are visible in C@t{++} demangled names. For example, a
15168 function that returns a std::string:
15171 std::string function(int);
15175 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15176 tag, and @value{GDBN} displays the symbol like this:
15179 function[abi:cxx11](int)
15182 You can set a breakpoint on such functions simply as if they had no
15186 (gdb) b function(int)
15187 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15188 (gdb) info breakpoints
15189 Num Type Disp Enb Address What
15190 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15194 On the rare occasion you need to disambiguate between different ABI
15195 tags, you can do so by simply including the ABI tag in the function
15199 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15203 @node Decimal Floating Point
15204 @subsubsection Decimal Floating Point format
15205 @cindex decimal floating point format
15207 @value{GDBN} can examine, set and perform computations with numbers in
15208 decimal floating point format, which in the C language correspond to the
15209 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15210 specified by the extension to support decimal floating-point arithmetic.
15212 There are two encodings in use, depending on the architecture: BID (Binary
15213 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15214 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15217 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15218 to manipulate decimal floating point numbers, it is not possible to convert
15219 (using a cast, for example) integers wider than 32-bit to decimal float.
15221 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15222 point computations, error checking in decimal float operations ignores
15223 underflow, overflow and divide by zero exceptions.
15225 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15226 to inspect @code{_Decimal128} values stored in floating point registers.
15227 See @ref{PowerPC,,PowerPC} for more details.
15233 @value{GDBN} can be used to debug programs written in D and compiled with
15234 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15235 specific feature --- dynamic arrays.
15240 @cindex Go (programming language)
15241 @value{GDBN} can be used to debug programs written in Go and compiled with
15242 @file{gccgo} or @file{6g} compilers.
15244 Here is a summary of the Go-specific features and restrictions:
15247 @cindex current Go package
15248 @item The current Go package
15249 The name of the current package does not need to be specified when
15250 specifying global variables and functions.
15252 For example, given the program:
15256 var myglob = "Shall we?"
15262 When stopped inside @code{main} either of these work:
15266 (gdb) p main.myglob
15269 @cindex builtin Go types
15270 @item Builtin Go types
15271 The @code{string} type is recognized by @value{GDBN} and is printed
15274 @cindex builtin Go functions
15275 @item Builtin Go functions
15276 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15277 function and handles it internally.
15279 @cindex restrictions on Go expressions
15280 @item Restrictions on Go expressions
15281 All Go operators are supported except @code{&^}.
15282 The Go @code{_} ``blank identifier'' is not supported.
15283 Automatic dereferencing of pointers is not supported.
15287 @subsection Objective-C
15289 @cindex Objective-C
15290 This section provides information about some commands and command
15291 options that are useful for debugging Objective-C code. See also
15292 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15293 few more commands specific to Objective-C support.
15296 * Method Names in Commands::
15297 * The Print Command with Objective-C::
15300 @node Method Names in Commands
15301 @subsubsection Method Names in Commands
15303 The following commands have been extended to accept Objective-C method
15304 names as line specifications:
15306 @kindex clear@r{, and Objective-C}
15307 @kindex break@r{, and Objective-C}
15308 @kindex info line@r{, and Objective-C}
15309 @kindex jump@r{, and Objective-C}
15310 @kindex list@r{, and Objective-C}
15314 @item @code{info line}
15319 A fully qualified Objective-C method name is specified as
15322 -[@var{Class} @var{methodName}]
15325 where the minus sign is used to indicate an instance method and a
15326 plus sign (not shown) is used to indicate a class method. The class
15327 name @var{Class} and method name @var{methodName} are enclosed in
15328 brackets, similar to the way messages are specified in Objective-C
15329 source code. For example, to set a breakpoint at the @code{create}
15330 instance method of class @code{Fruit} in the program currently being
15334 break -[Fruit create]
15337 To list ten program lines around the @code{initialize} class method,
15341 list +[NSText initialize]
15344 In the current version of @value{GDBN}, the plus or minus sign is
15345 required. In future versions of @value{GDBN}, the plus or minus
15346 sign will be optional, but you can use it to narrow the search. It
15347 is also possible to specify just a method name:
15353 You must specify the complete method name, including any colons. If
15354 your program's source files contain more than one @code{create} method,
15355 you'll be presented with a numbered list of classes that implement that
15356 method. Indicate your choice by number, or type @samp{0} to exit if
15359 As another example, to clear a breakpoint established at the
15360 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15363 clear -[NSWindow makeKeyAndOrderFront:]
15366 @node The Print Command with Objective-C
15367 @subsubsection The Print Command With Objective-C
15368 @cindex Objective-C, print objects
15369 @kindex print-object
15370 @kindex po @r{(@code{print-object})}
15372 The print command has also been extended to accept methods. For example:
15375 print -[@var{object} hash]
15378 @cindex print an Objective-C object description
15379 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15381 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15382 and print the result. Also, an additional command has been added,
15383 @code{print-object} or @code{po} for short, which is meant to print
15384 the description of an object. However, this command may only work
15385 with certain Objective-C libraries that have a particular hook
15386 function, @code{_NSPrintForDebugger}, defined.
15389 @subsection OpenCL C
15392 This section provides information about @value{GDBN}s OpenCL C support.
15395 * OpenCL C Datatypes::
15396 * OpenCL C Expressions::
15397 * OpenCL C Operators::
15400 @node OpenCL C Datatypes
15401 @subsubsection OpenCL C Datatypes
15403 @cindex OpenCL C Datatypes
15404 @value{GDBN} supports the builtin scalar and vector datatypes specified
15405 by OpenCL 1.1. In addition the half- and double-precision floating point
15406 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15407 extensions are also known to @value{GDBN}.
15409 @node OpenCL C Expressions
15410 @subsubsection OpenCL C Expressions
15412 @cindex OpenCL C Expressions
15413 @value{GDBN} supports accesses to vector components including the access as
15414 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15415 supported by @value{GDBN} can be used as well.
15417 @node OpenCL C Operators
15418 @subsubsection OpenCL C Operators
15420 @cindex OpenCL C Operators
15421 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15425 @subsection Fortran
15426 @cindex Fortran-specific support in @value{GDBN}
15428 @value{GDBN} can be used to debug programs written in Fortran, but it
15429 currently supports only the features of Fortran 77 language.
15431 @cindex trailing underscore, in Fortran symbols
15432 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15433 among them) append an underscore to the names of variables and
15434 functions. When you debug programs compiled by those compilers, you
15435 will need to refer to variables and functions with a trailing
15439 * Fortran Operators:: Fortran operators and expressions
15440 * Fortran Defaults:: Default settings for Fortran
15441 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15444 @node Fortran Operators
15445 @subsubsection Fortran Operators and Expressions
15447 @cindex Fortran operators and expressions
15449 Operators must be defined on values of specific types. For instance,
15450 @code{+} is defined on numbers, but not on characters or other non-
15451 arithmetic types. Operators are often defined on groups of types.
15455 The exponentiation operator. It raises the first operand to the power
15459 The range operator. Normally used in the form of array(low:high) to
15460 represent a section of array.
15463 The access component operator. Normally used to access elements in derived
15464 types. Also suitable for unions. As unions aren't part of regular Fortran,
15465 this can only happen when accessing a register that uses a gdbarch-defined
15469 @node Fortran Defaults
15470 @subsubsection Fortran Defaults
15472 @cindex Fortran Defaults
15474 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15475 default uses case-insensitive matches for Fortran symbols. You can
15476 change that with the @samp{set case-insensitive} command, see
15477 @ref{Symbols}, for the details.
15479 @node Special Fortran Commands
15480 @subsubsection Special Fortran Commands
15482 @cindex Special Fortran commands
15484 @value{GDBN} has some commands to support Fortran-specific features,
15485 such as displaying common blocks.
15488 @cindex @code{COMMON} blocks, Fortran
15489 @kindex info common
15490 @item info common @r{[}@var{common-name}@r{]}
15491 This command prints the values contained in the Fortran @code{COMMON}
15492 block whose name is @var{common-name}. With no argument, the names of
15493 all @code{COMMON} blocks visible at the current program location are
15500 @cindex Pascal support in @value{GDBN}, limitations
15501 Debugging Pascal programs which use sets, subranges, file variables, or
15502 nested functions does not currently work. @value{GDBN} does not support
15503 entering expressions, printing values, or similar features using Pascal
15506 The Pascal-specific command @code{set print pascal_static-members}
15507 controls whether static members of Pascal objects are displayed.
15508 @xref{Print Settings, pascal_static-members}.
15513 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15514 Programming Language}. Type- and value-printing, and expression
15515 parsing, are reasonably complete. However, there are a few
15516 peculiarities and holes to be aware of.
15520 Linespecs (@pxref{Specify Location}) are never relative to the current
15521 crate. Instead, they act as if there were a global namespace of
15522 crates, somewhat similar to the way @code{extern crate} behaves.
15524 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15525 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15526 to set a breakpoint in a function named @samp{f} in a crate named
15529 As a consequence of this approach, linespecs also cannot refer to
15530 items using @samp{self::} or @samp{super::}.
15533 Because @value{GDBN} implements Rust name-lookup semantics in
15534 expressions, it will sometimes prepend the current crate to a name.
15535 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15536 @samp{K}, then @code{print ::x::y} will try to find the symbol
15539 However, since it is useful to be able to refer to other crates when
15540 debugging, @value{GDBN} provides the @code{extern} extension to
15541 circumvent this. To use the extension, just put @code{extern} before
15542 a path expression to refer to the otherwise unavailable ``global''
15545 In the above example, if you wanted to refer to the symbol @samp{y} in
15546 the crate @samp{x}, you would use @code{print extern x::y}.
15549 The Rust expression evaluator does not support ``statement-like''
15550 expressions such as @code{if} or @code{match}, or lambda expressions.
15553 Tuple expressions are not implemented.
15556 The Rust expression evaluator does not currently implement the
15557 @code{Drop} trait. Objects that may be created by the evaluator will
15558 never be destroyed.
15561 @value{GDBN} does not implement type inference for generics. In order
15562 to call generic functions or otherwise refer to generic items, you
15563 will have to specify the type parameters manually.
15566 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15567 cases this does not cause any problems. However, in an expression
15568 context, completing a generic function name will give syntactically
15569 invalid results. This happens because Rust requires the @samp{::}
15570 operator between the function name and its generic arguments. For
15571 example, @value{GDBN} might provide a completion like
15572 @code{crate::f<u32>}, where the parser would require
15573 @code{crate::f::<u32>}.
15576 As of this writing, the Rust compiler (version 1.8) has a few holes in
15577 the debugging information it generates. These holes prevent certain
15578 features from being implemented by @value{GDBN}:
15582 Method calls cannot be made via traits.
15585 Operator overloading is not implemented.
15588 When debugging in a monomorphized function, you cannot use the generic
15592 The type @code{Self} is not available.
15595 @code{use} statements are not available, so some names may not be
15596 available in the crate.
15601 @subsection Modula-2
15603 @cindex Modula-2, @value{GDBN} support
15605 The extensions made to @value{GDBN} to support Modula-2 only support
15606 output from the @sc{gnu} Modula-2 compiler (which is currently being
15607 developed). Other Modula-2 compilers are not currently supported, and
15608 attempting to debug executables produced by them is most likely
15609 to give an error as @value{GDBN} reads in the executable's symbol
15612 @cindex expressions in Modula-2
15614 * M2 Operators:: Built-in operators
15615 * Built-In Func/Proc:: Built-in functions and procedures
15616 * M2 Constants:: Modula-2 constants
15617 * M2 Types:: Modula-2 types
15618 * M2 Defaults:: Default settings for Modula-2
15619 * Deviations:: Deviations from standard Modula-2
15620 * M2 Checks:: Modula-2 type and range checks
15621 * M2 Scope:: The scope operators @code{::} and @code{.}
15622 * GDB/M2:: @value{GDBN} and Modula-2
15626 @subsubsection Operators
15627 @cindex Modula-2 operators
15629 Operators must be defined on values of specific types. For instance,
15630 @code{+} is defined on numbers, but not on structures. Operators are
15631 often defined on groups of types. For the purposes of Modula-2, the
15632 following definitions hold:
15637 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15641 @emph{Character types} consist of @code{CHAR} and its subranges.
15644 @emph{Floating-point types} consist of @code{REAL}.
15647 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15651 @emph{Scalar types} consist of all of the above.
15654 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15657 @emph{Boolean types} consist of @code{BOOLEAN}.
15661 The following operators are supported, and appear in order of
15662 increasing precedence:
15666 Function argument or array index separator.
15669 Assignment. The value of @var{var} @code{:=} @var{value} is
15673 Less than, greater than on integral, floating-point, or enumerated
15677 Less than or equal to, greater than or equal to
15678 on integral, floating-point and enumerated types, or set inclusion on
15679 set types. Same precedence as @code{<}.
15681 @item =@r{, }<>@r{, }#
15682 Equality and two ways of expressing inequality, valid on scalar types.
15683 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15684 available for inequality, since @code{#} conflicts with the script
15688 Set membership. Defined on set types and the types of their members.
15689 Same precedence as @code{<}.
15692 Boolean disjunction. Defined on boolean types.
15695 Boolean conjunction. Defined on boolean types.
15698 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15701 Addition and subtraction on integral and floating-point types, or union
15702 and difference on set types.
15705 Multiplication on integral and floating-point types, or set intersection
15709 Division on floating-point types, or symmetric set difference on set
15710 types. Same precedence as @code{*}.
15713 Integer division and remainder. Defined on integral types. Same
15714 precedence as @code{*}.
15717 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15720 Pointer dereferencing. Defined on pointer types.
15723 Boolean negation. Defined on boolean types. Same precedence as
15727 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15728 precedence as @code{^}.
15731 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15734 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15738 @value{GDBN} and Modula-2 scope operators.
15742 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15743 treats the use of the operator @code{IN}, or the use of operators
15744 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15745 @code{<=}, and @code{>=} on sets as an error.
15749 @node Built-In Func/Proc
15750 @subsubsection Built-in Functions and Procedures
15751 @cindex Modula-2 built-ins
15753 Modula-2 also makes available several built-in procedures and functions.
15754 In describing these, the following metavariables are used:
15759 represents an @code{ARRAY} variable.
15762 represents a @code{CHAR} constant or variable.
15765 represents a variable or constant of integral type.
15768 represents an identifier that belongs to a set. Generally used in the
15769 same function with the metavariable @var{s}. The type of @var{s} should
15770 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15773 represents a variable or constant of integral or floating-point type.
15776 represents a variable or constant of floating-point type.
15782 represents a variable.
15785 represents a variable or constant of one of many types. See the
15786 explanation of the function for details.
15789 All Modula-2 built-in procedures also return a result, described below.
15793 Returns the absolute value of @var{n}.
15796 If @var{c} is a lower case letter, it returns its upper case
15797 equivalent, otherwise it returns its argument.
15800 Returns the character whose ordinal value is @var{i}.
15803 Decrements the value in the variable @var{v} by one. Returns the new value.
15805 @item DEC(@var{v},@var{i})
15806 Decrements the value in the variable @var{v} by @var{i}. Returns the
15809 @item EXCL(@var{m},@var{s})
15810 Removes the element @var{m} from the set @var{s}. Returns the new
15813 @item FLOAT(@var{i})
15814 Returns the floating point equivalent of the integer @var{i}.
15816 @item HIGH(@var{a})
15817 Returns the index of the last member of @var{a}.
15820 Increments the value in the variable @var{v} by one. Returns the new value.
15822 @item INC(@var{v},@var{i})
15823 Increments the value in the variable @var{v} by @var{i}. Returns the
15826 @item INCL(@var{m},@var{s})
15827 Adds the element @var{m} to the set @var{s} if it is not already
15828 there. Returns the new set.
15831 Returns the maximum value of the type @var{t}.
15834 Returns the minimum value of the type @var{t}.
15837 Returns boolean TRUE if @var{i} is an odd number.
15840 Returns the ordinal value of its argument. For example, the ordinal
15841 value of a character is its @sc{ascii} value (on machines supporting
15842 the @sc{ascii} character set). The argument @var{x} must be of an
15843 ordered type, which include integral, character and enumerated types.
15845 @item SIZE(@var{x})
15846 Returns the size of its argument. The argument @var{x} can be a
15847 variable or a type.
15849 @item TRUNC(@var{r})
15850 Returns the integral part of @var{r}.
15852 @item TSIZE(@var{x})
15853 Returns the size of its argument. The argument @var{x} can be a
15854 variable or a type.
15856 @item VAL(@var{t},@var{i})
15857 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15861 @emph{Warning:} Sets and their operations are not yet supported, so
15862 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15866 @cindex Modula-2 constants
15868 @subsubsection Constants
15870 @value{GDBN} allows you to express the constants of Modula-2 in the following
15876 Integer constants are simply a sequence of digits. When used in an
15877 expression, a constant is interpreted to be type-compatible with the
15878 rest of the expression. Hexadecimal integers are specified by a
15879 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15882 Floating point constants appear as a sequence of digits, followed by a
15883 decimal point and another sequence of digits. An optional exponent can
15884 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15885 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15886 digits of the floating point constant must be valid decimal (base 10)
15890 Character constants consist of a single character enclosed by a pair of
15891 like quotes, either single (@code{'}) or double (@code{"}). They may
15892 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15893 followed by a @samp{C}.
15896 String constants consist of a sequence of characters enclosed by a
15897 pair of like quotes, either single (@code{'}) or double (@code{"}).
15898 Escape sequences in the style of C are also allowed. @xref{C
15899 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15903 Enumerated constants consist of an enumerated identifier.
15906 Boolean constants consist of the identifiers @code{TRUE} and
15910 Pointer constants consist of integral values only.
15913 Set constants are not yet supported.
15917 @subsubsection Modula-2 Types
15918 @cindex Modula-2 types
15920 Currently @value{GDBN} can print the following data types in Modula-2
15921 syntax: array types, record types, set types, pointer types, procedure
15922 types, enumerated types, subrange types and base types. You can also
15923 print the contents of variables declared using these type.
15924 This section gives a number of simple source code examples together with
15925 sample @value{GDBN} sessions.
15927 The first example contains the following section of code:
15936 and you can request @value{GDBN} to interrogate the type and value of
15937 @code{r} and @code{s}.
15940 (@value{GDBP}) print s
15942 (@value{GDBP}) ptype s
15944 (@value{GDBP}) print r
15946 (@value{GDBP}) ptype r
15951 Likewise if your source code declares @code{s} as:
15955 s: SET ['A'..'Z'] ;
15959 then you may query the type of @code{s} by:
15962 (@value{GDBP}) ptype s
15963 type = SET ['A'..'Z']
15967 Note that at present you cannot interactively manipulate set
15968 expressions using the debugger.
15970 The following example shows how you might declare an array in Modula-2
15971 and how you can interact with @value{GDBN} to print its type and contents:
15975 s: ARRAY [-10..10] OF CHAR ;
15979 (@value{GDBP}) ptype s
15980 ARRAY [-10..10] OF CHAR
15983 Note that the array handling is not yet complete and although the type
15984 is printed correctly, expression handling still assumes that all
15985 arrays have a lower bound of zero and not @code{-10} as in the example
15988 Here are some more type related Modula-2 examples:
15992 colour = (blue, red, yellow, green) ;
15993 t = [blue..yellow] ;
16001 The @value{GDBN} interaction shows how you can query the data type
16002 and value of a variable.
16005 (@value{GDBP}) print s
16007 (@value{GDBP}) ptype t
16008 type = [blue..yellow]
16012 In this example a Modula-2 array is declared and its contents
16013 displayed. Observe that the contents are written in the same way as
16014 their @code{C} counterparts.
16018 s: ARRAY [1..5] OF CARDINAL ;
16024 (@value{GDBP}) print s
16025 $1 = @{1, 0, 0, 0, 0@}
16026 (@value{GDBP}) ptype s
16027 type = ARRAY [1..5] OF CARDINAL
16030 The Modula-2 language interface to @value{GDBN} also understands
16031 pointer types as shown in this example:
16035 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16042 and you can request that @value{GDBN} describes the type of @code{s}.
16045 (@value{GDBP}) ptype s
16046 type = POINTER TO ARRAY [1..5] OF CARDINAL
16049 @value{GDBN} handles compound types as we can see in this example.
16050 Here we combine array types, record types, pointer types and subrange
16061 myarray = ARRAY myrange OF CARDINAL ;
16062 myrange = [-2..2] ;
16064 s: POINTER TO ARRAY myrange OF foo ;
16068 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16072 (@value{GDBP}) ptype s
16073 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16076 f3 : ARRAY [-2..2] OF CARDINAL;
16081 @subsubsection Modula-2 Defaults
16082 @cindex Modula-2 defaults
16084 If type and range checking are set automatically by @value{GDBN}, they
16085 both default to @code{on} whenever the working language changes to
16086 Modula-2. This happens regardless of whether you or @value{GDBN}
16087 selected the working language.
16089 If you allow @value{GDBN} to set the language automatically, then entering
16090 code compiled from a file whose name ends with @file{.mod} sets the
16091 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16092 Infer the Source Language}, for further details.
16095 @subsubsection Deviations from Standard Modula-2
16096 @cindex Modula-2, deviations from
16098 A few changes have been made to make Modula-2 programs easier to debug.
16099 This is done primarily via loosening its type strictness:
16103 Unlike in standard Modula-2, pointer constants can be formed by
16104 integers. This allows you to modify pointer variables during
16105 debugging. (In standard Modula-2, the actual address contained in a
16106 pointer variable is hidden from you; it can only be modified
16107 through direct assignment to another pointer variable or expression that
16108 returned a pointer.)
16111 C escape sequences can be used in strings and characters to represent
16112 non-printable characters. @value{GDBN} prints out strings with these
16113 escape sequences embedded. Single non-printable characters are
16114 printed using the @samp{CHR(@var{nnn})} format.
16117 The assignment operator (@code{:=}) returns the value of its right-hand
16121 All built-in procedures both modify @emph{and} return their argument.
16125 @subsubsection Modula-2 Type and Range Checks
16126 @cindex Modula-2 checks
16129 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16132 @c FIXME remove warning when type/range checks added
16134 @value{GDBN} considers two Modula-2 variables type equivalent if:
16138 They are of types that have been declared equivalent via a @code{TYPE
16139 @var{t1} = @var{t2}} statement
16142 They have been declared on the same line. (Note: This is true of the
16143 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16146 As long as type checking is enabled, any attempt to combine variables
16147 whose types are not equivalent is an error.
16149 Range checking is done on all mathematical operations, assignment, array
16150 index bounds, and all built-in functions and procedures.
16153 @subsubsection The Scope Operators @code{::} and @code{.}
16155 @cindex @code{.}, Modula-2 scope operator
16156 @cindex colon, doubled as scope operator
16158 @vindex colon-colon@r{, in Modula-2}
16159 @c Info cannot handle :: but TeX can.
16162 @vindex ::@r{, in Modula-2}
16165 There are a few subtle differences between the Modula-2 scope operator
16166 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16171 @var{module} . @var{id}
16172 @var{scope} :: @var{id}
16176 where @var{scope} is the name of a module or a procedure,
16177 @var{module} the name of a module, and @var{id} is any declared
16178 identifier within your program, except another module.
16180 Using the @code{::} operator makes @value{GDBN} search the scope
16181 specified by @var{scope} for the identifier @var{id}. If it is not
16182 found in the specified scope, then @value{GDBN} searches all scopes
16183 enclosing the one specified by @var{scope}.
16185 Using the @code{.} operator makes @value{GDBN} search the current scope for
16186 the identifier specified by @var{id} that was imported from the
16187 definition module specified by @var{module}. With this operator, it is
16188 an error if the identifier @var{id} was not imported from definition
16189 module @var{module}, or if @var{id} is not an identifier in
16193 @subsubsection @value{GDBN} and Modula-2
16195 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16196 Five subcommands of @code{set print} and @code{show print} apply
16197 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16198 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16199 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16200 analogue in Modula-2.
16202 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16203 with any language, is not useful with Modula-2. Its
16204 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16205 created in Modula-2 as they can in C or C@t{++}. However, because an
16206 address can be specified by an integral constant, the construct
16207 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16209 @cindex @code{#} in Modula-2
16210 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16211 interpreted as the beginning of a comment. Use @code{<>} instead.
16217 The extensions made to @value{GDBN} for Ada only support
16218 output from the @sc{gnu} Ada (GNAT) compiler.
16219 Other Ada compilers are not currently supported, and
16220 attempting to debug executables produced by them is most likely
16224 @cindex expressions in Ada
16226 * Ada Mode Intro:: General remarks on the Ada syntax
16227 and semantics supported by Ada mode
16229 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16230 * Additions to Ada:: Extensions of the Ada expression syntax.
16231 * Overloading support for Ada:: Support for expressions involving overloaded
16233 * Stopping Before Main Program:: Debugging the program during elaboration.
16234 * Ada Exceptions:: Ada Exceptions
16235 * Ada Tasks:: Listing and setting breakpoints in tasks.
16236 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16237 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16239 * Ada Glitches:: Known peculiarities of Ada mode.
16242 @node Ada Mode Intro
16243 @subsubsection Introduction
16244 @cindex Ada mode, general
16246 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16247 syntax, with some extensions.
16248 The philosophy behind the design of this subset is
16252 That @value{GDBN} should provide basic literals and access to operations for
16253 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16254 leaving more sophisticated computations to subprograms written into the
16255 program (which therefore may be called from @value{GDBN}).
16258 That type safety and strict adherence to Ada language restrictions
16259 are not particularly important to the @value{GDBN} user.
16262 That brevity is important to the @value{GDBN} user.
16265 Thus, for brevity, the debugger acts as if all names declared in
16266 user-written packages are directly visible, even if they are not visible
16267 according to Ada rules, thus making it unnecessary to fully qualify most
16268 names with their packages, regardless of context. Where this causes
16269 ambiguity, @value{GDBN} asks the user's intent.
16271 The debugger will start in Ada mode if it detects an Ada main program.
16272 As for other languages, it will enter Ada mode when stopped in a program that
16273 was translated from an Ada source file.
16275 While in Ada mode, you may use `@t{--}' for comments. This is useful
16276 mostly for documenting command files. The standard @value{GDBN} comment
16277 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16278 middle (to allow based literals).
16280 @node Omissions from Ada
16281 @subsubsection Omissions from Ada
16282 @cindex Ada, omissions from
16284 Here are the notable omissions from the subset:
16288 Only a subset of the attributes are supported:
16292 @t{'First}, @t{'Last}, and @t{'Length}
16293 on array objects (not on types and subtypes).
16296 @t{'Min} and @t{'Max}.
16299 @t{'Pos} and @t{'Val}.
16305 @t{'Range} on array objects (not subtypes), but only as the right
16306 operand of the membership (@code{in}) operator.
16309 @t{'Access}, @t{'Unchecked_Access}, and
16310 @t{'Unrestricted_Access} (a GNAT extension).
16318 @code{Characters.Latin_1} are not available and
16319 concatenation is not implemented. Thus, escape characters in strings are
16320 not currently available.
16323 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16324 equality of representations. They will generally work correctly
16325 for strings and arrays whose elements have integer or enumeration types.
16326 They may not work correctly for arrays whose element
16327 types have user-defined equality, for arrays of real values
16328 (in particular, IEEE-conformant floating point, because of negative
16329 zeroes and NaNs), and for arrays whose elements contain unused bits with
16330 indeterminate values.
16333 The other component-by-component array operations (@code{and}, @code{or},
16334 @code{xor}, @code{not}, and relational tests other than equality)
16335 are not implemented.
16338 @cindex array aggregates (Ada)
16339 @cindex record aggregates (Ada)
16340 @cindex aggregates (Ada)
16341 There is limited support for array and record aggregates. They are
16342 permitted only on the right sides of assignments, as in these examples:
16345 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16346 (@value{GDBP}) set An_Array := (1, others => 0)
16347 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16348 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16349 (@value{GDBP}) set A_Record := (1, "Peter", True);
16350 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16354 discriminant's value by assigning an aggregate has an
16355 undefined effect if that discriminant is used within the record.
16356 However, you can first modify discriminants by directly assigning to
16357 them (which normally would not be allowed in Ada), and then performing an
16358 aggregate assignment. For example, given a variable @code{A_Rec}
16359 declared to have a type such as:
16362 type Rec (Len : Small_Integer := 0) is record
16364 Vals : IntArray (1 .. Len);
16368 you can assign a value with a different size of @code{Vals} with two
16372 (@value{GDBP}) set A_Rec.Len := 4
16373 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16376 As this example also illustrates, @value{GDBN} is very loose about the usual
16377 rules concerning aggregates. You may leave out some of the
16378 components of an array or record aggregate (such as the @code{Len}
16379 component in the assignment to @code{A_Rec} above); they will retain their
16380 original values upon assignment. You may freely use dynamic values as
16381 indices in component associations. You may even use overlapping or
16382 redundant component associations, although which component values are
16383 assigned in such cases is not defined.
16386 Calls to dispatching subprograms are not implemented.
16389 The overloading algorithm is much more limited (i.e., less selective)
16390 than that of real Ada. It makes only limited use of the context in
16391 which a subexpression appears to resolve its meaning, and it is much
16392 looser in its rules for allowing type matches. As a result, some
16393 function calls will be ambiguous, and the user will be asked to choose
16394 the proper resolution.
16397 The @code{new} operator is not implemented.
16400 Entry calls are not implemented.
16403 Aside from printing, arithmetic operations on the native VAX floating-point
16404 formats are not supported.
16407 It is not possible to slice a packed array.
16410 The names @code{True} and @code{False}, when not part of a qualified name,
16411 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16413 Should your program
16414 redefine these names in a package or procedure (at best a dubious practice),
16415 you will have to use fully qualified names to access their new definitions.
16418 @node Additions to Ada
16419 @subsubsection Additions to Ada
16420 @cindex Ada, deviations from
16422 As it does for other languages, @value{GDBN} makes certain generic
16423 extensions to Ada (@pxref{Expressions}):
16427 If the expression @var{E} is a variable residing in memory (typically
16428 a local variable or array element) and @var{N} is a positive integer,
16429 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16430 @var{N}-1 adjacent variables following it in memory as an array. In
16431 Ada, this operator is generally not necessary, since its prime use is
16432 in displaying parts of an array, and slicing will usually do this in
16433 Ada. However, there are occasional uses when debugging programs in
16434 which certain debugging information has been optimized away.
16437 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16438 appears in function or file @var{B}.'' When @var{B} is a file name,
16439 you must typically surround it in single quotes.
16442 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16443 @var{type} that appears at address @var{addr}.''
16446 A name starting with @samp{$} is a convenience variable
16447 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16450 In addition, @value{GDBN} provides a few other shortcuts and outright
16451 additions specific to Ada:
16455 The assignment statement is allowed as an expression, returning
16456 its right-hand operand as its value. Thus, you may enter
16459 (@value{GDBP}) set x := y + 3
16460 (@value{GDBP}) print A(tmp := y + 1)
16464 The semicolon is allowed as an ``operator,'' returning as its value
16465 the value of its right-hand operand.
16466 This allows, for example,
16467 complex conditional breaks:
16470 (@value{GDBP}) break f
16471 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16475 Rather than use catenation and symbolic character names to introduce special
16476 characters into strings, one may instead use a special bracket notation,
16477 which is also used to print strings. A sequence of characters of the form
16478 @samp{["@var{XX}"]} within a string or character literal denotes the
16479 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16480 sequence of characters @samp{["""]} also denotes a single quotation mark
16481 in strings. For example,
16483 "One line.["0a"]Next line.["0a"]"
16486 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16490 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16491 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16495 (@value{GDBP}) print 'max(x, y)
16499 When printing arrays, @value{GDBN} uses positional notation when the
16500 array has a lower bound of 1, and uses a modified named notation otherwise.
16501 For example, a one-dimensional array of three integers with a lower bound
16502 of 3 might print as
16509 That is, in contrast to valid Ada, only the first component has a @code{=>}
16513 You may abbreviate attributes in expressions with any unique,
16514 multi-character subsequence of
16515 their names (an exact match gets preference).
16516 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16517 in place of @t{a'length}.
16520 @cindex quoting Ada internal identifiers
16521 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16522 to lower case. The GNAT compiler uses upper-case characters for
16523 some of its internal identifiers, which are normally of no interest to users.
16524 For the rare occasions when you actually have to look at them,
16525 enclose them in angle brackets to avoid the lower-case mapping.
16528 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16532 Printing an object of class-wide type or dereferencing an
16533 access-to-class-wide value will display all the components of the object's
16534 specific type (as indicated by its run-time tag). Likewise, component
16535 selection on such a value will operate on the specific type of the
16540 @node Overloading support for Ada
16541 @subsubsection Overloading support for Ada
16542 @cindex overloading, Ada
16544 The debugger supports limited overloading. Given a subprogram call in which
16545 the function symbol has multiple definitions, it will use the number of
16546 actual parameters and some information about their types to attempt to narrow
16547 the set of definitions. It also makes very limited use of context, preferring
16548 procedures to functions in the context of the @code{call} command, and
16549 functions to procedures elsewhere.
16551 If, after narrowing, the set of matching definitions still contains more than
16552 one definition, @value{GDBN} will display a menu to query which one it should
16556 (@value{GDBP}) print f(1)
16557 Multiple matches for f
16559 [1] foo.f (integer) return boolean at foo.adb:23
16560 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16564 In this case, just select one menu entry either to cancel expression evaluation
16565 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16566 instance (type the corresponding number and press @key{RET}).
16568 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16573 @kindex set ada print-signatures
16574 @item set ada print-signatures
16575 Control whether parameter types and return types are displayed in overloads
16576 selection menus. It is @code{on} by default.
16577 @xref{Overloading support for Ada}.
16579 @kindex show ada print-signatures
16580 @item show ada print-signatures
16581 Show the current setting for displaying parameter types and return types in
16582 overloads selection menu.
16583 @xref{Overloading support for Ada}.
16587 @node Stopping Before Main Program
16588 @subsubsection Stopping at the Very Beginning
16590 @cindex breakpointing Ada elaboration code
16591 It is sometimes necessary to debug the program during elaboration, and
16592 before reaching the main procedure.
16593 As defined in the Ada Reference
16594 Manual, the elaboration code is invoked from a procedure called
16595 @code{adainit}. To run your program up to the beginning of
16596 elaboration, simply use the following two commands:
16597 @code{tbreak adainit} and @code{run}.
16599 @node Ada Exceptions
16600 @subsubsection Ada Exceptions
16602 A command is provided to list all Ada exceptions:
16605 @kindex info exceptions
16606 @item info exceptions
16607 @itemx info exceptions @var{regexp}
16608 The @code{info exceptions} command allows you to list all Ada exceptions
16609 defined within the program being debugged, as well as their addresses.
16610 With a regular expression, @var{regexp}, as argument, only those exceptions
16611 whose names match @var{regexp} are listed.
16614 Below is a small example, showing how the command can be used, first
16615 without argument, and next with a regular expression passed as an
16619 (@value{GDBP}) info exceptions
16620 All defined Ada exceptions:
16621 constraint_error: 0x613da0
16622 program_error: 0x613d20
16623 storage_error: 0x613ce0
16624 tasking_error: 0x613ca0
16625 const.aint_global_e: 0x613b00
16626 (@value{GDBP}) info exceptions const.aint
16627 All Ada exceptions matching regular expression "const.aint":
16628 constraint_error: 0x613da0
16629 const.aint_global_e: 0x613b00
16632 It is also possible to ask @value{GDBN} to stop your program's execution
16633 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16636 @subsubsection Extensions for Ada Tasks
16637 @cindex Ada, tasking
16639 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16640 @value{GDBN} provides the following task-related commands:
16645 This command shows a list of current Ada tasks, as in the following example:
16652 (@value{GDBP}) info tasks
16653 ID TID P-ID Pri State Name
16654 1 8088000 0 15 Child Activation Wait main_task
16655 2 80a4000 1 15 Accept Statement b
16656 3 809a800 1 15 Child Activation Wait a
16657 * 4 80ae800 3 15 Runnable c
16662 In this listing, the asterisk before the last task indicates it to be the
16663 task currently being inspected.
16667 Represents @value{GDBN}'s internal task number.
16673 The parent's task ID (@value{GDBN}'s internal task number).
16676 The base priority of the task.
16679 Current state of the task.
16683 The task has been created but has not been activated. It cannot be
16687 The task is not blocked for any reason known to Ada. (It may be waiting
16688 for a mutex, though.) It is conceptually "executing" in normal mode.
16691 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16692 that were waiting on terminate alternatives have been awakened and have
16693 terminated themselves.
16695 @item Child Activation Wait
16696 The task is waiting for created tasks to complete activation.
16698 @item Accept Statement
16699 The task is waiting on an accept or selective wait statement.
16701 @item Waiting on entry call
16702 The task is waiting on an entry call.
16704 @item Async Select Wait
16705 The task is waiting to start the abortable part of an asynchronous
16709 The task is waiting on a select statement with only a delay
16712 @item Child Termination Wait
16713 The task is sleeping having completed a master within itself, and is
16714 waiting for the tasks dependent on that master to become terminated or
16715 waiting on a terminate Phase.
16717 @item Wait Child in Term Alt
16718 The task is sleeping waiting for tasks on terminate alternatives to
16719 finish terminating.
16721 @item Accepting RV with @var{taskno}
16722 The task is accepting a rendez-vous with the task @var{taskno}.
16726 Name of the task in the program.
16730 @kindex info task @var{taskno}
16731 @item info task @var{taskno}
16732 This command shows detailled informations on the specified task, as in
16733 the following example:
16738 (@value{GDBP}) info tasks
16739 ID TID P-ID Pri State Name
16740 1 8077880 0 15 Child Activation Wait main_task
16741 * 2 807c468 1 15 Runnable task_1
16742 (@value{GDBP}) info task 2
16743 Ada Task: 0x807c468
16746 Parent: 1 (main_task)
16752 @kindex task@r{ (Ada)}
16753 @cindex current Ada task ID
16754 This command prints the ID of the current task.
16760 (@value{GDBP}) info tasks
16761 ID TID P-ID Pri State Name
16762 1 8077870 0 15 Child Activation Wait main_task
16763 * 2 807c458 1 15 Runnable t
16764 (@value{GDBP}) task
16765 [Current task is 2]
16768 @item task @var{taskno}
16769 @cindex Ada task switching
16770 This command is like the @code{thread @var{thread-id}}
16771 command (@pxref{Threads}). It switches the context of debugging
16772 from the current task to the given task.
16778 (@value{GDBP}) info tasks
16779 ID TID P-ID Pri State Name
16780 1 8077870 0 15 Child Activation Wait main_task
16781 * 2 807c458 1 15 Runnable t
16782 (@value{GDBP}) task 1
16783 [Switching to task 1]
16784 #0 0x8067726 in pthread_cond_wait ()
16786 #0 0x8067726 in pthread_cond_wait ()
16787 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16788 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16789 #3 0x806153e in system.tasking.stages.activate_tasks ()
16790 #4 0x804aacc in un () at un.adb:5
16793 @item break @var{location} task @var{taskno}
16794 @itemx break @var{location} task @var{taskno} if @dots{}
16795 @cindex breakpoints and tasks, in Ada
16796 @cindex task breakpoints, in Ada
16797 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16798 These commands are like the @code{break @dots{} thread @dots{}}
16799 command (@pxref{Thread Stops}). The
16800 @var{location} argument specifies source lines, as described
16801 in @ref{Specify Location}.
16803 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16804 to specify that you only want @value{GDBN} to stop the program when a
16805 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16806 numeric task identifiers assigned by @value{GDBN}, shown in the first
16807 column of the @samp{info tasks} display.
16809 If you do not specify @samp{task @var{taskno}} when you set a
16810 breakpoint, the breakpoint applies to @emph{all} tasks of your
16813 You can use the @code{task} qualifier on conditional breakpoints as
16814 well; in this case, place @samp{task @var{taskno}} before the
16815 breakpoint condition (before the @code{if}).
16823 (@value{GDBP}) info tasks
16824 ID TID P-ID Pri State Name
16825 1 140022020 0 15 Child Activation Wait main_task
16826 2 140045060 1 15 Accept/Select Wait t2
16827 3 140044840 1 15 Runnable t1
16828 * 4 140056040 1 15 Runnable t3
16829 (@value{GDBP}) b 15 task 2
16830 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16831 (@value{GDBP}) cont
16836 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16838 (@value{GDBP}) info tasks
16839 ID TID P-ID Pri State Name
16840 1 140022020 0 15 Child Activation Wait main_task
16841 * 2 140045060 1 15 Runnable t2
16842 3 140044840 1 15 Runnable t1
16843 4 140056040 1 15 Delay Sleep t3
16847 @node Ada Tasks and Core Files
16848 @subsubsection Tasking Support when Debugging Core Files
16849 @cindex Ada tasking and core file debugging
16851 When inspecting a core file, as opposed to debugging a live program,
16852 tasking support may be limited or even unavailable, depending on
16853 the platform being used.
16854 For instance, on x86-linux, the list of tasks is available, but task
16855 switching is not supported.
16857 On certain platforms, the debugger needs to perform some
16858 memory writes in order to provide Ada tasking support. When inspecting
16859 a core file, this means that the core file must be opened with read-write
16860 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16861 Under these circumstances, you should make a backup copy of the core
16862 file before inspecting it with @value{GDBN}.
16864 @node Ravenscar Profile
16865 @subsubsection Tasking Support when using the Ravenscar Profile
16866 @cindex Ravenscar Profile
16868 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16869 specifically designed for systems with safety-critical real-time
16873 @kindex set ravenscar task-switching on
16874 @cindex task switching with program using Ravenscar Profile
16875 @item set ravenscar task-switching on
16876 Allows task switching when debugging a program that uses the Ravenscar
16877 Profile. This is the default.
16879 @kindex set ravenscar task-switching off
16880 @item set ravenscar task-switching off
16881 Turn off task switching when debugging a program that uses the Ravenscar
16882 Profile. This is mostly intended to disable the code that adds support
16883 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16884 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16885 To be effective, this command should be run before the program is started.
16887 @kindex show ravenscar task-switching
16888 @item show ravenscar task-switching
16889 Show whether it is possible to switch from task to task in a program
16890 using the Ravenscar Profile.
16895 @subsubsection Known Peculiarities of Ada Mode
16896 @cindex Ada, problems
16898 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16899 we know of several problems with and limitations of Ada mode in
16901 some of which will be fixed with planned future releases of the debugger
16902 and the GNU Ada compiler.
16906 Static constants that the compiler chooses not to materialize as objects in
16907 storage are invisible to the debugger.
16910 Named parameter associations in function argument lists are ignored (the
16911 argument lists are treated as positional).
16914 Many useful library packages are currently invisible to the debugger.
16917 Fixed-point arithmetic, conversions, input, and output is carried out using
16918 floating-point arithmetic, and may give results that only approximate those on
16922 The GNAT compiler never generates the prefix @code{Standard} for any of
16923 the standard symbols defined by the Ada language. @value{GDBN} knows about
16924 this: it will strip the prefix from names when you use it, and will never
16925 look for a name you have so qualified among local symbols, nor match against
16926 symbols in other packages or subprograms. If you have
16927 defined entities anywhere in your program other than parameters and
16928 local variables whose simple names match names in @code{Standard},
16929 GNAT's lack of qualification here can cause confusion. When this happens,
16930 you can usually resolve the confusion
16931 by qualifying the problematic names with package
16932 @code{Standard} explicitly.
16935 Older versions of the compiler sometimes generate erroneous debugging
16936 information, resulting in the debugger incorrectly printing the value
16937 of affected entities. In some cases, the debugger is able to work
16938 around an issue automatically. In other cases, the debugger is able
16939 to work around the issue, but the work-around has to be specifically
16942 @kindex set ada trust-PAD-over-XVS
16943 @kindex show ada trust-PAD-over-XVS
16946 @item set ada trust-PAD-over-XVS on
16947 Configure GDB to strictly follow the GNAT encoding when computing the
16948 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16949 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16950 a complete description of the encoding used by the GNAT compiler).
16951 This is the default.
16953 @item set ada trust-PAD-over-XVS off
16954 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16955 sometimes prints the wrong value for certain entities, changing @code{ada
16956 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16957 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16958 @code{off}, but this incurs a slight performance penalty, so it is
16959 recommended to leave this setting to @code{on} unless necessary.
16963 @cindex GNAT descriptive types
16964 @cindex GNAT encoding
16965 Internally, the debugger also relies on the compiler following a number
16966 of conventions known as the @samp{GNAT Encoding}, all documented in
16967 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16968 how the debugging information should be generated for certain types.
16969 In particular, this convention makes use of @dfn{descriptive types},
16970 which are artificial types generated purely to help the debugger.
16972 These encodings were defined at a time when the debugging information
16973 format used was not powerful enough to describe some of the more complex
16974 types available in Ada. Since DWARF allows us to express nearly all
16975 Ada features, the long-term goal is to slowly replace these descriptive
16976 types by their pure DWARF equivalent. To facilitate that transition,
16977 a new maintenance option is available to force the debugger to ignore
16978 those descriptive types. It allows the user to quickly evaluate how
16979 well @value{GDBN} works without them.
16983 @kindex maint ada set ignore-descriptive-types
16984 @item maintenance ada set ignore-descriptive-types [on|off]
16985 Control whether the debugger should ignore descriptive types.
16986 The default is not to ignore descriptives types (@code{off}).
16988 @kindex maint ada show ignore-descriptive-types
16989 @item maintenance ada show ignore-descriptive-types
16990 Show if descriptive types are ignored by @value{GDBN}.
16994 @node Unsupported Languages
16995 @section Unsupported Languages
16997 @cindex unsupported languages
16998 @cindex minimal language
16999 In addition to the other fully-supported programming languages,
17000 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17001 It does not represent a real programming language, but provides a set
17002 of capabilities close to what the C or assembly languages provide.
17003 This should allow most simple operations to be performed while debugging
17004 an application that uses a language currently not supported by @value{GDBN}.
17006 If the language is set to @code{auto}, @value{GDBN} will automatically
17007 select this language if the current frame corresponds to an unsupported
17011 @chapter Examining the Symbol Table
17013 The commands described in this chapter allow you to inquire about the
17014 symbols (names of variables, functions and types) defined in your
17015 program. This information is inherent in the text of your program and
17016 does not change as your program executes. @value{GDBN} finds it in your
17017 program's symbol table, in the file indicated when you started @value{GDBN}
17018 (@pxref{File Options, ,Choosing Files}), or by one of the
17019 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17021 @cindex symbol names
17022 @cindex names of symbols
17023 @cindex quoting names
17024 @anchor{quoting names}
17025 Occasionally, you may need to refer to symbols that contain unusual
17026 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17027 most frequent case is in referring to static variables in other
17028 source files (@pxref{Variables,,Program Variables}). File names
17029 are recorded in object files as debugging symbols, but @value{GDBN} would
17030 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17031 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17032 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17039 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17042 @cindex case-insensitive symbol names
17043 @cindex case sensitivity in symbol names
17044 @kindex set case-sensitive
17045 @item set case-sensitive on
17046 @itemx set case-sensitive off
17047 @itemx set case-sensitive auto
17048 Normally, when @value{GDBN} looks up symbols, it matches their names
17049 with case sensitivity determined by the current source language.
17050 Occasionally, you may wish to control that. The command @code{set
17051 case-sensitive} lets you do that by specifying @code{on} for
17052 case-sensitive matches or @code{off} for case-insensitive ones. If
17053 you specify @code{auto}, case sensitivity is reset to the default
17054 suitable for the source language. The default is case-sensitive
17055 matches for all languages except for Fortran, for which the default is
17056 case-insensitive matches.
17058 @kindex show case-sensitive
17059 @item show case-sensitive
17060 This command shows the current setting of case sensitivity for symbols
17063 @kindex set print type methods
17064 @item set print type methods
17065 @itemx set print type methods on
17066 @itemx set print type methods off
17067 Normally, when @value{GDBN} prints a class, it displays any methods
17068 declared in that class. You can control this behavior either by
17069 passing the appropriate flag to @code{ptype}, or using @command{set
17070 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17071 display the methods; this is the default. Specifying @code{off} will
17072 cause @value{GDBN} to omit the methods.
17074 @kindex show print type methods
17075 @item show print type methods
17076 This command shows the current setting of method display when printing
17079 @kindex set print type nested-type-limit
17080 @item set print type nested-type-limit @var{limit}
17081 @itemx set print type nested-type-limit unlimited
17082 Set the limit of displayed nested types that the type printer will
17083 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17084 nested definitions. By default, the type printer will not show any nested
17085 types defined in classes.
17087 @kindex show print type nested-type-limit
17088 @item show print type nested-type-limit
17089 This command shows the current display limit of nested types when
17092 @kindex set print type typedefs
17093 @item set print type typedefs
17094 @itemx set print type typedefs on
17095 @itemx set print type typedefs off
17097 Normally, when @value{GDBN} prints a class, it displays any typedefs
17098 defined in that class. You can control this behavior either by
17099 passing the appropriate flag to @code{ptype}, or using @command{set
17100 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17101 display the typedef definitions; this is the default. Specifying
17102 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17103 Note that this controls whether the typedef definition itself is
17104 printed, not whether typedef names are substituted when printing other
17107 @kindex show print type typedefs
17108 @item show print type typedefs
17109 This command shows the current setting of typedef display when
17112 @kindex info address
17113 @cindex address of a symbol
17114 @item info address @var{symbol}
17115 Describe where the data for @var{symbol} is stored. For a register
17116 variable, this says which register it is kept in. For a non-register
17117 local variable, this prints the stack-frame offset at which the variable
17120 Note the contrast with @samp{print &@var{symbol}}, which does not work
17121 at all for a register variable, and for a stack local variable prints
17122 the exact address of the current instantiation of the variable.
17124 @kindex info symbol
17125 @cindex symbol from address
17126 @cindex closest symbol and offset for an address
17127 @item info symbol @var{addr}
17128 Print the name of a symbol which is stored at the address @var{addr}.
17129 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17130 nearest symbol and an offset from it:
17133 (@value{GDBP}) info symbol 0x54320
17134 _initialize_vx + 396 in section .text
17138 This is the opposite of the @code{info address} command. You can use
17139 it to find out the name of a variable or a function given its address.
17141 For dynamically linked executables, the name of executable or shared
17142 library containing the symbol is also printed:
17145 (@value{GDBP}) info symbol 0x400225
17146 _start + 5 in section .text of /tmp/a.out
17147 (@value{GDBP}) info symbol 0x2aaaac2811cf
17148 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17153 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17154 Demangle @var{name}.
17155 If @var{language} is provided it is the name of the language to demangle
17156 @var{name} in. Otherwise @var{name} is demangled in the current language.
17158 The @samp{--} option specifies the end of options,
17159 and is useful when @var{name} begins with a dash.
17161 The parameter @code{demangle-style} specifies how to interpret the kind
17162 of mangling used. @xref{Print Settings}.
17165 @item whatis[/@var{flags}] [@var{arg}]
17166 Print the data type of @var{arg}, which can be either an expression
17167 or a name of a data type. With no argument, print the data type of
17168 @code{$}, the last value in the value history.
17170 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17171 is not actually evaluated, and any side-effecting operations (such as
17172 assignments or function calls) inside it do not take place.
17174 If @var{arg} is a variable or an expression, @code{whatis} prints its
17175 literal type as it is used in the source code. If the type was
17176 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17177 the data type underlying the @code{typedef}. If the type of the
17178 variable or the expression is a compound data type, such as
17179 @code{struct} or @code{class}, @code{whatis} never prints their
17180 fields or methods. It just prints the @code{struct}/@code{class}
17181 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17182 such a compound data type, use @code{ptype}.
17184 If @var{arg} is a type name that was defined using @code{typedef},
17185 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17186 Unrolling means that @code{whatis} will show the underlying type used
17187 in the @code{typedef} declaration of @var{arg}. However, if that
17188 underlying type is also a @code{typedef}, @code{whatis} will not
17191 For C code, the type names may also have the form @samp{class
17192 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17193 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17195 @var{flags} can be used to modify how the type is displayed.
17196 Available flags are:
17200 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17201 parameters and typedefs defined in a class when printing the class'
17202 members. The @code{/r} flag disables this.
17205 Do not print methods defined in the class.
17208 Print methods defined in the class. This is the default, but the flag
17209 exists in case you change the default with @command{set print type methods}.
17212 Do not print typedefs defined in the class. Note that this controls
17213 whether the typedef definition itself is printed, not whether typedef
17214 names are substituted when printing other types.
17217 Print typedefs defined in the class. This is the default, but the flag
17218 exists in case you change the default with @command{set print type typedefs}.
17221 Print the offsets and sizes of fields in a struct, similar to what the
17222 @command{pahole} tool does. This option implies the @code{/tm} flags.
17224 For example, given the following declarations:
17260 Issuing a @kbd{ptype /o struct tuv} command would print:
17263 (@value{GDBP}) ptype /o struct tuv
17264 /* offset | size */ type = struct tuv @{
17265 /* 0 | 4 */ int a1;
17266 /* XXX 4-byte hole */
17267 /* 8 | 8 */ char *a2;
17268 /* 16 | 4 */ int a3;
17270 /* total size (bytes): 24 */
17274 Notice the format of the first column of comments. There, you can
17275 find two parts separated by the @samp{|} character: the @emph{offset},
17276 which indicates where the field is located inside the struct, in
17277 bytes, and the @emph{size} of the field. Another interesting line is
17278 the marker of a @emph{hole} in the struct, indicating that it may be
17279 possible to pack the struct and make it use less space by reorganizing
17282 It is also possible to print offsets inside an union:
17285 (@value{GDBP}) ptype /o union qwe
17286 /* offset | size */ type = union qwe @{
17287 /* 24 */ struct tuv @{
17288 /* 0 | 4 */ int a1;
17289 /* XXX 4-byte hole */
17290 /* 8 | 8 */ char *a2;
17291 /* 16 | 4 */ int a3;
17293 /* total size (bytes): 24 */
17295 /* 40 */ struct xyz @{
17296 /* 0 | 4 */ int f1;
17297 /* 4 | 1 */ char f2;
17298 /* XXX 3-byte hole */
17299 /* 8 | 8 */ void *f3;
17300 /* 16 | 24 */ struct tuv @{
17301 /* 16 | 4 */ int a1;
17302 /* XXX 4-byte hole */
17303 /* 24 | 8 */ char *a2;
17304 /* 32 | 4 */ int a3;
17306 /* total size (bytes): 24 */
17309 /* total size (bytes): 40 */
17312 /* total size (bytes): 40 */
17316 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17317 same space (because we are dealing with an union), the offset is not
17318 printed for them. However, you can still examine the offset of each
17319 of these structures' fields.
17321 Another useful scenario is printing the offsets of a struct containing
17325 (@value{GDBP}) ptype /o struct tyu
17326 /* offset | size */ type = struct tyu @{
17327 /* 0:31 | 4 */ int a1 : 1;
17328 /* 0:28 | 4 */ int a2 : 3;
17329 /* 0: 5 | 4 */ int a3 : 23;
17330 /* 3: 3 | 1 */ signed char a4 : 2;
17331 /* XXX 3-bit hole */
17332 /* XXX 4-byte hole */
17333 /* 8 | 8 */ int64_t a5;
17334 /* 16:27 | 4 */ int a6 : 5;
17335 /* 16:56 | 8 */ int64_t a7 : 3;
17337 /* total size (bytes): 24 */
17341 Note how the offset information is now extended to also include how
17342 many bits are left to be used in each bitfield.
17346 @item ptype[/@var{flags}] [@var{arg}]
17347 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17348 detailed description of the type, instead of just the name of the type.
17349 @xref{Expressions, ,Expressions}.
17351 Contrary to @code{whatis}, @code{ptype} always unrolls any
17352 @code{typedef}s in its argument declaration, whether the argument is
17353 a variable, expression, or a data type. This means that @code{ptype}
17354 of a variable or an expression will not print literally its type as
17355 present in the source code---use @code{whatis} for that. @code{typedef}s at
17356 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17357 fields, methods and inner @code{class typedef}s of @code{struct}s,
17358 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17360 For example, for this variable declaration:
17363 typedef double real_t;
17364 struct complex @{ real_t real; double imag; @};
17365 typedef struct complex complex_t;
17367 real_t *real_pointer_var;
17371 the two commands give this output:
17375 (@value{GDBP}) whatis var
17377 (@value{GDBP}) ptype var
17378 type = struct complex @{
17382 (@value{GDBP}) whatis complex_t
17383 type = struct complex
17384 (@value{GDBP}) whatis struct complex
17385 type = struct complex
17386 (@value{GDBP}) ptype struct complex
17387 type = struct complex @{
17391 (@value{GDBP}) whatis real_pointer_var
17393 (@value{GDBP}) ptype real_pointer_var
17399 As with @code{whatis}, using @code{ptype} without an argument refers to
17400 the type of @code{$}, the last value in the value history.
17402 @cindex incomplete type
17403 Sometimes, programs use opaque data types or incomplete specifications
17404 of complex data structure. If the debug information included in the
17405 program does not allow @value{GDBN} to display a full declaration of
17406 the data type, it will say @samp{<incomplete type>}. For example,
17407 given these declarations:
17411 struct foo *fooptr;
17415 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17418 (@value{GDBP}) ptype foo
17419 $1 = <incomplete type>
17423 ``Incomplete type'' is C terminology for data types that are not
17424 completely specified.
17426 @cindex unknown type
17427 Othertimes, information about a variable's type is completely absent
17428 from the debug information included in the program. This most often
17429 happens when the program or library where the variable is defined
17430 includes no debug information at all. @value{GDBN} knows the variable
17431 exists from inspecting the linker/loader symbol table (e.g., the ELF
17432 dynamic symbol table), but such symbols do not contain type
17433 information. Inspecting the type of a (global) variable for which
17434 @value{GDBN} has no type information shows:
17437 (@value{GDBP}) ptype var
17438 type = <data variable, no debug info>
17441 @xref{Variables, no debug info variables}, for how to print the values
17445 @item info types @var{regexp}
17447 Print a brief description of all types whose names match the regular
17448 expression @var{regexp} (or all types in your program, if you supply
17449 no argument). Each complete typename is matched as though it were a
17450 complete line; thus, @samp{i type value} gives information on all
17451 types in your program whose names include the string @code{value}, but
17452 @samp{i type ^value$} gives information only on types whose complete
17453 name is @code{value}.
17455 This command differs from @code{ptype} in two ways: first, like
17456 @code{whatis}, it does not print a detailed description; second, it
17457 lists all source files where a type is defined.
17459 @kindex info type-printers
17460 @item info type-printers
17461 Versions of @value{GDBN} that ship with Python scripting enabled may
17462 have ``type printers'' available. When using @command{ptype} or
17463 @command{whatis}, these printers are consulted when the name of a type
17464 is needed. @xref{Type Printing API}, for more information on writing
17467 @code{info type-printers} displays all the available type printers.
17469 @kindex enable type-printer
17470 @kindex disable type-printer
17471 @item enable type-printer @var{name}@dots{}
17472 @item disable type-printer @var{name}@dots{}
17473 These commands can be used to enable or disable type printers.
17476 @cindex local variables
17477 @item info scope @var{location}
17478 List all the variables local to a particular scope. This command
17479 accepts a @var{location} argument---a function name, a source line, or
17480 an address preceded by a @samp{*}, and prints all the variables local
17481 to the scope defined by that location. (@xref{Specify Location}, for
17482 details about supported forms of @var{location}.) For example:
17485 (@value{GDBP}) @b{info scope command_line_handler}
17486 Scope for command_line_handler:
17487 Symbol rl is an argument at stack/frame offset 8, length 4.
17488 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17489 Symbol linelength is in static storage at address 0x150a1c, length 4.
17490 Symbol p is a local variable in register $esi, length 4.
17491 Symbol p1 is a local variable in register $ebx, length 4.
17492 Symbol nline is a local variable in register $edx, length 4.
17493 Symbol repeat is a local variable at frame offset -8, length 4.
17497 This command is especially useful for determining what data to collect
17498 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17501 @kindex info source
17503 Show information about the current source file---that is, the source file for
17504 the function containing the current point of execution:
17507 the name of the source file, and the directory containing it,
17509 the directory it was compiled in,
17511 its length, in lines,
17513 which programming language it is written in,
17515 if the debug information provides it, the program that compiled the file
17516 (which may include, e.g., the compiler version and command line arguments),
17518 whether the executable includes debugging information for that file, and
17519 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17521 whether the debugging information includes information about
17522 preprocessor macros.
17526 @kindex info sources
17528 Print the names of all source files in your program for which there is
17529 debugging information, organized into two lists: files whose symbols
17530 have already been read, and files whose symbols will be read when needed.
17532 @kindex info functions
17533 @item info functions
17534 Print the names and data types of all defined functions.
17536 @item info functions @var{regexp}
17537 Print the names and data types of all defined functions
17538 whose names contain a match for regular expression @var{regexp}.
17539 Thus, @samp{info fun step} finds all functions whose names
17540 include @code{step}; @samp{info fun ^step} finds those whose names
17541 start with @code{step}. If a function name contains characters
17542 that conflict with the regular expression language (e.g.@:
17543 @samp{operator*()}), they may be quoted with a backslash.
17545 @kindex info variables
17546 @item info variables
17547 Print the names and data types of all variables that are defined
17548 outside of functions (i.e.@: excluding local variables).
17550 @item info variables @var{regexp}
17551 Print the names and data types of all variables (except for local
17552 variables) whose names contain a match for regular expression
17555 @kindex info classes
17556 @cindex Objective-C, classes and selectors
17558 @itemx info classes @var{regexp}
17559 Display all Objective-C classes in your program, or
17560 (with the @var{regexp} argument) all those matching a particular regular
17563 @kindex info selectors
17564 @item info selectors
17565 @itemx info selectors @var{regexp}
17566 Display all Objective-C selectors in your program, or
17567 (with the @var{regexp} argument) all those matching a particular regular
17571 This was never implemented.
17572 @kindex info methods
17574 @itemx info methods @var{regexp}
17575 The @code{info methods} command permits the user to examine all defined
17576 methods within C@t{++} program, or (with the @var{regexp} argument) a
17577 specific set of methods found in the various C@t{++} classes. Many
17578 C@t{++} classes provide a large number of methods. Thus, the output
17579 from the @code{ptype} command can be overwhelming and hard to use. The
17580 @code{info-methods} command filters the methods, printing only those
17581 which match the regular-expression @var{regexp}.
17584 @cindex opaque data types
17585 @kindex set opaque-type-resolution
17586 @item set opaque-type-resolution on
17587 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17588 declared as a pointer to a @code{struct}, @code{class}, or
17589 @code{union}---for example, @code{struct MyType *}---that is used in one
17590 source file although the full declaration of @code{struct MyType} is in
17591 another source file. The default is on.
17593 A change in the setting of this subcommand will not take effect until
17594 the next time symbols for a file are loaded.
17596 @item set opaque-type-resolution off
17597 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17598 is printed as follows:
17600 @{<no data fields>@}
17603 @kindex show opaque-type-resolution
17604 @item show opaque-type-resolution
17605 Show whether opaque types are resolved or not.
17607 @kindex set print symbol-loading
17608 @cindex print messages when symbols are loaded
17609 @item set print symbol-loading
17610 @itemx set print symbol-loading full
17611 @itemx set print symbol-loading brief
17612 @itemx set print symbol-loading off
17613 The @code{set print symbol-loading} command allows you to control the
17614 printing of messages when @value{GDBN} loads symbol information.
17615 By default a message is printed for the executable and one for each
17616 shared library, and normally this is what you want. However, when
17617 debugging apps with large numbers of shared libraries these messages
17619 When set to @code{brief} a message is printed for each executable,
17620 and when @value{GDBN} loads a collection of shared libraries at once
17621 it will only print one message regardless of the number of shared
17622 libraries. When set to @code{off} no messages are printed.
17624 @kindex show print symbol-loading
17625 @item show print symbol-loading
17626 Show whether messages will be printed when a @value{GDBN} command
17627 entered from the keyboard causes symbol information to be loaded.
17629 @kindex maint print symbols
17630 @cindex symbol dump
17631 @kindex maint print psymbols
17632 @cindex partial symbol dump
17633 @kindex maint print msymbols
17634 @cindex minimal symbol dump
17635 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17636 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17637 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17638 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17639 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17640 Write a dump of debugging symbol data into the file @var{filename} or
17641 the terminal if @var{filename} is unspecified.
17642 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17644 If @code{-pc @var{address}} is specified, only dump symbols for the file
17645 with code at that address. Note that @var{address} may be a symbol like
17647 If @code{-source @var{source}} is specified, only dump symbols for that
17650 These commands are used to debug the @value{GDBN} symbol-reading code.
17651 These commands do not modify internal @value{GDBN} state, therefore
17652 @samp{maint print symbols} will only print symbols for already expanded symbol
17654 You can use the command @code{info sources} to find out which files these are.
17655 If you use @samp{maint print psymbols} instead, the dump shows information
17656 about symbols that @value{GDBN} only knows partially---that is, symbols
17657 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17658 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17661 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17662 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17664 @kindex maint info symtabs
17665 @kindex maint info psymtabs
17666 @cindex listing @value{GDBN}'s internal symbol tables
17667 @cindex symbol tables, listing @value{GDBN}'s internal
17668 @cindex full symbol tables, listing @value{GDBN}'s internal
17669 @cindex partial symbol tables, listing @value{GDBN}'s internal
17670 @item maint info symtabs @r{[} @var{regexp} @r{]}
17671 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17673 List the @code{struct symtab} or @code{struct partial_symtab}
17674 structures whose names match @var{regexp}. If @var{regexp} is not
17675 given, list them all. The output includes expressions which you can
17676 copy into a @value{GDBN} debugging this one to examine a particular
17677 structure in more detail. For example:
17680 (@value{GDBP}) maint info psymtabs dwarf2read
17681 @{ objfile /home/gnu/build/gdb/gdb
17682 ((struct objfile *) 0x82e69d0)
17683 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17684 ((struct partial_symtab *) 0x8474b10)
17687 text addresses 0x814d3c8 -- 0x8158074
17688 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17689 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17690 dependencies (none)
17693 (@value{GDBP}) maint info symtabs
17697 We see that there is one partial symbol table whose filename contains
17698 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17699 and we see that @value{GDBN} has not read in any symtabs yet at all.
17700 If we set a breakpoint on a function, that will cause @value{GDBN} to
17701 read the symtab for the compilation unit containing that function:
17704 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17705 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17707 (@value{GDBP}) maint info symtabs
17708 @{ objfile /home/gnu/build/gdb/gdb
17709 ((struct objfile *) 0x82e69d0)
17710 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17711 ((struct symtab *) 0x86c1f38)
17714 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17715 linetable ((struct linetable *) 0x8370fa0)
17716 debugformat DWARF 2
17722 @kindex maint info line-table
17723 @cindex listing @value{GDBN}'s internal line tables
17724 @cindex line tables, listing @value{GDBN}'s internal
17725 @item maint info line-table @r{[} @var{regexp} @r{]}
17727 List the @code{struct linetable} from all @code{struct symtab}
17728 instances whose name matches @var{regexp}. If @var{regexp} is not
17729 given, list the @code{struct linetable} from all @code{struct symtab}.
17731 @kindex maint set symbol-cache-size
17732 @cindex symbol cache size
17733 @item maint set symbol-cache-size @var{size}
17734 Set the size of the symbol cache to @var{size}.
17735 The default size is intended to be good enough for debugging
17736 most applications. This option exists to allow for experimenting
17737 with different sizes.
17739 @kindex maint show symbol-cache-size
17740 @item maint show symbol-cache-size
17741 Show the size of the symbol cache.
17743 @kindex maint print symbol-cache
17744 @cindex symbol cache, printing its contents
17745 @item maint print symbol-cache
17746 Print the contents of the symbol cache.
17747 This is useful when debugging symbol cache issues.
17749 @kindex maint print symbol-cache-statistics
17750 @cindex symbol cache, printing usage statistics
17751 @item maint print symbol-cache-statistics
17752 Print symbol cache usage statistics.
17753 This helps determine how well the cache is being utilized.
17755 @kindex maint flush-symbol-cache
17756 @cindex symbol cache, flushing
17757 @item maint flush-symbol-cache
17758 Flush the contents of the symbol cache, all entries are removed.
17759 This command is useful when debugging the symbol cache.
17760 It is also useful when collecting performance data.
17765 @chapter Altering Execution
17767 Once you think you have found an error in your program, you might want to
17768 find out for certain whether correcting the apparent error would lead to
17769 correct results in the rest of the run. You can find the answer by
17770 experiment, using the @value{GDBN} features for altering execution of the
17773 For example, you can store new values into variables or memory
17774 locations, give your program a signal, restart it at a different
17775 address, or even return prematurely from a function.
17778 * Assignment:: Assignment to variables
17779 * Jumping:: Continuing at a different address
17780 * Signaling:: Giving your program a signal
17781 * Returning:: Returning from a function
17782 * Calling:: Calling your program's functions
17783 * Patching:: Patching your program
17784 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17788 @section Assignment to Variables
17791 @cindex setting variables
17792 To alter the value of a variable, evaluate an assignment expression.
17793 @xref{Expressions, ,Expressions}. For example,
17800 stores the value 4 into the variable @code{x}, and then prints the
17801 value of the assignment expression (which is 4).
17802 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17803 information on operators in supported languages.
17805 @kindex set variable
17806 @cindex variables, setting
17807 If you are not interested in seeing the value of the assignment, use the
17808 @code{set} command instead of the @code{print} command. @code{set} is
17809 really the same as @code{print} except that the expression's value is
17810 not printed and is not put in the value history (@pxref{Value History,
17811 ,Value History}). The expression is evaluated only for its effects.
17813 If the beginning of the argument string of the @code{set} command
17814 appears identical to a @code{set} subcommand, use the @code{set
17815 variable} command instead of just @code{set}. This command is identical
17816 to @code{set} except for its lack of subcommands. For example, if your
17817 program has a variable @code{width}, you get an error if you try to set
17818 a new value with just @samp{set width=13}, because @value{GDBN} has the
17819 command @code{set width}:
17822 (@value{GDBP}) whatis width
17824 (@value{GDBP}) p width
17826 (@value{GDBP}) set width=47
17827 Invalid syntax in expression.
17831 The invalid expression, of course, is @samp{=47}. In
17832 order to actually set the program's variable @code{width}, use
17835 (@value{GDBP}) set var width=47
17838 Because the @code{set} command has many subcommands that can conflict
17839 with the names of program variables, it is a good idea to use the
17840 @code{set variable} command instead of just @code{set}. For example, if
17841 your program has a variable @code{g}, you run into problems if you try
17842 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17843 the command @code{set gnutarget}, abbreviated @code{set g}:
17847 (@value{GDBP}) whatis g
17851 (@value{GDBP}) set g=4
17855 The program being debugged has been started already.
17856 Start it from the beginning? (y or n) y
17857 Starting program: /home/smith/cc_progs/a.out
17858 "/home/smith/cc_progs/a.out": can't open to read symbols:
17859 Invalid bfd target.
17860 (@value{GDBP}) show g
17861 The current BFD target is "=4".
17866 The program variable @code{g} did not change, and you silently set the
17867 @code{gnutarget} to an invalid value. In order to set the variable
17871 (@value{GDBP}) set var g=4
17874 @value{GDBN} allows more implicit conversions in assignments than C; you can
17875 freely store an integer value into a pointer variable or vice versa,
17876 and you can convert any structure to any other structure that is the
17877 same length or shorter.
17878 @comment FIXME: how do structs align/pad in these conversions?
17879 @comment /doc@cygnus.com 18dec1990
17881 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17882 construct to generate a value of specified type at a specified address
17883 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17884 to memory location @code{0x83040} as an integer (which implies a certain size
17885 and representation in memory), and
17888 set @{int@}0x83040 = 4
17892 stores the value 4 into that memory location.
17895 @section Continuing at a Different Address
17897 Ordinarily, when you continue your program, you do so at the place where
17898 it stopped, with the @code{continue} command. You can instead continue at
17899 an address of your own choosing, with the following commands:
17903 @kindex j @r{(@code{jump})}
17904 @item jump @var{location}
17905 @itemx j @var{location}
17906 Resume execution at @var{location}. Execution stops again immediately
17907 if there is a breakpoint there. @xref{Specify Location}, for a description
17908 of the different forms of @var{location}. It is common
17909 practice to use the @code{tbreak} command in conjunction with
17910 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17912 The @code{jump} command does not change the current stack frame, or
17913 the stack pointer, or the contents of any memory location or any
17914 register other than the program counter. If @var{location} is in
17915 a different function from the one currently executing, the results may
17916 be bizarre if the two functions expect different patterns of arguments or
17917 of local variables. For this reason, the @code{jump} command requests
17918 confirmation if the specified line is not in the function currently
17919 executing. However, even bizarre results are predictable if you are
17920 well acquainted with the machine-language code of your program.
17923 On many systems, you can get much the same effect as the @code{jump}
17924 command by storing a new value into the register @code{$pc}. The
17925 difference is that this does not start your program running; it only
17926 changes the address of where it @emph{will} run when you continue. For
17934 makes the next @code{continue} command or stepping command execute at
17935 address @code{0x485}, rather than at the address where your program stopped.
17936 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17938 The most common occasion to use the @code{jump} command is to back
17939 up---perhaps with more breakpoints set---over a portion of a program
17940 that has already executed, in order to examine its execution in more
17945 @section Giving your Program a Signal
17946 @cindex deliver a signal to a program
17950 @item signal @var{signal}
17951 Resume execution where your program is stopped, but immediately give it the
17952 signal @var{signal}. The @var{signal} can be the name or the number of a
17953 signal. For example, on many systems @code{signal 2} and @code{signal
17954 SIGINT} are both ways of sending an interrupt signal.
17956 Alternatively, if @var{signal} is zero, continue execution without
17957 giving a signal. This is useful when your program stopped on account of
17958 a signal and would ordinarily see the signal when resumed with the
17959 @code{continue} command; @samp{signal 0} causes it to resume without a
17962 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17963 delivered to the currently selected thread, not the thread that last
17964 reported a stop. This includes the situation where a thread was
17965 stopped due to a signal. So if you want to continue execution
17966 suppressing the signal that stopped a thread, you should select that
17967 same thread before issuing the @samp{signal 0} command. If you issue
17968 the @samp{signal 0} command with another thread as the selected one,
17969 @value{GDBN} detects that and asks for confirmation.
17971 Invoking the @code{signal} command is not the same as invoking the
17972 @code{kill} utility from the shell. Sending a signal with @code{kill}
17973 causes @value{GDBN} to decide what to do with the signal depending on
17974 the signal handling tables (@pxref{Signals}). The @code{signal} command
17975 passes the signal directly to your program.
17977 @code{signal} does not repeat when you press @key{RET} a second time
17978 after executing the command.
17980 @kindex queue-signal
17981 @item queue-signal @var{signal}
17982 Queue @var{signal} to be delivered immediately to the current thread
17983 when execution of the thread resumes. The @var{signal} can be the name or
17984 the number of a signal. For example, on many systems @code{signal 2} and
17985 @code{signal SIGINT} are both ways of sending an interrupt signal.
17986 The handling of the signal must be set to pass the signal to the program,
17987 otherwise @value{GDBN} will report an error.
17988 You can control the handling of signals from @value{GDBN} with the
17989 @code{handle} command (@pxref{Signals}).
17991 Alternatively, if @var{signal} is zero, any currently queued signal
17992 for the current thread is discarded and when execution resumes no signal
17993 will be delivered. This is useful when your program stopped on account
17994 of a signal and would ordinarily see the signal when resumed with the
17995 @code{continue} command.
17997 This command differs from the @code{signal} command in that the signal
17998 is just queued, execution is not resumed. And @code{queue-signal} cannot
17999 be used to pass a signal whose handling state has been set to @code{nopass}
18004 @xref{stepping into signal handlers}, for information on how stepping
18005 commands behave when the thread has a signal queued.
18008 @section Returning from a Function
18011 @cindex returning from a function
18014 @itemx return @var{expression}
18015 You can cancel execution of a function call with the @code{return}
18016 command. If you give an
18017 @var{expression} argument, its value is used as the function's return
18021 When you use @code{return}, @value{GDBN} discards the selected stack frame
18022 (and all frames within it). You can think of this as making the
18023 discarded frame return prematurely. If you wish to specify a value to
18024 be returned, give that value as the argument to @code{return}.
18026 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18027 Frame}), and any other frames inside of it, leaving its caller as the
18028 innermost remaining frame. That frame becomes selected. The
18029 specified value is stored in the registers used for returning values
18032 The @code{return} command does not resume execution; it leaves the
18033 program stopped in the state that would exist if the function had just
18034 returned. In contrast, the @code{finish} command (@pxref{Continuing
18035 and Stepping, ,Continuing and Stepping}) resumes execution until the
18036 selected stack frame returns naturally.
18038 @value{GDBN} needs to know how the @var{expression} argument should be set for
18039 the inferior. The concrete registers assignment depends on the OS ABI and the
18040 type being returned by the selected stack frame. For example it is common for
18041 OS ABI to return floating point values in FPU registers while integer values in
18042 CPU registers. Still some ABIs return even floating point values in CPU
18043 registers. Larger integer widths (such as @code{long long int}) also have
18044 specific placement rules. @value{GDBN} already knows the OS ABI from its
18045 current target so it needs to find out also the type being returned to make the
18046 assignment into the right register(s).
18048 Normally, the selected stack frame has debug info. @value{GDBN} will always
18049 use the debug info instead of the implicit type of @var{expression} when the
18050 debug info is available. For example, if you type @kbd{return -1}, and the
18051 function in the current stack frame is declared to return a @code{long long
18052 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18053 into a @code{long long int}:
18056 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18058 (@value{GDBP}) return -1
18059 Make func return now? (y or n) y
18060 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18061 43 printf ("result=%lld\n", func ());
18065 However, if the selected stack frame does not have a debug info, e.g., if the
18066 function was compiled without debug info, @value{GDBN} has to find out the type
18067 to return from user. Specifying a different type by mistake may set the value
18068 in different inferior registers than the caller code expects. For example,
18069 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18070 of a @code{long long int} result for a debug info less function (on 32-bit
18071 architectures). Therefore the user is required to specify the return type by
18072 an appropriate cast explicitly:
18075 Breakpoint 2, 0x0040050b in func ()
18076 (@value{GDBP}) return -1
18077 Return value type not available for selected stack frame.
18078 Please use an explicit cast of the value to return.
18079 (@value{GDBP}) return (long long int) -1
18080 Make selected stack frame return now? (y or n) y
18081 #0 0x00400526 in main ()
18086 @section Calling Program Functions
18089 @cindex calling functions
18090 @cindex inferior functions, calling
18091 @item print @var{expr}
18092 Evaluate the expression @var{expr} and display the resulting value.
18093 The expression may include calls to functions in the program being
18097 @item call @var{expr}
18098 Evaluate the expression @var{expr} without displaying @code{void}
18101 You can use this variant of the @code{print} command if you want to
18102 execute a function from your program that does not return anything
18103 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18104 with @code{void} returned values that @value{GDBN} will otherwise
18105 print. If the result is not void, it is printed and saved in the
18109 It is possible for the function you call via the @code{print} or
18110 @code{call} command to generate a signal (e.g., if there's a bug in
18111 the function, or if you passed it incorrect arguments). What happens
18112 in that case is controlled by the @code{set unwindonsignal} command.
18114 Similarly, with a C@t{++} program it is possible for the function you
18115 call via the @code{print} or @code{call} command to generate an
18116 exception that is not handled due to the constraints of the dummy
18117 frame. In this case, any exception that is raised in the frame, but has
18118 an out-of-frame exception handler will not be found. GDB builds a
18119 dummy-frame for the inferior function call, and the unwinder cannot
18120 seek for exception handlers outside of this dummy-frame. What happens
18121 in that case is controlled by the
18122 @code{set unwind-on-terminating-exception} command.
18125 @item set unwindonsignal
18126 @kindex set unwindonsignal
18127 @cindex unwind stack in called functions
18128 @cindex call dummy stack unwinding
18129 Set unwinding of the stack if a signal is received while in a function
18130 that @value{GDBN} called in the program being debugged. If set to on,
18131 @value{GDBN} unwinds the stack it created for the call and restores
18132 the context to what it was before the call. If set to off (the
18133 default), @value{GDBN} stops in the frame where the signal was
18136 @item show unwindonsignal
18137 @kindex show unwindonsignal
18138 Show the current setting of stack unwinding in the functions called by
18141 @item set unwind-on-terminating-exception
18142 @kindex set unwind-on-terminating-exception
18143 @cindex unwind stack in called functions with unhandled exceptions
18144 @cindex call dummy stack unwinding on unhandled exception.
18145 Set unwinding of the stack if a C@t{++} exception is raised, but left
18146 unhandled while in a function that @value{GDBN} called in the program being
18147 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18148 it created for the call and restores the context to what it was before
18149 the call. If set to off, @value{GDBN} the exception is delivered to
18150 the default C@t{++} exception handler and the inferior terminated.
18152 @item show unwind-on-terminating-exception
18153 @kindex show unwind-on-terminating-exception
18154 Show the current setting of stack unwinding in the functions called by
18159 @subsection Calling functions with no debug info
18161 @cindex no debug info functions
18162 Sometimes, a function you wish to call is missing debug information.
18163 In such case, @value{GDBN} does not know the type of the function,
18164 including the types of the function's parameters. To avoid calling
18165 the inferior function incorrectly, which could result in the called
18166 function functioning erroneously and even crash, @value{GDBN} refuses
18167 to call the function unless you tell it the type of the function.
18169 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18170 to do that. The simplest is to cast the call to the function's
18171 declared return type. For example:
18174 (@value{GDBP}) p getenv ("PATH")
18175 'getenv' has unknown return type; cast the call to its declared return type
18176 (@value{GDBP}) p (char *) getenv ("PATH")
18177 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18180 Casting the return type of a no-debug function is equivalent to
18181 casting the function to a pointer to a prototyped function that has a
18182 prototype that matches the types of the passed-in arguments, and
18183 calling that. I.e., the call above is equivalent to:
18186 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18190 and given this prototyped C or C++ function with float parameters:
18193 float multiply (float v1, float v2) @{ return v1 * v2; @}
18197 these calls are equivalent:
18200 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18201 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18204 If the function you wish to call is declared as unprototyped (i.e.@:
18205 old K&R style), you must use the cast-to-function-pointer syntax, so
18206 that @value{GDBN} knows that it needs to apply default argument
18207 promotions (promote float arguments to double). @xref{ABI, float
18208 promotion}. For example, given this unprototyped C function with
18209 float parameters, and no debug info:
18213 multiply_noproto (v1, v2)
18221 you call it like this:
18224 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18228 @section Patching Programs
18230 @cindex patching binaries
18231 @cindex writing into executables
18232 @cindex writing into corefiles
18234 By default, @value{GDBN} opens the file containing your program's
18235 executable code (or the corefile) read-only. This prevents accidental
18236 alterations to machine code; but it also prevents you from intentionally
18237 patching your program's binary.
18239 If you'd like to be able to patch the binary, you can specify that
18240 explicitly with the @code{set write} command. For example, you might
18241 want to turn on internal debugging flags, or even to make emergency
18247 @itemx set write off
18248 If you specify @samp{set write on}, @value{GDBN} opens executable and
18249 core files for both reading and writing; if you specify @kbd{set write
18250 off} (the default), @value{GDBN} opens them read-only.
18252 If you have already loaded a file, you must load it again (using the
18253 @code{exec-file} or @code{core-file} command) after changing @code{set
18254 write}, for your new setting to take effect.
18258 Display whether executable files and core files are opened for writing
18259 as well as reading.
18262 @node Compiling and Injecting Code
18263 @section Compiling and injecting code in @value{GDBN}
18264 @cindex injecting code
18265 @cindex writing into executables
18266 @cindex compiling code
18268 @value{GDBN} supports on-demand compilation and code injection into
18269 programs running under @value{GDBN}. GCC 5.0 or higher built with
18270 @file{libcc1.so} must be installed for this functionality to be enabled.
18271 This functionality is implemented with the following commands.
18274 @kindex compile code
18275 @item compile code @var{source-code}
18276 @itemx compile code -raw @var{--} @var{source-code}
18277 Compile @var{source-code} with the compiler language found as the current
18278 language in @value{GDBN} (@pxref{Languages}). If compilation and
18279 injection is not supported with the current language specified in
18280 @value{GDBN}, or the compiler does not support this feature, an error
18281 message will be printed. If @var{source-code} compiles and links
18282 successfully, @value{GDBN} will load the object-code emitted,
18283 and execute it within the context of the currently selected inferior.
18284 It is important to note that the compiled code is executed immediately.
18285 After execution, the compiled code is removed from @value{GDBN} and any
18286 new types or variables you have defined will be deleted.
18288 The command allows you to specify @var{source-code} in two ways.
18289 The simplest method is to provide a single line of code to the command.
18293 compile code printf ("hello world\n");
18296 If you specify options on the command line as well as source code, they
18297 may conflict. The @samp{--} delimiter can be used to separate options
18298 from actual source code. E.g.:
18301 compile code -r -- printf ("hello world\n");
18304 Alternatively you can enter source code as multiple lines of text. To
18305 enter this mode, invoke the @samp{compile code} command without any text
18306 following the command. This will start the multiple-line editor and
18307 allow you to type as many lines of source code as required. When you
18308 have completed typing, enter @samp{end} on its own line to exit the
18313 >printf ("hello\n");
18314 >printf ("world\n");
18318 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18319 provided @var{source-code} in a callable scope. In this case, you must
18320 specify the entry point of the code by defining a function named
18321 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18322 inferior. Using @samp{-raw} option may be needed for example when
18323 @var{source-code} requires @samp{#include} lines which may conflict with
18324 inferior symbols otherwise.
18326 @kindex compile file
18327 @item compile file @var{filename}
18328 @itemx compile file -raw @var{filename}
18329 Like @code{compile code}, but take the source code from @var{filename}.
18332 compile file /home/user/example.c
18337 @item compile print @var{expr}
18338 @itemx compile print /@var{f} @var{expr}
18339 Compile and execute @var{expr} with the compiler language found as the
18340 current language in @value{GDBN} (@pxref{Languages}). By default the
18341 value of @var{expr} is printed in a format appropriate to its data type;
18342 you can choose a different format by specifying @samp{/@var{f}}, where
18343 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18346 @item compile print
18347 @itemx compile print /@var{f}
18348 @cindex reprint the last value
18349 Alternatively you can enter the expression (source code producing it) as
18350 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18351 command without any text following the command. This will start the
18352 multiple-line editor.
18356 The process of compiling and injecting the code can be inspected using:
18359 @anchor{set debug compile}
18360 @item set debug compile
18361 @cindex compile command debugging info
18362 Turns on or off display of @value{GDBN} process of compiling and
18363 injecting the code. The default is off.
18365 @item show debug compile
18366 Displays the current state of displaying @value{GDBN} process of
18367 compiling and injecting the code.
18370 @subsection Compilation options for the @code{compile} command
18372 @value{GDBN} needs to specify the right compilation options for the code
18373 to be injected, in part to make its ABI compatible with the inferior
18374 and in part to make the injected code compatible with @value{GDBN}'s
18378 The options used, in increasing precedence:
18381 @item target architecture and OS options (@code{gdbarch})
18382 These options depend on target processor type and target operating
18383 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18384 (@code{-m64}) compilation option.
18386 @item compilation options recorded in the target
18387 @value{NGCC} (since version 4.7) stores the options used for compilation
18388 into @code{DW_AT_producer} part of DWARF debugging information according
18389 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18390 explicitly specify @code{-g} during inferior compilation otherwise
18391 @value{NGCC} produces no DWARF. This feature is only relevant for
18392 platforms where @code{-g} produces DWARF by default, otherwise one may
18393 try to enforce DWARF by using @code{-gdwarf-4}.
18395 @item compilation options set by @code{set compile-args}
18399 You can override compilation options using the following command:
18402 @item set compile-args
18403 @cindex compile command options override
18404 Set compilation options used for compiling and injecting code with the
18405 @code{compile} commands. These options override any conflicting ones
18406 from the target architecture and/or options stored during inferior
18409 @item show compile-args
18410 Displays the current state of compilation options override.
18411 This does not show all the options actually used during compilation,
18412 use @ref{set debug compile} for that.
18415 @subsection Caveats when using the @code{compile} command
18417 There are a few caveats to keep in mind when using the @code{compile}
18418 command. As the caveats are different per language, the table below
18419 highlights specific issues on a per language basis.
18422 @item C code examples and caveats
18423 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18424 attempt to compile the source code with a @samp{C} compiler. The source
18425 code provided to the @code{compile} command will have much the same
18426 access to variables and types as it normally would if it were part of
18427 the program currently being debugged in @value{GDBN}.
18429 Below is a sample program that forms the basis of the examples that
18430 follow. This program has been compiled and loaded into @value{GDBN},
18431 much like any other normal debugging session.
18434 void function1 (void)
18437 printf ("function 1\n");
18440 void function2 (void)
18455 For the purposes of the examples in this section, the program above has
18456 been compiled, loaded into @value{GDBN}, stopped at the function
18457 @code{main}, and @value{GDBN} is awaiting input from the user.
18459 To access variables and types for any program in @value{GDBN}, the
18460 program must be compiled and packaged with debug information. The
18461 @code{compile} command is not an exception to this rule. Without debug
18462 information, you can still use the @code{compile} command, but you will
18463 be very limited in what variables and types you can access.
18465 So with that in mind, the example above has been compiled with debug
18466 information enabled. The @code{compile} command will have access to
18467 all variables and types (except those that may have been optimized
18468 out). Currently, as @value{GDBN} has stopped the program in the
18469 @code{main} function, the @code{compile} command would have access to
18470 the variable @code{k}. You could invoke the @code{compile} command
18471 and type some source code to set the value of @code{k}. You can also
18472 read it, or do anything with that variable you would normally do in
18473 @code{C}. Be aware that changes to inferior variables in the
18474 @code{compile} command are persistent. In the following example:
18477 compile code k = 3;
18481 the variable @code{k} is now 3. It will retain that value until
18482 something else in the example program changes it, or another
18483 @code{compile} command changes it.
18485 Normal scope and access rules apply to source code compiled and
18486 injected by the @code{compile} command. In the example, the variables
18487 @code{j} and @code{k} are not accessible yet, because the program is
18488 currently stopped in the @code{main} function, where these variables
18489 are not in scope. Therefore, the following command
18492 compile code j = 3;
18496 will result in a compilation error message.
18498 Once the program is continued, execution will bring these variables in
18499 scope, and they will become accessible; then the code you specify via
18500 the @code{compile} command will be able to access them.
18502 You can create variables and types with the @code{compile} command as
18503 part of your source code. Variables and types that are created as part
18504 of the @code{compile} command are not visible to the rest of the program for
18505 the duration of its run. This example is valid:
18508 compile code int ff = 5; printf ("ff is %d\n", ff);
18511 However, if you were to type the following into @value{GDBN} after that
18512 command has completed:
18515 compile code printf ("ff is %d\n'', ff);
18519 a compiler error would be raised as the variable @code{ff} no longer
18520 exists. Object code generated and injected by the @code{compile}
18521 command is removed when its execution ends. Caution is advised
18522 when assigning to program variables values of variables created by the
18523 code submitted to the @code{compile} command. This example is valid:
18526 compile code int ff = 5; k = ff;
18529 The value of the variable @code{ff} is assigned to @code{k}. The variable
18530 @code{k} does not require the existence of @code{ff} to maintain the value
18531 it has been assigned. However, pointers require particular care in
18532 assignment. If the source code compiled with the @code{compile} command
18533 changed the address of a pointer in the example program, perhaps to a
18534 variable created in the @code{compile} command, that pointer would point
18535 to an invalid location when the command exits. The following example
18536 would likely cause issues with your debugged program:
18539 compile code int ff = 5; p = &ff;
18542 In this example, @code{p} would point to @code{ff} when the
18543 @code{compile} command is executing the source code provided to it.
18544 However, as variables in the (example) program persist with their
18545 assigned values, the variable @code{p} would point to an invalid
18546 location when the command exists. A general rule should be followed
18547 in that you should either assign @code{NULL} to any assigned pointers,
18548 or restore a valid location to the pointer before the command exits.
18550 Similar caution must be exercised with any structs, unions, and typedefs
18551 defined in @code{compile} command. Types defined in the @code{compile}
18552 command will no longer be available in the next @code{compile} command.
18553 Therefore, if you cast a variable to a type defined in the
18554 @code{compile} command, care must be taken to ensure that any future
18555 need to resolve the type can be achieved.
18558 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18559 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18560 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18561 Compilation failed.
18562 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18566 Variables that have been optimized away by the compiler are not
18567 accessible to the code submitted to the @code{compile} command.
18568 Access to those variables will generate a compiler error which @value{GDBN}
18569 will print to the console.
18572 @subsection Compiler search for the @code{compile} command
18574 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18575 which may not be obvious for remote targets of different architecture
18576 than where @value{GDBN} is running. Environment variable @code{PATH} on
18577 @value{GDBN} host is searched for @value{NGCC} binary matching the
18578 target architecture and operating system. This search can be overriden
18579 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18580 taken from shell that executed @value{GDBN}, it is not the value set by
18581 @value{GDBN} command @code{set environment}). @xref{Environment}.
18584 Specifically @code{PATH} is searched for binaries matching regular expression
18585 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18586 debugged. @var{arch} is processor name --- multiarch is supported, so for
18587 example both @code{i386} and @code{x86_64} targets look for pattern
18588 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18589 for pattern @code{s390x?}. @var{os} is currently supported only for
18590 pattern @code{linux(-gnu)?}.
18592 On Posix hosts the compiler driver @value{GDBN} needs to find also
18593 shared library @file{libcc1.so} from the compiler. It is searched in
18594 default shared library search path (overridable with usual environment
18595 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18596 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18597 according to the installation of the found compiler --- as possibly
18598 specified by the @code{set compile-gcc} command.
18601 @item set compile-gcc
18602 @cindex compile command driver filename override
18603 Set compilation command used for compiling and injecting code with the
18604 @code{compile} commands. If this option is not set (it is set to
18605 an empty string), the search described above will occur --- that is the
18608 @item show compile-gcc
18609 Displays the current compile command @value{NGCC} driver filename.
18610 If set, it is the main command @command{gcc}, found usually for example
18611 under name @file{x86_64-linux-gnu-gcc}.
18615 @chapter @value{GDBN} Files
18617 @value{GDBN} needs to know the file name of the program to be debugged,
18618 both in order to read its symbol table and in order to start your
18619 program. To debug a core dump of a previous run, you must also tell
18620 @value{GDBN} the name of the core dump file.
18623 * Files:: Commands to specify files
18624 * File Caching:: Information about @value{GDBN}'s file caching
18625 * Separate Debug Files:: Debugging information in separate files
18626 * MiniDebugInfo:: Debugging information in a special section
18627 * Index Files:: Index files speed up GDB
18628 * Symbol Errors:: Errors reading symbol files
18629 * Data Files:: GDB data files
18633 @section Commands to Specify Files
18635 @cindex symbol table
18636 @cindex core dump file
18638 You may want to specify executable and core dump file names. The usual
18639 way to do this is at start-up time, using the arguments to
18640 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18641 Out of @value{GDBN}}).
18643 Occasionally it is necessary to change to a different file during a
18644 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18645 specify a file you want to use. Or you are debugging a remote target
18646 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18647 Program}). In these situations the @value{GDBN} commands to specify
18648 new files are useful.
18651 @cindex executable file
18653 @item file @var{filename}
18654 Use @var{filename} as the program to be debugged. It is read for its
18655 symbols and for the contents of pure memory. It is also the program
18656 executed when you use the @code{run} command. If you do not specify a
18657 directory and the file is not found in the @value{GDBN} working directory,
18658 @value{GDBN} uses the environment variable @code{PATH} as a list of
18659 directories to search, just as the shell does when looking for a program
18660 to run. You can change the value of this variable, for both @value{GDBN}
18661 and your program, using the @code{path} command.
18663 @cindex unlinked object files
18664 @cindex patching object files
18665 You can load unlinked object @file{.o} files into @value{GDBN} using
18666 the @code{file} command. You will not be able to ``run'' an object
18667 file, but you can disassemble functions and inspect variables. Also,
18668 if the underlying BFD functionality supports it, you could use
18669 @kbd{gdb -write} to patch object files using this technique. Note
18670 that @value{GDBN} can neither interpret nor modify relocations in this
18671 case, so branches and some initialized variables will appear to go to
18672 the wrong place. But this feature is still handy from time to time.
18675 @code{file} with no argument makes @value{GDBN} discard any information it
18676 has on both executable file and the symbol table.
18679 @item exec-file @r{[} @var{filename} @r{]}
18680 Specify that the program to be run (but not the symbol table) is found
18681 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18682 if necessary to locate your program. Omitting @var{filename} means to
18683 discard information on the executable file.
18685 @kindex symbol-file
18686 @item symbol-file @r{[} @var{filename} @r{]}
18687 Read symbol table information from file @var{filename}. @code{PATH} is
18688 searched when necessary. Use the @code{file} command to get both symbol
18689 table and program to run from the same file.
18691 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18692 program's symbol table.
18694 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18695 some breakpoints and auto-display expressions. This is because they may
18696 contain pointers to the internal data recording symbols and data types,
18697 which are part of the old symbol table data being discarded inside
18700 @code{symbol-file} does not repeat if you press @key{RET} again after
18703 When @value{GDBN} is configured for a particular environment, it
18704 understands debugging information in whatever format is the standard
18705 generated for that environment; you may use either a @sc{gnu} compiler, or
18706 other compilers that adhere to the local conventions.
18707 Best results are usually obtained from @sc{gnu} compilers; for example,
18708 using @code{@value{NGCC}} you can generate debugging information for
18711 For most kinds of object files, with the exception of old SVR3 systems
18712 using COFF, the @code{symbol-file} command does not normally read the
18713 symbol table in full right away. Instead, it scans the symbol table
18714 quickly to find which source files and which symbols are present. The
18715 details are read later, one source file at a time, as they are needed.
18717 The purpose of this two-stage reading strategy is to make @value{GDBN}
18718 start up faster. For the most part, it is invisible except for
18719 occasional pauses while the symbol table details for a particular source
18720 file are being read. (The @code{set verbose} command can turn these
18721 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18722 Warnings and Messages}.)
18724 We have not implemented the two-stage strategy for COFF yet. When the
18725 symbol table is stored in COFF format, @code{symbol-file} reads the
18726 symbol table data in full right away. Note that ``stabs-in-COFF''
18727 still does the two-stage strategy, since the debug info is actually
18731 @cindex reading symbols immediately
18732 @cindex symbols, reading immediately
18733 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18734 @itemx file @r{[} -readnow @r{]} @var{filename}
18735 You can override the @value{GDBN} two-stage strategy for reading symbol
18736 tables by using the @samp{-readnow} option with any of the commands that
18737 load symbol table information, if you want to be sure @value{GDBN} has the
18738 entire symbol table available.
18740 @cindex @code{-readnever}, option for symbol-file command
18741 @cindex never read symbols
18742 @cindex symbols, never read
18743 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18744 @itemx file @r{[} -readnever @r{]} @var{filename}
18745 You can instruct @value{GDBN} to never read the symbolic information
18746 contained in @var{filename} by using the @samp{-readnever} option.
18747 @xref{--readnever}.
18749 @c FIXME: for now no mention of directories, since this seems to be in
18750 @c flux. 13mar1992 status is that in theory GDB would look either in
18751 @c current dir or in same dir as myprog; but issues like competing
18752 @c GDB's, or clutter in system dirs, mean that in practice right now
18753 @c only current dir is used. FFish says maybe a special GDB hierarchy
18754 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18758 @item core-file @r{[}@var{filename}@r{]}
18760 Specify the whereabouts of a core dump file to be used as the ``contents
18761 of memory''. Traditionally, core files contain only some parts of the
18762 address space of the process that generated them; @value{GDBN} can access the
18763 executable file itself for other parts.
18765 @code{core-file} with no argument specifies that no core file is
18768 Note that the core file is ignored when your program is actually running
18769 under @value{GDBN}. So, if you have been running your program and you
18770 wish to debug a core file instead, you must kill the subprocess in which
18771 the program is running. To do this, use the @code{kill} command
18772 (@pxref{Kill Process, ,Killing the Child Process}).
18774 @kindex add-symbol-file
18775 @cindex dynamic linking
18776 @item add-symbol-file @var{filename} @var{address}
18777 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18778 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18779 The @code{add-symbol-file} command reads additional symbol table
18780 information from the file @var{filename}. You would use this command
18781 when @var{filename} has been dynamically loaded (by some other means)
18782 into the program that is running. The @var{address} should give the memory
18783 address at which the file has been loaded; @value{GDBN} cannot figure
18784 this out for itself. You can additionally specify an arbitrary number
18785 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18786 section name and base address for that section. You can specify any
18787 @var{address} as an expression.
18789 The symbol table of the file @var{filename} is added to the symbol table
18790 originally read with the @code{symbol-file} command. You can use the
18791 @code{add-symbol-file} command any number of times; the new symbol data
18792 thus read is kept in addition to the old.
18794 Changes can be reverted using the command @code{remove-symbol-file}.
18796 @cindex relocatable object files, reading symbols from
18797 @cindex object files, relocatable, reading symbols from
18798 @cindex reading symbols from relocatable object files
18799 @cindex symbols, reading from relocatable object files
18800 @cindex @file{.o} files, reading symbols from
18801 Although @var{filename} is typically a shared library file, an
18802 executable file, or some other object file which has been fully
18803 relocated for loading into a process, you can also load symbolic
18804 information from relocatable @file{.o} files, as long as:
18808 the file's symbolic information refers only to linker symbols defined in
18809 that file, not to symbols defined by other object files,
18811 every section the file's symbolic information refers to has actually
18812 been loaded into the inferior, as it appears in the file, and
18814 you can determine the address at which every section was loaded, and
18815 provide these to the @code{add-symbol-file} command.
18819 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18820 relocatable files into an already running program; such systems
18821 typically make the requirements above easy to meet. However, it's
18822 important to recognize that many native systems use complex link
18823 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18824 assembly, for example) that make the requirements difficult to meet. In
18825 general, one cannot assume that using @code{add-symbol-file} to read a
18826 relocatable object file's symbolic information will have the same effect
18827 as linking the relocatable object file into the program in the normal
18830 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18832 @kindex remove-symbol-file
18833 @item remove-symbol-file @var{filename}
18834 @item remove-symbol-file -a @var{address}
18835 Remove a symbol file added via the @code{add-symbol-file} command. The
18836 file to remove can be identified by its @var{filename} or by an @var{address}
18837 that lies within the boundaries of this symbol file in memory. Example:
18840 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18841 add symbol table from file "/home/user/gdb/mylib.so" at
18842 .text_addr = 0x7ffff7ff9480
18844 Reading symbols from /home/user/gdb/mylib.so...done.
18845 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18846 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18851 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18853 @kindex add-symbol-file-from-memory
18854 @cindex @code{syscall DSO}
18855 @cindex load symbols from memory
18856 @item add-symbol-file-from-memory @var{address}
18857 Load symbols from the given @var{address} in a dynamically loaded
18858 object file whose image is mapped directly into the inferior's memory.
18859 For example, the Linux kernel maps a @code{syscall DSO} into each
18860 process's address space; this DSO provides kernel-specific code for
18861 some system calls. The argument can be any expression whose
18862 evaluation yields the address of the file's shared object file header.
18863 For this command to work, you must have used @code{symbol-file} or
18864 @code{exec-file} commands in advance.
18867 @item section @var{section} @var{addr}
18868 The @code{section} command changes the base address of the named
18869 @var{section} of the exec file to @var{addr}. This can be used if the
18870 exec file does not contain section addresses, (such as in the
18871 @code{a.out} format), or when the addresses specified in the file
18872 itself are wrong. Each section must be changed separately. The
18873 @code{info files} command, described below, lists all the sections and
18877 @kindex info target
18880 @code{info files} and @code{info target} are synonymous; both print the
18881 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18882 including the names of the executable and core dump files currently in
18883 use by @value{GDBN}, and the files from which symbols were loaded. The
18884 command @code{help target} lists all possible targets rather than
18887 @kindex maint info sections
18888 @item maint info sections
18889 Another command that can give you extra information about program sections
18890 is @code{maint info sections}. In addition to the section information
18891 displayed by @code{info files}, this command displays the flags and file
18892 offset of each section in the executable and core dump files. In addition,
18893 @code{maint info sections} provides the following command options (which
18894 may be arbitrarily combined):
18898 Display sections for all loaded object files, including shared libraries.
18899 @item @var{sections}
18900 Display info only for named @var{sections}.
18901 @item @var{section-flags}
18902 Display info only for sections for which @var{section-flags} are true.
18903 The section flags that @value{GDBN} currently knows about are:
18906 Section will have space allocated in the process when loaded.
18907 Set for all sections except those containing debug information.
18909 Section will be loaded from the file into the child process memory.
18910 Set for pre-initialized code and data, clear for @code{.bss} sections.
18912 Section needs to be relocated before loading.
18914 Section cannot be modified by the child process.
18916 Section contains executable code only.
18918 Section contains data only (no executable code).
18920 Section will reside in ROM.
18922 Section contains data for constructor/destructor lists.
18924 Section is not empty.
18926 An instruction to the linker to not output the section.
18927 @item COFF_SHARED_LIBRARY
18928 A notification to the linker that the section contains
18929 COFF shared library information.
18931 Section contains common symbols.
18934 @kindex set trust-readonly-sections
18935 @cindex read-only sections
18936 @item set trust-readonly-sections on
18937 Tell @value{GDBN} that readonly sections in your object file
18938 really are read-only (i.e.@: that their contents will not change).
18939 In that case, @value{GDBN} can fetch values from these sections
18940 out of the object file, rather than from the target program.
18941 For some targets (notably embedded ones), this can be a significant
18942 enhancement to debugging performance.
18944 The default is off.
18946 @item set trust-readonly-sections off
18947 Tell @value{GDBN} not to trust readonly sections. This means that
18948 the contents of the section might change while the program is running,
18949 and must therefore be fetched from the target when needed.
18951 @item show trust-readonly-sections
18952 Show the current setting of trusting readonly sections.
18955 All file-specifying commands allow both absolute and relative file names
18956 as arguments. @value{GDBN} always converts the file name to an absolute file
18957 name and remembers it that way.
18959 @cindex shared libraries
18960 @anchor{Shared Libraries}
18961 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18962 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18963 DSBT (TIC6X) shared libraries.
18965 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18966 shared libraries. @xref{Expat}.
18968 @value{GDBN} automatically loads symbol definitions from shared libraries
18969 when you use the @code{run} command, or when you examine a core file.
18970 (Before you issue the @code{run} command, @value{GDBN} does not understand
18971 references to a function in a shared library, however---unless you are
18972 debugging a core file).
18974 @c FIXME: some @value{GDBN} release may permit some refs to undef
18975 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18976 @c FIXME...lib; check this from time to time when updating manual
18978 There are times, however, when you may wish to not automatically load
18979 symbol definitions from shared libraries, such as when they are
18980 particularly large or there are many of them.
18982 To control the automatic loading of shared library symbols, use the
18986 @kindex set auto-solib-add
18987 @item set auto-solib-add @var{mode}
18988 If @var{mode} is @code{on}, symbols from all shared object libraries
18989 will be loaded automatically when the inferior begins execution, you
18990 attach to an independently started inferior, or when the dynamic linker
18991 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18992 is @code{off}, symbols must be loaded manually, using the
18993 @code{sharedlibrary} command. The default value is @code{on}.
18995 @cindex memory used for symbol tables
18996 If your program uses lots of shared libraries with debug info that
18997 takes large amounts of memory, you can decrease the @value{GDBN}
18998 memory footprint by preventing it from automatically loading the
18999 symbols from shared libraries. To that end, type @kbd{set
19000 auto-solib-add off} before running the inferior, then load each
19001 library whose debug symbols you do need with @kbd{sharedlibrary
19002 @var{regexp}}, where @var{regexp} is a regular expression that matches
19003 the libraries whose symbols you want to be loaded.
19005 @kindex show auto-solib-add
19006 @item show auto-solib-add
19007 Display the current autoloading mode.
19010 @cindex load shared library
19011 To explicitly load shared library symbols, use the @code{sharedlibrary}
19015 @kindex info sharedlibrary
19017 @item info share @var{regex}
19018 @itemx info sharedlibrary @var{regex}
19019 Print the names of the shared libraries which are currently loaded
19020 that match @var{regex}. If @var{regex} is omitted then print
19021 all shared libraries that are loaded.
19024 @item info dll @var{regex}
19025 This is an alias of @code{info sharedlibrary}.
19027 @kindex sharedlibrary
19029 @item sharedlibrary @var{regex}
19030 @itemx share @var{regex}
19031 Load shared object library symbols for files matching a
19032 Unix regular expression.
19033 As with files loaded automatically, it only loads shared libraries
19034 required by your program for a core file or after typing @code{run}. If
19035 @var{regex} is omitted all shared libraries required by your program are
19038 @item nosharedlibrary
19039 @kindex nosharedlibrary
19040 @cindex unload symbols from shared libraries
19041 Unload all shared object library symbols. This discards all symbols
19042 that have been loaded from all shared libraries. Symbols from shared
19043 libraries that were loaded by explicit user requests are not
19047 Sometimes you may wish that @value{GDBN} stops and gives you control
19048 when any of shared library events happen. The best way to do this is
19049 to use @code{catch load} and @code{catch unload} (@pxref{Set
19052 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19053 command for this. This command exists for historical reasons. It is
19054 less useful than setting a catchpoint, because it does not allow for
19055 conditions or commands as a catchpoint does.
19058 @item set stop-on-solib-events
19059 @kindex set stop-on-solib-events
19060 This command controls whether @value{GDBN} should give you control
19061 when the dynamic linker notifies it about some shared library event.
19062 The most common event of interest is loading or unloading of a new
19065 @item show stop-on-solib-events
19066 @kindex show stop-on-solib-events
19067 Show whether @value{GDBN} stops and gives you control when shared
19068 library events happen.
19071 Shared libraries are also supported in many cross or remote debugging
19072 configurations. @value{GDBN} needs to have access to the target's libraries;
19073 this can be accomplished either by providing copies of the libraries
19074 on the host system, or by asking @value{GDBN} to automatically retrieve the
19075 libraries from the target. If copies of the target libraries are
19076 provided, they need to be the same as the target libraries, although the
19077 copies on the target can be stripped as long as the copies on the host are
19080 @cindex where to look for shared libraries
19081 For remote debugging, you need to tell @value{GDBN} where the target
19082 libraries are, so that it can load the correct copies---otherwise, it
19083 may try to load the host's libraries. @value{GDBN} has two variables
19084 to specify the search directories for target libraries.
19087 @cindex prefix for executable and shared library file names
19088 @cindex system root, alternate
19089 @kindex set solib-absolute-prefix
19090 @kindex set sysroot
19091 @item set sysroot @var{path}
19092 Use @var{path} as the system root for the program being debugged. Any
19093 absolute shared library paths will be prefixed with @var{path}; many
19094 runtime loaders store the absolute paths to the shared library in the
19095 target program's memory. When starting processes remotely, and when
19096 attaching to already-running processes (local or remote), their
19097 executable filenames will be prefixed with @var{path} if reported to
19098 @value{GDBN} as absolute by the operating system. If you use
19099 @code{set sysroot} to find executables and shared libraries, they need
19100 to be laid out in the same way that they are on the target, with
19101 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19104 If @var{path} starts with the sequence @file{target:} and the target
19105 system is remote then @value{GDBN} will retrieve the target binaries
19106 from the remote system. This is only supported when using a remote
19107 target that supports the @code{remote get} command (@pxref{File
19108 Transfer,,Sending files to a remote system}). The part of @var{path}
19109 following the initial @file{target:} (if present) is used as system
19110 root prefix on the remote file system. If @var{path} starts with the
19111 sequence @file{remote:} this is converted to the sequence
19112 @file{target:} by @code{set sysroot}@footnote{Historically the
19113 functionality to retrieve binaries from the remote system was
19114 provided by prefixing @var{path} with @file{remote:}}. If you want
19115 to specify a local system root using a directory that happens to be
19116 named @file{target:} or @file{remote:}, you need to use some
19117 equivalent variant of the name like @file{./target:}.
19119 For targets with an MS-DOS based filesystem, such as MS-Windows and
19120 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19121 absolute file name with @var{path}. But first, on Unix hosts,
19122 @value{GDBN} converts all backslash directory separators into forward
19123 slashes, because the backslash is not a directory separator on Unix:
19126 c:\foo\bar.dll @result{} c:/foo/bar.dll
19129 Then, @value{GDBN} attempts prefixing the target file name with
19130 @var{path}, and looks for the resulting file name in the host file
19134 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19137 If that does not find the binary, @value{GDBN} tries removing
19138 the @samp{:} character from the drive spec, both for convenience, and,
19139 for the case of the host file system not supporting file names with
19143 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19146 This makes it possible to have a system root that mirrors a target
19147 with more than one drive. E.g., you may want to setup your local
19148 copies of the target system shared libraries like so (note @samp{c} vs
19152 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19153 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19154 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19158 and point the system root at @file{/path/to/sysroot}, so that
19159 @value{GDBN} can find the correct copies of both
19160 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19162 If that still does not find the binary, @value{GDBN} tries
19163 removing the whole drive spec from the target file name:
19166 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19169 This last lookup makes it possible to not care about the drive name,
19170 if you don't want or need to.
19172 The @code{set solib-absolute-prefix} command is an alias for @code{set
19175 @cindex default system root
19176 @cindex @samp{--with-sysroot}
19177 You can set the default system root by using the configure-time
19178 @samp{--with-sysroot} option. If the system root is inside
19179 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19180 @samp{--exec-prefix}), then the default system root will be updated
19181 automatically if the installed @value{GDBN} is moved to a new
19184 @kindex show sysroot
19186 Display the current executable and shared library prefix.
19188 @kindex set solib-search-path
19189 @item set solib-search-path @var{path}
19190 If this variable is set, @var{path} is a colon-separated list of
19191 directories to search for shared libraries. @samp{solib-search-path}
19192 is used after @samp{sysroot} fails to locate the library, or if the
19193 path to the library is relative instead of absolute. If you want to
19194 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19195 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19196 finding your host's libraries. @samp{sysroot} is preferred; setting
19197 it to a nonexistent directory may interfere with automatic loading
19198 of shared library symbols.
19200 @kindex show solib-search-path
19201 @item show solib-search-path
19202 Display the current shared library search path.
19204 @cindex DOS file-name semantics of file names.
19205 @kindex set target-file-system-kind (unix|dos-based|auto)
19206 @kindex show target-file-system-kind
19207 @item set target-file-system-kind @var{kind}
19208 Set assumed file system kind for target reported file names.
19210 Shared library file names as reported by the target system may not
19211 make sense as is on the system @value{GDBN} is running on. For
19212 example, when remote debugging a target that has MS-DOS based file
19213 system semantics, from a Unix host, the target may be reporting to
19214 @value{GDBN} a list of loaded shared libraries with file names such as
19215 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19216 drive letters, so the @samp{c:\} prefix is not normally understood as
19217 indicating an absolute file name, and neither is the backslash
19218 normally considered a directory separator character. In that case,
19219 the native file system would interpret this whole absolute file name
19220 as a relative file name with no directory components. This would make
19221 it impossible to point @value{GDBN} at a copy of the remote target's
19222 shared libraries on the host using @code{set sysroot}, and impractical
19223 with @code{set solib-search-path}. Setting
19224 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19225 to interpret such file names similarly to how the target would, and to
19226 map them to file names valid on @value{GDBN}'s native file system
19227 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19228 to one of the supported file system kinds. In that case, @value{GDBN}
19229 tries to determine the appropriate file system variant based on the
19230 current target's operating system (@pxref{ABI, ,Configuring the
19231 Current ABI}). The supported file system settings are:
19235 Instruct @value{GDBN} to assume the target file system is of Unix
19236 kind. Only file names starting the forward slash (@samp{/}) character
19237 are considered absolute, and the directory separator character is also
19241 Instruct @value{GDBN} to assume the target file system is DOS based.
19242 File names starting with either a forward slash, or a drive letter
19243 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19244 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19245 considered directory separators.
19248 Instruct @value{GDBN} to use the file system kind associated with the
19249 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19250 This is the default.
19254 @cindex file name canonicalization
19255 @cindex base name differences
19256 When processing file names provided by the user, @value{GDBN}
19257 frequently needs to compare them to the file names recorded in the
19258 program's debug info. Normally, @value{GDBN} compares just the
19259 @dfn{base names} of the files as strings, which is reasonably fast
19260 even for very large programs. (The base name of a file is the last
19261 portion of its name, after stripping all the leading directories.)
19262 This shortcut in comparison is based upon the assumption that files
19263 cannot have more than one base name. This is usually true, but
19264 references to files that use symlinks or similar filesystem
19265 facilities violate that assumption. If your program records files
19266 using such facilities, or if you provide file names to @value{GDBN}
19267 using symlinks etc., you can set @code{basenames-may-differ} to
19268 @code{true} to instruct @value{GDBN} to completely canonicalize each
19269 pair of file names it needs to compare. This will make file-name
19270 comparisons accurate, but at a price of a significant slowdown.
19273 @item set basenames-may-differ
19274 @kindex set basenames-may-differ
19275 Set whether a source file may have multiple base names.
19277 @item show basenames-may-differ
19278 @kindex show basenames-may-differ
19279 Show whether a source file may have multiple base names.
19283 @section File Caching
19284 @cindex caching of opened files
19285 @cindex caching of bfd objects
19287 To speed up file loading, and reduce memory usage, @value{GDBN} will
19288 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19289 BFD, bfd, The Binary File Descriptor Library}. The following commands
19290 allow visibility and control of the caching behavior.
19293 @kindex maint info bfds
19294 @item maint info bfds
19295 This prints information about each @code{bfd} object that is known to
19298 @kindex maint set bfd-sharing
19299 @kindex maint show bfd-sharing
19300 @kindex bfd caching
19301 @item maint set bfd-sharing
19302 @item maint show bfd-sharing
19303 Control whether @code{bfd} objects can be shared. When sharing is
19304 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19305 than reopening the same file. Turning sharing off does not cause
19306 already shared @code{bfd} objects to be unshared, but all future files
19307 that are opened will create a new @code{bfd} object. Similarly,
19308 re-enabling sharing does not cause multiple existing @code{bfd}
19309 objects to be collapsed into a single shared @code{bfd} object.
19311 @kindex set debug bfd-cache @var{level}
19312 @kindex bfd caching
19313 @item set debug bfd-cache @var{level}
19314 Turns on debugging of the bfd cache, setting the level to @var{level}.
19316 @kindex show debug bfd-cache
19317 @kindex bfd caching
19318 @item show debug bfd-cache
19319 Show the current debugging level of the bfd cache.
19322 @node Separate Debug Files
19323 @section Debugging Information in Separate Files
19324 @cindex separate debugging information files
19325 @cindex debugging information in separate files
19326 @cindex @file{.debug} subdirectories
19327 @cindex debugging information directory, global
19328 @cindex global debugging information directories
19329 @cindex build ID, and separate debugging files
19330 @cindex @file{.build-id} directory
19332 @value{GDBN} allows you to put a program's debugging information in a
19333 file separate from the executable itself, in a way that allows
19334 @value{GDBN} to find and load the debugging information automatically.
19335 Since debugging information can be very large---sometimes larger
19336 than the executable code itself---some systems distribute debugging
19337 information for their executables in separate files, which users can
19338 install only when they need to debug a problem.
19340 @value{GDBN} supports two ways of specifying the separate debug info
19345 The executable contains a @dfn{debug link} that specifies the name of
19346 the separate debug info file. The separate debug file's name is
19347 usually @file{@var{executable}.debug}, where @var{executable} is the
19348 name of the corresponding executable file without leading directories
19349 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19350 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19351 checksum for the debug file, which @value{GDBN} uses to validate that
19352 the executable and the debug file came from the same build.
19355 The executable contains a @dfn{build ID}, a unique bit string that is
19356 also present in the corresponding debug info file. (This is supported
19357 only on some operating systems, when using the ELF or PE file formats
19358 for binary files and the @sc{gnu} Binutils.) For more details about
19359 this feature, see the description of the @option{--build-id}
19360 command-line option in @ref{Options, , Command Line Options, ld.info,
19361 The GNU Linker}. The debug info file's name is not specified
19362 explicitly by the build ID, but can be computed from the build ID, see
19366 Depending on the way the debug info file is specified, @value{GDBN}
19367 uses two different methods of looking for the debug file:
19371 For the ``debug link'' method, @value{GDBN} looks up the named file in
19372 the directory of the executable file, then in a subdirectory of that
19373 directory named @file{.debug}, and finally under each one of the global debug
19374 directories, in a subdirectory whose name is identical to the leading
19375 directories of the executable's absolute file name.
19378 For the ``build ID'' method, @value{GDBN} looks in the
19379 @file{.build-id} subdirectory of each one of the global debug directories for
19380 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19381 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19382 are the rest of the bit string. (Real build ID strings are 32 or more
19383 hex characters, not 10.)
19386 So, for example, suppose you ask @value{GDBN} to debug
19387 @file{/usr/bin/ls}, which has a debug link that specifies the
19388 file @file{ls.debug}, and a build ID whose value in hex is
19389 @code{abcdef1234}. If the list of the global debug directories includes
19390 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19391 debug information files, in the indicated order:
19395 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19397 @file{/usr/bin/ls.debug}
19399 @file{/usr/bin/.debug/ls.debug}
19401 @file{/usr/lib/debug/usr/bin/ls.debug}.
19404 @anchor{debug-file-directory}
19405 Global debugging info directories default to what is set by @value{GDBN}
19406 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19407 you can also set the global debugging info directories, and view the list
19408 @value{GDBN} is currently using.
19412 @kindex set debug-file-directory
19413 @item set debug-file-directory @var{directories}
19414 Set the directories which @value{GDBN} searches for separate debugging
19415 information files to @var{directory}. Multiple path components can be set
19416 concatenating them by a path separator.
19418 @kindex show debug-file-directory
19419 @item show debug-file-directory
19420 Show the directories @value{GDBN} searches for separate debugging
19425 @cindex @code{.gnu_debuglink} sections
19426 @cindex debug link sections
19427 A debug link is a special section of the executable file named
19428 @code{.gnu_debuglink}. The section must contain:
19432 A filename, with any leading directory components removed, followed by
19435 zero to three bytes of padding, as needed to reach the next four-byte
19436 boundary within the section, and
19438 a four-byte CRC checksum, stored in the same endianness used for the
19439 executable file itself. The checksum is computed on the debugging
19440 information file's full contents by the function given below, passing
19441 zero as the @var{crc} argument.
19444 Any executable file format can carry a debug link, as long as it can
19445 contain a section named @code{.gnu_debuglink} with the contents
19448 @cindex @code{.note.gnu.build-id} sections
19449 @cindex build ID sections
19450 The build ID is a special section in the executable file (and in other
19451 ELF binary files that @value{GDBN} may consider). This section is
19452 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19453 It contains unique identification for the built files---the ID remains
19454 the same across multiple builds of the same build tree. The default
19455 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19456 content for the build ID string. The same section with an identical
19457 value is present in the original built binary with symbols, in its
19458 stripped variant, and in the separate debugging information file.
19460 The debugging information file itself should be an ordinary
19461 executable, containing a full set of linker symbols, sections, and
19462 debugging information. The sections of the debugging information file
19463 should have the same names, addresses, and sizes as the original file,
19464 but they need not contain any data---much like a @code{.bss} section
19465 in an ordinary executable.
19467 The @sc{gnu} binary utilities (Binutils) package includes the
19468 @samp{objcopy} utility that can produce
19469 the separated executable / debugging information file pairs using the
19470 following commands:
19473 @kbd{objcopy --only-keep-debug foo foo.debug}
19478 These commands remove the debugging
19479 information from the executable file @file{foo} and place it in the file
19480 @file{foo.debug}. You can use the first, second or both methods to link the
19485 The debug link method needs the following additional command to also leave
19486 behind a debug link in @file{foo}:
19489 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19492 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19493 a version of the @code{strip} command such that the command @kbd{strip foo -f
19494 foo.debug} has the same functionality as the two @code{objcopy} commands and
19495 the @code{ln -s} command above, together.
19498 Build ID gets embedded into the main executable using @code{ld --build-id} or
19499 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19500 compatibility fixes for debug files separation are present in @sc{gnu} binary
19501 utilities (Binutils) package since version 2.18.
19506 @cindex CRC algorithm definition
19507 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19508 IEEE 802.3 using the polynomial:
19510 @c TexInfo requires naked braces for multi-digit exponents for Tex
19511 @c output, but this causes HTML output to barf. HTML has to be set using
19512 @c raw commands. So we end up having to specify this equation in 2
19517 <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>
19518 + <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
19524 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19525 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19529 The function is computed byte at a time, taking the least
19530 significant bit of each byte first. The initial pattern
19531 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19532 the final result is inverted to ensure trailing zeros also affect the
19535 @emph{Note:} This is the same CRC polynomial as used in handling the
19536 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19537 However in the case of the Remote Serial Protocol, the CRC is computed
19538 @emph{most} significant bit first, and the result is not inverted, so
19539 trailing zeros have no effect on the CRC value.
19541 To complete the description, we show below the code of the function
19542 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19543 initially supplied @code{crc} argument means that an initial call to
19544 this function passing in zero will start computing the CRC using
19547 @kindex gnu_debuglink_crc32
19550 gnu_debuglink_crc32 (unsigned long crc,
19551 unsigned char *buf, size_t len)
19553 static const unsigned long crc32_table[256] =
19555 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19556 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19557 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19558 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19559 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19560 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19561 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19562 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19563 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19564 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19565 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19566 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19567 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19568 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19569 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19570 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19571 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19572 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19573 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19574 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19575 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19576 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19577 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19578 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19579 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19580 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19581 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19582 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19583 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19584 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19585 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19586 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19587 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19588 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19589 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19590 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19591 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19592 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19593 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19594 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19595 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19596 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19597 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19598 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19599 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19600 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19601 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19602 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19603 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19604 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19605 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19608 unsigned char *end;
19610 crc = ~crc & 0xffffffff;
19611 for (end = buf + len; buf < end; ++buf)
19612 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19613 return ~crc & 0xffffffff;
19618 This computation does not apply to the ``build ID'' method.
19620 @node MiniDebugInfo
19621 @section Debugging information in a special section
19622 @cindex separate debug sections
19623 @cindex @samp{.gnu_debugdata} section
19625 Some systems ship pre-built executables and libraries that have a
19626 special @samp{.gnu_debugdata} section. This feature is called
19627 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19628 is used to supply extra symbols for backtraces.
19630 The intent of this section is to provide extra minimal debugging
19631 information for use in simple backtraces. It is not intended to be a
19632 replacement for full separate debugging information (@pxref{Separate
19633 Debug Files}). The example below shows the intended use; however,
19634 @value{GDBN} does not currently put restrictions on what sort of
19635 debugging information might be included in the section.
19637 @value{GDBN} has support for this extension. If the section exists,
19638 then it is used provided that no other source of debugging information
19639 can be found, and that @value{GDBN} was configured with LZMA support.
19641 This section can be easily created using @command{objcopy} and other
19642 standard utilities:
19645 # Extract the dynamic symbols from the main binary, there is no need
19646 # to also have these in the normal symbol table.
19647 nm -D @var{binary} --format=posix --defined-only \
19648 | awk '@{ print $1 @}' | sort > dynsyms
19650 # Extract all the text (i.e. function) symbols from the debuginfo.
19651 # (Note that we actually also accept "D" symbols, for the benefit
19652 # of platforms like PowerPC64 that use function descriptors.)
19653 nm @var{binary} --format=posix --defined-only \
19654 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19657 # Keep all the function symbols not already in the dynamic symbol
19659 comm -13 dynsyms funcsyms > keep_symbols
19661 # Separate full debug info into debug binary.
19662 objcopy --only-keep-debug @var{binary} debug
19664 # Copy the full debuginfo, keeping only a minimal set of symbols and
19665 # removing some unnecessary sections.
19666 objcopy -S --remove-section .gdb_index --remove-section .comment \
19667 --keep-symbols=keep_symbols debug mini_debuginfo
19669 # Drop the full debug info from the original binary.
19670 strip --strip-all -R .comment @var{binary}
19672 # Inject the compressed data into the .gnu_debugdata section of the
19675 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19679 @section Index Files Speed Up @value{GDBN}
19680 @cindex index files
19681 @cindex @samp{.gdb_index} section
19683 When @value{GDBN} finds a symbol file, it scans the symbols in the
19684 file in order to construct an internal symbol table. This lets most
19685 @value{GDBN} operations work quickly---at the cost of a delay early
19686 on. For large programs, this delay can be quite lengthy, so
19687 @value{GDBN} provides a way to build an index, which speeds up
19690 The index is stored as a section in the symbol file. @value{GDBN} can
19691 write the index to a file, then you can put it into the symbol file
19692 using @command{objcopy}.
19694 To create an index file, use the @code{save gdb-index} command:
19697 @item save gdb-index [-dwarf-5] @var{directory}
19698 @kindex save gdb-index
19699 Create index files for all symbol files currently known by
19700 @value{GDBN}. For each known @var{symbol-file}, this command by
19701 default creates it produces a single file
19702 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19703 the @option{-dwarf-5} option, it produces 2 files:
19704 @file{@var{symbol-file}.debug_names} and
19705 @file{@var{symbol-file}.debug_str}. The files are created in the
19706 given @var{directory}.
19709 Once you have created an index file you can merge it into your symbol
19710 file, here named @file{symfile}, using @command{objcopy}:
19713 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19714 --set-section-flags .gdb_index=readonly symfile symfile
19717 Or for @code{-dwarf-5}:
19720 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19721 $ cat symfile.debug_str >>symfile.debug_str.new
19722 $ objcopy --add-section .debug_names=symfile.gdb-index \
19723 --set-section-flags .debug_names=readonly \
19724 --update-section .debug_str=symfile.debug_str.new symfile symfile
19727 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19728 sections that have been deprecated. Usually they are deprecated because
19729 they are missing a new feature or have performance issues.
19730 To tell @value{GDBN} to use a deprecated index section anyway
19731 specify @code{set use-deprecated-index-sections on}.
19732 The default is @code{off}.
19733 This can speed up startup, but may result in some functionality being lost.
19734 @xref{Index Section Format}.
19736 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19737 must be done before gdb reads the file. The following will not work:
19740 $ gdb -ex "set use-deprecated-index-sections on" <program>
19743 Instead you must do, for example,
19746 $ gdb -iex "set use-deprecated-index-sections on" <program>
19749 There are currently some limitation on indices. They only work when
19750 for DWARF debugging information, not stabs. And, they do not
19751 currently work for programs using Ada.
19753 @node Symbol Errors
19754 @section Errors Reading Symbol Files
19756 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19757 such as symbol types it does not recognize, or known bugs in compiler
19758 output. By default, @value{GDBN} does not notify you of such problems, since
19759 they are relatively common and primarily of interest to people
19760 debugging compilers. If you are interested in seeing information
19761 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19762 only one message about each such type of problem, no matter how many
19763 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19764 to see how many times the problems occur, with the @code{set
19765 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19768 The messages currently printed, and their meanings, include:
19771 @item inner block not inside outer block in @var{symbol}
19773 The symbol information shows where symbol scopes begin and end
19774 (such as at the start of a function or a block of statements). This
19775 error indicates that an inner scope block is not fully contained
19776 in its outer scope blocks.
19778 @value{GDBN} circumvents the problem by treating the inner block as if it had
19779 the same scope as the outer block. In the error message, @var{symbol}
19780 may be shown as ``@code{(don't know)}'' if the outer block is not a
19783 @item block at @var{address} out of order
19785 The symbol information for symbol scope blocks should occur in
19786 order of increasing addresses. This error indicates that it does not
19789 @value{GDBN} does not circumvent this problem, and has trouble
19790 locating symbols in the source file whose symbols it is reading. (You
19791 can often determine what source file is affected by specifying
19792 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19795 @item bad block start address patched
19797 The symbol information for a symbol scope block has a start address
19798 smaller than the address of the preceding source line. This is known
19799 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19801 @value{GDBN} circumvents the problem by treating the symbol scope block as
19802 starting on the previous source line.
19804 @item bad string table offset in symbol @var{n}
19807 Symbol number @var{n} contains a pointer into the string table which is
19808 larger than the size of the string table.
19810 @value{GDBN} circumvents the problem by considering the symbol to have the
19811 name @code{foo}, which may cause other problems if many symbols end up
19814 @item unknown symbol type @code{0x@var{nn}}
19816 The symbol information contains new data types that @value{GDBN} does
19817 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19818 uncomprehended information, in hexadecimal.
19820 @value{GDBN} circumvents the error by ignoring this symbol information.
19821 This usually allows you to debug your program, though certain symbols
19822 are not accessible. If you encounter such a problem and feel like
19823 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19824 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19825 and examine @code{*bufp} to see the symbol.
19827 @item stub type has NULL name
19829 @value{GDBN} could not find the full definition for a struct or class.
19831 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19832 The symbol information for a C@t{++} member function is missing some
19833 information that recent versions of the compiler should have output for
19836 @item info mismatch between compiler and debugger
19838 @value{GDBN} could not parse a type specification output by the compiler.
19843 @section GDB Data Files
19845 @cindex prefix for data files
19846 @value{GDBN} will sometimes read an auxiliary data file. These files
19847 are kept in a directory known as the @dfn{data directory}.
19849 You can set the data directory's name, and view the name @value{GDBN}
19850 is currently using.
19853 @kindex set data-directory
19854 @item set data-directory @var{directory}
19855 Set the directory which @value{GDBN} searches for auxiliary data files
19856 to @var{directory}.
19858 @kindex show data-directory
19859 @item show data-directory
19860 Show the directory @value{GDBN} searches for auxiliary data files.
19863 @cindex default data directory
19864 @cindex @samp{--with-gdb-datadir}
19865 You can set the default data directory by using the configure-time
19866 @samp{--with-gdb-datadir} option. If the data directory is inside
19867 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19868 @samp{--exec-prefix}), then the default data directory will be updated
19869 automatically if the installed @value{GDBN} is moved to a new
19872 The data directory may also be specified with the
19873 @code{--data-directory} command line option.
19874 @xref{Mode Options}.
19877 @chapter Specifying a Debugging Target
19879 @cindex debugging target
19880 A @dfn{target} is the execution environment occupied by your program.
19882 Often, @value{GDBN} runs in the same host environment as your program;
19883 in that case, the debugging target is specified as a side effect when
19884 you use the @code{file} or @code{core} commands. When you need more
19885 flexibility---for example, running @value{GDBN} on a physically separate
19886 host, or controlling a standalone system over a serial port or a
19887 realtime system over a TCP/IP connection---you can use the @code{target}
19888 command to specify one of the target types configured for @value{GDBN}
19889 (@pxref{Target Commands, ,Commands for Managing Targets}).
19891 @cindex target architecture
19892 It is possible to build @value{GDBN} for several different @dfn{target
19893 architectures}. When @value{GDBN} is built like that, you can choose
19894 one of the available architectures with the @kbd{set architecture}
19898 @kindex set architecture
19899 @kindex show architecture
19900 @item set architecture @var{arch}
19901 This command sets the current target architecture to @var{arch}. The
19902 value of @var{arch} can be @code{"auto"}, in addition to one of the
19903 supported architectures.
19905 @item show architecture
19906 Show the current target architecture.
19908 @item set processor
19910 @kindex set processor
19911 @kindex show processor
19912 These are alias commands for, respectively, @code{set architecture}
19913 and @code{show architecture}.
19917 * Active Targets:: Active targets
19918 * Target Commands:: Commands for managing targets
19919 * Byte Order:: Choosing target byte order
19922 @node Active Targets
19923 @section Active Targets
19925 @cindex stacking targets
19926 @cindex active targets
19927 @cindex multiple targets
19929 There are multiple classes of targets such as: processes, executable files or
19930 recording sessions. Core files belong to the process class, making core file
19931 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19932 on multiple active targets, one in each class. This allows you to (for
19933 example) start a process and inspect its activity, while still having access to
19934 the executable file after the process finishes. Or if you start process
19935 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19936 presented a virtual layer of the recording target, while the process target
19937 remains stopped at the chronologically last point of the process execution.
19939 Use the @code{core-file} and @code{exec-file} commands to select a new core
19940 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19941 specify as a target a process that is already running, use the @code{attach}
19942 command (@pxref{Attach, ,Debugging an Already-running Process}).
19944 @node Target Commands
19945 @section Commands for Managing Targets
19948 @item target @var{type} @var{parameters}
19949 Connects the @value{GDBN} host environment to a target machine or
19950 process. A target is typically a protocol for talking to debugging
19951 facilities. You use the argument @var{type} to specify the type or
19952 protocol of the target machine.
19954 Further @var{parameters} are interpreted by the target protocol, but
19955 typically include things like device names or host names to connect
19956 with, process numbers, and baud rates.
19958 The @code{target} command does not repeat if you press @key{RET} again
19959 after executing the command.
19961 @kindex help target
19963 Displays the names of all targets available. To display targets
19964 currently selected, use either @code{info target} or @code{info files}
19965 (@pxref{Files, ,Commands to Specify Files}).
19967 @item help target @var{name}
19968 Describe a particular target, including any parameters necessary to
19971 @kindex set gnutarget
19972 @item set gnutarget @var{args}
19973 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19974 knows whether it is reading an @dfn{executable},
19975 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19976 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19977 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19980 @emph{Warning:} To specify a file format with @code{set gnutarget},
19981 you must know the actual BFD name.
19985 @xref{Files, , Commands to Specify Files}.
19987 @kindex show gnutarget
19988 @item show gnutarget
19989 Use the @code{show gnutarget} command to display what file format
19990 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19991 @value{GDBN} will determine the file format for each file automatically,
19992 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19995 @cindex common targets
19996 Here are some common targets (available, or not, depending on the GDB
20001 @item target exec @var{program}
20002 @cindex executable file target
20003 An executable file. @samp{target exec @var{program}} is the same as
20004 @samp{exec-file @var{program}}.
20006 @item target core @var{filename}
20007 @cindex core dump file target
20008 A core dump file. @samp{target core @var{filename}} is the same as
20009 @samp{core-file @var{filename}}.
20011 @item target remote @var{medium}
20012 @cindex remote target
20013 A remote system connected to @value{GDBN} via a serial line or network
20014 connection. This command tells @value{GDBN} to use its own remote
20015 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20017 For example, if you have a board connected to @file{/dev/ttya} on the
20018 machine running @value{GDBN}, you could say:
20021 target remote /dev/ttya
20024 @code{target remote} supports the @code{load} command. This is only
20025 useful if you have some other way of getting the stub to the target
20026 system, and you can put it somewhere in memory where it won't get
20027 clobbered by the download.
20029 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20030 @cindex built-in simulator target
20031 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20039 works; however, you cannot assume that a specific memory map, device
20040 drivers, or even basic I/O is available, although some simulators do
20041 provide these. For info about any processor-specific simulator details,
20042 see the appropriate section in @ref{Embedded Processors, ,Embedded
20045 @item target native
20046 @cindex native target
20047 Setup for local/native process debugging. Useful to make the
20048 @code{run} command spawn native processes (likewise @code{attach},
20049 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20050 (@pxref{set auto-connect-native-target}).
20054 Different targets are available on different configurations of @value{GDBN};
20055 your configuration may have more or fewer targets.
20057 Many remote targets require you to download the executable's code once
20058 you've successfully established a connection. You may wish to control
20059 various aspects of this process.
20064 @kindex set hash@r{, for remote monitors}
20065 @cindex hash mark while downloading
20066 This command controls whether a hash mark @samp{#} is displayed while
20067 downloading a file to the remote monitor. If on, a hash mark is
20068 displayed after each S-record is successfully downloaded to the
20072 @kindex show hash@r{, for remote monitors}
20073 Show the current status of displaying the hash mark.
20075 @item set debug monitor
20076 @kindex set debug monitor
20077 @cindex display remote monitor communications
20078 Enable or disable display of communications messages between
20079 @value{GDBN} and the remote monitor.
20081 @item show debug monitor
20082 @kindex show debug monitor
20083 Show the current status of displaying communications between
20084 @value{GDBN} and the remote monitor.
20089 @kindex load @var{filename} @var{offset}
20090 @item load @var{filename} @var{offset}
20092 Depending on what remote debugging facilities are configured into
20093 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20094 is meant to make @var{filename} (an executable) available for debugging
20095 on the remote system---by downloading, or dynamic linking, for example.
20096 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20097 the @code{add-symbol-file} command.
20099 If your @value{GDBN} does not have a @code{load} command, attempting to
20100 execute it gets the error message ``@code{You can't do that when your
20101 target is @dots{}}''
20103 The file is loaded at whatever address is specified in the executable.
20104 For some object file formats, you can specify the load address when you
20105 link the program; for other formats, like a.out, the object file format
20106 specifies a fixed address.
20107 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20109 It is also possible to tell @value{GDBN} to load the executable file at a
20110 specific offset described by the optional argument @var{offset}. When
20111 @var{offset} is provided, @var{filename} must also be provided.
20113 Depending on the remote side capabilities, @value{GDBN} may be able to
20114 load programs into flash memory.
20116 @code{load} does not repeat if you press @key{RET} again after using it.
20121 @kindex flash-erase
20123 @anchor{flash-erase}
20125 Erases all known flash memory regions on the target.
20130 @section Choosing Target Byte Order
20132 @cindex choosing target byte order
20133 @cindex target byte order
20135 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20136 offer the ability to run either big-endian or little-endian byte
20137 orders. Usually the executable or symbol will include a bit to
20138 designate the endian-ness, and you will not need to worry about
20139 which to use. However, you may still find it useful to adjust
20140 @value{GDBN}'s idea of processor endian-ness manually.
20144 @item set endian big
20145 Instruct @value{GDBN} to assume the target is big-endian.
20147 @item set endian little
20148 Instruct @value{GDBN} to assume the target is little-endian.
20150 @item set endian auto
20151 Instruct @value{GDBN} to use the byte order associated with the
20155 Display @value{GDBN}'s current idea of the target byte order.
20159 Note that these commands merely adjust interpretation of symbolic
20160 data on the host, and that they have absolutely no effect on the
20164 @node Remote Debugging
20165 @chapter Debugging Remote Programs
20166 @cindex remote debugging
20168 If you are trying to debug a program running on a machine that cannot run
20169 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20170 For example, you might use remote debugging on an operating system kernel,
20171 or on a small system which does not have a general purpose operating system
20172 powerful enough to run a full-featured debugger.
20174 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20175 to make this work with particular debugging targets. In addition,
20176 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20177 but not specific to any particular target system) which you can use if you
20178 write the remote stubs---the code that runs on the remote system to
20179 communicate with @value{GDBN}.
20181 Other remote targets may be available in your
20182 configuration of @value{GDBN}; use @code{help target} to list them.
20185 * Connecting:: Connecting to a remote target
20186 * File Transfer:: Sending files to a remote system
20187 * Server:: Using the gdbserver program
20188 * Remote Configuration:: Remote configuration
20189 * Remote Stub:: Implementing a remote stub
20193 @section Connecting to a Remote Target
20194 @cindex remote debugging, connecting
20195 @cindex @code{gdbserver}, connecting
20196 @cindex remote debugging, types of connections
20197 @cindex @code{gdbserver}, types of connections
20198 @cindex @code{gdbserver}, @code{target remote} mode
20199 @cindex @code{gdbserver}, @code{target extended-remote} mode
20201 This section describes how to connect to a remote target, including the
20202 types of connections and their differences, how to set up executable and
20203 symbol files on the host and target, and the commands used for
20204 connecting to and disconnecting from the remote target.
20206 @subsection Types of Remote Connections
20208 @value{GDBN} supports two types of remote connections, @code{target remote}
20209 mode and @code{target extended-remote} mode. Note that many remote targets
20210 support only @code{target remote} mode. There are several major
20211 differences between the two types of connections, enumerated here:
20215 @cindex remote debugging, detach and program exit
20216 @item Result of detach or program exit
20217 @strong{With target remote mode:} When the debugged program exits or you
20218 detach from it, @value{GDBN} disconnects from the target. When using
20219 @code{gdbserver}, @code{gdbserver} will exit.
20221 @strong{With target extended-remote mode:} When the debugged program exits or
20222 you detach from it, @value{GDBN} remains connected to the target, even
20223 though no program is running. You can rerun the program, attach to a
20224 running program, or use @code{monitor} commands specific to the target.
20226 When using @code{gdbserver} in this case, it does not exit unless it was
20227 invoked using the @option{--once} option. If the @option{--once} option
20228 was not used, you can ask @code{gdbserver} to exit using the
20229 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20231 @item Specifying the program to debug
20232 For both connection types you use the @code{file} command to specify the
20233 program on the host system. If you are using @code{gdbserver} there are
20234 some differences in how to specify the location of the program on the
20237 @strong{With target remote mode:} You must either specify the program to debug
20238 on the @code{gdbserver} command line or use the @option{--attach} option
20239 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20241 @cindex @option{--multi}, @code{gdbserver} option
20242 @strong{With target extended-remote mode:} You may specify the program to debug
20243 on the @code{gdbserver} command line, or you can load the program or attach
20244 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20246 @anchor{--multi Option in Types of Remote Connnections}
20247 You can start @code{gdbserver} without supplying an initial command to run
20248 or process ID to attach. To do this, use the @option{--multi} command line
20249 option. Then you can connect using @code{target extended-remote} and start
20250 the program you want to debug (see below for details on using the
20251 @code{run} command in this scenario). Note that the conditions under which
20252 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20253 (@code{target remote} or @code{target extended-remote}). The
20254 @option{--multi} option to @code{gdbserver} has no influence on that.
20256 @item The @code{run} command
20257 @strong{With target remote mode:} The @code{run} command is not
20258 supported. Once a connection has been established, you can use all
20259 the usual @value{GDBN} commands to examine and change data. The
20260 remote program is already running, so you can use commands like
20261 @kbd{step} and @kbd{continue}.
20263 @strong{With target extended-remote mode:} The @code{run} command is
20264 supported. The @code{run} command uses the value set by
20265 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20266 the program to run. Command line arguments are supported, except for
20267 wildcard expansion and I/O redirection (@pxref{Arguments}).
20269 If you specify the program to debug on the command line, then the
20270 @code{run} command is not required to start execution, and you can
20271 resume using commands like @kbd{step} and @kbd{continue} as with
20272 @code{target remote} mode.
20274 @anchor{Attaching in Types of Remote Connections}
20276 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20277 not supported. To attach to a running program using @code{gdbserver}, you
20278 must use the @option{--attach} option (@pxref{Running gdbserver}).
20280 @strong{With target extended-remote mode:} To attach to a running program,
20281 you may use the @code{attach} command after the connection has been
20282 established. If you are using @code{gdbserver}, you may also invoke
20283 @code{gdbserver} using the @option{--attach} option
20284 (@pxref{Running gdbserver}).
20288 @anchor{Host and target files}
20289 @subsection Host and Target Files
20290 @cindex remote debugging, symbol files
20291 @cindex symbol files, remote debugging
20293 @value{GDBN}, running on the host, needs access to symbol and debugging
20294 information for your program running on the target. This requires
20295 access to an unstripped copy of your program, and possibly any associated
20296 symbol files. Note that this section applies equally to both @code{target
20297 remote} mode and @code{target extended-remote} mode.
20299 Some remote targets (@pxref{qXfer executable filename read}, and
20300 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20301 the same connection used to communicate with @value{GDBN}. With such a
20302 target, if the remote program is unstripped, the only command you need is
20303 @code{target remote} (or @code{target extended-remote}).
20305 If the remote program is stripped, or the target does not support remote
20306 program file access, start up @value{GDBN} using the name of the local
20307 unstripped copy of your program as the first argument, or use the
20308 @code{file} command. Use @code{set sysroot} to specify the location (on
20309 the host) of target libraries (unless your @value{GDBN} was compiled with
20310 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20311 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20314 The symbol file and target libraries must exactly match the executable
20315 and libraries on the target, with one exception: the files on the host
20316 system should not be stripped, even if the files on the target system
20317 are. Mismatched or missing files will lead to confusing results
20318 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20319 files may also prevent @code{gdbserver} from debugging multi-threaded
20322 @subsection Remote Connection Commands
20323 @cindex remote connection commands
20324 @value{GDBN} can communicate with the target over a serial line, or
20325 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20326 each case, @value{GDBN} uses the same protocol for debugging your
20327 program; only the medium carrying the debugging packets varies. The
20328 @code{target remote} and @code{target extended-remote} commands
20329 establish a connection to the target. Both commands accept the same
20330 arguments, which indicate the medium to use:
20334 @item target remote @var{serial-device}
20335 @itemx target extended-remote @var{serial-device}
20336 @cindex serial line, @code{target remote}
20337 Use @var{serial-device} to communicate with the target. For example,
20338 to use a serial line connected to the device named @file{/dev/ttyb}:
20341 target remote /dev/ttyb
20344 If you're using a serial line, you may want to give @value{GDBN} the
20345 @samp{--baud} option, or use the @code{set serial baud} command
20346 (@pxref{Remote Configuration, set serial baud}) before the
20347 @code{target} command.
20349 @item target remote @code{@var{host}:@var{port}}
20350 @itemx target remote @code{tcp:@var{host}:@var{port}}
20351 @itemx target extended-remote @code{@var{host}:@var{port}}
20352 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20353 @cindex @acronym{TCP} port, @code{target remote}
20354 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20355 The @var{host} may be either a host name or a numeric @acronym{IP}
20356 address; @var{port} must be a decimal number. The @var{host} could be
20357 the target machine itself, if it is directly connected to the net, or
20358 it might be a terminal server which in turn has a serial line to the
20361 For example, to connect to port 2828 on a terminal server named
20365 target remote manyfarms:2828
20368 If your remote target is actually running on the same machine as your
20369 debugger session (e.g.@: a simulator for your target running on the
20370 same host), you can omit the hostname. For example, to connect to
20371 port 1234 on your local machine:
20374 target remote :1234
20378 Note that the colon is still required here.
20380 @item target remote @code{udp:@var{host}:@var{port}}
20381 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20382 @cindex @acronym{UDP} port, @code{target remote}
20383 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20384 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20387 target remote udp:manyfarms:2828
20390 When using a @acronym{UDP} connection for remote debugging, you should
20391 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20392 can silently drop packets on busy or unreliable networks, which will
20393 cause havoc with your debugging session.
20395 @item target remote | @var{command}
20396 @itemx target extended-remote | @var{command}
20397 @cindex pipe, @code{target remote} to
20398 Run @var{command} in the background and communicate with it using a
20399 pipe. The @var{command} is a shell command, to be parsed and expanded
20400 by the system's command shell, @code{/bin/sh}; it should expect remote
20401 protocol packets on its standard input, and send replies on its
20402 standard output. You could use this to run a stand-alone simulator
20403 that speaks the remote debugging protocol, to make net connections
20404 using programs like @code{ssh}, or for other similar tricks.
20406 If @var{command} closes its standard output (perhaps by exiting),
20407 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20408 program has already exited, this will have no effect.)
20412 @cindex interrupting remote programs
20413 @cindex remote programs, interrupting
20414 Whenever @value{GDBN} is waiting for the remote program, if you type the
20415 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20416 program. This may or may not succeed, depending in part on the hardware
20417 and the serial drivers the remote system uses. If you type the
20418 interrupt character once again, @value{GDBN} displays this prompt:
20421 Interrupted while waiting for the program.
20422 Give up (and stop debugging it)? (y or n)
20425 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20426 the remote debugging session. (If you decide you want to try again later,
20427 you can use @kbd{target remote} again to connect once more.) If you type
20428 @kbd{n}, @value{GDBN} goes back to waiting.
20430 In @code{target extended-remote} mode, typing @kbd{n} will leave
20431 @value{GDBN} connected to the target.
20434 @kindex detach (remote)
20436 When you have finished debugging the remote program, you can use the
20437 @code{detach} command to release it from @value{GDBN} control.
20438 Detaching from the target normally resumes its execution, but the results
20439 will depend on your particular remote stub. After the @code{detach}
20440 command in @code{target remote} mode, @value{GDBN} is free to connect to
20441 another target. In @code{target extended-remote} mode, @value{GDBN} is
20442 still connected to the target.
20446 The @code{disconnect} command closes the connection to the target, and
20447 the target is generally not resumed. It will wait for @value{GDBN}
20448 (this instance or another one) to connect and continue debugging. After
20449 the @code{disconnect} command, @value{GDBN} is again free to connect to
20452 @cindex send command to remote monitor
20453 @cindex extend @value{GDBN} for remote targets
20454 @cindex add new commands for external monitor
20456 @item monitor @var{cmd}
20457 This command allows you to send arbitrary commands directly to the
20458 remote monitor. Since @value{GDBN} doesn't care about the commands it
20459 sends like this, this command is the way to extend @value{GDBN}---you
20460 can add new commands that only the external monitor will understand
20464 @node File Transfer
20465 @section Sending files to a remote system
20466 @cindex remote target, file transfer
20467 @cindex file transfer
20468 @cindex sending files to remote systems
20470 Some remote targets offer the ability to transfer files over the same
20471 connection used to communicate with @value{GDBN}. This is convenient
20472 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20473 running @code{gdbserver} over a network interface. For other targets,
20474 e.g.@: embedded devices with only a single serial port, this may be
20475 the only way to upload or download files.
20477 Not all remote targets support these commands.
20481 @item remote put @var{hostfile} @var{targetfile}
20482 Copy file @var{hostfile} from the host system (the machine running
20483 @value{GDBN}) to @var{targetfile} on the target system.
20486 @item remote get @var{targetfile} @var{hostfile}
20487 Copy file @var{targetfile} from the target system to @var{hostfile}
20488 on the host system.
20490 @kindex remote delete
20491 @item remote delete @var{targetfile}
20492 Delete @var{targetfile} from the target system.
20497 @section Using the @code{gdbserver} Program
20500 @cindex remote connection without stubs
20501 @code{gdbserver} is a control program for Unix-like systems, which
20502 allows you to connect your program with a remote @value{GDBN} via
20503 @code{target remote} or @code{target extended-remote}---but without
20504 linking in the usual debugging stub.
20506 @code{gdbserver} is not a complete replacement for the debugging stubs,
20507 because it requires essentially the same operating-system facilities
20508 that @value{GDBN} itself does. In fact, a system that can run
20509 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20510 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20511 because it is a much smaller program than @value{GDBN} itself. It is
20512 also easier to port than all of @value{GDBN}, so you may be able to get
20513 started more quickly on a new system by using @code{gdbserver}.
20514 Finally, if you develop code for real-time systems, you may find that
20515 the tradeoffs involved in real-time operation make it more convenient to
20516 do as much development work as possible on another system, for example
20517 by cross-compiling. You can use @code{gdbserver} to make a similar
20518 choice for debugging.
20520 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20521 or a TCP connection, using the standard @value{GDBN} remote serial
20525 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20526 Do not run @code{gdbserver} connected to any public network; a
20527 @value{GDBN} connection to @code{gdbserver} provides access to the
20528 target system with the same privileges as the user running
20532 @anchor{Running gdbserver}
20533 @subsection Running @code{gdbserver}
20534 @cindex arguments, to @code{gdbserver}
20535 @cindex @code{gdbserver}, command-line arguments
20537 Run @code{gdbserver} on the target system. You need a copy of the
20538 program you want to debug, including any libraries it requires.
20539 @code{gdbserver} does not need your program's symbol table, so you can
20540 strip the program if necessary to save space. @value{GDBN} on the host
20541 system does all the symbol handling.
20543 To use the server, you must tell it how to communicate with @value{GDBN};
20544 the name of your program; and the arguments for your program. The usual
20548 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20551 @var{comm} is either a device name (to use a serial line), or a TCP
20552 hostname and portnumber, or @code{-} or @code{stdio} to use
20553 stdin/stdout of @code{gdbserver}.
20554 For example, to debug Emacs with the argument
20555 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20559 target> gdbserver /dev/com1 emacs foo.txt
20562 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20565 To use a TCP connection instead of a serial line:
20568 target> gdbserver host:2345 emacs foo.txt
20571 The only difference from the previous example is the first argument,
20572 specifying that you are communicating with the host @value{GDBN} via
20573 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20574 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20575 (Currently, the @samp{host} part is ignored.) You can choose any number
20576 you want for the port number as long as it does not conflict with any
20577 TCP ports already in use on the target system (for example, @code{23} is
20578 reserved for @code{telnet}).@footnote{If you choose a port number that
20579 conflicts with another service, @code{gdbserver} prints an error message
20580 and exits.} You must use the same port number with the host @value{GDBN}
20581 @code{target remote} command.
20583 The @code{stdio} connection is useful when starting @code{gdbserver}
20587 (gdb) target remote | ssh -T hostname gdbserver - hello
20590 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20591 and we don't want escape-character handling. Ssh does this by default when
20592 a command is provided, the flag is provided to make it explicit.
20593 You could elide it if you want to.
20595 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20596 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20597 display through a pipe connected to gdbserver.
20598 Both @code{stdout} and @code{stderr} use the same pipe.
20600 @anchor{Attaching to a program}
20601 @subsubsection Attaching to a Running Program
20602 @cindex attach to a program, @code{gdbserver}
20603 @cindex @option{--attach}, @code{gdbserver} option
20605 On some targets, @code{gdbserver} can also attach to running programs.
20606 This is accomplished via the @code{--attach} argument. The syntax is:
20609 target> gdbserver --attach @var{comm} @var{pid}
20612 @var{pid} is the process ID of a currently running process. It isn't
20613 necessary to point @code{gdbserver} at a binary for the running process.
20615 In @code{target extended-remote} mode, you can also attach using the
20616 @value{GDBN} attach command
20617 (@pxref{Attaching in Types of Remote Connections}).
20620 You can debug processes by name instead of process ID if your target has the
20621 @code{pidof} utility:
20624 target> gdbserver --attach @var{comm} `pidof @var{program}`
20627 In case more than one copy of @var{program} is running, or @var{program}
20628 has multiple threads, most versions of @code{pidof} support the
20629 @code{-s} option to only return the first process ID.
20631 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20633 This section applies only when @code{gdbserver} is run to listen on a TCP
20636 @code{gdbserver} normally terminates after all of its debugged processes have
20637 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20638 extended-remote}, @code{gdbserver} stays running even with no processes left.
20639 @value{GDBN} normally terminates the spawned debugged process on its exit,
20640 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20641 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20642 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20643 stays running even in the @kbd{target remote} mode.
20645 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20646 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20647 completeness, at most one @value{GDBN} can be connected at a time.
20649 @cindex @option{--once}, @code{gdbserver} option
20650 By default, @code{gdbserver} keeps the listening TCP port open, so that
20651 subsequent connections are possible. However, if you start @code{gdbserver}
20652 with the @option{--once} option, it will stop listening for any further
20653 connection attempts after connecting to the first @value{GDBN} session. This
20654 means no further connections to @code{gdbserver} will be possible after the
20655 first one. It also means @code{gdbserver} will terminate after the first
20656 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20657 connections and even in the @kbd{target extended-remote} mode. The
20658 @option{--once} option allows reusing the same port number for connecting to
20659 multiple instances of @code{gdbserver} running on the same host, since each
20660 instance closes its port after the first connection.
20662 @anchor{Other Command-Line Arguments for gdbserver}
20663 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20665 You can use the @option{--multi} option to start @code{gdbserver} without
20666 specifying a program to debug or a process to attach to. Then you can
20667 attach in @code{target extended-remote} mode and run or attach to a
20668 program. For more information,
20669 @pxref{--multi Option in Types of Remote Connnections}.
20671 @cindex @option{--debug}, @code{gdbserver} option
20672 The @option{--debug} option tells @code{gdbserver} to display extra
20673 status information about the debugging process.
20674 @cindex @option{--remote-debug}, @code{gdbserver} option
20675 The @option{--remote-debug} option tells @code{gdbserver} to display
20676 remote protocol debug output. These options are intended for
20677 @code{gdbserver} development and for bug reports to the developers.
20679 @cindex @option{--debug-format}, @code{gdbserver} option
20680 The @option{--debug-format=option1[,option2,...]} option tells
20681 @code{gdbserver} to include additional information in each output.
20682 Possible options are:
20686 Turn off all extra information in debugging output.
20688 Turn on all extra information in debugging output.
20690 Include a timestamp in each line of debugging output.
20693 Options are processed in order. Thus, for example, if @option{none}
20694 appears last then no additional information is added to debugging output.
20696 @cindex @option{--wrapper}, @code{gdbserver} option
20697 The @option{--wrapper} option specifies a wrapper to launch programs
20698 for debugging. The option should be followed by the name of the
20699 wrapper, then any command-line arguments to pass to the wrapper, then
20700 @kbd{--} indicating the end of the wrapper arguments.
20702 @code{gdbserver} runs the specified wrapper program with a combined
20703 command line including the wrapper arguments, then the name of the
20704 program to debug, then any arguments to the program. The wrapper
20705 runs until it executes your program, and then @value{GDBN} gains control.
20707 You can use any program that eventually calls @code{execve} with
20708 its arguments as a wrapper. Several standard Unix utilities do
20709 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20710 with @code{exec "$@@"} will also work.
20712 For example, you can use @code{env} to pass an environment variable to
20713 the debugged program, without setting the variable in @code{gdbserver}'s
20717 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20720 @cindex @option{--selftest}
20721 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20724 $ gdbserver --selftest
20725 Ran 2 unit tests, 0 failed
20728 These tests are disabled in release.
20729 @subsection Connecting to @code{gdbserver}
20731 The basic procedure for connecting to the remote target is:
20735 Run @value{GDBN} on the host system.
20738 Make sure you have the necessary symbol files
20739 (@pxref{Host and target files}).
20740 Load symbols for your application using the @code{file} command before you
20741 connect. Use @code{set sysroot} to locate target libraries (unless your
20742 @value{GDBN} was compiled with the correct sysroot using
20743 @code{--with-sysroot}).
20746 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20747 For TCP connections, you must start up @code{gdbserver} prior to using
20748 the @code{target} command. Otherwise you may get an error whose
20749 text depends on the host system, but which usually looks something like
20750 @samp{Connection refused}. Don't use the @code{load}
20751 command in @value{GDBN} when using @code{target remote} mode, since the
20752 program is already on the target.
20756 @anchor{Monitor Commands for gdbserver}
20757 @subsection Monitor Commands for @code{gdbserver}
20758 @cindex monitor commands, for @code{gdbserver}
20760 During a @value{GDBN} session using @code{gdbserver}, you can use the
20761 @code{monitor} command to send special requests to @code{gdbserver}.
20762 Here are the available commands.
20766 List the available monitor commands.
20768 @item monitor set debug 0
20769 @itemx monitor set debug 1
20770 Disable or enable general debugging messages.
20772 @item monitor set remote-debug 0
20773 @itemx monitor set remote-debug 1
20774 Disable or enable specific debugging messages associated with the remote
20775 protocol (@pxref{Remote Protocol}).
20777 @item monitor set debug-format option1@r{[},option2,...@r{]}
20778 Specify additional text to add to debugging messages.
20779 Possible options are:
20783 Turn off all extra information in debugging output.
20785 Turn on all extra information in debugging output.
20787 Include a timestamp in each line of debugging output.
20790 Options are processed in order. Thus, for example, if @option{none}
20791 appears last then no additional information is added to debugging output.
20793 @item monitor set libthread-db-search-path [PATH]
20794 @cindex gdbserver, search path for @code{libthread_db}
20795 When this command is issued, @var{path} is a colon-separated list of
20796 directories to search for @code{libthread_db} (@pxref{Threads,,set
20797 libthread-db-search-path}). If you omit @var{path},
20798 @samp{libthread-db-search-path} will be reset to its default value.
20800 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20801 not supported in @code{gdbserver}.
20804 Tell gdbserver to exit immediately. This command should be followed by
20805 @code{disconnect} to close the debugging session. @code{gdbserver} will
20806 detach from any attached processes and kill any processes it created.
20807 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20808 of a multi-process mode debug session.
20812 @subsection Tracepoints support in @code{gdbserver}
20813 @cindex tracepoints support in @code{gdbserver}
20815 On some targets, @code{gdbserver} supports tracepoints, fast
20816 tracepoints and static tracepoints.
20818 For fast or static tracepoints to work, a special library called the
20819 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20820 This library is built and distributed as an integral part of
20821 @code{gdbserver}. In addition, support for static tracepoints
20822 requires building the in-process agent library with static tracepoints
20823 support. At present, the UST (LTTng Userspace Tracer,
20824 @url{http://lttng.org/ust}) tracing engine is supported. This support
20825 is automatically available if UST development headers are found in the
20826 standard include path when @code{gdbserver} is built, or if
20827 @code{gdbserver} was explicitly configured using @option{--with-ust}
20828 to point at such headers. You can explicitly disable the support
20829 using @option{--with-ust=no}.
20831 There are several ways to load the in-process agent in your program:
20834 @item Specifying it as dependency at link time
20836 You can link your program dynamically with the in-process agent
20837 library. On most systems, this is accomplished by adding
20838 @code{-linproctrace} to the link command.
20840 @item Using the system's preloading mechanisms
20842 You can force loading the in-process agent at startup time by using
20843 your system's support for preloading shared libraries. Many Unixes
20844 support the concept of preloading user defined libraries. In most
20845 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20846 in the environment. See also the description of @code{gdbserver}'s
20847 @option{--wrapper} command line option.
20849 @item Using @value{GDBN} to force loading the agent at run time
20851 On some systems, you can force the inferior to load a shared library,
20852 by calling a dynamic loader function in the inferior that takes care
20853 of dynamically looking up and loading a shared library. On most Unix
20854 systems, the function is @code{dlopen}. You'll use the @code{call}
20855 command for that. For example:
20858 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20861 Note that on most Unix systems, for the @code{dlopen} function to be
20862 available, the program needs to be linked with @code{-ldl}.
20865 On systems that have a userspace dynamic loader, like most Unix
20866 systems, when you connect to @code{gdbserver} using @code{target
20867 remote}, you'll find that the program is stopped at the dynamic
20868 loader's entry point, and no shared library has been loaded in the
20869 program's address space yet, including the in-process agent. In that
20870 case, before being able to use any of the fast or static tracepoints
20871 features, you need to let the loader run and load the shared
20872 libraries. The simplest way to do that is to run the program to the
20873 main procedure. E.g., if debugging a C or C@t{++} program, start
20874 @code{gdbserver} like so:
20877 $ gdbserver :9999 myprogram
20880 Start GDB and connect to @code{gdbserver} like so, and run to main:
20884 (@value{GDBP}) target remote myhost:9999
20885 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20886 (@value{GDBP}) b main
20887 (@value{GDBP}) continue
20890 The in-process tracing agent library should now be loaded into the
20891 process; you can confirm it with the @code{info sharedlibrary}
20892 command, which will list @file{libinproctrace.so} as loaded in the
20893 process. You are now ready to install fast tracepoints, list static
20894 tracepoint markers, probe static tracepoints markers, and start
20897 @node Remote Configuration
20898 @section Remote Configuration
20901 @kindex show remote
20902 This section documents the configuration options available when
20903 debugging remote programs. For the options related to the File I/O
20904 extensions of the remote protocol, see @ref{system,
20905 system-call-allowed}.
20908 @item set remoteaddresssize @var{bits}
20909 @cindex address size for remote targets
20910 @cindex bits in remote address
20911 Set the maximum size of address in a memory packet to the specified
20912 number of bits. @value{GDBN} will mask off the address bits above
20913 that number, when it passes addresses to the remote target. The
20914 default value is the number of bits in the target's address.
20916 @item show remoteaddresssize
20917 Show the current value of remote address size in bits.
20919 @item set serial baud @var{n}
20920 @cindex baud rate for remote targets
20921 Set the baud rate for the remote serial I/O to @var{n} baud. The
20922 value is used to set the speed of the serial port used for debugging
20925 @item show serial baud
20926 Show the current speed of the remote connection.
20928 @item set serial parity @var{parity}
20929 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20930 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20932 @item show serial parity
20933 Show the current parity of the serial port.
20935 @item set remotebreak
20936 @cindex interrupt remote programs
20937 @cindex BREAK signal instead of Ctrl-C
20938 @anchor{set remotebreak}
20939 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20940 when you type @kbd{Ctrl-c} to interrupt the program running
20941 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20942 character instead. The default is off, since most remote systems
20943 expect to see @samp{Ctrl-C} as the interrupt signal.
20945 @item show remotebreak
20946 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20947 interrupt the remote program.
20949 @item set remoteflow on
20950 @itemx set remoteflow off
20951 @kindex set remoteflow
20952 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20953 on the serial port used to communicate to the remote target.
20955 @item show remoteflow
20956 @kindex show remoteflow
20957 Show the current setting of hardware flow control.
20959 @item set remotelogbase @var{base}
20960 Set the base (a.k.a.@: radix) of logging serial protocol
20961 communications to @var{base}. Supported values of @var{base} are:
20962 @code{ascii}, @code{octal}, and @code{hex}. The default is
20965 @item show remotelogbase
20966 Show the current setting of the radix for logging remote serial
20969 @item set remotelogfile @var{file}
20970 @cindex record serial communications on file
20971 Record remote serial communications on the named @var{file}. The
20972 default is not to record at all.
20974 @item show remotelogfile.
20975 Show the current setting of the file name on which to record the
20976 serial communications.
20978 @item set remotetimeout @var{num}
20979 @cindex timeout for serial communications
20980 @cindex remote timeout
20981 Set the timeout limit to wait for the remote target to respond to
20982 @var{num} seconds. The default is 2 seconds.
20984 @item show remotetimeout
20985 Show the current number of seconds to wait for the remote target
20988 @cindex limit hardware breakpoints and watchpoints
20989 @cindex remote target, limit break- and watchpoints
20990 @anchor{set remote hardware-watchpoint-limit}
20991 @anchor{set remote hardware-breakpoint-limit}
20992 @item set remote hardware-watchpoint-limit @var{limit}
20993 @itemx set remote hardware-breakpoint-limit @var{limit}
20994 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20995 watchpoints. A limit of -1, the default, is treated as unlimited.
20997 @cindex limit hardware watchpoints length
20998 @cindex remote target, limit watchpoints length
20999 @anchor{set remote hardware-watchpoint-length-limit}
21000 @item set remote hardware-watchpoint-length-limit @var{limit}
21001 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
21002 a remote hardware watchpoint. A limit of -1, the default, is treated
21005 @item show remote hardware-watchpoint-length-limit
21006 Show the current limit (in bytes) of the maximum length of
21007 a remote hardware watchpoint.
21009 @item set remote exec-file @var{filename}
21010 @itemx show remote exec-file
21011 @anchor{set remote exec-file}
21012 @cindex executable file, for remote target
21013 Select the file used for @code{run} with @code{target
21014 extended-remote}. This should be set to a filename valid on the
21015 target system. If it is not set, the target will use a default
21016 filename (e.g.@: the last program run).
21018 @item set remote interrupt-sequence
21019 @cindex interrupt remote programs
21020 @cindex select Ctrl-C, BREAK or BREAK-g
21021 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21022 @samp{BREAK-g} as the
21023 sequence to the remote target in order to interrupt the execution.
21024 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21025 is high level of serial line for some certain time.
21026 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21027 It is @code{BREAK} signal followed by character @code{g}.
21029 @item show interrupt-sequence
21030 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21031 is sent by @value{GDBN} to interrupt the remote program.
21032 @code{BREAK-g} is BREAK signal followed by @code{g} and
21033 also known as Magic SysRq g.
21035 @item set remote interrupt-on-connect
21036 @cindex send interrupt-sequence on start
21037 Specify whether interrupt-sequence is sent to remote target when
21038 @value{GDBN} connects to it. This is mostly needed when you debug
21039 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21040 which is known as Magic SysRq g in order to connect @value{GDBN}.
21042 @item show interrupt-on-connect
21043 Show whether interrupt-sequence is sent
21044 to remote target when @value{GDBN} connects to it.
21048 @item set tcp auto-retry on
21049 @cindex auto-retry, for remote TCP target
21050 Enable auto-retry for remote TCP connections. This is useful if the remote
21051 debugging agent is launched in parallel with @value{GDBN}; there is a race
21052 condition because the agent may not become ready to accept the connection
21053 before @value{GDBN} attempts to connect. When auto-retry is
21054 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21055 to establish the connection using the timeout specified by
21056 @code{set tcp connect-timeout}.
21058 @item set tcp auto-retry off
21059 Do not auto-retry failed TCP connections.
21061 @item show tcp auto-retry
21062 Show the current auto-retry setting.
21064 @item set tcp connect-timeout @var{seconds}
21065 @itemx set tcp connect-timeout unlimited
21066 @cindex connection timeout, for remote TCP target
21067 @cindex timeout, for remote target connection
21068 Set the timeout for establishing a TCP connection to the remote target to
21069 @var{seconds}. The timeout affects both polling to retry failed connections
21070 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21071 that are merely slow to complete, and represents an approximate cumulative
21072 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21073 @value{GDBN} will keep attempting to establish a connection forever,
21074 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21076 @item show tcp connect-timeout
21077 Show the current connection timeout setting.
21080 @cindex remote packets, enabling and disabling
21081 The @value{GDBN} remote protocol autodetects the packets supported by
21082 your debugging stub. If you need to override the autodetection, you
21083 can use these commands to enable or disable individual packets. Each
21084 packet can be set to @samp{on} (the remote target supports this
21085 packet), @samp{off} (the remote target does not support this packet),
21086 or @samp{auto} (detect remote target support for this packet). They
21087 all default to @samp{auto}. For more information about each packet,
21088 see @ref{Remote Protocol}.
21090 During normal use, you should not have to use any of these commands.
21091 If you do, that may be a bug in your remote debugging stub, or a bug
21092 in @value{GDBN}. You may want to report the problem to the
21093 @value{GDBN} developers.
21095 For each packet @var{name}, the command to enable or disable the
21096 packet is @code{set remote @var{name}-packet}. The available settings
21099 @multitable @columnfractions 0.28 0.32 0.25
21102 @tab Related Features
21104 @item @code{fetch-register}
21106 @tab @code{info registers}
21108 @item @code{set-register}
21112 @item @code{binary-download}
21114 @tab @code{load}, @code{set}
21116 @item @code{read-aux-vector}
21117 @tab @code{qXfer:auxv:read}
21118 @tab @code{info auxv}
21120 @item @code{symbol-lookup}
21121 @tab @code{qSymbol}
21122 @tab Detecting multiple threads
21124 @item @code{attach}
21125 @tab @code{vAttach}
21128 @item @code{verbose-resume}
21130 @tab Stepping or resuming multiple threads
21136 @item @code{software-breakpoint}
21140 @item @code{hardware-breakpoint}
21144 @item @code{write-watchpoint}
21148 @item @code{read-watchpoint}
21152 @item @code{access-watchpoint}
21156 @item @code{pid-to-exec-file}
21157 @tab @code{qXfer:exec-file:read}
21158 @tab @code{attach}, @code{run}
21160 @item @code{target-features}
21161 @tab @code{qXfer:features:read}
21162 @tab @code{set architecture}
21164 @item @code{library-info}
21165 @tab @code{qXfer:libraries:read}
21166 @tab @code{info sharedlibrary}
21168 @item @code{memory-map}
21169 @tab @code{qXfer:memory-map:read}
21170 @tab @code{info mem}
21172 @item @code{read-sdata-object}
21173 @tab @code{qXfer:sdata:read}
21174 @tab @code{print $_sdata}
21176 @item @code{read-spu-object}
21177 @tab @code{qXfer:spu:read}
21178 @tab @code{info spu}
21180 @item @code{write-spu-object}
21181 @tab @code{qXfer:spu:write}
21182 @tab @code{info spu}
21184 @item @code{read-siginfo-object}
21185 @tab @code{qXfer:siginfo:read}
21186 @tab @code{print $_siginfo}
21188 @item @code{write-siginfo-object}
21189 @tab @code{qXfer:siginfo:write}
21190 @tab @code{set $_siginfo}
21192 @item @code{threads}
21193 @tab @code{qXfer:threads:read}
21194 @tab @code{info threads}
21196 @item @code{get-thread-local-@*storage-address}
21197 @tab @code{qGetTLSAddr}
21198 @tab Displaying @code{__thread} variables
21200 @item @code{get-thread-information-block-address}
21201 @tab @code{qGetTIBAddr}
21202 @tab Display MS-Windows Thread Information Block.
21204 @item @code{search-memory}
21205 @tab @code{qSearch:memory}
21208 @item @code{supported-packets}
21209 @tab @code{qSupported}
21210 @tab Remote communications parameters
21212 @item @code{catch-syscalls}
21213 @tab @code{QCatchSyscalls}
21214 @tab @code{catch syscall}
21216 @item @code{pass-signals}
21217 @tab @code{QPassSignals}
21218 @tab @code{handle @var{signal}}
21220 @item @code{program-signals}
21221 @tab @code{QProgramSignals}
21222 @tab @code{handle @var{signal}}
21224 @item @code{hostio-close-packet}
21225 @tab @code{vFile:close}
21226 @tab @code{remote get}, @code{remote put}
21228 @item @code{hostio-open-packet}
21229 @tab @code{vFile:open}
21230 @tab @code{remote get}, @code{remote put}
21232 @item @code{hostio-pread-packet}
21233 @tab @code{vFile:pread}
21234 @tab @code{remote get}, @code{remote put}
21236 @item @code{hostio-pwrite-packet}
21237 @tab @code{vFile:pwrite}
21238 @tab @code{remote get}, @code{remote put}
21240 @item @code{hostio-unlink-packet}
21241 @tab @code{vFile:unlink}
21242 @tab @code{remote delete}
21244 @item @code{hostio-readlink-packet}
21245 @tab @code{vFile:readlink}
21248 @item @code{hostio-fstat-packet}
21249 @tab @code{vFile:fstat}
21252 @item @code{hostio-setfs-packet}
21253 @tab @code{vFile:setfs}
21256 @item @code{noack-packet}
21257 @tab @code{QStartNoAckMode}
21258 @tab Packet acknowledgment
21260 @item @code{osdata}
21261 @tab @code{qXfer:osdata:read}
21262 @tab @code{info os}
21264 @item @code{query-attached}
21265 @tab @code{qAttached}
21266 @tab Querying remote process attach state.
21268 @item @code{trace-buffer-size}
21269 @tab @code{QTBuffer:size}
21270 @tab @code{set trace-buffer-size}
21272 @item @code{trace-status}
21273 @tab @code{qTStatus}
21274 @tab @code{tstatus}
21276 @item @code{traceframe-info}
21277 @tab @code{qXfer:traceframe-info:read}
21278 @tab Traceframe info
21280 @item @code{install-in-trace}
21281 @tab @code{InstallInTrace}
21282 @tab Install tracepoint in tracing
21284 @item @code{disable-randomization}
21285 @tab @code{QDisableRandomization}
21286 @tab @code{set disable-randomization}
21288 @item @code{startup-with-shell}
21289 @tab @code{QStartupWithShell}
21290 @tab @code{set startup-with-shell}
21292 @item @code{environment-hex-encoded}
21293 @tab @code{QEnvironmentHexEncoded}
21294 @tab @code{set environment}
21296 @item @code{environment-unset}
21297 @tab @code{QEnvironmentUnset}
21298 @tab @code{unset environment}
21300 @item @code{environment-reset}
21301 @tab @code{QEnvironmentReset}
21302 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21304 @item @code{set-working-dir}
21305 @tab @code{QSetWorkingDir}
21306 @tab @code{set cwd}
21308 @item @code{conditional-breakpoints-packet}
21309 @tab @code{Z0 and Z1}
21310 @tab @code{Support for target-side breakpoint condition evaluation}
21312 @item @code{multiprocess-extensions}
21313 @tab @code{multiprocess extensions}
21314 @tab Debug multiple processes and remote process PID awareness
21316 @item @code{swbreak-feature}
21317 @tab @code{swbreak stop reason}
21320 @item @code{hwbreak-feature}
21321 @tab @code{hwbreak stop reason}
21324 @item @code{fork-event-feature}
21325 @tab @code{fork stop reason}
21328 @item @code{vfork-event-feature}
21329 @tab @code{vfork stop reason}
21332 @item @code{exec-event-feature}
21333 @tab @code{exec stop reason}
21336 @item @code{thread-events}
21337 @tab @code{QThreadEvents}
21338 @tab Tracking thread lifetime.
21340 @item @code{no-resumed-stop-reply}
21341 @tab @code{no resumed thread left stop reply}
21342 @tab Tracking thread lifetime.
21347 @section Implementing a Remote Stub
21349 @cindex debugging stub, example
21350 @cindex remote stub, example
21351 @cindex stub example, remote debugging
21352 The stub files provided with @value{GDBN} implement the target side of the
21353 communication protocol, and the @value{GDBN} side is implemented in the
21354 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21355 these subroutines to communicate, and ignore the details. (If you're
21356 implementing your own stub file, you can still ignore the details: start
21357 with one of the existing stub files. @file{sparc-stub.c} is the best
21358 organized, and therefore the easiest to read.)
21360 @cindex remote serial debugging, overview
21361 To debug a program running on another machine (the debugging
21362 @dfn{target} machine), you must first arrange for all the usual
21363 prerequisites for the program to run by itself. For example, for a C
21368 A startup routine to set up the C runtime environment; these usually
21369 have a name like @file{crt0}. The startup routine may be supplied by
21370 your hardware supplier, or you may have to write your own.
21373 A C subroutine library to support your program's
21374 subroutine calls, notably managing input and output.
21377 A way of getting your program to the other machine---for example, a
21378 download program. These are often supplied by the hardware
21379 manufacturer, but you may have to write your own from hardware
21383 The next step is to arrange for your program to use a serial port to
21384 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21385 machine). In general terms, the scheme looks like this:
21389 @value{GDBN} already understands how to use this protocol; when everything
21390 else is set up, you can simply use the @samp{target remote} command
21391 (@pxref{Targets,,Specifying a Debugging Target}).
21393 @item On the target,
21394 you must link with your program a few special-purpose subroutines that
21395 implement the @value{GDBN} remote serial protocol. The file containing these
21396 subroutines is called a @dfn{debugging stub}.
21398 On certain remote targets, you can use an auxiliary program
21399 @code{gdbserver} instead of linking a stub into your program.
21400 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21403 The debugging stub is specific to the architecture of the remote
21404 machine; for example, use @file{sparc-stub.c} to debug programs on
21407 @cindex remote serial stub list
21408 These working remote stubs are distributed with @value{GDBN}:
21413 @cindex @file{i386-stub.c}
21416 For Intel 386 and compatible architectures.
21419 @cindex @file{m68k-stub.c}
21420 @cindex Motorola 680x0
21422 For Motorola 680x0 architectures.
21425 @cindex @file{sh-stub.c}
21428 For Renesas SH architectures.
21431 @cindex @file{sparc-stub.c}
21433 For @sc{sparc} architectures.
21435 @item sparcl-stub.c
21436 @cindex @file{sparcl-stub.c}
21439 For Fujitsu @sc{sparclite} architectures.
21443 The @file{README} file in the @value{GDBN} distribution may list other
21444 recently added stubs.
21447 * Stub Contents:: What the stub can do for you
21448 * Bootstrapping:: What you must do for the stub
21449 * Debug Session:: Putting it all together
21452 @node Stub Contents
21453 @subsection What the Stub Can Do for You
21455 @cindex remote serial stub
21456 The debugging stub for your architecture supplies these three
21460 @item set_debug_traps
21461 @findex set_debug_traps
21462 @cindex remote serial stub, initialization
21463 This routine arranges for @code{handle_exception} to run when your
21464 program stops. You must call this subroutine explicitly in your
21465 program's startup code.
21467 @item handle_exception
21468 @findex handle_exception
21469 @cindex remote serial stub, main routine
21470 This is the central workhorse, but your program never calls it
21471 explicitly---the setup code arranges for @code{handle_exception} to
21472 run when a trap is triggered.
21474 @code{handle_exception} takes control when your program stops during
21475 execution (for example, on a breakpoint), and mediates communications
21476 with @value{GDBN} on the host machine. This is where the communications
21477 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21478 representative on the target machine. It begins by sending summary
21479 information on the state of your program, then continues to execute,
21480 retrieving and transmitting any information @value{GDBN} needs, until you
21481 execute a @value{GDBN} command that makes your program resume; at that point,
21482 @code{handle_exception} returns control to your own code on the target
21486 @cindex @code{breakpoint} subroutine, remote
21487 Use this auxiliary subroutine to make your program contain a
21488 breakpoint. Depending on the particular situation, this may be the only
21489 way for @value{GDBN} to get control. For instance, if your target
21490 machine has some sort of interrupt button, you won't need to call this;
21491 pressing the interrupt button transfers control to
21492 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21493 simply receiving characters on the serial port may also trigger a trap;
21494 again, in that situation, you don't need to call @code{breakpoint} from
21495 your own program---simply running @samp{target remote} from the host
21496 @value{GDBN} session gets control.
21498 Call @code{breakpoint} if none of these is true, or if you simply want
21499 to make certain your program stops at a predetermined point for the
21500 start of your debugging session.
21503 @node Bootstrapping
21504 @subsection What You Must Do for the Stub
21506 @cindex remote stub, support routines
21507 The debugging stubs that come with @value{GDBN} are set up for a particular
21508 chip architecture, but they have no information about the rest of your
21509 debugging target machine.
21511 First of all you need to tell the stub how to communicate with the
21515 @item int getDebugChar()
21516 @findex getDebugChar
21517 Write this subroutine to read a single character from the serial port.
21518 It may be identical to @code{getchar} for your target system; a
21519 different name is used to allow you to distinguish the two if you wish.
21521 @item void putDebugChar(int)
21522 @findex putDebugChar
21523 Write this subroutine to write a single character to the serial port.
21524 It may be identical to @code{putchar} for your target system; a
21525 different name is used to allow you to distinguish the two if you wish.
21528 @cindex control C, and remote debugging
21529 @cindex interrupting remote targets
21530 If you want @value{GDBN} to be able to stop your program while it is
21531 running, you need to use an interrupt-driven serial driver, and arrange
21532 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21533 character). That is the character which @value{GDBN} uses to tell the
21534 remote system to stop.
21536 Getting the debugging target to return the proper status to @value{GDBN}
21537 probably requires changes to the standard stub; one quick and dirty way
21538 is to just execute a breakpoint instruction (the ``dirty'' part is that
21539 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21541 Other routines you need to supply are:
21544 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21545 @findex exceptionHandler
21546 Write this function to install @var{exception_address} in the exception
21547 handling tables. You need to do this because the stub does not have any
21548 way of knowing what the exception handling tables on your target system
21549 are like (for example, the processor's table might be in @sc{rom},
21550 containing entries which point to a table in @sc{ram}).
21551 The @var{exception_number} specifies the exception which should be changed;
21552 its meaning is architecture-dependent (for example, different numbers
21553 might represent divide by zero, misaligned access, etc). When this
21554 exception occurs, control should be transferred directly to
21555 @var{exception_address}, and the processor state (stack, registers,
21556 and so on) should be just as it is when a processor exception occurs. So if
21557 you want to use a jump instruction to reach @var{exception_address}, it
21558 should be a simple jump, not a jump to subroutine.
21560 For the 386, @var{exception_address} should be installed as an interrupt
21561 gate so that interrupts are masked while the handler runs. The gate
21562 should be at privilege level 0 (the most privileged level). The
21563 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21564 help from @code{exceptionHandler}.
21566 @item void flush_i_cache()
21567 @findex flush_i_cache
21568 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21569 instruction cache, if any, on your target machine. If there is no
21570 instruction cache, this subroutine may be a no-op.
21572 On target machines that have instruction caches, @value{GDBN} requires this
21573 function to make certain that the state of your program is stable.
21577 You must also make sure this library routine is available:
21580 @item void *memset(void *, int, int)
21582 This is the standard library function @code{memset} that sets an area of
21583 memory to a known value. If you have one of the free versions of
21584 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21585 either obtain it from your hardware manufacturer, or write your own.
21588 If you do not use the GNU C compiler, you may need other standard
21589 library subroutines as well; this varies from one stub to another,
21590 but in general the stubs are likely to use any of the common library
21591 subroutines which @code{@value{NGCC}} generates as inline code.
21594 @node Debug Session
21595 @subsection Putting it All Together
21597 @cindex remote serial debugging summary
21598 In summary, when your program is ready to debug, you must follow these
21603 Make sure you have defined the supporting low-level routines
21604 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21606 @code{getDebugChar}, @code{putDebugChar},
21607 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21611 Insert these lines in your program's startup code, before the main
21612 procedure is called:
21619 On some machines, when a breakpoint trap is raised, the hardware
21620 automatically makes the PC point to the instruction after the
21621 breakpoint. If your machine doesn't do that, you may need to adjust
21622 @code{handle_exception} to arrange for it to return to the instruction
21623 after the breakpoint on this first invocation, so that your program
21624 doesn't keep hitting the initial breakpoint instead of making
21628 For the 680x0 stub only, you need to provide a variable called
21629 @code{exceptionHook}. Normally you just use:
21632 void (*exceptionHook)() = 0;
21636 but if before calling @code{set_debug_traps}, you set it to point to a
21637 function in your program, that function is called when
21638 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21639 error). The function indicated by @code{exceptionHook} is called with
21640 one parameter: an @code{int} which is the exception number.
21643 Compile and link together: your program, the @value{GDBN} debugging stub for
21644 your target architecture, and the supporting subroutines.
21647 Make sure you have a serial connection between your target machine and
21648 the @value{GDBN} host, and identify the serial port on the host.
21651 @c The "remote" target now provides a `load' command, so we should
21652 @c document that. FIXME.
21653 Download your program to your target machine (or get it there by
21654 whatever means the manufacturer provides), and start it.
21657 Start @value{GDBN} on the host, and connect to the target
21658 (@pxref{Connecting,,Connecting to a Remote Target}).
21662 @node Configurations
21663 @chapter Configuration-Specific Information
21665 While nearly all @value{GDBN} commands are available for all native and
21666 cross versions of the debugger, there are some exceptions. This chapter
21667 describes things that are only available in certain configurations.
21669 There are three major categories of configurations: native
21670 configurations, where the host and target are the same, embedded
21671 operating system configurations, which are usually the same for several
21672 different processor architectures, and bare embedded processors, which
21673 are quite different from each other.
21678 * Embedded Processors::
21685 This section describes details specific to particular native
21689 * BSD libkvm Interface:: Debugging BSD kernel memory images
21690 * SVR4 Process Information:: SVR4 process information
21691 * DJGPP Native:: Features specific to the DJGPP port
21692 * Cygwin Native:: Features specific to the Cygwin port
21693 * Hurd Native:: Features specific to @sc{gnu} Hurd
21694 * Darwin:: Features specific to Darwin
21697 @node BSD libkvm Interface
21698 @subsection BSD libkvm Interface
21701 @cindex kernel memory image
21702 @cindex kernel crash dump
21704 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21705 interface that provides a uniform interface for accessing kernel virtual
21706 memory images, including live systems and crash dumps. @value{GDBN}
21707 uses this interface to allow you to debug live kernels and kernel crash
21708 dumps on many native BSD configurations. This is implemented as a
21709 special @code{kvm} debugging target. For debugging a live system, load
21710 the currently running kernel into @value{GDBN} and connect to the
21714 (@value{GDBP}) @b{target kvm}
21717 For debugging crash dumps, provide the file name of the crash dump as an
21721 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21724 Once connected to the @code{kvm} target, the following commands are
21730 Set current context from the @dfn{Process Control Block} (PCB) address.
21733 Set current context from proc address. This command isn't available on
21734 modern FreeBSD systems.
21737 @node SVR4 Process Information
21738 @subsection SVR4 Process Information
21740 @cindex examine process image
21741 @cindex process info via @file{/proc}
21743 Many versions of SVR4 and compatible systems provide a facility called
21744 @samp{/proc} that can be used to examine the image of a running
21745 process using file-system subroutines.
21747 If @value{GDBN} is configured for an operating system with this
21748 facility, the command @code{info proc} is available to report
21749 information about the process running your program, or about any
21750 process running on your system. This includes, as of this writing,
21751 @sc{gnu}/Linux and Solaris, for example.
21753 This command may also work on core files that were created on a system
21754 that has the @samp{/proc} facility.
21760 @itemx info proc @var{process-id}
21761 Summarize available information about any running process. If a
21762 process ID is specified by @var{process-id}, display information about
21763 that process; otherwise display information about the program being
21764 debugged. The summary includes the debugged process ID, the command
21765 line used to invoke it, its current working directory, and its
21766 executable file's absolute file name.
21768 On some systems, @var{process-id} can be of the form
21769 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21770 within a process. If the optional @var{pid} part is missing, it means
21771 a thread from the process being debugged (the leading @samp{/} still
21772 needs to be present, or else @value{GDBN} will interpret the number as
21773 a process ID rather than a thread ID).
21775 @item info proc cmdline
21776 @cindex info proc cmdline
21777 Show the original command line of the process. This command is
21778 specific to @sc{gnu}/Linux.
21780 @item info proc cwd
21781 @cindex info proc cwd
21782 Show the current working directory of the process. This command is
21783 specific to @sc{gnu}/Linux.
21785 @item info proc exe
21786 @cindex info proc exe
21787 Show the name of executable of the process. This command is specific
21790 @item info proc mappings
21791 @cindex memory address space mappings
21792 Report the memory address space ranges accessible in the program, with
21793 information on whether the process has read, write, or execute access
21794 rights to each range. On @sc{gnu}/Linux systems, each memory range
21795 includes the object file which is mapped to that range, instead of the
21796 memory access rights to that range.
21798 @item info proc stat
21799 @itemx info proc status
21800 @cindex process detailed status information
21801 These subcommands are specific to @sc{gnu}/Linux systems. They show
21802 the process-related information, including the user ID and group ID;
21803 how many threads are there in the process; its virtual memory usage;
21804 the signals that are pending, blocked, and ignored; its TTY; its
21805 consumption of system and user time; its stack size; its @samp{nice}
21806 value; etc. For more information, see the @samp{proc} man page
21807 (type @kbd{man 5 proc} from your shell prompt).
21809 @item info proc all
21810 Show all the information about the process described under all of the
21811 above @code{info proc} subcommands.
21814 @comment These sub-options of 'info proc' were not included when
21815 @comment procfs.c was re-written. Keep their descriptions around
21816 @comment against the day when someone finds the time to put them back in.
21817 @kindex info proc times
21818 @item info proc times
21819 Starting time, user CPU time, and system CPU time for your program and
21822 @kindex info proc id
21824 Report on the process IDs related to your program: its own process ID,
21825 the ID of its parent, the process group ID, and the session ID.
21828 @item set procfs-trace
21829 @kindex set procfs-trace
21830 @cindex @code{procfs} API calls
21831 This command enables and disables tracing of @code{procfs} API calls.
21833 @item show procfs-trace
21834 @kindex show procfs-trace
21835 Show the current state of @code{procfs} API call tracing.
21837 @item set procfs-file @var{file}
21838 @kindex set procfs-file
21839 Tell @value{GDBN} to write @code{procfs} API trace to the named
21840 @var{file}. @value{GDBN} appends the trace info to the previous
21841 contents of the file. The default is to display the trace on the
21844 @item show procfs-file
21845 @kindex show procfs-file
21846 Show the file to which @code{procfs} API trace is written.
21848 @item proc-trace-entry
21849 @itemx proc-trace-exit
21850 @itemx proc-untrace-entry
21851 @itemx proc-untrace-exit
21852 @kindex proc-trace-entry
21853 @kindex proc-trace-exit
21854 @kindex proc-untrace-entry
21855 @kindex proc-untrace-exit
21856 These commands enable and disable tracing of entries into and exits
21857 from the @code{syscall} interface.
21860 @kindex info pidlist
21861 @cindex process list, QNX Neutrino
21862 For QNX Neutrino only, this command displays the list of all the
21863 processes and all the threads within each process.
21866 @kindex info meminfo
21867 @cindex mapinfo list, QNX Neutrino
21868 For QNX Neutrino only, this command displays the list of all mapinfos.
21872 @subsection Features for Debugging @sc{djgpp} Programs
21873 @cindex @sc{djgpp} debugging
21874 @cindex native @sc{djgpp} debugging
21875 @cindex MS-DOS-specific commands
21878 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21879 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21880 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21881 top of real-mode DOS systems and their emulations.
21883 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21884 defines a few commands specific to the @sc{djgpp} port. This
21885 subsection describes those commands.
21890 This is a prefix of @sc{djgpp}-specific commands which print
21891 information about the target system and important OS structures.
21894 @cindex MS-DOS system info
21895 @cindex free memory information (MS-DOS)
21896 @item info dos sysinfo
21897 This command displays assorted information about the underlying
21898 platform: the CPU type and features, the OS version and flavor, the
21899 DPMI version, and the available conventional and DPMI memory.
21904 @cindex segment descriptor tables
21905 @cindex descriptor tables display
21907 @itemx info dos ldt
21908 @itemx info dos idt
21909 These 3 commands display entries from, respectively, Global, Local,
21910 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21911 tables are data structures which store a descriptor for each segment
21912 that is currently in use. The segment's selector is an index into a
21913 descriptor table; the table entry for that index holds the
21914 descriptor's base address and limit, and its attributes and access
21917 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21918 segment (used for both data and the stack), and a DOS segment (which
21919 allows access to DOS/BIOS data structures and absolute addresses in
21920 conventional memory). However, the DPMI host will usually define
21921 additional segments in order to support the DPMI environment.
21923 @cindex garbled pointers
21924 These commands allow to display entries from the descriptor tables.
21925 Without an argument, all entries from the specified table are
21926 displayed. An argument, which should be an integer expression, means
21927 display a single entry whose index is given by the argument. For
21928 example, here's a convenient way to display information about the
21929 debugged program's data segment:
21932 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21933 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21937 This comes in handy when you want to see whether a pointer is outside
21938 the data segment's limit (i.e.@: @dfn{garbled}).
21940 @cindex page tables display (MS-DOS)
21942 @itemx info dos pte
21943 These two commands display entries from, respectively, the Page
21944 Directory and the Page Tables. Page Directories and Page Tables are
21945 data structures which control how virtual memory addresses are mapped
21946 into physical addresses. A Page Table includes an entry for every
21947 page of memory that is mapped into the program's address space; there
21948 may be several Page Tables, each one holding up to 4096 entries. A
21949 Page Directory has up to 4096 entries, one each for every Page Table
21950 that is currently in use.
21952 Without an argument, @kbd{info dos pde} displays the entire Page
21953 Directory, and @kbd{info dos pte} displays all the entries in all of
21954 the Page Tables. An argument, an integer expression, given to the
21955 @kbd{info dos pde} command means display only that entry from the Page
21956 Directory table. An argument given to the @kbd{info dos pte} command
21957 means display entries from a single Page Table, the one pointed to by
21958 the specified entry in the Page Directory.
21960 @cindex direct memory access (DMA) on MS-DOS
21961 These commands are useful when your program uses @dfn{DMA} (Direct
21962 Memory Access), which needs physical addresses to program the DMA
21965 These commands are supported only with some DPMI servers.
21967 @cindex physical address from linear address
21968 @item info dos address-pte @var{addr}
21969 This command displays the Page Table entry for a specified linear
21970 address. The argument @var{addr} is a linear address which should
21971 already have the appropriate segment's base address added to it,
21972 because this command accepts addresses which may belong to @emph{any}
21973 segment. For example, here's how to display the Page Table entry for
21974 the page where a variable @code{i} is stored:
21977 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21978 @exdent @code{Page Table entry for address 0x11a00d30:}
21979 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21983 This says that @code{i} is stored at offset @code{0xd30} from the page
21984 whose physical base address is @code{0x02698000}, and shows all the
21985 attributes of that page.
21987 Note that you must cast the addresses of variables to a @code{char *},
21988 since otherwise the value of @code{__djgpp_base_address}, the base
21989 address of all variables and functions in a @sc{djgpp} program, will
21990 be added using the rules of C pointer arithmetics: if @code{i} is
21991 declared an @code{int}, @value{GDBN} will add 4 times the value of
21992 @code{__djgpp_base_address} to the address of @code{i}.
21994 Here's another example, it displays the Page Table entry for the
21998 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21999 @exdent @code{Page Table entry for address 0x29110:}
22000 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22004 (The @code{+ 3} offset is because the transfer buffer's address is the
22005 3rd member of the @code{_go32_info_block} structure.) The output
22006 clearly shows that this DPMI server maps the addresses in conventional
22007 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22008 linear (@code{0x29110}) addresses are identical.
22010 This command is supported only with some DPMI servers.
22013 @cindex DOS serial data link, remote debugging
22014 In addition to native debugging, the DJGPP port supports remote
22015 debugging via a serial data link. The following commands are specific
22016 to remote serial debugging in the DJGPP port of @value{GDBN}.
22019 @kindex set com1base
22020 @kindex set com1irq
22021 @kindex set com2base
22022 @kindex set com2irq
22023 @kindex set com3base
22024 @kindex set com3irq
22025 @kindex set com4base
22026 @kindex set com4irq
22027 @item set com1base @var{addr}
22028 This command sets the base I/O port address of the @file{COM1} serial
22031 @item set com1irq @var{irq}
22032 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22033 for the @file{COM1} serial port.
22035 There are similar commands @samp{set com2base}, @samp{set com3irq},
22036 etc.@: for setting the port address and the @code{IRQ} lines for the
22039 @kindex show com1base
22040 @kindex show com1irq
22041 @kindex show com2base
22042 @kindex show com2irq
22043 @kindex show com3base
22044 @kindex show com3irq
22045 @kindex show com4base
22046 @kindex show com4irq
22047 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22048 display the current settings of the base address and the @code{IRQ}
22049 lines used by the COM ports.
22052 @kindex info serial
22053 @cindex DOS serial port status
22054 This command prints the status of the 4 DOS serial ports. For each
22055 port, it prints whether it's active or not, its I/O base address and
22056 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22057 counts of various errors encountered so far.
22061 @node Cygwin Native
22062 @subsection Features for Debugging MS Windows PE Executables
22063 @cindex MS Windows debugging
22064 @cindex native Cygwin debugging
22065 @cindex Cygwin-specific commands
22067 @value{GDBN} supports native debugging of MS Windows programs, including
22068 DLLs with and without symbolic debugging information.
22070 @cindex Ctrl-BREAK, MS-Windows
22071 @cindex interrupt debuggee on MS-Windows
22072 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22073 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22074 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22075 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22076 sequence, which can be used to interrupt the debuggee even if it
22079 There are various additional Cygwin-specific commands, described in
22080 this section. Working with DLLs that have no debugging symbols is
22081 described in @ref{Non-debug DLL Symbols}.
22086 This is a prefix of MS Windows-specific commands which print
22087 information about the target system and important OS structures.
22089 @item info w32 selector
22090 This command displays information returned by
22091 the Win32 API @code{GetThreadSelectorEntry} function.
22092 It takes an optional argument that is evaluated to
22093 a long value to give the information about this given selector.
22094 Without argument, this command displays information
22095 about the six segment registers.
22097 @item info w32 thread-information-block
22098 This command displays thread specific information stored in the
22099 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22100 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22102 @kindex signal-event
22103 @item signal-event @var{id}
22104 This command signals an event with user-provided @var{id}. Used to resume
22105 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22107 To use it, create or edit the following keys in
22108 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22109 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22110 (for x86_64 versions):
22114 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22115 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22116 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22118 The first @code{%ld} will be replaced by the process ID of the
22119 crashing process, the second @code{%ld} will be replaced by the ID of
22120 the event that blocks the crashing process, waiting for @value{GDBN}
22124 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22125 make the system run debugger specified by the Debugger key
22126 automatically, @code{0} will cause a dialog box with ``OK'' and
22127 ``Cancel'' buttons to appear, which allows the user to either
22128 terminate the crashing process (OK) or debug it (Cancel).
22131 @kindex set cygwin-exceptions
22132 @cindex debugging the Cygwin DLL
22133 @cindex Cygwin DLL, debugging
22134 @item set cygwin-exceptions @var{mode}
22135 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22136 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22137 @value{GDBN} will delay recognition of exceptions, and may ignore some
22138 exceptions which seem to be caused by internal Cygwin DLL
22139 ``bookkeeping''. This option is meant primarily for debugging the
22140 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22141 @value{GDBN} users with false @code{SIGSEGV} signals.
22143 @kindex show cygwin-exceptions
22144 @item show cygwin-exceptions
22145 Displays whether @value{GDBN} will break on exceptions that happen
22146 inside the Cygwin DLL itself.
22148 @kindex set new-console
22149 @item set new-console @var{mode}
22150 If @var{mode} is @code{on} the debuggee will
22151 be started in a new console on next start.
22152 If @var{mode} is @code{off}, the debuggee will
22153 be started in the same console as the debugger.
22155 @kindex show new-console
22156 @item show new-console
22157 Displays whether a new console is used
22158 when the debuggee is started.
22160 @kindex set new-group
22161 @item set new-group @var{mode}
22162 This boolean value controls whether the debuggee should
22163 start a new group or stay in the same group as the debugger.
22164 This affects the way the Windows OS handles
22167 @kindex show new-group
22168 @item show new-group
22169 Displays current value of new-group boolean.
22171 @kindex set debugevents
22172 @item set debugevents
22173 This boolean value adds debug output concerning kernel events related
22174 to the debuggee seen by the debugger. This includes events that
22175 signal thread and process creation and exit, DLL loading and
22176 unloading, console interrupts, and debugging messages produced by the
22177 Windows @code{OutputDebugString} API call.
22179 @kindex set debugexec
22180 @item set debugexec
22181 This boolean value adds debug output concerning execute events
22182 (such as resume thread) seen by the debugger.
22184 @kindex set debugexceptions
22185 @item set debugexceptions
22186 This boolean value adds debug output concerning exceptions in the
22187 debuggee seen by the debugger.
22189 @kindex set debugmemory
22190 @item set debugmemory
22191 This boolean value adds debug output concerning debuggee memory reads
22192 and writes by the debugger.
22196 This boolean values specifies whether the debuggee is called
22197 via a shell or directly (default value is on).
22201 Displays if the debuggee will be started with a shell.
22206 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22209 @node Non-debug DLL Symbols
22210 @subsubsection Support for DLLs without Debugging Symbols
22211 @cindex DLLs with no debugging symbols
22212 @cindex Minimal symbols and DLLs
22214 Very often on windows, some of the DLLs that your program relies on do
22215 not include symbolic debugging information (for example,
22216 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22217 symbols in a DLL, it relies on the minimal amount of symbolic
22218 information contained in the DLL's export table. This section
22219 describes working with such symbols, known internally to @value{GDBN} as
22220 ``minimal symbols''.
22222 Note that before the debugged program has started execution, no DLLs
22223 will have been loaded. The easiest way around this problem is simply to
22224 start the program --- either by setting a breakpoint or letting the
22225 program run once to completion.
22227 @subsubsection DLL Name Prefixes
22229 In keeping with the naming conventions used by the Microsoft debugging
22230 tools, DLL export symbols are made available with a prefix based on the
22231 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22232 also entered into the symbol table, so @code{CreateFileA} is often
22233 sufficient. In some cases there will be name clashes within a program
22234 (particularly if the executable itself includes full debugging symbols)
22235 necessitating the use of the fully qualified name when referring to the
22236 contents of the DLL. Use single-quotes around the name to avoid the
22237 exclamation mark (``!'') being interpreted as a language operator.
22239 Note that the internal name of the DLL may be all upper-case, even
22240 though the file name of the DLL is lower-case, or vice-versa. Since
22241 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22242 some confusion. If in doubt, try the @code{info functions} and
22243 @code{info variables} commands or even @code{maint print msymbols}
22244 (@pxref{Symbols}). Here's an example:
22247 (@value{GDBP}) info function CreateFileA
22248 All functions matching regular expression "CreateFileA":
22250 Non-debugging symbols:
22251 0x77e885f4 CreateFileA
22252 0x77e885f4 KERNEL32!CreateFileA
22256 (@value{GDBP}) info function !
22257 All functions matching regular expression "!":
22259 Non-debugging symbols:
22260 0x6100114c cygwin1!__assert
22261 0x61004034 cygwin1!_dll_crt0@@0
22262 0x61004240 cygwin1!dll_crt0(per_process *)
22266 @subsubsection Working with Minimal Symbols
22268 Symbols extracted from a DLL's export table do not contain very much
22269 type information. All that @value{GDBN} can do is guess whether a symbol
22270 refers to a function or variable depending on the linker section that
22271 contains the symbol. Also note that the actual contents of the memory
22272 contained in a DLL are not available unless the program is running. This
22273 means that you cannot examine the contents of a variable or disassemble
22274 a function within a DLL without a running program.
22276 Variables are generally treated as pointers and dereferenced
22277 automatically. For this reason, it is often necessary to prefix a
22278 variable name with the address-of operator (``&'') and provide explicit
22279 type information in the command. Here's an example of the type of
22283 (@value{GDBP}) print 'cygwin1!__argv'
22284 'cygwin1!__argv' has unknown type; cast it to its declared type
22288 (@value{GDBP}) x 'cygwin1!__argv'
22289 'cygwin1!__argv' has unknown type; cast it to its declared type
22292 And two possible solutions:
22295 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22296 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22300 (@value{GDBP}) x/2x &'cygwin1!__argv'
22301 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22302 (@value{GDBP}) x/x 0x10021608
22303 0x10021608: 0x0022fd98
22304 (@value{GDBP}) x/s 0x0022fd98
22305 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22308 Setting a break point within a DLL is possible even before the program
22309 starts execution. However, under these circumstances, @value{GDBN} can't
22310 examine the initial instructions of the function in order to skip the
22311 function's frame set-up code. You can work around this by using ``*&''
22312 to set the breakpoint at a raw memory address:
22315 (@value{GDBP}) break *&'python22!PyOS_Readline'
22316 Breakpoint 1 at 0x1e04eff0
22319 The author of these extensions is not entirely convinced that setting a
22320 break point within a shared DLL like @file{kernel32.dll} is completely
22324 @subsection Commands Specific to @sc{gnu} Hurd Systems
22325 @cindex @sc{gnu} Hurd debugging
22327 This subsection describes @value{GDBN} commands specific to the
22328 @sc{gnu} Hurd native debugging.
22333 @kindex set signals@r{, Hurd command}
22334 @kindex set sigs@r{, Hurd command}
22335 This command toggles the state of inferior signal interception by
22336 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22337 affected by this command. @code{sigs} is a shorthand alias for
22342 @kindex show signals@r{, Hurd command}
22343 @kindex show sigs@r{, Hurd command}
22344 Show the current state of intercepting inferior's signals.
22346 @item set signal-thread
22347 @itemx set sigthread
22348 @kindex set signal-thread
22349 @kindex set sigthread
22350 This command tells @value{GDBN} which thread is the @code{libc} signal
22351 thread. That thread is run when a signal is delivered to a running
22352 process. @code{set sigthread} is the shorthand alias of @code{set
22355 @item show signal-thread
22356 @itemx show sigthread
22357 @kindex show signal-thread
22358 @kindex show sigthread
22359 These two commands show which thread will run when the inferior is
22360 delivered a signal.
22363 @kindex set stopped@r{, Hurd command}
22364 This commands tells @value{GDBN} that the inferior process is stopped,
22365 as with the @code{SIGSTOP} signal. The stopped process can be
22366 continued by delivering a signal to it.
22369 @kindex show stopped@r{, Hurd command}
22370 This command shows whether @value{GDBN} thinks the debuggee is
22373 @item set exceptions
22374 @kindex set exceptions@r{, Hurd command}
22375 Use this command to turn off trapping of exceptions in the inferior.
22376 When exception trapping is off, neither breakpoints nor
22377 single-stepping will work. To restore the default, set exception
22380 @item show exceptions
22381 @kindex show exceptions@r{, Hurd command}
22382 Show the current state of trapping exceptions in the inferior.
22384 @item set task pause
22385 @kindex set task@r{, Hurd commands}
22386 @cindex task attributes (@sc{gnu} Hurd)
22387 @cindex pause current task (@sc{gnu} Hurd)
22388 This command toggles task suspension when @value{GDBN} has control.
22389 Setting it to on takes effect immediately, and the task is suspended
22390 whenever @value{GDBN} gets control. Setting it to off will take
22391 effect the next time the inferior is continued. If this option is set
22392 to off, you can use @code{set thread default pause on} or @code{set
22393 thread pause on} (see below) to pause individual threads.
22395 @item show task pause
22396 @kindex show task@r{, Hurd commands}
22397 Show the current state of task suspension.
22399 @item set task detach-suspend-count
22400 @cindex task suspend count
22401 @cindex detach from task, @sc{gnu} Hurd
22402 This command sets the suspend count the task will be left with when
22403 @value{GDBN} detaches from it.
22405 @item show task detach-suspend-count
22406 Show the suspend count the task will be left with when detaching.
22408 @item set task exception-port
22409 @itemx set task excp
22410 @cindex task exception port, @sc{gnu} Hurd
22411 This command sets the task exception port to which @value{GDBN} will
22412 forward exceptions. The argument should be the value of the @dfn{send
22413 rights} of the task. @code{set task excp} is a shorthand alias.
22415 @item set noninvasive
22416 @cindex noninvasive task options
22417 This command switches @value{GDBN} to a mode that is the least
22418 invasive as far as interfering with the inferior is concerned. This
22419 is the same as using @code{set task pause}, @code{set exceptions}, and
22420 @code{set signals} to values opposite to the defaults.
22422 @item info send-rights
22423 @itemx info receive-rights
22424 @itemx info port-rights
22425 @itemx info port-sets
22426 @itemx info dead-names
22429 @cindex send rights, @sc{gnu} Hurd
22430 @cindex receive rights, @sc{gnu} Hurd
22431 @cindex port rights, @sc{gnu} Hurd
22432 @cindex port sets, @sc{gnu} Hurd
22433 @cindex dead names, @sc{gnu} Hurd
22434 These commands display information about, respectively, send rights,
22435 receive rights, port rights, port sets, and dead names of a task.
22436 There are also shorthand aliases: @code{info ports} for @code{info
22437 port-rights} and @code{info psets} for @code{info port-sets}.
22439 @item set thread pause
22440 @kindex set thread@r{, Hurd command}
22441 @cindex thread properties, @sc{gnu} Hurd
22442 @cindex pause current thread (@sc{gnu} Hurd)
22443 This command toggles current thread suspension when @value{GDBN} has
22444 control. Setting it to on takes effect immediately, and the current
22445 thread is suspended whenever @value{GDBN} gets control. Setting it to
22446 off will take effect the next time the inferior is continued.
22447 Normally, this command has no effect, since when @value{GDBN} has
22448 control, the whole task is suspended. However, if you used @code{set
22449 task pause off} (see above), this command comes in handy to suspend
22450 only the current thread.
22452 @item show thread pause
22453 @kindex show thread@r{, Hurd command}
22454 This command shows the state of current thread suspension.
22456 @item set thread run
22457 This command sets whether the current thread is allowed to run.
22459 @item show thread run
22460 Show whether the current thread is allowed to run.
22462 @item set thread detach-suspend-count
22463 @cindex thread suspend count, @sc{gnu} Hurd
22464 @cindex detach from thread, @sc{gnu} Hurd
22465 This command sets the suspend count @value{GDBN} will leave on a
22466 thread when detaching. This number is relative to the suspend count
22467 found by @value{GDBN} when it notices the thread; use @code{set thread
22468 takeover-suspend-count} to force it to an absolute value.
22470 @item show thread detach-suspend-count
22471 Show the suspend count @value{GDBN} will leave on the thread when
22474 @item set thread exception-port
22475 @itemx set thread excp
22476 Set the thread exception port to which to forward exceptions. This
22477 overrides the port set by @code{set task exception-port} (see above).
22478 @code{set thread excp} is the shorthand alias.
22480 @item set thread takeover-suspend-count
22481 Normally, @value{GDBN}'s thread suspend counts are relative to the
22482 value @value{GDBN} finds when it notices each thread. This command
22483 changes the suspend counts to be absolute instead.
22485 @item set thread default
22486 @itemx show thread default
22487 @cindex thread default settings, @sc{gnu} Hurd
22488 Each of the above @code{set thread} commands has a @code{set thread
22489 default} counterpart (e.g., @code{set thread default pause}, @code{set
22490 thread default exception-port}, etc.). The @code{thread default}
22491 variety of commands sets the default thread properties for all
22492 threads; you can then change the properties of individual threads with
22493 the non-default commands.
22500 @value{GDBN} provides the following commands specific to the Darwin target:
22503 @item set debug darwin @var{num}
22504 @kindex set debug darwin
22505 When set to a non zero value, enables debugging messages specific to
22506 the Darwin support. Higher values produce more verbose output.
22508 @item show debug darwin
22509 @kindex show debug darwin
22510 Show the current state of Darwin messages.
22512 @item set debug mach-o @var{num}
22513 @kindex set debug mach-o
22514 When set to a non zero value, enables debugging messages while
22515 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22516 file format used on Darwin for object and executable files.) Higher
22517 values produce more verbose output. This is a command to diagnose
22518 problems internal to @value{GDBN} and should not be needed in normal
22521 @item show debug mach-o
22522 @kindex show debug mach-o
22523 Show the current state of Mach-O file messages.
22525 @item set mach-exceptions on
22526 @itemx set mach-exceptions off
22527 @kindex set mach-exceptions
22528 On Darwin, faults are first reported as a Mach exception and are then
22529 mapped to a Posix signal. Use this command to turn on trapping of
22530 Mach exceptions in the inferior. This might be sometimes useful to
22531 better understand the cause of a fault. The default is off.
22533 @item show mach-exceptions
22534 @kindex show mach-exceptions
22535 Show the current state of exceptions trapping.
22540 @section Embedded Operating Systems
22542 This section describes configurations involving the debugging of
22543 embedded operating systems that are available for several different
22546 @value{GDBN} includes the ability to debug programs running on
22547 various real-time operating systems.
22549 @node Embedded Processors
22550 @section Embedded Processors
22552 This section goes into details specific to particular embedded
22555 @cindex send command to simulator
22556 Whenever a specific embedded processor has a simulator, @value{GDBN}
22557 allows to send an arbitrary command to the simulator.
22560 @item sim @var{command}
22561 @kindex sim@r{, a command}
22562 Send an arbitrary @var{command} string to the simulator. Consult the
22563 documentation for the specific simulator in use for information about
22564 acceptable commands.
22569 * ARC:: Synopsys ARC
22571 * M68K:: Motorola M68K
22572 * MicroBlaze:: Xilinx MicroBlaze
22573 * MIPS Embedded:: MIPS Embedded
22574 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22575 * PowerPC Embedded:: PowerPC Embedded
22578 * Super-H:: Renesas Super-H
22582 @subsection Synopsys ARC
22583 @cindex Synopsys ARC
22584 @cindex ARC specific commands
22590 @value{GDBN} provides the following ARC-specific commands:
22593 @item set debug arc
22594 @kindex set debug arc
22595 Control the level of ARC specific debug messages. Use 0 for no messages (the
22596 default), 1 for debug messages, and 2 for even more debug messages.
22598 @item show debug arc
22599 @kindex show debug arc
22600 Show the level of ARC specific debugging in operation.
22602 @item maint print arc arc-instruction @var{address}
22603 @kindex maint print arc arc-instruction
22604 Print internal disassembler information about instruction at a given address.
22611 @value{GDBN} provides the following ARM-specific commands:
22614 @item set arm disassembler
22616 This commands selects from a list of disassembly styles. The
22617 @code{"std"} style is the standard style.
22619 @item show arm disassembler
22621 Show the current disassembly style.
22623 @item set arm apcs32
22624 @cindex ARM 32-bit mode
22625 This command toggles ARM operation mode between 32-bit and 26-bit.
22627 @item show arm apcs32
22628 Display the current usage of the ARM 32-bit mode.
22630 @item set arm fpu @var{fputype}
22631 This command sets the ARM floating-point unit (FPU) type. The
22632 argument @var{fputype} can be one of these:
22636 Determine the FPU type by querying the OS ABI.
22638 Software FPU, with mixed-endian doubles on little-endian ARM
22641 GCC-compiled FPA co-processor.
22643 Software FPU with pure-endian doubles.
22649 Show the current type of the FPU.
22652 This command forces @value{GDBN} to use the specified ABI.
22655 Show the currently used ABI.
22657 @item set arm fallback-mode (arm|thumb|auto)
22658 @value{GDBN} uses the symbol table, when available, to determine
22659 whether instructions are ARM or Thumb. This command controls
22660 @value{GDBN}'s default behavior when the symbol table is not
22661 available. The default is @samp{auto}, which causes @value{GDBN} to
22662 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22665 @item show arm fallback-mode
22666 Show the current fallback instruction mode.
22668 @item set arm force-mode (arm|thumb|auto)
22669 This command overrides use of the symbol table to determine whether
22670 instructions are ARM or Thumb. The default is @samp{auto}, which
22671 causes @value{GDBN} to use the symbol table and then the setting
22672 of @samp{set arm fallback-mode}.
22674 @item show arm force-mode
22675 Show the current forced instruction mode.
22677 @item set debug arm
22678 Toggle whether to display ARM-specific debugging messages from the ARM
22679 target support subsystem.
22681 @item show debug arm
22682 Show whether ARM-specific debugging messages are enabled.
22686 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22687 The @value{GDBN} ARM simulator accepts the following optional arguments.
22690 @item --swi-support=@var{type}
22691 Tell the simulator which SWI interfaces to support. The argument
22692 @var{type} may be a comma separated list of the following values.
22693 The default value is @code{all}.
22708 The Motorola m68k configuration includes ColdFire support.
22711 @subsection MicroBlaze
22712 @cindex Xilinx MicroBlaze
22713 @cindex XMD, Xilinx Microprocessor Debugger
22715 The MicroBlaze is a soft-core processor supported on various Xilinx
22716 FPGAs, such as Spartan or Virtex series. Boards with these processors
22717 usually have JTAG ports which connect to a host system running the Xilinx
22718 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22719 This host system is used to download the configuration bitstream to
22720 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22721 communicates with the target board using the JTAG interface and
22722 presents a @code{gdbserver} interface to the board. By default
22723 @code{xmd} uses port @code{1234}. (While it is possible to change
22724 this default port, it requires the use of undocumented @code{xmd}
22725 commands. Contact Xilinx support if you need to do this.)
22727 Use these GDB commands to connect to the MicroBlaze target processor.
22730 @item target remote :1234
22731 Use this command to connect to the target if you are running @value{GDBN}
22732 on the same system as @code{xmd}.
22734 @item target remote @var{xmd-host}:1234
22735 Use this command to connect to the target if it is connected to @code{xmd}
22736 running on a different system named @var{xmd-host}.
22739 Use this command to download a program to the MicroBlaze target.
22741 @item set debug microblaze @var{n}
22742 Enable MicroBlaze-specific debugging messages if non-zero.
22744 @item show debug microblaze @var{n}
22745 Show MicroBlaze-specific debugging level.
22748 @node MIPS Embedded
22749 @subsection @acronym{MIPS} Embedded
22752 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22755 @item set mipsfpu double
22756 @itemx set mipsfpu single
22757 @itemx set mipsfpu none
22758 @itemx set mipsfpu auto
22759 @itemx show mipsfpu
22760 @kindex set mipsfpu
22761 @kindex show mipsfpu
22762 @cindex @acronym{MIPS} remote floating point
22763 @cindex floating point, @acronym{MIPS} remote
22764 If your target board does not support the @acronym{MIPS} floating point
22765 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22766 need this, you may wish to put the command in your @value{GDBN} init
22767 file). This tells @value{GDBN} how to find the return value of
22768 functions which return floating point values. It also allows
22769 @value{GDBN} to avoid saving the floating point registers when calling
22770 functions on the board. If you are using a floating point coprocessor
22771 with only single precision floating point support, as on the @sc{r4650}
22772 processor, use the command @samp{set mipsfpu single}. The default
22773 double precision floating point coprocessor may be selected using
22774 @samp{set mipsfpu double}.
22776 In previous versions the only choices were double precision or no
22777 floating point, so @samp{set mipsfpu on} will select double precision
22778 and @samp{set mipsfpu off} will select no floating point.
22780 As usual, you can inquire about the @code{mipsfpu} variable with
22781 @samp{show mipsfpu}.
22784 @node OpenRISC 1000
22785 @subsection OpenRISC 1000
22786 @cindex OpenRISC 1000
22789 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22790 mainly provided as a soft-core which can run on Xilinx, Altera and other
22793 @value{GDBN} for OpenRISC supports the below commands when connecting to
22801 Runs the builtin CPU simulator which can run very basic
22802 programs but does not support most hardware functions like MMU.
22803 For more complex use cases the user is advised to run an external
22804 target, and connect using @samp{target remote}.
22806 Example: @code{target sim}
22808 @item set debug or1k
22809 Toggle whether to display OpenRISC-specific debugging messages from the
22810 OpenRISC target support subsystem.
22812 @item show debug or1k
22813 Show whether OpenRISC-specific debugging messages are enabled.
22816 @node PowerPC Embedded
22817 @subsection PowerPC Embedded
22819 @cindex DVC register
22820 @value{GDBN} supports using the DVC (Data Value Compare) register to
22821 implement in hardware simple hardware watchpoint conditions of the form:
22824 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22825 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22828 The DVC register will be automatically used when @value{GDBN} detects
22829 such pattern in a condition expression, and the created watchpoint uses one
22830 debug register (either the @code{exact-watchpoints} option is on and the
22831 variable is scalar, or the variable has a length of one byte). This feature
22832 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22835 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22836 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22837 in which case watchpoints using only one debug register are created when
22838 watching variables of scalar types.
22840 You can create an artificial array to watch an arbitrary memory
22841 region using one of the following commands (@pxref{Expressions}):
22844 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22845 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22848 PowerPC embedded processors support masked watchpoints. See the discussion
22849 about the @code{mask} argument in @ref{Set Watchpoints}.
22851 @cindex ranged breakpoint
22852 PowerPC embedded processors support hardware accelerated
22853 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22854 the inferior whenever it executes an instruction at any address within
22855 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22856 use the @code{break-range} command.
22858 @value{GDBN} provides the following PowerPC-specific commands:
22861 @kindex break-range
22862 @item break-range @var{start-location}, @var{end-location}
22863 Set a breakpoint for an address range given by
22864 @var{start-location} and @var{end-location}, which can specify a function name,
22865 a line number, an offset of lines from the current line or from the start
22866 location, or an address of an instruction (see @ref{Specify Location},
22867 for a list of all the possible ways to specify a @var{location}.)
22868 The breakpoint will stop execution of the inferior whenever it
22869 executes an instruction at any address within the specified range,
22870 (including @var{start-location} and @var{end-location}.)
22872 @kindex set powerpc
22873 @item set powerpc soft-float
22874 @itemx show powerpc soft-float
22875 Force @value{GDBN} to use (or not use) a software floating point calling
22876 convention. By default, @value{GDBN} selects the calling convention based
22877 on the selected architecture and the provided executable file.
22879 @item set powerpc vector-abi
22880 @itemx show powerpc vector-abi
22881 Force @value{GDBN} to use the specified calling convention for vector
22882 arguments and return values. The valid options are @samp{auto};
22883 @samp{generic}, to avoid vector registers even if they are present;
22884 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22885 registers. By default, @value{GDBN} selects the calling convention
22886 based on the selected architecture and the provided executable file.
22888 @item set powerpc exact-watchpoints
22889 @itemx show powerpc exact-watchpoints
22890 Allow @value{GDBN} to use only one debug register when watching a variable
22891 of scalar type, thus assuming that the variable is accessed through the
22892 address of its first byte.
22897 @subsection Atmel AVR
22900 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22901 following AVR-specific commands:
22904 @item info io_registers
22905 @kindex info io_registers@r{, AVR}
22906 @cindex I/O registers (Atmel AVR)
22907 This command displays information about the AVR I/O registers. For
22908 each register, @value{GDBN} prints its number and value.
22915 When configured for debugging CRIS, @value{GDBN} provides the
22916 following CRIS-specific commands:
22919 @item set cris-version @var{ver}
22920 @cindex CRIS version
22921 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22922 The CRIS version affects register names and sizes. This command is useful in
22923 case autodetection of the CRIS version fails.
22925 @item show cris-version
22926 Show the current CRIS version.
22928 @item set cris-dwarf2-cfi
22929 @cindex DWARF-2 CFI and CRIS
22930 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22931 Change to @samp{off} when using @code{gcc-cris} whose version is below
22934 @item show cris-dwarf2-cfi
22935 Show the current state of using DWARF-2 CFI.
22937 @item set cris-mode @var{mode}
22939 Set the current CRIS mode to @var{mode}. It should only be changed when
22940 debugging in guru mode, in which case it should be set to
22941 @samp{guru} (the default is @samp{normal}).
22943 @item show cris-mode
22944 Show the current CRIS mode.
22948 @subsection Renesas Super-H
22951 For the Renesas Super-H processor, @value{GDBN} provides these
22955 @item set sh calling-convention @var{convention}
22956 @kindex set sh calling-convention
22957 Set the calling-convention used when calling functions from @value{GDBN}.
22958 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22959 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22960 convention. If the DWARF-2 information of the called function specifies
22961 that the function follows the Renesas calling convention, the function
22962 is called using the Renesas calling convention. If the calling convention
22963 is set to @samp{renesas}, the Renesas calling convention is always used,
22964 regardless of the DWARF-2 information. This can be used to override the
22965 default of @samp{gcc} if debug information is missing, or the compiler
22966 does not emit the DWARF-2 calling convention entry for a function.
22968 @item show sh calling-convention
22969 @kindex show sh calling-convention
22970 Show the current calling convention setting.
22975 @node Architectures
22976 @section Architectures
22978 This section describes characteristics of architectures that affect
22979 all uses of @value{GDBN} with the architecture, both native and cross.
22986 * HPPA:: HP PA architecture
22987 * SPU:: Cell Broadband Engine SPU architecture
22994 @subsection AArch64
22995 @cindex AArch64 support
22997 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22998 following special commands:
23001 @item set debug aarch64
23002 @kindex set debug aarch64
23003 This command determines whether AArch64 architecture-specific debugging
23004 messages are to be displayed.
23006 @item show debug aarch64
23007 Show whether AArch64 debugging messages are displayed.
23012 @subsection x86 Architecture-specific Issues
23015 @item set struct-convention @var{mode}
23016 @kindex set struct-convention
23017 @cindex struct return convention
23018 @cindex struct/union returned in registers
23019 Set the convention used by the inferior to return @code{struct}s and
23020 @code{union}s from functions to @var{mode}. Possible values of
23021 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23022 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23023 are returned on the stack, while @code{"reg"} means that a
23024 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23025 be returned in a register.
23027 @item show struct-convention
23028 @kindex show struct-convention
23029 Show the current setting of the convention to return @code{struct}s
23034 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23035 @cindex Intel Memory Protection Extensions (MPX).
23037 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23038 @footnote{The register named with capital letters represent the architecture
23039 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23040 which are the lower bound and upper bound. Bounds are effective addresses or
23041 memory locations. The upper bounds are architecturally represented in 1's
23042 complement form. A bound having lower bound = 0, and upper bound = 0
23043 (1's complement of all bits set) will allow access to the entire address space.
23045 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23046 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23047 display the upper bound performing the complement of one operation on the
23048 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23049 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23050 can also be noted that the upper bounds are inclusive.
23052 As an example, assume that the register BND0 holds bounds for a pointer having
23053 access allowed for the range between 0x32 and 0x71. The values present on
23054 bnd0raw and bnd registers are presented as follows:
23057 bnd0raw = @{0x32, 0xffffffff8e@}
23058 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23061 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23062 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23063 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23064 Python, the display includes the memory size, in bits, accessible to
23067 Bounds can also be stored in bounds tables, which are stored in
23068 application memory. These tables store bounds for pointers by specifying
23069 the bounds pointer's value along with its bounds. Evaluating and changing
23070 bounds located in bound tables is therefore interesting while investigating
23071 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23074 @item show mpx bound @var{pointer}
23075 @kindex show mpx bound
23076 Display bounds of the given @var{pointer}.
23078 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23079 @kindex set mpx bound
23080 Set the bounds of a pointer in the bound table.
23081 This command takes three parameters: @var{pointer} is the pointers
23082 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23083 for lower and upper bounds respectively.
23086 When you call an inferior function on an Intel MPX enabled program,
23087 GDB sets the inferior's bound registers to the init (disabled) state
23088 before calling the function. As a consequence, bounds checks for the
23089 pointer arguments passed to the function will always pass.
23091 This is necessary because when you call an inferior function, the
23092 program is usually in the middle of the execution of other function.
23093 Since at that point bound registers are in an arbitrary state, not
23094 clearing them would lead to random bound violations in the called
23097 You can still examine the influence of the bound registers on the
23098 execution of the called function by stopping the execution of the
23099 called function at its prologue, setting bound registers, and
23100 continuing the execution. For example:
23104 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23105 $ print upper (a, b, c, d, 1)
23106 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23108 @{lbound = 0x0, ubound = ffffffff@} : size -1
23111 At this last step the value of bnd0 can be changed for investigation of bound
23112 violations caused along the execution of the call. In order to know how to
23113 set the bound registers or bound table for the call consult the ABI.
23118 See the following section.
23121 @subsection @acronym{MIPS}
23123 @cindex stack on Alpha
23124 @cindex stack on @acronym{MIPS}
23125 @cindex Alpha stack
23126 @cindex @acronym{MIPS} stack
23127 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23128 sometimes requires @value{GDBN} to search backward in the object code to
23129 find the beginning of a function.
23131 @cindex response time, @acronym{MIPS} debugging
23132 To improve response time (especially for embedded applications, where
23133 @value{GDBN} may be restricted to a slow serial line for this search)
23134 you may want to limit the size of this search, using one of these
23138 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23139 @item set heuristic-fence-post @var{limit}
23140 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23141 search for the beginning of a function. A value of @var{0} (the
23142 default) means there is no limit. However, except for @var{0}, the
23143 larger the limit the more bytes @code{heuristic-fence-post} must search
23144 and therefore the longer it takes to run. You should only need to use
23145 this command when debugging a stripped executable.
23147 @item show heuristic-fence-post
23148 Display the current limit.
23152 These commands are available @emph{only} when @value{GDBN} is configured
23153 for debugging programs on Alpha or @acronym{MIPS} processors.
23155 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23159 @item set mips abi @var{arg}
23160 @kindex set mips abi
23161 @cindex set ABI for @acronym{MIPS}
23162 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23163 values of @var{arg} are:
23167 The default ABI associated with the current binary (this is the
23177 @item show mips abi
23178 @kindex show mips abi
23179 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23181 @item set mips compression @var{arg}
23182 @kindex set mips compression
23183 @cindex code compression, @acronym{MIPS}
23184 Tell @value{GDBN} which @acronym{MIPS} compressed
23185 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23186 inferior. @value{GDBN} uses this for code disassembly and other
23187 internal interpretation purposes. This setting is only referred to
23188 when no executable has been associated with the debugging session or
23189 the executable does not provide information about the encoding it uses.
23190 Otherwise this setting is automatically updated from information
23191 provided by the executable.
23193 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23194 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23195 executables containing @acronym{MIPS16} code frequently are not
23196 identified as such.
23198 This setting is ``sticky''; that is, it retains its value across
23199 debugging sessions until reset either explicitly with this command or
23200 implicitly from an executable.
23202 The compiler and/or assembler typically add symbol table annotations to
23203 identify functions compiled for the @acronym{MIPS16} or
23204 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23205 are present, @value{GDBN} uses them in preference to the global
23206 compressed @acronym{ISA} encoding setting.
23208 @item show mips compression
23209 @kindex show mips compression
23210 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23211 @value{GDBN} to debug the inferior.
23214 @itemx show mipsfpu
23215 @xref{MIPS Embedded, set mipsfpu}.
23217 @item set mips mask-address @var{arg}
23218 @kindex set mips mask-address
23219 @cindex @acronym{MIPS} addresses, masking
23220 This command determines whether the most-significant 32 bits of 64-bit
23221 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23222 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23223 setting, which lets @value{GDBN} determine the correct value.
23225 @item show mips mask-address
23226 @kindex show mips mask-address
23227 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23230 @item set remote-mips64-transfers-32bit-regs
23231 @kindex set remote-mips64-transfers-32bit-regs
23232 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23233 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23234 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23235 and 64 bits for other registers, set this option to @samp{on}.
23237 @item show remote-mips64-transfers-32bit-regs
23238 @kindex show remote-mips64-transfers-32bit-regs
23239 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23241 @item set debug mips
23242 @kindex set debug mips
23243 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23244 target code in @value{GDBN}.
23246 @item show debug mips
23247 @kindex show debug mips
23248 Show the current setting of @acronym{MIPS} debugging messages.
23254 @cindex HPPA support
23256 When @value{GDBN} is debugging the HP PA architecture, it provides the
23257 following special commands:
23260 @item set debug hppa
23261 @kindex set debug hppa
23262 This command determines whether HPPA architecture-specific debugging
23263 messages are to be displayed.
23265 @item show debug hppa
23266 Show whether HPPA debugging messages are displayed.
23268 @item maint print unwind @var{address}
23269 @kindex maint print unwind@r{, HPPA}
23270 This command displays the contents of the unwind table entry at the
23271 given @var{address}.
23277 @subsection Cell Broadband Engine SPU architecture
23278 @cindex Cell Broadband Engine
23281 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23282 it provides the following special commands:
23285 @item info spu event
23287 Display SPU event facility status. Shows current event mask
23288 and pending event status.
23290 @item info spu signal
23291 Display SPU signal notification facility status. Shows pending
23292 signal-control word and signal notification mode of both signal
23293 notification channels.
23295 @item info spu mailbox
23296 Display SPU mailbox facility status. Shows all pending entries,
23297 in order of processing, in each of the SPU Write Outbound,
23298 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23301 Display MFC DMA status. Shows all pending commands in the MFC
23302 DMA queue. For each entry, opcode, tag, class IDs, effective
23303 and local store addresses and transfer size are shown.
23305 @item info spu proxydma
23306 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23307 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23308 and local store addresses and transfer size are shown.
23312 When @value{GDBN} is debugging a combined PowerPC/SPU application
23313 on the Cell Broadband Engine, it provides in addition the following
23317 @item set spu stop-on-load @var{arg}
23319 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23320 will give control to the user when a new SPE thread enters its @code{main}
23321 function. The default is @code{off}.
23323 @item show spu stop-on-load
23325 Show whether to stop for new SPE threads.
23327 @item set spu auto-flush-cache @var{arg}
23328 Set whether to automatically flush the software-managed cache. When set to
23329 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23330 cache to be flushed whenever SPE execution stops. This provides a consistent
23331 view of PowerPC memory that is accessed via the cache. If an application
23332 does not use the software-managed cache, this option has no effect.
23334 @item show spu auto-flush-cache
23335 Show whether to automatically flush the software-managed cache.
23340 @subsection PowerPC
23341 @cindex PowerPC architecture
23343 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23344 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23345 numbers stored in the floating point registers. These values must be stored
23346 in two consecutive registers, always starting at an even register like
23347 @code{f0} or @code{f2}.
23349 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23350 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23351 @code{f2} and @code{f3} for @code{$dl1} and so on.
23353 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23354 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23357 @subsection Nios II
23358 @cindex Nios II architecture
23360 When @value{GDBN} is debugging the Nios II architecture,
23361 it provides the following special commands:
23365 @item set debug nios2
23366 @kindex set debug nios2
23367 This command turns on and off debugging messages for the Nios II
23368 target code in @value{GDBN}.
23370 @item show debug nios2
23371 @kindex show debug nios2
23372 Show the current setting of Nios II debugging messages.
23376 @subsection Sparc64
23377 @cindex Sparc64 support
23378 @cindex Application Data Integrity
23379 @subsubsection ADI Support
23381 The M7 processor supports an Application Data Integrity (ADI) feature that
23382 detects invalid data accesses. When software allocates memory and enables
23383 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23384 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23385 the 4-bit version in every cacheline of that data. Hardware saves the latter
23386 in spare bits in the cache and memory hierarchy. On each load and store,
23387 the processor compares the upper 4 VA (virtual address) bits to the
23388 cacheline's version. If there is a mismatch, the processor generates a
23389 version mismatch trap which can be either precise or disrupting. The trap
23390 is an error condition which the kernel delivers to the process as a SIGSEGV
23393 Note that only 64-bit applications can use ADI and need to be built with
23396 Values of the ADI version tags, which are in granularity of a
23397 cacheline (64 bytes), can be viewed or modified.
23401 @kindex adi examine
23402 @item adi (examine | x) [ / @var{n} ] @var{addr}
23404 The @code{adi examine} command displays the value of one ADI version tag per
23407 @var{n} is a decimal integer specifying the number in bytes; the default
23408 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23409 block size, to display.
23411 @var{addr} is the address in user address space where you want @value{GDBN}
23412 to begin displaying the ADI version tags.
23414 Below is an example of displaying ADI versions of variable "shmaddr".
23417 (@value{GDBP}) adi x/100 shmaddr
23418 0xfff800010002c000: 0 0
23422 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23424 The @code{adi assign} command is used to assign new ADI version tag
23427 @var{n} is a decimal integer specifying the number in bytes;
23428 the default is 1. It specifies how much ADI version information, at the
23429 ratio of 1:ADI block size, to modify.
23431 @var{addr} is the address in user address space where you want @value{GDBN}
23432 to begin modifying the ADI version tags.
23434 @var{tag} is the new ADI version tag.
23436 For example, do the following to modify then verify ADI versions of
23437 variable "shmaddr":
23440 (@value{GDBP}) adi a/100 shmaddr = 7
23441 (@value{GDBP}) adi x/100 shmaddr
23442 0xfff800010002c000: 7 7
23447 @node Controlling GDB
23448 @chapter Controlling @value{GDBN}
23450 You can alter the way @value{GDBN} interacts with you by using the
23451 @code{set} command. For commands controlling how @value{GDBN} displays
23452 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23457 * Editing:: Command editing
23458 * Command History:: Command history
23459 * Screen Size:: Screen size
23460 * Numbers:: Numbers
23461 * ABI:: Configuring the current ABI
23462 * Auto-loading:: Automatically loading associated files
23463 * Messages/Warnings:: Optional warnings and messages
23464 * Debugging Output:: Optional messages about internal happenings
23465 * Other Misc Settings:: Other Miscellaneous Settings
23473 @value{GDBN} indicates its readiness to read a command by printing a string
23474 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23475 can change the prompt string with the @code{set prompt} command. For
23476 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23477 the prompt in one of the @value{GDBN} sessions so that you can always tell
23478 which one you are talking to.
23480 @emph{Note:} @code{set prompt} does not add a space for you after the
23481 prompt you set. This allows you to set a prompt which ends in a space
23482 or a prompt that does not.
23486 @item set prompt @var{newprompt}
23487 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23489 @kindex show prompt
23491 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23494 Versions of @value{GDBN} that ship with Python scripting enabled have
23495 prompt extensions. The commands for interacting with these extensions
23499 @kindex set extended-prompt
23500 @item set extended-prompt @var{prompt}
23501 Set an extended prompt that allows for substitutions.
23502 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23503 substitution. Any escape sequences specified as part of the prompt
23504 string are replaced with the corresponding strings each time the prompt
23510 set extended-prompt Current working directory: \w (gdb)
23513 Note that when an extended-prompt is set, it takes control of the
23514 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23516 @kindex show extended-prompt
23517 @item show extended-prompt
23518 Prints the extended prompt. Any escape sequences specified as part of
23519 the prompt string with @code{set extended-prompt}, are replaced with the
23520 corresponding strings each time the prompt is displayed.
23524 @section Command Editing
23526 @cindex command line editing
23528 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23529 @sc{gnu} library provides consistent behavior for programs which provide a
23530 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23531 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23532 substitution, and a storage and recall of command history across
23533 debugging sessions.
23535 You may control the behavior of command line editing in @value{GDBN} with the
23536 command @code{set}.
23539 @kindex set editing
23542 @itemx set editing on
23543 Enable command line editing (enabled by default).
23545 @item set editing off
23546 Disable command line editing.
23548 @kindex show editing
23550 Show whether command line editing is enabled.
23553 @ifset SYSTEM_READLINE
23554 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23556 @ifclear SYSTEM_READLINE
23557 @xref{Command Line Editing},
23559 for more details about the Readline
23560 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23561 encouraged to read that chapter.
23563 @node Command History
23564 @section Command History
23565 @cindex command history
23567 @value{GDBN} can keep track of the commands you type during your
23568 debugging sessions, so that you can be certain of precisely what
23569 happened. Use these commands to manage the @value{GDBN} command
23572 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23573 package, to provide the history facility.
23574 @ifset SYSTEM_READLINE
23575 @xref{Using History Interactively, , , history, GNU History Library},
23577 @ifclear SYSTEM_READLINE
23578 @xref{Using History Interactively},
23580 for the detailed description of the History library.
23582 To issue a command to @value{GDBN} without affecting certain aspects of
23583 the state which is seen by users, prefix it with @samp{server }
23584 (@pxref{Server Prefix}). This
23585 means that this command will not affect the command history, nor will it
23586 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23587 pressed on a line by itself.
23589 @cindex @code{server}, command prefix
23590 The server prefix does not affect the recording of values into the value
23591 history; to print a value without recording it into the value history,
23592 use the @code{output} command instead of the @code{print} command.
23594 Here is the description of @value{GDBN} commands related to command
23598 @cindex history substitution
23599 @cindex history file
23600 @kindex set history filename
23601 @cindex @env{GDBHISTFILE}, environment variable
23602 @item set history filename @var{fname}
23603 Set the name of the @value{GDBN} command history file to @var{fname}.
23604 This is the file where @value{GDBN} reads an initial command history
23605 list, and where it writes the command history from this session when it
23606 exits. You can access this list through history expansion or through
23607 the history command editing characters listed below. This file defaults
23608 to the value of the environment variable @code{GDBHISTFILE}, or to
23609 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23612 @cindex save command history
23613 @kindex set history save
23614 @item set history save
23615 @itemx set history save on
23616 Record command history in a file, whose name may be specified with the
23617 @code{set history filename} command. By default, this option is disabled.
23619 @item set history save off
23620 Stop recording command history in a file.
23622 @cindex history size
23623 @kindex set history size
23624 @cindex @env{GDBHISTSIZE}, environment variable
23625 @item set history size @var{size}
23626 @itemx set history size unlimited
23627 Set the number of commands which @value{GDBN} keeps in its history list.
23628 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23629 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23630 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23631 either a negative number or the empty string, then the number of commands
23632 @value{GDBN} keeps in the history list is unlimited.
23634 @cindex remove duplicate history
23635 @kindex set history remove-duplicates
23636 @item set history remove-duplicates @var{count}
23637 @itemx set history remove-duplicates unlimited
23638 Control the removal of duplicate history entries in the command history list.
23639 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23640 history entries and remove the first entry that is a duplicate of the current
23641 entry being added to the command history list. If @var{count} is
23642 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23643 removal of duplicate history entries is disabled.
23645 Only history entries added during the current session are considered for
23646 removal. This option is set to 0 by default.
23650 History expansion assigns special meaning to the character @kbd{!}.
23651 @ifset SYSTEM_READLINE
23652 @xref{Event Designators, , , history, GNU History Library},
23654 @ifclear SYSTEM_READLINE
23655 @xref{Event Designators},
23659 @cindex history expansion, turn on/off
23660 Since @kbd{!} is also the logical not operator in C, history expansion
23661 is off by default. If you decide to enable history expansion with the
23662 @code{set history expansion on} command, you may sometimes need to
23663 follow @kbd{!} (when it is used as logical not, in an expression) with
23664 a space or a tab to prevent it from being expanded. The readline
23665 history facilities do not attempt substitution on the strings
23666 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23668 The commands to control history expansion are:
23671 @item set history expansion on
23672 @itemx set history expansion
23673 @kindex set history expansion
23674 Enable history expansion. History expansion is off by default.
23676 @item set history expansion off
23677 Disable history expansion.
23680 @kindex show history
23682 @itemx show history filename
23683 @itemx show history save
23684 @itemx show history size
23685 @itemx show history expansion
23686 These commands display the state of the @value{GDBN} history parameters.
23687 @code{show history} by itself displays all four states.
23692 @kindex show commands
23693 @cindex show last commands
23694 @cindex display command history
23695 @item show commands
23696 Display the last ten commands in the command history.
23698 @item show commands @var{n}
23699 Print ten commands centered on command number @var{n}.
23701 @item show commands +
23702 Print ten commands just after the commands last printed.
23706 @section Screen Size
23707 @cindex size of screen
23708 @cindex screen size
23711 @cindex pauses in output
23713 Certain commands to @value{GDBN} may produce large amounts of
23714 information output to the screen. To help you read all of it,
23715 @value{GDBN} pauses and asks you for input at the end of each page of
23716 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23717 to discard the remaining output. Also, the screen width setting
23718 determines when to wrap lines of output. Depending on what is being
23719 printed, @value{GDBN} tries to break the line at a readable place,
23720 rather than simply letting it overflow onto the following line.
23722 Normally @value{GDBN} knows the size of the screen from the terminal
23723 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23724 together with the value of the @code{TERM} environment variable and the
23725 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23726 you can override it with the @code{set height} and @code{set
23733 @kindex show height
23734 @item set height @var{lpp}
23735 @itemx set height unlimited
23737 @itemx set width @var{cpl}
23738 @itemx set width unlimited
23740 These @code{set} commands specify a screen height of @var{lpp} lines and
23741 a screen width of @var{cpl} characters. The associated @code{show}
23742 commands display the current settings.
23744 If you specify a height of either @code{unlimited} or zero lines,
23745 @value{GDBN} does not pause during output no matter how long the
23746 output is. This is useful if output is to a file or to an editor
23749 Likewise, you can specify @samp{set width unlimited} or @samp{set
23750 width 0} to prevent @value{GDBN} from wrapping its output.
23752 @item set pagination on
23753 @itemx set pagination off
23754 @kindex set pagination
23755 Turn the output pagination on or off; the default is on. Turning
23756 pagination off is the alternative to @code{set height unlimited}. Note that
23757 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23758 Options, -batch}) also automatically disables pagination.
23760 @item show pagination
23761 @kindex show pagination
23762 Show the current pagination mode.
23767 @cindex number representation
23768 @cindex entering numbers
23770 You can always enter numbers in octal, decimal, or hexadecimal in
23771 @value{GDBN} by the usual conventions: octal numbers begin with
23772 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23773 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23774 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23775 10; likewise, the default display for numbers---when no particular
23776 format is specified---is base 10. You can change the default base for
23777 both input and output with the commands described below.
23780 @kindex set input-radix
23781 @item set input-radix @var{base}
23782 Set the default base for numeric input. Supported choices
23783 for @var{base} are decimal 8, 10, or 16. The base must itself be
23784 specified either unambiguously or using the current input radix; for
23788 set input-radix 012
23789 set input-radix 10.
23790 set input-radix 0xa
23794 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23795 leaves the input radix unchanged, no matter what it was, since
23796 @samp{10}, being without any leading or trailing signs of its base, is
23797 interpreted in the current radix. Thus, if the current radix is 16,
23798 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23801 @kindex set output-radix
23802 @item set output-radix @var{base}
23803 Set the default base for numeric display. Supported choices
23804 for @var{base} are decimal 8, 10, or 16. The base must itself be
23805 specified either unambiguously or using the current input radix.
23807 @kindex show input-radix
23808 @item show input-radix
23809 Display the current default base for numeric input.
23811 @kindex show output-radix
23812 @item show output-radix
23813 Display the current default base for numeric display.
23815 @item set radix @r{[}@var{base}@r{]}
23819 These commands set and show the default base for both input and output
23820 of numbers. @code{set radix} sets the radix of input and output to
23821 the same base; without an argument, it resets the radix back to its
23822 default value of 10.
23827 @section Configuring the Current ABI
23829 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23830 application automatically. However, sometimes you need to override its
23831 conclusions. Use these commands to manage @value{GDBN}'s view of the
23837 @cindex Newlib OS ABI and its influence on the longjmp handling
23839 One @value{GDBN} configuration can debug binaries for multiple operating
23840 system targets, either via remote debugging or native emulation.
23841 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23842 but you can override its conclusion using the @code{set osabi} command.
23843 One example where this is useful is in debugging of binaries which use
23844 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23845 not have the same identifying marks that the standard C library for your
23848 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23849 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23850 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23851 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23855 Show the OS ABI currently in use.
23858 With no argument, show the list of registered available OS ABI's.
23860 @item set osabi @var{abi}
23861 Set the current OS ABI to @var{abi}.
23864 @cindex float promotion
23866 Generally, the way that an argument of type @code{float} is passed to a
23867 function depends on whether the function is prototyped. For a prototyped
23868 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23869 according to the architecture's convention for @code{float}. For unprototyped
23870 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23871 @code{double} and then passed.
23873 Unfortunately, some forms of debug information do not reliably indicate whether
23874 a function is prototyped. If @value{GDBN} calls a function that is not marked
23875 as prototyped, it consults @kbd{set coerce-float-to-double}.
23878 @kindex set coerce-float-to-double
23879 @item set coerce-float-to-double
23880 @itemx set coerce-float-to-double on
23881 Arguments of type @code{float} will be promoted to @code{double} when passed
23882 to an unprototyped function. This is the default setting.
23884 @item set coerce-float-to-double off
23885 Arguments of type @code{float} will be passed directly to unprototyped
23888 @kindex show coerce-float-to-double
23889 @item show coerce-float-to-double
23890 Show the current setting of promoting @code{float} to @code{double}.
23894 @kindex show cp-abi
23895 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23896 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23897 used to build your application. @value{GDBN} only fully supports
23898 programs with a single C@t{++} ABI; if your program contains code using
23899 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23900 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23901 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23902 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23903 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23904 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23909 Show the C@t{++} ABI currently in use.
23912 With no argument, show the list of supported C@t{++} ABI's.
23914 @item set cp-abi @var{abi}
23915 @itemx set cp-abi auto
23916 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23920 @section Automatically loading associated files
23921 @cindex auto-loading
23923 @value{GDBN} sometimes reads files with commands and settings automatically,
23924 without being explicitly told so by the user. We call this feature
23925 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23926 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23927 results or introduce security risks (e.g., if the file comes from untrusted
23931 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23932 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23934 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23935 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23938 There are various kinds of files @value{GDBN} can automatically load.
23939 In addition to these files, @value{GDBN} supports auto-loading code written
23940 in various extension languages. @xref{Auto-loading extensions}.
23942 Note that loading of these associated files (including the local @file{.gdbinit}
23943 file) requires accordingly configured @code{auto-load safe-path}
23944 (@pxref{Auto-loading safe path}).
23946 For these reasons, @value{GDBN} includes commands and options to let you
23947 control when to auto-load files and which files should be auto-loaded.
23950 @anchor{set auto-load off}
23951 @kindex set auto-load off
23952 @item set auto-load off
23953 Globally disable loading of all auto-loaded files.
23954 You may want to use this command with the @samp{-iex} option
23955 (@pxref{Option -init-eval-command}) such as:
23957 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23960 Be aware that system init file (@pxref{System-wide configuration})
23961 and init files from your home directory (@pxref{Home Directory Init File})
23962 still get read (as they come from generally trusted directories).
23963 To prevent @value{GDBN} from auto-loading even those init files, use the
23964 @option{-nx} option (@pxref{Mode Options}), in addition to
23965 @code{set auto-load no}.
23967 @anchor{show auto-load}
23968 @kindex show auto-load
23969 @item show auto-load
23970 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23974 (gdb) show auto-load
23975 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23976 libthread-db: Auto-loading of inferior specific libthread_db is on.
23977 local-gdbinit: Auto-loading of .gdbinit script from current directory
23979 python-scripts: Auto-loading of Python scripts is on.
23980 safe-path: List of directories from which it is safe to auto-load files
23981 is $debugdir:$datadir/auto-load.
23982 scripts-directory: List of directories from which to load auto-loaded scripts
23983 is $debugdir:$datadir/auto-load.
23986 @anchor{info auto-load}
23987 @kindex info auto-load
23988 @item info auto-load
23989 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23993 (gdb) info auto-load
23996 Yes /home/user/gdb/gdb-gdb.gdb
23997 libthread-db: No auto-loaded libthread-db.
23998 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24002 Yes /home/user/gdb/gdb-gdb.py
24006 These are @value{GDBN} control commands for the auto-loading:
24008 @multitable @columnfractions .5 .5
24009 @item @xref{set auto-load off}.
24010 @tab Disable auto-loading globally.
24011 @item @xref{show auto-load}.
24012 @tab Show setting of all kinds of files.
24013 @item @xref{info auto-load}.
24014 @tab Show state of all kinds of files.
24015 @item @xref{set auto-load gdb-scripts}.
24016 @tab Control for @value{GDBN} command scripts.
24017 @item @xref{show auto-load gdb-scripts}.
24018 @tab Show setting of @value{GDBN} command scripts.
24019 @item @xref{info auto-load gdb-scripts}.
24020 @tab Show state of @value{GDBN} command scripts.
24021 @item @xref{set auto-load python-scripts}.
24022 @tab Control for @value{GDBN} Python scripts.
24023 @item @xref{show auto-load python-scripts}.
24024 @tab Show setting of @value{GDBN} Python scripts.
24025 @item @xref{info auto-load python-scripts}.
24026 @tab Show state of @value{GDBN} Python scripts.
24027 @item @xref{set auto-load guile-scripts}.
24028 @tab Control for @value{GDBN} Guile scripts.
24029 @item @xref{show auto-load guile-scripts}.
24030 @tab Show setting of @value{GDBN} Guile scripts.
24031 @item @xref{info auto-load guile-scripts}.
24032 @tab Show state of @value{GDBN} Guile scripts.
24033 @item @xref{set auto-load scripts-directory}.
24034 @tab Control for @value{GDBN} auto-loaded scripts location.
24035 @item @xref{show auto-load scripts-directory}.
24036 @tab Show @value{GDBN} auto-loaded scripts location.
24037 @item @xref{add-auto-load-scripts-directory}.
24038 @tab Add directory for auto-loaded scripts location list.
24039 @item @xref{set auto-load local-gdbinit}.
24040 @tab Control for init file in the current directory.
24041 @item @xref{show auto-load local-gdbinit}.
24042 @tab Show setting of init file in the current directory.
24043 @item @xref{info auto-load local-gdbinit}.
24044 @tab Show state of init file in the current directory.
24045 @item @xref{set auto-load libthread-db}.
24046 @tab Control for thread debugging library.
24047 @item @xref{show auto-load libthread-db}.
24048 @tab Show setting of thread debugging library.
24049 @item @xref{info auto-load libthread-db}.
24050 @tab Show state of thread debugging library.
24051 @item @xref{set auto-load safe-path}.
24052 @tab Control directories trusted for automatic loading.
24053 @item @xref{show auto-load safe-path}.
24054 @tab Show directories trusted for automatic loading.
24055 @item @xref{add-auto-load-safe-path}.
24056 @tab Add directory trusted for automatic loading.
24059 @node Init File in the Current Directory
24060 @subsection Automatically loading init file in the current directory
24061 @cindex auto-loading init file in the current directory
24063 By default, @value{GDBN} reads and executes the canned sequences of commands
24064 from init file (if any) in the current working directory,
24065 see @ref{Init File in the Current Directory during Startup}.
24067 Note that loading of this local @file{.gdbinit} file also requires accordingly
24068 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24071 @anchor{set auto-load local-gdbinit}
24072 @kindex set auto-load local-gdbinit
24073 @item set auto-load local-gdbinit [on|off]
24074 Enable or disable the auto-loading of canned sequences of commands
24075 (@pxref{Sequences}) found in init file in the current directory.
24077 @anchor{show auto-load local-gdbinit}
24078 @kindex show auto-load local-gdbinit
24079 @item show auto-load local-gdbinit
24080 Show whether auto-loading of canned sequences of commands from init file in the
24081 current directory is enabled or disabled.
24083 @anchor{info auto-load local-gdbinit}
24084 @kindex info auto-load local-gdbinit
24085 @item info auto-load local-gdbinit
24086 Print whether canned sequences of commands from init file in the
24087 current directory have been auto-loaded.
24090 @node libthread_db.so.1 file
24091 @subsection Automatically loading thread debugging library
24092 @cindex auto-loading libthread_db.so.1
24094 This feature is currently present only on @sc{gnu}/Linux native hosts.
24096 @value{GDBN} reads in some cases thread debugging library from places specific
24097 to the inferior (@pxref{set libthread-db-search-path}).
24099 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24100 without checking this @samp{set auto-load libthread-db} switch as system
24101 libraries have to be trusted in general. In all other cases of
24102 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24103 auto-load libthread-db} is enabled before trying to open such thread debugging
24106 Note that loading of this debugging library also requires accordingly configured
24107 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24110 @anchor{set auto-load libthread-db}
24111 @kindex set auto-load libthread-db
24112 @item set auto-load libthread-db [on|off]
24113 Enable or disable the auto-loading of inferior specific thread debugging library.
24115 @anchor{show auto-load libthread-db}
24116 @kindex show auto-load libthread-db
24117 @item show auto-load libthread-db
24118 Show whether auto-loading of inferior specific thread debugging library is
24119 enabled or disabled.
24121 @anchor{info auto-load libthread-db}
24122 @kindex info auto-load libthread-db
24123 @item info auto-load libthread-db
24124 Print the list of all loaded inferior specific thread debugging libraries and
24125 for each such library print list of inferior @var{pid}s using it.
24128 @node Auto-loading safe path
24129 @subsection Security restriction for auto-loading
24130 @cindex auto-loading safe-path
24132 As the files of inferior can come from untrusted source (such as submitted by
24133 an application user) @value{GDBN} does not always load any files automatically.
24134 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24135 directories trusted for loading files not explicitly requested by user.
24136 Each directory can also be a shell wildcard pattern.
24138 If the path is not set properly you will see a warning and the file will not
24143 Reading symbols from /home/user/gdb/gdb...done.
24144 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24145 declined by your `auto-load safe-path' set
24146 to "$debugdir:$datadir/auto-load".
24147 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24148 declined by your `auto-load safe-path' set
24149 to "$debugdir:$datadir/auto-load".
24153 To instruct @value{GDBN} to go ahead and use the init files anyway,
24154 invoke @value{GDBN} like this:
24157 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24160 The list of trusted directories is controlled by the following commands:
24163 @anchor{set auto-load safe-path}
24164 @kindex set auto-load safe-path
24165 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24166 Set the list of directories (and their subdirectories) trusted for automatic
24167 loading and execution of scripts. You can also enter a specific trusted file.
24168 Each directory can also be a shell wildcard pattern; wildcards do not match
24169 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24170 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24171 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24172 its default value as specified during @value{GDBN} compilation.
24174 The list of directories uses path separator (@samp{:} on GNU and Unix
24175 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24176 to the @env{PATH} environment variable.
24178 @anchor{show auto-load safe-path}
24179 @kindex show auto-load safe-path
24180 @item show auto-load safe-path
24181 Show the list of directories trusted for automatic loading and execution of
24184 @anchor{add-auto-load-safe-path}
24185 @kindex add-auto-load-safe-path
24186 @item add-auto-load-safe-path
24187 Add an entry (or list of entries) to the list of directories trusted for
24188 automatic loading and execution of scripts. Multiple entries may be delimited
24189 by the host platform path separator in use.
24192 This variable defaults to what @code{--with-auto-load-dir} has been configured
24193 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24194 substitution applies the same as for @ref{set auto-load scripts-directory}.
24195 The default @code{set auto-load safe-path} value can be also overriden by
24196 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24198 Setting this variable to @file{/} disables this security protection,
24199 corresponding @value{GDBN} configuration option is
24200 @option{--without-auto-load-safe-path}.
24201 This variable is supposed to be set to the system directories writable by the
24202 system superuser only. Users can add their source directories in init files in
24203 their home directories (@pxref{Home Directory Init File}). See also deprecated
24204 init file in the current directory
24205 (@pxref{Init File in the Current Directory during Startup}).
24207 To force @value{GDBN} to load the files it declined to load in the previous
24208 example, you could use one of the following ways:
24211 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24212 Specify this trusted directory (or a file) as additional component of the list.
24213 You have to specify also any existing directories displayed by
24214 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24216 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24217 Specify this directory as in the previous case but just for a single
24218 @value{GDBN} session.
24220 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24221 Disable auto-loading safety for a single @value{GDBN} session.
24222 This assumes all the files you debug during this @value{GDBN} session will come
24223 from trusted sources.
24225 @item @kbd{./configure --without-auto-load-safe-path}
24226 During compilation of @value{GDBN} you may disable any auto-loading safety.
24227 This assumes all the files you will ever debug with this @value{GDBN} come from
24231 On the other hand you can also explicitly forbid automatic files loading which
24232 also suppresses any such warning messages:
24235 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24236 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24238 @item @file{~/.gdbinit}: @samp{set auto-load no}
24239 Disable auto-loading globally for the user
24240 (@pxref{Home Directory Init File}). While it is improbable, you could also
24241 use system init file instead (@pxref{System-wide configuration}).
24244 This setting applies to the file names as entered by user. If no entry matches
24245 @value{GDBN} tries as a last resort to also resolve all the file names into
24246 their canonical form (typically resolving symbolic links) and compare the
24247 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24248 own before starting the comparison so a canonical form of directories is
24249 recommended to be entered.
24251 @node Auto-loading verbose mode
24252 @subsection Displaying files tried for auto-load
24253 @cindex auto-loading verbose mode
24255 For better visibility of all the file locations where you can place scripts to
24256 be auto-loaded with inferior --- or to protect yourself against accidental
24257 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24258 all the files attempted to be loaded. Both existing and non-existing files may
24261 For example the list of directories from which it is safe to auto-load files
24262 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24263 may not be too obvious while setting it up.
24266 (gdb) set debug auto-load on
24267 (gdb) file ~/src/t/true
24268 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24269 for objfile "/tmp/true".
24270 auto-load: Updating directories of "/usr:/opt".
24271 auto-load: Using directory "/usr".
24272 auto-load: Using directory "/opt".
24273 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24274 by your `auto-load safe-path' set to "/usr:/opt".
24278 @anchor{set debug auto-load}
24279 @kindex set debug auto-load
24280 @item set debug auto-load [on|off]
24281 Set whether to print the filenames attempted to be auto-loaded.
24283 @anchor{show debug auto-load}
24284 @kindex show debug auto-load
24285 @item show debug auto-load
24286 Show whether printing of the filenames attempted to be auto-loaded is turned
24290 @node Messages/Warnings
24291 @section Optional Warnings and Messages
24293 @cindex verbose operation
24294 @cindex optional warnings
24295 By default, @value{GDBN} is silent about its inner workings. If you are
24296 running on a slow machine, you may want to use the @code{set verbose}
24297 command. This makes @value{GDBN} tell you when it does a lengthy
24298 internal operation, so you will not think it has crashed.
24300 Currently, the messages controlled by @code{set verbose} are those
24301 which announce that the symbol table for a source file is being read;
24302 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24305 @kindex set verbose
24306 @item set verbose on
24307 Enables @value{GDBN} output of certain informational messages.
24309 @item set verbose off
24310 Disables @value{GDBN} output of certain informational messages.
24312 @kindex show verbose
24314 Displays whether @code{set verbose} is on or off.
24317 By default, if @value{GDBN} encounters bugs in the symbol table of an
24318 object file, it is silent; but if you are debugging a compiler, you may
24319 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24324 @kindex set complaints
24325 @item set complaints @var{limit}
24326 Permits @value{GDBN} to output @var{limit} complaints about each type of
24327 unusual symbols before becoming silent about the problem. Set
24328 @var{limit} to zero to suppress all complaints; set it to a large number
24329 to prevent complaints from being suppressed.
24331 @kindex show complaints
24332 @item show complaints
24333 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24337 @anchor{confirmation requests}
24338 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24339 lot of stupid questions to confirm certain commands. For example, if
24340 you try to run a program which is already running:
24344 The program being debugged has been started already.
24345 Start it from the beginning? (y or n)
24348 If you are willing to unflinchingly face the consequences of your own
24349 commands, you can disable this ``feature'':
24353 @kindex set confirm
24355 @cindex confirmation
24356 @cindex stupid questions
24357 @item set confirm off
24358 Disables confirmation requests. Note that running @value{GDBN} with
24359 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24360 automatically disables confirmation requests.
24362 @item set confirm on
24363 Enables confirmation requests (the default).
24365 @kindex show confirm
24367 Displays state of confirmation requests.
24371 @cindex command tracing
24372 If you need to debug user-defined commands or sourced files you may find it
24373 useful to enable @dfn{command tracing}. In this mode each command will be
24374 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24375 quantity denoting the call depth of each command.
24378 @kindex set trace-commands
24379 @cindex command scripts, debugging
24380 @item set trace-commands on
24381 Enable command tracing.
24382 @item set trace-commands off
24383 Disable command tracing.
24384 @item show trace-commands
24385 Display the current state of command tracing.
24388 @node Debugging Output
24389 @section Optional Messages about Internal Happenings
24390 @cindex optional debugging messages
24392 @value{GDBN} has commands that enable optional debugging messages from
24393 various @value{GDBN} subsystems; normally these commands are of
24394 interest to @value{GDBN} maintainers, or when reporting a bug. This
24395 section documents those commands.
24398 @kindex set exec-done-display
24399 @item set exec-done-display
24400 Turns on or off the notification of asynchronous commands'
24401 completion. When on, @value{GDBN} will print a message when an
24402 asynchronous command finishes its execution. The default is off.
24403 @kindex show exec-done-display
24404 @item show exec-done-display
24405 Displays the current setting of asynchronous command completion
24408 @cindex ARM AArch64
24409 @item set debug aarch64
24410 Turns on or off display of debugging messages related to ARM AArch64.
24411 The default is off.
24413 @item show debug aarch64
24414 Displays the current state of displaying debugging messages related to
24416 @cindex gdbarch debugging info
24417 @cindex architecture debugging info
24418 @item set debug arch
24419 Turns on or off display of gdbarch debugging info. The default is off
24420 @item show debug arch
24421 Displays the current state of displaying gdbarch debugging info.
24422 @item set debug aix-solib
24423 @cindex AIX shared library debugging
24424 Control display of debugging messages from the AIX shared library
24425 support module. The default is off.
24426 @item show debug aix-thread
24427 Show the current state of displaying AIX shared library debugging messages.
24428 @item set debug aix-thread
24429 @cindex AIX threads
24430 Display debugging messages about inner workings of the AIX thread
24432 @item show debug aix-thread
24433 Show the current state of AIX thread debugging info display.
24434 @item set debug check-physname
24436 Check the results of the ``physname'' computation. When reading DWARF
24437 debugging information for C@t{++}, @value{GDBN} attempts to compute
24438 each entity's name. @value{GDBN} can do this computation in two
24439 different ways, depending on exactly what information is present.
24440 When enabled, this setting causes @value{GDBN} to compute the names
24441 both ways and display any discrepancies.
24442 @item show debug check-physname
24443 Show the current state of ``physname'' checking.
24444 @item set debug coff-pe-read
24445 @cindex COFF/PE exported symbols
24446 Control display of debugging messages related to reading of COFF/PE
24447 exported symbols. The default is off.
24448 @item show debug coff-pe-read
24449 Displays the current state of displaying debugging messages related to
24450 reading of COFF/PE exported symbols.
24451 @item set debug dwarf-die
24453 Dump DWARF DIEs after they are read in.
24454 The value is the number of nesting levels to print.
24455 A value of zero turns off the display.
24456 @item show debug dwarf-die
24457 Show the current state of DWARF DIE debugging.
24458 @item set debug dwarf-line
24459 @cindex DWARF Line Tables
24460 Turns on or off display of debugging messages related to reading
24461 DWARF line tables. The default is 0 (off).
24462 A value of 1 provides basic information.
24463 A value greater than 1 provides more verbose information.
24464 @item show debug dwarf-line
24465 Show the current state of DWARF line table debugging.
24466 @item set debug dwarf-read
24467 @cindex DWARF Reading
24468 Turns on or off display of debugging messages related to reading
24469 DWARF debug info. The default is 0 (off).
24470 A value of 1 provides basic information.
24471 A value greater than 1 provides more verbose information.
24472 @item show debug dwarf-read
24473 Show the current state of DWARF reader debugging.
24474 @item set debug displaced
24475 @cindex displaced stepping debugging info
24476 Turns on or off display of @value{GDBN} debugging info for the
24477 displaced stepping support. The default is off.
24478 @item show debug displaced
24479 Displays the current state of displaying @value{GDBN} debugging info
24480 related to displaced stepping.
24481 @item set debug event
24482 @cindex event debugging info
24483 Turns on or off display of @value{GDBN} event debugging info. The
24485 @item show debug event
24486 Displays the current state of displaying @value{GDBN} event debugging
24488 @item set debug expression
24489 @cindex expression debugging info
24490 Turns on or off display of debugging info about @value{GDBN}
24491 expression parsing. The default is off.
24492 @item show debug expression
24493 Displays the current state of displaying debugging info about
24494 @value{GDBN} expression parsing.
24495 @item set debug fbsd-lwp
24496 @cindex FreeBSD LWP debug messages
24497 Turns on or off debugging messages from the FreeBSD LWP debug support.
24498 @item show debug fbsd-lwp
24499 Show the current state of FreeBSD LWP debugging messages.
24500 @item set debug frame
24501 @cindex frame debugging info
24502 Turns on or off display of @value{GDBN} frame debugging info. The
24504 @item show debug frame
24505 Displays the current state of displaying @value{GDBN} frame debugging
24507 @item set debug gnu-nat
24508 @cindex @sc{gnu}/Hurd debug messages
24509 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24510 @item show debug gnu-nat
24511 Show the current state of @sc{gnu}/Hurd debugging messages.
24512 @item set debug infrun
24513 @cindex inferior debugging info
24514 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24515 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24516 for implementing operations such as single-stepping the inferior.
24517 @item show debug infrun
24518 Displays the current state of @value{GDBN} inferior debugging.
24519 @item set debug jit
24520 @cindex just-in-time compilation, debugging messages
24521 Turn on or off debugging messages from JIT debug support.
24522 @item show debug jit
24523 Displays the current state of @value{GDBN} JIT debugging.
24524 @item set debug lin-lwp
24525 @cindex @sc{gnu}/Linux LWP debug messages
24526 @cindex Linux lightweight processes
24527 Turn on or off debugging messages from the Linux LWP debug support.
24528 @item show debug lin-lwp
24529 Show the current state of Linux LWP debugging messages.
24530 @item set debug linux-namespaces
24531 @cindex @sc{gnu}/Linux namespaces debug messages
24532 Turn on or off debugging messages from the Linux namespaces debug support.
24533 @item show debug linux-namespaces
24534 Show the current state of Linux namespaces debugging messages.
24535 @item set debug mach-o
24536 @cindex Mach-O symbols processing
24537 Control display of debugging messages related to Mach-O symbols
24538 processing. The default is off.
24539 @item show debug mach-o
24540 Displays the current state of displaying debugging messages related to
24541 reading of COFF/PE exported symbols.
24542 @item set debug notification
24543 @cindex remote async notification debugging info
24544 Turn on or off debugging messages about remote async notification.
24545 The default is off.
24546 @item show debug notification
24547 Displays the current state of remote async notification debugging messages.
24548 @item set debug observer
24549 @cindex observer debugging info
24550 Turns on or off display of @value{GDBN} observer debugging. This
24551 includes info such as the notification of observable events.
24552 @item show debug observer
24553 Displays the current state of observer debugging.
24554 @item set debug overload
24555 @cindex C@t{++} overload debugging info
24556 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24557 info. This includes info such as ranking of functions, etc. The default
24559 @item show debug overload
24560 Displays the current state of displaying @value{GDBN} C@t{++} overload
24562 @cindex expression parser, debugging info
24563 @cindex debug expression parser
24564 @item set debug parser
24565 Turns on or off the display of expression parser debugging output.
24566 Internally, this sets the @code{yydebug} variable in the expression
24567 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24568 details. The default is off.
24569 @item show debug parser
24570 Show the current state of expression parser debugging.
24571 @cindex packets, reporting on stdout
24572 @cindex serial connections, debugging
24573 @cindex debug remote protocol
24574 @cindex remote protocol debugging
24575 @cindex display remote packets
24576 @item set debug remote
24577 Turns on or off display of reports on all packets sent back and forth across
24578 the serial line to the remote machine. The info is printed on the
24579 @value{GDBN} standard output stream. The default is off.
24580 @item show debug remote
24581 Displays the state of display of remote packets.
24583 @item set debug separate-debug-file
24584 Turns on or off display of debug output about separate debug file search.
24585 @item show debug separate-debug-file
24586 Displays the state of separate debug file search debug output.
24588 @item set debug serial
24589 Turns on or off display of @value{GDBN} serial debugging info. The
24591 @item show debug serial
24592 Displays the current state of displaying @value{GDBN} serial debugging
24594 @item set debug solib-frv
24595 @cindex FR-V shared-library debugging
24596 Turn on or off debugging messages for FR-V shared-library code.
24597 @item show debug solib-frv
24598 Display the current state of FR-V shared-library code debugging
24600 @item set debug symbol-lookup
24601 @cindex symbol lookup
24602 Turns on or off display of debugging messages related to symbol lookup.
24603 The default is 0 (off).
24604 A value of 1 provides basic information.
24605 A value greater than 1 provides more verbose information.
24606 @item show debug symbol-lookup
24607 Show the current state of symbol lookup debugging messages.
24608 @item set debug symfile
24609 @cindex symbol file functions
24610 Turns on or off display of debugging messages related to symbol file functions.
24611 The default is off. @xref{Files}.
24612 @item show debug symfile
24613 Show the current state of symbol file debugging messages.
24614 @item set debug symtab-create
24615 @cindex symbol table creation
24616 Turns on or off display of debugging messages related to symbol table creation.
24617 The default is 0 (off).
24618 A value of 1 provides basic information.
24619 A value greater than 1 provides more verbose information.
24620 @item show debug symtab-create
24621 Show the current state of symbol table creation debugging.
24622 @item set debug target
24623 @cindex target debugging info
24624 Turns on or off display of @value{GDBN} target debugging info. This info
24625 includes what is going on at the target level of GDB, as it happens. The
24626 default is 0. Set it to 1 to track events, and to 2 to also track the
24627 value of large memory transfers.
24628 @item show debug target
24629 Displays the current state of displaying @value{GDBN} target debugging
24631 @item set debug timestamp
24632 @cindex timestampping debugging info
24633 Turns on or off display of timestamps with @value{GDBN} debugging info.
24634 When enabled, seconds and microseconds are displayed before each debugging
24636 @item show debug timestamp
24637 Displays the current state of displaying timestamps with @value{GDBN}
24639 @item set debug varobj
24640 @cindex variable object debugging info
24641 Turns on or off display of @value{GDBN} variable object debugging
24642 info. The default is off.
24643 @item show debug varobj
24644 Displays the current state of displaying @value{GDBN} variable object
24646 @item set debug xml
24647 @cindex XML parser debugging
24648 Turn on or off debugging messages for built-in XML parsers.
24649 @item show debug xml
24650 Displays the current state of XML debugging messages.
24653 @node Other Misc Settings
24654 @section Other Miscellaneous Settings
24655 @cindex miscellaneous settings
24658 @kindex set interactive-mode
24659 @item set interactive-mode
24660 If @code{on}, forces @value{GDBN} to assume that GDB was started
24661 in a terminal. In practice, this means that @value{GDBN} should wait
24662 for the user to answer queries generated by commands entered at
24663 the command prompt. If @code{off}, forces @value{GDBN} to operate
24664 in the opposite mode, and it uses the default answers to all queries.
24665 If @code{auto} (the default), @value{GDBN} tries to determine whether
24666 its standard input is a terminal, and works in interactive-mode if it
24667 is, non-interactively otherwise.
24669 In the vast majority of cases, the debugger should be able to guess
24670 correctly which mode should be used. But this setting can be useful
24671 in certain specific cases, such as running a MinGW @value{GDBN}
24672 inside a cygwin window.
24674 @kindex show interactive-mode
24675 @item show interactive-mode
24676 Displays whether the debugger is operating in interactive mode or not.
24679 @node Extending GDB
24680 @chapter Extending @value{GDBN}
24681 @cindex extending GDB
24683 @value{GDBN} provides several mechanisms for extension.
24684 @value{GDBN} also provides the ability to automatically load
24685 extensions when it reads a file for debugging. This allows the
24686 user to automatically customize @value{GDBN} for the program
24690 * Sequences:: Canned Sequences of @value{GDBN} Commands
24691 * Python:: Extending @value{GDBN} using Python
24692 * Guile:: Extending @value{GDBN} using Guile
24693 * Auto-loading extensions:: Automatically loading extensions
24694 * Multiple Extension Languages:: Working with multiple extension languages
24695 * Aliases:: Creating new spellings of existing commands
24698 To facilitate the use of extension languages, @value{GDBN} is capable
24699 of evaluating the contents of a file. When doing so, @value{GDBN}
24700 can recognize which extension language is being used by looking at
24701 the filename extension. Files with an unrecognized filename extension
24702 are always treated as a @value{GDBN} Command Files.
24703 @xref{Command Files,, Command files}.
24705 You can control how @value{GDBN} evaluates these files with the following
24709 @kindex set script-extension
24710 @kindex show script-extension
24711 @item set script-extension off
24712 All scripts are always evaluated as @value{GDBN} Command Files.
24714 @item set script-extension soft
24715 The debugger determines the scripting language based on filename
24716 extension. If this scripting language is supported, @value{GDBN}
24717 evaluates the script using that language. Otherwise, it evaluates
24718 the file as a @value{GDBN} Command File.
24720 @item set script-extension strict
24721 The debugger determines the scripting language based on filename
24722 extension, and evaluates the script using that language. If the
24723 language is not supported, then the evaluation fails.
24725 @item show script-extension
24726 Display the current value of the @code{script-extension} option.
24731 @section Canned Sequences of Commands
24733 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24734 Command Lists}), @value{GDBN} provides two ways to store sequences of
24735 commands for execution as a unit: user-defined commands and command
24739 * Define:: How to define your own commands
24740 * Hooks:: Hooks for user-defined commands
24741 * Command Files:: How to write scripts of commands to be stored in a file
24742 * Output:: Commands for controlled output
24743 * Auto-loading sequences:: Controlling auto-loaded command files
24747 @subsection User-defined Commands
24749 @cindex user-defined command
24750 @cindex arguments, to user-defined commands
24751 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24752 which you assign a new name as a command. This is done with the
24753 @code{define} command. User commands may accept an unlimited number of arguments
24754 separated by whitespace. Arguments are accessed within the user command
24755 via @code{$arg0@dots{}$argN}. A trivial example:
24759 print $arg0 + $arg1 + $arg2
24764 To execute the command use:
24771 This defines the command @code{adder}, which prints the sum of
24772 its three arguments. Note the arguments are text substitutions, so they may
24773 reference variables, use complex expressions, or even perform inferior
24776 @cindex argument count in user-defined commands
24777 @cindex how many arguments (user-defined commands)
24778 In addition, @code{$argc} may be used to find out how many arguments have
24784 print $arg0 + $arg1
24787 print $arg0 + $arg1 + $arg2
24792 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24793 to process a variable number of arguments:
24800 eval "set $sum = $sum + $arg%d", $i
24810 @item define @var{commandname}
24811 Define a command named @var{commandname}. If there is already a command
24812 by that name, you are asked to confirm that you want to redefine it.
24813 The argument @var{commandname} may be a bare command name consisting of letters,
24814 numbers, dashes, and underscores. It may also start with any predefined
24815 prefix command. For example, @samp{define target my-target} creates
24816 a user-defined @samp{target my-target} command.
24818 The definition of the command is made up of other @value{GDBN} command lines,
24819 which are given following the @code{define} command. The end of these
24820 commands is marked by a line containing @code{end}.
24823 @kindex end@r{ (user-defined commands)}
24824 @item document @var{commandname}
24825 Document the user-defined command @var{commandname}, so that it can be
24826 accessed by @code{help}. The command @var{commandname} must already be
24827 defined. This command reads lines of documentation just as @code{define}
24828 reads the lines of the command definition, ending with @code{end}.
24829 After the @code{document} command is finished, @code{help} on command
24830 @var{commandname} displays the documentation you have written.
24832 You may use the @code{document} command again to change the
24833 documentation of a command. Redefining the command with @code{define}
24834 does not change the documentation.
24836 @kindex dont-repeat
24837 @cindex don't repeat command
24839 Used inside a user-defined command, this tells @value{GDBN} that this
24840 command should not be repeated when the user hits @key{RET}
24841 (@pxref{Command Syntax, repeat last command}).
24843 @kindex help user-defined
24844 @item help user-defined
24845 List all user-defined commands and all python commands defined in class
24846 COMAND_USER. The first line of the documentation or docstring is
24851 @itemx show user @var{commandname}
24852 Display the @value{GDBN} commands used to define @var{commandname} (but
24853 not its documentation). If no @var{commandname} is given, display the
24854 definitions for all user-defined commands.
24855 This does not work for user-defined python commands.
24857 @cindex infinite recursion in user-defined commands
24858 @kindex show max-user-call-depth
24859 @kindex set max-user-call-depth
24860 @item show max-user-call-depth
24861 @itemx set max-user-call-depth
24862 The value of @code{max-user-call-depth} controls how many recursion
24863 levels are allowed in user-defined commands before @value{GDBN} suspects an
24864 infinite recursion and aborts the command.
24865 This does not apply to user-defined python commands.
24868 In addition to the above commands, user-defined commands frequently
24869 use control flow commands, described in @ref{Command Files}.
24871 When user-defined commands are executed, the
24872 commands of the definition are not printed. An error in any command
24873 stops execution of the user-defined command.
24875 If used interactively, commands that would ask for confirmation proceed
24876 without asking when used inside a user-defined command. Many @value{GDBN}
24877 commands that normally print messages to say what they are doing omit the
24878 messages when used in a user-defined command.
24881 @subsection User-defined Command Hooks
24882 @cindex command hooks
24883 @cindex hooks, for commands
24884 @cindex hooks, pre-command
24887 You may define @dfn{hooks}, which are a special kind of user-defined
24888 command. Whenever you run the command @samp{foo}, if the user-defined
24889 command @samp{hook-foo} exists, it is executed (with no arguments)
24890 before that command.
24892 @cindex hooks, post-command
24894 A hook may also be defined which is run after the command you executed.
24895 Whenever you run the command @samp{foo}, if the user-defined command
24896 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24897 that command. Post-execution hooks may exist simultaneously with
24898 pre-execution hooks, for the same command.
24900 It is valid for a hook to call the command which it hooks. If this
24901 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24903 @c It would be nice if hookpost could be passed a parameter indicating
24904 @c if the command it hooks executed properly or not. FIXME!
24906 @kindex stop@r{, a pseudo-command}
24907 In addition, a pseudo-command, @samp{stop} exists. Defining
24908 (@samp{hook-stop}) makes the associated commands execute every time
24909 execution stops in your program: before breakpoint commands are run,
24910 displays are printed, or the stack frame is printed.
24912 For example, to ignore @code{SIGALRM} signals while
24913 single-stepping, but treat them normally during normal execution,
24918 handle SIGALRM nopass
24922 handle SIGALRM pass
24925 define hook-continue
24926 handle SIGALRM pass
24930 As a further example, to hook at the beginning and end of the @code{echo}
24931 command, and to add extra text to the beginning and end of the message,
24939 define hookpost-echo
24943 (@value{GDBP}) echo Hello World
24944 <<<---Hello World--->>>
24949 You can define a hook for any single-word command in @value{GDBN}, but
24950 not for command aliases; you should define a hook for the basic command
24951 name, e.g.@: @code{backtrace} rather than @code{bt}.
24952 @c FIXME! So how does Joe User discover whether a command is an alias
24954 You can hook a multi-word command by adding @code{hook-} or
24955 @code{hookpost-} to the last word of the command, e.g.@:
24956 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24958 If an error occurs during the execution of your hook, execution of
24959 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24960 (before the command that you actually typed had a chance to run).
24962 If you try to define a hook which does not match any known command, you
24963 get a warning from the @code{define} command.
24965 @node Command Files
24966 @subsection Command Files
24968 @cindex command files
24969 @cindex scripting commands
24970 A command file for @value{GDBN} is a text file made of lines that are
24971 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24972 also be included. An empty line in a command file does nothing; it
24973 does not mean to repeat the last command, as it would from the
24976 You can request the execution of a command file with the @code{source}
24977 command. Note that the @code{source} command is also used to evaluate
24978 scripts that are not Command Files. The exact behavior can be configured
24979 using the @code{script-extension} setting.
24980 @xref{Extending GDB,, Extending GDB}.
24984 @cindex execute commands from a file
24985 @item source [-s] [-v] @var{filename}
24986 Execute the command file @var{filename}.
24989 The lines in a command file are generally executed sequentially,
24990 unless the order of execution is changed by one of the
24991 @emph{flow-control commands} described below. The commands are not
24992 printed as they are executed. An error in any command terminates
24993 execution of the command file and control is returned to the console.
24995 @value{GDBN} first searches for @var{filename} in the current directory.
24996 If the file is not found there, and @var{filename} does not specify a
24997 directory, then @value{GDBN} also looks for the file on the source search path
24998 (specified with the @samp{directory} command);
24999 except that @file{$cdir} is not searched because the compilation directory
25000 is not relevant to scripts.
25002 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25003 on the search path even if @var{filename} specifies a directory.
25004 The search is done by appending @var{filename} to each element of the
25005 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25006 and the search path contains @file{/home/user} then @value{GDBN} will
25007 look for the script @file{/home/user/mylib/myscript}.
25008 The search is also done if @var{filename} is an absolute path.
25009 For example, if @var{filename} is @file{/tmp/myscript} and
25010 the search path contains @file{/home/user} then @value{GDBN} will
25011 look for the script @file{/home/user/tmp/myscript}.
25012 For DOS-like systems, if @var{filename} contains a drive specification,
25013 it is stripped before concatenation. For example, if @var{filename} is
25014 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25015 will look for the script @file{c:/tmp/myscript}.
25017 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25018 each command as it is executed. The option must be given before
25019 @var{filename}, and is interpreted as part of the filename anywhere else.
25021 Commands that would ask for confirmation if used interactively proceed
25022 without asking when used in a command file. Many @value{GDBN} commands that
25023 normally print messages to say what they are doing omit the messages
25024 when called from command files.
25026 @value{GDBN} also accepts command input from standard input. In this
25027 mode, normal output goes to standard output and error output goes to
25028 standard error. Errors in a command file supplied on standard input do
25029 not terminate execution of the command file---execution continues with
25033 gdb < cmds > log 2>&1
25036 (The syntax above will vary depending on the shell used.) This example
25037 will execute commands from the file @file{cmds}. All output and errors
25038 would be directed to @file{log}.
25040 Since commands stored on command files tend to be more general than
25041 commands typed interactively, they frequently need to deal with
25042 complicated situations, such as different or unexpected values of
25043 variables and symbols, changes in how the program being debugged is
25044 built, etc. @value{GDBN} provides a set of flow-control commands to
25045 deal with these complexities. Using these commands, you can write
25046 complex scripts that loop over data structures, execute commands
25047 conditionally, etc.
25054 This command allows to include in your script conditionally executed
25055 commands. The @code{if} command takes a single argument, which is an
25056 expression to evaluate. It is followed by a series of commands that
25057 are executed only if the expression is true (its value is nonzero).
25058 There can then optionally be an @code{else} line, followed by a series
25059 of commands that are only executed if the expression was false. The
25060 end of the list is marked by a line containing @code{end}.
25064 This command allows to write loops. Its syntax is similar to
25065 @code{if}: the command takes a single argument, which is an expression
25066 to evaluate, and must be followed by the commands to execute, one per
25067 line, terminated by an @code{end}. These commands are called the
25068 @dfn{body} of the loop. The commands in the body of @code{while} are
25069 executed repeatedly as long as the expression evaluates to true.
25073 This command exits the @code{while} loop in whose body it is included.
25074 Execution of the script continues after that @code{while}s @code{end}
25077 @kindex loop_continue
25078 @item loop_continue
25079 This command skips the execution of the rest of the body of commands
25080 in the @code{while} loop in whose body it is included. Execution
25081 branches to the beginning of the @code{while} loop, where it evaluates
25082 the controlling expression.
25084 @kindex end@r{ (if/else/while commands)}
25086 Terminate the block of commands that are the body of @code{if},
25087 @code{else}, or @code{while} flow-control commands.
25092 @subsection Commands for Controlled Output
25094 During the execution of a command file or a user-defined command, normal
25095 @value{GDBN} output is suppressed; the only output that appears is what is
25096 explicitly printed by the commands in the definition. This section
25097 describes three commands useful for generating exactly the output you
25102 @item echo @var{text}
25103 @c I do not consider backslash-space a standard C escape sequence
25104 @c because it is not in ANSI.
25105 Print @var{text}. Nonprinting characters can be included in
25106 @var{text} using C escape sequences, such as @samp{\n} to print a
25107 newline. @strong{No newline is printed unless you specify one.}
25108 In addition to the standard C escape sequences, a backslash followed
25109 by a space stands for a space. This is useful for displaying a
25110 string with spaces at the beginning or the end, since leading and
25111 trailing spaces are otherwise trimmed from all arguments.
25112 To print @samp{@w{ }and foo =@w{ }}, use the command
25113 @samp{echo \@w{ }and foo = \@w{ }}.
25115 A backslash at the end of @var{text} can be used, as in C, to continue
25116 the command onto subsequent lines. For example,
25119 echo This is some text\n\
25120 which is continued\n\
25121 onto several lines.\n
25124 produces the same output as
25127 echo This is some text\n
25128 echo which is continued\n
25129 echo onto several lines.\n
25133 @item output @var{expression}
25134 Print the value of @var{expression} and nothing but that value: no
25135 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25136 value history either. @xref{Expressions, ,Expressions}, for more information
25139 @item output/@var{fmt} @var{expression}
25140 Print the value of @var{expression} in format @var{fmt}. You can use
25141 the same formats as for @code{print}. @xref{Output Formats,,Output
25142 Formats}, for more information.
25145 @item printf @var{template}, @var{expressions}@dots{}
25146 Print the values of one or more @var{expressions} under the control of
25147 the string @var{template}. To print several values, make
25148 @var{expressions} be a comma-separated list of individual expressions,
25149 which may be either numbers or pointers. Their values are printed as
25150 specified by @var{template}, exactly as a C program would do by
25151 executing the code below:
25154 printf (@var{template}, @var{expressions}@dots{});
25157 As in @code{C} @code{printf}, ordinary characters in @var{template}
25158 are printed verbatim, while @dfn{conversion specification} introduced
25159 by the @samp{%} character cause subsequent @var{expressions} to be
25160 evaluated, their values converted and formatted according to type and
25161 style information encoded in the conversion specifications, and then
25164 For example, you can print two values in hex like this:
25167 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25170 @code{printf} supports all the standard @code{C} conversion
25171 specifications, including the flags and modifiers between the @samp{%}
25172 character and the conversion letter, with the following exceptions:
25176 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25179 The modifier @samp{*} is not supported for specifying precision or
25183 The @samp{'} flag (for separation of digits into groups according to
25184 @code{LC_NUMERIC'}) is not supported.
25187 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25191 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25194 The conversion letters @samp{a} and @samp{A} are not supported.
25198 Note that the @samp{ll} type modifier is supported only if the
25199 underlying @code{C} implementation used to build @value{GDBN} supports
25200 the @code{long long int} type, and the @samp{L} type modifier is
25201 supported only if @code{long double} type is available.
25203 As in @code{C}, @code{printf} supports simple backslash-escape
25204 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25205 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25206 single character. Octal and hexadecimal escape sequences are not
25209 Additionally, @code{printf} supports conversion specifications for DFP
25210 (@dfn{Decimal Floating Point}) types using the following length modifiers
25211 together with a floating point specifier.
25216 @samp{H} for printing @code{Decimal32} types.
25219 @samp{D} for printing @code{Decimal64} types.
25222 @samp{DD} for printing @code{Decimal128} types.
25225 If the underlying @code{C} implementation used to build @value{GDBN} has
25226 support for the three length modifiers for DFP types, other modifiers
25227 such as width and precision will also be available for @value{GDBN} to use.
25229 In case there is no such @code{C} support, no additional modifiers will be
25230 available and the value will be printed in the standard way.
25232 Here's an example of printing DFP types using the above conversion letters:
25234 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25239 @item eval @var{template}, @var{expressions}@dots{}
25240 Convert the values of one or more @var{expressions} under the control of
25241 the string @var{template} to a command line, and call it.
25245 @node Auto-loading sequences
25246 @subsection Controlling auto-loading native @value{GDBN} scripts
25247 @cindex native script auto-loading
25249 When a new object file is read (for example, due to the @code{file}
25250 command, or because the inferior has loaded a shared library),
25251 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25252 @xref{Auto-loading extensions}.
25254 Auto-loading can be enabled or disabled,
25255 and the list of auto-loaded scripts can be printed.
25258 @anchor{set auto-load gdb-scripts}
25259 @kindex set auto-load gdb-scripts
25260 @item set auto-load gdb-scripts [on|off]
25261 Enable or disable the auto-loading of canned sequences of commands scripts.
25263 @anchor{show auto-load gdb-scripts}
25264 @kindex show auto-load gdb-scripts
25265 @item show auto-load gdb-scripts
25266 Show whether auto-loading of canned sequences of commands scripts is enabled or
25269 @anchor{info auto-load gdb-scripts}
25270 @kindex info auto-load gdb-scripts
25271 @cindex print list of auto-loaded canned sequences of commands scripts
25272 @item info auto-load gdb-scripts [@var{regexp}]
25273 Print the list of all canned sequences of commands scripts that @value{GDBN}
25277 If @var{regexp} is supplied only canned sequences of commands scripts with
25278 matching names are printed.
25280 @c Python docs live in a separate file.
25281 @include python.texi
25283 @c Guile docs live in a separate file.
25284 @include guile.texi
25286 @node Auto-loading extensions
25287 @section Auto-loading extensions
25288 @cindex auto-loading extensions
25290 @value{GDBN} provides two mechanisms for automatically loading extensions
25291 when a new object file is read (for example, due to the @code{file}
25292 command, or because the inferior has loaded a shared library):
25293 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25294 section of modern file formats like ELF.
25297 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25298 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25299 * Which flavor to choose?::
25302 The auto-loading feature is useful for supplying application-specific
25303 debugging commands and features.
25305 Auto-loading can be enabled or disabled,
25306 and the list of auto-loaded scripts can be printed.
25307 See the @samp{auto-loading} section of each extension language
25308 for more information.
25309 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25310 For Python files see @ref{Python Auto-loading}.
25312 Note that loading of this script file also requires accordingly configured
25313 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25315 @node objfile-gdbdotext file
25316 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25317 @cindex @file{@var{objfile}-gdb.gdb}
25318 @cindex @file{@var{objfile}-gdb.py}
25319 @cindex @file{@var{objfile}-gdb.scm}
25321 When a new object file is read, @value{GDBN} looks for a file named
25322 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25323 where @var{objfile} is the object file's name and
25324 where @var{ext} is the file extension for the extension language:
25327 @item @file{@var{objfile}-gdb.gdb}
25328 GDB's own command language
25329 @item @file{@var{objfile}-gdb.py}
25331 @item @file{@var{objfile}-gdb.scm}
25335 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25336 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25337 components, and appending the @file{-gdb.@var{ext}} suffix.
25338 If this file exists and is readable, @value{GDBN} will evaluate it as a
25339 script in the specified extension language.
25341 If this file does not exist, then @value{GDBN} will look for
25342 @var{script-name} file in all of the directories as specified below.
25344 Note that loading of these files requires an accordingly configured
25345 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25347 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25348 scripts normally according to its @file{.exe} filename. But if no scripts are
25349 found @value{GDBN} also tries script filenames matching the object file without
25350 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25351 is attempted on any platform. This makes the script filenames compatible
25352 between Unix and MS-Windows hosts.
25355 @anchor{set auto-load scripts-directory}
25356 @kindex set auto-load scripts-directory
25357 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25358 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25359 may be delimited by the host platform path separator in use
25360 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25362 Each entry here needs to be covered also by the security setting
25363 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25365 @anchor{with-auto-load-dir}
25366 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25367 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25368 configuration option @option{--with-auto-load-dir}.
25370 Any reference to @file{$debugdir} will get replaced by
25371 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25372 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25373 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25374 @file{$datadir} must be placed as a directory component --- either alone or
25375 delimited by @file{/} or @file{\} directory separators, depending on the host
25378 The list of directories uses path separator (@samp{:} on GNU and Unix
25379 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25380 to the @env{PATH} environment variable.
25382 @anchor{show auto-load scripts-directory}
25383 @kindex show auto-load scripts-directory
25384 @item show auto-load scripts-directory
25385 Show @value{GDBN} auto-loaded scripts location.
25387 @anchor{add-auto-load-scripts-directory}
25388 @kindex add-auto-load-scripts-directory
25389 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25390 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25391 Multiple entries may be delimited by the host platform path separator in use.
25394 @value{GDBN} does not track which files it has already auto-loaded this way.
25395 @value{GDBN} will load the associated script every time the corresponding
25396 @var{objfile} is opened.
25397 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25398 is evaluated more than once.
25400 @node dotdebug_gdb_scripts section
25401 @subsection The @code{.debug_gdb_scripts} section
25402 @cindex @code{.debug_gdb_scripts} section
25404 For systems using file formats like ELF and COFF,
25405 when @value{GDBN} loads a new object file
25406 it will look for a special section named @code{.debug_gdb_scripts}.
25407 If this section exists, its contents is a list of null-terminated entries
25408 specifying scripts to load. Each entry begins with a non-null prefix byte that
25409 specifies the kind of entry, typically the extension language and whether the
25410 script is in a file or inlined in @code{.debug_gdb_scripts}.
25412 The following entries are supported:
25415 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25416 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25417 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25418 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25421 @subsubsection Script File Entries
25423 If the entry specifies a file, @value{GDBN} will look for the file first
25424 in the current directory and then along the source search path
25425 (@pxref{Source Path, ,Specifying Source Directories}),
25426 except that @file{$cdir} is not searched, since the compilation
25427 directory is not relevant to scripts.
25429 File entries can be placed in section @code{.debug_gdb_scripts} with,
25430 for example, this GCC macro for Python scripts.
25433 /* Note: The "MS" section flags are to remove duplicates. */
25434 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25436 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25437 .byte 1 /* Python */\n\
25438 .asciz \"" script_name "\"\n\
25444 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25445 Then one can reference the macro in a header or source file like this:
25448 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25451 The script name may include directories if desired.
25453 Note that loading of this script file also requires accordingly configured
25454 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25456 If the macro invocation is put in a header, any application or library
25457 using this header will get a reference to the specified script,
25458 and with the use of @code{"MS"} attributes on the section, the linker
25459 will remove duplicates.
25461 @subsubsection Script Text Entries
25463 Script text entries allow to put the executable script in the entry
25464 itself instead of loading it from a file.
25465 The first line of the entry, everything after the prefix byte and up to
25466 the first newline (@code{0xa}) character, is the script name, and must not
25467 contain any kind of space character, e.g., spaces or tabs.
25468 The rest of the entry, up to the trailing null byte, is the script to
25469 execute in the specified language. The name needs to be unique among
25470 all script names, as @value{GDBN} executes each script only once based
25473 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25477 #include "symcat.h"
25478 #include "gdb/section-scripts.h"
25480 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25481 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25482 ".ascii \"gdb.inlined-script\\n\"\n"
25483 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25484 ".ascii \" def __init__ (self):\\n\"\n"
25485 ".ascii \" super (test_cmd, self).__init__ ("
25486 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25487 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25488 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25489 ".ascii \"test_cmd ()\\n\"\n"
25495 Loading of inlined scripts requires a properly configured
25496 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25497 The path to specify in @code{auto-load safe-path} is the path of the file
25498 containing the @code{.debug_gdb_scripts} section.
25500 @node Which flavor to choose?
25501 @subsection Which flavor to choose?
25503 Given the multiple ways of auto-loading extensions, it might not always
25504 be clear which one to choose. This section provides some guidance.
25507 Benefits of the @file{-gdb.@var{ext}} way:
25511 Can be used with file formats that don't support multiple sections.
25514 Ease of finding scripts for public libraries.
25516 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25517 in the source search path.
25518 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25519 isn't a source directory in which to find the script.
25522 Doesn't require source code additions.
25526 Benefits of the @code{.debug_gdb_scripts} way:
25530 Works with static linking.
25532 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25533 trigger their loading. When an application is statically linked the only
25534 objfile available is the executable, and it is cumbersome to attach all the
25535 scripts from all the input libraries to the executable's
25536 @file{-gdb.@var{ext}} script.
25539 Works with classes that are entirely inlined.
25541 Some classes can be entirely inlined, and thus there may not be an associated
25542 shared library to attach a @file{-gdb.@var{ext}} script to.
25545 Scripts needn't be copied out of the source tree.
25547 In some circumstances, apps can be built out of large collections of internal
25548 libraries, and the build infrastructure necessary to install the
25549 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25550 cumbersome. It may be easier to specify the scripts in the
25551 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25552 top of the source tree to the source search path.
25555 @node Multiple Extension Languages
25556 @section Multiple Extension Languages
25558 The Guile and Python extension languages do not share any state,
25559 and generally do not interfere with each other.
25560 There are some things to be aware of, however.
25562 @subsection Python comes first
25564 Python was @value{GDBN}'s first extension language, and to avoid breaking
25565 existing behaviour Python comes first. This is generally solved by the
25566 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25567 extension languages, and when it makes a call to an extension language,
25568 (say to pretty-print a value), it tries each in turn until an extension
25569 language indicates it has performed the request (e.g., has returned the
25570 pretty-printed form of a value).
25571 This extends to errors while performing such requests: If an error happens
25572 while, for example, trying to pretty-print an object then the error is
25573 reported and any following extension languages are not tried.
25576 @section Creating new spellings of existing commands
25577 @cindex aliases for commands
25579 It is often useful to define alternate spellings of existing commands.
25580 For example, if a new @value{GDBN} command defined in Python has
25581 a long name to type, it is handy to have an abbreviated version of it
25582 that involves less typing.
25584 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25585 of the @samp{step} command even though it is otherwise an ambiguous
25586 abbreviation of other commands like @samp{set} and @samp{show}.
25588 Aliases are also used to provide shortened or more common versions
25589 of multi-word commands. For example, @value{GDBN} provides the
25590 @samp{tty} alias of the @samp{set inferior-tty} command.
25592 You can define a new alias with the @samp{alias} command.
25597 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25601 @var{ALIAS} specifies the name of the new alias.
25602 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25605 @var{COMMAND} specifies the name of an existing command
25606 that is being aliased.
25608 The @samp{-a} option specifies that the new alias is an abbreviation
25609 of the command. Abbreviations are not shown in command
25610 lists displayed by the @samp{help} command.
25612 The @samp{--} option specifies the end of options,
25613 and is useful when @var{ALIAS} begins with a dash.
25615 Here is a simple example showing how to make an abbreviation
25616 of a command so that there is less to type.
25617 Suppose you were tired of typing @samp{disas}, the current
25618 shortest unambiguous abbreviation of the @samp{disassemble} command
25619 and you wanted an even shorter version named @samp{di}.
25620 The following will accomplish this.
25623 (gdb) alias -a di = disas
25626 Note that aliases are different from user-defined commands.
25627 With a user-defined command, you also need to write documentation
25628 for it with the @samp{document} command.
25629 An alias automatically picks up the documentation of the existing command.
25631 Here is an example where we make @samp{elms} an abbreviation of
25632 @samp{elements} in the @samp{set print elements} command.
25633 This is to show that you can make an abbreviation of any part
25637 (gdb) alias -a set print elms = set print elements
25638 (gdb) alias -a show print elms = show print elements
25639 (gdb) set p elms 20
25641 Limit on string chars or array elements to print is 200.
25644 Note that if you are defining an alias of a @samp{set} command,
25645 and you want to have an alias for the corresponding @samp{show}
25646 command, then you need to define the latter separately.
25648 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25649 @var{ALIAS}, just as they are normally.
25652 (gdb) alias -a set pr elms = set p ele
25655 Finally, here is an example showing the creation of a one word
25656 alias for a more complex command.
25657 This creates alias @samp{spe} of the command @samp{set print elements}.
25660 (gdb) alias spe = set print elements
25665 @chapter Command Interpreters
25666 @cindex command interpreters
25668 @value{GDBN} supports multiple command interpreters, and some command
25669 infrastructure to allow users or user interface writers to switch
25670 between interpreters or run commands in other interpreters.
25672 @value{GDBN} currently supports two command interpreters, the console
25673 interpreter (sometimes called the command-line interpreter or @sc{cli})
25674 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25675 describes both of these interfaces in great detail.
25677 By default, @value{GDBN} will start with the console interpreter.
25678 However, the user may choose to start @value{GDBN} with another
25679 interpreter by specifying the @option{-i} or @option{--interpreter}
25680 startup options. Defined interpreters include:
25684 @cindex console interpreter
25685 The traditional console or command-line interpreter. This is the most often
25686 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25687 @value{GDBN} will use this interpreter.
25690 @cindex mi interpreter
25691 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25692 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25693 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25697 @cindex mi2 interpreter
25698 The current @sc{gdb/mi} interface.
25701 @cindex mi1 interpreter
25702 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25706 @cindex invoke another interpreter
25708 @kindex interpreter-exec
25709 You may execute commands in any interpreter from the current
25710 interpreter using the appropriate command. If you are running the
25711 console interpreter, simply use the @code{interpreter-exec} command:
25714 interpreter-exec mi "-data-list-register-names"
25717 @sc{gdb/mi} has a similar command, although it is only available in versions of
25718 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25720 Note that @code{interpreter-exec} only changes the interpreter for the
25721 duration of the specified command. It does not change the interpreter
25724 @cindex start a new independent interpreter
25726 Although you may only choose a single interpreter at startup, it is
25727 possible to run an independent interpreter on a specified input/output
25728 device (usually a tty).
25730 For example, consider a debugger GUI or IDE that wants to provide a
25731 @value{GDBN} console view. It may do so by embedding a terminal
25732 emulator widget in its GUI, starting @value{GDBN} in the traditional
25733 command-line mode with stdin/stdout/stderr redirected to that
25734 terminal, and then creating an MI interpreter running on a specified
25735 input/output device. The console interpreter created by @value{GDBN}
25736 at startup handles commands the user types in the terminal widget,
25737 while the GUI controls and synchronizes state with @value{GDBN} using
25738 the separate MI interpreter.
25740 To start a new secondary @dfn{user interface} running MI, use the
25741 @code{new-ui} command:
25744 @cindex new user interface
25746 new-ui @var{interpreter} @var{tty}
25749 The @var{interpreter} parameter specifies the interpreter to run.
25750 This accepts the same values as the @code{interpreter-exec} command.
25751 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25752 @var{tty} parameter specifies the name of the bidirectional file the
25753 interpreter uses for input/output, usually the name of a
25754 pseudoterminal slave on Unix systems. For example:
25757 (@value{GDBP}) new-ui mi /dev/pts/9
25761 runs an MI interpreter on @file{/dev/pts/9}.
25764 @chapter @value{GDBN} Text User Interface
25766 @cindex Text User Interface
25769 * TUI Overview:: TUI overview
25770 * TUI Keys:: TUI key bindings
25771 * TUI Single Key Mode:: TUI single key mode
25772 * TUI Commands:: TUI-specific commands
25773 * TUI Configuration:: TUI configuration variables
25776 The @value{GDBN} Text User Interface (TUI) is a terminal
25777 interface which uses the @code{curses} library to show the source
25778 file, the assembly output, the program registers and @value{GDBN}
25779 commands in separate text windows. The TUI mode is supported only
25780 on platforms where a suitable version of the @code{curses} library
25783 The TUI mode is enabled by default when you invoke @value{GDBN} as
25784 @samp{@value{GDBP} -tui}.
25785 You can also switch in and out of TUI mode while @value{GDBN} runs by
25786 using various TUI commands and key bindings, such as @command{tui
25787 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25788 @ref{TUI Keys, ,TUI Key Bindings}.
25791 @section TUI Overview
25793 In TUI mode, @value{GDBN} can display several text windows:
25797 This window is the @value{GDBN} command window with the @value{GDBN}
25798 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25799 managed using readline.
25802 The source window shows the source file of the program. The current
25803 line and active breakpoints are displayed in this window.
25806 The assembly window shows the disassembly output of the program.
25809 This window shows the processor registers. Registers are highlighted
25810 when their values change.
25813 The source and assembly windows show the current program position
25814 by highlighting the current line and marking it with a @samp{>} marker.
25815 Breakpoints are indicated with two markers. The first marker
25816 indicates the breakpoint type:
25820 Breakpoint which was hit at least once.
25823 Breakpoint which was never hit.
25826 Hardware breakpoint which was hit at least once.
25829 Hardware breakpoint which was never hit.
25832 The second marker indicates whether the breakpoint is enabled or not:
25836 Breakpoint is enabled.
25839 Breakpoint is disabled.
25842 The source, assembly and register windows are updated when the current
25843 thread changes, when the frame changes, or when the program counter
25846 These windows are not all visible at the same time. The command
25847 window is always visible. The others can be arranged in several
25858 source and assembly,
25861 source and registers, or
25864 assembly and registers.
25867 A status line above the command window shows the following information:
25871 Indicates the current @value{GDBN} target.
25872 (@pxref{Targets, ,Specifying a Debugging Target}).
25875 Gives the current process or thread number.
25876 When no process is being debugged, this field is set to @code{No process}.
25879 Gives the current function name for the selected frame.
25880 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25881 When there is no symbol corresponding to the current program counter,
25882 the string @code{??} is displayed.
25885 Indicates the current line number for the selected frame.
25886 When the current line number is not known, the string @code{??} is displayed.
25889 Indicates the current program counter address.
25893 @section TUI Key Bindings
25894 @cindex TUI key bindings
25896 The TUI installs several key bindings in the readline keymaps
25897 @ifset SYSTEM_READLINE
25898 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25900 @ifclear SYSTEM_READLINE
25901 (@pxref{Command Line Editing}).
25903 The following key bindings are installed for both TUI mode and the
25904 @value{GDBN} standard mode.
25913 Enter or leave the TUI mode. When leaving the TUI mode,
25914 the curses window management stops and @value{GDBN} operates using
25915 its standard mode, writing on the terminal directly. When reentering
25916 the TUI mode, control is given back to the curses windows.
25917 The screen is then refreshed.
25921 Use a TUI layout with only one window. The layout will
25922 either be @samp{source} or @samp{assembly}. When the TUI mode
25923 is not active, it will switch to the TUI mode.
25925 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25929 Use a TUI layout with at least two windows. When the current
25930 layout already has two windows, the next layout with two windows is used.
25931 When a new layout is chosen, one window will always be common to the
25932 previous layout and the new one.
25934 Think of it as the Emacs @kbd{C-x 2} binding.
25938 Change the active window. The TUI associates several key bindings
25939 (like scrolling and arrow keys) with the active window. This command
25940 gives the focus to the next TUI window.
25942 Think of it as the Emacs @kbd{C-x o} binding.
25946 Switch in and out of the TUI SingleKey mode that binds single
25947 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25950 The following key bindings only work in the TUI mode:
25955 Scroll the active window one page up.
25959 Scroll the active window one page down.
25963 Scroll the active window one line up.
25967 Scroll the active window one line down.
25971 Scroll the active window one column left.
25975 Scroll the active window one column right.
25979 Refresh the screen.
25982 Because the arrow keys scroll the active window in the TUI mode, they
25983 are not available for their normal use by readline unless the command
25984 window has the focus. When another window is active, you must use
25985 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25986 and @kbd{C-f} to control the command window.
25988 @node TUI Single Key Mode
25989 @section TUI Single Key Mode
25990 @cindex TUI single key mode
25992 The TUI also provides a @dfn{SingleKey} mode, which binds several
25993 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25994 switch into this mode, where the following key bindings are used:
25997 @kindex c @r{(SingleKey TUI key)}
26001 @kindex d @r{(SingleKey TUI key)}
26005 @kindex f @r{(SingleKey TUI key)}
26009 @kindex n @r{(SingleKey TUI key)}
26013 @kindex o @r{(SingleKey TUI key)}
26015 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26017 @kindex q @r{(SingleKey TUI key)}
26019 exit the SingleKey mode.
26021 @kindex r @r{(SingleKey TUI key)}
26025 @kindex s @r{(SingleKey TUI key)}
26029 @kindex i @r{(SingleKey TUI key)}
26031 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26033 @kindex u @r{(SingleKey TUI key)}
26037 @kindex v @r{(SingleKey TUI key)}
26041 @kindex w @r{(SingleKey TUI key)}
26046 Other keys temporarily switch to the @value{GDBN} command prompt.
26047 The key that was pressed is inserted in the editing buffer so that
26048 it is possible to type most @value{GDBN} commands without interaction
26049 with the TUI SingleKey mode. Once the command is entered the TUI
26050 SingleKey mode is restored. The only way to permanently leave
26051 this mode is by typing @kbd{q} or @kbd{C-x s}.
26055 @section TUI-specific Commands
26056 @cindex TUI commands
26058 The TUI has specific commands to control the text windows.
26059 These commands are always available, even when @value{GDBN} is not in
26060 the TUI mode. When @value{GDBN} is in the standard mode, most
26061 of these commands will automatically switch to the TUI mode.
26063 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26064 terminal, or @value{GDBN} has been started with the machine interface
26065 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26066 these commands will fail with an error, because it would not be
26067 possible or desirable to enable curses window management.
26072 Activate TUI mode. The last active TUI window layout will be used if
26073 TUI mode has prevsiouly been used in the current debugging session,
26074 otherwise a default layout is used.
26077 @kindex tui disable
26078 Disable TUI mode, returning to the console interpreter.
26082 List and give the size of all displayed windows.
26084 @item layout @var{name}
26086 Changes which TUI windows are displayed. In each layout the command
26087 window is always displayed, the @var{name} parameter controls which
26088 additional windows are displayed, and can be any of the following:
26092 Display the next layout.
26095 Display the previous layout.
26098 Display the source and command windows.
26101 Display the assembly and command windows.
26104 Display the source, assembly, and command windows.
26107 When in @code{src} layout display the register, source, and command
26108 windows. When in @code{asm} or @code{split} layout display the
26109 register, assembler, and command windows.
26112 @item focus @var{name}
26114 Changes which TUI window is currently active for scrolling. The
26115 @var{name} parameter can be any of the following:
26119 Make the next window active for scrolling.
26122 Make the previous window active for scrolling.
26125 Make the source window active for scrolling.
26128 Make the assembly window active for scrolling.
26131 Make the register window active for scrolling.
26134 Make the command window active for scrolling.
26139 Refresh the screen. This is similar to typing @kbd{C-L}.
26141 @item tui reg @var{group}
26143 Changes the register group displayed in the tui register window to
26144 @var{group}. If the register window is not currently displayed this
26145 command will cause the register window to be displayed. The list of
26146 register groups, as well as their order is target specific. The
26147 following groups are available on most targets:
26150 Repeatedly selecting this group will cause the display to cycle
26151 through all of the available register groups.
26154 Repeatedly selecting this group will cause the display to cycle
26155 through all of the available register groups in the reverse order to
26159 Display the general registers.
26161 Display the floating point registers.
26163 Display the system registers.
26165 Display the vector registers.
26167 Display all registers.
26172 Update the source window and the current execution point.
26174 @item winheight @var{name} +@var{count}
26175 @itemx winheight @var{name} -@var{count}
26177 Change the height of the window @var{name} by @var{count}
26178 lines. Positive counts increase the height, while negative counts
26179 decrease it. The @var{name} parameter can be one of @code{src} (the
26180 source window), @code{cmd} (the command window), @code{asm} (the
26181 disassembly window), or @code{regs} (the register display window).
26183 @item tabset @var{nchars}
26185 Set the width of tab stops to be @var{nchars} characters. This
26186 setting affects the display of TAB characters in the source and
26190 @node TUI Configuration
26191 @section TUI Configuration Variables
26192 @cindex TUI configuration variables
26194 Several configuration variables control the appearance of TUI windows.
26197 @item set tui border-kind @var{kind}
26198 @kindex set tui border-kind
26199 Select the border appearance for the source, assembly and register windows.
26200 The possible values are the following:
26203 Use a space character to draw the border.
26206 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26209 Use the Alternate Character Set to draw the border. The border is
26210 drawn using character line graphics if the terminal supports them.
26213 @item set tui border-mode @var{mode}
26214 @kindex set tui border-mode
26215 @itemx set tui active-border-mode @var{mode}
26216 @kindex set tui active-border-mode
26217 Select the display attributes for the borders of the inactive windows
26218 or the active window. The @var{mode} can be one of the following:
26221 Use normal attributes to display the border.
26227 Use reverse video mode.
26230 Use half bright mode.
26232 @item half-standout
26233 Use half bright and standout mode.
26236 Use extra bright or bold mode.
26238 @item bold-standout
26239 Use extra bright or bold and standout mode.
26244 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26247 @cindex @sc{gnu} Emacs
26248 A special interface allows you to use @sc{gnu} Emacs to view (and
26249 edit) the source files for the program you are debugging with
26252 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26253 executable file you want to debug as an argument. This command starts
26254 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26255 created Emacs buffer.
26256 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26258 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26263 All ``terminal'' input and output goes through an Emacs buffer, called
26266 This applies both to @value{GDBN} commands and their output, and to the input
26267 and output done by the program you are debugging.
26269 This is useful because it means that you can copy the text of previous
26270 commands and input them again; you can even use parts of the output
26273 All the facilities of Emacs' Shell mode are available for interacting
26274 with your program. In particular, you can send signals the usual
26275 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26279 @value{GDBN} displays source code through Emacs.
26281 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26282 source file for that frame and puts an arrow (@samp{=>}) at the
26283 left margin of the current line. Emacs uses a separate buffer for
26284 source display, and splits the screen to show both your @value{GDBN} session
26287 Explicit @value{GDBN} @code{list} or search commands still produce output as
26288 usual, but you probably have no reason to use them from Emacs.
26291 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26292 a graphical mode, enabled by default, which provides further buffers
26293 that can control the execution and describe the state of your program.
26294 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26296 If you specify an absolute file name when prompted for the @kbd{M-x
26297 gdb} argument, then Emacs sets your current working directory to where
26298 your program resides. If you only specify the file name, then Emacs
26299 sets your current working directory to the directory associated
26300 with the previous buffer. In this case, @value{GDBN} may find your
26301 program by searching your environment's @code{PATH} variable, but on
26302 some operating systems it might not find the source. So, although the
26303 @value{GDBN} input and output session proceeds normally, the auxiliary
26304 buffer does not display the current source and line of execution.
26306 The initial working directory of @value{GDBN} is printed on the top
26307 line of the GUD buffer and this serves as a default for the commands
26308 that specify files for @value{GDBN} to operate on. @xref{Files,
26309 ,Commands to Specify Files}.
26311 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26312 need to call @value{GDBN} by a different name (for example, if you
26313 keep several configurations around, with different names) you can
26314 customize the Emacs variable @code{gud-gdb-command-name} to run the
26317 In the GUD buffer, you can use these special Emacs commands in
26318 addition to the standard Shell mode commands:
26322 Describe the features of Emacs' GUD Mode.
26325 Execute to another source line, like the @value{GDBN} @code{step} command; also
26326 update the display window to show the current file and location.
26329 Execute to next source line in this function, skipping all function
26330 calls, like the @value{GDBN} @code{next} command. Then update the display window
26331 to show the current file and location.
26334 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26335 display window accordingly.
26338 Execute until exit from the selected stack frame, like the @value{GDBN}
26339 @code{finish} command.
26342 Continue execution of your program, like the @value{GDBN} @code{continue}
26346 Go up the number of frames indicated by the numeric argument
26347 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26348 like the @value{GDBN} @code{up} command.
26351 Go down the number of frames indicated by the numeric argument, like the
26352 @value{GDBN} @code{down} command.
26355 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26356 tells @value{GDBN} to set a breakpoint on the source line point is on.
26358 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26359 separate frame which shows a backtrace when the GUD buffer is current.
26360 Move point to any frame in the stack and type @key{RET} to make it
26361 become the current frame and display the associated source in the
26362 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26363 selected frame become the current one. In graphical mode, the
26364 speedbar displays watch expressions.
26366 If you accidentally delete the source-display buffer, an easy way to get
26367 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26368 request a frame display; when you run under Emacs, this recreates
26369 the source buffer if necessary to show you the context of the current
26372 The source files displayed in Emacs are in ordinary Emacs buffers
26373 which are visiting the source files in the usual way. You can edit
26374 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26375 communicates with Emacs in terms of line numbers. If you add or
26376 delete lines from the text, the line numbers that @value{GDBN} knows cease
26377 to correspond properly with the code.
26379 A more detailed description of Emacs' interaction with @value{GDBN} is
26380 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26384 @chapter The @sc{gdb/mi} Interface
26386 @unnumberedsec Function and Purpose
26388 @cindex @sc{gdb/mi}, its purpose
26389 @sc{gdb/mi} is a line based machine oriented text interface to
26390 @value{GDBN} and is activated by specifying using the
26391 @option{--interpreter} command line option (@pxref{Mode Options}). It
26392 is specifically intended to support the development of systems which
26393 use the debugger as just one small component of a larger system.
26395 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26396 in the form of a reference manual.
26398 Note that @sc{gdb/mi} is still under construction, so some of the
26399 features described below are incomplete and subject to change
26400 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26402 @unnumberedsec Notation and Terminology
26404 @cindex notational conventions, for @sc{gdb/mi}
26405 This chapter uses the following notation:
26409 @code{|} separates two alternatives.
26412 @code{[ @var{something} ]} indicates that @var{something} is optional:
26413 it may or may not be given.
26416 @code{( @var{group} )*} means that @var{group} inside the parentheses
26417 may repeat zero or more times.
26420 @code{( @var{group} )+} means that @var{group} inside the parentheses
26421 may repeat one or more times.
26424 @code{"@var{string}"} means a literal @var{string}.
26428 @heading Dependencies
26432 * GDB/MI General Design::
26433 * GDB/MI Command Syntax::
26434 * GDB/MI Compatibility with CLI::
26435 * GDB/MI Development and Front Ends::
26436 * GDB/MI Output Records::
26437 * GDB/MI Simple Examples::
26438 * GDB/MI Command Description Format::
26439 * GDB/MI Breakpoint Commands::
26440 * GDB/MI Catchpoint Commands::
26441 * GDB/MI Program Context::
26442 * GDB/MI Thread Commands::
26443 * GDB/MI Ada Tasking Commands::
26444 * GDB/MI Program Execution::
26445 * GDB/MI Stack Manipulation::
26446 * GDB/MI Variable Objects::
26447 * GDB/MI Data Manipulation::
26448 * GDB/MI Tracepoint Commands::
26449 * GDB/MI Symbol Query::
26450 * GDB/MI File Commands::
26452 * GDB/MI Kod Commands::
26453 * GDB/MI Memory Overlay Commands::
26454 * GDB/MI Signal Handling Commands::
26456 * GDB/MI Target Manipulation::
26457 * GDB/MI File Transfer Commands::
26458 * GDB/MI Ada Exceptions Commands::
26459 * GDB/MI Support Commands::
26460 * GDB/MI Miscellaneous Commands::
26463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26464 @node GDB/MI General Design
26465 @section @sc{gdb/mi} General Design
26466 @cindex GDB/MI General Design
26468 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26469 parts---commands sent to @value{GDBN}, responses to those commands
26470 and notifications. Each command results in exactly one response,
26471 indicating either successful completion of the command, or an error.
26472 For the commands that do not resume the target, the response contains the
26473 requested information. For the commands that resume the target, the
26474 response only indicates whether the target was successfully resumed.
26475 Notifications is the mechanism for reporting changes in the state of the
26476 target, or in @value{GDBN} state, that cannot conveniently be associated with
26477 a command and reported as part of that command response.
26479 The important examples of notifications are:
26483 Exec notifications. These are used to report changes in
26484 target state---when a target is resumed, or stopped. It would not
26485 be feasible to include this information in response of resuming
26486 commands, because one resume commands can result in multiple events in
26487 different threads. Also, quite some time may pass before any event
26488 happens in the target, while a frontend needs to know whether the resuming
26489 command itself was successfully executed.
26492 Console output, and status notifications. Console output
26493 notifications are used to report output of CLI commands, as well as
26494 diagnostics for other commands. Status notifications are used to
26495 report the progress of a long-running operation. Naturally, including
26496 this information in command response would mean no output is produced
26497 until the command is finished, which is undesirable.
26500 General notifications. Commands may have various side effects on
26501 the @value{GDBN} or target state beyond their official purpose. For example,
26502 a command may change the selected thread. Although such changes can
26503 be included in command response, using notification allows for more
26504 orthogonal frontend design.
26508 There's no guarantee that whenever an MI command reports an error,
26509 @value{GDBN} or the target are in any specific state, and especially,
26510 the state is not reverted to the state before the MI command was
26511 processed. Therefore, whenever an MI command results in an error,
26512 we recommend that the frontend refreshes all the information shown in
26513 the user interface.
26517 * Context management::
26518 * Asynchronous and non-stop modes::
26522 @node Context management
26523 @subsection Context management
26525 @subsubsection Threads and Frames
26527 In most cases when @value{GDBN} accesses the target, this access is
26528 done in context of a specific thread and frame (@pxref{Frames}).
26529 Often, even when accessing global data, the target requires that a thread
26530 be specified. The CLI interface maintains the selected thread and frame,
26531 and supplies them to target on each command. This is convenient,
26532 because a command line user would not want to specify that information
26533 explicitly on each command, and because user interacts with
26534 @value{GDBN} via a single terminal, so no confusion is possible as
26535 to what thread and frame are the current ones.
26537 In the case of MI, the concept of selected thread and frame is less
26538 useful. First, a frontend can easily remember this information
26539 itself. Second, a graphical frontend can have more than one window,
26540 each one used for debugging a different thread, and the frontend might
26541 want to access additional threads for internal purposes. This
26542 increases the risk that by relying on implicitly selected thread, the
26543 frontend may be operating on a wrong one. Therefore, each MI command
26544 should explicitly specify which thread and frame to operate on. To
26545 make it possible, each MI command accepts the @samp{--thread} and
26546 @samp{--frame} options, the value to each is @value{GDBN} global
26547 identifier for thread and frame to operate on.
26549 Usually, each top-level window in a frontend allows the user to select
26550 a thread and a frame, and remembers the user selection for further
26551 operations. However, in some cases @value{GDBN} may suggest that the
26552 current thread or frame be changed. For example, when stopping on a
26553 breakpoint it is reasonable to switch to the thread where breakpoint is
26554 hit. For another example, if the user issues the CLI @samp{thread} or
26555 @samp{frame} commands via the frontend, it is desirable to change the
26556 frontend's selection to the one specified by user. @value{GDBN}
26557 communicates the suggestion to change current thread and frame using the
26558 @samp{=thread-selected} notification.
26560 Note that historically, MI shares the selected thread with CLI, so
26561 frontends used the @code{-thread-select} to execute commands in the
26562 right context. However, getting this to work right is cumbersome. The
26563 simplest way is for frontend to emit @code{-thread-select} command
26564 before every command. This doubles the number of commands that need
26565 to be sent. The alternative approach is to suppress @code{-thread-select}
26566 if the selected thread in @value{GDBN} is supposed to be identical to the
26567 thread the frontend wants to operate on. However, getting this
26568 optimization right can be tricky. In particular, if the frontend
26569 sends several commands to @value{GDBN}, and one of the commands changes the
26570 selected thread, then the behaviour of subsequent commands will
26571 change. So, a frontend should either wait for response from such
26572 problematic commands, or explicitly add @code{-thread-select} for
26573 all subsequent commands. No frontend is known to do this exactly
26574 right, so it is suggested to just always pass the @samp{--thread} and
26575 @samp{--frame} options.
26577 @subsubsection Language
26579 The execution of several commands depends on which language is selected.
26580 By default, the current language (@pxref{show language}) is used.
26581 But for commands known to be language-sensitive, it is recommended
26582 to use the @samp{--language} option. This option takes one argument,
26583 which is the name of the language to use while executing the command.
26587 -data-evaluate-expression --language c "sizeof (void*)"
26592 The valid language names are the same names accepted by the
26593 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26594 @samp{local} or @samp{unknown}.
26596 @node Asynchronous and non-stop modes
26597 @subsection Asynchronous command execution and non-stop mode
26599 On some targets, @value{GDBN} is capable of processing MI commands
26600 even while the target is running. This is called @dfn{asynchronous
26601 command execution} (@pxref{Background Execution}). The frontend may
26602 specify a preferrence for asynchronous execution using the
26603 @code{-gdb-set mi-async 1} command, which should be emitted before
26604 either running the executable or attaching to the target. After the
26605 frontend has started the executable or attached to the target, it can
26606 find if asynchronous execution is enabled using the
26607 @code{-list-target-features} command.
26610 @item -gdb-set mi-async on
26611 @item -gdb-set mi-async off
26612 Set whether MI is in asynchronous mode.
26614 When @code{off}, which is the default, MI execution commands (e.g.,
26615 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26616 for the program to stop before processing further commands.
26618 When @code{on}, MI execution commands are background execution
26619 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26620 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26621 MI commands even while the target is running.
26623 @item -gdb-show mi-async
26624 Show whether MI asynchronous mode is enabled.
26627 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26628 @code{target-async} instead of @code{mi-async}, and it had the effect
26629 of both putting MI in asynchronous mode and making CLI background
26630 commands possible. CLI background commands are now always possible
26631 ``out of the box'' if the target supports them. The old spelling is
26632 kept as a deprecated alias for backwards compatibility.
26634 Even if @value{GDBN} can accept a command while target is running,
26635 many commands that access the target do not work when the target is
26636 running. Therefore, asynchronous command execution is most useful
26637 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26638 it is possible to examine the state of one thread, while other threads
26641 When a given thread is running, MI commands that try to access the
26642 target in the context of that thread may not work, or may work only on
26643 some targets. In particular, commands that try to operate on thread's
26644 stack will not work, on any target. Commands that read memory, or
26645 modify breakpoints, may work or not work, depending on the target. Note
26646 that even commands that operate on global state, such as @code{print},
26647 @code{set}, and breakpoint commands, still access the target in the
26648 context of a specific thread, so frontend should try to find a
26649 stopped thread and perform the operation on that thread (using the
26650 @samp{--thread} option).
26652 Which commands will work in the context of a running thread is
26653 highly target dependent. However, the two commands
26654 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26655 to find the state of a thread, will always work.
26657 @node Thread groups
26658 @subsection Thread groups
26659 @value{GDBN} may be used to debug several processes at the same time.
26660 On some platfroms, @value{GDBN} may support debugging of several
26661 hardware systems, each one having several cores with several different
26662 processes running on each core. This section describes the MI
26663 mechanism to support such debugging scenarios.
26665 The key observation is that regardless of the structure of the
26666 target, MI can have a global list of threads, because most commands that
26667 accept the @samp{--thread} option do not need to know what process that
26668 thread belongs to. Therefore, it is not necessary to introduce
26669 neither additional @samp{--process} option, nor an notion of the
26670 current process in the MI interface. The only strictly new feature
26671 that is required is the ability to find how the threads are grouped
26674 To allow the user to discover such grouping, and to support arbitrary
26675 hierarchy of machines/cores/processes, MI introduces the concept of a
26676 @dfn{thread group}. Thread group is a collection of threads and other
26677 thread groups. A thread group always has a string identifier, a type,
26678 and may have additional attributes specific to the type. A new
26679 command, @code{-list-thread-groups}, returns the list of top-level
26680 thread groups, which correspond to processes that @value{GDBN} is
26681 debugging at the moment. By passing an identifier of a thread group
26682 to the @code{-list-thread-groups} command, it is possible to obtain
26683 the members of specific thread group.
26685 To allow the user to easily discover processes, and other objects, he
26686 wishes to debug, a concept of @dfn{available thread group} is
26687 introduced. Available thread group is an thread group that
26688 @value{GDBN} is not debugging, but that can be attached to, using the
26689 @code{-target-attach} command. The list of available top-level thread
26690 groups can be obtained using @samp{-list-thread-groups --available}.
26691 In general, the content of a thread group may be only retrieved only
26692 after attaching to that thread group.
26694 Thread groups are related to inferiors (@pxref{Inferiors and
26695 Programs}). Each inferior corresponds to a thread group of a special
26696 type @samp{process}, and some additional operations are permitted on
26697 such thread groups.
26699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26700 @node GDB/MI Command Syntax
26701 @section @sc{gdb/mi} Command Syntax
26704 * GDB/MI Input Syntax::
26705 * GDB/MI Output Syntax::
26708 @node GDB/MI Input Syntax
26709 @subsection @sc{gdb/mi} Input Syntax
26711 @cindex input syntax for @sc{gdb/mi}
26712 @cindex @sc{gdb/mi}, input syntax
26714 @item @var{command} @expansion{}
26715 @code{@var{cli-command} | @var{mi-command}}
26717 @item @var{cli-command} @expansion{}
26718 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26719 @var{cli-command} is any existing @value{GDBN} CLI command.
26721 @item @var{mi-command} @expansion{}
26722 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26723 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26725 @item @var{token} @expansion{}
26726 "any sequence of digits"
26728 @item @var{option} @expansion{}
26729 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26731 @item @var{parameter} @expansion{}
26732 @code{@var{non-blank-sequence} | @var{c-string}}
26734 @item @var{operation} @expansion{}
26735 @emph{any of the operations described in this chapter}
26737 @item @var{non-blank-sequence} @expansion{}
26738 @emph{anything, provided it doesn't contain special characters such as
26739 "-", @var{nl}, """ and of course " "}
26741 @item @var{c-string} @expansion{}
26742 @code{""" @var{seven-bit-iso-c-string-content} """}
26744 @item @var{nl} @expansion{}
26753 The CLI commands are still handled by the @sc{mi} interpreter; their
26754 output is described below.
26757 The @code{@var{token}}, when present, is passed back when the command
26761 Some @sc{mi} commands accept optional arguments as part of the parameter
26762 list. Each option is identified by a leading @samp{-} (dash) and may be
26763 followed by an optional argument parameter. Options occur first in the
26764 parameter list and can be delimited from normal parameters using
26765 @samp{--} (this is useful when some parameters begin with a dash).
26772 We want easy access to the existing CLI syntax (for debugging).
26775 We want it to be easy to spot a @sc{mi} operation.
26778 @node GDB/MI Output Syntax
26779 @subsection @sc{gdb/mi} Output Syntax
26781 @cindex output syntax of @sc{gdb/mi}
26782 @cindex @sc{gdb/mi}, output syntax
26783 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26784 followed, optionally, by a single result record. This result record
26785 is for the most recent command. The sequence of output records is
26786 terminated by @samp{(gdb)}.
26788 If an input command was prefixed with a @code{@var{token}} then the
26789 corresponding output for that command will also be prefixed by that same
26793 @item @var{output} @expansion{}
26794 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26796 @item @var{result-record} @expansion{}
26797 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26799 @item @var{out-of-band-record} @expansion{}
26800 @code{@var{async-record} | @var{stream-record}}
26802 @item @var{async-record} @expansion{}
26803 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26805 @item @var{exec-async-output} @expansion{}
26806 @code{[ @var{token} ] "*" @var{async-output nl}}
26808 @item @var{status-async-output} @expansion{}
26809 @code{[ @var{token} ] "+" @var{async-output nl}}
26811 @item @var{notify-async-output} @expansion{}
26812 @code{[ @var{token} ] "=" @var{async-output nl}}
26814 @item @var{async-output} @expansion{}
26815 @code{@var{async-class} ( "," @var{result} )*}
26817 @item @var{result-class} @expansion{}
26818 @code{"done" | "running" | "connected" | "error" | "exit"}
26820 @item @var{async-class} @expansion{}
26821 @code{"stopped" | @var{others}} (where @var{others} will be added
26822 depending on the needs---this is still in development).
26824 @item @var{result} @expansion{}
26825 @code{ @var{variable} "=" @var{value}}
26827 @item @var{variable} @expansion{}
26828 @code{ @var{string} }
26830 @item @var{value} @expansion{}
26831 @code{ @var{const} | @var{tuple} | @var{list} }
26833 @item @var{const} @expansion{}
26834 @code{@var{c-string}}
26836 @item @var{tuple} @expansion{}
26837 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26839 @item @var{list} @expansion{}
26840 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26841 @var{result} ( "," @var{result} )* "]" }
26843 @item @var{stream-record} @expansion{}
26844 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26846 @item @var{console-stream-output} @expansion{}
26847 @code{"~" @var{c-string nl}}
26849 @item @var{target-stream-output} @expansion{}
26850 @code{"@@" @var{c-string nl}}
26852 @item @var{log-stream-output} @expansion{}
26853 @code{"&" @var{c-string nl}}
26855 @item @var{nl} @expansion{}
26858 @item @var{token} @expansion{}
26859 @emph{any sequence of digits}.
26867 All output sequences end in a single line containing a period.
26870 The @code{@var{token}} is from the corresponding request. Note that
26871 for all async output, while the token is allowed by the grammar and
26872 may be output by future versions of @value{GDBN} for select async
26873 output messages, it is generally omitted. Frontends should treat
26874 all async output as reporting general changes in the state of the
26875 target and there should be no need to associate async output to any
26879 @cindex status output in @sc{gdb/mi}
26880 @var{status-async-output} contains on-going status information about the
26881 progress of a slow operation. It can be discarded. All status output is
26882 prefixed by @samp{+}.
26885 @cindex async output in @sc{gdb/mi}
26886 @var{exec-async-output} contains asynchronous state change on the target
26887 (stopped, started, disappeared). All async output is prefixed by
26891 @cindex notify output in @sc{gdb/mi}
26892 @var{notify-async-output} contains supplementary information that the
26893 client should handle (e.g., a new breakpoint information). All notify
26894 output is prefixed by @samp{=}.
26897 @cindex console output in @sc{gdb/mi}
26898 @var{console-stream-output} is output that should be displayed as is in the
26899 console. It is the textual response to a CLI command. All the console
26900 output is prefixed by @samp{~}.
26903 @cindex target output in @sc{gdb/mi}
26904 @var{target-stream-output} is the output produced by the target program.
26905 All the target output is prefixed by @samp{@@}.
26908 @cindex log output in @sc{gdb/mi}
26909 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26910 instance messages that should be displayed as part of an error log. All
26911 the log output is prefixed by @samp{&}.
26914 @cindex list output in @sc{gdb/mi}
26915 New @sc{gdb/mi} commands should only output @var{lists} containing
26921 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26922 details about the various output records.
26924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26925 @node GDB/MI Compatibility with CLI
26926 @section @sc{gdb/mi} Compatibility with CLI
26928 @cindex compatibility, @sc{gdb/mi} and CLI
26929 @cindex @sc{gdb/mi}, compatibility with CLI
26931 For the developers convenience CLI commands can be entered directly,
26932 but there may be some unexpected behaviour. For example, commands
26933 that query the user will behave as if the user replied yes, breakpoint
26934 command lists are not executed and some CLI commands, such as
26935 @code{if}, @code{when} and @code{define}, prompt for further input with
26936 @samp{>}, which is not valid MI output.
26938 This feature may be removed at some stage in the future and it is
26939 recommended that front ends use the @code{-interpreter-exec} command
26940 (@pxref{-interpreter-exec}).
26942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26943 @node GDB/MI Development and Front Ends
26944 @section @sc{gdb/mi} Development and Front Ends
26945 @cindex @sc{gdb/mi} development
26947 The application which takes the MI output and presents the state of the
26948 program being debugged to the user is called a @dfn{front end}.
26950 Although @sc{gdb/mi} is still incomplete, it is currently being used
26951 by a variety of front ends to @value{GDBN}. This makes it difficult
26952 to introduce new functionality without breaking existing usage. This
26953 section tries to minimize the problems by describing how the protocol
26956 Some changes in MI need not break a carefully designed front end, and
26957 for these the MI version will remain unchanged. The following is a
26958 list of changes that may occur within one level, so front ends should
26959 parse MI output in a way that can handle them:
26963 New MI commands may be added.
26966 New fields may be added to the output of any MI command.
26969 The range of values for fields with specified values, e.g.,
26970 @code{in_scope} (@pxref{-var-update}) may be extended.
26972 @c The format of field's content e.g type prefix, may change so parse it
26973 @c at your own risk. Yes, in general?
26975 @c The order of fields may change? Shouldn't really matter but it might
26976 @c resolve inconsistencies.
26979 If the changes are likely to break front ends, the MI version level
26980 will be increased by one. This will allow the front end to parse the
26981 output according to the MI version. Apart from mi0, new versions of
26982 @value{GDBN} will not support old versions of MI and it will be the
26983 responsibility of the front end to work with the new one.
26985 @c Starting with mi3, add a new command -mi-version that prints the MI
26988 The best way to avoid unexpected changes in MI that might break your front
26989 end is to make your project known to @value{GDBN} developers and
26990 follow development on @email{gdb@@sourceware.org} and
26991 @email{gdb-patches@@sourceware.org}.
26992 @cindex mailing lists
26994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26995 @node GDB/MI Output Records
26996 @section @sc{gdb/mi} Output Records
26999 * GDB/MI Result Records::
27000 * GDB/MI Stream Records::
27001 * GDB/MI Async Records::
27002 * GDB/MI Breakpoint Information::
27003 * GDB/MI Frame Information::
27004 * GDB/MI Thread Information::
27005 * GDB/MI Ada Exception Information::
27008 @node GDB/MI Result Records
27009 @subsection @sc{gdb/mi} Result Records
27011 @cindex result records in @sc{gdb/mi}
27012 @cindex @sc{gdb/mi}, result records
27013 In addition to a number of out-of-band notifications, the response to a
27014 @sc{gdb/mi} command includes one of the following result indications:
27018 @item "^done" [ "," @var{results} ]
27019 The synchronous operation was successful, @code{@var{results}} are the return
27024 This result record is equivalent to @samp{^done}. Historically, it
27025 was output instead of @samp{^done} if the command has resumed the
27026 target. This behaviour is maintained for backward compatibility, but
27027 all frontends should treat @samp{^done} and @samp{^running}
27028 identically and rely on the @samp{*running} output record to determine
27029 which threads are resumed.
27033 @value{GDBN} has connected to a remote target.
27035 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27037 The operation failed. The @code{msg=@var{c-string}} variable contains
27038 the corresponding error message.
27040 If present, the @code{code=@var{c-string}} variable provides an error
27041 code on which consumers can rely on to detect the corresponding
27042 error condition. At present, only one error code is defined:
27045 @item "undefined-command"
27046 Indicates that the command causing the error does not exist.
27051 @value{GDBN} has terminated.
27055 @node GDB/MI Stream Records
27056 @subsection @sc{gdb/mi} Stream Records
27058 @cindex @sc{gdb/mi}, stream records
27059 @cindex stream records in @sc{gdb/mi}
27060 @value{GDBN} internally maintains a number of output streams: the console, the
27061 target, and the log. The output intended for each of these streams is
27062 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27064 Each stream record begins with a unique @dfn{prefix character} which
27065 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27066 Syntax}). In addition to the prefix, each stream record contains a
27067 @code{@var{string-output}}. This is either raw text (with an implicit new
27068 line) or a quoted C string (which does not contain an implicit newline).
27071 @item "~" @var{string-output}
27072 The console output stream contains text that should be displayed in the
27073 CLI console window. It contains the textual responses to CLI commands.
27075 @item "@@" @var{string-output}
27076 The target output stream contains any textual output from the running
27077 target. This is only present when GDB's event loop is truly
27078 asynchronous, which is currently only the case for remote targets.
27080 @item "&" @var{string-output}
27081 The log stream contains debugging messages being produced by @value{GDBN}'s
27085 @node GDB/MI Async Records
27086 @subsection @sc{gdb/mi} Async Records
27088 @cindex async records in @sc{gdb/mi}
27089 @cindex @sc{gdb/mi}, async records
27090 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27091 additional changes that have occurred. Those changes can either be a
27092 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27093 target activity (e.g., target stopped).
27095 The following is the list of possible async records:
27099 @item *running,thread-id="@var{thread}"
27100 The target is now running. The @var{thread} field can be the global
27101 thread ID of the the thread that is now running, and it can be
27102 @samp{all} if all threads are running. The frontend should assume
27103 that no interaction with a running thread is possible after this
27104 notification is produced. The frontend should not assume that this
27105 notification is output only once for any command. @value{GDBN} may
27106 emit this notification several times, either for different threads,
27107 because it cannot resume all threads together, or even for a single
27108 thread, if the thread must be stepped though some code before letting
27111 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27112 The target has stopped. The @var{reason} field can have one of the
27116 @item breakpoint-hit
27117 A breakpoint was reached.
27118 @item watchpoint-trigger
27119 A watchpoint was triggered.
27120 @item read-watchpoint-trigger
27121 A read watchpoint was triggered.
27122 @item access-watchpoint-trigger
27123 An access watchpoint was triggered.
27124 @item function-finished
27125 An -exec-finish or similar CLI command was accomplished.
27126 @item location-reached
27127 An -exec-until or similar CLI command was accomplished.
27128 @item watchpoint-scope
27129 A watchpoint has gone out of scope.
27130 @item end-stepping-range
27131 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27132 similar CLI command was accomplished.
27133 @item exited-signalled
27134 The inferior exited because of a signal.
27136 The inferior exited.
27137 @item exited-normally
27138 The inferior exited normally.
27139 @item signal-received
27140 A signal was received by the inferior.
27142 The inferior has stopped due to a library being loaded or unloaded.
27143 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27144 set or when a @code{catch load} or @code{catch unload} catchpoint is
27145 in use (@pxref{Set Catchpoints}).
27147 The inferior has forked. This is reported when @code{catch fork}
27148 (@pxref{Set Catchpoints}) has been used.
27150 The inferior has vforked. This is reported in when @code{catch vfork}
27151 (@pxref{Set Catchpoints}) has been used.
27152 @item syscall-entry
27153 The inferior entered a system call. This is reported when @code{catch
27154 syscall} (@pxref{Set Catchpoints}) has been used.
27155 @item syscall-return
27156 The inferior returned from a system call. This is reported when
27157 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27159 The inferior called @code{exec}. This is reported when @code{catch exec}
27160 (@pxref{Set Catchpoints}) has been used.
27163 The @var{id} field identifies the global thread ID of the thread
27164 that directly caused the stop -- for example by hitting a breakpoint.
27165 Depending on whether all-stop
27166 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27167 stop all threads, or only the thread that directly triggered the stop.
27168 If all threads are stopped, the @var{stopped} field will have the
27169 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27170 field will be a list of thread identifiers. Presently, this list will
27171 always include a single thread, but frontend should be prepared to see
27172 several threads in the list. The @var{core} field reports the
27173 processor core on which the stop event has happened. This field may be absent
27174 if such information is not available.
27176 @item =thread-group-added,id="@var{id}"
27177 @itemx =thread-group-removed,id="@var{id}"
27178 A thread group was either added or removed. The @var{id} field
27179 contains the @value{GDBN} identifier of the thread group. When a thread
27180 group is added, it generally might not be associated with a running
27181 process. When a thread group is removed, its id becomes invalid and
27182 cannot be used in any way.
27184 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27185 A thread group became associated with a running program,
27186 either because the program was just started or the thread group
27187 was attached to a program. The @var{id} field contains the
27188 @value{GDBN} identifier of the thread group. The @var{pid} field
27189 contains process identifier, specific to the operating system.
27191 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27192 A thread group is no longer associated with a running program,
27193 either because the program has exited, or because it was detached
27194 from. The @var{id} field contains the @value{GDBN} identifier of the
27195 thread group. The @var{code} field is the exit code of the inferior; it exists
27196 only when the inferior exited with some code.
27198 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27199 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27200 A thread either was created, or has exited. The @var{id} field
27201 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27202 field identifies the thread group this thread belongs to.
27204 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27205 Informs that the selected thread or frame were changed. This notification
27206 is not emitted as result of the @code{-thread-select} or
27207 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27208 that is not documented to change the selected thread and frame actually
27209 changes them. In particular, invoking, directly or indirectly
27210 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27211 will generate this notification. Changing the thread or frame from another
27212 user interface (see @ref{Interpreters}) will also generate this notification.
27214 The @var{frame} field is only present if the newly selected thread is
27215 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27217 We suggest that in response to this notification, front ends
27218 highlight the selected thread and cause subsequent commands to apply to
27221 @item =library-loaded,...
27222 Reports that a new library file was loaded by the program. This
27223 notification has 5 fields---@var{id}, @var{target-name},
27224 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27225 opaque identifier of the library. For remote debugging case,
27226 @var{target-name} and @var{host-name} fields give the name of the
27227 library file on the target, and on the host respectively. For native
27228 debugging, both those fields have the same value. The
27229 @var{symbols-loaded} field is emitted only for backward compatibility
27230 and should not be relied on to convey any useful information. The
27231 @var{thread-group} field, if present, specifies the id of the thread
27232 group in whose context the library was loaded. If the field is
27233 absent, it means the library was loaded in the context of all present
27234 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27237 @item =library-unloaded,...
27238 Reports that a library was unloaded by the program. This notification
27239 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27240 the same meaning as for the @code{=library-loaded} notification.
27241 The @var{thread-group} field, if present, specifies the id of the
27242 thread group in whose context the library was unloaded. If the field is
27243 absent, it means the library was unloaded in the context of all present
27246 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27247 @itemx =traceframe-changed,end
27248 Reports that the trace frame was changed and its new number is
27249 @var{tfnum}. The number of the tracepoint associated with this trace
27250 frame is @var{tpnum}.
27252 @item =tsv-created,name=@var{name},initial=@var{initial}
27253 Reports that the new trace state variable @var{name} is created with
27254 initial value @var{initial}.
27256 @item =tsv-deleted,name=@var{name}
27257 @itemx =tsv-deleted
27258 Reports that the trace state variable @var{name} is deleted or all
27259 trace state variables are deleted.
27261 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27262 Reports that the trace state variable @var{name} is modified with
27263 the initial value @var{initial}. The current value @var{current} of
27264 trace state variable is optional and is reported if the current
27265 value of trace state variable is known.
27267 @item =breakpoint-created,bkpt=@{...@}
27268 @itemx =breakpoint-modified,bkpt=@{...@}
27269 @itemx =breakpoint-deleted,id=@var{number}
27270 Reports that a breakpoint was created, modified, or deleted,
27271 respectively. Only user-visible breakpoints are reported to the MI
27274 The @var{bkpt} argument is of the same form as returned by the various
27275 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27276 @var{number} is the ordinal number of the breakpoint.
27278 Note that if a breakpoint is emitted in the result record of a
27279 command, then it will not also be emitted in an async record.
27281 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27282 @itemx =record-stopped,thread-group="@var{id}"
27283 Execution log recording was either started or stopped on an
27284 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27285 group corresponding to the affected inferior.
27287 The @var{method} field indicates the method used to record execution. If the
27288 method in use supports multiple recording formats, @var{format} will be present
27289 and contain the currently used format. @xref{Process Record and Replay},
27290 for existing method and format values.
27292 @item =cmd-param-changed,param=@var{param},value=@var{value}
27293 Reports that a parameter of the command @code{set @var{param}} is
27294 changed to @var{value}. In the multi-word @code{set} command,
27295 the @var{param} is the whole parameter list to @code{set} command.
27296 For example, In command @code{set check type on}, @var{param}
27297 is @code{check type} and @var{value} is @code{on}.
27299 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27300 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27301 written in an inferior. The @var{id} is the identifier of the
27302 thread group corresponding to the affected inferior. The optional
27303 @code{type="code"} part is reported if the memory written to holds
27307 @node GDB/MI Breakpoint Information
27308 @subsection @sc{gdb/mi} Breakpoint Information
27310 When @value{GDBN} reports information about a breakpoint, a
27311 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27316 The breakpoint number. For a breakpoint that represents one location
27317 of a multi-location breakpoint, this will be a dotted pair, like
27321 The type of the breakpoint. For ordinary breakpoints this will be
27322 @samp{breakpoint}, but many values are possible.
27325 If the type of the breakpoint is @samp{catchpoint}, then this
27326 indicates the exact type of catchpoint.
27329 This is the breakpoint disposition---either @samp{del}, meaning that
27330 the breakpoint will be deleted at the next stop, or @samp{keep},
27331 meaning that the breakpoint will not be deleted.
27334 This indicates whether the breakpoint is enabled, in which case the
27335 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27336 Note that this is not the same as the field @code{enable}.
27339 The address of the breakpoint. This may be a hexidecimal number,
27340 giving the address; or the string @samp{<PENDING>}, for a pending
27341 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27342 multiple locations. This field will not be present if no address can
27343 be determined. For example, a watchpoint does not have an address.
27346 If known, the function in which the breakpoint appears.
27347 If not known, this field is not present.
27350 The name of the source file which contains this function, if known.
27351 If not known, this field is not present.
27354 The full file name of the source file which contains this function, if
27355 known. If not known, this field is not present.
27358 The line number at which this breakpoint appears, if known.
27359 If not known, this field is not present.
27362 If the source file is not known, this field may be provided. If
27363 provided, this holds the address of the breakpoint, possibly followed
27367 If this breakpoint is pending, this field is present and holds the
27368 text used to set the breakpoint, as entered by the user.
27371 Where this breakpoint's condition is evaluated, either @samp{host} or
27375 If this is a thread-specific breakpoint, then this identifies the
27376 thread in which the breakpoint can trigger.
27379 If this breakpoint is restricted to a particular Ada task, then this
27380 field will hold the task identifier.
27383 If the breakpoint is conditional, this is the condition expression.
27386 The ignore count of the breakpoint.
27389 The enable count of the breakpoint.
27391 @item traceframe-usage
27394 @item static-tracepoint-marker-string-id
27395 For a static tracepoint, the name of the static tracepoint marker.
27398 For a masked watchpoint, this is the mask.
27401 A tracepoint's pass count.
27403 @item original-location
27404 The location of the breakpoint as originally specified by the user.
27405 This field is optional.
27408 The number of times the breakpoint has been hit.
27411 This field is only given for tracepoints. This is either @samp{y},
27412 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27416 Some extra data, the exact contents of which are type-dependent.
27420 For example, here is what the output of @code{-break-insert}
27421 (@pxref{GDB/MI Breakpoint Commands}) might be:
27424 -> -break-insert main
27425 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27426 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27427 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27432 @node GDB/MI Frame Information
27433 @subsection @sc{gdb/mi} Frame Information
27435 Response from many MI commands includes an information about stack
27436 frame. This information is a tuple that may have the following
27441 The level of the stack frame. The innermost frame has the level of
27442 zero. This field is always present.
27445 The name of the function corresponding to the frame. This field may
27446 be absent if @value{GDBN} is unable to determine the function name.
27449 The code address for the frame. This field is always present.
27452 The name of the source files that correspond to the frame's code
27453 address. This field may be absent.
27456 The source line corresponding to the frames' code address. This field
27460 The name of the binary file (either executable or shared library) the
27461 corresponds to the frame's code address. This field may be absent.
27465 @node GDB/MI Thread Information
27466 @subsection @sc{gdb/mi} Thread Information
27468 Whenever @value{GDBN} has to report an information about a thread, it
27469 uses a tuple with the following fields. The fields are always present unless
27474 The global numeric id assigned to the thread by @value{GDBN}.
27477 The target-specific string identifying the thread.
27480 Additional information about the thread provided by the target.
27481 It is supposed to be human-readable and not interpreted by the
27482 frontend. This field is optional.
27485 The name of the thread. If the user specified a name using the
27486 @code{thread name} command, then this name is given. Otherwise, if
27487 @value{GDBN} can extract the thread name from the target, then that
27488 name is given. If @value{GDBN} cannot find the thread name, then this
27492 The execution state of the thread, either @samp{stopped} or @samp{running},
27493 depending on whether the thread is presently running.
27496 The stack frame currently executing in the thread. This field is only present
27497 if the thread is stopped. Its format is documented in
27498 @ref{GDB/MI Frame Information}.
27501 The value of this field is an integer number of the processor core the
27502 thread was last seen on. This field is optional.
27505 @node GDB/MI Ada Exception Information
27506 @subsection @sc{gdb/mi} Ada Exception Information
27508 Whenever a @code{*stopped} record is emitted because the program
27509 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27510 @value{GDBN} provides the name of the exception that was raised via
27511 the @code{exception-name} field. Also, for exceptions that were raised
27512 with an exception message, @value{GDBN} provides that message via
27513 the @code{exception-message} field.
27515 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27516 @node GDB/MI Simple Examples
27517 @section Simple Examples of @sc{gdb/mi} Interaction
27518 @cindex @sc{gdb/mi}, simple examples
27520 This subsection presents several simple examples of interaction using
27521 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27522 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27523 the output received from @sc{gdb/mi}.
27525 Note the line breaks shown in the examples are here only for
27526 readability, they don't appear in the real output.
27528 @subheading Setting a Breakpoint
27530 Setting a breakpoint generates synchronous output which contains detailed
27531 information of the breakpoint.
27534 -> -break-insert main
27535 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27536 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27537 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27542 @subheading Program Execution
27544 Program execution generates asynchronous records and MI gives the
27545 reason that execution stopped.
27551 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27552 frame=@{addr="0x08048564",func="main",
27553 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27554 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27559 <- *stopped,reason="exited-normally"
27563 @subheading Quitting @value{GDBN}
27565 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27573 Please note that @samp{^exit} is printed immediately, but it might
27574 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27575 performs necessary cleanups, including killing programs being debugged
27576 or disconnecting from debug hardware, so the frontend should wait till
27577 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27578 fails to exit in reasonable time.
27580 @subheading A Bad Command
27582 Here's what happens if you pass a non-existent command:
27586 <- ^error,msg="Undefined MI command: rubbish"
27591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27592 @node GDB/MI Command Description Format
27593 @section @sc{gdb/mi} Command Description Format
27595 The remaining sections describe blocks of commands. Each block of
27596 commands is laid out in a fashion similar to this section.
27598 @subheading Motivation
27600 The motivation for this collection of commands.
27602 @subheading Introduction
27604 A brief introduction to this collection of commands as a whole.
27606 @subheading Commands
27608 For each command in the block, the following is described:
27610 @subsubheading Synopsis
27613 -command @var{args}@dots{}
27616 @subsubheading Result
27618 @subsubheading @value{GDBN} Command
27620 The corresponding @value{GDBN} CLI command(s), if any.
27622 @subsubheading Example
27624 Example(s) formatted for readability. Some of the described commands have
27625 not been implemented yet and these are labeled N.A.@: (not available).
27628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27629 @node GDB/MI Breakpoint Commands
27630 @section @sc{gdb/mi} Breakpoint Commands
27632 @cindex breakpoint commands for @sc{gdb/mi}
27633 @cindex @sc{gdb/mi}, breakpoint commands
27634 This section documents @sc{gdb/mi} commands for manipulating
27637 @subheading The @code{-break-after} Command
27638 @findex -break-after
27640 @subsubheading Synopsis
27643 -break-after @var{number} @var{count}
27646 The breakpoint number @var{number} is not in effect until it has been
27647 hit @var{count} times. To see how this is reflected in the output of
27648 the @samp{-break-list} command, see the description of the
27649 @samp{-break-list} command below.
27651 @subsubheading @value{GDBN} Command
27653 The corresponding @value{GDBN} command is @samp{ignore}.
27655 @subsubheading Example
27660 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27661 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27662 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27670 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27671 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27672 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27673 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27674 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27675 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27676 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27677 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27678 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27679 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27684 @subheading The @code{-break-catch} Command
27685 @findex -break-catch
27688 @subheading The @code{-break-commands} Command
27689 @findex -break-commands
27691 @subsubheading Synopsis
27694 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27697 Specifies the CLI commands that should be executed when breakpoint
27698 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27699 are the commands. If no command is specified, any previously-set
27700 commands are cleared. @xref{Break Commands}. Typical use of this
27701 functionality is tracing a program, that is, printing of values of
27702 some variables whenever breakpoint is hit and then continuing.
27704 @subsubheading @value{GDBN} Command
27706 The corresponding @value{GDBN} command is @samp{commands}.
27708 @subsubheading Example
27713 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27714 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27715 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27718 -break-commands 1 "print v" "continue"
27723 @subheading The @code{-break-condition} Command
27724 @findex -break-condition
27726 @subsubheading Synopsis
27729 -break-condition @var{number} @var{expr}
27732 Breakpoint @var{number} will stop the program only if the condition in
27733 @var{expr} is true. The condition becomes part of the
27734 @samp{-break-list} output (see the description of the @samp{-break-list}
27737 @subsubheading @value{GDBN} Command
27739 The corresponding @value{GDBN} command is @samp{condition}.
27741 @subsubheading Example
27745 -break-condition 1 1
27749 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27750 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27751 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27752 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27753 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27754 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27755 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27756 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27757 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27758 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27762 @subheading The @code{-break-delete} Command
27763 @findex -break-delete
27765 @subsubheading Synopsis
27768 -break-delete ( @var{breakpoint} )+
27771 Delete the breakpoint(s) whose number(s) are specified in the argument
27772 list. This is obviously reflected in the breakpoint list.
27774 @subsubheading @value{GDBN} Command
27776 The corresponding @value{GDBN} command is @samp{delete}.
27778 @subsubheading Example
27786 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27797 @subheading The @code{-break-disable} Command
27798 @findex -break-disable
27800 @subsubheading Synopsis
27803 -break-disable ( @var{breakpoint} )+
27806 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27807 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27809 @subsubheading @value{GDBN} Command
27811 The corresponding @value{GDBN} command is @samp{disable}.
27813 @subsubheading Example
27821 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27822 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27823 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27824 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27825 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27826 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27827 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27828 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27829 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27830 line="5",thread-groups=["i1"],times="0"@}]@}
27834 @subheading The @code{-break-enable} Command
27835 @findex -break-enable
27837 @subsubheading Synopsis
27840 -break-enable ( @var{breakpoint} )+
27843 Enable (previously disabled) @var{breakpoint}(s).
27845 @subsubheading @value{GDBN} Command
27847 The corresponding @value{GDBN} command is @samp{enable}.
27849 @subsubheading Example
27857 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27858 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27859 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27860 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27861 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27862 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27863 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27864 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27865 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27866 line="5",thread-groups=["i1"],times="0"@}]@}
27870 @subheading The @code{-break-info} Command
27871 @findex -break-info
27873 @subsubheading Synopsis
27876 -break-info @var{breakpoint}
27880 Get information about a single breakpoint.
27882 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27883 Information}, for details on the format of each breakpoint in the
27886 @subsubheading @value{GDBN} Command
27888 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27890 @subsubheading Example
27893 @subheading The @code{-break-insert} Command
27894 @findex -break-insert
27895 @anchor{-break-insert}
27897 @subsubheading Synopsis
27900 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27901 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27902 [ -p @var{thread-id} ] [ @var{location} ]
27906 If specified, @var{location}, can be one of:
27909 @item linespec location
27910 A linespec location. @xref{Linespec Locations}.
27912 @item explicit location
27913 An explicit location. @sc{gdb/mi} explicit locations are
27914 analogous to the CLI's explicit locations using the option names
27915 listed below. @xref{Explicit Locations}.
27918 @item --source @var{filename}
27919 The source file name of the location. This option requires the use
27920 of either @samp{--function} or @samp{--line}.
27922 @item --function @var{function}
27923 The name of a function or method.
27925 @item --label @var{label}
27926 The name of a label.
27928 @item --line @var{lineoffset}
27929 An absolute or relative line offset from the start of the location.
27932 @item address location
27933 An address location, *@var{address}. @xref{Address Locations}.
27937 The possible optional parameters of this command are:
27941 Insert a temporary breakpoint.
27943 Insert a hardware breakpoint.
27945 If @var{location} cannot be parsed (for example if it
27946 refers to unknown files or functions), create a pending
27947 breakpoint. Without this flag, @value{GDBN} will report
27948 an error, and won't create a breakpoint, if @var{location}
27951 Create a disabled breakpoint.
27953 Create a tracepoint. @xref{Tracepoints}. When this parameter
27954 is used together with @samp{-h}, a fast tracepoint is created.
27955 @item -c @var{condition}
27956 Make the breakpoint conditional on @var{condition}.
27957 @item -i @var{ignore-count}
27958 Initialize the @var{ignore-count}.
27959 @item -p @var{thread-id}
27960 Restrict the breakpoint to the thread with the specified global
27964 @subsubheading Result
27966 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27967 resulting breakpoint.
27969 Note: this format is open to change.
27970 @c An out-of-band breakpoint instead of part of the result?
27972 @subsubheading @value{GDBN} Command
27974 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27975 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27977 @subsubheading Example
27982 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27983 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27986 -break-insert -t foo
27987 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27988 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27992 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27993 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27994 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27995 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27996 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27997 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27998 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27999 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28000 addr="0x0001072c", func="main",file="recursive2.c",
28001 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28003 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28004 addr="0x00010774",func="foo",file="recursive2.c",
28005 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28008 @c -break-insert -r foo.*
28009 @c ~int foo(int, int);
28010 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28011 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28016 @subheading The @code{-dprintf-insert} Command
28017 @findex -dprintf-insert
28019 @subsubheading Synopsis
28022 -dprintf-insert [ -t ] [ -f ] [ -d ]
28023 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28024 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28029 If supplied, @var{location} may be specified the same way as for
28030 the @code{-break-insert} command. @xref{-break-insert}.
28032 The possible optional parameters of this command are:
28036 Insert a temporary breakpoint.
28038 If @var{location} cannot be parsed (for example, if it
28039 refers to unknown files or functions), create a pending
28040 breakpoint. Without this flag, @value{GDBN} will report
28041 an error, and won't create a breakpoint, if @var{location}
28044 Create a disabled breakpoint.
28045 @item -c @var{condition}
28046 Make the breakpoint conditional on @var{condition}.
28047 @item -i @var{ignore-count}
28048 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28049 to @var{ignore-count}.
28050 @item -p @var{thread-id}
28051 Restrict the breakpoint to the thread with the specified global
28055 @subsubheading Result
28057 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28058 resulting breakpoint.
28060 @c An out-of-band breakpoint instead of part of the result?
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} command is @samp{dprintf}.
28066 @subsubheading Example
28070 4-dprintf-insert foo "At foo entry\n"
28071 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28072 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28073 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28074 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28075 original-location="foo"@}
28077 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28078 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28079 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28080 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28081 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28082 original-location="mi-dprintf.c:26"@}
28086 @subheading The @code{-break-list} Command
28087 @findex -break-list
28089 @subsubheading Synopsis
28095 Displays the list of inserted breakpoints, showing the following fields:
28099 number of the breakpoint
28101 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28103 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28106 is the breakpoint enabled or no: @samp{y} or @samp{n}
28108 memory location at which the breakpoint is set
28110 logical location of the breakpoint, expressed by function name, file
28112 @item Thread-groups
28113 list of thread groups to which this breakpoint applies
28115 number of times the breakpoint has been hit
28118 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28119 @code{body} field is an empty list.
28121 @subsubheading @value{GDBN} Command
28123 The corresponding @value{GDBN} command is @samp{info break}.
28125 @subsubheading Example
28130 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28137 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28138 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28140 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28141 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28142 line="13",thread-groups=["i1"],times="0"@}]@}
28146 Here's an example of the result when there are no breakpoints:
28151 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28152 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28153 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28154 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28155 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28156 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28157 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28162 @subheading The @code{-break-passcount} Command
28163 @findex -break-passcount
28165 @subsubheading Synopsis
28168 -break-passcount @var{tracepoint-number} @var{passcount}
28171 Set the passcount for tracepoint @var{tracepoint-number} to
28172 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28173 is not a tracepoint, error is emitted. This corresponds to CLI
28174 command @samp{passcount}.
28176 @subheading The @code{-break-watch} Command
28177 @findex -break-watch
28179 @subsubheading Synopsis
28182 -break-watch [ -a | -r ]
28185 Create a watchpoint. With the @samp{-a} option it will create an
28186 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28187 read from or on a write to the memory location. With the @samp{-r}
28188 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28189 trigger only when the memory location is accessed for reading. Without
28190 either of the options, the watchpoint created is a regular watchpoint,
28191 i.e., it will trigger when the memory location is accessed for writing.
28192 @xref{Set Watchpoints, , Setting Watchpoints}.
28194 Note that @samp{-break-list} will report a single list of watchpoints and
28195 breakpoints inserted.
28197 @subsubheading @value{GDBN} Command
28199 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28202 @subsubheading Example
28204 Setting a watchpoint on a variable in the @code{main} function:
28209 ^done,wpt=@{number="2",exp="x"@}
28214 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28215 value=@{old="-268439212",new="55"@},
28216 frame=@{func="main",args=[],file="recursive2.c",
28217 fullname="/home/foo/bar/recursive2.c",line="5"@}
28221 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28222 the program execution twice: first for the variable changing value, then
28223 for the watchpoint going out of scope.
28228 ^done,wpt=@{number="5",exp="C"@}
28233 *stopped,reason="watchpoint-trigger",
28234 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28235 frame=@{func="callee4",args=[],
28236 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28237 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28242 *stopped,reason="watchpoint-scope",wpnum="5",
28243 frame=@{func="callee3",args=[@{name="strarg",
28244 value="0x11940 \"A string argument.\""@}],
28245 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28246 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28250 Listing breakpoints and watchpoints, at different points in the program
28251 execution. Note that once the watchpoint goes out of scope, it is
28257 ^done,wpt=@{number="2",exp="C"@}
28260 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28261 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28262 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28263 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28264 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28265 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28266 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28267 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28268 addr="0x00010734",func="callee4",
28269 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28270 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28272 bkpt=@{number="2",type="watchpoint",disp="keep",
28273 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28278 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28279 value=@{old="-276895068",new="3"@},
28280 frame=@{func="callee4",args=[],
28281 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28282 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28285 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28286 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28287 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28288 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28289 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28290 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28291 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28292 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28293 addr="0x00010734",func="callee4",
28294 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28295 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28297 bkpt=@{number="2",type="watchpoint",disp="keep",
28298 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28302 ^done,reason="watchpoint-scope",wpnum="2",
28303 frame=@{func="callee3",args=[@{name="strarg",
28304 value="0x11940 \"A string argument.\""@}],
28305 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28306 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28309 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28310 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28311 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28312 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28313 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28314 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28315 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28316 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28317 addr="0x00010734",func="callee4",
28318 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28319 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28320 thread-groups=["i1"],times="1"@}]@}
28325 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28326 @node GDB/MI Catchpoint Commands
28327 @section @sc{gdb/mi} Catchpoint Commands
28329 This section documents @sc{gdb/mi} commands for manipulating
28333 * Shared Library GDB/MI Catchpoint Commands::
28334 * Ada Exception GDB/MI Catchpoint Commands::
28337 @node Shared Library GDB/MI Catchpoint Commands
28338 @subsection Shared Library @sc{gdb/mi} Catchpoints
28340 @subheading The @code{-catch-load} Command
28341 @findex -catch-load
28343 @subsubheading Synopsis
28346 -catch-load [ -t ] [ -d ] @var{regexp}
28349 Add a catchpoint for library load events. If the @samp{-t} option is used,
28350 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28351 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28352 in a disabled state. The @samp{regexp} argument is a regular
28353 expression used to match the name of the loaded library.
28356 @subsubheading @value{GDBN} Command
28358 The corresponding @value{GDBN} command is @samp{catch load}.
28360 @subsubheading Example
28363 -catch-load -t foo.so
28364 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28365 what="load of library matching foo.so",catch-type="load",times="0"@}
28370 @subheading The @code{-catch-unload} Command
28371 @findex -catch-unload
28373 @subsubheading Synopsis
28376 -catch-unload [ -t ] [ -d ] @var{regexp}
28379 Add a catchpoint for library unload events. If the @samp{-t} option is
28380 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28381 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28382 created in a disabled state. The @samp{regexp} argument is a regular
28383 expression used to match the name of the unloaded library.
28385 @subsubheading @value{GDBN} Command
28387 The corresponding @value{GDBN} command is @samp{catch unload}.
28389 @subsubheading Example
28392 -catch-unload -d bar.so
28393 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28394 what="load of library matching bar.so",catch-type="unload",times="0"@}
28398 @node Ada Exception GDB/MI Catchpoint Commands
28399 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28401 The following @sc{gdb/mi} commands can be used to create catchpoints
28402 that stop the execution when Ada exceptions are being raised.
28404 @subheading The @code{-catch-assert} Command
28405 @findex -catch-assert
28407 @subsubheading Synopsis
28410 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28413 Add a catchpoint for failed Ada assertions.
28415 The possible optional parameters for this command are:
28418 @item -c @var{condition}
28419 Make the catchpoint conditional on @var{condition}.
28421 Create a disabled catchpoint.
28423 Create a temporary catchpoint.
28426 @subsubheading @value{GDBN} Command
28428 The corresponding @value{GDBN} command is @samp{catch assert}.
28430 @subsubheading Example
28434 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28435 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28436 thread-groups=["i1"],times="0",
28437 original-location="__gnat_debug_raise_assert_failure"@}
28441 @subheading The @code{-catch-exception} Command
28442 @findex -catch-exception
28444 @subsubheading Synopsis
28447 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28451 Add a catchpoint stopping when Ada exceptions are raised.
28452 By default, the command stops the program when any Ada exception
28453 gets raised. But it is also possible, by using some of the
28454 optional parameters described below, to create more selective
28457 The possible optional parameters for this command are:
28460 @item -c @var{condition}
28461 Make the catchpoint conditional on @var{condition}.
28463 Create a disabled catchpoint.
28464 @item -e @var{exception-name}
28465 Only stop when @var{exception-name} is raised. This option cannot
28466 be used combined with @samp{-u}.
28468 Create a temporary catchpoint.
28470 Stop only when an unhandled exception gets raised. This option
28471 cannot be used combined with @samp{-e}.
28474 @subsubheading @value{GDBN} Command
28476 The corresponding @value{GDBN} commands are @samp{catch exception}
28477 and @samp{catch exception unhandled}.
28479 @subsubheading Example
28482 -catch-exception -e Program_Error
28483 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28484 enabled="y",addr="0x0000000000404874",
28485 what="`Program_Error' Ada exception", thread-groups=["i1"],
28486 times="0",original-location="__gnat_debug_raise_exception"@}
28490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28491 @node GDB/MI Program Context
28492 @section @sc{gdb/mi} Program Context
28494 @subheading The @code{-exec-arguments} Command
28495 @findex -exec-arguments
28498 @subsubheading Synopsis
28501 -exec-arguments @var{args}
28504 Set the inferior program arguments, to be used in the next
28507 @subsubheading @value{GDBN} Command
28509 The corresponding @value{GDBN} command is @samp{set args}.
28511 @subsubheading Example
28515 -exec-arguments -v word
28522 @subheading The @code{-exec-show-arguments} Command
28523 @findex -exec-show-arguments
28525 @subsubheading Synopsis
28528 -exec-show-arguments
28531 Print the arguments of the program.
28533 @subsubheading @value{GDBN} Command
28535 The corresponding @value{GDBN} command is @samp{show args}.
28537 @subsubheading Example
28542 @subheading The @code{-environment-cd} Command
28543 @findex -environment-cd
28545 @subsubheading Synopsis
28548 -environment-cd @var{pathdir}
28551 Set @value{GDBN}'s working directory.
28553 @subsubheading @value{GDBN} Command
28555 The corresponding @value{GDBN} command is @samp{cd}.
28557 @subsubheading Example
28561 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28567 @subheading The @code{-environment-directory} Command
28568 @findex -environment-directory
28570 @subsubheading Synopsis
28573 -environment-directory [ -r ] [ @var{pathdir} ]+
28576 Add directories @var{pathdir} to beginning of search path for source files.
28577 If the @samp{-r} option is used, the search path is reset to the default
28578 search path. If directories @var{pathdir} are supplied in addition to the
28579 @samp{-r} option, the search path is first reset and then addition
28581 Multiple directories may be specified, separated by blanks. Specifying
28582 multiple directories in a single command
28583 results in the directories added to the beginning of the
28584 search path in the same order they were presented in the command.
28585 If blanks are needed as
28586 part of a directory name, double-quotes should be used around
28587 the name. In the command output, the path will show up separated
28588 by the system directory-separator character. The directory-separator
28589 character must not be used
28590 in any directory name.
28591 If no directories are specified, the current search path is displayed.
28593 @subsubheading @value{GDBN} Command
28595 The corresponding @value{GDBN} command is @samp{dir}.
28597 @subsubheading Example
28601 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28602 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28604 -environment-directory ""
28605 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28607 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28608 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28610 -environment-directory -r
28611 ^done,source-path="$cdir:$cwd"
28616 @subheading The @code{-environment-path} Command
28617 @findex -environment-path
28619 @subsubheading Synopsis
28622 -environment-path [ -r ] [ @var{pathdir} ]+
28625 Add directories @var{pathdir} to beginning of search path for object files.
28626 If the @samp{-r} option is used, the search path is reset to the original
28627 search path that existed at gdb start-up. If directories @var{pathdir} are
28628 supplied in addition to the
28629 @samp{-r} option, the search path is first reset and then addition
28631 Multiple directories may be specified, separated by blanks. Specifying
28632 multiple directories in a single command
28633 results in the directories added to the beginning of the
28634 search path in the same order they were presented in the command.
28635 If blanks are needed as
28636 part of a directory name, double-quotes should be used around
28637 the name. In the command output, the path will show up separated
28638 by the system directory-separator character. The directory-separator
28639 character must not be used
28640 in any directory name.
28641 If no directories are specified, the current path is displayed.
28644 @subsubheading @value{GDBN} Command
28646 The corresponding @value{GDBN} command is @samp{path}.
28648 @subsubheading Example
28653 ^done,path="/usr/bin"
28655 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28656 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28658 -environment-path -r /usr/local/bin
28659 ^done,path="/usr/local/bin:/usr/bin"
28664 @subheading The @code{-environment-pwd} Command
28665 @findex -environment-pwd
28667 @subsubheading Synopsis
28673 Show the current working directory.
28675 @subsubheading @value{GDBN} Command
28677 The corresponding @value{GDBN} command is @samp{pwd}.
28679 @subsubheading Example
28684 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28689 @node GDB/MI Thread Commands
28690 @section @sc{gdb/mi} Thread Commands
28693 @subheading The @code{-thread-info} Command
28694 @findex -thread-info
28696 @subsubheading Synopsis
28699 -thread-info [ @var{thread-id} ]
28702 Reports information about either a specific thread, if the
28703 @var{thread-id} parameter is present, or about all threads.
28704 @var{thread-id} is the thread's global thread ID. When printing
28705 information about all threads, also reports the global ID of the
28708 @subsubheading @value{GDBN} Command
28710 The @samp{info thread} command prints the same information
28713 @subsubheading Result
28715 The result contains the following attributes:
28719 A list of threads. The format of the elements of the list is described in
28720 @ref{GDB/MI Thread Information}.
28722 @item current-thread-id
28723 The global id of the currently selected thread. This field is omitted if there
28724 is no selected thread (for example, when the selected inferior is not running,
28725 and therefore has no threads) or if a @var{thread-id} argument was passed to
28730 @subsubheading Example
28735 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28736 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28737 args=[]@},state="running"@},
28738 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28739 frame=@{level="0",addr="0x0804891f",func="foo",
28740 args=[@{name="i",value="10"@}],
28741 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28742 state="running"@}],
28743 current-thread-id="1"
28747 @subheading The @code{-thread-list-ids} Command
28748 @findex -thread-list-ids
28750 @subsubheading Synopsis
28756 Produces a list of the currently known global @value{GDBN} thread ids.
28757 At the end of the list it also prints the total number of such
28760 This command is retained for historical reasons, the
28761 @code{-thread-info} command should be used instead.
28763 @subsubheading @value{GDBN} Command
28765 Part of @samp{info threads} supplies the same information.
28767 @subsubheading Example
28772 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28773 current-thread-id="1",number-of-threads="3"
28778 @subheading The @code{-thread-select} Command
28779 @findex -thread-select
28781 @subsubheading Synopsis
28784 -thread-select @var{thread-id}
28787 Make thread with global thread number @var{thread-id} the current
28788 thread. It prints the number of the new current thread, and the
28789 topmost frame for that thread.
28791 This command is deprecated in favor of explicitly using the
28792 @samp{--thread} option to each command.
28794 @subsubheading @value{GDBN} Command
28796 The corresponding @value{GDBN} command is @samp{thread}.
28798 @subsubheading Example
28805 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28806 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28810 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28811 number-of-threads="3"
28814 ^done,new-thread-id="3",
28815 frame=@{level="0",func="vprintf",
28816 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28817 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28822 @node GDB/MI Ada Tasking Commands
28823 @section @sc{gdb/mi} Ada Tasking Commands
28825 @subheading The @code{-ada-task-info} Command
28826 @findex -ada-task-info
28828 @subsubheading Synopsis
28831 -ada-task-info [ @var{task-id} ]
28834 Reports information about either a specific Ada task, if the
28835 @var{task-id} parameter is present, or about all Ada tasks.
28837 @subsubheading @value{GDBN} Command
28839 The @samp{info tasks} command prints the same information
28840 about all Ada tasks (@pxref{Ada Tasks}).
28842 @subsubheading Result
28844 The result is a table of Ada tasks. The following columns are
28845 defined for each Ada task:
28849 This field exists only for the current thread. It has the value @samp{*}.
28852 The identifier that @value{GDBN} uses to refer to the Ada task.
28855 The identifier that the target uses to refer to the Ada task.
28858 The global thread identifier of the thread corresponding to the Ada
28861 This field should always exist, as Ada tasks are always implemented
28862 on top of a thread. But if @value{GDBN} cannot find this corresponding
28863 thread for any reason, the field is omitted.
28866 This field exists only when the task was created by another task.
28867 In this case, it provides the ID of the parent task.
28870 The base priority of the task.
28873 The current state of the task. For a detailed description of the
28874 possible states, see @ref{Ada Tasks}.
28877 The name of the task.
28881 @subsubheading Example
28885 ^done,tasks=@{nr_rows="3",nr_cols="8",
28886 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28887 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28888 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28889 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28890 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28891 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28892 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28893 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28894 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28895 state="Child Termination Wait",name="main_task"@}]@}
28899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28900 @node GDB/MI Program Execution
28901 @section @sc{gdb/mi} Program Execution
28903 These are the asynchronous commands which generate the out-of-band
28904 record @samp{*stopped}. Currently @value{GDBN} only really executes
28905 asynchronously with remote targets and this interaction is mimicked in
28908 @subheading The @code{-exec-continue} Command
28909 @findex -exec-continue
28911 @subsubheading Synopsis
28914 -exec-continue [--reverse] [--all|--thread-group N]
28917 Resumes the execution of the inferior program, which will continue
28918 to execute until it reaches a debugger stop event. If the
28919 @samp{--reverse} option is specified, execution resumes in reverse until
28920 it reaches a stop event. Stop events may include
28923 breakpoints or watchpoints
28925 signals or exceptions
28927 the end of the process (or its beginning under @samp{--reverse})
28929 the end or beginning of a replay log if one is being used.
28931 In all-stop mode (@pxref{All-Stop
28932 Mode}), may resume only one thread, or all threads, depending on the
28933 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28934 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28935 ignored in all-stop mode. If the @samp{--thread-group} options is
28936 specified, then all threads in that thread group are resumed.
28938 @subsubheading @value{GDBN} Command
28940 The corresponding @value{GDBN} corresponding is @samp{continue}.
28942 @subsubheading Example
28949 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28950 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28956 @subheading The @code{-exec-finish} Command
28957 @findex -exec-finish
28959 @subsubheading Synopsis
28962 -exec-finish [--reverse]
28965 Resumes the execution of the inferior program until the current
28966 function is exited. Displays the results returned by the function.
28967 If the @samp{--reverse} option is specified, resumes the reverse
28968 execution of the inferior program until the point where current
28969 function was called.
28971 @subsubheading @value{GDBN} Command
28973 The corresponding @value{GDBN} command is @samp{finish}.
28975 @subsubheading Example
28977 Function returning @code{void}.
28984 *stopped,reason="function-finished",frame=@{func="main",args=[],
28985 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28989 Function returning other than @code{void}. The name of the internal
28990 @value{GDBN} variable storing the result is printed, together with the
28997 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28998 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29000 gdb-result-var="$1",return-value="0"
29005 @subheading The @code{-exec-interrupt} Command
29006 @findex -exec-interrupt
29008 @subsubheading Synopsis
29011 -exec-interrupt [--all|--thread-group N]
29014 Interrupts the background execution of the target. Note how the token
29015 associated with the stop message is the one for the execution command
29016 that has been interrupted. The token for the interrupt itself only
29017 appears in the @samp{^done} output. If the user is trying to
29018 interrupt a non-running program, an error message will be printed.
29020 Note that when asynchronous execution is enabled, this command is
29021 asynchronous just like other execution commands. That is, first the
29022 @samp{^done} response will be printed, and the target stop will be
29023 reported after that using the @samp{*stopped} notification.
29025 In non-stop mode, only the context thread is interrupted by default.
29026 All threads (in all inferiors) will be interrupted if the
29027 @samp{--all} option is specified. If the @samp{--thread-group}
29028 option is specified, all threads in that group will be interrupted.
29030 @subsubheading @value{GDBN} Command
29032 The corresponding @value{GDBN} command is @samp{interrupt}.
29034 @subsubheading Example
29045 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29046 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29047 fullname="/home/foo/bar/try.c",line="13"@}
29052 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29056 @subheading The @code{-exec-jump} Command
29059 @subsubheading Synopsis
29062 -exec-jump @var{location}
29065 Resumes execution of the inferior program at the location specified by
29066 parameter. @xref{Specify Location}, for a description of the
29067 different forms of @var{location}.
29069 @subsubheading @value{GDBN} Command
29071 The corresponding @value{GDBN} command is @samp{jump}.
29073 @subsubheading Example
29076 -exec-jump foo.c:10
29077 *running,thread-id="all"
29082 @subheading The @code{-exec-next} Command
29085 @subsubheading Synopsis
29088 -exec-next [--reverse]
29091 Resumes execution of the inferior program, stopping when the beginning
29092 of the next source line is reached.
29094 If the @samp{--reverse} option is specified, resumes reverse execution
29095 of the inferior program, stopping at the beginning of the previous
29096 source line. If you issue this command on the first line of a
29097 function, it will take you back to the caller of that function, to the
29098 source line where the function was called.
29101 @subsubheading @value{GDBN} Command
29103 The corresponding @value{GDBN} command is @samp{next}.
29105 @subsubheading Example
29111 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29116 @subheading The @code{-exec-next-instruction} Command
29117 @findex -exec-next-instruction
29119 @subsubheading Synopsis
29122 -exec-next-instruction [--reverse]
29125 Executes one machine instruction. If the instruction is a function
29126 call, continues until the function returns. If the program stops at an
29127 instruction in the middle of a source line, the address will be
29130 If the @samp{--reverse} option is specified, resumes reverse execution
29131 of the inferior program, stopping at the previous instruction. If the
29132 previously executed instruction was a return from another function,
29133 it will continue to execute in reverse until the call to that function
29134 (from the current stack frame) is reached.
29136 @subsubheading @value{GDBN} Command
29138 The corresponding @value{GDBN} command is @samp{nexti}.
29140 @subsubheading Example
29144 -exec-next-instruction
29148 *stopped,reason="end-stepping-range",
29149 addr="0x000100d4",line="5",file="hello.c"
29154 @subheading The @code{-exec-return} Command
29155 @findex -exec-return
29157 @subsubheading Synopsis
29163 Makes current function return immediately. Doesn't execute the inferior.
29164 Displays the new current frame.
29166 @subsubheading @value{GDBN} Command
29168 The corresponding @value{GDBN} command is @samp{return}.
29170 @subsubheading Example
29174 200-break-insert callee4
29175 200^done,bkpt=@{number="1",addr="0x00010734",
29176 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29181 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29182 frame=@{func="callee4",args=[],
29183 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29184 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29190 111^done,frame=@{level="0",func="callee3",
29191 args=[@{name="strarg",
29192 value="0x11940 \"A string argument.\""@}],
29193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29194 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29199 @subheading The @code{-exec-run} Command
29202 @subsubheading Synopsis
29205 -exec-run [ --all | --thread-group N ] [ --start ]
29208 Starts execution of the inferior from the beginning. The inferior
29209 executes until either a breakpoint is encountered or the program
29210 exits. In the latter case the output will include an exit code, if
29211 the program has exited exceptionally.
29213 When neither the @samp{--all} nor the @samp{--thread-group} option
29214 is specified, the current inferior is started. If the
29215 @samp{--thread-group} option is specified, it should refer to a thread
29216 group of type @samp{process}, and that thread group will be started.
29217 If the @samp{--all} option is specified, then all inferiors will be started.
29219 Using the @samp{--start} option instructs the debugger to stop
29220 the execution at the start of the inferior's main subprogram,
29221 following the same behavior as the @code{start} command
29222 (@pxref{Starting}).
29224 @subsubheading @value{GDBN} Command
29226 The corresponding @value{GDBN} command is @samp{run}.
29228 @subsubheading Examples
29233 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29238 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29239 frame=@{func="main",args=[],file="recursive2.c",
29240 fullname="/home/foo/bar/recursive2.c",line="4"@}
29245 Program exited normally:
29253 *stopped,reason="exited-normally"
29258 Program exited exceptionally:
29266 *stopped,reason="exited",exit-code="01"
29270 Another way the program can terminate is if it receives a signal such as
29271 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29275 *stopped,reason="exited-signalled",signal-name="SIGINT",
29276 signal-meaning="Interrupt"
29280 @c @subheading -exec-signal
29283 @subheading The @code{-exec-step} Command
29286 @subsubheading Synopsis
29289 -exec-step [--reverse]
29292 Resumes execution of the inferior program, stopping when the beginning
29293 of the next source line is reached, if the next source line is not a
29294 function call. If it is, stop at the first instruction of the called
29295 function. If the @samp{--reverse} option is specified, resumes reverse
29296 execution of the inferior program, stopping at the beginning of the
29297 previously executed source line.
29299 @subsubheading @value{GDBN} Command
29301 The corresponding @value{GDBN} command is @samp{step}.
29303 @subsubheading Example
29305 Stepping into a function:
29311 *stopped,reason="end-stepping-range",
29312 frame=@{func="foo",args=[@{name="a",value="10"@},
29313 @{name="b",value="0"@}],file="recursive2.c",
29314 fullname="/home/foo/bar/recursive2.c",line="11"@}
29324 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29329 @subheading The @code{-exec-step-instruction} Command
29330 @findex -exec-step-instruction
29332 @subsubheading Synopsis
29335 -exec-step-instruction [--reverse]
29338 Resumes the inferior which executes one machine instruction. If the
29339 @samp{--reverse} option is specified, resumes reverse execution of the
29340 inferior program, stopping at the previously executed instruction.
29341 The output, once @value{GDBN} has stopped, will vary depending on
29342 whether we have stopped in the middle of a source line or not. In the
29343 former case, the address at which the program stopped will be printed
29346 @subsubheading @value{GDBN} Command
29348 The corresponding @value{GDBN} command is @samp{stepi}.
29350 @subsubheading Example
29354 -exec-step-instruction
29358 *stopped,reason="end-stepping-range",
29359 frame=@{func="foo",args=[],file="try.c",
29360 fullname="/home/foo/bar/try.c",line="10"@}
29362 -exec-step-instruction
29366 *stopped,reason="end-stepping-range",
29367 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29368 fullname="/home/foo/bar/try.c",line="10"@}
29373 @subheading The @code{-exec-until} Command
29374 @findex -exec-until
29376 @subsubheading Synopsis
29379 -exec-until [ @var{location} ]
29382 Executes the inferior until the @var{location} specified in the
29383 argument is reached. If there is no argument, the inferior executes
29384 until a source line greater than the current one is reached. The
29385 reason for stopping in this case will be @samp{location-reached}.
29387 @subsubheading @value{GDBN} Command
29389 The corresponding @value{GDBN} command is @samp{until}.
29391 @subsubheading Example
29395 -exec-until recursive2.c:6
29399 *stopped,reason="location-reached",frame=@{func="main",args=[],
29400 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29405 @subheading -file-clear
29406 Is this going away????
29409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29410 @node GDB/MI Stack Manipulation
29411 @section @sc{gdb/mi} Stack Manipulation Commands
29413 @subheading The @code{-enable-frame-filters} Command
29414 @findex -enable-frame-filters
29417 -enable-frame-filters
29420 @value{GDBN} allows Python-based frame filters to affect the output of
29421 the MI commands relating to stack traces. As there is no way to
29422 implement this in a fully backward-compatible way, a front end must
29423 request that this functionality be enabled.
29425 Once enabled, this feature cannot be disabled.
29427 Note that if Python support has not been compiled into @value{GDBN},
29428 this command will still succeed (and do nothing).
29430 @subheading The @code{-stack-info-frame} Command
29431 @findex -stack-info-frame
29433 @subsubheading Synopsis
29439 Get info on the selected frame.
29441 @subsubheading @value{GDBN} Command
29443 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29444 (without arguments).
29446 @subsubheading Example
29451 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29453 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29457 @subheading The @code{-stack-info-depth} Command
29458 @findex -stack-info-depth
29460 @subsubheading Synopsis
29463 -stack-info-depth [ @var{max-depth} ]
29466 Return the depth of the stack. If the integer argument @var{max-depth}
29467 is specified, do not count beyond @var{max-depth} frames.
29469 @subsubheading @value{GDBN} Command
29471 There's no equivalent @value{GDBN} command.
29473 @subsubheading Example
29475 For a stack with frame levels 0 through 11:
29482 -stack-info-depth 4
29485 -stack-info-depth 12
29488 -stack-info-depth 11
29491 -stack-info-depth 13
29496 @anchor{-stack-list-arguments}
29497 @subheading The @code{-stack-list-arguments} Command
29498 @findex -stack-list-arguments
29500 @subsubheading Synopsis
29503 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29504 [ @var{low-frame} @var{high-frame} ]
29507 Display a list of the arguments for the frames between @var{low-frame}
29508 and @var{high-frame} (inclusive). If @var{low-frame} and
29509 @var{high-frame} are not provided, list the arguments for the whole
29510 call stack. If the two arguments are equal, show the single frame
29511 at the corresponding level. It is an error if @var{low-frame} is
29512 larger than the actual number of frames. On the other hand,
29513 @var{high-frame} may be larger than the actual number of frames, in
29514 which case only existing frames will be returned.
29516 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29517 the variables; if it is 1 or @code{--all-values}, print also their
29518 values; and if it is 2 or @code{--simple-values}, print the name,
29519 type and value for simple data types, and the name and type for arrays,
29520 structures and unions. If the option @code{--no-frame-filters} is
29521 supplied, then Python frame filters will not be executed.
29523 If the @code{--skip-unavailable} option is specified, arguments that
29524 are not available are not listed. Partially available arguments
29525 are still displayed, however.
29527 Use of this command to obtain arguments in a single frame is
29528 deprecated in favor of the @samp{-stack-list-variables} command.
29530 @subsubheading @value{GDBN} Command
29532 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29533 @samp{gdb_get_args} command which partially overlaps with the
29534 functionality of @samp{-stack-list-arguments}.
29536 @subsubheading Example
29543 frame=@{level="0",addr="0x00010734",func="callee4",
29544 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29545 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29546 frame=@{level="1",addr="0x0001076c",func="callee3",
29547 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29548 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29549 frame=@{level="2",addr="0x0001078c",func="callee2",
29550 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29551 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29552 frame=@{level="3",addr="0x000107b4",func="callee1",
29553 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29554 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29555 frame=@{level="4",addr="0x000107e0",func="main",
29556 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29557 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29559 -stack-list-arguments 0
29562 frame=@{level="0",args=[]@},
29563 frame=@{level="1",args=[name="strarg"]@},
29564 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29565 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29566 frame=@{level="4",args=[]@}]
29568 -stack-list-arguments 1
29571 frame=@{level="0",args=[]@},
29573 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29574 frame=@{level="2",args=[
29575 @{name="intarg",value="2"@},
29576 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29577 @{frame=@{level="3",args=[
29578 @{name="intarg",value="2"@},
29579 @{name="strarg",value="0x11940 \"A string argument.\""@},
29580 @{name="fltarg",value="3.5"@}]@},
29581 frame=@{level="4",args=[]@}]
29583 -stack-list-arguments 0 2 2
29584 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29586 -stack-list-arguments 1 2 2
29587 ^done,stack-args=[frame=@{level="2",
29588 args=[@{name="intarg",value="2"@},
29589 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29593 @c @subheading -stack-list-exception-handlers
29596 @anchor{-stack-list-frames}
29597 @subheading The @code{-stack-list-frames} Command
29598 @findex -stack-list-frames
29600 @subsubheading Synopsis
29603 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29606 List the frames currently on the stack. For each frame it displays the
29611 The frame number, 0 being the topmost frame, i.e., the innermost function.
29613 The @code{$pc} value for that frame.
29617 File name of the source file where the function lives.
29618 @item @var{fullname}
29619 The full file name of the source file where the function lives.
29621 Line number corresponding to the @code{$pc}.
29623 The shared library where this function is defined. This is only given
29624 if the frame's function is not known.
29627 If invoked without arguments, this command prints a backtrace for the
29628 whole stack. If given two integer arguments, it shows the frames whose
29629 levels are between the two arguments (inclusive). If the two arguments
29630 are equal, it shows the single frame at the corresponding level. It is
29631 an error if @var{low-frame} is larger than the actual number of
29632 frames. On the other hand, @var{high-frame} may be larger than the
29633 actual number of frames, in which case only existing frames will be
29634 returned. If the option @code{--no-frame-filters} is supplied, then
29635 Python frame filters will not be executed.
29637 @subsubheading @value{GDBN} Command
29639 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29641 @subsubheading Example
29643 Full stack backtrace:
29649 [frame=@{level="0",addr="0x0001076c",func="foo",
29650 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29651 frame=@{level="1",addr="0x000107a4",func="foo",
29652 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29653 frame=@{level="2",addr="0x000107a4",func="foo",
29654 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29655 frame=@{level="3",addr="0x000107a4",func="foo",
29656 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29657 frame=@{level="4",addr="0x000107a4",func="foo",
29658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29659 frame=@{level="5",addr="0x000107a4",func="foo",
29660 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29661 frame=@{level="6",addr="0x000107a4",func="foo",
29662 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29663 frame=@{level="7",addr="0x000107a4",func="foo",
29664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29665 frame=@{level="8",addr="0x000107a4",func="foo",
29666 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29667 frame=@{level="9",addr="0x000107a4",func="foo",
29668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29669 frame=@{level="10",addr="0x000107a4",func="foo",
29670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29671 frame=@{level="11",addr="0x00010738",func="main",
29672 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29676 Show frames between @var{low_frame} and @var{high_frame}:
29680 -stack-list-frames 3 5
29682 [frame=@{level="3",addr="0x000107a4",func="foo",
29683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29684 frame=@{level="4",addr="0x000107a4",func="foo",
29685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29686 frame=@{level="5",addr="0x000107a4",func="foo",
29687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29691 Show a single frame:
29695 -stack-list-frames 3 3
29697 [frame=@{level="3",addr="0x000107a4",func="foo",
29698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29703 @subheading The @code{-stack-list-locals} Command
29704 @findex -stack-list-locals
29705 @anchor{-stack-list-locals}
29707 @subsubheading Synopsis
29710 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29713 Display the local variable names for the selected frame. If
29714 @var{print-values} is 0 or @code{--no-values}, print only the names of
29715 the variables; if it is 1 or @code{--all-values}, print also their
29716 values; and if it is 2 or @code{--simple-values}, print the name,
29717 type and value for simple data types, and the name and type for arrays,
29718 structures and unions. In this last case, a frontend can immediately
29719 display the value of simple data types and create variable objects for
29720 other data types when the user wishes to explore their values in
29721 more detail. If the option @code{--no-frame-filters} is supplied, then
29722 Python frame filters will not be executed.
29724 If the @code{--skip-unavailable} option is specified, local variables
29725 that are not available are not listed. Partially available local
29726 variables are still displayed, however.
29728 This command is deprecated in favor of the
29729 @samp{-stack-list-variables} command.
29731 @subsubheading @value{GDBN} Command
29733 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29735 @subsubheading Example
29739 -stack-list-locals 0
29740 ^done,locals=[name="A",name="B",name="C"]
29742 -stack-list-locals --all-values
29743 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29744 @{name="C",value="@{1, 2, 3@}"@}]
29745 -stack-list-locals --simple-values
29746 ^done,locals=[@{name="A",type="int",value="1"@},
29747 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29751 @anchor{-stack-list-variables}
29752 @subheading The @code{-stack-list-variables} Command
29753 @findex -stack-list-variables
29755 @subsubheading Synopsis
29758 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29761 Display the names of local variables and function arguments for the selected frame. If
29762 @var{print-values} is 0 or @code{--no-values}, print only the names of
29763 the variables; if it is 1 or @code{--all-values}, print also their
29764 values; and if it is 2 or @code{--simple-values}, print the name,
29765 type and value for simple data types, and the name and type for arrays,
29766 structures and unions. If the option @code{--no-frame-filters} is
29767 supplied, then Python frame filters will not be executed.
29769 If the @code{--skip-unavailable} option is specified, local variables
29770 and arguments that are not available are not listed. Partially
29771 available arguments and local variables are still displayed, however.
29773 @subsubheading Example
29777 -stack-list-variables --thread 1 --frame 0 --all-values
29778 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29783 @subheading The @code{-stack-select-frame} Command
29784 @findex -stack-select-frame
29786 @subsubheading Synopsis
29789 -stack-select-frame @var{framenum}
29792 Change the selected frame. Select a different frame @var{framenum} on
29795 This command in deprecated in favor of passing the @samp{--frame}
29796 option to every command.
29798 @subsubheading @value{GDBN} Command
29800 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29801 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29803 @subsubheading Example
29807 -stack-select-frame 2
29812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29813 @node GDB/MI Variable Objects
29814 @section @sc{gdb/mi} Variable Objects
29818 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29820 For the implementation of a variable debugger window (locals, watched
29821 expressions, etc.), we are proposing the adaptation of the existing code
29822 used by @code{Insight}.
29824 The two main reasons for that are:
29828 It has been proven in practice (it is already on its second generation).
29831 It will shorten development time (needless to say how important it is
29835 The original interface was designed to be used by Tcl code, so it was
29836 slightly changed so it could be used through @sc{gdb/mi}. This section
29837 describes the @sc{gdb/mi} operations that will be available and gives some
29838 hints about their use.
29840 @emph{Note}: In addition to the set of operations described here, we
29841 expect the @sc{gui} implementation of a variable window to require, at
29842 least, the following operations:
29845 @item @code{-gdb-show} @code{output-radix}
29846 @item @code{-stack-list-arguments}
29847 @item @code{-stack-list-locals}
29848 @item @code{-stack-select-frame}
29853 @subheading Introduction to Variable Objects
29855 @cindex variable objects in @sc{gdb/mi}
29857 Variable objects are "object-oriented" MI interface for examining and
29858 changing values of expressions. Unlike some other MI interfaces that
29859 work with expressions, variable objects are specifically designed for
29860 simple and efficient presentation in the frontend. A variable object
29861 is identified by string name. When a variable object is created, the
29862 frontend specifies the expression for that variable object. The
29863 expression can be a simple variable, or it can be an arbitrary complex
29864 expression, and can even involve CPU registers. After creating a
29865 variable object, the frontend can invoke other variable object
29866 operations---for example to obtain or change the value of a variable
29867 object, or to change display format.
29869 Variable objects have hierarchical tree structure. Any variable object
29870 that corresponds to a composite type, such as structure in C, has
29871 a number of child variable objects, for example corresponding to each
29872 element of a structure. A child variable object can itself have
29873 children, recursively. Recursion ends when we reach
29874 leaf variable objects, which always have built-in types. Child variable
29875 objects are created only by explicit request, so if a frontend
29876 is not interested in the children of a particular variable object, no
29877 child will be created.
29879 For a leaf variable object it is possible to obtain its value as a
29880 string, or set the value from a string. String value can be also
29881 obtained for a non-leaf variable object, but it's generally a string
29882 that only indicates the type of the object, and does not list its
29883 contents. Assignment to a non-leaf variable object is not allowed.
29885 A frontend does not need to read the values of all variable objects each time
29886 the program stops. Instead, MI provides an update command that lists all
29887 variable objects whose values has changed since the last update
29888 operation. This considerably reduces the amount of data that must
29889 be transferred to the frontend. As noted above, children variable
29890 objects are created on demand, and only leaf variable objects have a
29891 real value. As result, gdb will read target memory only for leaf
29892 variables that frontend has created.
29894 The automatic update is not always desirable. For example, a frontend
29895 might want to keep a value of some expression for future reference,
29896 and never update it. For another example, fetching memory is
29897 relatively slow for embedded targets, so a frontend might want
29898 to disable automatic update for the variables that are either not
29899 visible on the screen, or ``closed''. This is possible using so
29900 called ``frozen variable objects''. Such variable objects are never
29901 implicitly updated.
29903 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29904 fixed variable object, the expression is parsed when the variable
29905 object is created, including associating identifiers to specific
29906 variables. The meaning of expression never changes. For a floating
29907 variable object the values of variables whose names appear in the
29908 expressions are re-evaluated every time in the context of the current
29909 frame. Consider this example:
29914 struct work_state state;
29921 If a fixed variable object for the @code{state} variable is created in
29922 this function, and we enter the recursive call, the variable
29923 object will report the value of @code{state} in the top-level
29924 @code{do_work} invocation. On the other hand, a floating variable
29925 object will report the value of @code{state} in the current frame.
29927 If an expression specified when creating a fixed variable object
29928 refers to a local variable, the variable object becomes bound to the
29929 thread and frame in which the variable object is created. When such
29930 variable object is updated, @value{GDBN} makes sure that the
29931 thread/frame combination the variable object is bound to still exists,
29932 and re-evaluates the variable object in context of that thread/frame.
29934 The following is the complete set of @sc{gdb/mi} operations defined to
29935 access this functionality:
29937 @multitable @columnfractions .4 .6
29938 @item @strong{Operation}
29939 @tab @strong{Description}
29941 @item @code{-enable-pretty-printing}
29942 @tab enable Python-based pretty-printing
29943 @item @code{-var-create}
29944 @tab create a variable object
29945 @item @code{-var-delete}
29946 @tab delete the variable object and/or its children
29947 @item @code{-var-set-format}
29948 @tab set the display format of this variable
29949 @item @code{-var-show-format}
29950 @tab show the display format of this variable
29951 @item @code{-var-info-num-children}
29952 @tab tells how many children this object has
29953 @item @code{-var-list-children}
29954 @tab return a list of the object's children
29955 @item @code{-var-info-type}
29956 @tab show the type of this variable object
29957 @item @code{-var-info-expression}
29958 @tab print parent-relative expression that this variable object represents
29959 @item @code{-var-info-path-expression}
29960 @tab print full expression that this variable object represents
29961 @item @code{-var-show-attributes}
29962 @tab is this variable editable? does it exist here?
29963 @item @code{-var-evaluate-expression}
29964 @tab get the value of this variable
29965 @item @code{-var-assign}
29966 @tab set the value of this variable
29967 @item @code{-var-update}
29968 @tab update the variable and its children
29969 @item @code{-var-set-frozen}
29970 @tab set frozeness attribute
29971 @item @code{-var-set-update-range}
29972 @tab set range of children to display on update
29975 In the next subsection we describe each operation in detail and suggest
29976 how it can be used.
29978 @subheading Description And Use of Operations on Variable Objects
29980 @subheading The @code{-enable-pretty-printing} Command
29981 @findex -enable-pretty-printing
29984 -enable-pretty-printing
29987 @value{GDBN} allows Python-based visualizers to affect the output of the
29988 MI variable object commands. However, because there was no way to
29989 implement this in a fully backward-compatible way, a front end must
29990 request that this functionality be enabled.
29992 Once enabled, this feature cannot be disabled.
29994 Note that if Python support has not been compiled into @value{GDBN},
29995 this command will still succeed (and do nothing).
29997 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29998 may work differently in future versions of @value{GDBN}.
30000 @subheading The @code{-var-create} Command
30001 @findex -var-create
30003 @subsubheading Synopsis
30006 -var-create @{@var{name} | "-"@}
30007 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30010 This operation creates a variable object, which allows the monitoring of
30011 a variable, the result of an expression, a memory cell or a CPU
30014 The @var{name} parameter is the string by which the object can be
30015 referenced. It must be unique. If @samp{-} is specified, the varobj
30016 system will generate a string ``varNNNNNN'' automatically. It will be
30017 unique provided that one does not specify @var{name} of that format.
30018 The command fails if a duplicate name is found.
30020 The frame under which the expression should be evaluated can be
30021 specified by @var{frame-addr}. A @samp{*} indicates that the current
30022 frame should be used. A @samp{@@} indicates that a floating variable
30023 object must be created.
30025 @var{expression} is any expression valid on the current language set (must not
30026 begin with a @samp{*}), or one of the following:
30030 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30033 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30036 @samp{$@var{regname}} --- a CPU register name
30039 @cindex dynamic varobj
30040 A varobj's contents may be provided by a Python-based pretty-printer. In this
30041 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30042 have slightly different semantics in some cases. If the
30043 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30044 will never create a dynamic varobj. This ensures backward
30045 compatibility for existing clients.
30047 @subsubheading Result
30049 This operation returns attributes of the newly-created varobj. These
30054 The name of the varobj.
30057 The number of children of the varobj. This number is not necessarily
30058 reliable for a dynamic varobj. Instead, you must examine the
30059 @samp{has_more} attribute.
30062 The varobj's scalar value. For a varobj whose type is some sort of
30063 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30064 will not be interesting.
30067 The varobj's type. This is a string representation of the type, as
30068 would be printed by the @value{GDBN} CLI. If @samp{print object}
30069 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30070 @emph{actual} (derived) type of the object is shown rather than the
30071 @emph{declared} one.
30074 If a variable object is bound to a specific thread, then this is the
30075 thread's global identifier.
30078 For a dynamic varobj, this indicates whether there appear to be any
30079 children available. For a non-dynamic varobj, this will be 0.
30082 This attribute will be present and have the value @samp{1} if the
30083 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30084 then this attribute will not be present.
30087 A dynamic varobj can supply a display hint to the front end. The
30088 value comes directly from the Python pretty-printer object's
30089 @code{display_hint} method. @xref{Pretty Printing API}.
30092 Typical output will look like this:
30095 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30096 has_more="@var{has_more}"
30100 @subheading The @code{-var-delete} Command
30101 @findex -var-delete
30103 @subsubheading Synopsis
30106 -var-delete [ -c ] @var{name}
30109 Deletes a previously created variable object and all of its children.
30110 With the @samp{-c} option, just deletes the children.
30112 Returns an error if the object @var{name} is not found.
30115 @subheading The @code{-var-set-format} Command
30116 @findex -var-set-format
30118 @subsubheading Synopsis
30121 -var-set-format @var{name} @var{format-spec}
30124 Sets the output format for the value of the object @var{name} to be
30127 @anchor{-var-set-format}
30128 The syntax for the @var{format-spec} is as follows:
30131 @var{format-spec} @expansion{}
30132 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30135 The natural format is the default format choosen automatically
30136 based on the variable type (like decimal for an @code{int}, hex
30137 for pointers, etc.).
30139 The zero-hexadecimal format has a representation similar to hexadecimal
30140 but with padding zeroes to the left of the value. For example, a 32-bit
30141 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30142 zero-hexadecimal format.
30144 For a variable with children, the format is set only on the
30145 variable itself, and the children are not affected.
30147 @subheading The @code{-var-show-format} Command
30148 @findex -var-show-format
30150 @subsubheading Synopsis
30153 -var-show-format @var{name}
30156 Returns the format used to display the value of the object @var{name}.
30159 @var{format} @expansion{}
30164 @subheading The @code{-var-info-num-children} Command
30165 @findex -var-info-num-children
30167 @subsubheading Synopsis
30170 -var-info-num-children @var{name}
30173 Returns the number of children of a variable object @var{name}:
30179 Note that this number is not completely reliable for a dynamic varobj.
30180 It will return the current number of children, but more children may
30184 @subheading The @code{-var-list-children} Command
30185 @findex -var-list-children
30187 @subsubheading Synopsis
30190 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30192 @anchor{-var-list-children}
30194 Return a list of the children of the specified variable object and
30195 create variable objects for them, if they do not already exist. With
30196 a single argument or if @var{print-values} has a value of 0 or
30197 @code{--no-values}, print only the names of the variables; if
30198 @var{print-values} is 1 or @code{--all-values}, also print their
30199 values; and if it is 2 or @code{--simple-values} print the name and
30200 value for simple data types and just the name for arrays, structures
30203 @var{from} and @var{to}, if specified, indicate the range of children
30204 to report. If @var{from} or @var{to} is less than zero, the range is
30205 reset and all children will be reported. Otherwise, children starting
30206 at @var{from} (zero-based) and up to and excluding @var{to} will be
30209 If a child range is requested, it will only affect the current call to
30210 @code{-var-list-children}, but not future calls to @code{-var-update}.
30211 For this, you must instead use @code{-var-set-update-range}. The
30212 intent of this approach is to enable a front end to implement any
30213 update approach it likes; for example, scrolling a view may cause the
30214 front end to request more children with @code{-var-list-children}, and
30215 then the front end could call @code{-var-set-update-range} with a
30216 different range to ensure that future updates are restricted to just
30219 For each child the following results are returned:
30224 Name of the variable object created for this child.
30227 The expression to be shown to the user by the front end to designate this child.
30228 For example this may be the name of a structure member.
30230 For a dynamic varobj, this value cannot be used to form an
30231 expression. There is no way to do this at all with a dynamic varobj.
30233 For C/C@t{++} structures there are several pseudo children returned to
30234 designate access qualifiers. For these pseudo children @var{exp} is
30235 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30236 type and value are not present.
30238 A dynamic varobj will not report the access qualifying
30239 pseudo-children, regardless of the language. This information is not
30240 available at all with a dynamic varobj.
30243 Number of children this child has. For a dynamic varobj, this will be
30247 The type of the child. If @samp{print object}
30248 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30249 @emph{actual} (derived) type of the object is shown rather than the
30250 @emph{declared} one.
30253 If values were requested, this is the value.
30256 If this variable object is associated with a thread, this is the
30257 thread's global thread id. Otherwise this result is not present.
30260 If the variable object is frozen, this variable will be present with a value of 1.
30263 A dynamic varobj can supply a display hint to the front end. The
30264 value comes directly from the Python pretty-printer object's
30265 @code{display_hint} method. @xref{Pretty Printing API}.
30268 This attribute will be present and have the value @samp{1} if the
30269 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30270 then this attribute will not be present.
30274 The result may have its own attributes:
30278 A dynamic varobj can supply a display hint to the front end. The
30279 value comes directly from the Python pretty-printer object's
30280 @code{display_hint} method. @xref{Pretty Printing API}.
30283 This is an integer attribute which is nonzero if there are children
30284 remaining after the end of the selected range.
30287 @subsubheading Example
30291 -var-list-children n
30292 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30293 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30295 -var-list-children --all-values n
30296 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30297 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30301 @subheading The @code{-var-info-type} Command
30302 @findex -var-info-type
30304 @subsubheading Synopsis
30307 -var-info-type @var{name}
30310 Returns the type of the specified variable @var{name}. The type is
30311 returned as a string in the same format as it is output by the
30315 type=@var{typename}
30319 @subheading The @code{-var-info-expression} Command
30320 @findex -var-info-expression
30322 @subsubheading Synopsis
30325 -var-info-expression @var{name}
30328 Returns a string that is suitable for presenting this
30329 variable object in user interface. The string is generally
30330 not valid expression in the current language, and cannot be evaluated.
30332 For example, if @code{a} is an array, and variable object
30333 @code{A} was created for @code{a}, then we'll get this output:
30336 (gdb) -var-info-expression A.1
30337 ^done,lang="C",exp="1"
30341 Here, the value of @code{lang} is the language name, which can be
30342 found in @ref{Supported Languages}.
30344 Note that the output of the @code{-var-list-children} command also
30345 includes those expressions, so the @code{-var-info-expression} command
30348 @subheading The @code{-var-info-path-expression} Command
30349 @findex -var-info-path-expression
30351 @subsubheading Synopsis
30354 -var-info-path-expression @var{name}
30357 Returns an expression that can be evaluated in the current
30358 context and will yield the same value that a variable object has.
30359 Compare this with the @code{-var-info-expression} command, which
30360 result can be used only for UI presentation. Typical use of
30361 the @code{-var-info-path-expression} command is creating a
30362 watchpoint from a variable object.
30364 This command is currently not valid for children of a dynamic varobj,
30365 and will give an error when invoked on one.
30367 For example, suppose @code{C} is a C@t{++} class, derived from class
30368 @code{Base}, and that the @code{Base} class has a member called
30369 @code{m_size}. Assume a variable @code{c} is has the type of
30370 @code{C} and a variable object @code{C} was created for variable
30371 @code{c}. Then, we'll get this output:
30373 (gdb) -var-info-path-expression C.Base.public.m_size
30374 ^done,path_expr=((Base)c).m_size)
30377 @subheading The @code{-var-show-attributes} Command
30378 @findex -var-show-attributes
30380 @subsubheading Synopsis
30383 -var-show-attributes @var{name}
30386 List attributes of the specified variable object @var{name}:
30389 status=@var{attr} [ ( ,@var{attr} )* ]
30393 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30395 @subheading The @code{-var-evaluate-expression} Command
30396 @findex -var-evaluate-expression
30398 @subsubheading Synopsis
30401 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30404 Evaluates the expression that is represented by the specified variable
30405 object and returns its value as a string. The format of the string
30406 can be specified with the @samp{-f} option. The possible values of
30407 this option are the same as for @code{-var-set-format}
30408 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30409 the current display format will be used. The current display format
30410 can be changed using the @code{-var-set-format} command.
30416 Note that one must invoke @code{-var-list-children} for a variable
30417 before the value of a child variable can be evaluated.
30419 @subheading The @code{-var-assign} Command
30420 @findex -var-assign
30422 @subsubheading Synopsis
30425 -var-assign @var{name} @var{expression}
30428 Assigns the value of @var{expression} to the variable object specified
30429 by @var{name}. The object must be @samp{editable}. If the variable's
30430 value is altered by the assign, the variable will show up in any
30431 subsequent @code{-var-update} list.
30433 @subsubheading Example
30441 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30445 @subheading The @code{-var-update} Command
30446 @findex -var-update
30448 @subsubheading Synopsis
30451 -var-update [@var{print-values}] @{@var{name} | "*"@}
30454 Reevaluate the expressions corresponding to the variable object
30455 @var{name} and all its direct and indirect children, and return the
30456 list of variable objects whose values have changed; @var{name} must
30457 be a root variable object. Here, ``changed'' means that the result of
30458 @code{-var-evaluate-expression} before and after the
30459 @code{-var-update} is different. If @samp{*} is used as the variable
30460 object names, all existing variable objects are updated, except
30461 for frozen ones (@pxref{-var-set-frozen}). The option
30462 @var{print-values} determines whether both names and values, or just
30463 names are printed. The possible values of this option are the same
30464 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30465 recommended to use the @samp{--all-values} option, to reduce the
30466 number of MI commands needed on each program stop.
30468 With the @samp{*} parameter, if a variable object is bound to a
30469 currently running thread, it will not be updated, without any
30472 If @code{-var-set-update-range} was previously used on a varobj, then
30473 only the selected range of children will be reported.
30475 @code{-var-update} reports all the changed varobjs in a tuple named
30478 Each item in the change list is itself a tuple holding:
30482 The name of the varobj.
30485 If values were requested for this update, then this field will be
30486 present and will hold the value of the varobj.
30489 @anchor{-var-update}
30490 This field is a string which may take one of three values:
30494 The variable object's current value is valid.
30497 The variable object does not currently hold a valid value but it may
30498 hold one in the future if its associated expression comes back into
30502 The variable object no longer holds a valid value.
30503 This can occur when the executable file being debugged has changed,
30504 either through recompilation or by using the @value{GDBN} @code{file}
30505 command. The front end should normally choose to delete these variable
30509 In the future new values may be added to this list so the front should
30510 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30513 This is only present if the varobj is still valid. If the type
30514 changed, then this will be the string @samp{true}; otherwise it will
30517 When a varobj's type changes, its children are also likely to have
30518 become incorrect. Therefore, the varobj's children are automatically
30519 deleted when this attribute is @samp{true}. Also, the varobj's update
30520 range, when set using the @code{-var-set-update-range} command, is
30524 If the varobj's type changed, then this field will be present and will
30527 @item new_num_children
30528 For a dynamic varobj, if the number of children changed, or if the
30529 type changed, this will be the new number of children.
30531 The @samp{numchild} field in other varobj responses is generally not
30532 valid for a dynamic varobj -- it will show the number of children that
30533 @value{GDBN} knows about, but because dynamic varobjs lazily
30534 instantiate their children, this will not reflect the number of
30535 children which may be available.
30537 The @samp{new_num_children} attribute only reports changes to the
30538 number of children known by @value{GDBN}. This is the only way to
30539 detect whether an update has removed children (which necessarily can
30540 only happen at the end of the update range).
30543 The display hint, if any.
30546 This is an integer value, which will be 1 if there are more children
30547 available outside the varobj's update range.
30550 This attribute will be present and have the value @samp{1} if the
30551 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30552 then this attribute will not be present.
30555 If new children were added to a dynamic varobj within the selected
30556 update range (as set by @code{-var-set-update-range}), then they will
30557 be listed in this attribute.
30560 @subsubheading Example
30567 -var-update --all-values var1
30568 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30569 type_changed="false"@}]
30573 @subheading The @code{-var-set-frozen} Command
30574 @findex -var-set-frozen
30575 @anchor{-var-set-frozen}
30577 @subsubheading Synopsis
30580 -var-set-frozen @var{name} @var{flag}
30583 Set the frozenness flag on the variable object @var{name}. The
30584 @var{flag} parameter should be either @samp{1} to make the variable
30585 frozen or @samp{0} to make it unfrozen. If a variable object is
30586 frozen, then neither itself, nor any of its children, are
30587 implicitly updated by @code{-var-update} of
30588 a parent variable or by @code{-var-update *}. Only
30589 @code{-var-update} of the variable itself will update its value and
30590 values of its children. After a variable object is unfrozen, it is
30591 implicitly updated by all subsequent @code{-var-update} operations.
30592 Unfreezing a variable does not update it, only subsequent
30593 @code{-var-update} does.
30595 @subsubheading Example
30599 -var-set-frozen V 1
30604 @subheading The @code{-var-set-update-range} command
30605 @findex -var-set-update-range
30606 @anchor{-var-set-update-range}
30608 @subsubheading Synopsis
30611 -var-set-update-range @var{name} @var{from} @var{to}
30614 Set the range of children to be returned by future invocations of
30615 @code{-var-update}.
30617 @var{from} and @var{to} indicate the range of children to report. If
30618 @var{from} or @var{to} is less than zero, the range is reset and all
30619 children will be reported. Otherwise, children starting at @var{from}
30620 (zero-based) and up to and excluding @var{to} will be reported.
30622 @subsubheading Example
30626 -var-set-update-range V 1 2
30630 @subheading The @code{-var-set-visualizer} command
30631 @findex -var-set-visualizer
30632 @anchor{-var-set-visualizer}
30634 @subsubheading Synopsis
30637 -var-set-visualizer @var{name} @var{visualizer}
30640 Set a visualizer for the variable object @var{name}.
30642 @var{visualizer} is the visualizer to use. The special value
30643 @samp{None} means to disable any visualizer in use.
30645 If not @samp{None}, @var{visualizer} must be a Python expression.
30646 This expression must evaluate to a callable object which accepts a
30647 single argument. @value{GDBN} will call this object with the value of
30648 the varobj @var{name} as an argument (this is done so that the same
30649 Python pretty-printing code can be used for both the CLI and MI).
30650 When called, this object must return an object which conforms to the
30651 pretty-printing interface (@pxref{Pretty Printing API}).
30653 The pre-defined function @code{gdb.default_visualizer} may be used to
30654 select a visualizer by following the built-in process
30655 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30656 a varobj is created, and so ordinarily is not needed.
30658 This feature is only available if Python support is enabled. The MI
30659 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30660 can be used to check this.
30662 @subsubheading Example
30664 Resetting the visualizer:
30668 -var-set-visualizer V None
30672 Reselecting the default (type-based) visualizer:
30676 -var-set-visualizer V gdb.default_visualizer
30680 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30681 can be used to instantiate this class for a varobj:
30685 -var-set-visualizer V "lambda val: SomeClass()"
30689 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30690 @node GDB/MI Data Manipulation
30691 @section @sc{gdb/mi} Data Manipulation
30693 @cindex data manipulation, in @sc{gdb/mi}
30694 @cindex @sc{gdb/mi}, data manipulation
30695 This section describes the @sc{gdb/mi} commands that manipulate data:
30696 examine memory and registers, evaluate expressions, etc.
30698 For details about what an addressable memory unit is,
30699 @pxref{addressable memory unit}.
30701 @c REMOVED FROM THE INTERFACE.
30702 @c @subheading -data-assign
30703 @c Change the value of a program variable. Plenty of side effects.
30704 @c @subsubheading GDB Command
30706 @c @subsubheading Example
30709 @subheading The @code{-data-disassemble} Command
30710 @findex -data-disassemble
30712 @subsubheading Synopsis
30716 [ -s @var{start-addr} -e @var{end-addr} ]
30717 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30725 @item @var{start-addr}
30726 is the beginning address (or @code{$pc})
30727 @item @var{end-addr}
30729 @item @var{filename}
30730 is the name of the file to disassemble
30731 @item @var{linenum}
30732 is the line number to disassemble around
30734 is the number of disassembly lines to be produced. If it is -1,
30735 the whole function will be disassembled, in case no @var{end-addr} is
30736 specified. If @var{end-addr} is specified as a non-zero value, and
30737 @var{lines} is lower than the number of disassembly lines between
30738 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30739 displayed; if @var{lines} is higher than the number of lines between
30740 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30745 @item 0 disassembly only
30746 @item 1 mixed source and disassembly (deprecated)
30747 @item 2 disassembly with raw opcodes
30748 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30749 @item 4 mixed source and disassembly
30750 @item 5 mixed source and disassembly with raw opcodes
30753 Modes 1 and 3 are deprecated. The output is ``source centric''
30754 which hasn't proved useful in practice.
30755 @xref{Machine Code}, for a discussion of the difference between
30756 @code{/m} and @code{/s} output of the @code{disassemble} command.
30759 @subsubheading Result
30761 The result of the @code{-data-disassemble} command will be a list named
30762 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30763 used with the @code{-data-disassemble} command.
30765 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30770 The address at which this instruction was disassembled.
30773 The name of the function this instruction is within.
30776 The decimal offset in bytes from the start of @samp{func-name}.
30779 The text disassembly for this @samp{address}.
30782 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30783 bytes for the @samp{inst} field.
30787 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30788 @samp{src_and_asm_line}, each of which has the following fields:
30792 The line number within @samp{file}.
30795 The file name from the compilation unit. This might be an absolute
30796 file name or a relative file name depending on the compile command
30800 Absolute file name of @samp{file}. It is converted to a canonical form
30801 using the source file search path
30802 (@pxref{Source Path, ,Specifying Source Directories})
30803 and after resolving all the symbolic links.
30805 If the source file is not found this field will contain the path as
30806 present in the debug information.
30808 @item line_asm_insn
30809 This is a list of tuples containing the disassembly for @samp{line} in
30810 @samp{file}. The fields of each tuple are the same as for
30811 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30812 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30817 Note that whatever included in the @samp{inst} field, is not
30818 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30821 @subsubheading @value{GDBN} Command
30823 The corresponding @value{GDBN} command is @samp{disassemble}.
30825 @subsubheading Example
30827 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30831 -data-disassemble -s $pc -e "$pc + 20" -- 0
30834 @{address="0x000107c0",func-name="main",offset="4",
30835 inst="mov 2, %o0"@},
30836 @{address="0x000107c4",func-name="main",offset="8",
30837 inst="sethi %hi(0x11800), %o2"@},
30838 @{address="0x000107c8",func-name="main",offset="12",
30839 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30840 @{address="0x000107cc",func-name="main",offset="16",
30841 inst="sethi %hi(0x11800), %o2"@},
30842 @{address="0x000107d0",func-name="main",offset="20",
30843 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30847 Disassemble the whole @code{main} function. Line 32 is part of
30851 -data-disassemble -f basics.c -l 32 -- 0
30853 @{address="0x000107bc",func-name="main",offset="0",
30854 inst="save %sp, -112, %sp"@},
30855 @{address="0x000107c0",func-name="main",offset="4",
30856 inst="mov 2, %o0"@},
30857 @{address="0x000107c4",func-name="main",offset="8",
30858 inst="sethi %hi(0x11800), %o2"@},
30860 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30861 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30865 Disassemble 3 instructions from the start of @code{main}:
30869 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30871 @{address="0x000107bc",func-name="main",offset="0",
30872 inst="save %sp, -112, %sp"@},
30873 @{address="0x000107c0",func-name="main",offset="4",
30874 inst="mov 2, %o0"@},
30875 @{address="0x000107c4",func-name="main",offset="8",
30876 inst="sethi %hi(0x11800), %o2"@}]
30880 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30884 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30886 src_and_asm_line=@{line="31",
30887 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30888 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30889 line_asm_insn=[@{address="0x000107bc",
30890 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30891 src_and_asm_line=@{line="32",
30892 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30893 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30894 line_asm_insn=[@{address="0x000107c0",
30895 func-name="main",offset="4",inst="mov 2, %o0"@},
30896 @{address="0x000107c4",func-name="main",offset="8",
30897 inst="sethi %hi(0x11800), %o2"@}]@}]
30902 @subheading The @code{-data-evaluate-expression} Command
30903 @findex -data-evaluate-expression
30905 @subsubheading Synopsis
30908 -data-evaluate-expression @var{expr}
30911 Evaluate @var{expr} as an expression. The expression could contain an
30912 inferior function call. The function call will execute synchronously.
30913 If the expression contains spaces, it must be enclosed in double quotes.
30915 @subsubheading @value{GDBN} Command
30917 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30918 @samp{call}. In @code{gdbtk} only, there's a corresponding
30919 @samp{gdb_eval} command.
30921 @subsubheading Example
30923 In the following example, the numbers that precede the commands are the
30924 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30925 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30929 211-data-evaluate-expression A
30932 311-data-evaluate-expression &A
30933 311^done,value="0xefffeb7c"
30935 411-data-evaluate-expression A+3
30938 511-data-evaluate-expression "A + 3"
30944 @subheading The @code{-data-list-changed-registers} Command
30945 @findex -data-list-changed-registers
30947 @subsubheading Synopsis
30950 -data-list-changed-registers
30953 Display a list of the registers that have changed.
30955 @subsubheading @value{GDBN} Command
30957 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30958 has the corresponding command @samp{gdb_changed_register_list}.
30960 @subsubheading Example
30962 On a PPC MBX board:
30970 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30971 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30974 -data-list-changed-registers
30975 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30976 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30977 "24","25","26","27","28","30","31","64","65","66","67","69"]
30982 @subheading The @code{-data-list-register-names} Command
30983 @findex -data-list-register-names
30985 @subsubheading Synopsis
30988 -data-list-register-names [ ( @var{regno} )+ ]
30991 Show a list of register names for the current target. If no arguments
30992 are given, it shows a list of the names of all the registers. If
30993 integer numbers are given as arguments, it will print a list of the
30994 names of the registers corresponding to the arguments. To ensure
30995 consistency between a register name and its number, the output list may
30996 include empty register names.
30998 @subsubheading @value{GDBN} Command
31000 @value{GDBN} does not have a command which corresponds to
31001 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31002 corresponding command @samp{gdb_regnames}.
31004 @subsubheading Example
31006 For the PPC MBX board:
31009 -data-list-register-names
31010 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31011 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31012 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31013 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31014 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31015 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31016 "", "pc","ps","cr","lr","ctr","xer"]
31018 -data-list-register-names 1 2 3
31019 ^done,register-names=["r1","r2","r3"]
31023 @subheading The @code{-data-list-register-values} Command
31024 @findex -data-list-register-values
31026 @subsubheading Synopsis
31029 -data-list-register-values
31030 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31033 Display the registers' contents. The format according to which the
31034 registers' contents are to be returned is given by @var{fmt}, followed
31035 by an optional list of numbers specifying the registers to display. A
31036 missing list of numbers indicates that the contents of all the
31037 registers must be returned. The @code{--skip-unavailable} option
31038 indicates that only the available registers are to be returned.
31040 Allowed formats for @var{fmt} are:
31057 @subsubheading @value{GDBN} Command
31059 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31060 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31062 @subsubheading Example
31064 For a PPC MBX board (note: line breaks are for readability only, they
31065 don't appear in the actual output):
31069 -data-list-register-values r 64 65
31070 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31071 @{number="65",value="0x00029002"@}]
31073 -data-list-register-values x
31074 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31075 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31076 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31077 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31078 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31079 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31080 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31081 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31082 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31083 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31084 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31085 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31086 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31087 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31088 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31089 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31090 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31091 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31092 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31093 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31094 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31095 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31096 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31097 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31098 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31099 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31100 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31101 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31102 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31103 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31104 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31105 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31106 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31107 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31108 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31109 @{number="69",value="0x20002b03"@}]
31114 @subheading The @code{-data-read-memory} Command
31115 @findex -data-read-memory
31117 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31119 @subsubheading Synopsis
31122 -data-read-memory [ -o @var{byte-offset} ]
31123 @var{address} @var{word-format} @var{word-size}
31124 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31131 @item @var{address}
31132 An expression specifying the address of the first memory word to be
31133 read. Complex expressions containing embedded white space should be
31134 quoted using the C convention.
31136 @item @var{word-format}
31137 The format to be used to print the memory words. The notation is the
31138 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31141 @item @var{word-size}
31142 The size of each memory word in bytes.
31144 @item @var{nr-rows}
31145 The number of rows in the output table.
31147 @item @var{nr-cols}
31148 The number of columns in the output table.
31151 If present, indicates that each row should include an @sc{ascii} dump. The
31152 value of @var{aschar} is used as a padding character when a byte is not a
31153 member of the printable @sc{ascii} character set (printable @sc{ascii}
31154 characters are those whose code is between 32 and 126, inclusively).
31156 @item @var{byte-offset}
31157 An offset to add to the @var{address} before fetching memory.
31160 This command displays memory contents as a table of @var{nr-rows} by
31161 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31162 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31163 (returned as @samp{total-bytes}). Should less than the requested number
31164 of bytes be returned by the target, the missing words are identified
31165 using @samp{N/A}. The number of bytes read from the target is returned
31166 in @samp{nr-bytes} and the starting address used to read memory in
31169 The address of the next/previous row or page is available in
31170 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31173 @subsubheading @value{GDBN} Command
31175 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31176 @samp{gdb_get_mem} memory read command.
31178 @subsubheading Example
31180 Read six bytes of memory starting at @code{bytes+6} but then offset by
31181 @code{-6} bytes. Format as three rows of two columns. One byte per
31182 word. Display each word in hex.
31186 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31187 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31188 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31189 prev-page="0x0000138a",memory=[
31190 @{addr="0x00001390",data=["0x00","0x01"]@},
31191 @{addr="0x00001392",data=["0x02","0x03"]@},
31192 @{addr="0x00001394",data=["0x04","0x05"]@}]
31196 Read two bytes of memory starting at address @code{shorts + 64} and
31197 display as a single word formatted in decimal.
31201 5-data-read-memory shorts+64 d 2 1 1
31202 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31203 next-row="0x00001512",prev-row="0x0000150e",
31204 next-page="0x00001512",prev-page="0x0000150e",memory=[
31205 @{addr="0x00001510",data=["128"]@}]
31209 Read thirty two bytes of memory starting at @code{bytes+16} and format
31210 as eight rows of four columns. Include a string encoding with @samp{x}
31211 used as the non-printable character.
31215 4-data-read-memory bytes+16 x 1 8 4 x
31216 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31217 next-row="0x000013c0",prev-row="0x0000139c",
31218 next-page="0x000013c0",prev-page="0x00001380",memory=[
31219 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31220 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31221 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31222 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31223 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31224 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31225 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31226 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31230 @subheading The @code{-data-read-memory-bytes} Command
31231 @findex -data-read-memory-bytes
31233 @subsubheading Synopsis
31236 -data-read-memory-bytes [ -o @var{offset} ]
31237 @var{address} @var{count}
31244 @item @var{address}
31245 An expression specifying the address of the first addressable memory unit
31246 to be read. Complex expressions containing embedded white space should be
31247 quoted using the C convention.
31250 The number of addressable memory units to read. This should be an integer
31254 The offset relative to @var{address} at which to start reading. This
31255 should be an integer literal. This option is provided so that a frontend
31256 is not required to first evaluate address and then perform address
31257 arithmetics itself.
31261 This command attempts to read all accessible memory regions in the
31262 specified range. First, all regions marked as unreadable in the memory
31263 map (if one is defined) will be skipped. @xref{Memory Region
31264 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31265 regions. For each one, if reading full region results in an errors,
31266 @value{GDBN} will try to read a subset of the region.
31268 In general, every single memory unit in the region may be readable or not,
31269 and the only way to read every readable unit is to try a read at
31270 every address, which is not practical. Therefore, @value{GDBN} will
31271 attempt to read all accessible memory units at either beginning or the end
31272 of the region, using a binary division scheme. This heuristic works
31273 well for reading accross a memory map boundary. Note that if a region
31274 has a readable range that is neither at the beginning or the end,
31275 @value{GDBN} will not read it.
31277 The result record (@pxref{GDB/MI Result Records}) that is output of
31278 the command includes a field named @samp{memory} whose content is a
31279 list of tuples. Each tuple represent a successfully read memory block
31280 and has the following fields:
31284 The start address of the memory block, as hexadecimal literal.
31287 The end address of the memory block, as hexadecimal literal.
31290 The offset of the memory block, as hexadecimal literal, relative to
31291 the start address passed to @code{-data-read-memory-bytes}.
31294 The contents of the memory block, in hex.
31300 @subsubheading @value{GDBN} Command
31302 The corresponding @value{GDBN} command is @samp{x}.
31304 @subsubheading Example
31308 -data-read-memory-bytes &a 10
31309 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31311 contents="01000000020000000300"@}]
31316 @subheading The @code{-data-write-memory-bytes} Command
31317 @findex -data-write-memory-bytes
31319 @subsubheading Synopsis
31322 -data-write-memory-bytes @var{address} @var{contents}
31323 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31330 @item @var{address}
31331 An expression specifying the address of the first addressable memory unit
31332 to be written. Complex expressions containing embedded white space should
31333 be quoted using the C convention.
31335 @item @var{contents}
31336 The hex-encoded data to write. It is an error if @var{contents} does
31337 not represent an integral number of addressable memory units.
31340 Optional argument indicating the number of addressable memory units to be
31341 written. If @var{count} is greater than @var{contents}' length,
31342 @value{GDBN} will repeatedly write @var{contents} until it fills
31343 @var{count} memory units.
31347 @subsubheading @value{GDBN} Command
31349 There's no corresponding @value{GDBN} command.
31351 @subsubheading Example
31355 -data-write-memory-bytes &a "aabbccdd"
31362 -data-write-memory-bytes &a "aabbccdd" 16e
31367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31368 @node GDB/MI Tracepoint Commands
31369 @section @sc{gdb/mi} Tracepoint Commands
31371 The commands defined in this section implement MI support for
31372 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31374 @subheading The @code{-trace-find} Command
31375 @findex -trace-find
31377 @subsubheading Synopsis
31380 -trace-find @var{mode} [@var{parameters}@dots{}]
31383 Find a trace frame using criteria defined by @var{mode} and
31384 @var{parameters}. The following table lists permissible
31385 modes and their parameters. For details of operation, see @ref{tfind}.
31390 No parameters are required. Stops examining trace frames.
31393 An integer is required as parameter. Selects tracepoint frame with
31396 @item tracepoint-number
31397 An integer is required as parameter. Finds next
31398 trace frame that corresponds to tracepoint with the specified number.
31401 An address is required as parameter. Finds
31402 next trace frame that corresponds to any tracepoint at the specified
31405 @item pc-inside-range
31406 Two addresses are required as parameters. Finds next trace
31407 frame that corresponds to a tracepoint at an address inside the
31408 specified range. Both bounds are considered to be inside the range.
31410 @item pc-outside-range
31411 Two addresses are required as parameters. Finds
31412 next trace frame that corresponds to a tracepoint at an address outside
31413 the specified range. Both bounds are considered to be inside the range.
31416 Line specification is required as parameter. @xref{Specify Location}.
31417 Finds next trace frame that corresponds to a tracepoint at
31418 the specified location.
31422 If @samp{none} was passed as @var{mode}, the response does not
31423 have fields. Otherwise, the response may have the following fields:
31427 This field has either @samp{0} or @samp{1} as the value, depending
31428 on whether a matching tracepoint was found.
31431 The index of the found traceframe. This field is present iff
31432 the @samp{found} field has value of @samp{1}.
31435 The index of the found tracepoint. This field is present iff
31436 the @samp{found} field has value of @samp{1}.
31439 The information about the frame corresponding to the found trace
31440 frame. This field is present only if a trace frame was found.
31441 @xref{GDB/MI Frame Information}, for description of this field.
31445 @subsubheading @value{GDBN} Command
31447 The corresponding @value{GDBN} command is @samp{tfind}.
31449 @subheading -trace-define-variable
31450 @findex -trace-define-variable
31452 @subsubheading Synopsis
31455 -trace-define-variable @var{name} [ @var{value} ]
31458 Create trace variable @var{name} if it does not exist. If
31459 @var{value} is specified, sets the initial value of the specified
31460 trace variable to that value. Note that the @var{name} should start
31461 with the @samp{$} character.
31463 @subsubheading @value{GDBN} Command
31465 The corresponding @value{GDBN} command is @samp{tvariable}.
31467 @subheading The @code{-trace-frame-collected} Command
31468 @findex -trace-frame-collected
31470 @subsubheading Synopsis
31473 -trace-frame-collected
31474 [--var-print-values @var{var_pval}]
31475 [--comp-print-values @var{comp_pval}]
31476 [--registers-format @var{regformat}]
31477 [--memory-contents]
31480 This command returns the set of collected objects, register names,
31481 trace state variable names, memory ranges and computed expressions
31482 that have been collected at a particular trace frame. The optional
31483 parameters to the command affect the output format in different ways.
31484 See the output description table below for more details.
31486 The reported names can be used in the normal manner to create
31487 varobjs and inspect the objects themselves. The items returned by
31488 this command are categorized so that it is clear which is a variable,
31489 which is a register, which is a trace state variable, which is a
31490 memory range and which is a computed expression.
31492 For instance, if the actions were
31494 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31495 collect *(int*)0xaf02bef0@@40
31499 the object collected in its entirety would be @code{myVar}. The
31500 object @code{myArray} would be partially collected, because only the
31501 element at index @code{myIndex} would be collected. The remaining
31502 objects would be computed expressions.
31504 An example output would be:
31508 -trace-frame-collected
31510 explicit-variables=[@{name="myVar",value="1"@}],
31511 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31512 @{name="myObj.field",value="0"@},
31513 @{name="myPtr->field",value="1"@},
31514 @{name="myCount + 2",value="3"@},
31515 @{name="$tvar1 + 1",value="43970027"@}],
31516 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31517 @{number="1",value="0x0"@},
31518 @{number="2",value="0x4"@},
31520 @{number="125",value="0x0"@}],
31521 tvars=[@{name="$tvar1",current="43970026"@}],
31522 memory=[@{address="0x0000000000602264",length="4"@},
31523 @{address="0x0000000000615bc0",length="4"@}]
31530 @item explicit-variables
31531 The set of objects that have been collected in their entirety (as
31532 opposed to collecting just a few elements of an array or a few struct
31533 members). For each object, its name and value are printed.
31534 The @code{--var-print-values} option affects how or whether the value
31535 field is output. If @var{var_pval} is 0, then print only the names;
31536 if it is 1, print also their values; and if it is 2, print the name,
31537 type and value for simple data types, and the name and type for
31538 arrays, structures and unions.
31540 @item computed-expressions
31541 The set of computed expressions that have been collected at the
31542 current trace frame. The @code{--comp-print-values} option affects
31543 this set like the @code{--var-print-values} option affects the
31544 @code{explicit-variables} set. See above.
31547 The registers that have been collected at the current trace frame.
31548 For each register collected, the name and current value are returned.
31549 The value is formatted according to the @code{--registers-format}
31550 option. See the @command{-data-list-register-values} command for a
31551 list of the allowed formats. The default is @samp{x}.
31554 The trace state variables that have been collected at the current
31555 trace frame. For each trace state variable collected, the name and
31556 current value are returned.
31559 The set of memory ranges that have been collected at the current trace
31560 frame. Its content is a list of tuples. Each tuple represents a
31561 collected memory range and has the following fields:
31565 The start address of the memory range, as hexadecimal literal.
31568 The length of the memory range, as decimal literal.
31571 The contents of the memory block, in hex. This field is only present
31572 if the @code{--memory-contents} option is specified.
31578 @subsubheading @value{GDBN} Command
31580 There is no corresponding @value{GDBN} command.
31582 @subsubheading Example
31584 @subheading -trace-list-variables
31585 @findex -trace-list-variables
31587 @subsubheading Synopsis
31590 -trace-list-variables
31593 Return a table of all defined trace variables. Each element of the
31594 table has the following fields:
31598 The name of the trace variable. This field is always present.
31601 The initial value. This is a 64-bit signed integer. This
31602 field is always present.
31605 The value the trace variable has at the moment. This is a 64-bit
31606 signed integer. This field is absent iff current value is
31607 not defined, for example if the trace was never run, or is
31612 @subsubheading @value{GDBN} Command
31614 The corresponding @value{GDBN} command is @samp{tvariables}.
31616 @subsubheading Example
31620 -trace-list-variables
31621 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31622 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31623 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31624 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31625 body=[variable=@{name="$trace_timestamp",initial="0"@}
31626 variable=@{name="$foo",initial="10",current="15"@}]@}
31630 @subheading -trace-save
31631 @findex -trace-save
31633 @subsubheading Synopsis
31636 -trace-save [ -r ] [ -ctf ] @var{filename}
31639 Saves the collected trace data to @var{filename}. Without the
31640 @samp{-r} option, the data is downloaded from the target and saved
31641 in a local file. With the @samp{-r} option the target is asked
31642 to perform the save.
31644 By default, this command will save the trace in the tfile format. You can
31645 supply the optional @samp{-ctf} argument to save it the CTF format. See
31646 @ref{Trace Files} for more information about CTF.
31648 @subsubheading @value{GDBN} Command
31650 The corresponding @value{GDBN} command is @samp{tsave}.
31653 @subheading -trace-start
31654 @findex -trace-start
31656 @subsubheading Synopsis
31662 Starts a tracing experiment. The result of this command does not
31665 @subsubheading @value{GDBN} Command
31667 The corresponding @value{GDBN} command is @samp{tstart}.
31669 @subheading -trace-status
31670 @findex -trace-status
31672 @subsubheading Synopsis
31678 Obtains the status of a tracing experiment. The result may include
31679 the following fields:
31684 May have a value of either @samp{0}, when no tracing operations are
31685 supported, @samp{1}, when all tracing operations are supported, or
31686 @samp{file} when examining trace file. In the latter case, examining
31687 of trace frame is possible but new tracing experiement cannot be
31688 started. This field is always present.
31691 May have a value of either @samp{0} or @samp{1} depending on whether
31692 tracing experiement is in progress on target. This field is present
31693 if @samp{supported} field is not @samp{0}.
31696 Report the reason why the tracing was stopped last time. This field
31697 may be absent iff tracing was never stopped on target yet. The
31698 value of @samp{request} means the tracing was stopped as result of
31699 the @code{-trace-stop} command. The value of @samp{overflow} means
31700 the tracing buffer is full. The value of @samp{disconnection} means
31701 tracing was automatically stopped when @value{GDBN} has disconnected.
31702 The value of @samp{passcount} means tracing was stopped when a
31703 tracepoint was passed a maximal number of times for that tracepoint.
31704 This field is present if @samp{supported} field is not @samp{0}.
31706 @item stopping-tracepoint
31707 The number of tracepoint whose passcount as exceeded. This field is
31708 present iff the @samp{stop-reason} field has the value of
31712 @itemx frames-created
31713 The @samp{frames} field is a count of the total number of trace frames
31714 in the trace buffer, while @samp{frames-created} is the total created
31715 during the run, including ones that were discarded, such as when a
31716 circular trace buffer filled up. Both fields are optional.
31720 These fields tell the current size of the tracing buffer and the
31721 remaining space. These fields are optional.
31724 The value of the circular trace buffer flag. @code{1} means that the
31725 trace buffer is circular and old trace frames will be discarded if
31726 necessary to make room, @code{0} means that the trace buffer is linear
31730 The value of the disconnected tracing flag. @code{1} means that
31731 tracing will continue after @value{GDBN} disconnects, @code{0} means
31732 that the trace run will stop.
31735 The filename of the trace file being examined. This field is
31736 optional, and only present when examining a trace file.
31740 @subsubheading @value{GDBN} Command
31742 The corresponding @value{GDBN} command is @samp{tstatus}.
31744 @subheading -trace-stop
31745 @findex -trace-stop
31747 @subsubheading Synopsis
31753 Stops a tracing experiment. The result of this command has the same
31754 fields as @code{-trace-status}, except that the @samp{supported} and
31755 @samp{running} fields are not output.
31757 @subsubheading @value{GDBN} Command
31759 The corresponding @value{GDBN} command is @samp{tstop}.
31762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31763 @node GDB/MI Symbol Query
31764 @section @sc{gdb/mi} Symbol Query Commands
31768 @subheading The @code{-symbol-info-address} Command
31769 @findex -symbol-info-address
31771 @subsubheading Synopsis
31774 -symbol-info-address @var{symbol}
31777 Describe where @var{symbol} is stored.
31779 @subsubheading @value{GDBN} Command
31781 The corresponding @value{GDBN} command is @samp{info address}.
31783 @subsubheading Example
31787 @subheading The @code{-symbol-info-file} Command
31788 @findex -symbol-info-file
31790 @subsubheading Synopsis
31796 Show the file for the symbol.
31798 @subsubheading @value{GDBN} Command
31800 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31801 @samp{gdb_find_file}.
31803 @subsubheading Example
31807 @subheading The @code{-symbol-info-function} Command
31808 @findex -symbol-info-function
31810 @subsubheading Synopsis
31813 -symbol-info-function
31816 Show which function the symbol lives in.
31818 @subsubheading @value{GDBN} Command
31820 @samp{gdb_get_function} in @code{gdbtk}.
31822 @subsubheading Example
31826 @subheading The @code{-symbol-info-line} Command
31827 @findex -symbol-info-line
31829 @subsubheading Synopsis
31835 Show the core addresses of the code for a source line.
31837 @subsubheading @value{GDBN} Command
31839 The corresponding @value{GDBN} command is @samp{info line}.
31840 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31842 @subsubheading Example
31846 @subheading The @code{-symbol-info-symbol} Command
31847 @findex -symbol-info-symbol
31849 @subsubheading Synopsis
31852 -symbol-info-symbol @var{addr}
31855 Describe what symbol is at location @var{addr}.
31857 @subsubheading @value{GDBN} Command
31859 The corresponding @value{GDBN} command is @samp{info symbol}.
31861 @subsubheading Example
31865 @subheading The @code{-symbol-list-functions} Command
31866 @findex -symbol-list-functions
31868 @subsubheading Synopsis
31871 -symbol-list-functions
31874 List the functions in the executable.
31876 @subsubheading @value{GDBN} Command
31878 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31879 @samp{gdb_search} in @code{gdbtk}.
31881 @subsubheading Example
31886 @subheading The @code{-symbol-list-lines} Command
31887 @findex -symbol-list-lines
31889 @subsubheading Synopsis
31892 -symbol-list-lines @var{filename}
31895 Print the list of lines that contain code and their associated program
31896 addresses for the given source filename. The entries are sorted in
31897 ascending PC order.
31899 @subsubheading @value{GDBN} Command
31901 There is no corresponding @value{GDBN} command.
31903 @subsubheading Example
31906 -symbol-list-lines basics.c
31907 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31913 @subheading The @code{-symbol-list-types} Command
31914 @findex -symbol-list-types
31916 @subsubheading Synopsis
31922 List all the type names.
31924 @subsubheading @value{GDBN} Command
31926 The corresponding commands are @samp{info types} in @value{GDBN},
31927 @samp{gdb_search} in @code{gdbtk}.
31929 @subsubheading Example
31933 @subheading The @code{-symbol-list-variables} Command
31934 @findex -symbol-list-variables
31936 @subsubheading Synopsis
31939 -symbol-list-variables
31942 List all the global and static variable names.
31944 @subsubheading @value{GDBN} Command
31946 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31948 @subsubheading Example
31952 @subheading The @code{-symbol-locate} Command
31953 @findex -symbol-locate
31955 @subsubheading Synopsis
31961 @subsubheading @value{GDBN} Command
31963 @samp{gdb_loc} in @code{gdbtk}.
31965 @subsubheading Example
31969 @subheading The @code{-symbol-type} Command
31970 @findex -symbol-type
31972 @subsubheading Synopsis
31975 -symbol-type @var{variable}
31978 Show type of @var{variable}.
31980 @subsubheading @value{GDBN} Command
31982 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31983 @samp{gdb_obj_variable}.
31985 @subsubheading Example
31990 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31991 @node GDB/MI File Commands
31992 @section @sc{gdb/mi} File Commands
31994 This section describes the GDB/MI commands to specify executable file names
31995 and to read in and obtain symbol table information.
31997 @subheading The @code{-file-exec-and-symbols} Command
31998 @findex -file-exec-and-symbols
32000 @subsubheading Synopsis
32003 -file-exec-and-symbols @var{file}
32006 Specify the executable file to be debugged. This file is the one from
32007 which the symbol table is also read. If no file is specified, the
32008 command clears the executable and symbol information. If breakpoints
32009 are set when using this command with no arguments, @value{GDBN} will produce
32010 error messages. Otherwise, no output is produced, except a completion
32013 @subsubheading @value{GDBN} Command
32015 The corresponding @value{GDBN} command is @samp{file}.
32017 @subsubheading Example
32021 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32027 @subheading The @code{-file-exec-file} Command
32028 @findex -file-exec-file
32030 @subsubheading Synopsis
32033 -file-exec-file @var{file}
32036 Specify the executable file to be debugged. Unlike
32037 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32038 from this file. If used without argument, @value{GDBN} clears the information
32039 about the executable file. No output is produced, except a completion
32042 @subsubheading @value{GDBN} Command
32044 The corresponding @value{GDBN} command is @samp{exec-file}.
32046 @subsubheading Example
32050 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32057 @subheading The @code{-file-list-exec-sections} Command
32058 @findex -file-list-exec-sections
32060 @subsubheading Synopsis
32063 -file-list-exec-sections
32066 List the sections of the current executable file.
32068 @subsubheading @value{GDBN} Command
32070 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32071 information as this command. @code{gdbtk} has a corresponding command
32072 @samp{gdb_load_info}.
32074 @subsubheading Example
32079 @subheading The @code{-file-list-exec-source-file} Command
32080 @findex -file-list-exec-source-file
32082 @subsubheading Synopsis
32085 -file-list-exec-source-file
32088 List the line number, the current source file, and the absolute path
32089 to the current source file for the current executable. The macro
32090 information field has a value of @samp{1} or @samp{0} depending on
32091 whether or not the file includes preprocessor macro information.
32093 @subsubheading @value{GDBN} Command
32095 The @value{GDBN} equivalent is @samp{info source}
32097 @subsubheading Example
32101 123-file-list-exec-source-file
32102 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32107 @subheading The @code{-file-list-exec-source-files} Command
32108 @findex -file-list-exec-source-files
32110 @subsubheading Synopsis
32113 -file-list-exec-source-files
32116 List the source files for the current executable.
32118 It will always output both the filename and fullname (absolute file
32119 name) of a source file.
32121 @subsubheading @value{GDBN} Command
32123 The @value{GDBN} equivalent is @samp{info sources}.
32124 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32126 @subsubheading Example
32129 -file-list-exec-source-files
32131 @{file=foo.c,fullname=/home/foo.c@},
32132 @{file=/home/bar.c,fullname=/home/bar.c@},
32133 @{file=gdb_could_not_find_fullpath.c@}]
32137 @subheading The @code{-file-list-shared-libraries} Command
32138 @findex -file-list-shared-libraries
32140 @subsubheading Synopsis
32143 -file-list-shared-libraries [ @var{regexp} ]
32146 List the shared libraries in the program.
32147 With a regular expression @var{regexp}, only those libraries whose
32148 names match @var{regexp} are listed.
32150 @subsubheading @value{GDBN} Command
32152 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32153 have a similar meaning to the @code{=library-loaded} notification.
32154 The @code{ranges} field specifies the multiple segments belonging to this
32155 library. Each range has the following fields:
32159 The address defining the inclusive lower bound of the segment.
32161 The address defining the exclusive upper bound of the segment.
32164 @subsubheading Example
32167 -file-list-exec-source-files
32168 ^done,shared-libraries=[
32169 @{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"@}]@},
32170 @{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"@}]@}]
32176 @subheading The @code{-file-list-symbol-files} Command
32177 @findex -file-list-symbol-files
32179 @subsubheading Synopsis
32182 -file-list-symbol-files
32187 @subsubheading @value{GDBN} Command
32189 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32191 @subsubheading Example
32196 @subheading The @code{-file-symbol-file} Command
32197 @findex -file-symbol-file
32199 @subsubheading Synopsis
32202 -file-symbol-file @var{file}
32205 Read symbol table info from the specified @var{file} argument. When
32206 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32207 produced, except for a completion notification.
32209 @subsubheading @value{GDBN} Command
32211 The corresponding @value{GDBN} command is @samp{symbol-file}.
32213 @subsubheading Example
32217 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32224 @node GDB/MI Memory Overlay Commands
32225 @section @sc{gdb/mi} Memory Overlay Commands
32227 The memory overlay commands are not implemented.
32229 @c @subheading -overlay-auto
32231 @c @subheading -overlay-list-mapping-state
32233 @c @subheading -overlay-list-overlays
32235 @c @subheading -overlay-map
32237 @c @subheading -overlay-off
32239 @c @subheading -overlay-on
32241 @c @subheading -overlay-unmap
32243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32244 @node GDB/MI Signal Handling Commands
32245 @section @sc{gdb/mi} Signal Handling Commands
32247 Signal handling commands are not implemented.
32249 @c @subheading -signal-handle
32251 @c @subheading -signal-list-handle-actions
32253 @c @subheading -signal-list-signal-types
32257 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32258 @node GDB/MI Target Manipulation
32259 @section @sc{gdb/mi} Target Manipulation Commands
32262 @subheading The @code{-target-attach} Command
32263 @findex -target-attach
32265 @subsubheading Synopsis
32268 -target-attach @var{pid} | @var{gid} | @var{file}
32271 Attach to a process @var{pid} or a file @var{file} outside of
32272 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32273 group, the id previously returned by
32274 @samp{-list-thread-groups --available} must be used.
32276 @subsubheading @value{GDBN} Command
32278 The corresponding @value{GDBN} command is @samp{attach}.
32280 @subsubheading Example
32284 =thread-created,id="1"
32285 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32291 @subheading The @code{-target-compare-sections} Command
32292 @findex -target-compare-sections
32294 @subsubheading Synopsis
32297 -target-compare-sections [ @var{section} ]
32300 Compare data of section @var{section} on target to the exec file.
32301 Without the argument, all sections are compared.
32303 @subsubheading @value{GDBN} Command
32305 The @value{GDBN} equivalent is @samp{compare-sections}.
32307 @subsubheading Example
32312 @subheading The @code{-target-detach} Command
32313 @findex -target-detach
32315 @subsubheading Synopsis
32318 -target-detach [ @var{pid} | @var{gid} ]
32321 Detach from the remote target which normally resumes its execution.
32322 If either @var{pid} or @var{gid} is specified, detaches from either
32323 the specified process, or specified thread group. There's no output.
32325 @subsubheading @value{GDBN} Command
32327 The corresponding @value{GDBN} command is @samp{detach}.
32329 @subsubheading Example
32339 @subheading The @code{-target-disconnect} Command
32340 @findex -target-disconnect
32342 @subsubheading Synopsis
32348 Disconnect from the remote target. There's no output and the target is
32349 generally not resumed.
32351 @subsubheading @value{GDBN} Command
32353 The corresponding @value{GDBN} command is @samp{disconnect}.
32355 @subsubheading Example
32365 @subheading The @code{-target-download} Command
32366 @findex -target-download
32368 @subsubheading Synopsis
32374 Loads the executable onto the remote target.
32375 It prints out an update message every half second, which includes the fields:
32379 The name of the section.
32381 The size of what has been sent so far for that section.
32383 The size of the section.
32385 The total size of what was sent so far (the current and the previous sections).
32387 The size of the overall executable to download.
32391 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32392 @sc{gdb/mi} Output Syntax}).
32394 In addition, it prints the name and size of the sections, as they are
32395 downloaded. These messages include the following fields:
32399 The name of the section.
32401 The size of the section.
32403 The size of the overall executable to download.
32407 At the end, a summary is printed.
32409 @subsubheading @value{GDBN} Command
32411 The corresponding @value{GDBN} command is @samp{load}.
32413 @subsubheading Example
32415 Note: each status message appears on a single line. Here the messages
32416 have been broken down so that they can fit onto a page.
32421 +download,@{section=".text",section-size="6668",total-size="9880"@}
32422 +download,@{section=".text",section-sent="512",section-size="6668",
32423 total-sent="512",total-size="9880"@}
32424 +download,@{section=".text",section-sent="1024",section-size="6668",
32425 total-sent="1024",total-size="9880"@}
32426 +download,@{section=".text",section-sent="1536",section-size="6668",
32427 total-sent="1536",total-size="9880"@}
32428 +download,@{section=".text",section-sent="2048",section-size="6668",
32429 total-sent="2048",total-size="9880"@}
32430 +download,@{section=".text",section-sent="2560",section-size="6668",
32431 total-sent="2560",total-size="9880"@}
32432 +download,@{section=".text",section-sent="3072",section-size="6668",
32433 total-sent="3072",total-size="9880"@}
32434 +download,@{section=".text",section-sent="3584",section-size="6668",
32435 total-sent="3584",total-size="9880"@}
32436 +download,@{section=".text",section-sent="4096",section-size="6668",
32437 total-sent="4096",total-size="9880"@}
32438 +download,@{section=".text",section-sent="4608",section-size="6668",
32439 total-sent="4608",total-size="9880"@}
32440 +download,@{section=".text",section-sent="5120",section-size="6668",
32441 total-sent="5120",total-size="9880"@}
32442 +download,@{section=".text",section-sent="5632",section-size="6668",
32443 total-sent="5632",total-size="9880"@}
32444 +download,@{section=".text",section-sent="6144",section-size="6668",
32445 total-sent="6144",total-size="9880"@}
32446 +download,@{section=".text",section-sent="6656",section-size="6668",
32447 total-sent="6656",total-size="9880"@}
32448 +download,@{section=".init",section-size="28",total-size="9880"@}
32449 +download,@{section=".fini",section-size="28",total-size="9880"@}
32450 +download,@{section=".data",section-size="3156",total-size="9880"@}
32451 +download,@{section=".data",section-sent="512",section-size="3156",
32452 total-sent="7236",total-size="9880"@}
32453 +download,@{section=".data",section-sent="1024",section-size="3156",
32454 total-sent="7748",total-size="9880"@}
32455 +download,@{section=".data",section-sent="1536",section-size="3156",
32456 total-sent="8260",total-size="9880"@}
32457 +download,@{section=".data",section-sent="2048",section-size="3156",
32458 total-sent="8772",total-size="9880"@}
32459 +download,@{section=".data",section-sent="2560",section-size="3156",
32460 total-sent="9284",total-size="9880"@}
32461 +download,@{section=".data",section-sent="3072",section-size="3156",
32462 total-sent="9796",total-size="9880"@}
32463 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32470 @subheading The @code{-target-exec-status} Command
32471 @findex -target-exec-status
32473 @subsubheading Synopsis
32476 -target-exec-status
32479 Provide information on the state of the target (whether it is running or
32480 not, for instance).
32482 @subsubheading @value{GDBN} Command
32484 There's no equivalent @value{GDBN} command.
32486 @subsubheading Example
32490 @subheading The @code{-target-list-available-targets} Command
32491 @findex -target-list-available-targets
32493 @subsubheading Synopsis
32496 -target-list-available-targets
32499 List the possible targets to connect to.
32501 @subsubheading @value{GDBN} Command
32503 The corresponding @value{GDBN} command is @samp{help target}.
32505 @subsubheading Example
32509 @subheading The @code{-target-list-current-targets} Command
32510 @findex -target-list-current-targets
32512 @subsubheading Synopsis
32515 -target-list-current-targets
32518 Describe the current target.
32520 @subsubheading @value{GDBN} Command
32522 The corresponding information is printed by @samp{info file} (among
32525 @subsubheading Example
32529 @subheading The @code{-target-list-parameters} Command
32530 @findex -target-list-parameters
32532 @subsubheading Synopsis
32535 -target-list-parameters
32541 @subsubheading @value{GDBN} Command
32545 @subsubheading Example
32548 @subheading The @code{-target-flash-erase} Command
32549 @findex -target-flash-erase
32551 @subsubheading Synopsis
32554 -target-flash-erase
32557 Erases all known flash memory regions on the target.
32559 The corresponding @value{GDBN} command is @samp{flash-erase}.
32561 The output is a list of flash regions that have been erased, with starting
32562 addresses and memory region sizes.
32566 -target-flash-erase
32567 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32571 @subheading The @code{-target-select} Command
32572 @findex -target-select
32574 @subsubheading Synopsis
32577 -target-select @var{type} @var{parameters @dots{}}
32580 Connect @value{GDBN} to the remote target. This command takes two args:
32584 The type of target, for instance @samp{remote}, etc.
32585 @item @var{parameters}
32586 Device names, host names and the like. @xref{Target Commands, ,
32587 Commands for Managing Targets}, for more details.
32590 The output is a connection notification, followed by the address at
32591 which the target program is, in the following form:
32594 ^connected,addr="@var{address}",func="@var{function name}",
32595 args=[@var{arg list}]
32598 @subsubheading @value{GDBN} Command
32600 The corresponding @value{GDBN} command is @samp{target}.
32602 @subsubheading Example
32606 -target-select remote /dev/ttya
32607 ^connected,addr="0xfe00a300",func="??",args=[]
32611 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32612 @node GDB/MI File Transfer Commands
32613 @section @sc{gdb/mi} File Transfer Commands
32616 @subheading The @code{-target-file-put} Command
32617 @findex -target-file-put
32619 @subsubheading Synopsis
32622 -target-file-put @var{hostfile} @var{targetfile}
32625 Copy file @var{hostfile} from the host system (the machine running
32626 @value{GDBN}) to @var{targetfile} on the target system.
32628 @subsubheading @value{GDBN} Command
32630 The corresponding @value{GDBN} command is @samp{remote put}.
32632 @subsubheading Example
32636 -target-file-put localfile remotefile
32642 @subheading The @code{-target-file-get} Command
32643 @findex -target-file-get
32645 @subsubheading Synopsis
32648 -target-file-get @var{targetfile} @var{hostfile}
32651 Copy file @var{targetfile} from the target system to @var{hostfile}
32652 on the host system.
32654 @subsubheading @value{GDBN} Command
32656 The corresponding @value{GDBN} command is @samp{remote get}.
32658 @subsubheading Example
32662 -target-file-get remotefile localfile
32668 @subheading The @code{-target-file-delete} Command
32669 @findex -target-file-delete
32671 @subsubheading Synopsis
32674 -target-file-delete @var{targetfile}
32677 Delete @var{targetfile} from the target system.
32679 @subsubheading @value{GDBN} Command
32681 The corresponding @value{GDBN} command is @samp{remote delete}.
32683 @subsubheading Example
32687 -target-file-delete remotefile
32693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32694 @node GDB/MI Ada Exceptions Commands
32695 @section Ada Exceptions @sc{gdb/mi} Commands
32697 @subheading The @code{-info-ada-exceptions} Command
32698 @findex -info-ada-exceptions
32700 @subsubheading Synopsis
32703 -info-ada-exceptions [ @var{regexp}]
32706 List all Ada exceptions defined within the program being debugged.
32707 With a regular expression @var{regexp}, only those exceptions whose
32708 names match @var{regexp} are listed.
32710 @subsubheading @value{GDBN} Command
32712 The corresponding @value{GDBN} command is @samp{info exceptions}.
32714 @subsubheading Result
32716 The result is a table of Ada exceptions. The following columns are
32717 defined for each exception:
32721 The name of the exception.
32724 The address of the exception.
32728 @subsubheading Example
32731 -info-ada-exceptions aint
32732 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32733 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32734 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32735 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32736 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32739 @subheading Catching Ada Exceptions
32741 The commands describing how to ask @value{GDBN} to stop when a program
32742 raises an exception are described at @ref{Ada Exception GDB/MI
32743 Catchpoint Commands}.
32746 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32747 @node GDB/MI Support Commands
32748 @section @sc{gdb/mi} Support Commands
32750 Since new commands and features get regularly added to @sc{gdb/mi},
32751 some commands are available to help front-ends query the debugger
32752 about support for these capabilities. Similarly, it is also possible
32753 to query @value{GDBN} about target support of certain features.
32755 @subheading The @code{-info-gdb-mi-command} Command
32756 @cindex @code{-info-gdb-mi-command}
32757 @findex -info-gdb-mi-command
32759 @subsubheading Synopsis
32762 -info-gdb-mi-command @var{cmd_name}
32765 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32767 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32768 is technically not part of the command name (@pxref{GDB/MI Input
32769 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32770 for ease of use, this command also accepts the form with the leading
32773 @subsubheading @value{GDBN} Command
32775 There is no corresponding @value{GDBN} command.
32777 @subsubheading Result
32779 The result is a tuple. There is currently only one field:
32783 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32784 @code{"false"} otherwise.
32788 @subsubheading Example
32790 Here is an example where the @sc{gdb/mi} command does not exist:
32793 -info-gdb-mi-command unsupported-command
32794 ^done,command=@{exists="false"@}
32798 And here is an example where the @sc{gdb/mi} command is known
32802 -info-gdb-mi-command symbol-list-lines
32803 ^done,command=@{exists="true"@}
32806 @subheading The @code{-list-features} Command
32807 @findex -list-features
32808 @cindex supported @sc{gdb/mi} features, list
32810 Returns a list of particular features of the MI protocol that
32811 this version of gdb implements. A feature can be a command,
32812 or a new field in an output of some command, or even an
32813 important bugfix. While a frontend can sometimes detect presence
32814 of a feature at runtime, it is easier to perform detection at debugger
32817 The command returns a list of strings, with each string naming an
32818 available feature. Each returned string is just a name, it does not
32819 have any internal structure. The list of possible feature names
32825 (gdb) -list-features
32826 ^done,result=["feature1","feature2"]
32829 The current list of features is:
32832 @item frozen-varobjs
32833 Indicates support for the @code{-var-set-frozen} command, as well
32834 as possible presense of the @code{frozen} field in the output
32835 of @code{-varobj-create}.
32836 @item pending-breakpoints
32837 Indicates support for the @option{-f} option to the @code{-break-insert}
32840 Indicates Python scripting support, Python-based
32841 pretty-printing commands, and possible presence of the
32842 @samp{display_hint} field in the output of @code{-var-list-children}
32844 Indicates support for the @code{-thread-info} command.
32845 @item data-read-memory-bytes
32846 Indicates support for the @code{-data-read-memory-bytes} and the
32847 @code{-data-write-memory-bytes} commands.
32848 @item breakpoint-notifications
32849 Indicates that changes to breakpoints and breakpoints created via the
32850 CLI will be announced via async records.
32851 @item ada-task-info
32852 Indicates support for the @code{-ada-task-info} command.
32853 @item language-option
32854 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32855 option (@pxref{Context management}).
32856 @item info-gdb-mi-command
32857 Indicates support for the @code{-info-gdb-mi-command} command.
32858 @item undefined-command-error-code
32859 Indicates support for the "undefined-command" error code in error result
32860 records, produced when trying to execute an undefined @sc{gdb/mi} command
32861 (@pxref{GDB/MI Result Records}).
32862 @item exec-run-start-option
32863 Indicates that the @code{-exec-run} command supports the @option{--start}
32864 option (@pxref{GDB/MI Program Execution}).
32867 @subheading The @code{-list-target-features} Command
32868 @findex -list-target-features
32870 Returns a list of particular features that are supported by the
32871 target. Those features affect the permitted MI commands, but
32872 unlike the features reported by the @code{-list-features} command, the
32873 features depend on which target GDB is using at the moment. Whenever
32874 a target can change, due to commands such as @code{-target-select},
32875 @code{-target-attach} or @code{-exec-run}, the list of target features
32876 may change, and the frontend should obtain it again.
32880 (gdb) -list-target-features
32881 ^done,result=["async"]
32884 The current list of features is:
32888 Indicates that the target is capable of asynchronous command
32889 execution, which means that @value{GDBN} will accept further commands
32890 while the target is running.
32893 Indicates that the target is capable of reverse execution.
32894 @xref{Reverse Execution}, for more information.
32898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32899 @node GDB/MI Miscellaneous Commands
32900 @section Miscellaneous @sc{gdb/mi} Commands
32902 @c @subheading -gdb-complete
32904 @subheading The @code{-gdb-exit} Command
32907 @subsubheading Synopsis
32913 Exit @value{GDBN} immediately.
32915 @subsubheading @value{GDBN} Command
32917 Approximately corresponds to @samp{quit}.
32919 @subsubheading Example
32929 @subheading The @code{-exec-abort} Command
32930 @findex -exec-abort
32932 @subsubheading Synopsis
32938 Kill the inferior running program.
32940 @subsubheading @value{GDBN} Command
32942 The corresponding @value{GDBN} command is @samp{kill}.
32944 @subsubheading Example
32949 @subheading The @code{-gdb-set} Command
32952 @subsubheading Synopsis
32958 Set an internal @value{GDBN} variable.
32959 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32961 @subsubheading @value{GDBN} Command
32963 The corresponding @value{GDBN} command is @samp{set}.
32965 @subsubheading Example
32975 @subheading The @code{-gdb-show} Command
32978 @subsubheading Synopsis
32984 Show the current value of a @value{GDBN} variable.
32986 @subsubheading @value{GDBN} Command
32988 The corresponding @value{GDBN} command is @samp{show}.
32990 @subsubheading Example
32999 @c @subheading -gdb-source
33002 @subheading The @code{-gdb-version} Command
33003 @findex -gdb-version
33005 @subsubheading Synopsis
33011 Show version information for @value{GDBN}. Used mostly in testing.
33013 @subsubheading @value{GDBN} Command
33015 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33016 default shows this information when you start an interactive session.
33018 @subsubheading Example
33020 @c This example modifies the actual output from GDB to avoid overfull
33026 ~Copyright 2000 Free Software Foundation, Inc.
33027 ~GDB is free software, covered by the GNU General Public License, and
33028 ~you are welcome to change it and/or distribute copies of it under
33029 ~ certain conditions.
33030 ~Type "show copying" to see the conditions.
33031 ~There is absolutely no warranty for GDB. Type "show warranty" for
33033 ~This GDB was configured as
33034 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33039 @subheading The @code{-list-thread-groups} Command
33040 @findex -list-thread-groups
33042 @subheading Synopsis
33045 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33048 Lists thread groups (@pxref{Thread groups}). When a single thread
33049 group is passed as the argument, lists the children of that group.
33050 When several thread group are passed, lists information about those
33051 thread groups. Without any parameters, lists information about all
33052 top-level thread groups.
33054 Normally, thread groups that are being debugged are reported.
33055 With the @samp{--available} option, @value{GDBN} reports thread groups
33056 available on the target.
33058 The output of this command may have either a @samp{threads} result or
33059 a @samp{groups} result. The @samp{thread} result has a list of tuples
33060 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33061 Information}). The @samp{groups} result has a list of tuples as value,
33062 each tuple describing a thread group. If top-level groups are
33063 requested (that is, no parameter is passed), or when several groups
33064 are passed, the output always has a @samp{groups} result. The format
33065 of the @samp{group} result is described below.
33067 To reduce the number of roundtrips it's possible to list thread groups
33068 together with their children, by passing the @samp{--recurse} option
33069 and the recursion depth. Presently, only recursion depth of 1 is
33070 permitted. If this option is present, then every reported thread group
33071 will also include its children, either as @samp{group} or
33072 @samp{threads} field.
33074 In general, any combination of option and parameters is permitted, with
33075 the following caveats:
33079 When a single thread group is passed, the output will typically
33080 be the @samp{threads} result. Because threads may not contain
33081 anything, the @samp{recurse} option will be ignored.
33084 When the @samp{--available} option is passed, limited information may
33085 be available. In particular, the list of threads of a process might
33086 be inaccessible. Further, specifying specific thread groups might
33087 not give any performance advantage over listing all thread groups.
33088 The frontend should assume that @samp{-list-thread-groups --available}
33089 is always an expensive operation and cache the results.
33093 The @samp{groups} result is a list of tuples, where each tuple may
33094 have the following fields:
33098 Identifier of the thread group. This field is always present.
33099 The identifier is an opaque string; frontends should not try to
33100 convert it to an integer, even though it might look like one.
33103 The type of the thread group. At present, only @samp{process} is a
33107 The target-specific process identifier. This field is only present
33108 for thread groups of type @samp{process} and only if the process exists.
33111 The exit code of this group's last exited thread, formatted in octal.
33112 This field is only present for thread groups of type @samp{process} and
33113 only if the process is not running.
33116 The number of children this thread group has. This field may be
33117 absent for an available thread group.
33120 This field has a list of tuples as value, each tuple describing a
33121 thread. It may be present if the @samp{--recurse} option is
33122 specified, and it's actually possible to obtain the threads.
33125 This field is a list of integers, each identifying a core that one
33126 thread of the group is running on. This field may be absent if
33127 such information is not available.
33130 The name of the executable file that corresponds to this thread group.
33131 The field is only present for thread groups of type @samp{process},
33132 and only if there is a corresponding executable file.
33136 @subheading Example
33140 -list-thread-groups
33141 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33142 -list-thread-groups 17
33143 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33144 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33145 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33146 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33147 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33148 -list-thread-groups --available
33149 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33150 -list-thread-groups --available --recurse 1
33151 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33152 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33153 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33154 -list-thread-groups --available --recurse 1 17 18
33155 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33156 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33157 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33160 @subheading The @code{-info-os} Command
33163 @subsubheading Synopsis
33166 -info-os [ @var{type} ]
33169 If no argument is supplied, the command returns a table of available
33170 operating-system-specific information types. If one of these types is
33171 supplied as an argument @var{type}, then the command returns a table
33172 of data of that type.
33174 The types of information available depend on the target operating
33177 @subsubheading @value{GDBN} Command
33179 The corresponding @value{GDBN} command is @samp{info os}.
33181 @subsubheading Example
33183 When run on a @sc{gnu}/Linux system, the output will look something
33189 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33190 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33191 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33192 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33193 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33195 item=@{col0="files",col1="Listing of all file descriptors",
33196 col2="File descriptors"@},
33197 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33198 col2="Kernel modules"@},
33199 item=@{col0="msg",col1="Listing of all message queues",
33200 col2="Message queues"@},
33201 item=@{col0="processes",col1="Listing of all processes",
33202 col2="Processes"@},
33203 item=@{col0="procgroups",col1="Listing of all process groups",
33204 col2="Process groups"@},
33205 item=@{col0="semaphores",col1="Listing of all semaphores",
33206 col2="Semaphores"@},
33207 item=@{col0="shm",col1="Listing of all shared-memory regions",
33208 col2="Shared-memory regions"@},
33209 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33211 item=@{col0="threads",col1="Listing of all threads",
33215 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33216 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33217 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33218 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33219 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33220 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33221 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33222 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33224 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33225 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33229 (Note that the MI output here includes a @code{"Title"} column that
33230 does not appear in command-line @code{info os}; this column is useful
33231 for MI clients that want to enumerate the types of data, such as in a
33232 popup menu, but is needless clutter on the command line, and
33233 @code{info os} omits it.)
33235 @subheading The @code{-add-inferior} Command
33236 @findex -add-inferior
33238 @subheading Synopsis
33244 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33245 inferior is not associated with any executable. Such association may
33246 be established with the @samp{-file-exec-and-symbols} command
33247 (@pxref{GDB/MI File Commands}). The command response has a single
33248 field, @samp{inferior}, whose value is the identifier of the
33249 thread group corresponding to the new inferior.
33251 @subheading Example
33256 ^done,inferior="i3"
33259 @subheading The @code{-interpreter-exec} Command
33260 @findex -interpreter-exec
33262 @subheading Synopsis
33265 -interpreter-exec @var{interpreter} @var{command}
33267 @anchor{-interpreter-exec}
33269 Execute the specified @var{command} in the given @var{interpreter}.
33271 @subheading @value{GDBN} Command
33273 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33275 @subheading Example
33279 -interpreter-exec console "break main"
33280 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33281 &"During symbol reading, bad structure-type format.\n"
33282 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33287 @subheading The @code{-inferior-tty-set} Command
33288 @findex -inferior-tty-set
33290 @subheading Synopsis
33293 -inferior-tty-set /dev/pts/1
33296 Set terminal for future runs of the program being debugged.
33298 @subheading @value{GDBN} Command
33300 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33302 @subheading Example
33306 -inferior-tty-set /dev/pts/1
33311 @subheading The @code{-inferior-tty-show} Command
33312 @findex -inferior-tty-show
33314 @subheading Synopsis
33320 Show terminal for future runs of program being debugged.
33322 @subheading @value{GDBN} Command
33324 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33326 @subheading Example
33330 -inferior-tty-set /dev/pts/1
33334 ^done,inferior_tty_terminal="/dev/pts/1"
33338 @subheading The @code{-enable-timings} Command
33339 @findex -enable-timings
33341 @subheading Synopsis
33344 -enable-timings [yes | no]
33347 Toggle the printing of the wallclock, user and system times for an MI
33348 command as a field in its output. This command is to help frontend
33349 developers optimize the performance of their code. No argument is
33350 equivalent to @samp{yes}.
33352 @subheading @value{GDBN} Command
33356 @subheading Example
33364 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33365 addr="0x080484ed",func="main",file="myprog.c",
33366 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33368 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33376 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33377 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33378 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33379 fullname="/home/nickrob/myprog.c",line="73"@}
33384 @chapter @value{GDBN} Annotations
33386 This chapter describes annotations in @value{GDBN}. Annotations were
33387 designed to interface @value{GDBN} to graphical user interfaces or other
33388 similar programs which want to interact with @value{GDBN} at a
33389 relatively high level.
33391 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33395 This is Edition @value{EDITION}, @value{DATE}.
33399 * Annotations Overview:: What annotations are; the general syntax.
33400 * Server Prefix:: Issuing a command without affecting user state.
33401 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33402 * Errors:: Annotations for error messages.
33403 * Invalidation:: Some annotations describe things now invalid.
33404 * Annotations for Running::
33405 Whether the program is running, how it stopped, etc.
33406 * Source Annotations:: Annotations describing source code.
33409 @node Annotations Overview
33410 @section What is an Annotation?
33411 @cindex annotations
33413 Annotations start with a newline character, two @samp{control-z}
33414 characters, and the name of the annotation. If there is no additional
33415 information associated with this annotation, the name of the annotation
33416 is followed immediately by a newline. If there is additional
33417 information, the name of the annotation is followed by a space, the
33418 additional information, and a newline. The additional information
33419 cannot contain newline characters.
33421 Any output not beginning with a newline and two @samp{control-z}
33422 characters denotes literal output from @value{GDBN}. Currently there is
33423 no need for @value{GDBN} to output a newline followed by two
33424 @samp{control-z} characters, but if there was such a need, the
33425 annotations could be extended with an @samp{escape} annotation which
33426 means those three characters as output.
33428 The annotation @var{level}, which is specified using the
33429 @option{--annotate} command line option (@pxref{Mode Options}), controls
33430 how much information @value{GDBN} prints together with its prompt,
33431 values of expressions, source lines, and other types of output. Level 0
33432 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33433 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33434 for programs that control @value{GDBN}, and level 2 annotations have
33435 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33436 Interface, annotate, GDB's Obsolete Annotations}).
33439 @kindex set annotate
33440 @item set annotate @var{level}
33441 The @value{GDBN} command @code{set annotate} sets the level of
33442 annotations to the specified @var{level}.
33444 @item show annotate
33445 @kindex show annotate
33446 Show the current annotation level.
33449 This chapter describes level 3 annotations.
33451 A simple example of starting up @value{GDBN} with annotations is:
33454 $ @kbd{gdb --annotate=3}
33456 Copyright 2003 Free Software Foundation, Inc.
33457 GDB is free software, covered by the GNU General Public License,
33458 and you are welcome to change it and/or distribute copies of it
33459 under certain conditions.
33460 Type "show copying" to see the conditions.
33461 There is absolutely no warranty for GDB. Type "show warranty"
33463 This GDB was configured as "i386-pc-linux-gnu"
33474 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33475 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33476 denotes a @samp{control-z} character) are annotations; the rest is
33477 output from @value{GDBN}.
33479 @node Server Prefix
33480 @section The Server Prefix
33481 @cindex server prefix
33483 If you prefix a command with @samp{server } then it will not affect
33484 the command history, nor will it affect @value{GDBN}'s notion of which
33485 command to repeat if @key{RET} is pressed on a line by itself. This
33486 means that commands can be run behind a user's back by a front-end in
33487 a transparent manner.
33489 The @code{server } prefix does not affect the recording of values into
33490 the value history; to print a value without recording it into the
33491 value history, use the @code{output} command instead of the
33492 @code{print} command.
33494 Using this prefix also disables confirmation requests
33495 (@pxref{confirmation requests}).
33498 @section Annotation for @value{GDBN} Input
33500 @cindex annotations for prompts
33501 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33502 to know when to send output, when the output from a given command is
33505 Different kinds of input each have a different @dfn{input type}. Each
33506 input type has three annotations: a @code{pre-} annotation, which
33507 denotes the beginning of any prompt which is being output, a plain
33508 annotation, which denotes the end of the prompt, and then a @code{post-}
33509 annotation which denotes the end of any echo which may (or may not) be
33510 associated with the input. For example, the @code{prompt} input type
33511 features the following annotations:
33519 The input types are
33522 @findex pre-prompt annotation
33523 @findex prompt annotation
33524 @findex post-prompt annotation
33526 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33528 @findex pre-commands annotation
33529 @findex commands annotation
33530 @findex post-commands annotation
33532 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33533 command. The annotations are repeated for each command which is input.
33535 @findex pre-overload-choice annotation
33536 @findex overload-choice annotation
33537 @findex post-overload-choice annotation
33538 @item overload-choice
33539 When @value{GDBN} wants the user to select between various overloaded functions.
33541 @findex pre-query annotation
33542 @findex query annotation
33543 @findex post-query annotation
33545 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33547 @findex pre-prompt-for-continue annotation
33548 @findex prompt-for-continue annotation
33549 @findex post-prompt-for-continue annotation
33550 @item prompt-for-continue
33551 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33552 expect this to work well; instead use @code{set height 0} to disable
33553 prompting. This is because the counting of lines is buggy in the
33554 presence of annotations.
33559 @cindex annotations for errors, warnings and interrupts
33561 @findex quit annotation
33566 This annotation occurs right before @value{GDBN} responds to an interrupt.
33568 @findex error annotation
33573 This annotation occurs right before @value{GDBN} responds to an error.
33575 Quit and error annotations indicate that any annotations which @value{GDBN} was
33576 in the middle of may end abruptly. For example, if a
33577 @code{value-history-begin} annotation is followed by a @code{error}, one
33578 cannot expect to receive the matching @code{value-history-end}. One
33579 cannot expect not to receive it either, however; an error annotation
33580 does not necessarily mean that @value{GDBN} is immediately returning all the way
33583 @findex error-begin annotation
33584 A quit or error annotation may be preceded by
33590 Any output between that and the quit or error annotation is the error
33593 Warning messages are not yet annotated.
33594 @c If we want to change that, need to fix warning(), type_error(),
33595 @c range_error(), and possibly other places.
33598 @section Invalidation Notices
33600 @cindex annotations for invalidation messages
33601 The following annotations say that certain pieces of state may have
33605 @findex frames-invalid annotation
33606 @item ^Z^Zframes-invalid
33608 The frames (for example, output from the @code{backtrace} command) may
33611 @findex breakpoints-invalid annotation
33612 @item ^Z^Zbreakpoints-invalid
33614 The breakpoints may have changed. For example, the user just added or
33615 deleted a breakpoint.
33618 @node Annotations for Running
33619 @section Running the Program
33620 @cindex annotations for running programs
33622 @findex starting annotation
33623 @findex stopping annotation
33624 When the program starts executing due to a @value{GDBN} command such as
33625 @code{step} or @code{continue},
33631 is output. When the program stops,
33637 is output. Before the @code{stopped} annotation, a variety of
33638 annotations describe how the program stopped.
33641 @findex exited annotation
33642 @item ^Z^Zexited @var{exit-status}
33643 The program exited, and @var{exit-status} is the exit status (zero for
33644 successful exit, otherwise nonzero).
33646 @findex signalled annotation
33647 @findex signal-name annotation
33648 @findex signal-name-end annotation
33649 @findex signal-string annotation
33650 @findex signal-string-end annotation
33651 @item ^Z^Zsignalled
33652 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33653 annotation continues:
33659 ^Z^Zsignal-name-end
33663 ^Z^Zsignal-string-end
33668 where @var{name} is the name of the signal, such as @code{SIGILL} or
33669 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33670 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33671 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33672 user's benefit and have no particular format.
33674 @findex signal annotation
33676 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33677 just saying that the program received the signal, not that it was
33678 terminated with it.
33680 @findex breakpoint annotation
33681 @item ^Z^Zbreakpoint @var{number}
33682 The program hit breakpoint number @var{number}.
33684 @findex watchpoint annotation
33685 @item ^Z^Zwatchpoint @var{number}
33686 The program hit watchpoint number @var{number}.
33689 @node Source Annotations
33690 @section Displaying Source
33691 @cindex annotations for source display
33693 @findex source annotation
33694 The following annotation is used instead of displaying source code:
33697 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33700 where @var{filename} is an absolute file name indicating which source
33701 file, @var{line} is the line number within that file (where 1 is the
33702 first line in the file), @var{character} is the character position
33703 within the file (where 0 is the first character in the file) (for most
33704 debug formats this will necessarily point to the beginning of a line),
33705 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33706 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33707 @var{addr} is the address in the target program associated with the
33708 source which is being displayed. The @var{addr} is in the form @samp{0x}
33709 followed by one or more lowercase hex digits (note that this does not
33710 depend on the language).
33712 @node JIT Interface
33713 @chapter JIT Compilation Interface
33714 @cindex just-in-time compilation
33715 @cindex JIT compilation interface
33717 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33718 interface. A JIT compiler is a program or library that generates native
33719 executable code at runtime and executes it, usually in order to achieve good
33720 performance while maintaining platform independence.
33722 Programs that use JIT compilation are normally difficult to debug because
33723 portions of their code are generated at runtime, instead of being loaded from
33724 object files, which is where @value{GDBN} normally finds the program's symbols
33725 and debug information. In order to debug programs that use JIT compilation,
33726 @value{GDBN} has an interface that allows the program to register in-memory
33727 symbol files with @value{GDBN} at runtime.
33729 If you are using @value{GDBN} to debug a program that uses this interface, then
33730 it should work transparently so long as you have not stripped the binary. If
33731 you are developing a JIT compiler, then the interface is documented in the rest
33732 of this chapter. At this time, the only known client of this interface is the
33735 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33736 JIT compiler communicates with @value{GDBN} by writing data into a global
33737 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33738 attaches, it reads a linked list of symbol files from the global variable to
33739 find existing code, and puts a breakpoint in the function so that it can find
33740 out about additional code.
33743 * Declarations:: Relevant C struct declarations
33744 * Registering Code:: Steps to register code
33745 * Unregistering Code:: Steps to unregister code
33746 * Custom Debug Info:: Emit debug information in a custom format
33750 @section JIT Declarations
33752 These are the relevant struct declarations that a C program should include to
33753 implement the interface:
33763 struct jit_code_entry
33765 struct jit_code_entry *next_entry;
33766 struct jit_code_entry *prev_entry;
33767 const char *symfile_addr;
33768 uint64_t symfile_size;
33771 struct jit_descriptor
33774 /* This type should be jit_actions_t, but we use uint32_t
33775 to be explicit about the bitwidth. */
33776 uint32_t action_flag;
33777 struct jit_code_entry *relevant_entry;
33778 struct jit_code_entry *first_entry;
33781 /* GDB puts a breakpoint in this function. */
33782 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33784 /* Make sure to specify the version statically, because the
33785 debugger may check the version before we can set it. */
33786 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33789 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33790 modifications to this global data properly, which can easily be done by putting
33791 a global mutex around modifications to these structures.
33793 @node Registering Code
33794 @section Registering Code
33796 To register code with @value{GDBN}, the JIT should follow this protocol:
33800 Generate an object file in memory with symbols and other desired debug
33801 information. The file must include the virtual addresses of the sections.
33804 Create a code entry for the file, which gives the start and size of the symbol
33808 Add it to the linked list in the JIT descriptor.
33811 Point the relevant_entry field of the descriptor at the entry.
33814 Set @code{action_flag} to @code{JIT_REGISTER} and call
33815 @code{__jit_debug_register_code}.
33818 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33819 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33820 new code. However, the linked list must still be maintained in order to allow
33821 @value{GDBN} to attach to a running process and still find the symbol files.
33823 @node Unregistering Code
33824 @section Unregistering Code
33826 If code is freed, then the JIT should use the following protocol:
33830 Remove the code entry corresponding to the code from the linked list.
33833 Point the @code{relevant_entry} field of the descriptor at the code entry.
33836 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33837 @code{__jit_debug_register_code}.
33840 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33841 and the JIT will leak the memory used for the associated symbol files.
33843 @node Custom Debug Info
33844 @section Custom Debug Info
33845 @cindex custom JIT debug info
33846 @cindex JIT debug info reader
33848 Generating debug information in platform-native file formats (like ELF
33849 or COFF) may be an overkill for JIT compilers; especially if all the
33850 debug info is used for is displaying a meaningful backtrace. The
33851 issue can be resolved by having the JIT writers decide on a debug info
33852 format and also provide a reader that parses the debug info generated
33853 by the JIT compiler. This section gives a brief overview on writing
33854 such a parser. More specific details can be found in the source file
33855 @file{gdb/jit-reader.in}, which is also installed as a header at
33856 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33858 The reader is implemented as a shared object (so this functionality is
33859 not available on platforms which don't allow loading shared objects at
33860 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33861 @code{jit-reader-unload} are provided, to be used to load and unload
33862 the readers from a preconfigured directory. Once loaded, the shared
33863 object is used the parse the debug information emitted by the JIT
33867 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33868 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33871 @node Using JIT Debug Info Readers
33872 @subsection Using JIT Debug Info Readers
33873 @kindex jit-reader-load
33874 @kindex jit-reader-unload
33876 Readers can be loaded and unloaded using the @code{jit-reader-load}
33877 and @code{jit-reader-unload} commands.
33880 @item jit-reader-load @var{reader}
33881 Load the JIT reader named @var{reader}, which is a shared
33882 object specified as either an absolute or a relative file name. In
33883 the latter case, @value{GDBN} will try to load the reader from a
33884 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33885 system (here @var{libdir} is the system library directory, often
33886 @file{/usr/local/lib}).
33888 Only one reader can be active at a time; trying to load a second
33889 reader when one is already loaded will result in @value{GDBN}
33890 reporting an error. A new JIT reader can be loaded by first unloading
33891 the current one using @code{jit-reader-unload} and then invoking
33892 @code{jit-reader-load}.
33894 @item jit-reader-unload
33895 Unload the currently loaded JIT reader.
33899 @node Writing JIT Debug Info Readers
33900 @subsection Writing JIT Debug Info Readers
33901 @cindex writing JIT debug info readers
33903 As mentioned, a reader is essentially a shared object conforming to a
33904 certain ABI. This ABI is described in @file{jit-reader.h}.
33906 @file{jit-reader.h} defines the structures, macros and functions
33907 required to write a reader. It is installed (along with
33908 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33909 the system include directory.
33911 Readers need to be released under a GPL compatible license. A reader
33912 can be declared as released under such a license by placing the macro
33913 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33915 The entry point for readers is the symbol @code{gdb_init_reader},
33916 which is expected to be a function with the prototype
33918 @findex gdb_init_reader
33920 extern struct gdb_reader_funcs *gdb_init_reader (void);
33923 @cindex @code{struct gdb_reader_funcs}
33925 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33926 functions. These functions are executed to read the debug info
33927 generated by the JIT compiler (@code{read}), to unwind stack frames
33928 (@code{unwind}) and to create canonical frame IDs
33929 (@code{get_Frame_id}). It also has a callback that is called when the
33930 reader is being unloaded (@code{destroy}). The struct looks like this
33933 struct gdb_reader_funcs
33935 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33936 int reader_version;
33938 /* For use by the reader. */
33941 gdb_read_debug_info *read;
33942 gdb_unwind_frame *unwind;
33943 gdb_get_frame_id *get_frame_id;
33944 gdb_destroy_reader *destroy;
33948 @cindex @code{struct gdb_symbol_callbacks}
33949 @cindex @code{struct gdb_unwind_callbacks}
33951 The callbacks are provided with another set of callbacks by
33952 @value{GDBN} to do their job. For @code{read}, these callbacks are
33953 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33954 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33955 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33956 files and new symbol tables inside those object files. @code{struct
33957 gdb_unwind_callbacks} has callbacks to read registers off the current
33958 frame and to write out the values of the registers in the previous
33959 frame. Both have a callback (@code{target_read}) to read bytes off the
33960 target's address space.
33962 @node In-Process Agent
33963 @chapter In-Process Agent
33964 @cindex debugging agent
33965 The traditional debugging model is conceptually low-speed, but works fine,
33966 because most bugs can be reproduced in debugging-mode execution. However,
33967 as multi-core or many-core processors are becoming mainstream, and
33968 multi-threaded programs become more and more popular, there should be more
33969 and more bugs that only manifest themselves at normal-mode execution, for
33970 example, thread races, because debugger's interference with the program's
33971 timing may conceal the bugs. On the other hand, in some applications,
33972 it is not feasible for the debugger to interrupt the program's execution
33973 long enough for the developer to learn anything helpful about its behavior.
33974 If the program's correctness depends on its real-time behavior, delays
33975 introduced by a debugger might cause the program to fail, even when the
33976 code itself is correct. It is useful to be able to observe the program's
33977 behavior without interrupting it.
33979 Therefore, traditional debugging model is too intrusive to reproduce
33980 some bugs. In order to reduce the interference with the program, we can
33981 reduce the number of operations performed by debugger. The
33982 @dfn{In-Process Agent}, a shared library, is running within the same
33983 process with inferior, and is able to perform some debugging operations
33984 itself. As a result, debugger is only involved when necessary, and
33985 performance of debugging can be improved accordingly. Note that
33986 interference with program can be reduced but can't be removed completely,
33987 because the in-process agent will still stop or slow down the program.
33989 The in-process agent can interpret and execute Agent Expressions
33990 (@pxref{Agent Expressions}) during performing debugging operations. The
33991 agent expressions can be used for different purposes, such as collecting
33992 data in tracepoints, and condition evaluation in breakpoints.
33994 @anchor{Control Agent}
33995 You can control whether the in-process agent is used as an aid for
33996 debugging with the following commands:
33999 @kindex set agent on
34001 Causes the in-process agent to perform some operations on behalf of the
34002 debugger. Just which operations requested by the user will be done
34003 by the in-process agent depends on the its capabilities. For example,
34004 if you request to evaluate breakpoint conditions in the in-process agent,
34005 and the in-process agent has such capability as well, then breakpoint
34006 conditions will be evaluated in the in-process agent.
34008 @kindex set agent off
34009 @item set agent off
34010 Disables execution of debugging operations by the in-process agent. All
34011 of the operations will be performed by @value{GDBN}.
34015 Display the current setting of execution of debugging operations by
34016 the in-process agent.
34020 * In-Process Agent Protocol::
34023 @node In-Process Agent Protocol
34024 @section In-Process Agent Protocol
34025 @cindex in-process agent protocol
34027 The in-process agent is able to communicate with both @value{GDBN} and
34028 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34029 used for communications between @value{GDBN} or GDBserver and the IPA.
34030 In general, @value{GDBN} or GDBserver sends commands
34031 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34032 in-process agent replies back with the return result of the command, or
34033 some other information. The data sent to in-process agent is composed
34034 of primitive data types, such as 4-byte or 8-byte type, and composite
34035 types, which are called objects (@pxref{IPA Protocol Objects}).
34038 * IPA Protocol Objects::
34039 * IPA Protocol Commands::
34042 @node IPA Protocol Objects
34043 @subsection IPA Protocol Objects
34044 @cindex ipa protocol objects
34046 The commands sent to and results received from agent may contain some
34047 complex data types called @dfn{objects}.
34049 The in-process agent is running on the same machine with @value{GDBN}
34050 or GDBserver, so it doesn't have to handle as much differences between
34051 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34052 However, there are still some differences of two ends in two processes:
34056 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34057 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34059 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34060 GDBserver is compiled with one, and in-process agent is compiled with
34064 Here are the IPA Protocol Objects:
34068 agent expression object. It represents an agent expression
34069 (@pxref{Agent Expressions}).
34070 @anchor{agent expression object}
34072 tracepoint action object. It represents a tracepoint action
34073 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34074 memory, static trace data and to evaluate expression.
34075 @anchor{tracepoint action object}
34077 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34078 @anchor{tracepoint object}
34082 The following table describes important attributes of each IPA protocol
34085 @multitable @columnfractions .30 .20 .50
34086 @headitem Name @tab Size @tab Description
34087 @item @emph{agent expression object} @tab @tab
34088 @item length @tab 4 @tab length of bytes code
34089 @item byte code @tab @var{length} @tab contents of byte code
34090 @item @emph{tracepoint action for collecting memory} @tab @tab
34091 @item 'M' @tab 1 @tab type of tracepoint action
34092 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34093 address of the lowest byte to collect, otherwise @var{addr} is the offset
34094 of @var{basereg} for memory collecting.
34095 @item len @tab 8 @tab length of memory for collecting
34096 @item basereg @tab 4 @tab the register number containing the starting
34097 memory address for collecting.
34098 @item @emph{tracepoint action for collecting registers} @tab @tab
34099 @item 'R' @tab 1 @tab type of tracepoint action
34100 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34101 @item 'L' @tab 1 @tab type of tracepoint action
34102 @item @emph{tracepoint action for expression evaluation} @tab @tab
34103 @item 'X' @tab 1 @tab type of tracepoint action
34104 @item agent expression @tab length of @tab @ref{agent expression object}
34105 @item @emph{tracepoint object} @tab @tab
34106 @item number @tab 4 @tab number of tracepoint
34107 @item address @tab 8 @tab address of tracepoint inserted on
34108 @item type @tab 4 @tab type of tracepoint
34109 @item enabled @tab 1 @tab enable or disable of tracepoint
34110 @item step_count @tab 8 @tab step
34111 @item pass_count @tab 8 @tab pass
34112 @item numactions @tab 4 @tab number of tracepoint actions
34113 @item hit count @tab 8 @tab hit count
34114 @item trace frame usage @tab 8 @tab trace frame usage
34115 @item compiled_cond @tab 8 @tab compiled condition
34116 @item orig_size @tab 8 @tab orig size
34117 @item condition @tab 4 if condition is NULL otherwise length of
34118 @ref{agent expression object}
34119 @tab zero if condition is NULL, otherwise is
34120 @ref{agent expression object}
34121 @item actions @tab variable
34122 @tab numactions number of @ref{tracepoint action object}
34125 @node IPA Protocol Commands
34126 @subsection IPA Protocol Commands
34127 @cindex ipa protocol commands
34129 The spaces in each command are delimiters to ease reading this commands
34130 specification. They don't exist in real commands.
34134 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34135 Installs a new fast tracepoint described by @var{tracepoint_object}
34136 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34137 head of @dfn{jumppad}, which is used to jump to data collection routine
34142 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34143 @var{target_address} is address of tracepoint in the inferior.
34144 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34145 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34146 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34147 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34154 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34155 is about to kill inferiors.
34163 @item probe_marker_at:@var{address}
34164 Asks in-process agent to probe the marker at @var{address}.
34171 @item unprobe_marker_at:@var{address}
34172 Asks in-process agent to unprobe the marker at @var{address}.
34176 @chapter Reporting Bugs in @value{GDBN}
34177 @cindex bugs in @value{GDBN}
34178 @cindex reporting bugs in @value{GDBN}
34180 Your bug reports play an essential role in making @value{GDBN} reliable.
34182 Reporting a bug may help you by bringing a solution to your problem, or it
34183 may not. But in any case the principal function of a bug report is to help
34184 the entire community by making the next version of @value{GDBN} work better. Bug
34185 reports are your contribution to the maintenance of @value{GDBN}.
34187 In order for a bug report to serve its purpose, you must include the
34188 information that enables us to fix the bug.
34191 * Bug Criteria:: Have you found a bug?
34192 * Bug Reporting:: How to report bugs
34196 @section Have You Found a Bug?
34197 @cindex bug criteria
34199 If you are not sure whether you have found a bug, here are some guidelines:
34202 @cindex fatal signal
34203 @cindex debugger crash
34204 @cindex crash of debugger
34206 If the debugger gets a fatal signal, for any input whatever, that is a
34207 @value{GDBN} bug. Reliable debuggers never crash.
34209 @cindex error on valid input
34211 If @value{GDBN} produces an error message for valid input, that is a
34212 bug. (Note that if you're cross debugging, the problem may also be
34213 somewhere in the connection to the target.)
34215 @cindex invalid input
34217 If @value{GDBN} does not produce an error message for invalid input,
34218 that is a bug. However, you should note that your idea of
34219 ``invalid input'' might be our idea of ``an extension'' or ``support
34220 for traditional practice''.
34223 If you are an experienced user of debugging tools, your suggestions
34224 for improvement of @value{GDBN} are welcome in any case.
34227 @node Bug Reporting
34228 @section How to Report Bugs
34229 @cindex bug reports
34230 @cindex @value{GDBN} bugs, reporting
34232 A number of companies and individuals offer support for @sc{gnu} products.
34233 If you obtained @value{GDBN} from a support organization, we recommend you
34234 contact that organization first.
34236 You can find contact information for many support companies and
34237 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34239 @c should add a web page ref...
34242 @ifset BUGURL_DEFAULT
34243 In any event, we also recommend that you submit bug reports for
34244 @value{GDBN}. The preferred method is to submit them directly using
34245 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34246 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34249 @strong{Do not send bug reports to @samp{info-gdb}, or to
34250 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34251 not want to receive bug reports. Those that do have arranged to receive
34254 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34255 serves as a repeater. The mailing list and the newsgroup carry exactly
34256 the same messages. Often people think of posting bug reports to the
34257 newsgroup instead of mailing them. This appears to work, but it has one
34258 problem which can be crucial: a newsgroup posting often lacks a mail
34259 path back to the sender. Thus, if we need to ask for more information,
34260 we may be unable to reach you. For this reason, it is better to send
34261 bug reports to the mailing list.
34263 @ifclear BUGURL_DEFAULT
34264 In any event, we also recommend that you submit bug reports for
34265 @value{GDBN} to @value{BUGURL}.
34269 The fundamental principle of reporting bugs usefully is this:
34270 @strong{report all the facts}. If you are not sure whether to state a
34271 fact or leave it out, state it!
34273 Often people omit facts because they think they know what causes the
34274 problem and assume that some details do not matter. Thus, you might
34275 assume that the name of the variable you use in an example does not matter.
34276 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34277 stray memory reference which happens to fetch from the location where that
34278 name is stored in memory; perhaps, if the name were different, the contents
34279 of that location would fool the debugger into doing the right thing despite
34280 the bug. Play it safe and give a specific, complete example. That is the
34281 easiest thing for you to do, and the most helpful.
34283 Keep in mind that the purpose of a bug report is to enable us to fix the
34284 bug. It may be that the bug has been reported previously, but neither
34285 you nor we can know that unless your bug report is complete and
34288 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34289 bell?'' Those bug reports are useless, and we urge everyone to
34290 @emph{refuse to respond to them} except to chide the sender to report
34293 To enable us to fix the bug, you should include all these things:
34297 The version of @value{GDBN}. @value{GDBN} announces it if you start
34298 with no arguments; you can also print it at any time using @code{show
34301 Without this, we will not know whether there is any point in looking for
34302 the bug in the current version of @value{GDBN}.
34305 The type of machine you are using, and the operating system name and
34309 The details of the @value{GDBN} build-time configuration.
34310 @value{GDBN} shows these details if you invoke it with the
34311 @option{--configuration} command-line option, or if you type
34312 @code{show configuration} at @value{GDBN}'s prompt.
34315 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34316 ``@value{GCC}--2.8.1''.
34319 What compiler (and its version) was used to compile the program you are
34320 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34321 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34322 to get this information; for other compilers, see the documentation for
34326 The command arguments you gave the compiler to compile your example and
34327 observe the bug. For example, did you use @samp{-O}? To guarantee
34328 you will not omit something important, list them all. A copy of the
34329 Makefile (or the output from make) is sufficient.
34331 If we were to try to guess the arguments, we would probably guess wrong
34332 and then we might not encounter the bug.
34335 A complete input script, and all necessary source files, that will
34339 A description of what behavior you observe that you believe is
34340 incorrect. For example, ``It gets a fatal signal.''
34342 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34343 will certainly notice it. But if the bug is incorrect output, we might
34344 not notice unless it is glaringly wrong. You might as well not give us
34345 a chance to make a mistake.
34347 Even if the problem you experience is a fatal signal, you should still
34348 say so explicitly. Suppose something strange is going on, such as, your
34349 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34350 the C library on your system. (This has happened!) Your copy might
34351 crash and ours would not. If you told us to expect a crash, then when
34352 ours fails to crash, we would know that the bug was not happening for
34353 us. If you had not told us to expect a crash, then we would not be able
34354 to draw any conclusion from our observations.
34357 @cindex recording a session script
34358 To collect all this information, you can use a session recording program
34359 such as @command{script}, which is available on many Unix systems.
34360 Just run your @value{GDBN} session inside @command{script} and then
34361 include the @file{typescript} file with your bug report.
34363 Another way to record a @value{GDBN} session is to run @value{GDBN}
34364 inside Emacs and then save the entire buffer to a file.
34367 If you wish to suggest changes to the @value{GDBN} source, send us context
34368 diffs. If you even discuss something in the @value{GDBN} source, refer to
34369 it by context, not by line number.
34371 The line numbers in our development sources will not match those in your
34372 sources. Your line numbers would convey no useful information to us.
34376 Here are some things that are not necessary:
34380 A description of the envelope of the bug.
34382 Often people who encounter a bug spend a lot of time investigating
34383 which changes to the input file will make the bug go away and which
34384 changes will not affect it.
34386 This is often time consuming and not very useful, because the way we
34387 will find the bug is by running a single example under the debugger
34388 with breakpoints, not by pure deduction from a series of examples.
34389 We recommend that you save your time for something else.
34391 Of course, if you can find a simpler example to report @emph{instead}
34392 of the original one, that is a convenience for us. Errors in the
34393 output will be easier to spot, running under the debugger will take
34394 less time, and so on.
34396 However, simplification is not vital; if you do not want to do this,
34397 report the bug anyway and send us the entire test case you used.
34400 A patch for the bug.
34402 A patch for the bug does help us if it is a good one. But do not omit
34403 the necessary information, such as the test case, on the assumption that
34404 a patch is all we need. We might see problems with your patch and decide
34405 to fix the problem another way, or we might not understand it at all.
34407 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34408 construct an example that will make the program follow a certain path
34409 through the code. If you do not send us the example, we will not be able
34410 to construct one, so we will not be able to verify that the bug is fixed.
34412 And if we cannot understand what bug you are trying to fix, or why your
34413 patch should be an improvement, we will not install it. A test case will
34414 help us to understand.
34417 A guess about what the bug is or what it depends on.
34419 Such guesses are usually wrong. Even we cannot guess right about such
34420 things without first using the debugger to find the facts.
34423 @c The readline documentation is distributed with the readline code
34424 @c and consists of the two following files:
34427 @c Use -I with makeinfo to point to the appropriate directory,
34428 @c environment var TEXINPUTS with TeX.
34429 @ifclear SYSTEM_READLINE
34430 @include rluser.texi
34431 @include hsuser.texi
34435 @appendix In Memoriam
34437 The @value{GDBN} project mourns the loss of the following long-time
34442 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34443 to Free Software in general. Outside of @value{GDBN}, he was known in
34444 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34446 @item Michael Snyder
34447 Michael was one of the Global Maintainers of the @value{GDBN} project,
34448 with contributions recorded as early as 1996, until 2011. In addition
34449 to his day to day participation, he was a large driving force behind
34450 adding Reverse Debugging to @value{GDBN}.
34453 Beyond their technical contributions to the project, they were also
34454 enjoyable members of the Free Software Community. We will miss them.
34456 @node Formatting Documentation
34457 @appendix Formatting Documentation
34459 @cindex @value{GDBN} reference card
34460 @cindex reference card
34461 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34462 for printing with PostScript or Ghostscript, in the @file{gdb}
34463 subdirectory of the main source directory@footnote{In
34464 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34465 release.}. If you can use PostScript or Ghostscript with your printer,
34466 you can print the reference card immediately with @file{refcard.ps}.
34468 The release also includes the source for the reference card. You
34469 can format it, using @TeX{}, by typing:
34475 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34476 mode on US ``letter'' size paper;
34477 that is, on a sheet 11 inches wide by 8.5 inches
34478 high. You will need to specify this form of printing as an option to
34479 your @sc{dvi} output program.
34481 @cindex documentation
34483 All the documentation for @value{GDBN} comes as part of the machine-readable
34484 distribution. The documentation is written in Texinfo format, which is
34485 a documentation system that uses a single source file to produce both
34486 on-line information and a printed manual. You can use one of the Info
34487 formatting commands to create the on-line version of the documentation
34488 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34490 @value{GDBN} includes an already formatted copy of the on-line Info
34491 version of this manual in the @file{gdb} subdirectory. The main Info
34492 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34493 subordinate files matching @samp{gdb.info*} in the same directory. If
34494 necessary, you can print out these files, or read them with any editor;
34495 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34496 Emacs or the standalone @code{info} program, available as part of the
34497 @sc{gnu} Texinfo distribution.
34499 If you want to format these Info files yourself, you need one of the
34500 Info formatting programs, such as @code{texinfo-format-buffer} or
34503 If you have @code{makeinfo} installed, and are in the top level
34504 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34505 version @value{GDBVN}), you can make the Info file by typing:
34512 If you want to typeset and print copies of this manual, you need @TeX{},
34513 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34514 Texinfo definitions file.
34516 @TeX{} is a typesetting program; it does not print files directly, but
34517 produces output files called @sc{dvi} files. To print a typeset
34518 document, you need a program to print @sc{dvi} files. If your system
34519 has @TeX{} installed, chances are it has such a program. The precise
34520 command to use depends on your system; @kbd{lpr -d} is common; another
34521 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34522 require a file name without any extension or a @samp{.dvi} extension.
34524 @TeX{} also requires a macro definitions file called
34525 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34526 written in Texinfo format. On its own, @TeX{} cannot either read or
34527 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34528 and is located in the @file{gdb-@var{version-number}/texinfo}
34531 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34532 typeset and print this manual. First switch to the @file{gdb}
34533 subdirectory of the main source directory (for example, to
34534 @file{gdb-@value{GDBVN}/gdb}) and type:
34540 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34542 @node Installing GDB
34543 @appendix Installing @value{GDBN}
34544 @cindex installation
34547 * Requirements:: Requirements for building @value{GDBN}
34548 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34549 * Separate Objdir:: Compiling @value{GDBN} in another directory
34550 * Config Names:: Specifying names for hosts and targets
34551 * Configure Options:: Summary of options for configure
34552 * System-wide configuration:: Having a system-wide init file
34556 @section Requirements for Building @value{GDBN}
34557 @cindex building @value{GDBN}, requirements for
34559 Building @value{GDBN} requires various tools and packages to be available.
34560 Other packages will be used only if they are found.
34562 @heading Tools/Packages Necessary for Building @value{GDBN}
34564 @item ISO C90 compiler
34565 @value{GDBN} is written in ISO C90. It should be buildable with any
34566 working C90 compiler, e.g.@: GCC.
34570 @heading Tools/Packages Optional for Building @value{GDBN}
34574 @value{GDBN} can use the Expat XML parsing library. This library may be
34575 included with your operating system distribution; if it is not, you
34576 can get the latest version from @url{http://expat.sourceforge.net}.
34577 The @file{configure} script will search for this library in several
34578 standard locations; if it is installed in an unusual path, you can
34579 use the @option{--with-libexpat-prefix} option to specify its location.
34585 Remote protocol memory maps (@pxref{Memory Map Format})
34587 Target descriptions (@pxref{Target Descriptions})
34589 Remote shared library lists (@xref{Library List Format},
34590 or alternatively @pxref{Library List Format for SVR4 Targets})
34592 MS-Windows shared libraries (@pxref{Shared Libraries})
34594 Traceframe info (@pxref{Traceframe Info Format})
34596 Branch trace (@pxref{Branch Trace Format},
34597 @pxref{Branch Trace Configuration Format})
34602 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34603 library. This library may be included with your operating system
34604 distribution; if it is not, you can get the latest version from
34605 @url{http://www.mpfr.org}. The @file{configure} script will search
34606 for this library in several standard locations; if it is installed
34607 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34608 option to specify its location.
34610 GNU MPFR is used to emulate target floating-point arithmetic during
34611 expression evaluation when the target uses different floating-point
34612 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34613 will fall back to using host floating-point arithmetic.
34616 @cindex compressed debug sections
34617 @value{GDBN} will use the @samp{zlib} library, if available, to read
34618 compressed debug sections. Some linkers, such as GNU gold, are capable
34619 of producing binaries with compressed debug sections. If @value{GDBN}
34620 is compiled with @samp{zlib}, it will be able to read the debug
34621 information in such binaries.
34623 The @samp{zlib} library is likely included with your operating system
34624 distribution; if it is not, you can get the latest version from
34625 @url{http://zlib.net}.
34628 @value{GDBN}'s features related to character sets (@pxref{Character
34629 Sets}) require a functioning @code{iconv} implementation. If you are
34630 on a GNU system, then this is provided by the GNU C Library. Some
34631 other systems also provide a working @code{iconv}.
34633 If @value{GDBN} is using the @code{iconv} program which is installed
34634 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34635 This is done with @option{--with-iconv-bin} which specifies the
34636 directory that contains the @code{iconv} program.
34638 On systems without @code{iconv}, you can install GNU Libiconv. If you
34639 have previously installed Libiconv, you can use the
34640 @option{--with-libiconv-prefix} option to configure.
34642 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34643 arrange to build Libiconv if a directory named @file{libiconv} appears
34644 in the top-most source directory. If Libiconv is built this way, and
34645 if the operating system does not provide a suitable @code{iconv}
34646 implementation, then the just-built library will automatically be used
34647 by @value{GDBN}. One easy way to set this up is to download GNU
34648 Libiconv, unpack it, and then rename the directory holding the
34649 Libiconv source code to @samp{libiconv}.
34652 @node Running Configure
34653 @section Invoking the @value{GDBN} @file{configure} Script
34654 @cindex configuring @value{GDBN}
34655 @value{GDBN} comes with a @file{configure} script that automates the process
34656 of preparing @value{GDBN} for installation; you can then use @code{make} to
34657 build the @code{gdb} program.
34659 @c irrelevant in info file; it's as current as the code it lives with.
34660 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34661 look at the @file{README} file in the sources; we may have improved the
34662 installation procedures since publishing this manual.}
34665 The @value{GDBN} distribution includes all the source code you need for
34666 @value{GDBN} in a single directory, whose name is usually composed by
34667 appending the version number to @samp{gdb}.
34669 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34670 @file{gdb-@value{GDBVN}} directory. That directory contains:
34673 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34674 script for configuring @value{GDBN} and all its supporting libraries
34676 @item gdb-@value{GDBVN}/gdb
34677 the source specific to @value{GDBN} itself
34679 @item gdb-@value{GDBVN}/bfd
34680 source for the Binary File Descriptor library
34682 @item gdb-@value{GDBVN}/include
34683 @sc{gnu} include files
34685 @item gdb-@value{GDBVN}/libiberty
34686 source for the @samp{-liberty} free software library
34688 @item gdb-@value{GDBVN}/opcodes
34689 source for the library of opcode tables and disassemblers
34691 @item gdb-@value{GDBVN}/readline
34692 source for the @sc{gnu} command-line interface
34694 @item gdb-@value{GDBVN}/glob
34695 source for the @sc{gnu} filename pattern-matching subroutine
34697 @item gdb-@value{GDBVN}/mmalloc
34698 source for the @sc{gnu} memory-mapped malloc package
34701 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34702 from the @file{gdb-@var{version-number}} source directory, which in
34703 this example is the @file{gdb-@value{GDBVN}} directory.
34705 First switch to the @file{gdb-@var{version-number}} source directory
34706 if you are not already in it; then run @file{configure}. Pass the
34707 identifier for the platform on which @value{GDBN} will run as an
34713 cd gdb-@value{GDBVN}
34714 ./configure @var{host}
34719 where @var{host} is an identifier such as @samp{sun4} or
34720 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34721 (You can often leave off @var{host}; @file{configure} tries to guess the
34722 correct value by examining your system.)
34724 Running @samp{configure @var{host}} and then running @code{make} builds the
34725 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34726 libraries, then @code{gdb} itself. The configured source files, and the
34727 binaries, are left in the corresponding source directories.
34730 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34731 system does not recognize this automatically when you run a different
34732 shell, you may need to run @code{sh} on it explicitly:
34735 sh configure @var{host}
34738 If you run @file{configure} from a directory that contains source
34739 directories for multiple libraries or programs, such as the
34740 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34742 creates configuration files for every directory level underneath (unless
34743 you tell it not to, with the @samp{--norecursion} option).
34745 You should run the @file{configure} script from the top directory in the
34746 source tree, the @file{gdb-@var{version-number}} directory. If you run
34747 @file{configure} from one of the subdirectories, you will configure only
34748 that subdirectory. That is usually not what you want. In particular,
34749 if you run the first @file{configure} from the @file{gdb} subdirectory
34750 of the @file{gdb-@var{version-number}} directory, you will omit the
34751 configuration of @file{bfd}, @file{readline}, and other sibling
34752 directories of the @file{gdb} subdirectory. This leads to build errors
34753 about missing include files such as @file{bfd/bfd.h}.
34755 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34756 However, you should make sure that the shell on your path (named by
34757 the @samp{SHELL} environment variable) is publicly readable. Remember
34758 that @value{GDBN} uses the shell to start your program---some systems refuse to
34759 let @value{GDBN} debug child processes whose programs are not readable.
34761 @node Separate Objdir
34762 @section Compiling @value{GDBN} in Another Directory
34764 If you want to run @value{GDBN} versions for several host or target machines,
34765 you need a different @code{gdb} compiled for each combination of
34766 host and target. @file{configure} is designed to make this easy by
34767 allowing you to generate each configuration in a separate subdirectory,
34768 rather than in the source directory. If your @code{make} program
34769 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34770 @code{make} in each of these directories builds the @code{gdb}
34771 program specified there.
34773 To build @code{gdb} in a separate directory, run @file{configure}
34774 with the @samp{--srcdir} option to specify where to find the source.
34775 (You also need to specify a path to find @file{configure}
34776 itself from your working directory. If the path to @file{configure}
34777 would be the same as the argument to @samp{--srcdir}, you can leave out
34778 the @samp{--srcdir} option; it is assumed.)
34780 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34781 separate directory for a Sun 4 like this:
34785 cd gdb-@value{GDBVN}
34788 ../gdb-@value{GDBVN}/configure sun4
34793 When @file{configure} builds a configuration using a remote source
34794 directory, it creates a tree for the binaries with the same structure
34795 (and using the same names) as the tree under the source directory. In
34796 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34797 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34798 @file{gdb-sun4/gdb}.
34800 Make sure that your path to the @file{configure} script has just one
34801 instance of @file{gdb} in it. If your path to @file{configure} looks
34802 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34803 one subdirectory of @value{GDBN}, not the whole package. This leads to
34804 build errors about missing include files such as @file{bfd/bfd.h}.
34806 One popular reason to build several @value{GDBN} configurations in separate
34807 directories is to configure @value{GDBN} for cross-compiling (where
34808 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34809 programs that run on another machine---the @dfn{target}).
34810 You specify a cross-debugging target by
34811 giving the @samp{--target=@var{target}} option to @file{configure}.
34813 When you run @code{make} to build a program or library, you must run
34814 it in a configured directory---whatever directory you were in when you
34815 called @file{configure} (or one of its subdirectories).
34817 The @code{Makefile} that @file{configure} generates in each source
34818 directory also runs recursively. If you type @code{make} in a source
34819 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34820 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34821 will build all the required libraries, and then build GDB.
34823 When you have multiple hosts or targets configured in separate
34824 directories, you can run @code{make} on them in parallel (for example,
34825 if they are NFS-mounted on each of the hosts); they will not interfere
34829 @section Specifying Names for Hosts and Targets
34831 The specifications used for hosts and targets in the @file{configure}
34832 script are based on a three-part naming scheme, but some short predefined
34833 aliases are also supported. The full naming scheme encodes three pieces
34834 of information in the following pattern:
34837 @var{architecture}-@var{vendor}-@var{os}
34840 For example, you can use the alias @code{sun4} as a @var{host} argument,
34841 or as the value for @var{target} in a @code{--target=@var{target}}
34842 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34844 The @file{configure} script accompanying @value{GDBN} does not provide
34845 any query facility to list all supported host and target names or
34846 aliases. @file{configure} calls the Bourne shell script
34847 @code{config.sub} to map abbreviations to full names; you can read the
34848 script, if you wish, or you can use it to test your guesses on
34849 abbreviations---for example:
34852 % sh config.sub i386-linux
34854 % sh config.sub alpha-linux
34855 alpha-unknown-linux-gnu
34856 % sh config.sub hp9k700
34858 % sh config.sub sun4
34859 sparc-sun-sunos4.1.1
34860 % sh config.sub sun3
34861 m68k-sun-sunos4.1.1
34862 % sh config.sub i986v
34863 Invalid configuration `i986v': machine `i986v' not recognized
34867 @code{config.sub} is also distributed in the @value{GDBN} source
34868 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34870 @node Configure Options
34871 @section @file{configure} Options
34873 Here is a summary of the @file{configure} options and arguments that
34874 are most often useful for building @value{GDBN}. @file{configure} also has
34875 several other options not listed here. @inforef{What Configure
34876 Does,,configure.info}, for a full explanation of @file{configure}.
34879 configure @r{[}--help@r{]}
34880 @r{[}--prefix=@var{dir}@r{]}
34881 @r{[}--exec-prefix=@var{dir}@r{]}
34882 @r{[}--srcdir=@var{dirname}@r{]}
34883 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34884 @r{[}--target=@var{target}@r{]}
34889 You may introduce options with a single @samp{-} rather than
34890 @samp{--} if you prefer; but you may abbreviate option names if you use
34895 Display a quick summary of how to invoke @file{configure}.
34897 @item --prefix=@var{dir}
34898 Configure the source to install programs and files under directory
34901 @item --exec-prefix=@var{dir}
34902 Configure the source to install programs under directory
34905 @c avoid splitting the warning from the explanation:
34907 @item --srcdir=@var{dirname}
34908 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34909 @code{make} that implements the @code{VPATH} feature.}@*
34910 Use this option to make configurations in directories separate from the
34911 @value{GDBN} source directories. Among other things, you can use this to
34912 build (or maintain) several configurations simultaneously, in separate
34913 directories. @file{configure} writes configuration-specific files in
34914 the current directory, but arranges for them to use the source in the
34915 directory @var{dirname}. @file{configure} creates directories under
34916 the working directory in parallel to the source directories below
34919 @item --norecursion
34920 Configure only the directory level where @file{configure} is executed; do not
34921 propagate configuration to subdirectories.
34923 @item --target=@var{target}
34924 Configure @value{GDBN} for cross-debugging programs running on the specified
34925 @var{target}. Without this option, @value{GDBN} is configured to debug
34926 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34928 There is no convenient way to generate a list of all available targets.
34930 @item @var{host} @dots{}
34931 Configure @value{GDBN} to run on the specified @var{host}.
34933 There is no convenient way to generate a list of all available hosts.
34936 There are many other options available as well, but they are generally
34937 needed for special purposes only.
34939 @node System-wide configuration
34940 @section System-wide configuration and settings
34941 @cindex system-wide init file
34943 @value{GDBN} can be configured to have a system-wide init file;
34944 this file will be read and executed at startup (@pxref{Startup, , What
34945 @value{GDBN} does during startup}).
34947 Here is the corresponding configure option:
34950 @item --with-system-gdbinit=@var{file}
34951 Specify that the default location of the system-wide init file is
34955 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34956 it may be subject to relocation. Two possible cases:
34960 If the default location of this init file contains @file{$prefix},
34961 it will be subject to relocation. Suppose that the configure options
34962 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34963 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34964 init file is looked for as @file{$install/etc/gdbinit} instead of
34965 @file{$prefix/etc/gdbinit}.
34968 By contrast, if the default location does not contain the prefix,
34969 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34970 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34971 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34972 wherever @value{GDBN} is installed.
34975 If the configured location of the system-wide init file (as given by the
34976 @option{--with-system-gdbinit} option at configure time) is in the
34977 data-directory (as specified by @option{--with-gdb-datadir} at configure
34978 time) or in one of its subdirectories, then @value{GDBN} will look for the
34979 system-wide init file in the directory specified by the
34980 @option{--data-directory} command-line option.
34981 Note that the system-wide init file is only read once, during @value{GDBN}
34982 initialization. If the data-directory is changed after @value{GDBN} has
34983 started with the @code{set data-directory} command, the file will not be
34987 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34990 @node System-wide Configuration Scripts
34991 @subsection Installed System-wide Configuration Scripts
34992 @cindex system-wide configuration scripts
34994 The @file{system-gdbinit} directory, located inside the data-directory
34995 (as specified by @option{--with-gdb-datadir} at configure time) contains
34996 a number of scripts which can be used as system-wide init files. To
34997 automatically source those scripts at startup, @value{GDBN} should be
34998 configured with @option{--with-system-gdbinit}. Otherwise, any user
34999 should be able to source them by hand as needed.
35001 The following scripts are currently available:
35004 @item @file{elinos.py}
35006 @cindex ELinOS system-wide configuration script
35007 This script is useful when debugging a program on an ELinOS target.
35008 It takes advantage of the environment variables defined in a standard
35009 ELinOS environment in order to determine the location of the system
35010 shared libraries, and then sets the @samp{solib-absolute-prefix}
35011 and @samp{solib-search-path} variables appropriately.
35013 @item @file{wrs-linux.py}
35014 @pindex wrs-linux.py
35015 @cindex Wind River Linux system-wide configuration script
35016 This script is useful when debugging a program on a target running
35017 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35018 the host-side sysroot used by the target system.
35022 @node Maintenance Commands
35023 @appendix Maintenance Commands
35024 @cindex maintenance commands
35025 @cindex internal commands
35027 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35028 includes a number of commands intended for @value{GDBN} developers,
35029 that are not documented elsewhere in this manual. These commands are
35030 provided here for reference. (For commands that turn on debugging
35031 messages, see @ref{Debugging Output}.)
35034 @kindex maint agent
35035 @kindex maint agent-eval
35036 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35037 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35038 Translate the given @var{expression} into remote agent bytecodes.
35039 This command is useful for debugging the Agent Expression mechanism
35040 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35041 expression useful for data collection, such as by tracepoints, while
35042 @samp{maint agent-eval} produces an expression that evaluates directly
35043 to a result. For instance, a collection expression for @code{globa +
35044 globb} will include bytecodes to record four bytes of memory at each
35045 of the addresses of @code{globa} and @code{globb}, while discarding
35046 the result of the addition, while an evaluation expression will do the
35047 addition and return the sum.
35048 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35049 If not, generate remote agent bytecode for current frame PC address.
35051 @kindex maint agent-printf
35052 @item maint agent-printf @var{format},@var{expr},...
35053 Translate the given format string and list of argument expressions
35054 into remote agent bytecodes and display them as a disassembled list.
35055 This command is useful for debugging the agent version of dynamic
35056 printf (@pxref{Dynamic Printf}).
35058 @kindex maint info breakpoints
35059 @item @anchor{maint info breakpoints}maint info breakpoints
35060 Using the same format as @samp{info breakpoints}, display both the
35061 breakpoints you've set explicitly, and those @value{GDBN} is using for
35062 internal purposes. Internal breakpoints are shown with negative
35063 breakpoint numbers. The type column identifies what kind of breakpoint
35068 Normal, explicitly set breakpoint.
35071 Normal, explicitly set watchpoint.
35074 Internal breakpoint, used to handle correctly stepping through
35075 @code{longjmp} calls.
35077 @item longjmp resume
35078 Internal breakpoint at the target of a @code{longjmp}.
35081 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35084 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35087 Shared library events.
35091 @kindex maint info btrace
35092 @item maint info btrace
35093 Pint information about raw branch tracing data.
35095 @kindex maint btrace packet-history
35096 @item maint btrace packet-history
35097 Print the raw branch trace packets that are used to compute the
35098 execution history for the @samp{record btrace} command. Both the
35099 information and the format in which it is printed depend on the btrace
35104 For the BTS recording format, print a list of blocks of sequential
35105 code. For each block, the following information is printed:
35109 Newer blocks have higher numbers. The oldest block has number zero.
35110 @item Lowest @samp{PC}
35111 @item Highest @samp{PC}
35115 For the Intel Processor Trace recording format, print a list of
35116 Intel Processor Trace packets. For each packet, the following
35117 information is printed:
35120 @item Packet number
35121 Newer packets have higher numbers. The oldest packet has number zero.
35123 The packet's offset in the trace stream.
35124 @item Packet opcode and payload
35128 @kindex maint btrace clear-packet-history
35129 @item maint btrace clear-packet-history
35130 Discards the cached packet history printed by the @samp{maint btrace
35131 packet-history} command. The history will be computed again when
35134 @kindex maint btrace clear
35135 @item maint btrace clear
35136 Discard the branch trace data. The data will be fetched anew and the
35137 branch trace will be recomputed when needed.
35139 This implicitly truncates the branch trace to a single branch trace
35140 buffer. When updating branch trace incrementally, the branch trace
35141 available to @value{GDBN} may be bigger than a single branch trace
35144 @kindex maint set btrace pt skip-pad
35145 @item maint set btrace pt skip-pad
35146 @kindex maint show btrace pt skip-pad
35147 @item maint show btrace pt skip-pad
35148 Control whether @value{GDBN} will skip PAD packets when computing the
35151 @kindex set displaced-stepping
35152 @kindex show displaced-stepping
35153 @cindex displaced stepping support
35154 @cindex out-of-line single-stepping
35155 @item set displaced-stepping
35156 @itemx show displaced-stepping
35157 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35158 if the target supports it. Displaced stepping is a way to single-step
35159 over breakpoints without removing them from the inferior, by executing
35160 an out-of-line copy of the instruction that was originally at the
35161 breakpoint location. It is also known as out-of-line single-stepping.
35164 @item set displaced-stepping on
35165 If the target architecture supports it, @value{GDBN} will use
35166 displaced stepping to step over breakpoints.
35168 @item set displaced-stepping off
35169 @value{GDBN} will not use displaced stepping to step over breakpoints,
35170 even if such is supported by the target architecture.
35172 @cindex non-stop mode, and @samp{set displaced-stepping}
35173 @item set displaced-stepping auto
35174 This is the default mode. @value{GDBN} will use displaced stepping
35175 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35176 architecture supports displaced stepping.
35179 @kindex maint check-psymtabs
35180 @item maint check-psymtabs
35181 Check the consistency of currently expanded psymtabs versus symtabs.
35182 Use this to check, for example, whether a symbol is in one but not the other.
35184 @kindex maint check-symtabs
35185 @item maint check-symtabs
35186 Check the consistency of currently expanded symtabs.
35188 @kindex maint expand-symtabs
35189 @item maint expand-symtabs [@var{regexp}]
35190 Expand symbol tables.
35191 If @var{regexp} is specified, only expand symbol tables for file
35192 names matching @var{regexp}.
35194 @kindex maint set catch-demangler-crashes
35195 @kindex maint show catch-demangler-crashes
35196 @cindex demangler crashes
35197 @item maint set catch-demangler-crashes [on|off]
35198 @itemx maint show catch-demangler-crashes
35199 Control whether @value{GDBN} should attempt to catch crashes in the
35200 symbol name demangler. The default is to attempt to catch crashes.
35201 If enabled, the first time a crash is caught, a core file is created,
35202 the offending symbol is displayed and the user is presented with the
35203 option to terminate the current session.
35205 @kindex maint cplus first_component
35206 @item maint cplus first_component @var{name}
35207 Print the first C@t{++} class/namespace component of @var{name}.
35209 @kindex maint cplus namespace
35210 @item maint cplus namespace
35211 Print the list of possible C@t{++} namespaces.
35213 @kindex maint deprecate
35214 @kindex maint undeprecate
35215 @cindex deprecated commands
35216 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35217 @itemx maint undeprecate @var{command}
35218 Deprecate or undeprecate the named @var{command}. Deprecated commands
35219 cause @value{GDBN} to issue a warning when you use them. The optional
35220 argument @var{replacement} says which newer command should be used in
35221 favor of the deprecated one; if it is given, @value{GDBN} will mention
35222 the replacement as part of the warning.
35224 @kindex maint dump-me
35225 @item maint dump-me
35226 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35227 Cause a fatal signal in the debugger and force it to dump its core.
35228 This is supported only on systems which support aborting a program
35229 with the @code{SIGQUIT} signal.
35231 @kindex maint internal-error
35232 @kindex maint internal-warning
35233 @kindex maint demangler-warning
35234 @cindex demangler crashes
35235 @item maint internal-error @r{[}@var{message-text}@r{]}
35236 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35237 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35239 Cause @value{GDBN} to call the internal function @code{internal_error},
35240 @code{internal_warning} or @code{demangler_warning} and hence behave
35241 as though an internal problem has been detected. In addition to
35242 reporting the internal problem, these functions give the user the
35243 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35244 and @code{internal_warning}) create a core file of the current
35245 @value{GDBN} session.
35247 These commands take an optional parameter @var{message-text} that is
35248 used as the text of the error or warning message.
35250 Here's an example of using @code{internal-error}:
35253 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35254 @dots{}/maint.c:121: internal-error: testing, 1, 2
35255 A problem internal to GDB has been detected. Further
35256 debugging may prove unreliable.
35257 Quit this debugging session? (y or n) @kbd{n}
35258 Create a core file? (y or n) @kbd{n}
35262 @cindex @value{GDBN} internal error
35263 @cindex internal errors, control of @value{GDBN} behavior
35264 @cindex demangler crashes
35266 @kindex maint set internal-error
35267 @kindex maint show internal-error
35268 @kindex maint set internal-warning
35269 @kindex maint show internal-warning
35270 @kindex maint set demangler-warning
35271 @kindex maint show demangler-warning
35272 @item maint set internal-error @var{action} [ask|yes|no]
35273 @itemx maint show internal-error @var{action}
35274 @itemx maint set internal-warning @var{action} [ask|yes|no]
35275 @itemx maint show internal-warning @var{action}
35276 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35277 @itemx maint show demangler-warning @var{action}
35278 When @value{GDBN} reports an internal problem (error or warning) it
35279 gives the user the opportunity to both quit @value{GDBN} and create a
35280 core file of the current @value{GDBN} session. These commands let you
35281 override the default behaviour for each particular @var{action},
35282 described in the table below.
35286 You can specify that @value{GDBN} should always (yes) or never (no)
35287 quit. The default is to ask the user what to do.
35290 You can specify that @value{GDBN} should always (yes) or never (no)
35291 create a core file. The default is to ask the user what to do. Note
35292 that there is no @code{corefile} option for @code{demangler-warning}:
35293 demangler warnings always create a core file and this cannot be
35297 @kindex maint packet
35298 @item maint packet @var{text}
35299 If @value{GDBN} is talking to an inferior via the serial protocol,
35300 then this command sends the string @var{text} to the inferior, and
35301 displays the response packet. @value{GDBN} supplies the initial
35302 @samp{$} character, the terminating @samp{#} character, and the
35305 @kindex maint print architecture
35306 @item maint print architecture @r{[}@var{file}@r{]}
35307 Print the entire architecture configuration. The optional argument
35308 @var{file} names the file where the output goes.
35310 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35311 @item maint print c-tdesc
35312 Print the target description (@pxref{Target Descriptions}) as
35313 a C source file. By default, the target description is for the current
35314 target, but if the optional argument @var{file} is provided, that file
35315 is used to produce the description. The @var{file} should be an XML
35316 document, of the form described in @ref{Target Description Format}.
35317 The created source file is built into @value{GDBN} when @value{GDBN} is
35318 built again. This command is used by developers after they add or
35319 modify XML target descriptions.
35321 @kindex maint check xml-descriptions
35322 @item maint check xml-descriptions @var{dir}
35323 Check that the target descriptions dynamically created by @value{GDBN}
35324 equal the descriptions created from XML files found in @var{dir}.
35326 @kindex maint print dummy-frames
35327 @item maint print dummy-frames
35328 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35331 (@value{GDBP}) @kbd{b add}
35333 (@value{GDBP}) @kbd{print add(2,3)}
35334 Breakpoint 2, add (a=2, b=3) at @dots{}
35336 The program being debugged stopped while in a function called from GDB.
35338 (@value{GDBP}) @kbd{maint print dummy-frames}
35339 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35343 Takes an optional file parameter.
35345 @kindex maint print registers
35346 @kindex maint print raw-registers
35347 @kindex maint print cooked-registers
35348 @kindex maint print register-groups
35349 @kindex maint print remote-registers
35350 @item maint print registers @r{[}@var{file}@r{]}
35351 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35352 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35353 @itemx maint print register-groups @r{[}@var{file}@r{]}
35354 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35355 Print @value{GDBN}'s internal register data structures.
35357 The command @code{maint print raw-registers} includes the contents of
35358 the raw register cache; the command @code{maint print
35359 cooked-registers} includes the (cooked) value of all registers,
35360 including registers which aren't available on the target nor visible
35361 to user; the command @code{maint print register-groups} includes the
35362 groups that each register is a member of; and the command @code{maint
35363 print remote-registers} includes the remote target's register numbers
35364 and offsets in the `G' packets.
35366 These commands take an optional parameter, a file name to which to
35367 write the information.
35369 @kindex maint print reggroups
35370 @item maint print reggroups @r{[}@var{file}@r{]}
35371 Print @value{GDBN}'s internal register group data structures. The
35372 optional argument @var{file} tells to what file to write the
35375 The register groups info looks like this:
35378 (@value{GDBP}) @kbd{maint print reggroups}
35391 This command forces @value{GDBN} to flush its internal register cache.
35393 @kindex maint print objfiles
35394 @cindex info for known object files
35395 @item maint print objfiles @r{[}@var{regexp}@r{]}
35396 Print a dump of all known object files.
35397 If @var{regexp} is specified, only print object files whose names
35398 match @var{regexp}. For each object file, this command prints its name,
35399 address in memory, and all of its psymtabs and symtabs.
35401 @kindex maint print user-registers
35402 @cindex user registers
35403 @item maint print user-registers
35404 List all currently available @dfn{user registers}. User registers
35405 typically provide alternate names for actual hardware registers. They
35406 include the four ``standard'' registers @code{$fp}, @code{$pc},
35407 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35408 registers can be used in expressions in the same way as the canonical
35409 register names, but only the latter are listed by the @code{info
35410 registers} and @code{maint print registers} commands.
35412 @kindex maint print section-scripts
35413 @cindex info for known .debug_gdb_scripts-loaded scripts
35414 @item maint print section-scripts [@var{regexp}]
35415 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35416 If @var{regexp} is specified, only print scripts loaded by object files
35417 matching @var{regexp}.
35418 For each script, this command prints its name as specified in the objfile,
35419 and the full path if known.
35420 @xref{dotdebug_gdb_scripts section}.
35422 @kindex maint print statistics
35423 @cindex bcache statistics
35424 @item maint print statistics
35425 This command prints, for each object file in the program, various data
35426 about that object file followed by the byte cache (@dfn{bcache})
35427 statistics for the object file. The objfile data includes the number
35428 of minimal, partial, full, and stabs symbols, the number of types
35429 defined by the objfile, the number of as yet unexpanded psym tables,
35430 the number of line tables and string tables, and the amount of memory
35431 used by the various tables. The bcache statistics include the counts,
35432 sizes, and counts of duplicates of all and unique objects, max,
35433 average, and median entry size, total memory used and its overhead and
35434 savings, and various measures of the hash table size and chain
35437 @kindex maint print target-stack
35438 @cindex target stack description
35439 @item maint print target-stack
35440 A @dfn{target} is an interface between the debugger and a particular
35441 kind of file or process. Targets can be stacked in @dfn{strata},
35442 so that more than one target can potentially respond to a request.
35443 In particular, memory accesses will walk down the stack of targets
35444 until they find a target that is interested in handling that particular
35447 This command prints a short description of each layer that was pushed on
35448 the @dfn{target stack}, starting from the top layer down to the bottom one.
35450 @kindex maint print type
35451 @cindex type chain of a data type
35452 @item maint print type @var{expr}
35453 Print the type chain for a type specified by @var{expr}. The argument
35454 can be either a type name or a symbol. If it is a symbol, the type of
35455 that symbol is described. The type chain produced by this command is
35456 a recursive definition of the data type as stored in @value{GDBN}'s
35457 data structures, including its flags and contained types.
35459 @kindex maint selftest
35461 @item maint selftest @r{[}@var{filter}@r{]}
35462 Run any self tests that were compiled in to @value{GDBN}. This will
35463 print a message showing how many tests were run, and how many failed.
35464 If a @var{filter} is passed, only the tests with @var{filter} in their
35467 @kindex "maint info selftests"
35469 @item maint info selftests
35470 List the selftests compiled in to @value{GDBN}.
35472 @kindex maint set dwarf always-disassemble
35473 @kindex maint show dwarf always-disassemble
35474 @item maint set dwarf always-disassemble
35475 @item maint show dwarf always-disassemble
35476 Control the behavior of @code{info address} when using DWARF debugging
35479 The default is @code{off}, which means that @value{GDBN} should try to
35480 describe a variable's location in an easily readable format. When
35481 @code{on}, @value{GDBN} will instead display the DWARF location
35482 expression in an assembly-like format. Note that some locations are
35483 too complex for @value{GDBN} to describe simply; in this case you will
35484 always see the disassembly form.
35486 Here is an example of the resulting disassembly:
35489 (gdb) info addr argc
35490 Symbol "argc" is a complex DWARF expression:
35494 For more information on these expressions, see
35495 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35497 @kindex maint set dwarf max-cache-age
35498 @kindex maint show dwarf max-cache-age
35499 @item maint set dwarf max-cache-age
35500 @itemx maint show dwarf max-cache-age
35501 Control the DWARF compilation unit cache.
35503 @cindex DWARF compilation units cache
35504 In object files with inter-compilation-unit references, such as those
35505 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35506 reader needs to frequently refer to previously read compilation units.
35507 This setting controls how long a compilation unit will remain in the
35508 cache if it is not referenced. A higher limit means that cached
35509 compilation units will be stored in memory longer, and more total
35510 memory will be used. Setting it to zero disables caching, which will
35511 slow down @value{GDBN} startup, but reduce memory consumption.
35513 @kindex maint set profile
35514 @kindex maint show profile
35515 @cindex profiling GDB
35516 @item maint set profile
35517 @itemx maint show profile
35518 Control profiling of @value{GDBN}.
35520 Profiling will be disabled until you use the @samp{maint set profile}
35521 command to enable it. When you enable profiling, the system will begin
35522 collecting timing and execution count data; when you disable profiling or
35523 exit @value{GDBN}, the results will be written to a log file. Remember that
35524 if you use profiling, @value{GDBN} will overwrite the profiling log file
35525 (often called @file{gmon.out}). If you have a record of important profiling
35526 data in a @file{gmon.out} file, be sure to move it to a safe location.
35528 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35529 compiled with the @samp{-pg} compiler option.
35531 @kindex maint set show-debug-regs
35532 @kindex maint show show-debug-regs
35533 @cindex hardware debug registers
35534 @item maint set show-debug-regs
35535 @itemx maint show show-debug-regs
35536 Control whether to show variables that mirror the hardware debug
35537 registers. Use @code{on} to enable, @code{off} to disable. If
35538 enabled, the debug registers values are shown when @value{GDBN} inserts or
35539 removes a hardware breakpoint or watchpoint, and when the inferior
35540 triggers a hardware-assisted breakpoint or watchpoint.
35542 @kindex maint set show-all-tib
35543 @kindex maint show show-all-tib
35544 @item maint set show-all-tib
35545 @itemx maint show show-all-tib
35546 Control whether to show all non zero areas within a 1k block starting
35547 at thread local base, when using the @samp{info w32 thread-information-block}
35550 @kindex maint set target-async
35551 @kindex maint show target-async
35552 @item maint set target-async
35553 @itemx maint show target-async
35554 This controls whether @value{GDBN} targets operate in synchronous or
35555 asynchronous mode (@pxref{Background Execution}). Normally the
35556 default is asynchronous, if it is available; but this can be changed
35557 to more easily debug problems occurring only in synchronous mode.
35559 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35560 @kindex maint show target-non-stop
35561 @item maint set target-non-stop
35562 @itemx maint show target-non-stop
35564 This controls whether @value{GDBN} targets always operate in non-stop
35565 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35566 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35567 if supported by the target.
35570 @item maint set target-non-stop auto
35571 This is the default mode. @value{GDBN} controls the target in
35572 non-stop mode if the target supports it.
35574 @item maint set target-non-stop on
35575 @value{GDBN} controls the target in non-stop mode even if the target
35576 does not indicate support.
35578 @item maint set target-non-stop off
35579 @value{GDBN} does not control the target in non-stop mode even if the
35580 target supports it.
35583 @kindex maint set per-command
35584 @kindex maint show per-command
35585 @item maint set per-command
35586 @itemx maint show per-command
35587 @cindex resources used by commands
35589 @value{GDBN} can display the resources used by each command.
35590 This is useful in debugging performance problems.
35593 @item maint set per-command space [on|off]
35594 @itemx maint show per-command space
35595 Enable or disable the printing of the memory used by GDB for each command.
35596 If enabled, @value{GDBN} will display how much memory each command
35597 took, following the command's own output.
35598 This can also be requested by invoking @value{GDBN} with the
35599 @option{--statistics} command-line switch (@pxref{Mode Options}).
35601 @item maint set per-command time [on|off]
35602 @itemx maint show per-command time
35603 Enable or disable the printing of the execution time of @value{GDBN}
35605 If enabled, @value{GDBN} will display how much time it
35606 took to execute each command, following the command's own output.
35607 Both CPU time and wallclock time are printed.
35608 Printing both is useful when trying to determine whether the cost is
35609 CPU or, e.g., disk/network latency.
35610 Note that the CPU time printed is for @value{GDBN} only, it does not include
35611 the execution time of the inferior because there's no mechanism currently
35612 to compute how much time was spent by @value{GDBN} and how much time was
35613 spent by the program been debugged.
35614 This can also be requested by invoking @value{GDBN} with the
35615 @option{--statistics} command-line switch (@pxref{Mode Options}).
35617 @item maint set per-command symtab [on|off]
35618 @itemx maint show per-command symtab
35619 Enable or disable the printing of basic symbol table statistics
35621 If enabled, @value{GDBN} will display the following information:
35625 number of symbol tables
35627 number of primary symbol tables
35629 number of blocks in the blockvector
35633 @kindex maint space
35634 @cindex memory used by commands
35635 @item maint space @var{value}
35636 An alias for @code{maint set per-command space}.
35637 A non-zero value enables it, zero disables it.
35640 @cindex time of command execution
35641 @item maint time @var{value}
35642 An alias for @code{maint set per-command time}.
35643 A non-zero value enables it, zero disables it.
35645 @kindex maint translate-address
35646 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35647 Find the symbol stored at the location specified by the address
35648 @var{addr} and an optional section name @var{section}. If found,
35649 @value{GDBN} prints the name of the closest symbol and an offset from
35650 the symbol's location to the specified address. This is similar to
35651 the @code{info address} command (@pxref{Symbols}), except that this
35652 command also allows to find symbols in other sections.
35654 If section was not specified, the section in which the symbol was found
35655 is also printed. For dynamically linked executables, the name of
35656 executable or shared library containing the symbol is printed as well.
35660 The following command is useful for non-interactive invocations of
35661 @value{GDBN}, such as in the test suite.
35664 @item set watchdog @var{nsec}
35665 @kindex set watchdog
35666 @cindex watchdog timer
35667 @cindex timeout for commands
35668 Set the maximum number of seconds @value{GDBN} will wait for the
35669 target operation to finish. If this time expires, @value{GDBN}
35670 reports and error and the command is aborted.
35672 @item show watchdog
35673 Show the current setting of the target wait timeout.
35676 @node Remote Protocol
35677 @appendix @value{GDBN} Remote Serial Protocol
35682 * Stop Reply Packets::
35683 * General Query Packets::
35684 * Architecture-Specific Protocol Details::
35685 * Tracepoint Packets::
35686 * Host I/O Packets::
35688 * Notification Packets::
35689 * Remote Non-Stop::
35690 * Packet Acknowledgment::
35692 * File-I/O Remote Protocol Extension::
35693 * Library List Format::
35694 * Library List Format for SVR4 Targets::
35695 * Memory Map Format::
35696 * Thread List Format::
35697 * Traceframe Info Format::
35698 * Branch Trace Format::
35699 * Branch Trace Configuration Format::
35705 There may be occasions when you need to know something about the
35706 protocol---for example, if there is only one serial port to your target
35707 machine, you might want your program to do something special if it
35708 recognizes a packet meant for @value{GDBN}.
35710 In the examples below, @samp{->} and @samp{<-} are used to indicate
35711 transmitted and received data, respectively.
35713 @cindex protocol, @value{GDBN} remote serial
35714 @cindex serial protocol, @value{GDBN} remote
35715 @cindex remote serial protocol
35716 All @value{GDBN} commands and responses (other than acknowledgments
35717 and notifications, see @ref{Notification Packets}) are sent as a
35718 @var{packet}. A @var{packet} is introduced with the character
35719 @samp{$}, the actual @var{packet-data}, and the terminating character
35720 @samp{#} followed by a two-digit @var{checksum}:
35723 @code{$}@var{packet-data}@code{#}@var{checksum}
35727 @cindex checksum, for @value{GDBN} remote
35729 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35730 characters between the leading @samp{$} and the trailing @samp{#} (an
35731 eight bit unsigned checksum).
35733 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35734 specification also included an optional two-digit @var{sequence-id}:
35737 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35740 @cindex sequence-id, for @value{GDBN} remote
35742 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35743 has never output @var{sequence-id}s. Stubs that handle packets added
35744 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35746 When either the host or the target machine receives a packet, the first
35747 response expected is an acknowledgment: either @samp{+} (to indicate
35748 the package was received correctly) or @samp{-} (to request
35752 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35757 The @samp{+}/@samp{-} acknowledgments can be disabled
35758 once a connection is established.
35759 @xref{Packet Acknowledgment}, for details.
35761 The host (@value{GDBN}) sends @var{command}s, and the target (the
35762 debugging stub incorporated in your program) sends a @var{response}. In
35763 the case of step and continue @var{command}s, the response is only sent
35764 when the operation has completed, and the target has again stopped all
35765 threads in all attached processes. This is the default all-stop mode
35766 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35767 execution mode; see @ref{Remote Non-Stop}, for details.
35769 @var{packet-data} consists of a sequence of characters with the
35770 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35773 @cindex remote protocol, field separator
35774 Fields within the packet should be separated using @samp{,} @samp{;} or
35775 @samp{:}. Except where otherwise noted all numbers are represented in
35776 @sc{hex} with leading zeros suppressed.
35778 Implementors should note that prior to @value{GDBN} 5.0, the character
35779 @samp{:} could not appear as the third character in a packet (as it
35780 would potentially conflict with the @var{sequence-id}).
35782 @cindex remote protocol, binary data
35783 @anchor{Binary Data}
35784 Binary data in most packets is encoded either as two hexadecimal
35785 digits per byte of binary data. This allowed the traditional remote
35786 protocol to work over connections which were only seven-bit clean.
35787 Some packets designed more recently assume an eight-bit clean
35788 connection, and use a more efficient encoding to send and receive
35791 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35792 as an escape character. Any escaped byte is transmitted as the escape
35793 character followed by the original character XORed with @code{0x20}.
35794 For example, the byte @code{0x7d} would be transmitted as the two
35795 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35796 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35797 @samp{@}}) must always be escaped. Responses sent by the stub
35798 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35799 is not interpreted as the start of a run-length encoded sequence
35802 Response @var{data} can be run-length encoded to save space.
35803 Run-length encoding replaces runs of identical characters with one
35804 instance of the repeated character, followed by a @samp{*} and a
35805 repeat count. The repeat count is itself sent encoded, to avoid
35806 binary characters in @var{data}: a value of @var{n} is sent as
35807 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35808 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35809 code 32) for a repeat count of 3. (This is because run-length
35810 encoding starts to win for counts 3 or more.) Thus, for example,
35811 @samp{0* } is a run-length encoding of ``0000'': the space character
35812 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35815 The printable characters @samp{#} and @samp{$} or with a numeric value
35816 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35817 seven repeats (@samp{$}) can be expanded using a repeat count of only
35818 five (@samp{"}). For example, @samp{00000000} can be encoded as
35821 The error response returned for some packets includes a two character
35822 error number. That number is not well defined.
35824 @cindex empty response, for unsupported packets
35825 For any @var{command} not supported by the stub, an empty response
35826 (@samp{$#00}) should be returned. That way it is possible to extend the
35827 protocol. A newer @value{GDBN} can tell if a packet is supported based
35830 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35831 commands for register access, and the @samp{m} and @samp{M} commands
35832 for memory access. Stubs that only control single-threaded targets
35833 can implement run control with the @samp{c} (continue), and @samp{s}
35834 (step) commands. Stubs that support multi-threading targets should
35835 support the @samp{vCont} command. All other commands are optional.
35840 The following table provides a complete list of all currently defined
35841 @var{command}s and their corresponding response @var{data}.
35842 @xref{File-I/O Remote Protocol Extension}, for details about the File
35843 I/O extension of the remote protocol.
35845 Each packet's description has a template showing the packet's overall
35846 syntax, followed by an explanation of the packet's meaning. We
35847 include spaces in some of the templates for clarity; these are not
35848 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35849 separate its components. For example, a template like @samp{foo
35850 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35851 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35852 @var{baz}. @value{GDBN} does not transmit a space character between the
35853 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35856 @cindex @var{thread-id}, in remote protocol
35857 @anchor{thread-id syntax}
35858 Several packets and replies include a @var{thread-id} field to identify
35859 a thread. Normally these are positive numbers with a target-specific
35860 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35861 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35864 In addition, the remote protocol supports a multiprocess feature in
35865 which the @var{thread-id} syntax is extended to optionally include both
35866 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35867 The @var{pid} (process) and @var{tid} (thread) components each have the
35868 format described above: a positive number with target-specific
35869 interpretation formatted as a big-endian hex string, literal @samp{-1}
35870 to indicate all processes or threads (respectively), or @samp{0} to
35871 indicate an arbitrary process or thread. Specifying just a process, as
35872 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35873 error to specify all processes but a specific thread, such as
35874 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35875 for those packets and replies explicitly documented to include a process
35876 ID, rather than a @var{thread-id}.
35878 The multiprocess @var{thread-id} syntax extensions are only used if both
35879 @value{GDBN} and the stub report support for the @samp{multiprocess}
35880 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35883 Note that all packet forms beginning with an upper- or lower-case
35884 letter, other than those described here, are reserved for future use.
35886 Here are the packet descriptions.
35891 @cindex @samp{!} packet
35892 @anchor{extended mode}
35893 Enable extended mode. In extended mode, the remote server is made
35894 persistent. The @samp{R} packet is used to restart the program being
35900 The remote target both supports and has enabled extended mode.
35904 @cindex @samp{?} packet
35906 Indicate the reason the target halted. The reply is the same as for
35907 step and continue. This packet has a special interpretation when the
35908 target is in non-stop mode; see @ref{Remote Non-Stop}.
35911 @xref{Stop Reply Packets}, for the reply specifications.
35913 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35914 @cindex @samp{A} packet
35915 Initialized @code{argv[]} array passed into program. @var{arglen}
35916 specifies the number of bytes in the hex encoded byte stream
35917 @var{arg}. See @code{gdbserver} for more details.
35922 The arguments were set.
35928 @cindex @samp{b} packet
35929 (Don't use this packet; its behavior is not well-defined.)
35930 Change the serial line speed to @var{baud}.
35932 JTC: @emph{When does the transport layer state change? When it's
35933 received, or after the ACK is transmitted. In either case, there are
35934 problems if the command or the acknowledgment packet is dropped.}
35936 Stan: @emph{If people really wanted to add something like this, and get
35937 it working for the first time, they ought to modify ser-unix.c to send
35938 some kind of out-of-band message to a specially-setup stub and have the
35939 switch happen "in between" packets, so that from remote protocol's point
35940 of view, nothing actually happened.}
35942 @item B @var{addr},@var{mode}
35943 @cindex @samp{B} packet
35944 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35945 breakpoint at @var{addr}.
35947 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35948 (@pxref{insert breakpoint or watchpoint packet}).
35950 @cindex @samp{bc} packet
35953 Backward continue. Execute the target system in reverse. No parameter.
35954 @xref{Reverse Execution}, for more information.
35957 @xref{Stop Reply Packets}, for the reply specifications.
35959 @cindex @samp{bs} packet
35962 Backward single step. Execute one instruction in reverse. No parameter.
35963 @xref{Reverse Execution}, for more information.
35966 @xref{Stop Reply Packets}, for the reply specifications.
35968 @item c @r{[}@var{addr}@r{]}
35969 @cindex @samp{c} packet
35970 Continue at @var{addr}, which is the address to resume. If @var{addr}
35971 is omitted, resume at current address.
35973 This packet is deprecated for multi-threading support. @xref{vCont
35977 @xref{Stop Reply Packets}, for the reply specifications.
35979 @item C @var{sig}@r{[};@var{addr}@r{]}
35980 @cindex @samp{C} packet
35981 Continue with signal @var{sig} (hex signal number). If
35982 @samp{;@var{addr}} is omitted, resume at same address.
35984 This packet is deprecated for multi-threading support. @xref{vCont
35988 @xref{Stop Reply Packets}, for the reply specifications.
35991 @cindex @samp{d} packet
35994 Don't use this packet; instead, define a general set packet
35995 (@pxref{General Query Packets}).
35999 @cindex @samp{D} packet
36000 The first form of the packet is used to detach @value{GDBN} from the
36001 remote system. It is sent to the remote target
36002 before @value{GDBN} disconnects via the @code{detach} command.
36004 The second form, including a process ID, is used when multiprocess
36005 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36006 detach only a specific process. The @var{pid} is specified as a
36007 big-endian hex string.
36017 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36018 @cindex @samp{F} packet
36019 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36020 This is part of the File-I/O protocol extension. @xref{File-I/O
36021 Remote Protocol Extension}, for the specification.
36024 @anchor{read registers packet}
36025 @cindex @samp{g} packet
36026 Read general registers.
36030 @item @var{XX@dots{}}
36031 Each byte of register data is described by two hex digits. The bytes
36032 with the register are transmitted in target byte order. The size of
36033 each register and their position within the @samp{g} packet are
36034 determined by the @value{GDBN} internal gdbarch functions
36035 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36037 When reading registers from a trace frame (@pxref{Analyze Collected
36038 Data,,Using the Collected Data}), the stub may also return a string of
36039 literal @samp{x}'s in place of the register data digits, to indicate
36040 that the corresponding register has not been collected, thus its value
36041 is unavailable. For example, for an architecture with 4 registers of
36042 4 bytes each, the following reply indicates to @value{GDBN} that
36043 registers 0 and 2 have not been collected, while registers 1 and 3
36044 have been collected, and both have zero value:
36048 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36055 @item G @var{XX@dots{}}
36056 @cindex @samp{G} packet
36057 Write general registers. @xref{read registers packet}, for a
36058 description of the @var{XX@dots{}} data.
36068 @item H @var{op} @var{thread-id}
36069 @cindex @samp{H} packet
36070 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36071 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36072 should be @samp{c} for step and continue operations (note that this
36073 is deprecated, supporting the @samp{vCont} command is a better
36074 option), and @samp{g} for other operations. The thread designator
36075 @var{thread-id} has the format and interpretation described in
36076 @ref{thread-id syntax}.
36087 @c 'H': How restrictive (or permissive) is the thread model. If a
36088 @c thread is selected and stopped, are other threads allowed
36089 @c to continue to execute? As I mentioned above, I think the
36090 @c semantics of each command when a thread is selected must be
36091 @c described. For example:
36093 @c 'g': If the stub supports threads and a specific thread is
36094 @c selected, returns the register block from that thread;
36095 @c otherwise returns current registers.
36097 @c 'G' If the stub supports threads and a specific thread is
36098 @c selected, sets the registers of the register block of
36099 @c that thread; otherwise sets current registers.
36101 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36102 @anchor{cycle step packet}
36103 @cindex @samp{i} packet
36104 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36105 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36106 step starting at that address.
36109 @cindex @samp{I} packet
36110 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36114 @cindex @samp{k} packet
36117 The exact effect of this packet is not specified.
36119 For a bare-metal target, it may power cycle or reset the target
36120 system. For that reason, the @samp{k} packet has no reply.
36122 For a single-process target, it may kill that process if possible.
36124 A multiple-process target may choose to kill just one process, or all
36125 that are under @value{GDBN}'s control. For more precise control, use
36126 the vKill packet (@pxref{vKill packet}).
36128 If the target system immediately closes the connection in response to
36129 @samp{k}, @value{GDBN} does not consider the lack of packet
36130 acknowledgment to be an error, and assumes the kill was successful.
36132 If connected using @kbd{target extended-remote}, and the target does
36133 not close the connection in response to a kill request, @value{GDBN}
36134 probes the target state as if a new connection was opened
36135 (@pxref{? packet}).
36137 @item m @var{addr},@var{length}
36138 @cindex @samp{m} packet
36139 Read @var{length} addressable memory units starting at address @var{addr}
36140 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36141 any particular boundary.
36143 The stub need not use any particular size or alignment when gathering
36144 data from memory for the response; even if @var{addr} is word-aligned
36145 and @var{length} is a multiple of the word size, the stub is free to
36146 use byte accesses, or not. For this reason, this packet may not be
36147 suitable for accessing memory-mapped I/O devices.
36148 @cindex alignment of remote memory accesses
36149 @cindex size of remote memory accesses
36150 @cindex memory, alignment and size of remote accesses
36154 @item @var{XX@dots{}}
36155 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36156 The reply may contain fewer addressable memory units than requested if the
36157 server was able to read only part of the region of memory.
36162 @item M @var{addr},@var{length}:@var{XX@dots{}}
36163 @cindex @samp{M} packet
36164 Write @var{length} addressable memory units starting at address @var{addr}
36165 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36166 byte is transmitted as a two-digit hexadecimal number.
36173 for an error (this includes the case where only part of the data was
36178 @cindex @samp{p} packet
36179 Read the value of register @var{n}; @var{n} is in hex.
36180 @xref{read registers packet}, for a description of how the returned
36181 register value is encoded.
36185 @item @var{XX@dots{}}
36186 the register's value
36190 Indicating an unrecognized @var{query}.
36193 @item P @var{n@dots{}}=@var{r@dots{}}
36194 @anchor{write register packet}
36195 @cindex @samp{P} packet
36196 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36197 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36198 digits for each byte in the register (target byte order).
36208 @item q @var{name} @var{params}@dots{}
36209 @itemx Q @var{name} @var{params}@dots{}
36210 @cindex @samp{q} packet
36211 @cindex @samp{Q} packet
36212 General query (@samp{q}) and set (@samp{Q}). These packets are
36213 described fully in @ref{General Query Packets}.
36216 @cindex @samp{r} packet
36217 Reset the entire system.
36219 Don't use this packet; use the @samp{R} packet instead.
36222 @cindex @samp{R} packet
36223 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36224 This packet is only available in extended mode (@pxref{extended mode}).
36226 The @samp{R} packet has no reply.
36228 @item s @r{[}@var{addr}@r{]}
36229 @cindex @samp{s} packet
36230 Single step, resuming at @var{addr}. If
36231 @var{addr} is omitted, resume at same address.
36233 This packet is deprecated for multi-threading support. @xref{vCont
36237 @xref{Stop Reply Packets}, for the reply specifications.
36239 @item S @var{sig}@r{[};@var{addr}@r{]}
36240 @anchor{step with signal packet}
36241 @cindex @samp{S} packet
36242 Step with signal. This is analogous to the @samp{C} packet, but
36243 requests a single-step, rather than a normal resumption of execution.
36245 This packet is deprecated for multi-threading support. @xref{vCont
36249 @xref{Stop Reply Packets}, for the reply specifications.
36251 @item t @var{addr}:@var{PP},@var{MM}
36252 @cindex @samp{t} packet
36253 Search backwards starting at address @var{addr} for a match with pattern
36254 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36255 There must be at least 3 digits in @var{addr}.
36257 @item T @var{thread-id}
36258 @cindex @samp{T} packet
36259 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36264 thread is still alive
36270 Packets starting with @samp{v} are identified by a multi-letter name,
36271 up to the first @samp{;} or @samp{?} (or the end of the packet).
36273 @item vAttach;@var{pid}
36274 @cindex @samp{vAttach} packet
36275 Attach to a new process with the specified process ID @var{pid}.
36276 The process ID is a
36277 hexadecimal integer identifying the process. In all-stop mode, all
36278 threads in the attached process are stopped; in non-stop mode, it may be
36279 attached without being stopped if that is supported by the target.
36281 @c In non-stop mode, on a successful vAttach, the stub should set the
36282 @c current thread to a thread of the newly-attached process. After
36283 @c attaching, GDB queries for the attached process's thread ID with qC.
36284 @c Also note that, from a user perspective, whether or not the
36285 @c target is stopped on attach in non-stop mode depends on whether you
36286 @c use the foreground or background version of the attach command, not
36287 @c on what vAttach does; GDB does the right thing with respect to either
36288 @c stopping or restarting threads.
36290 This packet is only available in extended mode (@pxref{extended mode}).
36296 @item @r{Any stop packet}
36297 for success in all-stop mode (@pxref{Stop Reply Packets})
36299 for success in non-stop mode (@pxref{Remote Non-Stop})
36302 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36303 @cindex @samp{vCont} packet
36304 @anchor{vCont packet}
36305 Resume the inferior, specifying different actions for each thread.
36307 For each inferior thread, the leftmost action with a matching
36308 @var{thread-id} is applied. Threads that don't match any action
36309 remain in their current state. Thread IDs are specified using the
36310 syntax described in @ref{thread-id syntax}. If multiprocess
36311 extensions (@pxref{multiprocess extensions}) are supported, actions
36312 can be specified to match all threads in a process by using the
36313 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36314 @var{thread-id} matches all threads. Specifying no actions is an
36317 Currently supported actions are:
36323 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36327 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36330 @item r @var{start},@var{end}
36331 Step once, and then keep stepping as long as the thread stops at
36332 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36333 The remote stub reports a stop reply when either the thread goes out
36334 of the range or is stopped due to an unrelated reason, such as hitting
36335 a breakpoint. @xref{range stepping}.
36337 If the range is empty (@var{start} == @var{end}), then the action
36338 becomes equivalent to the @samp{s} action. In other words,
36339 single-step once, and report the stop (even if the stepped instruction
36340 jumps to @var{start}).
36342 (A stop reply may be sent at any point even if the PC is still within
36343 the stepping range; for example, it is valid to implement this packet
36344 in a degenerate way as a single instruction step operation.)
36348 The optional argument @var{addr} normally associated with the
36349 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36350 not supported in @samp{vCont}.
36352 The @samp{t} action is only relevant in non-stop mode
36353 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36354 A stop reply should be generated for any affected thread not already stopped.
36355 When a thread is stopped by means of a @samp{t} action,
36356 the corresponding stop reply should indicate that the thread has stopped with
36357 signal @samp{0}, regardless of whether the target uses some other signal
36358 as an implementation detail.
36360 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36361 @samp{r} actions for threads that are already running. Conversely,
36362 the server must ignore @samp{t} actions for threads that are already
36365 @emph{Note:} In non-stop mode, a thread is considered running until
36366 @value{GDBN} acknowleges an asynchronous stop notification for it with
36367 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36369 The stub must support @samp{vCont} if it reports support for
36370 multiprocess extensions (@pxref{multiprocess extensions}).
36373 @xref{Stop Reply Packets}, for the reply specifications.
36376 @cindex @samp{vCont?} packet
36377 Request a list of actions supported by the @samp{vCont} packet.
36381 @item vCont@r{[};@var{action}@dots{}@r{]}
36382 The @samp{vCont} packet is supported. Each @var{action} is a supported
36383 command in the @samp{vCont} packet.
36385 The @samp{vCont} packet is not supported.
36388 @anchor{vCtrlC packet}
36390 @cindex @samp{vCtrlC} packet
36391 Interrupt remote target as if a control-C was pressed on the remote
36392 terminal. This is the equivalent to reacting to the @code{^C}
36393 (@samp{\003}, the control-C character) character in all-stop mode
36394 while the target is running, except this works in non-stop mode.
36395 @xref{interrupting remote targets}, for more info on the all-stop
36406 @item vFile:@var{operation}:@var{parameter}@dots{}
36407 @cindex @samp{vFile} packet
36408 Perform a file operation on the target system. For details,
36409 see @ref{Host I/O Packets}.
36411 @item vFlashErase:@var{addr},@var{length}
36412 @cindex @samp{vFlashErase} packet
36413 Direct the stub to erase @var{length} bytes of flash starting at
36414 @var{addr}. The region may enclose any number of flash blocks, but
36415 its start and end must fall on block boundaries, as indicated by the
36416 flash block size appearing in the memory map (@pxref{Memory Map
36417 Format}). @value{GDBN} groups flash memory programming operations
36418 together, and sends a @samp{vFlashDone} request after each group; the
36419 stub is allowed to delay erase operation until the @samp{vFlashDone}
36420 packet is received.
36430 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36431 @cindex @samp{vFlashWrite} packet
36432 Direct the stub to write data to flash address @var{addr}. The data
36433 is passed in binary form using the same encoding as for the @samp{X}
36434 packet (@pxref{Binary Data}). The memory ranges specified by
36435 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36436 not overlap, and must appear in order of increasing addresses
36437 (although @samp{vFlashErase} packets for higher addresses may already
36438 have been received; the ordering is guaranteed only between
36439 @samp{vFlashWrite} packets). If a packet writes to an address that was
36440 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36441 target-specific method, the results are unpredictable.
36449 for vFlashWrite addressing non-flash memory
36455 @cindex @samp{vFlashDone} packet
36456 Indicate to the stub that flash programming operation is finished.
36457 The stub is permitted to delay or batch the effects of a group of
36458 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36459 @samp{vFlashDone} packet is received. The contents of the affected
36460 regions of flash memory are unpredictable until the @samp{vFlashDone}
36461 request is completed.
36463 @item vKill;@var{pid}
36464 @cindex @samp{vKill} packet
36465 @anchor{vKill packet}
36466 Kill the process with the specified process ID @var{pid}, which is a
36467 hexadecimal integer identifying the process. This packet is used in
36468 preference to @samp{k} when multiprocess protocol extensions are
36469 supported; see @ref{multiprocess extensions}.
36479 @item vMustReplyEmpty
36480 @cindex @samp{vMustReplyEmpty} packet
36481 The correct reply to an unknown @samp{v} packet is to return the empty
36482 string, however, some older versions of @command{gdbserver} would
36483 incorrectly return @samp{OK} for unknown @samp{v} packets.
36485 The @samp{vMustReplyEmpty} is used as a feature test to check how
36486 @command{gdbserver} handles unknown packets, it is important that this
36487 packet be handled in the same way as other unknown @samp{v} packets.
36488 If this packet is handled differently to other unknown @samp{v}
36489 packets then it is possile that @value{GDBN} may run into problems in
36490 other areas, specifically around use of @samp{vFile:setfs:}.
36492 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36493 @cindex @samp{vRun} packet
36494 Run the program @var{filename}, passing it each @var{argument} on its
36495 command line. The file and arguments are hex-encoded strings. If
36496 @var{filename} is an empty string, the stub may use a default program
36497 (e.g.@: the last program run). The program is created in the stopped
36500 @c FIXME: What about non-stop mode?
36502 This packet is only available in extended mode (@pxref{extended mode}).
36508 @item @r{Any stop packet}
36509 for success (@pxref{Stop Reply Packets})
36513 @cindex @samp{vStopped} packet
36514 @xref{Notification Packets}.
36516 @item X @var{addr},@var{length}:@var{XX@dots{}}
36518 @cindex @samp{X} packet
36519 Write data to memory, where the data is transmitted in binary.
36520 Memory is specified by its address @var{addr} and number of addressable memory
36521 units @var{length} (@pxref{addressable memory unit});
36522 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36532 @item z @var{type},@var{addr},@var{kind}
36533 @itemx Z @var{type},@var{addr},@var{kind}
36534 @anchor{insert breakpoint or watchpoint packet}
36535 @cindex @samp{z} packet
36536 @cindex @samp{Z} packets
36537 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36538 watchpoint starting at address @var{address} of kind @var{kind}.
36540 Each breakpoint and watchpoint packet @var{type} is documented
36543 @emph{Implementation notes: A remote target shall return an empty string
36544 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36545 remote target shall support either both or neither of a given
36546 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36547 avoid potential problems with duplicate packets, the operations should
36548 be implemented in an idempotent way.}
36550 @item z0,@var{addr},@var{kind}
36551 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36552 @cindex @samp{z0} packet
36553 @cindex @samp{Z0} packet
36554 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36555 @var{addr} of type @var{kind}.
36557 A software breakpoint is implemented by replacing the instruction at
36558 @var{addr} with a software breakpoint or trap instruction. The
36559 @var{kind} is target-specific and typically indicates the size of the
36560 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36561 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36562 architectures have additional meanings for @var{kind}
36563 (@pxref{Architecture-Specific Protocol Details}); if no
36564 architecture-specific value is being used, it should be @samp{0}.
36565 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36566 conditional expressions in bytecode form that should be evaluated on
36567 the target's side. These are the conditions that should be taken into
36568 consideration when deciding if the breakpoint trigger should be
36569 reported back to @value{GDBN}.
36571 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36572 for how to best report a software breakpoint event to @value{GDBN}.
36574 The @var{cond_list} parameter is comprised of a series of expressions,
36575 concatenated without separators. Each expression has the following form:
36579 @item X @var{len},@var{expr}
36580 @var{len} is the length of the bytecode expression and @var{expr} is the
36581 actual conditional expression in bytecode form.
36585 The optional @var{cmd_list} parameter introduces commands that may be
36586 run on the target, rather than being reported back to @value{GDBN}.
36587 The parameter starts with a numeric flag @var{persist}; if the flag is
36588 nonzero, then the breakpoint may remain active and the commands
36589 continue to be run even when @value{GDBN} disconnects from the target.
36590 Following this flag is a series of expressions concatenated with no
36591 separators. Each expression has the following form:
36595 @item X @var{len},@var{expr}
36596 @var{len} is the length of the bytecode expression and @var{expr} is the
36597 actual commands expression in bytecode form.
36601 @emph{Implementation note: It is possible for a target to copy or move
36602 code that contains software breakpoints (e.g., when implementing
36603 overlays). The behavior of this packet, in the presence of such a
36604 target, is not defined.}
36616 @item z1,@var{addr},@var{kind}
36617 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36618 @cindex @samp{z1} packet
36619 @cindex @samp{Z1} packet
36620 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36621 address @var{addr}.
36623 A hardware breakpoint is implemented using a mechanism that is not
36624 dependent on being able to modify the target's memory. The
36625 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36626 same meaning as in @samp{Z0} packets.
36628 @emph{Implementation note: A hardware breakpoint is not affected by code
36641 @item z2,@var{addr},@var{kind}
36642 @itemx Z2,@var{addr},@var{kind}
36643 @cindex @samp{z2} packet
36644 @cindex @samp{Z2} packet
36645 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36646 The number of bytes to watch is specified by @var{kind}.
36658 @item z3,@var{addr},@var{kind}
36659 @itemx Z3,@var{addr},@var{kind}
36660 @cindex @samp{z3} packet
36661 @cindex @samp{Z3} packet
36662 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36663 The number of bytes to watch is specified by @var{kind}.
36675 @item z4,@var{addr},@var{kind}
36676 @itemx Z4,@var{addr},@var{kind}
36677 @cindex @samp{z4} packet
36678 @cindex @samp{Z4} packet
36679 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36680 The number of bytes to watch is specified by @var{kind}.
36694 @node Stop Reply Packets
36695 @section Stop Reply Packets
36696 @cindex stop reply packets
36698 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36699 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36700 receive any of the below as a reply. Except for @samp{?}
36701 and @samp{vStopped}, that reply is only returned
36702 when the target halts. In the below the exact meaning of @dfn{signal
36703 number} is defined by the header @file{include/gdb/signals.h} in the
36704 @value{GDBN} source code.
36706 In non-stop mode, the server will simply reply @samp{OK} to commands
36707 such as @samp{vCont}; any stop will be the subject of a future
36708 notification. @xref{Remote Non-Stop}.
36710 As in the description of request packets, we include spaces in the
36711 reply templates for clarity; these are not part of the reply packet's
36712 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36718 The program received signal number @var{AA} (a two-digit hexadecimal
36719 number). This is equivalent to a @samp{T} response with no
36720 @var{n}:@var{r} pairs.
36722 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36723 @cindex @samp{T} packet reply
36724 The program received signal number @var{AA} (a two-digit hexadecimal
36725 number). This is equivalent to an @samp{S} response, except that the
36726 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36727 and other information directly in the stop reply packet, reducing
36728 round-trip latency. Single-step and breakpoint traps are reported
36729 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36733 If @var{n} is a hexadecimal number, it is a register number, and the
36734 corresponding @var{r} gives that register's value. The data @var{r} is a
36735 series of bytes in target byte order, with each byte given by a
36736 two-digit hex number.
36739 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36740 the stopped thread, as specified in @ref{thread-id syntax}.
36743 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36744 the core on which the stop event was detected.
36747 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36748 specific event that stopped the target. The currently defined stop
36749 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36750 signal. At most one stop reason should be present.
36753 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36754 and go on to the next; this allows us to extend the protocol in the
36758 The currently defined stop reasons are:
36764 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36767 @item syscall_entry
36768 @itemx syscall_return
36769 The packet indicates a syscall entry or return, and @var{r} is the
36770 syscall number, in hex.
36772 @cindex shared library events, remote reply
36774 The packet indicates that the loaded libraries have changed.
36775 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36776 list of loaded libraries. The @var{r} part is ignored.
36778 @cindex replay log events, remote reply
36780 The packet indicates that the target cannot continue replaying
36781 logged execution events, because it has reached the end (or the
36782 beginning when executing backward) of the log. The value of @var{r}
36783 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36784 for more information.
36787 @anchor{swbreak stop reason}
36788 The packet indicates a software breakpoint instruction was executed,
36789 irrespective of whether it was @value{GDBN} that planted the
36790 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36791 part must be left empty.
36793 On some architectures, such as x86, at the architecture level, when a
36794 breakpoint instruction executes the program counter points at the
36795 breakpoint address plus an offset. On such targets, the stub is
36796 responsible for adjusting the PC to point back at the breakpoint
36799 This packet should not be sent by default; older @value{GDBN} versions
36800 did not support it. @value{GDBN} requests it, by supplying an
36801 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36802 remote stub must also supply the appropriate @samp{qSupported} feature
36803 indicating support.
36805 This packet is required for correct non-stop mode operation.
36808 The packet indicates the target stopped for a hardware breakpoint.
36809 The @var{r} part must be left empty.
36811 The same remarks about @samp{qSupported} and non-stop mode above
36814 @cindex fork events, remote reply
36816 The packet indicates that @code{fork} was called, and @var{r}
36817 is the thread ID of the new child process. Refer to
36818 @ref{thread-id syntax} for the format of the @var{thread-id}
36819 field. This packet is only applicable to targets that support
36822 This packet should not be sent by default; older @value{GDBN} versions
36823 did not support it. @value{GDBN} requests it, by supplying an
36824 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36825 remote stub must also supply the appropriate @samp{qSupported} feature
36826 indicating support.
36828 @cindex vfork events, remote reply
36830 The packet indicates that @code{vfork} was called, and @var{r}
36831 is the thread ID of the new child process. Refer to
36832 @ref{thread-id syntax} for the format of the @var{thread-id}
36833 field. This packet is only applicable to targets that support
36836 This packet should not be sent by default; older @value{GDBN} versions
36837 did not support it. @value{GDBN} requests it, by supplying an
36838 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36839 remote stub must also supply the appropriate @samp{qSupported} feature
36840 indicating support.
36842 @cindex vforkdone events, remote reply
36844 The packet indicates that a child process created by a vfork
36845 has either called @code{exec} or terminated, so that the
36846 address spaces of the parent and child process are no longer
36847 shared. The @var{r} part is ignored. This packet is only
36848 applicable to targets that support vforkdone events.
36850 This packet should not be sent by default; older @value{GDBN} versions
36851 did not support it. @value{GDBN} requests it, by supplying an
36852 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36853 remote stub must also supply the appropriate @samp{qSupported} feature
36854 indicating support.
36856 @cindex exec events, remote reply
36858 The packet indicates that @code{execve} was called, and @var{r}
36859 is the absolute pathname of the file that was executed, in hex.
36860 This packet is only applicable to targets that support exec events.
36862 This packet should not be sent by default; older @value{GDBN} versions
36863 did not support it. @value{GDBN} requests it, by supplying an
36864 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36865 remote stub must also supply the appropriate @samp{qSupported} feature
36866 indicating support.
36868 @cindex thread create event, remote reply
36869 @anchor{thread create event}
36871 The packet indicates that the thread was just created. The new thread
36872 is stopped until @value{GDBN} sets it running with a resumption packet
36873 (@pxref{vCont packet}). This packet should not be sent by default;
36874 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36875 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36876 @var{r} part is ignored.
36881 @itemx W @var{AA} ; process:@var{pid}
36882 The process exited, and @var{AA} is the exit status. This is only
36883 applicable to certain targets.
36885 The second form of the response, including the process ID of the
36886 exited process, can be used only when @value{GDBN} has reported
36887 support for multiprocess protocol extensions; see @ref{multiprocess
36888 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36892 @itemx X @var{AA} ; process:@var{pid}
36893 The process terminated with signal @var{AA}.
36895 The second form of the response, including the process ID of the
36896 terminated process, can be used only when @value{GDBN} has reported
36897 support for multiprocess protocol extensions; see @ref{multiprocess
36898 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36901 @anchor{thread exit event}
36902 @cindex thread exit event, remote reply
36903 @item w @var{AA} ; @var{tid}
36905 The thread exited, and @var{AA} is the exit status. This response
36906 should not be sent by default; @value{GDBN} requests it with the
36907 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36908 @var{AA} is formatted as a big-endian hex string.
36911 There are no resumed threads left in the target. In other words, even
36912 though the process is alive, the last resumed thread has exited. For
36913 example, say the target process has two threads: thread 1 and thread
36914 2. The client leaves thread 1 stopped, and resumes thread 2, which
36915 subsequently exits. At this point, even though the process is still
36916 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36917 executing either. The @samp{N} stop reply thus informs the client
36918 that it can stop waiting for stop replies. This packet should not be
36919 sent by default; older @value{GDBN} versions did not support it.
36920 @value{GDBN} requests it, by supplying an appropriate
36921 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36922 also supply the appropriate @samp{qSupported} feature indicating
36925 @item O @var{XX}@dots{}
36926 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36927 written as the program's console output. This can happen at any time
36928 while the program is running and the debugger should continue to wait
36929 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36931 @item F @var{call-id},@var{parameter}@dots{}
36932 @var{call-id} is the identifier which says which host system call should
36933 be called. This is just the name of the function. Translation into the
36934 correct system call is only applicable as it's defined in @value{GDBN}.
36935 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36938 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36939 this very system call.
36941 The target replies with this packet when it expects @value{GDBN} to
36942 call a host system call on behalf of the target. @value{GDBN} replies
36943 with an appropriate @samp{F} packet and keeps up waiting for the next
36944 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36945 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36946 Protocol Extension}, for more details.
36950 @node General Query Packets
36951 @section General Query Packets
36952 @cindex remote query requests
36954 Packets starting with @samp{q} are @dfn{general query packets};
36955 packets starting with @samp{Q} are @dfn{general set packets}. General
36956 query and set packets are a semi-unified form for retrieving and
36957 sending information to and from the stub.
36959 The initial letter of a query or set packet is followed by a name
36960 indicating what sort of thing the packet applies to. For example,
36961 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36962 definitions with the stub. These packet names follow some
36967 The name must not contain commas, colons or semicolons.
36969 Most @value{GDBN} query and set packets have a leading upper case
36972 The names of custom vendor packets should use a company prefix, in
36973 lower case, followed by a period. For example, packets designed at
36974 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36975 foos) or @samp{Qacme.bar} (for setting bars).
36978 The name of a query or set packet should be separated from any
36979 parameters by a @samp{:}; the parameters themselves should be
36980 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36981 full packet name, and check for a separator or the end of the packet,
36982 in case two packet names share a common prefix. New packets should not begin
36983 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36984 packets predate these conventions, and have arguments without any terminator
36985 for the packet name; we suspect they are in widespread use in places that
36986 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36987 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36990 Like the descriptions of the other packets, each description here
36991 has a template showing the packet's overall syntax, followed by an
36992 explanation of the packet's meaning. We include spaces in some of the
36993 templates for clarity; these are not part of the packet's syntax. No
36994 @value{GDBN} packet uses spaces to separate its components.
36996 Here are the currently defined query and set packets:
37002 Turn on or off the agent as a helper to perform some debugging operations
37003 delegated from @value{GDBN} (@pxref{Control Agent}).
37005 @item QAllow:@var{op}:@var{val}@dots{}
37006 @cindex @samp{QAllow} packet
37007 Specify which operations @value{GDBN} expects to request of the
37008 target, as a semicolon-separated list of operation name and value
37009 pairs. Possible values for @var{op} include @samp{WriteReg},
37010 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37011 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37012 indicating that @value{GDBN} will not request the operation, or 1,
37013 indicating that it may. (The target can then use this to set up its
37014 own internals optimally, for instance if the debugger never expects to
37015 insert breakpoints, it may not need to install its own trap handler.)
37018 @cindex current thread, remote request
37019 @cindex @samp{qC} packet
37020 Return the current thread ID.
37024 @item QC @var{thread-id}
37025 Where @var{thread-id} is a thread ID as documented in
37026 @ref{thread-id syntax}.
37027 @item @r{(anything else)}
37028 Any other reply implies the old thread ID.
37031 @item qCRC:@var{addr},@var{length}
37032 @cindex CRC of memory block, remote request
37033 @cindex @samp{qCRC} packet
37034 @anchor{qCRC packet}
37035 Compute the CRC checksum of a block of memory using CRC-32 defined in
37036 IEEE 802.3. The CRC is computed byte at a time, taking the most
37037 significant bit of each byte first. The initial pattern code
37038 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37040 @emph{Note:} This is the same CRC used in validating separate debug
37041 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37042 Files}). However the algorithm is slightly different. When validating
37043 separate debug files, the CRC is computed taking the @emph{least}
37044 significant bit of each byte first, and the final result is inverted to
37045 detect trailing zeros.
37050 An error (such as memory fault)
37051 @item C @var{crc32}
37052 The specified memory region's checksum is @var{crc32}.
37055 @item QDisableRandomization:@var{value}
37056 @cindex disable address space randomization, remote request
37057 @cindex @samp{QDisableRandomization} packet
37058 Some target operating systems will randomize the virtual address space
37059 of the inferior process as a security feature, but provide a feature
37060 to disable such randomization, e.g.@: to allow for a more deterministic
37061 debugging experience. On such systems, this packet with a @var{value}
37062 of 1 directs the target to disable address space randomization for
37063 processes subsequently started via @samp{vRun} packets, while a packet
37064 with a @var{value} of 0 tells the target to enable address space
37067 This packet is only available in extended mode (@pxref{extended mode}).
37072 The request succeeded.
37075 An error occurred. The error number @var{nn} is given as hex digits.
37078 An empty reply indicates that @samp{QDisableRandomization} is not supported
37082 This packet is not probed by default; the remote stub must request it,
37083 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37084 This should only be done on targets that actually support disabling
37085 address space randomization.
37087 @item QStartupWithShell:@var{value}
37088 @cindex startup with shell, remote request
37089 @cindex @samp{QStartupWithShell} packet
37090 On UNIX-like targets, it is possible to start the inferior using a
37091 shell program. This is the default behavior on both @value{GDBN} and
37092 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37093 used to inform @command{gdbserver} whether it should start the
37094 inferior using a shell or not.
37096 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37097 to start the inferior. If @var{value} is @samp{1},
37098 @command{gdbserver} will use a shell to start the inferior. All other
37099 values are considered an error.
37101 This packet is only available in extended mode (@pxref{extended
37107 The request succeeded.
37110 An error occurred. The error number @var{nn} is given as hex digits.
37113 This packet is not probed by default; the remote stub must request it,
37114 by supplying an appropriate @samp{qSupported} response
37115 (@pxref{qSupported}). This should only be done on targets that
37116 actually support starting the inferior using a shell.
37118 Use of this packet is controlled by the @code{set startup-with-shell}
37119 command; @pxref{set startup-with-shell}.
37121 @item QEnvironmentHexEncoded:@var{hex-value}
37122 @anchor{QEnvironmentHexEncoded}
37123 @cindex set environment variable, remote request
37124 @cindex @samp{QEnvironmentHexEncoded} packet
37125 On UNIX-like targets, it is possible to set environment variables that
37126 will be passed to the inferior during the startup process. This
37127 packet is used to inform @command{gdbserver} of an environment
37128 variable that has been defined by the user on @value{GDBN} (@pxref{set
37131 The packet is composed by @var{hex-value}, an hex encoded
37132 representation of the @var{name=value} format representing an
37133 environment variable. The name of the environment variable is
37134 represented by @var{name}, and the value to be assigned to the
37135 environment variable is represented by @var{value}. If the variable
37136 has no value (i.e., the value is @code{null}), then @var{value} will
37139 This packet is only available in extended mode (@pxref{extended
37145 The request succeeded.
37148 This packet is not probed by default; the remote stub must request it,
37149 by supplying an appropriate @samp{qSupported} response
37150 (@pxref{qSupported}). This should only be done on targets that
37151 actually support passing environment variables to the starting
37154 This packet is related to the @code{set environment} command;
37155 @pxref{set environment}.
37157 @item QEnvironmentUnset:@var{hex-value}
37158 @anchor{QEnvironmentUnset}
37159 @cindex unset environment variable, remote request
37160 @cindex @samp{QEnvironmentUnset} packet
37161 On UNIX-like targets, it is possible to unset environment variables
37162 before starting the inferior in the remote target. This packet is
37163 used to inform @command{gdbserver} of an environment variable that has
37164 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37166 The packet is composed by @var{hex-value}, an hex encoded
37167 representation of the name of the environment variable to be unset.
37169 This packet is only available in extended mode (@pxref{extended
37175 The request succeeded.
37178 This packet is not probed by default; the remote stub must request it,
37179 by supplying an appropriate @samp{qSupported} response
37180 (@pxref{qSupported}). This should only be done on targets that
37181 actually support passing environment variables to the starting
37184 This packet is related to the @code{unset environment} command;
37185 @pxref{unset environment}.
37187 @item QEnvironmentReset
37188 @anchor{QEnvironmentReset}
37189 @cindex reset environment, remote request
37190 @cindex @samp{QEnvironmentReset} packet
37191 On UNIX-like targets, this packet is used to reset the state of
37192 environment variables in the remote target before starting the
37193 inferior. In this context, reset means unsetting all environment
37194 variables that were previously set by the user (i.e., were not
37195 initially present in the environment). It is sent to
37196 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37197 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37198 (@pxref{QEnvironmentUnset}) packets.
37200 This packet is only available in extended mode (@pxref{extended
37206 The request succeeded.
37209 This packet is not probed by default; the remote stub must request it,
37210 by supplying an appropriate @samp{qSupported} response
37211 (@pxref{qSupported}). This should only be done on targets that
37212 actually support passing environment variables to the starting
37215 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37216 @anchor{QSetWorkingDir packet}
37217 @cindex set working directory, remote request
37218 @cindex @samp{QSetWorkingDir} packet
37219 This packet is used to inform the remote server of the intended
37220 current working directory for programs that are going to be executed.
37222 The packet is composed by @var{directory}, an hex encoded
37223 representation of the directory that the remote inferior will use as
37224 its current working directory. If @var{directory} is an empty string,
37225 the remote server should reset the inferior's current working
37226 directory to its original, empty value.
37228 This packet is only available in extended mode (@pxref{extended
37234 The request succeeded.
37238 @itemx qsThreadInfo
37239 @cindex list active threads, remote request
37240 @cindex @samp{qfThreadInfo} packet
37241 @cindex @samp{qsThreadInfo} packet
37242 Obtain a list of all active thread IDs from the target (OS). Since there
37243 may be too many active threads to fit into one reply packet, this query
37244 works iteratively: it may require more than one query/reply sequence to
37245 obtain the entire list of threads. The first query of the sequence will
37246 be the @samp{qfThreadInfo} query; subsequent queries in the
37247 sequence will be the @samp{qsThreadInfo} query.
37249 NOTE: This packet replaces the @samp{qL} query (see below).
37253 @item m @var{thread-id}
37255 @item m @var{thread-id},@var{thread-id}@dots{}
37256 a comma-separated list of thread IDs
37258 (lower case letter @samp{L}) denotes end of list.
37261 In response to each query, the target will reply with a list of one or
37262 more thread IDs, separated by commas.
37263 @value{GDBN} will respond to each reply with a request for more thread
37264 ids (using the @samp{qs} form of the query), until the target responds
37265 with @samp{l} (lower-case ell, for @dfn{last}).
37266 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37269 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37270 initial connection with the remote target, and the very first thread ID
37271 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37272 message. Therefore, the stub should ensure that the first thread ID in
37273 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37275 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37276 @cindex get thread-local storage address, remote request
37277 @cindex @samp{qGetTLSAddr} packet
37278 Fetch the address associated with thread local storage specified
37279 by @var{thread-id}, @var{offset}, and @var{lm}.
37281 @var{thread-id} is the thread ID associated with the
37282 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37284 @var{offset} is the (big endian, hex encoded) offset associated with the
37285 thread local variable. (This offset is obtained from the debug
37286 information associated with the variable.)
37288 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37289 load module associated with the thread local storage. For example,
37290 a @sc{gnu}/Linux system will pass the link map address of the shared
37291 object associated with the thread local storage under consideration.
37292 Other operating environments may choose to represent the load module
37293 differently, so the precise meaning of this parameter will vary.
37297 @item @var{XX}@dots{}
37298 Hex encoded (big endian) bytes representing the address of the thread
37299 local storage requested.
37302 An error occurred. The error number @var{nn} is given as hex digits.
37305 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37308 @item qGetTIBAddr:@var{thread-id}
37309 @cindex get thread information block address
37310 @cindex @samp{qGetTIBAddr} packet
37311 Fetch address of the Windows OS specific Thread Information Block.
37313 @var{thread-id} is the thread ID associated with the thread.
37317 @item @var{XX}@dots{}
37318 Hex encoded (big endian) bytes representing the linear address of the
37319 thread information block.
37322 An error occured. This means that either the thread was not found, or the
37323 address could not be retrieved.
37326 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37329 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37330 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37331 digit) is one to indicate the first query and zero to indicate a
37332 subsequent query; @var{threadcount} (two hex digits) is the maximum
37333 number of threads the response packet can contain; and @var{nextthread}
37334 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37335 returned in the response as @var{argthread}.
37337 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37341 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37342 Where: @var{count} (two hex digits) is the number of threads being
37343 returned; @var{done} (one hex digit) is zero to indicate more threads
37344 and one indicates no further threads; @var{argthreadid} (eight hex
37345 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37346 is a sequence of thread IDs, @var{threadid} (eight hex
37347 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37351 @cindex section offsets, remote request
37352 @cindex @samp{qOffsets} packet
37353 Get section offsets that the target used when relocating the downloaded
37358 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37359 Relocate the @code{Text} section by @var{xxx} from its original address.
37360 Relocate the @code{Data} section by @var{yyy} from its original address.
37361 If the object file format provides segment information (e.g.@: @sc{elf}
37362 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37363 segments by the supplied offsets.
37365 @emph{Note: while a @code{Bss} offset may be included in the response,
37366 @value{GDBN} ignores this and instead applies the @code{Data} offset
37367 to the @code{Bss} section.}
37369 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37370 Relocate the first segment of the object file, which conventionally
37371 contains program code, to a starting address of @var{xxx}. If
37372 @samp{DataSeg} is specified, relocate the second segment, which
37373 conventionally contains modifiable data, to a starting address of
37374 @var{yyy}. @value{GDBN} will report an error if the object file
37375 does not contain segment information, or does not contain at least
37376 as many segments as mentioned in the reply. Extra segments are
37377 kept at fixed offsets relative to the last relocated segment.
37380 @item qP @var{mode} @var{thread-id}
37381 @cindex thread information, remote request
37382 @cindex @samp{qP} packet
37383 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37384 encoded 32 bit mode; @var{thread-id} is a thread ID
37385 (@pxref{thread-id syntax}).
37387 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37390 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37394 @cindex non-stop mode, remote request
37395 @cindex @samp{QNonStop} packet
37397 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37398 @xref{Remote Non-Stop}, for more information.
37403 The request succeeded.
37406 An error occurred. The error number @var{nn} is given as hex digits.
37409 An empty reply indicates that @samp{QNonStop} is not supported by
37413 This packet is not probed by default; the remote stub must request it,
37414 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37415 Use of this packet is controlled by the @code{set non-stop} command;
37416 @pxref{Non-Stop Mode}.
37418 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37419 @itemx QCatchSyscalls:0
37420 @cindex catch syscalls from inferior, remote request
37421 @cindex @samp{QCatchSyscalls} packet
37422 @anchor{QCatchSyscalls}
37423 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37424 catching syscalls from the inferior process.
37426 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37427 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37428 is listed, every system call should be reported.
37430 Note that if a syscall not in the list is reported, @value{GDBN} will
37431 still filter the event according to its own list from all corresponding
37432 @code{catch syscall} commands. However, it is more efficient to only
37433 report the requested syscalls.
37435 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37436 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37438 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37439 kept for the new process too. On targets where exec may affect syscall
37440 numbers, for example with exec between 32 and 64-bit processes, the
37441 client should send a new packet with the new syscall list.
37446 The request succeeded.
37449 An error occurred. @var{nn} are hex digits.
37452 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37456 Use of this packet is controlled by the @code{set remote catch-syscalls}
37457 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37458 This packet is not probed by default; the remote stub must request it,
37459 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37461 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37462 @cindex pass signals to inferior, remote request
37463 @cindex @samp{QPassSignals} packet
37464 @anchor{QPassSignals}
37465 Each listed @var{signal} should be passed directly to the inferior process.
37466 Signals are numbered identically to continue packets and stop replies
37467 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37468 strictly greater than the previous item. These signals do not need to stop
37469 the inferior, or be reported to @value{GDBN}. All other signals should be
37470 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37471 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37472 new list. This packet improves performance when using @samp{handle
37473 @var{signal} nostop noprint pass}.
37478 The request succeeded.
37481 An error occurred. The error number @var{nn} is given as hex digits.
37484 An empty reply indicates that @samp{QPassSignals} is not supported by
37488 Use of this packet is controlled by the @code{set remote pass-signals}
37489 command (@pxref{Remote Configuration, set remote pass-signals}).
37490 This packet is not probed by default; the remote stub must request it,
37491 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37493 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37494 @cindex signals the inferior may see, remote request
37495 @cindex @samp{QProgramSignals} packet
37496 @anchor{QProgramSignals}
37497 Each listed @var{signal} may be delivered to the inferior process.
37498 Others should be silently discarded.
37500 In some cases, the remote stub may need to decide whether to deliver a
37501 signal to the program or not without @value{GDBN} involvement. One
37502 example of that is while detaching --- the program's threads may have
37503 stopped for signals that haven't yet had a chance of being reported to
37504 @value{GDBN}, and so the remote stub can use the signal list specified
37505 by this packet to know whether to deliver or ignore those pending
37508 This does not influence whether to deliver a signal as requested by a
37509 resumption packet (@pxref{vCont packet}).
37511 Signals are numbered identically to continue packets and stop replies
37512 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37513 strictly greater than the previous item. Multiple
37514 @samp{QProgramSignals} packets do not combine; any earlier
37515 @samp{QProgramSignals} list is completely replaced by the new list.
37520 The request succeeded.
37523 An error occurred. The error number @var{nn} is given as hex digits.
37526 An empty reply indicates that @samp{QProgramSignals} is not supported
37530 Use of this packet is controlled by the @code{set remote program-signals}
37531 command (@pxref{Remote Configuration, set remote program-signals}).
37532 This packet is not probed by default; the remote stub must request it,
37533 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37535 @anchor{QThreadEvents}
37536 @item QThreadEvents:1
37537 @itemx QThreadEvents:0
37538 @cindex thread create/exit events, remote request
37539 @cindex @samp{QThreadEvents} packet
37541 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37542 reporting of thread create and exit events. @xref{thread create
37543 event}, for the reply specifications. For example, this is used in
37544 non-stop mode when @value{GDBN} stops a set of threads and
37545 synchronously waits for the their corresponding stop replies. Without
37546 exit events, if one of the threads exits, @value{GDBN} would hang
37547 forever not knowing that it should no longer expect a stop for that
37548 same thread. @value{GDBN} does not enable this feature unless the
37549 stub reports that it supports it by including @samp{QThreadEvents+} in
37550 its @samp{qSupported} reply.
37555 The request succeeded.
37558 An error occurred. The error number @var{nn} is given as hex digits.
37561 An empty reply indicates that @samp{QThreadEvents} is not supported by
37565 Use of this packet is controlled by the @code{set remote thread-events}
37566 command (@pxref{Remote Configuration, set remote thread-events}).
37568 @item qRcmd,@var{command}
37569 @cindex execute remote command, remote request
37570 @cindex @samp{qRcmd} packet
37571 @var{command} (hex encoded) is passed to the local interpreter for
37572 execution. Invalid commands should be reported using the output
37573 string. Before the final result packet, the target may also respond
37574 with a number of intermediate @samp{O@var{output}} console output
37575 packets. @emph{Implementors should note that providing access to a
37576 stubs's interpreter may have security implications}.
37581 A command response with no output.
37583 A command response with the hex encoded output string @var{OUTPUT}.
37585 Indicate a badly formed request.
37587 An empty reply indicates that @samp{qRcmd} is not recognized.
37590 (Note that the @code{qRcmd} packet's name is separated from the
37591 command by a @samp{,}, not a @samp{:}, contrary to the naming
37592 conventions above. Please don't use this packet as a model for new
37595 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37596 @cindex searching memory, in remote debugging
37598 @cindex @samp{qSearch:memory} packet
37600 @cindex @samp{qSearch memory} packet
37601 @anchor{qSearch memory}
37602 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37603 Both @var{address} and @var{length} are encoded in hex;
37604 @var{search-pattern} is a sequence of bytes, also hex encoded.
37609 The pattern was not found.
37611 The pattern was found at @var{address}.
37613 A badly formed request or an error was encountered while searching memory.
37615 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37618 @item QStartNoAckMode
37619 @cindex @samp{QStartNoAckMode} packet
37620 @anchor{QStartNoAckMode}
37621 Request that the remote stub disable the normal @samp{+}/@samp{-}
37622 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37627 The stub has switched to no-acknowledgment mode.
37628 @value{GDBN} acknowledges this reponse,
37629 but neither the stub nor @value{GDBN} shall send or expect further
37630 @samp{+}/@samp{-} acknowledgments in the current connection.
37632 An empty reply indicates that the stub does not support no-acknowledgment mode.
37635 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37636 @cindex supported packets, remote query
37637 @cindex features of the remote protocol
37638 @cindex @samp{qSupported} packet
37639 @anchor{qSupported}
37640 Tell the remote stub about features supported by @value{GDBN}, and
37641 query the stub for features it supports. This packet allows
37642 @value{GDBN} and the remote stub to take advantage of each others'
37643 features. @samp{qSupported} also consolidates multiple feature probes
37644 at startup, to improve @value{GDBN} performance---a single larger
37645 packet performs better than multiple smaller probe packets on
37646 high-latency links. Some features may enable behavior which must not
37647 be on by default, e.g.@: because it would confuse older clients or
37648 stubs. Other features may describe packets which could be
37649 automatically probed for, but are not. These features must be
37650 reported before @value{GDBN} will use them. This ``default
37651 unsupported'' behavior is not appropriate for all packets, but it
37652 helps to keep the initial connection time under control with new
37653 versions of @value{GDBN} which support increasing numbers of packets.
37657 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37658 The stub supports or does not support each returned @var{stubfeature},
37659 depending on the form of each @var{stubfeature} (see below for the
37662 An empty reply indicates that @samp{qSupported} is not recognized,
37663 or that no features needed to be reported to @value{GDBN}.
37666 The allowed forms for each feature (either a @var{gdbfeature} in the
37667 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37671 @item @var{name}=@var{value}
37672 The remote protocol feature @var{name} is supported, and associated
37673 with the specified @var{value}. The format of @var{value} depends
37674 on the feature, but it must not include a semicolon.
37676 The remote protocol feature @var{name} is supported, and does not
37677 need an associated value.
37679 The remote protocol feature @var{name} is not supported.
37681 The remote protocol feature @var{name} may be supported, and
37682 @value{GDBN} should auto-detect support in some other way when it is
37683 needed. This form will not be used for @var{gdbfeature} notifications,
37684 but may be used for @var{stubfeature} responses.
37687 Whenever the stub receives a @samp{qSupported} request, the
37688 supplied set of @value{GDBN} features should override any previous
37689 request. This allows @value{GDBN} to put the stub in a known
37690 state, even if the stub had previously been communicating with
37691 a different version of @value{GDBN}.
37693 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37698 This feature indicates whether @value{GDBN} supports multiprocess
37699 extensions to the remote protocol. @value{GDBN} does not use such
37700 extensions unless the stub also reports that it supports them by
37701 including @samp{multiprocess+} in its @samp{qSupported} reply.
37702 @xref{multiprocess extensions}, for details.
37705 This feature indicates that @value{GDBN} supports the XML target
37706 description. If the stub sees @samp{xmlRegisters=} with target
37707 specific strings separated by a comma, it will report register
37711 This feature indicates whether @value{GDBN} supports the
37712 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37713 instruction reply packet}).
37716 This feature indicates whether @value{GDBN} supports the swbreak stop
37717 reason in stop replies. @xref{swbreak stop reason}, for details.
37720 This feature indicates whether @value{GDBN} supports the hwbreak stop
37721 reason in stop replies. @xref{swbreak stop reason}, for details.
37724 This feature indicates whether @value{GDBN} supports fork event
37725 extensions to the remote protocol. @value{GDBN} does not use such
37726 extensions unless the stub also reports that it supports them by
37727 including @samp{fork-events+} in its @samp{qSupported} reply.
37730 This feature indicates whether @value{GDBN} supports vfork event
37731 extensions to the remote protocol. @value{GDBN} does not use such
37732 extensions unless the stub also reports that it supports them by
37733 including @samp{vfork-events+} in its @samp{qSupported} reply.
37736 This feature indicates whether @value{GDBN} supports exec event
37737 extensions to the remote protocol. @value{GDBN} does not use such
37738 extensions unless the stub also reports that it supports them by
37739 including @samp{exec-events+} in its @samp{qSupported} reply.
37741 @item vContSupported
37742 This feature indicates whether @value{GDBN} wants to know the
37743 supported actions in the reply to @samp{vCont?} packet.
37746 Stubs should ignore any unknown values for
37747 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37748 packet supports receiving packets of unlimited length (earlier
37749 versions of @value{GDBN} may reject overly long responses). Additional values
37750 for @var{gdbfeature} may be defined in the future to let the stub take
37751 advantage of new features in @value{GDBN}, e.g.@: incompatible
37752 improvements in the remote protocol---the @samp{multiprocess} feature is
37753 an example of such a feature. The stub's reply should be independent
37754 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37755 describes all the features it supports, and then the stub replies with
37756 all the features it supports.
37758 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37759 responses, as long as each response uses one of the standard forms.
37761 Some features are flags. A stub which supports a flag feature
37762 should respond with a @samp{+} form response. Other features
37763 require values, and the stub should respond with an @samp{=}
37766 Each feature has a default value, which @value{GDBN} will use if
37767 @samp{qSupported} is not available or if the feature is not mentioned
37768 in the @samp{qSupported} response. The default values are fixed; a
37769 stub is free to omit any feature responses that match the defaults.
37771 Not all features can be probed, but for those which can, the probing
37772 mechanism is useful: in some cases, a stub's internal
37773 architecture may not allow the protocol layer to know some information
37774 about the underlying target in advance. This is especially common in
37775 stubs which may be configured for multiple targets.
37777 These are the currently defined stub features and their properties:
37779 @multitable @columnfractions 0.35 0.2 0.12 0.2
37780 @c NOTE: The first row should be @headitem, but we do not yet require
37781 @c a new enough version of Texinfo (4.7) to use @headitem.
37783 @tab Value Required
37787 @item @samp{PacketSize}
37792 @item @samp{qXfer:auxv:read}
37797 @item @samp{qXfer:btrace:read}
37802 @item @samp{qXfer:btrace-conf:read}
37807 @item @samp{qXfer:exec-file:read}
37812 @item @samp{qXfer:features:read}
37817 @item @samp{qXfer:libraries:read}
37822 @item @samp{qXfer:libraries-svr4:read}
37827 @item @samp{augmented-libraries-svr4-read}
37832 @item @samp{qXfer:memory-map:read}
37837 @item @samp{qXfer:sdata:read}
37842 @item @samp{qXfer:spu:read}
37847 @item @samp{qXfer:spu:write}
37852 @item @samp{qXfer:siginfo:read}
37857 @item @samp{qXfer:siginfo:write}
37862 @item @samp{qXfer:threads:read}
37867 @item @samp{qXfer:traceframe-info:read}
37872 @item @samp{qXfer:uib:read}
37877 @item @samp{qXfer:fdpic:read}
37882 @item @samp{Qbtrace:off}
37887 @item @samp{Qbtrace:bts}
37892 @item @samp{Qbtrace:pt}
37897 @item @samp{Qbtrace-conf:bts:size}
37902 @item @samp{Qbtrace-conf:pt:size}
37907 @item @samp{QNonStop}
37912 @item @samp{QCatchSyscalls}
37917 @item @samp{QPassSignals}
37922 @item @samp{QStartNoAckMode}
37927 @item @samp{multiprocess}
37932 @item @samp{ConditionalBreakpoints}
37937 @item @samp{ConditionalTracepoints}
37942 @item @samp{ReverseContinue}
37947 @item @samp{ReverseStep}
37952 @item @samp{TracepointSource}
37957 @item @samp{QAgent}
37962 @item @samp{QAllow}
37967 @item @samp{QDisableRandomization}
37972 @item @samp{EnableDisableTracepoints}
37977 @item @samp{QTBuffer:size}
37982 @item @samp{tracenz}
37987 @item @samp{BreakpointCommands}
37992 @item @samp{swbreak}
37997 @item @samp{hwbreak}
38002 @item @samp{fork-events}
38007 @item @samp{vfork-events}
38012 @item @samp{exec-events}
38017 @item @samp{QThreadEvents}
38022 @item @samp{no-resumed}
38029 These are the currently defined stub features, in more detail:
38032 @cindex packet size, remote protocol
38033 @item PacketSize=@var{bytes}
38034 The remote stub can accept packets up to at least @var{bytes} in
38035 length. @value{GDBN} will send packets up to this size for bulk
38036 transfers, and will never send larger packets. This is a limit on the
38037 data characters in the packet, including the frame and checksum.
38038 There is no trailing NUL byte in a remote protocol packet; if the stub
38039 stores packets in a NUL-terminated format, it should allow an extra
38040 byte in its buffer for the NUL. If this stub feature is not supported,
38041 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38043 @item qXfer:auxv:read
38044 The remote stub understands the @samp{qXfer:auxv:read} packet
38045 (@pxref{qXfer auxiliary vector read}).
38047 @item qXfer:btrace:read
38048 The remote stub understands the @samp{qXfer:btrace:read}
38049 packet (@pxref{qXfer btrace read}).
38051 @item qXfer:btrace-conf:read
38052 The remote stub understands the @samp{qXfer:btrace-conf:read}
38053 packet (@pxref{qXfer btrace-conf read}).
38055 @item qXfer:exec-file:read
38056 The remote stub understands the @samp{qXfer:exec-file:read} packet
38057 (@pxref{qXfer executable filename read}).
38059 @item qXfer:features:read
38060 The remote stub understands the @samp{qXfer:features:read} packet
38061 (@pxref{qXfer target description read}).
38063 @item qXfer:libraries:read
38064 The remote stub understands the @samp{qXfer:libraries:read} packet
38065 (@pxref{qXfer library list read}).
38067 @item qXfer:libraries-svr4:read
38068 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38069 (@pxref{qXfer svr4 library list read}).
38071 @item augmented-libraries-svr4-read
38072 The remote stub understands the augmented form of the
38073 @samp{qXfer:libraries-svr4:read} packet
38074 (@pxref{qXfer svr4 library list read}).
38076 @item qXfer:memory-map:read
38077 The remote stub understands the @samp{qXfer:memory-map:read} packet
38078 (@pxref{qXfer memory map read}).
38080 @item qXfer:sdata:read
38081 The remote stub understands the @samp{qXfer:sdata:read} packet
38082 (@pxref{qXfer sdata read}).
38084 @item qXfer:spu:read
38085 The remote stub understands the @samp{qXfer:spu:read} packet
38086 (@pxref{qXfer spu read}).
38088 @item qXfer:spu:write
38089 The remote stub understands the @samp{qXfer:spu:write} packet
38090 (@pxref{qXfer spu write}).
38092 @item qXfer:siginfo:read
38093 The remote stub understands the @samp{qXfer:siginfo:read} packet
38094 (@pxref{qXfer siginfo read}).
38096 @item qXfer:siginfo:write
38097 The remote stub understands the @samp{qXfer:siginfo:write} packet
38098 (@pxref{qXfer siginfo write}).
38100 @item qXfer:threads:read
38101 The remote stub understands the @samp{qXfer:threads:read} packet
38102 (@pxref{qXfer threads read}).
38104 @item qXfer:traceframe-info:read
38105 The remote stub understands the @samp{qXfer:traceframe-info:read}
38106 packet (@pxref{qXfer traceframe info read}).
38108 @item qXfer:uib:read
38109 The remote stub understands the @samp{qXfer:uib:read}
38110 packet (@pxref{qXfer unwind info block}).
38112 @item qXfer:fdpic:read
38113 The remote stub understands the @samp{qXfer:fdpic:read}
38114 packet (@pxref{qXfer fdpic loadmap read}).
38117 The remote stub understands the @samp{QNonStop} packet
38118 (@pxref{QNonStop}).
38120 @item QCatchSyscalls
38121 The remote stub understands the @samp{QCatchSyscalls} packet
38122 (@pxref{QCatchSyscalls}).
38125 The remote stub understands the @samp{QPassSignals} packet
38126 (@pxref{QPassSignals}).
38128 @item QStartNoAckMode
38129 The remote stub understands the @samp{QStartNoAckMode} packet and
38130 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38133 @anchor{multiprocess extensions}
38134 @cindex multiprocess extensions, in remote protocol
38135 The remote stub understands the multiprocess extensions to the remote
38136 protocol syntax. The multiprocess extensions affect the syntax of
38137 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38138 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38139 replies. Note that reporting this feature indicates support for the
38140 syntactic extensions only, not that the stub necessarily supports
38141 debugging of more than one process at a time. The stub must not use
38142 multiprocess extensions in packet replies unless @value{GDBN} has also
38143 indicated it supports them in its @samp{qSupported} request.
38145 @item qXfer:osdata:read
38146 The remote stub understands the @samp{qXfer:osdata:read} packet
38147 ((@pxref{qXfer osdata read}).
38149 @item ConditionalBreakpoints
38150 The target accepts and implements evaluation of conditional expressions
38151 defined for breakpoints. The target will only report breakpoint triggers
38152 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38154 @item ConditionalTracepoints
38155 The remote stub accepts and implements conditional expressions defined
38156 for tracepoints (@pxref{Tracepoint Conditions}).
38158 @item ReverseContinue
38159 The remote stub accepts and implements the reverse continue packet
38163 The remote stub accepts and implements the reverse step packet
38166 @item TracepointSource
38167 The remote stub understands the @samp{QTDPsrc} packet that supplies
38168 the source form of tracepoint definitions.
38171 The remote stub understands the @samp{QAgent} packet.
38174 The remote stub understands the @samp{QAllow} packet.
38176 @item QDisableRandomization
38177 The remote stub understands the @samp{QDisableRandomization} packet.
38179 @item StaticTracepoint
38180 @cindex static tracepoints, in remote protocol
38181 The remote stub supports static tracepoints.
38183 @item InstallInTrace
38184 @anchor{install tracepoint in tracing}
38185 The remote stub supports installing tracepoint in tracing.
38187 @item EnableDisableTracepoints
38188 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38189 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38190 to be enabled and disabled while a trace experiment is running.
38192 @item QTBuffer:size
38193 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38194 packet that allows to change the size of the trace buffer.
38197 @cindex string tracing, in remote protocol
38198 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38199 See @ref{Bytecode Descriptions} for details about the bytecode.
38201 @item BreakpointCommands
38202 @cindex breakpoint commands, in remote protocol
38203 The remote stub supports running a breakpoint's command list itself,
38204 rather than reporting the hit to @value{GDBN}.
38207 The remote stub understands the @samp{Qbtrace:off} packet.
38210 The remote stub understands the @samp{Qbtrace:bts} packet.
38213 The remote stub understands the @samp{Qbtrace:pt} packet.
38215 @item Qbtrace-conf:bts:size
38216 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38218 @item Qbtrace-conf:pt:size
38219 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38222 The remote stub reports the @samp{swbreak} stop reason for memory
38226 The remote stub reports the @samp{hwbreak} stop reason for hardware
38230 The remote stub reports the @samp{fork} stop reason for fork events.
38233 The remote stub reports the @samp{vfork} stop reason for vfork events
38234 and vforkdone events.
38237 The remote stub reports the @samp{exec} stop reason for exec events.
38239 @item vContSupported
38240 The remote stub reports the supported actions in the reply to
38241 @samp{vCont?} packet.
38243 @item QThreadEvents
38244 The remote stub understands the @samp{QThreadEvents} packet.
38247 The remote stub reports the @samp{N} stop reply.
38252 @cindex symbol lookup, remote request
38253 @cindex @samp{qSymbol} packet
38254 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38255 requests. Accept requests from the target for the values of symbols.
38260 The target does not need to look up any (more) symbols.
38261 @item qSymbol:@var{sym_name}
38262 The target requests the value of symbol @var{sym_name} (hex encoded).
38263 @value{GDBN} may provide the value by using the
38264 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38268 @item qSymbol:@var{sym_value}:@var{sym_name}
38269 Set the value of @var{sym_name} to @var{sym_value}.
38271 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38272 target has previously requested.
38274 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38275 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38281 The target does not need to look up any (more) symbols.
38282 @item qSymbol:@var{sym_name}
38283 The target requests the value of a new symbol @var{sym_name} (hex
38284 encoded). @value{GDBN} will continue to supply the values of symbols
38285 (if available), until the target ceases to request them.
38290 @itemx QTDisconnected
38297 @itemx qTMinFTPILen
38299 @xref{Tracepoint Packets}.
38301 @item qThreadExtraInfo,@var{thread-id}
38302 @cindex thread attributes info, remote request
38303 @cindex @samp{qThreadExtraInfo} packet
38304 Obtain from the target OS a printable string description of thread
38305 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38306 for the forms of @var{thread-id}. This
38307 string may contain anything that the target OS thinks is interesting
38308 for @value{GDBN} to tell the user about the thread. The string is
38309 displayed in @value{GDBN}'s @code{info threads} display. Some
38310 examples of possible thread extra info strings are @samp{Runnable}, or
38311 @samp{Blocked on Mutex}.
38315 @item @var{XX}@dots{}
38316 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38317 comprising the printable string containing the extra information about
38318 the thread's attributes.
38321 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38322 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38323 conventions above. Please don't use this packet as a model for new
38342 @xref{Tracepoint Packets}.
38344 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38345 @cindex read special object, remote request
38346 @cindex @samp{qXfer} packet
38347 @anchor{qXfer read}
38348 Read uninterpreted bytes from the target's special data area
38349 identified by the keyword @var{object}. Request @var{length} bytes
38350 starting at @var{offset} bytes into the data. The content and
38351 encoding of @var{annex} is specific to @var{object}; it can supply
38352 additional details about what data to access.
38357 Data @var{data} (@pxref{Binary Data}) has been read from the
38358 target. There may be more data at a higher address (although
38359 it is permitted to return @samp{m} even for the last valid
38360 block of data, as long as at least one byte of data was read).
38361 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38365 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38366 There is no more data to be read. It is possible for @var{data} to
38367 have fewer bytes than the @var{length} in the request.
38370 The @var{offset} in the request is at the end of the data.
38371 There is no more data to be read.
38374 The request was malformed, or @var{annex} was invalid.
38377 The offset was invalid, or there was an error encountered reading the data.
38378 The @var{nn} part is a hex-encoded @code{errno} value.
38381 An empty reply indicates the @var{object} string was not recognized by
38382 the stub, or that the object does not support reading.
38385 Here are the specific requests of this form defined so far. All the
38386 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38387 formats, listed above.
38390 @item qXfer:auxv:read::@var{offset},@var{length}
38391 @anchor{qXfer auxiliary vector read}
38392 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38393 auxiliary vector}. Note @var{annex} must be empty.
38395 This packet is not probed by default; the remote stub must request it,
38396 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38398 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38399 @anchor{qXfer btrace read}
38401 Return a description of the current branch trace.
38402 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38403 packet may have one of the following values:
38407 Returns all available branch trace.
38410 Returns all available branch trace if the branch trace changed since
38411 the last read request.
38414 Returns the new branch trace since the last read request. Adds a new
38415 block to the end of the trace that begins at zero and ends at the source
38416 location of the first branch in the trace buffer. This extra block is
38417 used to stitch traces together.
38419 If the trace buffer overflowed, returns an error indicating the overflow.
38422 This packet is not probed by default; the remote stub must request it
38423 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38425 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38426 @anchor{qXfer btrace-conf read}
38428 Return a description of the current branch trace configuration.
38429 @xref{Branch Trace Configuration Format}.
38431 This packet is not probed by default; the remote stub must request it
38432 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38434 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38435 @anchor{qXfer executable filename read}
38436 Return the full absolute name of the file that was executed to create
38437 a process running on the remote system. The annex specifies the
38438 numeric process ID of the process to query, encoded as a hexadecimal
38439 number. If the annex part is empty the remote stub should return the
38440 filename corresponding to the currently executing process.
38442 This packet is not probed by default; the remote stub must request it,
38443 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38445 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38446 @anchor{qXfer target description read}
38447 Access the @dfn{target description}. @xref{Target Descriptions}. The
38448 annex specifies which XML document to access. The main description is
38449 always loaded from the @samp{target.xml} annex.
38451 This packet is not probed by default; the remote stub must request it,
38452 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38454 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38455 @anchor{qXfer library list read}
38456 Access the target's list of loaded libraries. @xref{Library List Format}.
38457 The annex part of the generic @samp{qXfer} packet must be empty
38458 (@pxref{qXfer read}).
38460 Targets which maintain a list of libraries in the program's memory do
38461 not need to implement this packet; it is designed for platforms where
38462 the operating system manages the list of loaded libraries.
38464 This packet is not probed by default; the remote stub must request it,
38465 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38467 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38468 @anchor{qXfer svr4 library list read}
38469 Access the target's list of loaded libraries when the target is an SVR4
38470 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38471 of the generic @samp{qXfer} packet must be empty unless the remote
38472 stub indicated it supports the augmented form of this packet
38473 by supplying an appropriate @samp{qSupported} response
38474 (@pxref{qXfer read}, @ref{qSupported}).
38476 This packet is optional for better performance on SVR4 targets.
38477 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38479 This packet is not probed by default; the remote stub must request it,
38480 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38482 If the remote stub indicates it supports the augmented form of this
38483 packet then the annex part of the generic @samp{qXfer} packet may
38484 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38485 arguments. The currently supported arguments are:
38488 @item start=@var{address}
38489 A hexadecimal number specifying the address of the @samp{struct
38490 link_map} to start reading the library list from. If unset or zero
38491 then the first @samp{struct link_map} in the library list will be
38492 chosen as the starting point.
38494 @item prev=@var{address}
38495 A hexadecimal number specifying the address of the @samp{struct
38496 link_map} immediately preceding the @samp{struct link_map}
38497 specified by the @samp{start} argument. If unset or zero then
38498 the remote stub will expect that no @samp{struct link_map}
38499 exists prior to the starting point.
38503 Arguments that are not understood by the remote stub will be silently
38506 @item qXfer:memory-map:read::@var{offset},@var{length}
38507 @anchor{qXfer memory map read}
38508 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38509 annex part of the generic @samp{qXfer} packet must be empty
38510 (@pxref{qXfer read}).
38512 This packet is not probed by default; the remote stub must request it,
38513 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38515 @item qXfer:sdata:read::@var{offset},@var{length}
38516 @anchor{qXfer sdata read}
38518 Read contents of the extra collected static tracepoint marker
38519 information. The annex part of the generic @samp{qXfer} packet must
38520 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38523 This packet is not probed by default; the remote stub must request it,
38524 by supplying an appropriate @samp{qSupported} response
38525 (@pxref{qSupported}).
38527 @item qXfer:siginfo:read::@var{offset},@var{length}
38528 @anchor{qXfer siginfo read}
38529 Read contents of the extra signal information on the target
38530 system. The annex part of the generic @samp{qXfer} packet must be
38531 empty (@pxref{qXfer read}).
38533 This packet is not probed by default; the remote stub must request it,
38534 by supplying an appropriate @samp{qSupported} response
38535 (@pxref{qSupported}).
38537 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38538 @anchor{qXfer spu read}
38539 Read contents of an @code{spufs} file on the target system. The
38540 annex specifies which file to read; it must be of the form
38541 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38542 in the target process, and @var{name} identifes the @code{spufs} file
38543 in that context to be accessed.
38545 This packet is not probed by default; the remote stub must request it,
38546 by supplying an appropriate @samp{qSupported} response
38547 (@pxref{qSupported}).
38549 @item qXfer:threads:read::@var{offset},@var{length}
38550 @anchor{qXfer threads read}
38551 Access the list of threads on target. @xref{Thread List Format}. The
38552 annex part of the generic @samp{qXfer} packet must be empty
38553 (@pxref{qXfer read}).
38555 This packet is not probed by default; the remote stub must request it,
38556 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38558 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38559 @anchor{qXfer traceframe info read}
38561 Return a description of the current traceframe's contents.
38562 @xref{Traceframe Info Format}. The annex part of the generic
38563 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38565 This packet is not probed by default; the remote stub must request it,
38566 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38568 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38569 @anchor{qXfer unwind info block}
38571 Return the unwind information block for @var{pc}. This packet is used
38572 on OpenVMS/ia64 to ask the kernel unwind information.
38574 This packet is not probed by default.
38576 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38577 @anchor{qXfer fdpic loadmap read}
38578 Read contents of @code{loadmap}s on the target system. The
38579 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38580 executable @code{loadmap} or interpreter @code{loadmap} to read.
38582 This packet is not probed by default; the remote stub must request it,
38583 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38585 @item qXfer:osdata:read::@var{offset},@var{length}
38586 @anchor{qXfer osdata read}
38587 Access the target's @dfn{operating system information}.
38588 @xref{Operating System Information}.
38592 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38593 @cindex write data into object, remote request
38594 @anchor{qXfer write}
38595 Write uninterpreted bytes into the target's special data area
38596 identified by the keyword @var{object}, starting at @var{offset} bytes
38597 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38598 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38599 is specific to @var{object}; it can supply additional details about what data
38605 @var{nn} (hex encoded) is the number of bytes written.
38606 This may be fewer bytes than supplied in the request.
38609 The request was malformed, or @var{annex} was invalid.
38612 The offset was invalid, or there was an error encountered writing the data.
38613 The @var{nn} part is a hex-encoded @code{errno} value.
38616 An empty reply indicates the @var{object} string was not
38617 recognized by the stub, or that the object does not support writing.
38620 Here are the specific requests of this form defined so far. All the
38621 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38622 formats, listed above.
38625 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38626 @anchor{qXfer siginfo write}
38627 Write @var{data} to the extra signal information on the target system.
38628 The annex part of the generic @samp{qXfer} packet must be
38629 empty (@pxref{qXfer write}).
38631 This packet is not probed by default; the remote stub must request it,
38632 by supplying an appropriate @samp{qSupported} response
38633 (@pxref{qSupported}).
38635 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38636 @anchor{qXfer spu write}
38637 Write @var{data} to an @code{spufs} file on the target system. The
38638 annex specifies which file to write; it must be of the form
38639 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38640 in the target process, and @var{name} identifes the @code{spufs} file
38641 in that context to be accessed.
38643 This packet is not probed by default; the remote stub must request it,
38644 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38647 @item qXfer:@var{object}:@var{operation}:@dots{}
38648 Requests of this form may be added in the future. When a stub does
38649 not recognize the @var{object} keyword, or its support for
38650 @var{object} does not recognize the @var{operation} keyword, the stub
38651 must respond with an empty packet.
38653 @item qAttached:@var{pid}
38654 @cindex query attached, remote request
38655 @cindex @samp{qAttached} packet
38656 Return an indication of whether the remote server attached to an
38657 existing process or created a new process. When the multiprocess
38658 protocol extensions are supported (@pxref{multiprocess extensions}),
38659 @var{pid} is an integer in hexadecimal format identifying the target
38660 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38661 the query packet will be simplified as @samp{qAttached}.
38663 This query is used, for example, to know whether the remote process
38664 should be detached or killed when a @value{GDBN} session is ended with
38665 the @code{quit} command.
38670 The remote server attached to an existing process.
38672 The remote server created a new process.
38674 A badly formed request or an error was encountered.
38678 Enable branch tracing for the current thread using Branch Trace Store.
38683 Branch tracing has been enabled.
38685 A badly formed request or an error was encountered.
38689 Enable branch tracing for the current thread using Intel Processor Trace.
38694 Branch tracing has been enabled.
38696 A badly formed request or an error was encountered.
38700 Disable branch tracing for the current thread.
38705 Branch tracing has been disabled.
38707 A badly formed request or an error was encountered.
38710 @item Qbtrace-conf:bts:size=@var{value}
38711 Set the requested ring buffer size for new threads that use the
38712 btrace recording method in bts format.
38717 The ring buffer size has been set.
38719 A badly formed request or an error was encountered.
38722 @item Qbtrace-conf:pt:size=@var{value}
38723 Set the requested ring buffer size for new threads that use the
38724 btrace recording method in pt format.
38729 The ring buffer size has been set.
38731 A badly formed request or an error was encountered.
38736 @node Architecture-Specific Protocol Details
38737 @section Architecture-Specific Protocol Details
38739 This section describes how the remote protocol is applied to specific
38740 target architectures. Also see @ref{Standard Target Features}, for
38741 details of XML target descriptions for each architecture.
38744 * ARM-Specific Protocol Details::
38745 * MIPS-Specific Protocol Details::
38748 @node ARM-Specific Protocol Details
38749 @subsection @acronym{ARM}-specific Protocol Details
38752 * ARM Breakpoint Kinds::
38755 @node ARM Breakpoint Kinds
38756 @subsubsection @acronym{ARM} Breakpoint Kinds
38757 @cindex breakpoint kinds, @acronym{ARM}
38759 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38764 16-bit Thumb mode breakpoint.
38767 32-bit Thumb mode (Thumb-2) breakpoint.
38770 32-bit @acronym{ARM} mode breakpoint.
38774 @node MIPS-Specific Protocol Details
38775 @subsection @acronym{MIPS}-specific Protocol Details
38778 * MIPS Register packet Format::
38779 * MIPS Breakpoint Kinds::
38782 @node MIPS Register packet Format
38783 @subsubsection @acronym{MIPS} Register Packet Format
38784 @cindex register packet format, @acronym{MIPS}
38786 The following @code{g}/@code{G} packets have previously been defined.
38787 In the below, some thirty-two bit registers are transferred as
38788 sixty-four bits. Those registers should be zero/sign extended (which?)
38789 to fill the space allocated. Register bytes are transferred in target
38790 byte order. The two nibbles within a register byte are transferred
38791 most-significant -- least-significant.
38796 All registers are transferred as thirty-two bit quantities in the order:
38797 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38798 registers; fsr; fir; fp.
38801 All registers are transferred as sixty-four bit quantities (including
38802 thirty-two bit registers such as @code{sr}). The ordering is the same
38807 @node MIPS Breakpoint Kinds
38808 @subsubsection @acronym{MIPS} Breakpoint Kinds
38809 @cindex breakpoint kinds, @acronym{MIPS}
38811 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38816 16-bit @acronym{MIPS16} mode breakpoint.
38819 16-bit @acronym{microMIPS} mode breakpoint.
38822 32-bit standard @acronym{MIPS} mode breakpoint.
38825 32-bit @acronym{microMIPS} mode breakpoint.
38829 @node Tracepoint Packets
38830 @section Tracepoint Packets
38831 @cindex tracepoint packets
38832 @cindex packets, tracepoint
38834 Here we describe the packets @value{GDBN} uses to implement
38835 tracepoints (@pxref{Tracepoints}).
38839 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38840 @cindex @samp{QTDP} packet
38841 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38842 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38843 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38844 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38845 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38846 the number of bytes that the target should copy elsewhere to make room
38847 for the tracepoint. If an @samp{X} is present, it introduces a
38848 tracepoint condition, which consists of a hexadecimal length, followed
38849 by a comma and hex-encoded bytes, in a manner similar to action
38850 encodings as described below. If the trailing @samp{-} is present,
38851 further @samp{QTDP} packets will follow to specify this tracepoint's
38857 The packet was understood and carried out.
38859 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38861 The packet was not recognized.
38864 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38865 Define actions to be taken when a tracepoint is hit. The @var{n} and
38866 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38867 this tracepoint. This packet may only be sent immediately after
38868 another @samp{QTDP} packet that ended with a @samp{-}. If the
38869 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38870 specifying more actions for this tracepoint.
38872 In the series of action packets for a given tracepoint, at most one
38873 can have an @samp{S} before its first @var{action}. If such a packet
38874 is sent, it and the following packets define ``while-stepping''
38875 actions. Any prior packets define ordinary actions --- that is, those
38876 taken when the tracepoint is first hit. If no action packet has an
38877 @samp{S}, then all the packets in the series specify ordinary
38878 tracepoint actions.
38880 The @samp{@var{action}@dots{}} portion of the packet is a series of
38881 actions, concatenated without separators. Each action has one of the
38887 Collect the registers whose bits are set in @var{mask},
38888 a hexadecimal number whose @var{i}'th bit is set if register number
38889 @var{i} should be collected. (The least significant bit is numbered
38890 zero.) Note that @var{mask} may be any number of digits long; it may
38891 not fit in a 32-bit word.
38893 @item M @var{basereg},@var{offset},@var{len}
38894 Collect @var{len} bytes of memory starting at the address in register
38895 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38896 @samp{-1}, then the range has a fixed address: @var{offset} is the
38897 address of the lowest byte to collect. The @var{basereg},
38898 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38899 values (the @samp{-1} value for @var{basereg} is a special case).
38901 @item X @var{len},@var{expr}
38902 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38903 it directs. The agent expression @var{expr} is as described in
38904 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38905 two-digit hex number in the packet; @var{len} is the number of bytes
38906 in the expression (and thus one-half the number of hex digits in the
38911 Any number of actions may be packed together in a single @samp{QTDP}
38912 packet, as long as the packet does not exceed the maximum packet
38913 length (400 bytes, for many stubs). There may be only one @samp{R}
38914 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38915 actions. Any registers referred to by @samp{M} and @samp{X} actions
38916 must be collected by a preceding @samp{R} action. (The
38917 ``while-stepping'' actions are treated as if they were attached to a
38918 separate tracepoint, as far as these restrictions are concerned.)
38923 The packet was understood and carried out.
38925 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38927 The packet was not recognized.
38930 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38931 @cindex @samp{QTDPsrc} packet
38932 Specify a source string of tracepoint @var{n} at address @var{addr}.
38933 This is useful to get accurate reproduction of the tracepoints
38934 originally downloaded at the beginning of the trace run. The @var{type}
38935 is the name of the tracepoint part, such as @samp{cond} for the
38936 tracepoint's conditional expression (see below for a list of types), while
38937 @var{bytes} is the string, encoded in hexadecimal.
38939 @var{start} is the offset of the @var{bytes} within the overall source
38940 string, while @var{slen} is the total length of the source string.
38941 This is intended for handling source strings that are longer than will
38942 fit in a single packet.
38943 @c Add detailed example when this info is moved into a dedicated
38944 @c tracepoint descriptions section.
38946 The available string types are @samp{at} for the location,
38947 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38948 @value{GDBN} sends a separate packet for each command in the action
38949 list, in the same order in which the commands are stored in the list.
38951 The target does not need to do anything with source strings except
38952 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38955 Although this packet is optional, and @value{GDBN} will only send it
38956 if the target replies with @samp{TracepointSource} @xref{General
38957 Query Packets}, it makes both disconnected tracing and trace files
38958 much easier to use. Otherwise the user must be careful that the
38959 tracepoints in effect while looking at trace frames are identical to
38960 the ones in effect during the trace run; even a small discrepancy
38961 could cause @samp{tdump} not to work, or a particular trace frame not
38964 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38965 @cindex define trace state variable, remote request
38966 @cindex @samp{QTDV} packet
38967 Create a new trace state variable, number @var{n}, with an initial
38968 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38969 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38970 the option of not using this packet for initial values of zero; the
38971 target should simply create the trace state variables as they are
38972 mentioned in expressions. The value @var{builtin} should be 1 (one)
38973 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38974 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38975 @samp{qTsV} packet had it set. The contents of @var{name} is the
38976 hex-encoded name (without the leading @samp{$}) of the trace state
38979 @item QTFrame:@var{n}
38980 @cindex @samp{QTFrame} packet
38981 Select the @var{n}'th tracepoint frame from the buffer, and use the
38982 register and memory contents recorded there to answer subsequent
38983 request packets from @value{GDBN}.
38985 A successful reply from the stub indicates that the stub has found the
38986 requested frame. The response is a series of parts, concatenated
38987 without separators, describing the frame we selected. Each part has
38988 one of the following forms:
38992 The selected frame is number @var{n} in the trace frame buffer;
38993 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38994 was no frame matching the criteria in the request packet.
38997 The selected trace frame records a hit of tracepoint number @var{t};
38998 @var{t} is a hexadecimal number.
39002 @item QTFrame:pc:@var{addr}
39003 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39004 currently selected frame whose PC is @var{addr};
39005 @var{addr} is a hexadecimal number.
39007 @item QTFrame:tdp:@var{t}
39008 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39009 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39010 is a hexadecimal number.
39012 @item QTFrame:range:@var{start}:@var{end}
39013 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39014 currently selected frame whose PC is between @var{start} (inclusive)
39015 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39018 @item QTFrame:outside:@var{start}:@var{end}
39019 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39020 frame @emph{outside} the given range of addresses (exclusive).
39023 @cindex @samp{qTMinFTPILen} packet
39024 This packet requests the minimum length of instruction at which a fast
39025 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39026 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39027 it depends on the target system being able to create trampolines in
39028 the first 64K of memory, which might or might not be possible for that
39029 system. So the reply to this packet will be 4 if it is able to
39036 The minimum instruction length is currently unknown.
39038 The minimum instruction length is @var{length}, where @var{length}
39039 is a hexadecimal number greater or equal to 1. A reply
39040 of 1 means that a fast tracepoint may be placed on any instruction
39041 regardless of size.
39043 An error has occurred.
39045 An empty reply indicates that the request is not supported by the stub.
39049 @cindex @samp{QTStart} packet
39050 Begin the tracepoint experiment. Begin collecting data from
39051 tracepoint hits in the trace frame buffer. This packet supports the
39052 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39053 instruction reply packet}).
39056 @cindex @samp{QTStop} packet
39057 End the tracepoint experiment. Stop collecting trace frames.
39059 @item QTEnable:@var{n}:@var{addr}
39061 @cindex @samp{QTEnable} packet
39062 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39063 experiment. If the tracepoint was previously disabled, then collection
39064 of data from it will resume.
39066 @item QTDisable:@var{n}:@var{addr}
39068 @cindex @samp{QTDisable} packet
39069 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39070 experiment. No more data will be collected from the tracepoint unless
39071 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39074 @cindex @samp{QTinit} packet
39075 Clear the table of tracepoints, and empty the trace frame buffer.
39077 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39078 @cindex @samp{QTro} packet
39079 Establish the given ranges of memory as ``transparent''. The stub
39080 will answer requests for these ranges from memory's current contents,
39081 if they were not collected as part of the tracepoint hit.
39083 @value{GDBN} uses this to mark read-only regions of memory, like those
39084 containing program code. Since these areas never change, they should
39085 still have the same contents they did when the tracepoint was hit, so
39086 there's no reason for the stub to refuse to provide their contents.
39088 @item QTDisconnected:@var{value}
39089 @cindex @samp{QTDisconnected} packet
39090 Set the choice to what to do with the tracing run when @value{GDBN}
39091 disconnects from the target. A @var{value} of 1 directs the target to
39092 continue the tracing run, while 0 tells the target to stop tracing if
39093 @value{GDBN} is no longer in the picture.
39096 @cindex @samp{qTStatus} packet
39097 Ask the stub if there is a trace experiment running right now.
39099 The reply has the form:
39103 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39104 @var{running} is a single digit @code{1} if the trace is presently
39105 running, or @code{0} if not. It is followed by semicolon-separated
39106 optional fields that an agent may use to report additional status.
39110 If the trace is not running, the agent may report any of several
39111 explanations as one of the optional fields:
39116 No trace has been run yet.
39118 @item tstop[:@var{text}]:0
39119 The trace was stopped by a user-originated stop command. The optional
39120 @var{text} field is a user-supplied string supplied as part of the
39121 stop command (for instance, an explanation of why the trace was
39122 stopped manually). It is hex-encoded.
39125 The trace stopped because the trace buffer filled up.
39127 @item tdisconnected:0
39128 The trace stopped because @value{GDBN} disconnected from the target.
39130 @item tpasscount:@var{tpnum}
39131 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39133 @item terror:@var{text}:@var{tpnum}
39134 The trace stopped because tracepoint @var{tpnum} had an error. The
39135 string @var{text} is available to describe the nature of the error
39136 (for instance, a divide by zero in the condition expression); it
39140 The trace stopped for some other reason.
39144 Additional optional fields supply statistical and other information.
39145 Although not required, they are extremely useful for users monitoring
39146 the progress of a trace run. If a trace has stopped, and these
39147 numbers are reported, they must reflect the state of the just-stopped
39152 @item tframes:@var{n}
39153 The number of trace frames in the buffer.
39155 @item tcreated:@var{n}
39156 The total number of trace frames created during the run. This may
39157 be larger than the trace frame count, if the buffer is circular.
39159 @item tsize:@var{n}
39160 The total size of the trace buffer, in bytes.
39162 @item tfree:@var{n}
39163 The number of bytes still unused in the buffer.
39165 @item circular:@var{n}
39166 The value of the circular trace buffer flag. @code{1} means that the
39167 trace buffer is circular and old trace frames will be discarded if
39168 necessary to make room, @code{0} means that the trace buffer is linear
39171 @item disconn:@var{n}
39172 The value of the disconnected tracing flag. @code{1} means that
39173 tracing will continue after @value{GDBN} disconnects, @code{0} means
39174 that the trace run will stop.
39178 @item qTP:@var{tp}:@var{addr}
39179 @cindex tracepoint status, remote request
39180 @cindex @samp{qTP} packet
39181 Ask the stub for the current state of tracepoint number @var{tp} at
39182 address @var{addr}.
39186 @item V@var{hits}:@var{usage}
39187 The tracepoint has been hit @var{hits} times so far during the trace
39188 run, and accounts for @var{usage} in the trace buffer. Note that
39189 @code{while-stepping} steps are not counted as separate hits, but the
39190 steps' space consumption is added into the usage number.
39194 @item qTV:@var{var}
39195 @cindex trace state variable value, remote request
39196 @cindex @samp{qTV} packet
39197 Ask the stub for the value of the trace state variable number @var{var}.
39202 The value of the variable is @var{value}. This will be the current
39203 value of the variable if the user is examining a running target, or a
39204 saved value if the variable was collected in the trace frame that the
39205 user is looking at. Note that multiple requests may result in
39206 different reply values, such as when requesting values while the
39207 program is running.
39210 The value of the variable is unknown. This would occur, for example,
39211 if the user is examining a trace frame in which the requested variable
39216 @cindex @samp{qTfP} packet
39218 @cindex @samp{qTsP} packet
39219 These packets request data about tracepoints that are being used by
39220 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39221 of data, and multiple @code{qTsP} to get additional pieces. Replies
39222 to these packets generally take the form of the @code{QTDP} packets
39223 that define tracepoints. (FIXME add detailed syntax)
39226 @cindex @samp{qTfV} packet
39228 @cindex @samp{qTsV} packet
39229 These packets request data about trace state variables that are on the
39230 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39231 and multiple @code{qTsV} to get additional variables. Replies to
39232 these packets follow the syntax of the @code{QTDV} packets that define
39233 trace state variables.
39239 @cindex @samp{qTfSTM} packet
39240 @cindex @samp{qTsSTM} packet
39241 These packets request data about static tracepoint markers that exist
39242 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39243 first piece of data, and multiple @code{qTsSTM} to get additional
39244 pieces. Replies to these packets take the following form:
39248 @item m @var{address}:@var{id}:@var{extra}
39250 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39251 a comma-separated list of markers
39253 (lower case letter @samp{L}) denotes end of list.
39255 An error occurred. The error number @var{nn} is given as hex digits.
39257 An empty reply indicates that the request is not supported by the
39261 The @var{address} is encoded in hex;
39262 @var{id} and @var{extra} are strings encoded in hex.
39264 In response to each query, the target will reply with a list of one or
39265 more markers, separated by commas. @value{GDBN} will respond to each
39266 reply with a request for more markers (using the @samp{qs} form of the
39267 query), until the target responds with @samp{l} (lower-case ell, for
39270 @item qTSTMat:@var{address}
39272 @cindex @samp{qTSTMat} packet
39273 This packets requests data about static tracepoint markers in the
39274 target program at @var{address}. Replies to this packet follow the
39275 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39276 tracepoint markers.
39278 @item QTSave:@var{filename}
39279 @cindex @samp{QTSave} packet
39280 This packet directs the target to save trace data to the file name
39281 @var{filename} in the target's filesystem. The @var{filename} is encoded
39282 as a hex string; the interpretation of the file name (relative vs
39283 absolute, wild cards, etc) is up to the target.
39285 @item qTBuffer:@var{offset},@var{len}
39286 @cindex @samp{qTBuffer} packet
39287 Return up to @var{len} bytes of the current contents of trace buffer,
39288 starting at @var{offset}. The trace buffer is treated as if it were
39289 a contiguous collection of traceframes, as per the trace file format.
39290 The reply consists as many hex-encoded bytes as the target can deliver
39291 in a packet; it is not an error to return fewer than were asked for.
39292 A reply consisting of just @code{l} indicates that no bytes are
39295 @item QTBuffer:circular:@var{value}
39296 This packet directs the target to use a circular trace buffer if
39297 @var{value} is 1, or a linear buffer if the value is 0.
39299 @item QTBuffer:size:@var{size}
39300 @anchor{QTBuffer-size}
39301 @cindex @samp{QTBuffer size} packet
39302 This packet directs the target to make the trace buffer be of size
39303 @var{size} if possible. A value of @code{-1} tells the target to
39304 use whatever size it prefers.
39306 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39307 @cindex @samp{QTNotes} packet
39308 This packet adds optional textual notes to the trace run. Allowable
39309 types include @code{user}, @code{notes}, and @code{tstop}, the
39310 @var{text} fields are arbitrary strings, hex-encoded.
39314 @subsection Relocate instruction reply packet
39315 When installing fast tracepoints in memory, the target may need to
39316 relocate the instruction currently at the tracepoint address to a
39317 different address in memory. For most instructions, a simple copy is
39318 enough, but, for example, call instructions that implicitly push the
39319 return address on the stack, and relative branches or other
39320 PC-relative instructions require offset adjustment, so that the effect
39321 of executing the instruction at a different address is the same as if
39322 it had executed in the original location.
39324 In response to several of the tracepoint packets, the target may also
39325 respond with a number of intermediate @samp{qRelocInsn} request
39326 packets before the final result packet, to have @value{GDBN} handle
39327 this relocation operation. If a packet supports this mechanism, its
39328 documentation will explicitly say so. See for example the above
39329 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39330 format of the request is:
39333 @item qRelocInsn:@var{from};@var{to}
39335 This requests @value{GDBN} to copy instruction at address @var{from}
39336 to address @var{to}, possibly adjusted so that executing the
39337 instruction at @var{to} has the same effect as executing it at
39338 @var{from}. @value{GDBN} writes the adjusted instruction to target
39339 memory starting at @var{to}.
39344 @item qRelocInsn:@var{adjusted_size}
39345 Informs the stub the relocation is complete. The @var{adjusted_size} is
39346 the length in bytes of resulting relocated instruction sequence.
39348 A badly formed request was detected, or an error was encountered while
39349 relocating the instruction.
39352 @node Host I/O Packets
39353 @section Host I/O Packets
39354 @cindex Host I/O, remote protocol
39355 @cindex file transfer, remote protocol
39357 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39358 operations on the far side of a remote link. For example, Host I/O is
39359 used to upload and download files to a remote target with its own
39360 filesystem. Host I/O uses the same constant values and data structure
39361 layout as the target-initiated File-I/O protocol. However, the
39362 Host I/O packets are structured differently. The target-initiated
39363 protocol relies on target memory to store parameters and buffers.
39364 Host I/O requests are initiated by @value{GDBN}, and the
39365 target's memory is not involved. @xref{File-I/O Remote Protocol
39366 Extension}, for more details on the target-initiated protocol.
39368 The Host I/O request packets all encode a single operation along with
39369 its arguments. They have this format:
39373 @item vFile:@var{operation}: @var{parameter}@dots{}
39374 @var{operation} is the name of the particular request; the target
39375 should compare the entire packet name up to the second colon when checking
39376 for a supported operation. The format of @var{parameter} depends on
39377 the operation. Numbers are always passed in hexadecimal. Negative
39378 numbers have an explicit minus sign (i.e.@: two's complement is not
39379 used). Strings (e.g.@: filenames) are encoded as a series of
39380 hexadecimal bytes. The last argument to a system call may be a
39381 buffer of escaped binary data (@pxref{Binary Data}).
39385 The valid responses to Host I/O packets are:
39389 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39390 @var{result} is the integer value returned by this operation, usually
39391 non-negative for success and -1 for errors. If an error has occured,
39392 @var{errno} will be included in the result specifying a
39393 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39394 operations which return data, @var{attachment} supplies the data as a
39395 binary buffer. Binary buffers in response packets are escaped in the
39396 normal way (@pxref{Binary Data}). See the individual packet
39397 documentation for the interpretation of @var{result} and
39401 An empty response indicates that this operation is not recognized.
39405 These are the supported Host I/O operations:
39408 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39409 Open a file at @var{filename} and return a file descriptor for it, or
39410 return -1 if an error occurs. The @var{filename} is a string,
39411 @var{flags} is an integer indicating a mask of open flags
39412 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39413 of mode bits to use if the file is created (@pxref{mode_t Values}).
39414 @xref{open}, for details of the open flags and mode values.
39416 @item vFile:close: @var{fd}
39417 Close the open file corresponding to @var{fd} and return 0, or
39418 -1 if an error occurs.
39420 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39421 Read data from the open file corresponding to @var{fd}. Up to
39422 @var{count} bytes will be read from the file, starting at @var{offset}
39423 relative to the start of the file. The target may read fewer bytes;
39424 common reasons include packet size limits and an end-of-file
39425 condition. The number of bytes read is returned. Zero should only be
39426 returned for a successful read at the end of the file, or if
39427 @var{count} was zero.
39429 The data read should be returned as a binary attachment on success.
39430 If zero bytes were read, the response should include an empty binary
39431 attachment (i.e.@: a trailing semicolon). The return value is the
39432 number of target bytes read; the binary attachment may be longer if
39433 some characters were escaped.
39435 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39436 Write @var{data} (a binary buffer) to the open file corresponding
39437 to @var{fd}. Start the write at @var{offset} from the start of the
39438 file. Unlike many @code{write} system calls, there is no
39439 separate @var{count} argument; the length of @var{data} in the
39440 packet is used. @samp{vFile:write} returns the number of bytes written,
39441 which may be shorter than the length of @var{data}, or -1 if an
39444 @item vFile:fstat: @var{fd}
39445 Get information about the open file corresponding to @var{fd}.
39446 On success the information is returned as a binary attachment
39447 and the return value is the size of this attachment in bytes.
39448 If an error occurs the return value is -1. The format of the
39449 returned binary attachment is as described in @ref{struct stat}.
39451 @item vFile:unlink: @var{filename}
39452 Delete the file at @var{filename} on the target. Return 0,
39453 or -1 if an error occurs. The @var{filename} is a string.
39455 @item vFile:readlink: @var{filename}
39456 Read value of symbolic link @var{filename} on the target. Return
39457 the number of bytes read, or -1 if an error occurs.
39459 The data read should be returned as a binary attachment on success.
39460 If zero bytes were read, the response should include an empty binary
39461 attachment (i.e.@: a trailing semicolon). The return value is the
39462 number of target bytes read; the binary attachment may be longer if
39463 some characters were escaped.
39465 @item vFile:setfs: @var{pid}
39466 Select the filesystem on which @code{vFile} operations with
39467 @var{filename} arguments will operate. This is required for
39468 @value{GDBN} to be able to access files on remote targets where
39469 the remote stub does not share a common filesystem with the
39472 If @var{pid} is nonzero, select the filesystem as seen by process
39473 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39474 the remote stub. Return 0 on success, or -1 if an error occurs.
39475 If @code{vFile:setfs:} indicates success, the selected filesystem
39476 remains selected until the next successful @code{vFile:setfs:}
39482 @section Interrupts
39483 @cindex interrupts (remote protocol)
39484 @anchor{interrupting remote targets}
39486 In all-stop mode, when a program on the remote target is running,
39487 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39488 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39489 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39491 The precise meaning of @code{BREAK} is defined by the transport
39492 mechanism and may, in fact, be undefined. @value{GDBN} does not
39493 currently define a @code{BREAK} mechanism for any of the network
39494 interfaces except for TCP, in which case @value{GDBN} sends the
39495 @code{telnet} BREAK sequence.
39497 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39498 transport mechanisms. It is represented by sending the single byte
39499 @code{0x03} without any of the usual packet overhead described in
39500 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39501 transmitted as part of a packet, it is considered to be packet data
39502 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39503 (@pxref{X packet}), used for binary downloads, may include an unescaped
39504 @code{0x03} as part of its packet.
39506 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39507 When Linux kernel receives this sequence from serial port,
39508 it stops execution and connects to gdb.
39510 In non-stop mode, because packet resumptions are asynchronous
39511 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39512 command to the remote stub, even when the target is running. For that
39513 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39514 packet}) with the usual packet framing instead of the single byte
39517 Stubs are not required to recognize these interrupt mechanisms and the
39518 precise meaning associated with receipt of the interrupt is
39519 implementation defined. If the target supports debugging of multiple
39520 threads and/or processes, it should attempt to interrupt all
39521 currently-executing threads and processes.
39522 If the stub is successful at interrupting the
39523 running program, it should send one of the stop
39524 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39525 of successfully stopping the program in all-stop mode, and a stop reply
39526 for each stopped thread in non-stop mode.
39527 Interrupts received while the
39528 program is stopped are queued and the program will be interrupted when
39529 it is resumed next time.
39531 @node Notification Packets
39532 @section Notification Packets
39533 @cindex notification packets
39534 @cindex packets, notification
39536 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39537 packets that require no acknowledgment. Both the GDB and the stub
39538 may send notifications (although the only notifications defined at
39539 present are sent by the stub). Notifications carry information
39540 without incurring the round-trip latency of an acknowledgment, and so
39541 are useful for low-impact communications where occasional packet loss
39544 A notification packet has the form @samp{% @var{data} #
39545 @var{checksum}}, where @var{data} is the content of the notification,
39546 and @var{checksum} is a checksum of @var{data}, computed and formatted
39547 as for ordinary @value{GDBN} packets. A notification's @var{data}
39548 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39549 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39550 to acknowledge the notification's receipt or to report its corruption.
39552 Every notification's @var{data} begins with a name, which contains no
39553 colon characters, followed by a colon character.
39555 Recipients should silently ignore corrupted notifications and
39556 notifications they do not understand. Recipients should restart
39557 timeout periods on receipt of a well-formed notification, whether or
39558 not they understand it.
39560 Senders should only send the notifications described here when this
39561 protocol description specifies that they are permitted. In the
39562 future, we may extend the protocol to permit existing notifications in
39563 new contexts; this rule helps older senders avoid confusing newer
39566 (Older versions of @value{GDBN} ignore bytes received until they see
39567 the @samp{$} byte that begins an ordinary packet, so new stubs may
39568 transmit notifications without fear of confusing older clients. There
39569 are no notifications defined for @value{GDBN} to send at the moment, but we
39570 assume that most older stubs would ignore them, as well.)
39572 Each notification is comprised of three parts:
39574 @item @var{name}:@var{event}
39575 The notification packet is sent by the side that initiates the
39576 exchange (currently, only the stub does that), with @var{event}
39577 carrying the specific information about the notification, and
39578 @var{name} specifying the name of the notification.
39580 The acknowledge sent by the other side, usually @value{GDBN}, to
39581 acknowledge the exchange and request the event.
39584 The purpose of an asynchronous notification mechanism is to report to
39585 @value{GDBN} that something interesting happened in the remote stub.
39587 The remote stub may send notification @var{name}:@var{event}
39588 at any time, but @value{GDBN} acknowledges the notification when
39589 appropriate. The notification event is pending before @value{GDBN}
39590 acknowledges. Only one notification at a time may be pending; if
39591 additional events occur before @value{GDBN} has acknowledged the
39592 previous notification, they must be queued by the stub for later
39593 synchronous transmission in response to @var{ack} packets from
39594 @value{GDBN}. Because the notification mechanism is unreliable,
39595 the stub is permitted to resend a notification if it believes
39596 @value{GDBN} may not have received it.
39598 Specifically, notifications may appear when @value{GDBN} is not
39599 otherwise reading input from the stub, or when @value{GDBN} is
39600 expecting to read a normal synchronous response or a
39601 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39602 Notification packets are distinct from any other communication from
39603 the stub so there is no ambiguity.
39605 After receiving a notification, @value{GDBN} shall acknowledge it by
39606 sending a @var{ack} packet as a regular, synchronous request to the
39607 stub. Such acknowledgment is not required to happen immediately, as
39608 @value{GDBN} is permitted to send other, unrelated packets to the
39609 stub first, which the stub should process normally.
39611 Upon receiving a @var{ack} packet, if the stub has other queued
39612 events to report to @value{GDBN}, it shall respond by sending a
39613 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39614 packet to solicit further responses; again, it is permitted to send
39615 other, unrelated packets as well which the stub should process
39618 If the stub receives a @var{ack} packet and there are no additional
39619 @var{event} to report, the stub shall return an @samp{OK} response.
39620 At this point, @value{GDBN} has finished processing a notification
39621 and the stub has completed sending any queued events. @value{GDBN}
39622 won't accept any new notifications until the final @samp{OK} is
39623 received . If further notification events occur, the stub shall send
39624 a new notification, @value{GDBN} shall accept the notification, and
39625 the process shall be repeated.
39627 The process of asynchronous notification can be illustrated by the
39630 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39633 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39635 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39640 The following notifications are defined:
39641 @multitable @columnfractions 0.12 0.12 0.38 0.38
39650 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39651 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39652 for information on how these notifications are acknowledged by
39654 @tab Report an asynchronous stop event in non-stop mode.
39658 @node Remote Non-Stop
39659 @section Remote Protocol Support for Non-Stop Mode
39661 @value{GDBN}'s remote protocol supports non-stop debugging of
39662 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39663 supports non-stop mode, it should report that to @value{GDBN} by including
39664 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39666 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39667 establishing a new connection with the stub. Entering non-stop mode
39668 does not alter the state of any currently-running threads, but targets
39669 must stop all threads in any already-attached processes when entering
39670 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39671 probe the target state after a mode change.
39673 In non-stop mode, when an attached process encounters an event that
39674 would otherwise be reported with a stop reply, it uses the
39675 asynchronous notification mechanism (@pxref{Notification Packets}) to
39676 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39677 in all processes are stopped when a stop reply is sent, in non-stop
39678 mode only the thread reporting the stop event is stopped. That is,
39679 when reporting a @samp{S} or @samp{T} response to indicate completion
39680 of a step operation, hitting a breakpoint, or a fault, only the
39681 affected thread is stopped; any other still-running threads continue
39682 to run. When reporting a @samp{W} or @samp{X} response, all running
39683 threads belonging to other attached processes continue to run.
39685 In non-stop mode, the target shall respond to the @samp{?} packet as
39686 follows. First, any incomplete stop reply notification/@samp{vStopped}
39687 sequence in progress is abandoned. The target must begin a new
39688 sequence reporting stop events for all stopped threads, whether or not
39689 it has previously reported those events to @value{GDBN}. The first
39690 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39691 subsequent stop replies are sent as responses to @samp{vStopped} packets
39692 using the mechanism described above. The target must not send
39693 asynchronous stop reply notifications until the sequence is complete.
39694 If all threads are running when the target receives the @samp{?} packet,
39695 or if the target is not attached to any process, it shall respond
39698 If the stub supports non-stop mode, it should also support the
39699 @samp{swbreak} stop reason if software breakpoints are supported, and
39700 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39701 (@pxref{swbreak stop reason}). This is because given the asynchronous
39702 nature of non-stop mode, between the time a thread hits a breakpoint
39703 and the time the event is finally processed by @value{GDBN}, the
39704 breakpoint may have already been removed from the target. Due to
39705 this, @value{GDBN} needs to be able to tell whether a trap stop was
39706 caused by a delayed breakpoint event, which should be ignored, as
39707 opposed to a random trap signal, which should be reported to the user.
39708 Note the @samp{swbreak} feature implies that the target is responsible
39709 for adjusting the PC when a software breakpoint triggers, if
39710 necessary, such as on the x86 architecture.
39712 @node Packet Acknowledgment
39713 @section Packet Acknowledgment
39715 @cindex acknowledgment, for @value{GDBN} remote
39716 @cindex packet acknowledgment, for @value{GDBN} remote
39717 By default, when either the host or the target machine receives a packet,
39718 the first response expected is an acknowledgment: either @samp{+} (to indicate
39719 the package was received correctly) or @samp{-} (to request retransmission).
39720 This mechanism allows the @value{GDBN} remote protocol to operate over
39721 unreliable transport mechanisms, such as a serial line.
39723 In cases where the transport mechanism is itself reliable (such as a pipe or
39724 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39725 It may be desirable to disable them in that case to reduce communication
39726 overhead, or for other reasons. This can be accomplished by means of the
39727 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39729 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39730 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39731 and response format still includes the normal checksum, as described in
39732 @ref{Overview}, but the checksum may be ignored by the receiver.
39734 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39735 no-acknowledgment mode, it should report that to @value{GDBN}
39736 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39737 @pxref{qSupported}.
39738 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39739 disabled via the @code{set remote noack-packet off} command
39740 (@pxref{Remote Configuration}),
39741 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39742 Only then may the stub actually turn off packet acknowledgments.
39743 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39744 response, which can be safely ignored by the stub.
39746 Note that @code{set remote noack-packet} command only affects negotiation
39747 between @value{GDBN} and the stub when subsequent connections are made;
39748 it does not affect the protocol acknowledgment state for any current
39750 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39751 new connection is established,
39752 there is also no protocol request to re-enable the acknowledgments
39753 for the current connection, once disabled.
39758 Example sequence of a target being re-started. Notice how the restart
39759 does not get any direct output:
39764 @emph{target restarts}
39767 <- @code{T001:1234123412341234}
39771 Example sequence of a target being stepped by a single instruction:
39774 -> @code{G1445@dots{}}
39779 <- @code{T001:1234123412341234}
39783 <- @code{1455@dots{}}
39787 @node File-I/O Remote Protocol Extension
39788 @section File-I/O Remote Protocol Extension
39789 @cindex File-I/O remote protocol extension
39792 * File-I/O Overview::
39793 * Protocol Basics::
39794 * The F Request Packet::
39795 * The F Reply Packet::
39796 * The Ctrl-C Message::
39798 * List of Supported Calls::
39799 * Protocol-specific Representation of Datatypes::
39801 * File-I/O Examples::
39804 @node File-I/O Overview
39805 @subsection File-I/O Overview
39806 @cindex file-i/o overview
39808 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39809 target to use the host's file system and console I/O to perform various
39810 system calls. System calls on the target system are translated into a
39811 remote protocol packet to the host system, which then performs the needed
39812 actions and returns a response packet to the target system.
39813 This simulates file system operations even on targets that lack file systems.
39815 The protocol is defined to be independent of both the host and target systems.
39816 It uses its own internal representation of datatypes and values. Both
39817 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39818 translating the system-dependent value representations into the internal
39819 protocol representations when data is transmitted.
39821 The communication is synchronous. A system call is possible only when
39822 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39823 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39824 the target is stopped to allow deterministic access to the target's
39825 memory. Therefore File-I/O is not interruptible by target signals. On
39826 the other hand, it is possible to interrupt File-I/O by a user interrupt
39827 (@samp{Ctrl-C}) within @value{GDBN}.
39829 The target's request to perform a host system call does not finish
39830 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39831 after finishing the system call, the target returns to continuing the
39832 previous activity (continue, step). No additional continue or step
39833 request from @value{GDBN} is required.
39836 (@value{GDBP}) continue
39837 <- target requests 'system call X'
39838 target is stopped, @value{GDBN} executes system call
39839 -> @value{GDBN} returns result
39840 ... target continues, @value{GDBN} returns to wait for the target
39841 <- target hits breakpoint and sends a Txx packet
39844 The protocol only supports I/O on the console and to regular files on
39845 the host file system. Character or block special devices, pipes,
39846 named pipes, sockets or any other communication method on the host
39847 system are not supported by this protocol.
39849 File I/O is not supported in non-stop mode.
39851 @node Protocol Basics
39852 @subsection Protocol Basics
39853 @cindex protocol basics, file-i/o
39855 The File-I/O protocol uses the @code{F} packet as the request as well
39856 as reply packet. Since a File-I/O system call can only occur when
39857 @value{GDBN} is waiting for a response from the continuing or stepping target,
39858 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39859 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39860 This @code{F} packet contains all information needed to allow @value{GDBN}
39861 to call the appropriate host system call:
39865 A unique identifier for the requested system call.
39868 All parameters to the system call. Pointers are given as addresses
39869 in the target memory address space. Pointers to strings are given as
39870 pointer/length pair. Numerical values are given as they are.
39871 Numerical control flags are given in a protocol-specific representation.
39875 At this point, @value{GDBN} has to perform the following actions.
39879 If the parameters include pointer values to data needed as input to a
39880 system call, @value{GDBN} requests this data from the target with a
39881 standard @code{m} packet request. This additional communication has to be
39882 expected by the target implementation and is handled as any other @code{m}
39886 @value{GDBN} translates all value from protocol representation to host
39887 representation as needed. Datatypes are coerced into the host types.
39890 @value{GDBN} calls the system call.
39893 It then coerces datatypes back to protocol representation.
39896 If the system call is expected to return data in buffer space specified
39897 by pointer parameters to the call, the data is transmitted to the
39898 target using a @code{M} or @code{X} packet. This packet has to be expected
39899 by the target implementation and is handled as any other @code{M} or @code{X}
39904 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39905 necessary information for the target to continue. This at least contains
39912 @code{errno}, if has been changed by the system call.
39919 After having done the needed type and value coercion, the target continues
39920 the latest continue or step action.
39922 @node The F Request Packet
39923 @subsection The @code{F} Request Packet
39924 @cindex file-i/o request packet
39925 @cindex @code{F} request packet
39927 The @code{F} request packet has the following format:
39930 @item F@var{call-id},@var{parameter@dots{}}
39932 @var{call-id} is the identifier to indicate the host system call to be called.
39933 This is just the name of the function.
39935 @var{parameter@dots{}} are the parameters to the system call.
39936 Parameters are hexadecimal integer values, either the actual values in case
39937 of scalar datatypes, pointers to target buffer space in case of compound
39938 datatypes and unspecified memory areas, or pointer/length pairs in case
39939 of string parameters. These are appended to the @var{call-id} as a
39940 comma-delimited list. All values are transmitted in ASCII
39941 string representation, pointer/length pairs separated by a slash.
39947 @node The F Reply Packet
39948 @subsection The @code{F} Reply Packet
39949 @cindex file-i/o reply packet
39950 @cindex @code{F} reply packet
39952 The @code{F} reply packet has the following format:
39956 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39958 @var{retcode} is the return code of the system call as hexadecimal value.
39960 @var{errno} is the @code{errno} set by the call, in protocol-specific
39962 This parameter can be omitted if the call was successful.
39964 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39965 case, @var{errno} must be sent as well, even if the call was successful.
39966 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39973 or, if the call was interrupted before the host call has been performed:
39980 assuming 4 is the protocol-specific representation of @code{EINTR}.
39985 @node The Ctrl-C Message
39986 @subsection The @samp{Ctrl-C} Message
39987 @cindex ctrl-c message, in file-i/o protocol
39989 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39990 reply packet (@pxref{The F Reply Packet}),
39991 the target should behave as if it had
39992 gotten a break message. The meaning for the target is ``system call
39993 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39994 (as with a break message) and return to @value{GDBN} with a @code{T02}
39997 It's important for the target to know in which
39998 state the system call was interrupted. There are two possible cases:
40002 The system call hasn't been performed on the host yet.
40005 The system call on the host has been finished.
40009 These two states can be distinguished by the target by the value of the
40010 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40011 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40012 on POSIX systems. In any other case, the target may presume that the
40013 system call has been finished --- successfully or not --- and should behave
40014 as if the break message arrived right after the system call.
40016 @value{GDBN} must behave reliably. If the system call has not been called
40017 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40018 @code{errno} in the packet. If the system call on the host has been finished
40019 before the user requests a break, the full action must be finished by
40020 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40021 The @code{F} packet may only be sent when either nothing has happened
40022 or the full action has been completed.
40025 @subsection Console I/O
40026 @cindex console i/o as part of file-i/o
40028 By default and if not explicitly closed by the target system, the file
40029 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40030 on the @value{GDBN} console is handled as any other file output operation
40031 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40032 by @value{GDBN} so that after the target read request from file descriptor
40033 0 all following typing is buffered until either one of the following
40038 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40040 system call is treated as finished.
40043 The user presses @key{RET}. This is treated as end of input with a trailing
40047 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40048 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40052 If the user has typed more characters than fit in the buffer given to
40053 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40054 either another @code{read(0, @dots{})} is requested by the target, or debugging
40055 is stopped at the user's request.
40058 @node List of Supported Calls
40059 @subsection List of Supported Calls
40060 @cindex list of supported file-i/o calls
40077 @unnumberedsubsubsec open
40078 @cindex open, file-i/o system call
40083 int open(const char *pathname, int flags);
40084 int open(const char *pathname, int flags, mode_t mode);
40088 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40091 @var{flags} is the bitwise @code{OR} of the following values:
40095 If the file does not exist it will be created. The host
40096 rules apply as far as file ownership and time stamps
40100 When used with @code{O_CREAT}, if the file already exists it is
40101 an error and open() fails.
40104 If the file already exists and the open mode allows
40105 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40106 truncated to zero length.
40109 The file is opened in append mode.
40112 The file is opened for reading only.
40115 The file is opened for writing only.
40118 The file is opened for reading and writing.
40122 Other bits are silently ignored.
40126 @var{mode} is the bitwise @code{OR} of the following values:
40130 User has read permission.
40133 User has write permission.
40136 Group has read permission.
40139 Group has write permission.
40142 Others have read permission.
40145 Others have write permission.
40149 Other bits are silently ignored.
40152 @item Return value:
40153 @code{open} returns the new file descriptor or -1 if an error
40160 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40163 @var{pathname} refers to a directory.
40166 The requested access is not allowed.
40169 @var{pathname} was too long.
40172 A directory component in @var{pathname} does not exist.
40175 @var{pathname} refers to a device, pipe, named pipe or socket.
40178 @var{pathname} refers to a file on a read-only filesystem and
40179 write access was requested.
40182 @var{pathname} is an invalid pointer value.
40185 No space on device to create the file.
40188 The process already has the maximum number of files open.
40191 The limit on the total number of files open on the system
40195 The call was interrupted by the user.
40201 @unnumberedsubsubsec close
40202 @cindex close, file-i/o system call
40211 @samp{Fclose,@var{fd}}
40213 @item Return value:
40214 @code{close} returns zero on success, or -1 if an error occurred.
40220 @var{fd} isn't a valid open file descriptor.
40223 The call was interrupted by the user.
40229 @unnumberedsubsubsec read
40230 @cindex read, file-i/o system call
40235 int read(int fd, void *buf, unsigned int count);
40239 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40241 @item Return value:
40242 On success, the number of bytes read is returned.
40243 Zero indicates end of file. If count is zero, read
40244 returns zero as well. On error, -1 is returned.
40250 @var{fd} is not a valid file descriptor or is not open for
40254 @var{bufptr} is an invalid pointer value.
40257 The call was interrupted by the user.
40263 @unnumberedsubsubsec write
40264 @cindex write, file-i/o system call
40269 int write(int fd, const void *buf, unsigned int count);
40273 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40275 @item Return value:
40276 On success, the number of bytes written are returned.
40277 Zero indicates nothing was written. On error, -1
40284 @var{fd} is not a valid file descriptor or is not open for
40288 @var{bufptr} is an invalid pointer value.
40291 An attempt was made to write a file that exceeds the
40292 host-specific maximum file size allowed.
40295 No space on device to write the data.
40298 The call was interrupted by the user.
40304 @unnumberedsubsubsec lseek
40305 @cindex lseek, file-i/o system call
40310 long lseek (int fd, long offset, int flag);
40314 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40316 @var{flag} is one of:
40320 The offset is set to @var{offset} bytes.
40323 The offset is set to its current location plus @var{offset}
40327 The offset is set to the size of the file plus @var{offset}
40331 @item Return value:
40332 On success, the resulting unsigned offset in bytes from
40333 the beginning of the file is returned. Otherwise, a
40334 value of -1 is returned.
40340 @var{fd} is not a valid open file descriptor.
40343 @var{fd} is associated with the @value{GDBN} console.
40346 @var{flag} is not a proper value.
40349 The call was interrupted by the user.
40355 @unnumberedsubsubsec rename
40356 @cindex rename, file-i/o system call
40361 int rename(const char *oldpath, const char *newpath);
40365 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40367 @item Return value:
40368 On success, zero is returned. On error, -1 is returned.
40374 @var{newpath} is an existing directory, but @var{oldpath} is not a
40378 @var{newpath} is a non-empty directory.
40381 @var{oldpath} or @var{newpath} is a directory that is in use by some
40385 An attempt was made to make a directory a subdirectory
40389 A component used as a directory in @var{oldpath} or new
40390 path is not a directory. Or @var{oldpath} is a directory
40391 and @var{newpath} exists but is not a directory.
40394 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40397 No access to the file or the path of the file.
40401 @var{oldpath} or @var{newpath} was too long.
40404 A directory component in @var{oldpath} or @var{newpath} does not exist.
40407 The file is on a read-only filesystem.
40410 The device containing the file has no room for the new
40414 The call was interrupted by the user.
40420 @unnumberedsubsubsec unlink
40421 @cindex unlink, file-i/o system call
40426 int unlink(const char *pathname);
40430 @samp{Funlink,@var{pathnameptr}/@var{len}}
40432 @item Return value:
40433 On success, zero is returned. On error, -1 is returned.
40439 No access to the file or the path of the file.
40442 The system does not allow unlinking of directories.
40445 The file @var{pathname} cannot be unlinked because it's
40446 being used by another process.
40449 @var{pathnameptr} is an invalid pointer value.
40452 @var{pathname} was too long.
40455 A directory component in @var{pathname} does not exist.
40458 A component of the path is not a directory.
40461 The file is on a read-only filesystem.
40464 The call was interrupted by the user.
40470 @unnumberedsubsubsec stat/fstat
40471 @cindex fstat, file-i/o system call
40472 @cindex stat, file-i/o system call
40477 int stat(const char *pathname, struct stat *buf);
40478 int fstat(int fd, struct stat *buf);
40482 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40483 @samp{Ffstat,@var{fd},@var{bufptr}}
40485 @item Return value:
40486 On success, zero is returned. On error, -1 is returned.
40492 @var{fd} is not a valid open file.
40495 A directory component in @var{pathname} does not exist or the
40496 path is an empty string.
40499 A component of the path is not a directory.
40502 @var{pathnameptr} is an invalid pointer value.
40505 No access to the file or the path of the file.
40508 @var{pathname} was too long.
40511 The call was interrupted by the user.
40517 @unnumberedsubsubsec gettimeofday
40518 @cindex gettimeofday, file-i/o system call
40523 int gettimeofday(struct timeval *tv, void *tz);
40527 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40529 @item Return value:
40530 On success, 0 is returned, -1 otherwise.
40536 @var{tz} is a non-NULL pointer.
40539 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40545 @unnumberedsubsubsec isatty
40546 @cindex isatty, file-i/o system call
40551 int isatty(int fd);
40555 @samp{Fisatty,@var{fd}}
40557 @item Return value:
40558 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40564 The call was interrupted by the user.
40569 Note that the @code{isatty} call is treated as a special case: it returns
40570 1 to the target if the file descriptor is attached
40571 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40572 would require implementing @code{ioctl} and would be more complex than
40577 @unnumberedsubsubsec system
40578 @cindex system, file-i/o system call
40583 int system(const char *command);
40587 @samp{Fsystem,@var{commandptr}/@var{len}}
40589 @item Return value:
40590 If @var{len} is zero, the return value indicates whether a shell is
40591 available. A zero return value indicates a shell is not available.
40592 For non-zero @var{len}, the value returned is -1 on error and the
40593 return status of the command otherwise. Only the exit status of the
40594 command is returned, which is extracted from the host's @code{system}
40595 return value by calling @code{WEXITSTATUS(retval)}. In case
40596 @file{/bin/sh} could not be executed, 127 is returned.
40602 The call was interrupted by the user.
40607 @value{GDBN} takes over the full task of calling the necessary host calls
40608 to perform the @code{system} call. The return value of @code{system} on
40609 the host is simplified before it's returned
40610 to the target. Any termination signal information from the child process
40611 is discarded, and the return value consists
40612 entirely of the exit status of the called command.
40614 Due to security concerns, the @code{system} call is by default refused
40615 by @value{GDBN}. The user has to allow this call explicitly with the
40616 @code{set remote system-call-allowed 1} command.
40619 @item set remote system-call-allowed
40620 @kindex set remote system-call-allowed
40621 Control whether to allow the @code{system} calls in the File I/O
40622 protocol for the remote target. The default is zero (disabled).
40624 @item show remote system-call-allowed
40625 @kindex show remote system-call-allowed
40626 Show whether the @code{system} calls are allowed in the File I/O
40630 @node Protocol-specific Representation of Datatypes
40631 @subsection Protocol-specific Representation of Datatypes
40632 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40635 * Integral Datatypes::
40637 * Memory Transfer::
40642 @node Integral Datatypes
40643 @unnumberedsubsubsec Integral Datatypes
40644 @cindex integral datatypes, in file-i/o protocol
40646 The integral datatypes used in the system calls are @code{int},
40647 @code{unsigned int}, @code{long}, @code{unsigned long},
40648 @code{mode_t}, and @code{time_t}.
40650 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40651 implemented as 32 bit values in this protocol.
40653 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40655 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40656 in @file{limits.h}) to allow range checking on host and target.
40658 @code{time_t} datatypes are defined as seconds since the Epoch.
40660 All integral datatypes transferred as part of a memory read or write of a
40661 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40664 @node Pointer Values
40665 @unnumberedsubsubsec Pointer Values
40666 @cindex pointer values, in file-i/o protocol
40668 Pointers to target data are transmitted as they are. An exception
40669 is made for pointers to buffers for which the length isn't
40670 transmitted as part of the function call, namely strings. Strings
40671 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40678 which is a pointer to data of length 18 bytes at position 0x1aaf.
40679 The length is defined as the full string length in bytes, including
40680 the trailing null byte. For example, the string @code{"hello world"}
40681 at address 0x123456 is transmitted as
40687 @node Memory Transfer
40688 @unnumberedsubsubsec Memory Transfer
40689 @cindex memory transfer, in file-i/o protocol
40691 Structured data which is transferred using a memory read or write (for
40692 example, a @code{struct stat}) is expected to be in a protocol-specific format
40693 with all scalar multibyte datatypes being big endian. Translation to
40694 this representation needs to be done both by the target before the @code{F}
40695 packet is sent, and by @value{GDBN} before
40696 it transfers memory to the target. Transferred pointers to structured
40697 data should point to the already-coerced data at any time.
40701 @unnumberedsubsubsec struct stat
40702 @cindex struct stat, in file-i/o protocol
40704 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40705 is defined as follows:
40709 unsigned int st_dev; /* device */
40710 unsigned int st_ino; /* inode */
40711 mode_t st_mode; /* protection */
40712 unsigned int st_nlink; /* number of hard links */
40713 unsigned int st_uid; /* user ID of owner */
40714 unsigned int st_gid; /* group ID of owner */
40715 unsigned int st_rdev; /* device type (if inode device) */
40716 unsigned long st_size; /* total size, in bytes */
40717 unsigned long st_blksize; /* blocksize for filesystem I/O */
40718 unsigned long st_blocks; /* number of blocks allocated */
40719 time_t st_atime; /* time of last access */
40720 time_t st_mtime; /* time of last modification */
40721 time_t st_ctime; /* time of last change */
40725 The integral datatypes conform to the definitions given in the
40726 appropriate section (see @ref{Integral Datatypes}, for details) so this
40727 structure is of size 64 bytes.
40729 The values of several fields have a restricted meaning and/or
40735 A value of 0 represents a file, 1 the console.
40738 No valid meaning for the target. Transmitted unchanged.
40741 Valid mode bits are described in @ref{Constants}. Any other
40742 bits have currently no meaning for the target.
40747 No valid meaning for the target. Transmitted unchanged.
40752 These values have a host and file system dependent
40753 accuracy. Especially on Windows hosts, the file system may not
40754 support exact timing values.
40757 The target gets a @code{struct stat} of the above representation and is
40758 responsible for coercing it to the target representation before
40761 Note that due to size differences between the host, target, and protocol
40762 representations of @code{struct stat} members, these members could eventually
40763 get truncated on the target.
40765 @node struct timeval
40766 @unnumberedsubsubsec struct timeval
40767 @cindex struct timeval, in file-i/o protocol
40769 The buffer of type @code{struct timeval} used by the File-I/O protocol
40770 is defined as follows:
40774 time_t tv_sec; /* second */
40775 long tv_usec; /* microsecond */
40779 The integral datatypes conform to the definitions given in the
40780 appropriate section (see @ref{Integral Datatypes}, for details) so this
40781 structure is of size 8 bytes.
40784 @subsection Constants
40785 @cindex constants, in file-i/o protocol
40787 The following values are used for the constants inside of the
40788 protocol. @value{GDBN} and target are responsible for translating these
40789 values before and after the call as needed.
40800 @unnumberedsubsubsec Open Flags
40801 @cindex open flags, in file-i/o protocol
40803 All values are given in hexadecimal representation.
40815 @node mode_t Values
40816 @unnumberedsubsubsec mode_t Values
40817 @cindex mode_t values, in file-i/o protocol
40819 All values are given in octal representation.
40836 @unnumberedsubsubsec Errno Values
40837 @cindex errno values, in file-i/o protocol
40839 All values are given in decimal representation.
40864 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40865 any error value not in the list of supported error numbers.
40868 @unnumberedsubsubsec Lseek Flags
40869 @cindex lseek flags, in file-i/o protocol
40878 @unnumberedsubsubsec Limits
40879 @cindex limits, in file-i/o protocol
40881 All values are given in decimal representation.
40884 INT_MIN -2147483648
40886 UINT_MAX 4294967295
40887 LONG_MIN -9223372036854775808
40888 LONG_MAX 9223372036854775807
40889 ULONG_MAX 18446744073709551615
40892 @node File-I/O Examples
40893 @subsection File-I/O Examples
40894 @cindex file-i/o examples
40896 Example sequence of a write call, file descriptor 3, buffer is at target
40897 address 0x1234, 6 bytes should be written:
40900 <- @code{Fwrite,3,1234,6}
40901 @emph{request memory read from target}
40904 @emph{return "6 bytes written"}
40908 Example sequence of a read call, file descriptor 3, buffer is at target
40909 address 0x1234, 6 bytes should be read:
40912 <- @code{Fread,3,1234,6}
40913 @emph{request memory write to target}
40914 -> @code{X1234,6:XXXXXX}
40915 @emph{return "6 bytes read"}
40919 Example sequence of a read call, call fails on the host due to invalid
40920 file descriptor (@code{EBADF}):
40923 <- @code{Fread,3,1234,6}
40927 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40931 <- @code{Fread,3,1234,6}
40936 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40940 <- @code{Fread,3,1234,6}
40941 -> @code{X1234,6:XXXXXX}
40945 @node Library List Format
40946 @section Library List Format
40947 @cindex library list format, remote protocol
40949 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40950 same process as your application to manage libraries. In this case,
40951 @value{GDBN} can use the loader's symbol table and normal memory
40952 operations to maintain a list of shared libraries. On other
40953 platforms, the operating system manages loaded libraries.
40954 @value{GDBN} can not retrieve the list of currently loaded libraries
40955 through memory operations, so it uses the @samp{qXfer:libraries:read}
40956 packet (@pxref{qXfer library list read}) instead. The remote stub
40957 queries the target's operating system and reports which libraries
40960 The @samp{qXfer:libraries:read} packet returns an XML document which
40961 lists loaded libraries and their offsets. Each library has an
40962 associated name and one or more segment or section base addresses,
40963 which report where the library was loaded in memory.
40965 For the common case of libraries that are fully linked binaries, the
40966 library should have a list of segments. If the target supports
40967 dynamic linking of a relocatable object file, its library XML element
40968 should instead include a list of allocated sections. The segment or
40969 section bases are start addresses, not relocation offsets; they do not
40970 depend on the library's link-time base addresses.
40972 @value{GDBN} must be linked with the Expat library to support XML
40973 library lists. @xref{Expat}.
40975 A simple memory map, with one loaded library relocated by a single
40976 offset, looks like this:
40980 <library name="/lib/libc.so.6">
40981 <segment address="0x10000000"/>
40986 Another simple memory map, with one loaded library with three
40987 allocated sections (.text, .data, .bss), looks like this:
40991 <library name="sharedlib.o">
40992 <section address="0x10000000"/>
40993 <section address="0x20000000"/>
40994 <section address="0x30000000"/>
40999 The format of a library list is described by this DTD:
41002 <!-- library-list: Root element with versioning -->
41003 <!ELEMENT library-list (library)*>
41004 <!ATTLIST library-list version CDATA #FIXED "1.0">
41005 <!ELEMENT library (segment*, section*)>
41006 <!ATTLIST library name CDATA #REQUIRED>
41007 <!ELEMENT segment EMPTY>
41008 <!ATTLIST segment address CDATA #REQUIRED>
41009 <!ELEMENT section EMPTY>
41010 <!ATTLIST section address CDATA #REQUIRED>
41013 In addition, segments and section descriptors cannot be mixed within a
41014 single library element, and you must supply at least one segment or
41015 section for each library.
41017 @node Library List Format for SVR4 Targets
41018 @section Library List Format for SVR4 Targets
41019 @cindex library list format, remote protocol
41021 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41022 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41023 shared libraries. Still a special library list provided by this packet is
41024 more efficient for the @value{GDBN} remote protocol.
41026 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41027 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41028 target, the following parameters are reported:
41032 @code{name}, the absolute file name from the @code{l_name} field of
41033 @code{struct link_map}.
41035 @code{lm} with address of @code{struct link_map} used for TLS
41036 (Thread Local Storage) access.
41038 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41039 @code{struct link_map}. For prelinked libraries this is not an absolute
41040 memory address. It is a displacement of absolute memory address against
41041 address the file was prelinked to during the library load.
41043 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41046 Additionally the single @code{main-lm} attribute specifies address of
41047 @code{struct link_map} used for the main executable. This parameter is used
41048 for TLS access and its presence is optional.
41050 @value{GDBN} must be linked with the Expat library to support XML
41051 SVR4 library lists. @xref{Expat}.
41053 A simple memory map, with two loaded libraries (which do not use prelink),
41057 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41058 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41060 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41062 </library-list-svr>
41065 The format of an SVR4 library list is described by this DTD:
41068 <!-- library-list-svr4: Root element with versioning -->
41069 <!ELEMENT library-list-svr4 (library)*>
41070 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41071 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41072 <!ELEMENT library EMPTY>
41073 <!ATTLIST library name CDATA #REQUIRED>
41074 <!ATTLIST library lm CDATA #REQUIRED>
41075 <!ATTLIST library l_addr CDATA #REQUIRED>
41076 <!ATTLIST library l_ld CDATA #REQUIRED>
41079 @node Memory Map Format
41080 @section Memory Map Format
41081 @cindex memory map format
41083 To be able to write into flash memory, @value{GDBN} needs to obtain a
41084 memory map from the target. This section describes the format of the
41087 The memory map is obtained using the @samp{qXfer:memory-map:read}
41088 (@pxref{qXfer memory map read}) packet and is an XML document that
41089 lists memory regions.
41091 @value{GDBN} must be linked with the Expat library to support XML
41092 memory maps. @xref{Expat}.
41094 The top-level structure of the document is shown below:
41097 <?xml version="1.0"?>
41098 <!DOCTYPE memory-map
41099 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41100 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41106 Each region can be either:
41111 A region of RAM starting at @var{addr} and extending for @var{length}
41115 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41120 A region of read-only memory:
41123 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41128 A region of flash memory, with erasure blocks @var{blocksize}
41132 <memory type="flash" start="@var{addr}" length="@var{length}">
41133 <property name="blocksize">@var{blocksize}</property>
41139 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41140 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41141 packets to write to addresses in such ranges.
41143 The formal DTD for memory map format is given below:
41146 <!-- ................................................... -->
41147 <!-- Memory Map XML DTD ................................ -->
41148 <!-- File: memory-map.dtd .............................. -->
41149 <!-- .................................... .............. -->
41150 <!-- memory-map.dtd -->
41151 <!-- memory-map: Root element with versioning -->
41152 <!ELEMENT memory-map (memory)*>
41153 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41154 <!ELEMENT memory (property)*>
41155 <!-- memory: Specifies a memory region,
41156 and its type, or device. -->
41157 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41158 start CDATA #REQUIRED
41159 length CDATA #REQUIRED>
41160 <!-- property: Generic attribute tag -->
41161 <!ELEMENT property (#PCDATA | property)*>
41162 <!ATTLIST property name (blocksize) #REQUIRED>
41165 @node Thread List Format
41166 @section Thread List Format
41167 @cindex thread list format
41169 To efficiently update the list of threads and their attributes,
41170 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41171 (@pxref{qXfer threads read}) and obtains the XML document with
41172 the following structure:
41175 <?xml version="1.0"?>
41177 <thread id="id" core="0" name="name">
41178 ... description ...
41183 Each @samp{thread} element must have the @samp{id} attribute that
41184 identifies the thread (@pxref{thread-id syntax}). The
41185 @samp{core} attribute, if present, specifies which processor core
41186 the thread was last executing on. The @samp{name} attribute, if
41187 present, specifies the human-readable name of the thread. The content
41188 of the of @samp{thread} element is interpreted as human-readable
41189 auxiliary information. The @samp{handle} attribute, if present,
41190 is a hex encoded representation of the thread handle.
41193 @node Traceframe Info Format
41194 @section Traceframe Info Format
41195 @cindex traceframe info format
41197 To be able to know which objects in the inferior can be examined when
41198 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41199 memory ranges, registers and trace state variables that have been
41200 collected in a traceframe.
41202 This list is obtained using the @samp{qXfer:traceframe-info:read}
41203 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41205 @value{GDBN} must be linked with the Expat library to support XML
41206 traceframe info discovery. @xref{Expat}.
41208 The top-level structure of the document is shown below:
41211 <?xml version="1.0"?>
41212 <!DOCTYPE traceframe-info
41213 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41214 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41220 Each traceframe block can be either:
41225 A region of collected memory starting at @var{addr} and extending for
41226 @var{length} bytes from there:
41229 <memory start="@var{addr}" length="@var{length}"/>
41233 A block indicating trace state variable numbered @var{number} has been
41237 <tvar id="@var{number}"/>
41242 The formal DTD for the traceframe info format is given below:
41245 <!ELEMENT traceframe-info (memory | tvar)* >
41246 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41248 <!ELEMENT memory EMPTY>
41249 <!ATTLIST memory start CDATA #REQUIRED
41250 length CDATA #REQUIRED>
41252 <!ATTLIST tvar id CDATA #REQUIRED>
41255 @node Branch Trace Format
41256 @section Branch Trace Format
41257 @cindex branch trace format
41259 In order to display the branch trace of an inferior thread,
41260 @value{GDBN} needs to obtain the list of branches. This list is
41261 represented as list of sequential code blocks that are connected via
41262 branches. The code in each block has been executed sequentially.
41264 This list is obtained using the @samp{qXfer:btrace:read}
41265 (@pxref{qXfer btrace read}) packet and is an XML document.
41267 @value{GDBN} must be linked with the Expat library to support XML
41268 traceframe info discovery. @xref{Expat}.
41270 The top-level structure of the document is shown below:
41273 <?xml version="1.0"?>
41275 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41276 "http://sourceware.org/gdb/gdb-btrace.dtd">
41285 A block of sequentially executed instructions starting at @var{begin}
41286 and ending at @var{end}:
41289 <block begin="@var{begin}" end="@var{end}"/>
41294 The formal DTD for the branch trace format is given below:
41297 <!ELEMENT btrace (block* | pt) >
41298 <!ATTLIST btrace version CDATA #FIXED "1.0">
41300 <!ELEMENT block EMPTY>
41301 <!ATTLIST block begin CDATA #REQUIRED
41302 end CDATA #REQUIRED>
41304 <!ELEMENT pt (pt-config?, raw?)>
41306 <!ELEMENT pt-config (cpu?)>
41308 <!ELEMENT cpu EMPTY>
41309 <!ATTLIST cpu vendor CDATA #REQUIRED
41310 family CDATA #REQUIRED
41311 model CDATA #REQUIRED
41312 stepping CDATA #REQUIRED>
41314 <!ELEMENT raw (#PCDATA)>
41317 @node Branch Trace Configuration Format
41318 @section Branch Trace Configuration Format
41319 @cindex branch trace configuration format
41321 For each inferior thread, @value{GDBN} can obtain the branch trace
41322 configuration using the @samp{qXfer:btrace-conf:read}
41323 (@pxref{qXfer btrace-conf read}) packet.
41325 The configuration describes the branch trace format and configuration
41326 settings for that format. The following information is described:
41330 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41333 The size of the @acronym{BTS} ring buffer in bytes.
41336 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41340 The size of the @acronym{Intel PT} ring buffer in bytes.
41344 @value{GDBN} must be linked with the Expat library to support XML
41345 branch trace configuration discovery. @xref{Expat}.
41347 The formal DTD for the branch trace configuration format is given below:
41350 <!ELEMENT btrace-conf (bts?, pt?)>
41351 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41353 <!ELEMENT bts EMPTY>
41354 <!ATTLIST bts size CDATA #IMPLIED>
41356 <!ELEMENT pt EMPTY>
41357 <!ATTLIST pt size CDATA #IMPLIED>
41360 @include agentexpr.texi
41362 @node Target Descriptions
41363 @appendix Target Descriptions
41364 @cindex target descriptions
41366 One of the challenges of using @value{GDBN} to debug embedded systems
41367 is that there are so many minor variants of each processor
41368 architecture in use. It is common practice for vendors to start with
41369 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41370 and then make changes to adapt it to a particular market niche. Some
41371 architectures have hundreds of variants, available from dozens of
41372 vendors. This leads to a number of problems:
41376 With so many different customized processors, it is difficult for
41377 the @value{GDBN} maintainers to keep up with the changes.
41379 Since individual variants may have short lifetimes or limited
41380 audiences, it may not be worthwhile to carry information about every
41381 variant in the @value{GDBN} source tree.
41383 When @value{GDBN} does support the architecture of the embedded system
41384 at hand, the task of finding the correct architecture name to give the
41385 @command{set architecture} command can be error-prone.
41388 To address these problems, the @value{GDBN} remote protocol allows a
41389 target system to not only identify itself to @value{GDBN}, but to
41390 actually describe its own features. This lets @value{GDBN} support
41391 processor variants it has never seen before --- to the extent that the
41392 descriptions are accurate, and that @value{GDBN} understands them.
41394 @value{GDBN} must be linked with the Expat library to support XML
41395 target descriptions. @xref{Expat}.
41398 * Retrieving Descriptions:: How descriptions are fetched from a target.
41399 * Target Description Format:: The contents of a target description.
41400 * Predefined Target Types:: Standard types available for target
41402 * Enum Target Types:: How to define enum target types.
41403 * Standard Target Features:: Features @value{GDBN} knows about.
41406 @node Retrieving Descriptions
41407 @section Retrieving Descriptions
41409 Target descriptions can be read from the target automatically, or
41410 specified by the user manually. The default behavior is to read the
41411 description from the target. @value{GDBN} retrieves it via the remote
41412 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41413 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41414 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41415 XML document, of the form described in @ref{Target Description
41418 Alternatively, you can specify a file to read for the target description.
41419 If a file is set, the target will not be queried. The commands to
41420 specify a file are:
41423 @cindex set tdesc filename
41424 @item set tdesc filename @var{path}
41425 Read the target description from @var{path}.
41427 @cindex unset tdesc filename
41428 @item unset tdesc filename
41429 Do not read the XML target description from a file. @value{GDBN}
41430 will use the description supplied by the current target.
41432 @cindex show tdesc filename
41433 @item show tdesc filename
41434 Show the filename to read for a target description, if any.
41438 @node Target Description Format
41439 @section Target Description Format
41440 @cindex target descriptions, XML format
41442 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41443 document which complies with the Document Type Definition provided in
41444 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41445 means you can use generally available tools like @command{xmllint} to
41446 check that your feature descriptions are well-formed and valid.
41447 However, to help people unfamiliar with XML write descriptions for
41448 their targets, we also describe the grammar here.
41450 Target descriptions can identify the architecture of the remote target
41451 and (for some architectures) provide information about custom register
41452 sets. They can also identify the OS ABI of the remote target.
41453 @value{GDBN} can use this information to autoconfigure for your
41454 target, or to warn you if you connect to an unsupported target.
41456 Here is a simple target description:
41459 <target version="1.0">
41460 <architecture>i386:x86-64</architecture>
41465 This minimal description only says that the target uses
41466 the x86-64 architecture.
41468 A target description has the following overall form, with [ ] marking
41469 optional elements and @dots{} marking repeatable elements. The elements
41470 are explained further below.
41473 <?xml version="1.0"?>
41474 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41475 <target version="1.0">
41476 @r{[}@var{architecture}@r{]}
41477 @r{[}@var{osabi}@r{]}
41478 @r{[}@var{compatible}@r{]}
41479 @r{[}@var{feature}@dots{}@r{]}
41484 The description is generally insensitive to whitespace and line
41485 breaks, under the usual common-sense rules. The XML version
41486 declaration and document type declaration can generally be omitted
41487 (@value{GDBN} does not require them), but specifying them may be
41488 useful for XML validation tools. The @samp{version} attribute for
41489 @samp{<target>} may also be omitted, but we recommend
41490 including it; if future versions of @value{GDBN} use an incompatible
41491 revision of @file{gdb-target.dtd}, they will detect and report
41492 the version mismatch.
41494 @subsection Inclusion
41495 @cindex target descriptions, inclusion
41498 @cindex <xi:include>
41501 It can sometimes be valuable to split a target description up into
41502 several different annexes, either for organizational purposes, or to
41503 share files between different possible target descriptions. You can
41504 divide a description into multiple files by replacing any element of
41505 the target description with an inclusion directive of the form:
41508 <xi:include href="@var{document}"/>
41512 When @value{GDBN} encounters an element of this form, it will retrieve
41513 the named XML @var{document}, and replace the inclusion directive with
41514 the contents of that document. If the current description was read
41515 using @samp{qXfer}, then so will be the included document;
41516 @var{document} will be interpreted as the name of an annex. If the
41517 current description was read from a file, @value{GDBN} will look for
41518 @var{document} as a file in the same directory where it found the
41519 original description.
41521 @subsection Architecture
41522 @cindex <architecture>
41524 An @samp{<architecture>} element has this form:
41527 <architecture>@var{arch}</architecture>
41530 @var{arch} is one of the architectures from the set accepted by
41531 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41534 @cindex @code{<osabi>}
41536 This optional field was introduced in @value{GDBN} version 7.0.
41537 Previous versions of @value{GDBN} ignore it.
41539 An @samp{<osabi>} element has this form:
41542 <osabi>@var{abi-name}</osabi>
41545 @var{abi-name} is an OS ABI name from the same selection accepted by
41546 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41548 @subsection Compatible Architecture
41549 @cindex @code{<compatible>}
41551 This optional field was introduced in @value{GDBN} version 7.0.
41552 Previous versions of @value{GDBN} ignore it.
41554 A @samp{<compatible>} element has this form:
41557 <compatible>@var{arch}</compatible>
41560 @var{arch} is one of the architectures from the set accepted by
41561 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41563 A @samp{<compatible>} element is used to specify that the target
41564 is able to run binaries in some other than the main target architecture
41565 given by the @samp{<architecture>} element. For example, on the
41566 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41567 or @code{powerpc:common64}, but the system is able to run binaries
41568 in the @code{spu} architecture as well. The way to describe this
41569 capability with @samp{<compatible>} is as follows:
41572 <architecture>powerpc:common</architecture>
41573 <compatible>spu</compatible>
41576 @subsection Features
41579 Each @samp{<feature>} describes some logical portion of the target
41580 system. Features are currently used to describe available CPU
41581 registers and the types of their contents. A @samp{<feature>} element
41585 <feature name="@var{name}">
41586 @r{[}@var{type}@dots{}@r{]}
41592 Each feature's name should be unique within the description. The name
41593 of a feature does not matter unless @value{GDBN} has some special
41594 knowledge of the contents of that feature; if it does, the feature
41595 should have its standard name. @xref{Standard Target Features}.
41599 Any register's value is a collection of bits which @value{GDBN} must
41600 interpret. The default interpretation is a two's complement integer,
41601 but other types can be requested by name in the register description.
41602 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41603 Target Types}), and the description can define additional composite
41606 Each type element must have an @samp{id} attribute, which gives
41607 a unique (within the containing @samp{<feature>}) name to the type.
41608 Types must be defined before they are used.
41611 Some targets offer vector registers, which can be treated as arrays
41612 of scalar elements. These types are written as @samp{<vector>} elements,
41613 specifying the array element type, @var{type}, and the number of elements,
41617 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41621 If a register's value is usefully viewed in multiple ways, define it
41622 with a union type containing the useful representations. The
41623 @samp{<union>} element contains one or more @samp{<field>} elements,
41624 each of which has a @var{name} and a @var{type}:
41627 <union id="@var{id}">
41628 <field name="@var{name}" type="@var{type}"/>
41635 If a register's value is composed from several separate values, define
41636 it with either a structure type or a flags type.
41637 A flags type may only contain bitfields.
41638 A structure type may either contain only bitfields or contain no bitfields.
41639 If the value contains only bitfields, its total size in bytes must be
41642 Non-bitfield values have a @var{name} and @var{type}.
41645 <struct id="@var{id}">
41646 <field name="@var{name}" type="@var{type}"/>
41651 Both @var{name} and @var{type} values are required.
41652 No implicit padding is added.
41654 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41657 <struct id="@var{id}" size="@var{size}">
41658 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41664 <flags id="@var{id}" size="@var{size}">
41665 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41670 The @var{name} value is required.
41671 Bitfield values may be named with the empty string, @samp{""},
41672 in which case the field is ``filler'' and its value is not printed.
41673 Not all bits need to be specified, so ``filler'' fields are optional.
41675 The @var{start} and @var{end} values are required, and @var{type}
41677 The field's @var{start} must be less than or equal to its @var{end},
41678 and zero represents the least significant bit.
41680 The default value of @var{type} is @code{bool} for single bit fields,
41681 and an unsigned integer otherwise.
41683 Which to choose? Structures or flags?
41685 Registers defined with @samp{flags} have these advantages over
41686 defining them with @samp{struct}:
41690 Arithmetic may be performed on them as if they were integers.
41692 They are printed in a more readable fashion.
41695 Registers defined with @samp{struct} have one advantage over
41696 defining them with @samp{flags}:
41700 One can fetch individual fields like in @samp{C}.
41703 (gdb) print $my_struct_reg.field3
41709 @subsection Registers
41712 Each register is represented as an element with this form:
41715 <reg name="@var{name}"
41716 bitsize="@var{size}"
41717 @r{[}regnum="@var{num}"@r{]}
41718 @r{[}save-restore="@var{save-restore}"@r{]}
41719 @r{[}type="@var{type}"@r{]}
41720 @r{[}group="@var{group}"@r{]}/>
41724 The components are as follows:
41729 The register's name; it must be unique within the target description.
41732 The register's size, in bits.
41735 The register's number. If omitted, a register's number is one greater
41736 than that of the previous register (either in the current feature or in
41737 a preceding feature); the first register in the target description
41738 defaults to zero. This register number is used to read or write
41739 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41740 packets, and registers appear in the @code{g} and @code{G} packets
41741 in order of increasing register number.
41744 Whether the register should be preserved across inferior function
41745 calls; this must be either @code{yes} or @code{no}. The default is
41746 @code{yes}, which is appropriate for most registers except for
41747 some system control registers; this is not related to the target's
41751 The type of the register. It may be a predefined type, a type
41752 defined in the current feature, or one of the special types @code{int}
41753 and @code{float}. @code{int} is an integer type of the correct size
41754 for @var{bitsize}, and @code{float} is a floating point type (in the
41755 architecture's normal floating point format) of the correct size for
41756 @var{bitsize}. The default is @code{int}.
41759 The register group to which this register belongs. It must
41760 be either @code{general}, @code{float}, or @code{vector}. If no
41761 @var{group} is specified, @value{GDBN} will not display the register
41762 in @code{info registers}.
41766 @node Predefined Target Types
41767 @section Predefined Target Types
41768 @cindex target descriptions, predefined types
41770 Type definitions in the self-description can build up composite types
41771 from basic building blocks, but can not define fundamental types. Instead,
41772 standard identifiers are provided by @value{GDBN} for the fundamental
41773 types. The currently supported types are:
41778 Boolean type, occupying a single bit.
41785 Signed integer types holding the specified number of bits.
41792 Unsigned integer types holding the specified number of bits.
41796 Pointers to unspecified code and data. The program counter and
41797 any dedicated return address register may be marked as code
41798 pointers; printing a code pointer converts it into a symbolic
41799 address. The stack pointer and any dedicated address registers
41800 may be marked as data pointers.
41803 Single precision IEEE floating point.
41806 Double precision IEEE floating point.
41809 The 12-byte extended precision format used by ARM FPA registers.
41812 The 10-byte extended precision format used by x87 registers.
41815 32bit @sc{eflags} register used by x86.
41818 32bit @sc{mxcsr} register used by x86.
41822 @node Enum Target Types
41823 @section Enum Target Types
41824 @cindex target descriptions, enum types
41826 Enum target types are useful in @samp{struct} and @samp{flags}
41827 register descriptions. @xref{Target Description Format}.
41829 Enum types have a name, size and a list of name/value pairs.
41832 <enum id="@var{id}" size="@var{size}">
41833 <evalue name="@var{name}" value="@var{value}"/>
41838 Enums must be defined before they are used.
41841 <enum id="levels_type" size="4">
41842 <evalue name="low" value="0"/>
41843 <evalue name="high" value="1"/>
41845 <flags id="flags_type" size="4">
41846 <field name="X" start="0"/>
41847 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41849 <reg name="flags" bitsize="32" type="flags_type"/>
41852 Given that description, a value of 3 for the @samp{flags} register
41853 would be printed as:
41856 (gdb) info register flags
41857 flags 0x3 [ X LEVEL=high ]
41860 @node Standard Target Features
41861 @section Standard Target Features
41862 @cindex target descriptions, standard features
41864 A target description must contain either no registers or all the
41865 target's registers. If the description contains no registers, then
41866 @value{GDBN} will assume a default register layout, selected based on
41867 the architecture. If the description contains any registers, the
41868 default layout will not be used; the standard registers must be
41869 described in the target description, in such a way that @value{GDBN}
41870 can recognize them.
41872 This is accomplished by giving specific names to feature elements
41873 which contain standard registers. @value{GDBN} will look for features
41874 with those names and verify that they contain the expected registers;
41875 if any known feature is missing required registers, or if any required
41876 feature is missing, @value{GDBN} will reject the target
41877 description. You can add additional registers to any of the
41878 standard features --- @value{GDBN} will display them just as if
41879 they were added to an unrecognized feature.
41881 This section lists the known features and their expected contents.
41882 Sample XML documents for these features are included in the
41883 @value{GDBN} source tree, in the directory @file{gdb/features}.
41885 Names recognized by @value{GDBN} should include the name of the
41886 company or organization which selected the name, and the overall
41887 architecture to which the feature applies; so e.g.@: the feature
41888 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41890 The names of registers are not case sensitive for the purpose
41891 of recognizing standard features, but @value{GDBN} will only display
41892 registers using the capitalization used in the description.
41895 * AArch64 Features::
41899 * MicroBlaze Features::
41903 * Nios II Features::
41904 * OpenRISC 1000 Features::
41905 * PowerPC Features::
41906 * S/390 and System z Features::
41912 @node AArch64 Features
41913 @subsection AArch64 Features
41914 @cindex target descriptions, AArch64 features
41916 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41917 targets. It should contain registers @samp{x0} through @samp{x30},
41918 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41920 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41921 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41925 @subsection ARC Features
41926 @cindex target descriptions, ARC Features
41928 ARC processors are highly configurable, so even core registers and their number
41929 are not completely predetermined. In addition flags and PC registers which are
41930 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41931 that one of the core registers features is present.
41932 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41934 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41935 targets with a normal register file. It should contain registers @samp{r0}
41936 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41937 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41938 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41939 @samp{ilink} and extension core registers are not available to read/write, when
41940 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41942 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41943 ARC HS targets with a reduced register file. It should contain registers
41944 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41945 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41946 This feature may contain register @samp{ilink} and any of extension core
41947 registers @samp{r32} through @samp{r59/acch}.
41949 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41950 targets with a normal register file. It should contain registers @samp{r0}
41951 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41952 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41953 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41954 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41955 registers are not available when debugging GNU/Linux applications. The only
41956 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41957 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41958 ARC v2, but @samp{ilink2} is optional on ARCompact.
41960 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41961 targets. It should contain registers @samp{pc} and @samp{status32}.
41964 @subsection ARM Features
41965 @cindex target descriptions, ARM features
41967 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41969 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41970 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41972 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41973 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41974 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41977 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41978 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41980 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41981 it should contain at least registers @samp{wR0} through @samp{wR15} and
41982 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41983 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41985 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41986 should contain at least registers @samp{d0} through @samp{d15}. If
41987 they are present, @samp{d16} through @samp{d31} should also be included.
41988 @value{GDBN} will synthesize the single-precision registers from
41989 halves of the double-precision registers.
41991 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41992 need to contain registers; it instructs @value{GDBN} to display the
41993 VFP double-precision registers as vectors and to synthesize the
41994 quad-precision registers from pairs of double-precision registers.
41995 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41996 be present and include 32 double-precision registers.
41998 @node i386 Features
41999 @subsection i386 Features
42000 @cindex target descriptions, i386 features
42002 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42003 targets. It should describe the following registers:
42007 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42009 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42011 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42012 @samp{fs}, @samp{gs}
42014 @samp{st0} through @samp{st7}
42016 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42017 @samp{foseg}, @samp{fooff} and @samp{fop}
42020 The register sets may be different, depending on the target.
42022 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42023 describe registers:
42027 @samp{xmm0} through @samp{xmm7} for i386
42029 @samp{xmm0} through @samp{xmm15} for amd64
42034 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42035 @samp{org.gnu.gdb.i386.sse} feature. It should
42036 describe the upper 128 bits of @sc{ymm} registers:
42040 @samp{ymm0h} through @samp{ymm7h} for i386
42042 @samp{ymm0h} through @samp{ymm15h} for amd64
42045 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42046 Memory Protection Extension (MPX). It should describe the following registers:
42050 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42052 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42055 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42056 describe a single register, @samp{orig_eax}.
42058 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42059 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42061 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42062 @samp{org.gnu.gdb.i386.avx} feature. It should
42063 describe additional @sc{xmm} registers:
42067 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42070 It should describe the upper 128 bits of additional @sc{ymm} registers:
42074 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42078 describe the upper 256 bits of @sc{zmm} registers:
42082 @samp{zmm0h} through @samp{zmm7h} for i386.
42084 @samp{zmm0h} through @samp{zmm15h} for amd64.
42088 describe the additional @sc{zmm} registers:
42092 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42095 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42096 describe a single register, @samp{pkru}. It is a 32-bit register
42097 valid for i386 and amd64.
42099 @node MicroBlaze Features
42100 @subsection MicroBlaze Features
42101 @cindex target descriptions, MicroBlaze features
42103 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42104 targets. It should contain registers @samp{r0} through @samp{r31},
42105 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42106 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42107 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42109 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42110 If present, it should contain registers @samp{rshr} and @samp{rslr}
42112 @node MIPS Features
42113 @subsection @acronym{MIPS} Features
42114 @cindex target descriptions, @acronym{MIPS} features
42116 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42117 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42118 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42121 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42122 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42123 registers. They may be 32-bit or 64-bit depending on the target.
42125 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42126 it may be optional in a future version of @value{GDBN}. It should
42127 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42128 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42130 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42131 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42132 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42133 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42135 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42136 contain a single register, @samp{restart}, which is used by the
42137 Linux kernel to control restartable syscalls.
42139 @node M68K Features
42140 @subsection M68K Features
42141 @cindex target descriptions, M68K features
42144 @item @samp{org.gnu.gdb.m68k.core}
42145 @itemx @samp{org.gnu.gdb.coldfire.core}
42146 @itemx @samp{org.gnu.gdb.fido.core}
42147 One of those features must be always present.
42148 The feature that is present determines which flavor of m68k is
42149 used. The feature that is present should contain registers
42150 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42151 @samp{sp}, @samp{ps} and @samp{pc}.
42153 @item @samp{org.gnu.gdb.coldfire.fp}
42154 This feature is optional. If present, it should contain registers
42155 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42159 @node NDS32 Features
42160 @subsection NDS32 Features
42161 @cindex target descriptions, NDS32 features
42163 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42164 targets. It should contain at least registers @samp{r0} through
42165 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42168 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42169 it should contain 64-bit double-precision floating-point registers
42170 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42171 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42173 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42174 registers are overlapped with the thirty-two 32-bit single-precision
42175 floating-point registers. The 32-bit single-precision registers, if
42176 not being listed explicitly, will be synthesized from halves of the
42177 overlapping 64-bit double-precision registers. Listing 32-bit
42178 single-precision registers explicitly is deprecated, and the
42179 support to it could be totally removed some day.
42181 @node Nios II Features
42182 @subsection Nios II Features
42183 @cindex target descriptions, Nios II features
42185 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42186 targets. It should contain the 32 core registers (@samp{zero},
42187 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42188 @samp{pc}, and the 16 control registers (@samp{status} through
42191 @node OpenRISC 1000 Features
42192 @subsection Openrisc 1000 Features
42193 @cindex target descriptions, OpenRISC 1000 features
42195 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42196 targets. It should contain the 32 general purpose registers (@samp{r0}
42197 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42199 @node PowerPC Features
42200 @subsection PowerPC Features
42201 @cindex target descriptions, PowerPC features
42203 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42204 targets. It should contain registers @samp{r0} through @samp{r31},
42205 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42206 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42208 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42209 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42211 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42212 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42215 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42216 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42217 will combine these registers with the floating point registers
42218 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42219 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42220 through @samp{vs63}, the set of vector registers for POWER7.
42222 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42223 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42224 @samp{spefscr}. SPE targets should provide 32-bit registers in
42225 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42226 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42227 these to present registers @samp{ev0} through @samp{ev31} to the
42230 @node S/390 and System z Features
42231 @subsection S/390 and System z Features
42232 @cindex target descriptions, S/390 features
42233 @cindex target descriptions, System z features
42235 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42236 System z targets. It should contain the PSW and the 16 general
42237 registers. In particular, System z targets should provide the 64-bit
42238 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42239 S/390 targets should provide the 32-bit versions of these registers.
42240 A System z target that runs in 31-bit addressing mode should provide
42241 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42242 register's upper halves @samp{r0h} through @samp{r15h}, and their
42243 lower halves @samp{r0l} through @samp{r15l}.
42245 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42246 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42249 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42250 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42252 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42253 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42254 targets and 32-bit otherwise. In addition, the feature may contain
42255 the @samp{last_break} register, whose width depends on the addressing
42256 mode, as well as the @samp{system_call} register, which is always
42259 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42260 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42261 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42263 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42264 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42265 combined by @value{GDBN} with the floating point registers @samp{f0}
42266 through @samp{f15} to present the 128-bit wide vector registers
42267 @samp{v0} through @samp{v15}. In addition, this feature should
42268 contain the 128-bit wide vector registers @samp{v16} through
42271 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42272 the 64-bit wide guarded-storage-control registers @samp{gsd},
42273 @samp{gssm}, and @samp{gsepla}.
42275 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42276 the 64-bit wide guarded-storage broadcast control registers
42277 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42279 @node Sparc Features
42280 @subsection Sparc Features
42281 @cindex target descriptions, sparc32 features
42282 @cindex target descriptions, sparc64 features
42283 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42284 targets. It should describe the following registers:
42288 @samp{g0} through @samp{g7}
42290 @samp{o0} through @samp{o7}
42292 @samp{l0} through @samp{l7}
42294 @samp{i0} through @samp{i7}
42297 They may be 32-bit or 64-bit depending on the target.
42299 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42300 targets. It should describe the following registers:
42304 @samp{f0} through @samp{f31}
42306 @samp{f32} through @samp{f62} for sparc64
42309 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42310 targets. It should describe the following registers:
42314 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42315 @samp{fsr}, and @samp{csr} for sparc32
42317 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42321 @node TIC6x Features
42322 @subsection TMS320C6x Features
42323 @cindex target descriptions, TIC6x features
42324 @cindex target descriptions, TMS320C6x features
42325 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42326 targets. It should contain registers @samp{A0} through @samp{A15},
42327 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42329 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42330 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42331 through @samp{B31}.
42333 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42334 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42336 @node Operating System Information
42337 @appendix Operating System Information
42338 @cindex operating system information
42344 Users of @value{GDBN} often wish to obtain information about the state of
42345 the operating system running on the target---for example the list of
42346 processes, or the list of open files. This section describes the
42347 mechanism that makes it possible. This mechanism is similar to the
42348 target features mechanism (@pxref{Target Descriptions}), but focuses
42349 on a different aspect of target.
42351 Operating system information is retrived from the target via the
42352 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42353 read}). The object name in the request should be @samp{osdata}, and
42354 the @var{annex} identifies the data to be fetched.
42357 @appendixsection Process list
42358 @cindex operating system information, process list
42360 When requesting the process list, the @var{annex} field in the
42361 @samp{qXfer} request should be @samp{processes}. The returned data is
42362 an XML document. The formal syntax of this document is defined in
42363 @file{gdb/features/osdata.dtd}.
42365 An example document is:
42368 <?xml version="1.0"?>
42369 <!DOCTYPE target SYSTEM "osdata.dtd">
42370 <osdata type="processes">
42372 <column name="pid">1</column>
42373 <column name="user">root</column>
42374 <column name="command">/sbin/init</column>
42375 <column name="cores">1,2,3</column>
42380 Each item should include a column whose name is @samp{pid}. The value
42381 of that column should identify the process on the target. The
42382 @samp{user} and @samp{command} columns are optional, and will be
42383 displayed by @value{GDBN}. The @samp{cores} column, if present,
42384 should contain a comma-separated list of cores that this process
42385 is running on. Target may provide additional columns,
42386 which @value{GDBN} currently ignores.
42388 @node Trace File Format
42389 @appendix Trace File Format
42390 @cindex trace file format
42392 The trace file comes in three parts: a header, a textual description
42393 section, and a trace frame section with binary data.
42395 The header has the form @code{\x7fTRACE0\n}. The first byte is
42396 @code{0x7f} so as to indicate that the file contains binary data,
42397 while the @code{0} is a version number that may have different values
42400 The description section consists of multiple lines of @sc{ascii} text
42401 separated by newline characters (@code{0xa}). The lines may include a
42402 variety of optional descriptive or context-setting information, such
42403 as tracepoint definitions or register set size. @value{GDBN} will
42404 ignore any line that it does not recognize. An empty line marks the end
42409 Specifies the size of a register block in bytes. This is equal to the
42410 size of a @code{g} packet payload in the remote protocol. @var{size}
42411 is an ascii decimal number. There should be only one such line in
42412 a single trace file.
42414 @item status @var{status}
42415 Trace status. @var{status} has the same format as a @code{qTStatus}
42416 remote packet reply. There should be only one such line in a single trace
42419 @item tp @var{payload}
42420 Tracepoint definition. The @var{payload} has the same format as
42421 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42422 may take multiple lines of definition, corresponding to the multiple
42425 @item tsv @var{payload}
42426 Trace state variable definition. The @var{payload} has the same format as
42427 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42428 may take multiple lines of definition, corresponding to the multiple
42431 @item tdesc @var{payload}
42432 Target description in XML format. The @var{payload} is a single line of
42433 the XML file. All such lines should be concatenated together to get
42434 the original XML file. This file is in the same format as @code{qXfer}
42435 @code{features} payload, and corresponds to the main @code{target.xml}
42436 file. Includes are not allowed.
42440 The trace frame section consists of a number of consecutive frames.
42441 Each frame begins with a two-byte tracepoint number, followed by a
42442 four-byte size giving the amount of data in the frame. The data in
42443 the frame consists of a number of blocks, each introduced by a
42444 character indicating its type (at least register, memory, and trace
42445 state variable). The data in this section is raw binary, not a
42446 hexadecimal or other encoding; its endianness matches the target's
42449 @c FIXME bi-arch may require endianness/arch info in description section
42452 @item R @var{bytes}
42453 Register block. The number and ordering of bytes matches that of a
42454 @code{g} packet in the remote protocol. Note that these are the
42455 actual bytes, in target order, not a hexadecimal encoding.
42457 @item M @var{address} @var{length} @var{bytes}...
42458 Memory block. This is a contiguous block of memory, at the 8-byte
42459 address @var{address}, with a 2-byte length @var{length}, followed by
42460 @var{length} bytes.
42462 @item V @var{number} @var{value}
42463 Trace state variable block. This records the 8-byte signed value
42464 @var{value} of trace state variable numbered @var{number}.
42468 Future enhancements of the trace file format may include additional types
42471 @node Index Section Format
42472 @appendix @code{.gdb_index} section format
42473 @cindex .gdb_index section format
42474 @cindex index section format
42476 This section documents the index section that is created by @code{save
42477 gdb-index} (@pxref{Index Files}). The index section is
42478 DWARF-specific; some knowledge of DWARF is assumed in this
42481 The mapped index file format is designed to be directly
42482 @code{mmap}able on any architecture. In most cases, a datum is
42483 represented using a little-endian 32-bit integer value, called an
42484 @code{offset_type}. Big endian machines must byte-swap the values
42485 before using them. Exceptions to this rule are noted. The data is
42486 laid out such that alignment is always respected.
42488 A mapped index consists of several areas, laid out in order.
42492 The file header. This is a sequence of values, of @code{offset_type}
42493 unless otherwise noted:
42497 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42498 Version 4 uses a different hashing function from versions 5 and 6.
42499 Version 6 includes symbols for inlined functions, whereas versions 4
42500 and 5 do not. Version 7 adds attributes to the CU indices in the
42501 symbol table. Version 8 specifies that symbols from DWARF type units
42502 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42503 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42505 @value{GDBN} will only read version 4, 5, or 6 indices
42506 by specifying @code{set use-deprecated-index-sections on}.
42507 GDB has a workaround for potentially broken version 7 indices so it is
42508 currently not flagged as deprecated.
42511 The offset, from the start of the file, of the CU list.
42514 The offset, from the start of the file, of the types CU list. Note
42515 that this area can be empty, in which case this offset will be equal
42516 to the next offset.
42519 The offset, from the start of the file, of the address area.
42522 The offset, from the start of the file, of the symbol table.
42525 The offset, from the start of the file, of the constant pool.
42529 The CU list. This is a sequence of pairs of 64-bit little-endian
42530 values, sorted by the CU offset. The first element in each pair is
42531 the offset of a CU in the @code{.debug_info} section. The second
42532 element in each pair is the length of that CU. References to a CU
42533 elsewhere in the map are done using a CU index, which is just the
42534 0-based index into this table. Note that if there are type CUs, then
42535 conceptually CUs and type CUs form a single list for the purposes of
42539 The types CU list. This is a sequence of triplets of 64-bit
42540 little-endian values. In a triplet, the first value is the CU offset,
42541 the second value is the type offset in the CU, and the third value is
42542 the type signature. The types CU list is not sorted.
42545 The address area. The address area consists of a sequence of address
42546 entries. Each address entry has three elements:
42550 The low address. This is a 64-bit little-endian value.
42553 The high address. This is a 64-bit little-endian value. Like
42554 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42557 The CU index. This is an @code{offset_type} value.
42561 The symbol table. This is an open-addressed hash table. The size of
42562 the hash table is always a power of 2.
42564 Each slot in the hash table consists of a pair of @code{offset_type}
42565 values. The first value is the offset of the symbol's name in the
42566 constant pool. The second value is the offset of the CU vector in the
42569 If both values are 0, then this slot in the hash table is empty. This
42570 is ok because while 0 is a valid constant pool index, it cannot be a
42571 valid index for both a string and a CU vector.
42573 The hash value for a table entry is computed by applying an
42574 iterative hash function to the symbol's name. Starting with an
42575 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42576 the string is incorporated into the hash using the formula depending on the
42581 The formula is @code{r = r * 67 + c - 113}.
42583 @item Versions 5 to 7
42584 The formula is @code{r = r * 67 + tolower (c) - 113}.
42587 The terminating @samp{\0} is not incorporated into the hash.
42589 The step size used in the hash table is computed via
42590 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42591 value, and @samp{size} is the size of the hash table. The step size
42592 is used to find the next candidate slot when handling a hash
42595 The names of C@t{++} symbols in the hash table are canonicalized. We
42596 don't currently have a simple description of the canonicalization
42597 algorithm; if you intend to create new index sections, you must read
42601 The constant pool. This is simply a bunch of bytes. It is organized
42602 so that alignment is correct: CU vectors are stored first, followed by
42605 A CU vector in the constant pool is a sequence of @code{offset_type}
42606 values. The first value is the number of CU indices in the vector.
42607 Each subsequent value is the index and symbol attributes of a CU in
42608 the CU list. This element in the hash table is used to indicate which
42609 CUs define the symbol and how the symbol is used.
42610 See below for the format of each CU index+attributes entry.
42612 A string in the constant pool is zero-terminated.
42615 Attributes were added to CU index values in @code{.gdb_index} version 7.
42616 If a symbol has multiple uses within a CU then there is one
42617 CU index+attributes value for each use.
42619 The format of each CU index+attributes entry is as follows
42625 This is the index of the CU in the CU list.
42627 These bits are reserved for future purposes and must be zero.
42629 The kind of the symbol in the CU.
42633 This value is reserved and should not be used.
42634 By reserving zero the full @code{offset_type} value is backwards compatible
42635 with previous versions of the index.
42637 The symbol is a type.
42639 The symbol is a variable or an enum value.
42641 The symbol is a function.
42643 Any other kind of symbol.
42645 These values are reserved.
42649 This bit is zero if the value is global and one if it is static.
42651 The determination of whether a symbol is global or static is complicated.
42652 The authorative reference is the file @file{dwarf2read.c} in
42653 @value{GDBN} sources.
42657 This pseudo-code describes the computation of a symbol's kind and
42658 global/static attributes in the index.
42661 is_external = get_attribute (die, DW_AT_external);
42662 language = get_attribute (cu_die, DW_AT_language);
42665 case DW_TAG_typedef:
42666 case DW_TAG_base_type:
42667 case DW_TAG_subrange_type:
42671 case DW_TAG_enumerator:
42673 is_static = language != CPLUS;
42675 case DW_TAG_subprogram:
42677 is_static = ! (is_external || language == ADA);
42679 case DW_TAG_constant:
42681 is_static = ! is_external;
42683 case DW_TAG_variable:
42685 is_static = ! is_external;
42687 case DW_TAG_namespace:
42691 case DW_TAG_class_type:
42692 case DW_TAG_interface_type:
42693 case DW_TAG_structure_type:
42694 case DW_TAG_union_type:
42695 case DW_TAG_enumeration_type:
42697 is_static = language != CPLUS;
42705 @appendix Manual pages
42709 * gdb man:: The GNU Debugger man page
42710 * gdbserver man:: Remote Server for the GNU Debugger man page
42711 * gcore man:: Generate a core file of a running program
42712 * gdbinit man:: gdbinit scripts
42718 @c man title gdb The GNU Debugger
42720 @c man begin SYNOPSIS gdb
42721 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42722 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42723 [@option{-b}@w{ }@var{bps}]
42724 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42725 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42726 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42727 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42728 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42731 @c man begin DESCRIPTION gdb
42732 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42733 going on ``inside'' another program while it executes -- or what another
42734 program was doing at the moment it crashed.
42736 @value{GDBN} can do four main kinds of things (plus other things in support of
42737 these) to help you catch bugs in the act:
42741 Start your program, specifying anything that might affect its behavior.
42744 Make your program stop on specified conditions.
42747 Examine what has happened, when your program has stopped.
42750 Change things in your program, so you can experiment with correcting the
42751 effects of one bug and go on to learn about another.
42754 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42757 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42758 commands from the terminal until you tell it to exit with the @value{GDBN}
42759 command @code{quit}. You can get online help from @value{GDBN} itself
42760 by using the command @code{help}.
42762 You can run @code{gdb} with no arguments or options; but the most
42763 usual way to start @value{GDBN} is with one argument or two, specifying an
42764 executable program as the argument:
42770 You can also start with both an executable program and a core file specified:
42776 You can, instead, specify a process ID as a second argument, if you want
42777 to debug a running process:
42785 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42786 named @file{1234}; @value{GDBN} does check for a core file first).
42787 With option @option{-p} you can omit the @var{program} filename.
42789 Here are some of the most frequently needed @value{GDBN} commands:
42791 @c pod2man highlights the right hand side of the @item lines.
42793 @item break [@var{file}:]@var{function}
42794 Set a breakpoint at @var{function} (in @var{file}).
42796 @item run [@var{arglist}]
42797 Start your program (with @var{arglist}, if specified).
42800 Backtrace: display the program stack.
42802 @item print @var{expr}
42803 Display the value of an expression.
42806 Continue running your program (after stopping, e.g. at a breakpoint).
42809 Execute next program line (after stopping); step @emph{over} any
42810 function calls in the line.
42812 @item edit [@var{file}:]@var{function}
42813 look at the program line where it is presently stopped.
42815 @item list [@var{file}:]@var{function}
42816 type the text of the program in the vicinity of where it is presently stopped.
42819 Execute next program line (after stopping); step @emph{into} any
42820 function calls in the line.
42822 @item help [@var{name}]
42823 Show information about @value{GDBN} command @var{name}, or general information
42824 about using @value{GDBN}.
42827 Exit from @value{GDBN}.
42831 For full details on @value{GDBN},
42832 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42833 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42834 as the @code{gdb} entry in the @code{info} program.
42838 @c man begin OPTIONS gdb
42839 Any arguments other than options specify an executable
42840 file and core file (or process ID); that is, the first argument
42841 encountered with no
42842 associated option flag is equivalent to a @option{-se} option, and the second,
42843 if any, is equivalent to a @option{-c} option if it's the name of a file.
42845 both long and short forms; both are shown here. The long forms are also
42846 recognized if you truncate them, so long as enough of the option is
42847 present to be unambiguous. (If you prefer, you can flag option
42848 arguments with @option{+} rather than @option{-}, though we illustrate the
42849 more usual convention.)
42851 All the options and command line arguments you give are processed
42852 in sequential order. The order makes a difference when the @option{-x}
42858 List all options, with brief explanations.
42860 @item -symbols=@var{file}
42861 @itemx -s @var{file}
42862 Read symbol table from file @var{file}.
42865 Enable writing into executable and core files.
42867 @item -exec=@var{file}
42868 @itemx -e @var{file}
42869 Use file @var{file} as the executable file to execute when
42870 appropriate, and for examining pure data in conjunction with a core
42873 @item -se=@var{file}
42874 Read symbol table from file @var{file} and use it as the executable
42877 @item -core=@var{file}
42878 @itemx -c @var{file}
42879 Use file @var{file} as a core dump to examine.
42881 @item -command=@var{file}
42882 @itemx -x @var{file}
42883 Execute @value{GDBN} commands from file @var{file}.
42885 @item -ex @var{command}
42886 Execute given @value{GDBN} @var{command}.
42888 @item -directory=@var{directory}
42889 @itemx -d @var{directory}
42890 Add @var{directory} to the path to search for source files.
42893 Do not execute commands from @file{~/.gdbinit}.
42897 Do not execute commands from any @file{.gdbinit} initialization files.
42901 ``Quiet''. Do not print the introductory and copyright messages. These
42902 messages are also suppressed in batch mode.
42905 Run in batch mode. Exit with status @code{0} after processing all the command
42906 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42907 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42908 commands in the command files.
42910 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42911 download and run a program on another computer; in order to make this
42912 more useful, the message
42915 Program exited normally.
42919 (which is ordinarily issued whenever a program running under @value{GDBN} control
42920 terminates) is not issued when running in batch mode.
42922 @item -cd=@var{directory}
42923 Run @value{GDBN} using @var{directory} as its working directory,
42924 instead of the current directory.
42928 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42929 @value{GDBN} to output the full file name and line number in a standard,
42930 recognizable fashion each time a stack frame is displayed (which
42931 includes each time the program stops). This recognizable format looks
42932 like two @samp{\032} characters, followed by the file name, line number
42933 and character position separated by colons, and a newline. The
42934 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42935 characters as a signal to display the source code for the frame.
42938 Set the line speed (baud rate or bits per second) of any serial
42939 interface used by @value{GDBN} for remote debugging.
42941 @item -tty=@var{device}
42942 Run using @var{device} for your program's standard input and output.
42946 @c man begin SEEALSO gdb
42948 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42949 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42950 documentation are properly installed at your site, the command
42957 should give you access to the complete manual.
42959 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42960 Richard M. Stallman and Roland H. Pesch, July 1991.
42964 @node gdbserver man
42965 @heading gdbserver man
42967 @c man title gdbserver Remote Server for the GNU Debugger
42969 @c man begin SYNOPSIS gdbserver
42970 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42972 gdbserver --attach @var{comm} @var{pid}
42974 gdbserver --multi @var{comm}
42978 @c man begin DESCRIPTION gdbserver
42979 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42980 than the one which is running the program being debugged.
42983 @subheading Usage (server (target) side)
42986 Usage (server (target) side):
42989 First, you need to have a copy of the program you want to debug put onto
42990 the target system. The program can be stripped to save space if needed, as
42991 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42992 the @value{GDBN} running on the host system.
42994 To use the server, you log on to the target system, and run the @command{gdbserver}
42995 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42996 your program, and (c) its arguments. The general syntax is:
42999 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43002 For example, using a serial port, you might say:
43006 @c @file would wrap it as F</dev/com1>.
43007 target> gdbserver /dev/com1 emacs foo.txt
43010 target> gdbserver @file{/dev/com1} emacs foo.txt
43014 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43015 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43016 waits patiently for the host @value{GDBN} to communicate with it.
43018 To use a TCP connection, you could say:
43021 target> gdbserver host:2345 emacs foo.txt
43024 This says pretty much the same thing as the last example, except that we are
43025 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43026 that we are expecting to see a TCP connection from @code{host} to local TCP port
43027 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43028 want for the port number as long as it does not conflict with any existing TCP
43029 ports on the target system. This same port number must be used in the host
43030 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43031 you chose a port number that conflicts with another service, @command{gdbserver} will
43032 print an error message and exit.
43034 @command{gdbserver} can also attach to running programs.
43035 This is accomplished via the @option{--attach} argument. The syntax is:
43038 target> gdbserver --attach @var{comm} @var{pid}
43041 @var{pid} is the process ID of a currently running process. It isn't
43042 necessary to point @command{gdbserver} at a binary for the running process.
43044 To start @code{gdbserver} without supplying an initial command to run
43045 or process ID to attach, use the @option{--multi} command line option.
43046 In such case you should connect using @kbd{target extended-remote} to start
43047 the program you want to debug.
43050 target> gdbserver --multi @var{comm}
43054 @subheading Usage (host side)
43060 You need an unstripped copy of the target program on your host system, since
43061 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43062 would, with the target program as the first argument. (You may need to use the
43063 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43064 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43065 new command you need to know about is @code{target remote}
43066 (or @code{target extended-remote}). Its argument is either
43067 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43068 descriptor. For example:
43072 @c @file would wrap it as F</dev/ttyb>.
43073 (gdb) target remote /dev/ttyb
43076 (gdb) target remote @file{/dev/ttyb}
43081 communicates with the server via serial line @file{/dev/ttyb}, and:
43084 (gdb) target remote the-target:2345
43088 communicates via a TCP connection to port 2345 on host `the-target', where
43089 you previously started up @command{gdbserver} with the same port number. Note that for
43090 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43091 command, otherwise you may get an error that looks something like
43092 `Connection refused'.
43094 @command{gdbserver} can also debug multiple inferiors at once,
43097 the @value{GDBN} manual in node @code{Inferiors and Programs}
43098 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43101 @ref{Inferiors and Programs}.
43103 In such case use the @code{extended-remote} @value{GDBN} command variant:
43106 (gdb) target extended-remote the-target:2345
43109 The @command{gdbserver} option @option{--multi} may or may not be used in such
43113 @c man begin OPTIONS gdbserver
43114 There are three different modes for invoking @command{gdbserver}:
43119 Debug a specific program specified by its program name:
43122 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43125 The @var{comm} parameter specifies how should the server communicate
43126 with @value{GDBN}; it is either a device name (to use a serial line),
43127 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43128 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43129 debug in @var{prog}. Any remaining arguments will be passed to the
43130 program verbatim. When the program exits, @value{GDBN} will close the
43131 connection, and @code{gdbserver} will exit.
43134 Debug a specific program by specifying the process ID of a running
43138 gdbserver --attach @var{comm} @var{pid}
43141 The @var{comm} parameter is as described above. Supply the process ID
43142 of a running program in @var{pid}; @value{GDBN} will do everything
43143 else. Like with the previous mode, when the process @var{pid} exits,
43144 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43147 Multi-process mode -- debug more than one program/process:
43150 gdbserver --multi @var{comm}
43153 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43154 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43155 close the connection when a process being debugged exits, so you can
43156 debug several processes in the same session.
43159 In each of the modes you may specify these options:
43164 List all options, with brief explanations.
43167 This option causes @command{gdbserver} to print its version number and exit.
43170 @command{gdbserver} will attach to a running program. The syntax is:
43173 target> gdbserver --attach @var{comm} @var{pid}
43176 @var{pid} is the process ID of a currently running process. It isn't
43177 necessary to point @command{gdbserver} at a binary for the running process.
43180 To start @code{gdbserver} without supplying an initial command to run
43181 or process ID to attach, use this command line option.
43182 Then you can connect using @kbd{target extended-remote} and start
43183 the program you want to debug. The syntax is:
43186 target> gdbserver --multi @var{comm}
43190 Instruct @code{gdbserver} to display extra status information about the debugging
43192 This option is intended for @code{gdbserver} development and for bug reports to
43195 @item --remote-debug
43196 Instruct @code{gdbserver} to display remote protocol debug output.
43197 This option is intended for @code{gdbserver} development and for bug reports to
43200 @item --debug-format=option1@r{[},option2,...@r{]}
43201 Instruct @code{gdbserver} to include extra information in each line
43202 of debugging output.
43203 @xref{Other Command-Line Arguments for gdbserver}.
43206 Specify a wrapper to launch programs
43207 for debugging. The option should be followed by the name of the
43208 wrapper, then any command-line arguments to pass to the wrapper, then
43209 @kbd{--} indicating the end of the wrapper arguments.
43212 By default, @command{gdbserver} keeps the listening TCP port open, so that
43213 additional connections are possible. However, if you start @code{gdbserver}
43214 with the @option{--once} option, it will stop listening for any further
43215 connection attempts after connecting to the first @value{GDBN} session.
43217 @c --disable-packet is not documented for users.
43219 @c --disable-randomization and --no-disable-randomization are superseded by
43220 @c QDisableRandomization.
43225 @c man begin SEEALSO gdbserver
43227 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43228 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43229 documentation are properly installed at your site, the command
43235 should give you access to the complete manual.
43237 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43238 Richard M. Stallman and Roland H. Pesch, July 1991.
43245 @c man title gcore Generate a core file of a running program
43248 @c man begin SYNOPSIS gcore
43249 gcore [-a] [-o @var{filename}] @var{pid}
43253 @c man begin DESCRIPTION gcore
43254 Generate a core dump of a running program with process ID @var{pid}.
43255 Produced file is equivalent to a kernel produced core file as if the process
43256 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43257 limit). Unlike after a crash, after @command{gcore} the program remains
43258 running without any change.
43261 @c man begin OPTIONS gcore
43264 Dump all memory mappings. The actual effect of this option depends on
43265 the Operating System. On @sc{gnu}/Linux, it will disable
43266 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43267 enable @code{dump-excluded-mappings} (@pxref{set
43268 dump-excluded-mappings}).
43270 @item -o @var{filename}
43271 The optional argument
43272 @var{filename} specifies the file name where to put the core dump.
43273 If not specified, the file name defaults to @file{core.@var{pid}},
43274 where @var{pid} is the running program process ID.
43278 @c man begin SEEALSO gcore
43280 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43281 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43282 documentation are properly installed at your site, the command
43289 should give you access to the complete manual.
43291 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43292 Richard M. Stallman and Roland H. Pesch, July 1991.
43299 @c man title gdbinit GDB initialization scripts
43302 @c man begin SYNOPSIS gdbinit
43303 @ifset SYSTEM_GDBINIT
43304 @value{SYSTEM_GDBINIT}
43313 @c man begin DESCRIPTION gdbinit
43314 These files contain @value{GDBN} commands to automatically execute during
43315 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43318 the @value{GDBN} manual in node @code{Sequences}
43319 -- shell command @code{info -f gdb -n Sequences}.
43325 Please read more in
43327 the @value{GDBN} manual in node @code{Startup}
43328 -- shell command @code{info -f gdb -n Startup}.
43335 @ifset SYSTEM_GDBINIT
43336 @item @value{SYSTEM_GDBINIT}
43338 @ifclear SYSTEM_GDBINIT
43339 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43341 System-wide initialization file. It is executed unless user specified
43342 @value{GDBN} option @code{-nx} or @code{-n}.
43345 the @value{GDBN} manual in node @code{System-wide configuration}
43346 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43349 @ref{System-wide configuration}.
43353 User initialization file. It is executed unless user specified
43354 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43357 Initialization file for current directory. It may need to be enabled with
43358 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43361 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43362 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43365 @ref{Init File in the Current Directory}.
43370 @c man begin SEEALSO gdbinit
43372 gdb(1), @code{info -f gdb -n Startup}
43374 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43375 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43376 documentation are properly installed at your site, the command
43382 should give you access to the complete manual.
43384 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43385 Richard M. Stallman and Roland H. Pesch, July 1991.
43391 @node GNU Free Documentation License
43392 @appendix GNU Free Documentation License
43395 @node Concept Index
43396 @unnumbered Concept Index
43400 @node Command and Variable Index
43401 @unnumbered Command, Variable, and Function Index
43406 % I think something like @@colophon should be in texinfo. In the
43408 \long\def\colophon{\hbox to0pt{}\vfill
43409 \centerline{The body of this manual is set in}
43410 \centerline{\fontname\tenrm,}
43411 \centerline{with headings in {\bf\fontname\tenbf}}
43412 \centerline{and examples in {\tt\fontname\tentt}.}
43413 \centerline{{\it\fontname\tenit\/},}
43414 \centerline{{\bf\fontname\tenbf}, and}
43415 \centerline{{\sl\fontname\tensl\/}}
43416 \centerline{are used for emphasis.}\vfill}
43418 % Blame: doc@@cygnus.com, 1991.