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}.
17222 @item ptype[/@var{flags}] [@var{arg}]
17223 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17224 detailed description of the type, instead of just the name of the type.
17225 @xref{Expressions, ,Expressions}.
17227 Contrary to @code{whatis}, @code{ptype} always unrolls any
17228 @code{typedef}s in its argument declaration, whether the argument is
17229 a variable, expression, or a data type. This means that @code{ptype}
17230 of a variable or an expression will not print literally its type as
17231 present in the source code---use @code{whatis} for that. @code{typedef}s at
17232 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17233 fields, methods and inner @code{class typedef}s of @code{struct}s,
17234 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17236 For example, for this variable declaration:
17239 typedef double real_t;
17240 struct complex @{ real_t real; double imag; @};
17241 typedef struct complex complex_t;
17243 real_t *real_pointer_var;
17247 the two commands give this output:
17251 (@value{GDBP}) whatis var
17253 (@value{GDBP}) ptype var
17254 type = struct complex @{
17258 (@value{GDBP}) whatis complex_t
17259 type = struct complex
17260 (@value{GDBP}) whatis struct complex
17261 type = struct complex
17262 (@value{GDBP}) ptype struct complex
17263 type = struct complex @{
17267 (@value{GDBP}) whatis real_pointer_var
17269 (@value{GDBP}) ptype real_pointer_var
17275 As with @code{whatis}, using @code{ptype} without an argument refers to
17276 the type of @code{$}, the last value in the value history.
17278 @cindex incomplete type
17279 Sometimes, programs use opaque data types or incomplete specifications
17280 of complex data structure. If the debug information included in the
17281 program does not allow @value{GDBN} to display a full declaration of
17282 the data type, it will say @samp{<incomplete type>}. For example,
17283 given these declarations:
17287 struct foo *fooptr;
17291 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17294 (@value{GDBP}) ptype foo
17295 $1 = <incomplete type>
17299 ``Incomplete type'' is C terminology for data types that are not
17300 completely specified.
17302 @cindex unknown type
17303 Othertimes, information about a variable's type is completely absent
17304 from the debug information included in the program. This most often
17305 happens when the program or library where the variable is defined
17306 includes no debug information at all. @value{GDBN} knows the variable
17307 exists from inspecting the linker/loader symbol table (e.g., the ELF
17308 dynamic symbol table), but such symbols do not contain type
17309 information. Inspecting the type of a (global) variable for which
17310 @value{GDBN} has no type information shows:
17313 (@value{GDBP}) ptype var
17314 type = <data variable, no debug info>
17317 @xref{Variables, no debug info variables}, for how to print the values
17321 @item info types @var{regexp}
17323 Print a brief description of all types whose names match the regular
17324 expression @var{regexp} (or all types in your program, if you supply
17325 no argument). Each complete typename is matched as though it were a
17326 complete line; thus, @samp{i type value} gives information on all
17327 types in your program whose names include the string @code{value}, but
17328 @samp{i type ^value$} gives information only on types whose complete
17329 name is @code{value}.
17331 This command differs from @code{ptype} in two ways: first, like
17332 @code{whatis}, it does not print a detailed description; second, it
17333 lists all source files where a type is defined.
17335 @kindex info type-printers
17336 @item info type-printers
17337 Versions of @value{GDBN} that ship with Python scripting enabled may
17338 have ``type printers'' available. When using @command{ptype} or
17339 @command{whatis}, these printers are consulted when the name of a type
17340 is needed. @xref{Type Printing API}, for more information on writing
17343 @code{info type-printers} displays all the available type printers.
17345 @kindex enable type-printer
17346 @kindex disable type-printer
17347 @item enable type-printer @var{name}@dots{}
17348 @item disable type-printer @var{name}@dots{}
17349 These commands can be used to enable or disable type printers.
17352 @cindex local variables
17353 @item info scope @var{location}
17354 List all the variables local to a particular scope. This command
17355 accepts a @var{location} argument---a function name, a source line, or
17356 an address preceded by a @samp{*}, and prints all the variables local
17357 to the scope defined by that location. (@xref{Specify Location}, for
17358 details about supported forms of @var{location}.) For example:
17361 (@value{GDBP}) @b{info scope command_line_handler}
17362 Scope for command_line_handler:
17363 Symbol rl is an argument at stack/frame offset 8, length 4.
17364 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17365 Symbol linelength is in static storage at address 0x150a1c, length 4.
17366 Symbol p is a local variable in register $esi, length 4.
17367 Symbol p1 is a local variable in register $ebx, length 4.
17368 Symbol nline is a local variable in register $edx, length 4.
17369 Symbol repeat is a local variable at frame offset -8, length 4.
17373 This command is especially useful for determining what data to collect
17374 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17377 @kindex info source
17379 Show information about the current source file---that is, the source file for
17380 the function containing the current point of execution:
17383 the name of the source file, and the directory containing it,
17385 the directory it was compiled in,
17387 its length, in lines,
17389 which programming language it is written in,
17391 if the debug information provides it, the program that compiled the file
17392 (which may include, e.g., the compiler version and command line arguments),
17394 whether the executable includes debugging information for that file, and
17395 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17397 whether the debugging information includes information about
17398 preprocessor macros.
17402 @kindex info sources
17404 Print the names of all source files in your program for which there is
17405 debugging information, organized into two lists: files whose symbols
17406 have already been read, and files whose symbols will be read when needed.
17408 @kindex info functions
17409 @item info functions
17410 Print the names and data types of all defined functions.
17412 @item info functions @var{regexp}
17413 Print the names and data types of all defined functions
17414 whose names contain a match for regular expression @var{regexp}.
17415 Thus, @samp{info fun step} finds all functions whose names
17416 include @code{step}; @samp{info fun ^step} finds those whose names
17417 start with @code{step}. If a function name contains characters
17418 that conflict with the regular expression language (e.g.@:
17419 @samp{operator*()}), they may be quoted with a backslash.
17421 @kindex info variables
17422 @item info variables
17423 Print the names and data types of all variables that are defined
17424 outside of functions (i.e.@: excluding local variables).
17426 @item info variables @var{regexp}
17427 Print the names and data types of all variables (except for local
17428 variables) whose names contain a match for regular expression
17431 @kindex info classes
17432 @cindex Objective-C, classes and selectors
17434 @itemx info classes @var{regexp}
17435 Display all Objective-C classes in your program, or
17436 (with the @var{regexp} argument) all those matching a particular regular
17439 @kindex info selectors
17440 @item info selectors
17441 @itemx info selectors @var{regexp}
17442 Display all Objective-C selectors in your program, or
17443 (with the @var{regexp} argument) all those matching a particular regular
17447 This was never implemented.
17448 @kindex info methods
17450 @itemx info methods @var{regexp}
17451 The @code{info methods} command permits the user to examine all defined
17452 methods within C@t{++} program, or (with the @var{regexp} argument) a
17453 specific set of methods found in the various C@t{++} classes. Many
17454 C@t{++} classes provide a large number of methods. Thus, the output
17455 from the @code{ptype} command can be overwhelming and hard to use. The
17456 @code{info-methods} command filters the methods, printing only those
17457 which match the regular-expression @var{regexp}.
17460 @cindex opaque data types
17461 @kindex set opaque-type-resolution
17462 @item set opaque-type-resolution on
17463 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17464 declared as a pointer to a @code{struct}, @code{class}, or
17465 @code{union}---for example, @code{struct MyType *}---that is used in one
17466 source file although the full declaration of @code{struct MyType} is in
17467 another source file. The default is on.
17469 A change in the setting of this subcommand will not take effect until
17470 the next time symbols for a file are loaded.
17472 @item set opaque-type-resolution off
17473 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17474 is printed as follows:
17476 @{<no data fields>@}
17479 @kindex show opaque-type-resolution
17480 @item show opaque-type-resolution
17481 Show whether opaque types are resolved or not.
17483 @kindex set print symbol-loading
17484 @cindex print messages when symbols are loaded
17485 @item set print symbol-loading
17486 @itemx set print symbol-loading full
17487 @itemx set print symbol-loading brief
17488 @itemx set print symbol-loading off
17489 The @code{set print symbol-loading} command allows you to control the
17490 printing of messages when @value{GDBN} loads symbol information.
17491 By default a message is printed for the executable and one for each
17492 shared library, and normally this is what you want. However, when
17493 debugging apps with large numbers of shared libraries these messages
17495 When set to @code{brief} a message is printed for each executable,
17496 and when @value{GDBN} loads a collection of shared libraries at once
17497 it will only print one message regardless of the number of shared
17498 libraries. When set to @code{off} no messages are printed.
17500 @kindex show print symbol-loading
17501 @item show print symbol-loading
17502 Show whether messages will be printed when a @value{GDBN} command
17503 entered from the keyboard causes symbol information to be loaded.
17505 @kindex maint print symbols
17506 @cindex symbol dump
17507 @kindex maint print psymbols
17508 @cindex partial symbol dump
17509 @kindex maint print msymbols
17510 @cindex minimal symbol dump
17511 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17512 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17513 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17514 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17515 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17516 Write a dump of debugging symbol data into the file @var{filename} or
17517 the terminal if @var{filename} is unspecified.
17518 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17520 If @code{-pc @var{address}} is specified, only dump symbols for the file
17521 with code at that address. Note that @var{address} may be a symbol like
17523 If @code{-source @var{source}} is specified, only dump symbols for that
17526 These commands are used to debug the @value{GDBN} symbol-reading code.
17527 These commands do not modify internal @value{GDBN} state, therefore
17528 @samp{maint print symbols} will only print symbols for already expanded symbol
17530 You can use the command @code{info sources} to find out which files these are.
17531 If you use @samp{maint print psymbols} instead, the dump shows information
17532 about symbols that @value{GDBN} only knows partially---that is, symbols
17533 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17534 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17537 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17538 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17540 @kindex maint info symtabs
17541 @kindex maint info psymtabs
17542 @cindex listing @value{GDBN}'s internal symbol tables
17543 @cindex symbol tables, listing @value{GDBN}'s internal
17544 @cindex full symbol tables, listing @value{GDBN}'s internal
17545 @cindex partial symbol tables, listing @value{GDBN}'s internal
17546 @item maint info symtabs @r{[} @var{regexp} @r{]}
17547 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17549 List the @code{struct symtab} or @code{struct partial_symtab}
17550 structures whose names match @var{regexp}. If @var{regexp} is not
17551 given, list them all. The output includes expressions which you can
17552 copy into a @value{GDBN} debugging this one to examine a particular
17553 structure in more detail. For example:
17556 (@value{GDBP}) maint info psymtabs dwarf2read
17557 @{ objfile /home/gnu/build/gdb/gdb
17558 ((struct objfile *) 0x82e69d0)
17559 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17560 ((struct partial_symtab *) 0x8474b10)
17563 text addresses 0x814d3c8 -- 0x8158074
17564 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17565 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17566 dependencies (none)
17569 (@value{GDBP}) maint info symtabs
17573 We see that there is one partial symbol table whose filename contains
17574 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17575 and we see that @value{GDBN} has not read in any symtabs yet at all.
17576 If we set a breakpoint on a function, that will cause @value{GDBN} to
17577 read the symtab for the compilation unit containing that function:
17580 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17581 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17583 (@value{GDBP}) maint info symtabs
17584 @{ objfile /home/gnu/build/gdb/gdb
17585 ((struct objfile *) 0x82e69d0)
17586 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17587 ((struct symtab *) 0x86c1f38)
17590 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17591 linetable ((struct linetable *) 0x8370fa0)
17592 debugformat DWARF 2
17598 @kindex maint info line-table
17599 @cindex listing @value{GDBN}'s internal line tables
17600 @cindex line tables, listing @value{GDBN}'s internal
17601 @item maint info line-table @r{[} @var{regexp} @r{]}
17603 List the @code{struct linetable} from all @code{struct symtab}
17604 instances whose name matches @var{regexp}. If @var{regexp} is not
17605 given, list the @code{struct linetable} from all @code{struct symtab}.
17607 @kindex maint set symbol-cache-size
17608 @cindex symbol cache size
17609 @item maint set symbol-cache-size @var{size}
17610 Set the size of the symbol cache to @var{size}.
17611 The default size is intended to be good enough for debugging
17612 most applications. This option exists to allow for experimenting
17613 with different sizes.
17615 @kindex maint show symbol-cache-size
17616 @item maint show symbol-cache-size
17617 Show the size of the symbol cache.
17619 @kindex maint print symbol-cache
17620 @cindex symbol cache, printing its contents
17621 @item maint print symbol-cache
17622 Print the contents of the symbol cache.
17623 This is useful when debugging symbol cache issues.
17625 @kindex maint print symbol-cache-statistics
17626 @cindex symbol cache, printing usage statistics
17627 @item maint print symbol-cache-statistics
17628 Print symbol cache usage statistics.
17629 This helps determine how well the cache is being utilized.
17631 @kindex maint flush-symbol-cache
17632 @cindex symbol cache, flushing
17633 @item maint flush-symbol-cache
17634 Flush the contents of the symbol cache, all entries are removed.
17635 This command is useful when debugging the symbol cache.
17636 It is also useful when collecting performance data.
17641 @chapter Altering Execution
17643 Once you think you have found an error in your program, you might want to
17644 find out for certain whether correcting the apparent error would lead to
17645 correct results in the rest of the run. You can find the answer by
17646 experiment, using the @value{GDBN} features for altering execution of the
17649 For example, you can store new values into variables or memory
17650 locations, give your program a signal, restart it at a different
17651 address, or even return prematurely from a function.
17654 * Assignment:: Assignment to variables
17655 * Jumping:: Continuing at a different address
17656 * Signaling:: Giving your program a signal
17657 * Returning:: Returning from a function
17658 * Calling:: Calling your program's functions
17659 * Patching:: Patching your program
17660 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17664 @section Assignment to Variables
17667 @cindex setting variables
17668 To alter the value of a variable, evaluate an assignment expression.
17669 @xref{Expressions, ,Expressions}. For example,
17676 stores the value 4 into the variable @code{x}, and then prints the
17677 value of the assignment expression (which is 4).
17678 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17679 information on operators in supported languages.
17681 @kindex set variable
17682 @cindex variables, setting
17683 If you are not interested in seeing the value of the assignment, use the
17684 @code{set} command instead of the @code{print} command. @code{set} is
17685 really the same as @code{print} except that the expression's value is
17686 not printed and is not put in the value history (@pxref{Value History,
17687 ,Value History}). The expression is evaluated only for its effects.
17689 If the beginning of the argument string of the @code{set} command
17690 appears identical to a @code{set} subcommand, use the @code{set
17691 variable} command instead of just @code{set}. This command is identical
17692 to @code{set} except for its lack of subcommands. For example, if your
17693 program has a variable @code{width}, you get an error if you try to set
17694 a new value with just @samp{set width=13}, because @value{GDBN} has the
17695 command @code{set width}:
17698 (@value{GDBP}) whatis width
17700 (@value{GDBP}) p width
17702 (@value{GDBP}) set width=47
17703 Invalid syntax in expression.
17707 The invalid expression, of course, is @samp{=47}. In
17708 order to actually set the program's variable @code{width}, use
17711 (@value{GDBP}) set var width=47
17714 Because the @code{set} command has many subcommands that can conflict
17715 with the names of program variables, it is a good idea to use the
17716 @code{set variable} command instead of just @code{set}. For example, if
17717 your program has a variable @code{g}, you run into problems if you try
17718 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17719 the command @code{set gnutarget}, abbreviated @code{set g}:
17723 (@value{GDBP}) whatis g
17727 (@value{GDBP}) set g=4
17731 The program being debugged has been started already.
17732 Start it from the beginning? (y or n) y
17733 Starting program: /home/smith/cc_progs/a.out
17734 "/home/smith/cc_progs/a.out": can't open to read symbols:
17735 Invalid bfd target.
17736 (@value{GDBP}) show g
17737 The current BFD target is "=4".
17742 The program variable @code{g} did not change, and you silently set the
17743 @code{gnutarget} to an invalid value. In order to set the variable
17747 (@value{GDBP}) set var g=4
17750 @value{GDBN} allows more implicit conversions in assignments than C; you can
17751 freely store an integer value into a pointer variable or vice versa,
17752 and you can convert any structure to any other structure that is the
17753 same length or shorter.
17754 @comment FIXME: how do structs align/pad in these conversions?
17755 @comment /doc@cygnus.com 18dec1990
17757 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17758 construct to generate a value of specified type at a specified address
17759 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17760 to memory location @code{0x83040} as an integer (which implies a certain size
17761 and representation in memory), and
17764 set @{int@}0x83040 = 4
17768 stores the value 4 into that memory location.
17771 @section Continuing at a Different Address
17773 Ordinarily, when you continue your program, you do so at the place where
17774 it stopped, with the @code{continue} command. You can instead continue at
17775 an address of your own choosing, with the following commands:
17779 @kindex j @r{(@code{jump})}
17780 @item jump @var{location}
17781 @itemx j @var{location}
17782 Resume execution at @var{location}. Execution stops again immediately
17783 if there is a breakpoint there. @xref{Specify Location}, for a description
17784 of the different forms of @var{location}. It is common
17785 practice to use the @code{tbreak} command in conjunction with
17786 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17788 The @code{jump} command does not change the current stack frame, or
17789 the stack pointer, or the contents of any memory location or any
17790 register other than the program counter. If @var{location} is in
17791 a different function from the one currently executing, the results may
17792 be bizarre if the two functions expect different patterns of arguments or
17793 of local variables. For this reason, the @code{jump} command requests
17794 confirmation if the specified line is not in the function currently
17795 executing. However, even bizarre results are predictable if you are
17796 well acquainted with the machine-language code of your program.
17799 On many systems, you can get much the same effect as the @code{jump}
17800 command by storing a new value into the register @code{$pc}. The
17801 difference is that this does not start your program running; it only
17802 changes the address of where it @emph{will} run when you continue. For
17810 makes the next @code{continue} command or stepping command execute at
17811 address @code{0x485}, rather than at the address where your program stopped.
17812 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17814 The most common occasion to use the @code{jump} command is to back
17815 up---perhaps with more breakpoints set---over a portion of a program
17816 that has already executed, in order to examine its execution in more
17821 @section Giving your Program a Signal
17822 @cindex deliver a signal to a program
17826 @item signal @var{signal}
17827 Resume execution where your program is stopped, but immediately give it the
17828 signal @var{signal}. The @var{signal} can be the name or the number of a
17829 signal. For example, on many systems @code{signal 2} and @code{signal
17830 SIGINT} are both ways of sending an interrupt signal.
17832 Alternatively, if @var{signal} is zero, continue execution without
17833 giving a signal. This is useful when your program stopped on account of
17834 a signal and would ordinarily see the signal when resumed with the
17835 @code{continue} command; @samp{signal 0} causes it to resume without a
17838 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17839 delivered to the currently selected thread, not the thread that last
17840 reported a stop. This includes the situation where a thread was
17841 stopped due to a signal. So if you want to continue execution
17842 suppressing the signal that stopped a thread, you should select that
17843 same thread before issuing the @samp{signal 0} command. If you issue
17844 the @samp{signal 0} command with another thread as the selected one,
17845 @value{GDBN} detects that and asks for confirmation.
17847 Invoking the @code{signal} command is not the same as invoking the
17848 @code{kill} utility from the shell. Sending a signal with @code{kill}
17849 causes @value{GDBN} to decide what to do with the signal depending on
17850 the signal handling tables (@pxref{Signals}). The @code{signal} command
17851 passes the signal directly to your program.
17853 @code{signal} does not repeat when you press @key{RET} a second time
17854 after executing the command.
17856 @kindex queue-signal
17857 @item queue-signal @var{signal}
17858 Queue @var{signal} to be delivered immediately to the current thread
17859 when execution of the thread resumes. The @var{signal} can be the name or
17860 the number of a signal. For example, on many systems @code{signal 2} and
17861 @code{signal SIGINT} are both ways of sending an interrupt signal.
17862 The handling of the signal must be set to pass the signal to the program,
17863 otherwise @value{GDBN} will report an error.
17864 You can control the handling of signals from @value{GDBN} with the
17865 @code{handle} command (@pxref{Signals}).
17867 Alternatively, if @var{signal} is zero, any currently queued signal
17868 for the current thread is discarded and when execution resumes no signal
17869 will be delivered. This is useful when your program stopped on account
17870 of a signal and would ordinarily see the signal when resumed with the
17871 @code{continue} command.
17873 This command differs from the @code{signal} command in that the signal
17874 is just queued, execution is not resumed. And @code{queue-signal} cannot
17875 be used to pass a signal whose handling state has been set to @code{nopass}
17880 @xref{stepping into signal handlers}, for information on how stepping
17881 commands behave when the thread has a signal queued.
17884 @section Returning from a Function
17887 @cindex returning from a function
17890 @itemx return @var{expression}
17891 You can cancel execution of a function call with the @code{return}
17892 command. If you give an
17893 @var{expression} argument, its value is used as the function's return
17897 When you use @code{return}, @value{GDBN} discards the selected stack frame
17898 (and all frames within it). You can think of this as making the
17899 discarded frame return prematurely. If you wish to specify a value to
17900 be returned, give that value as the argument to @code{return}.
17902 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17903 Frame}), and any other frames inside of it, leaving its caller as the
17904 innermost remaining frame. That frame becomes selected. The
17905 specified value is stored in the registers used for returning values
17908 The @code{return} command does not resume execution; it leaves the
17909 program stopped in the state that would exist if the function had just
17910 returned. In contrast, the @code{finish} command (@pxref{Continuing
17911 and Stepping, ,Continuing and Stepping}) resumes execution until the
17912 selected stack frame returns naturally.
17914 @value{GDBN} needs to know how the @var{expression} argument should be set for
17915 the inferior. The concrete registers assignment depends on the OS ABI and the
17916 type being returned by the selected stack frame. For example it is common for
17917 OS ABI to return floating point values in FPU registers while integer values in
17918 CPU registers. Still some ABIs return even floating point values in CPU
17919 registers. Larger integer widths (such as @code{long long int}) also have
17920 specific placement rules. @value{GDBN} already knows the OS ABI from its
17921 current target so it needs to find out also the type being returned to make the
17922 assignment into the right register(s).
17924 Normally, the selected stack frame has debug info. @value{GDBN} will always
17925 use the debug info instead of the implicit type of @var{expression} when the
17926 debug info is available. For example, if you type @kbd{return -1}, and the
17927 function in the current stack frame is declared to return a @code{long long
17928 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17929 into a @code{long long int}:
17932 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17934 (@value{GDBP}) return -1
17935 Make func return now? (y or n) y
17936 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17937 43 printf ("result=%lld\n", func ());
17941 However, if the selected stack frame does not have a debug info, e.g., if the
17942 function was compiled without debug info, @value{GDBN} has to find out the type
17943 to return from user. Specifying a different type by mistake may set the value
17944 in different inferior registers than the caller code expects. For example,
17945 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17946 of a @code{long long int} result for a debug info less function (on 32-bit
17947 architectures). Therefore the user is required to specify the return type by
17948 an appropriate cast explicitly:
17951 Breakpoint 2, 0x0040050b in func ()
17952 (@value{GDBP}) return -1
17953 Return value type not available for selected stack frame.
17954 Please use an explicit cast of the value to return.
17955 (@value{GDBP}) return (long long int) -1
17956 Make selected stack frame return now? (y or n) y
17957 #0 0x00400526 in main ()
17962 @section Calling Program Functions
17965 @cindex calling functions
17966 @cindex inferior functions, calling
17967 @item print @var{expr}
17968 Evaluate the expression @var{expr} and display the resulting value.
17969 The expression may include calls to functions in the program being
17973 @item call @var{expr}
17974 Evaluate the expression @var{expr} without displaying @code{void}
17977 You can use this variant of the @code{print} command if you want to
17978 execute a function from your program that does not return anything
17979 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17980 with @code{void} returned values that @value{GDBN} will otherwise
17981 print. If the result is not void, it is printed and saved in the
17985 It is possible for the function you call via the @code{print} or
17986 @code{call} command to generate a signal (e.g., if there's a bug in
17987 the function, or if you passed it incorrect arguments). What happens
17988 in that case is controlled by the @code{set unwindonsignal} command.
17990 Similarly, with a C@t{++} program it is possible for the function you
17991 call via the @code{print} or @code{call} command to generate an
17992 exception that is not handled due to the constraints of the dummy
17993 frame. In this case, any exception that is raised in the frame, but has
17994 an out-of-frame exception handler will not be found. GDB builds a
17995 dummy-frame for the inferior function call, and the unwinder cannot
17996 seek for exception handlers outside of this dummy-frame. What happens
17997 in that case is controlled by the
17998 @code{set unwind-on-terminating-exception} command.
18001 @item set unwindonsignal
18002 @kindex set unwindonsignal
18003 @cindex unwind stack in called functions
18004 @cindex call dummy stack unwinding
18005 Set unwinding of the stack if a signal is received while in a function
18006 that @value{GDBN} called in the program being debugged. If set to on,
18007 @value{GDBN} unwinds the stack it created for the call and restores
18008 the context to what it was before the call. If set to off (the
18009 default), @value{GDBN} stops in the frame where the signal was
18012 @item show unwindonsignal
18013 @kindex show unwindonsignal
18014 Show the current setting of stack unwinding in the functions called by
18017 @item set unwind-on-terminating-exception
18018 @kindex set unwind-on-terminating-exception
18019 @cindex unwind stack in called functions with unhandled exceptions
18020 @cindex call dummy stack unwinding on unhandled exception.
18021 Set unwinding of the stack if a C@t{++} exception is raised, but left
18022 unhandled while in a function that @value{GDBN} called in the program being
18023 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18024 it created for the call and restores the context to what it was before
18025 the call. If set to off, @value{GDBN} the exception is delivered to
18026 the default C@t{++} exception handler and the inferior terminated.
18028 @item show unwind-on-terminating-exception
18029 @kindex show unwind-on-terminating-exception
18030 Show the current setting of stack unwinding in the functions called by
18035 @subsection Calling functions with no debug info
18037 @cindex no debug info functions
18038 Sometimes, a function you wish to call is missing debug information.
18039 In such case, @value{GDBN} does not know the type of the function,
18040 including the types of the function's parameters. To avoid calling
18041 the inferior function incorrectly, which could result in the called
18042 function functioning erroneously and even crash, @value{GDBN} refuses
18043 to call the function unless you tell it the type of the function.
18045 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18046 to do that. The simplest is to cast the call to the function's
18047 declared return type. For example:
18050 (@value{GDBP}) p getenv ("PATH")
18051 'getenv' has unknown return type; cast the call to its declared return type
18052 (@value{GDBP}) p (char *) getenv ("PATH")
18053 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18056 Casting the return type of a no-debug function is equivalent to
18057 casting the function to a pointer to a prototyped function that has a
18058 prototype that matches the types of the passed-in arguments, and
18059 calling that. I.e., the call above is equivalent to:
18062 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18066 and given this prototyped C or C++ function with float parameters:
18069 float multiply (float v1, float v2) @{ return v1 * v2; @}
18073 these calls are equivalent:
18076 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18077 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18080 If the function you wish to call is declared as unprototyped (i.e.@:
18081 old K&R style), you must use the cast-to-function-pointer syntax, so
18082 that @value{GDBN} knows that it needs to apply default argument
18083 promotions (promote float arguments to double). @xref{ABI, float
18084 promotion}. For example, given this unprototyped C function with
18085 float parameters, and no debug info:
18089 multiply_noproto (v1, v2)
18097 you call it like this:
18100 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18104 @section Patching Programs
18106 @cindex patching binaries
18107 @cindex writing into executables
18108 @cindex writing into corefiles
18110 By default, @value{GDBN} opens the file containing your program's
18111 executable code (or the corefile) read-only. This prevents accidental
18112 alterations to machine code; but it also prevents you from intentionally
18113 patching your program's binary.
18115 If you'd like to be able to patch the binary, you can specify that
18116 explicitly with the @code{set write} command. For example, you might
18117 want to turn on internal debugging flags, or even to make emergency
18123 @itemx set write off
18124 If you specify @samp{set write on}, @value{GDBN} opens executable and
18125 core files for both reading and writing; if you specify @kbd{set write
18126 off} (the default), @value{GDBN} opens them read-only.
18128 If you have already loaded a file, you must load it again (using the
18129 @code{exec-file} or @code{core-file} command) after changing @code{set
18130 write}, for your new setting to take effect.
18134 Display whether executable files and core files are opened for writing
18135 as well as reading.
18138 @node Compiling and Injecting Code
18139 @section Compiling and injecting code in @value{GDBN}
18140 @cindex injecting code
18141 @cindex writing into executables
18142 @cindex compiling code
18144 @value{GDBN} supports on-demand compilation and code injection into
18145 programs running under @value{GDBN}. GCC 5.0 or higher built with
18146 @file{libcc1.so} must be installed for this functionality to be enabled.
18147 This functionality is implemented with the following commands.
18150 @kindex compile code
18151 @item compile code @var{source-code}
18152 @itemx compile code -raw @var{--} @var{source-code}
18153 Compile @var{source-code} with the compiler language found as the current
18154 language in @value{GDBN} (@pxref{Languages}). If compilation and
18155 injection is not supported with the current language specified in
18156 @value{GDBN}, or the compiler does not support this feature, an error
18157 message will be printed. If @var{source-code} compiles and links
18158 successfully, @value{GDBN} will load the object-code emitted,
18159 and execute it within the context of the currently selected inferior.
18160 It is important to note that the compiled code is executed immediately.
18161 After execution, the compiled code is removed from @value{GDBN} and any
18162 new types or variables you have defined will be deleted.
18164 The command allows you to specify @var{source-code} in two ways.
18165 The simplest method is to provide a single line of code to the command.
18169 compile code printf ("hello world\n");
18172 If you specify options on the command line as well as source code, they
18173 may conflict. The @samp{--} delimiter can be used to separate options
18174 from actual source code. E.g.:
18177 compile code -r -- printf ("hello world\n");
18180 Alternatively you can enter source code as multiple lines of text. To
18181 enter this mode, invoke the @samp{compile code} command without any text
18182 following the command. This will start the multiple-line editor and
18183 allow you to type as many lines of source code as required. When you
18184 have completed typing, enter @samp{end} on its own line to exit the
18189 >printf ("hello\n");
18190 >printf ("world\n");
18194 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18195 provided @var{source-code} in a callable scope. In this case, you must
18196 specify the entry point of the code by defining a function named
18197 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18198 inferior. Using @samp{-raw} option may be needed for example when
18199 @var{source-code} requires @samp{#include} lines which may conflict with
18200 inferior symbols otherwise.
18202 @kindex compile file
18203 @item compile file @var{filename}
18204 @itemx compile file -raw @var{filename}
18205 Like @code{compile code}, but take the source code from @var{filename}.
18208 compile file /home/user/example.c
18213 @item compile print @var{expr}
18214 @itemx compile print /@var{f} @var{expr}
18215 Compile and execute @var{expr} with the compiler language found as the
18216 current language in @value{GDBN} (@pxref{Languages}). By default the
18217 value of @var{expr} is printed in a format appropriate to its data type;
18218 you can choose a different format by specifying @samp{/@var{f}}, where
18219 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18222 @item compile print
18223 @itemx compile print /@var{f}
18224 @cindex reprint the last value
18225 Alternatively you can enter the expression (source code producing it) as
18226 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18227 command without any text following the command. This will start the
18228 multiple-line editor.
18232 The process of compiling and injecting the code can be inspected using:
18235 @anchor{set debug compile}
18236 @item set debug compile
18237 @cindex compile command debugging info
18238 Turns on or off display of @value{GDBN} process of compiling and
18239 injecting the code. The default is off.
18241 @item show debug compile
18242 Displays the current state of displaying @value{GDBN} process of
18243 compiling and injecting the code.
18246 @subsection Compilation options for the @code{compile} command
18248 @value{GDBN} needs to specify the right compilation options for the code
18249 to be injected, in part to make its ABI compatible with the inferior
18250 and in part to make the injected code compatible with @value{GDBN}'s
18254 The options used, in increasing precedence:
18257 @item target architecture and OS options (@code{gdbarch})
18258 These options depend on target processor type and target operating
18259 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18260 (@code{-m64}) compilation option.
18262 @item compilation options recorded in the target
18263 @value{NGCC} (since version 4.7) stores the options used for compilation
18264 into @code{DW_AT_producer} part of DWARF debugging information according
18265 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18266 explicitly specify @code{-g} during inferior compilation otherwise
18267 @value{NGCC} produces no DWARF. This feature is only relevant for
18268 platforms where @code{-g} produces DWARF by default, otherwise one may
18269 try to enforce DWARF by using @code{-gdwarf-4}.
18271 @item compilation options set by @code{set compile-args}
18275 You can override compilation options using the following command:
18278 @item set compile-args
18279 @cindex compile command options override
18280 Set compilation options used for compiling and injecting code with the
18281 @code{compile} commands. These options override any conflicting ones
18282 from the target architecture and/or options stored during inferior
18285 @item show compile-args
18286 Displays the current state of compilation options override.
18287 This does not show all the options actually used during compilation,
18288 use @ref{set debug compile} for that.
18291 @subsection Caveats when using the @code{compile} command
18293 There are a few caveats to keep in mind when using the @code{compile}
18294 command. As the caveats are different per language, the table below
18295 highlights specific issues on a per language basis.
18298 @item C code examples and caveats
18299 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18300 attempt to compile the source code with a @samp{C} compiler. The source
18301 code provided to the @code{compile} command will have much the same
18302 access to variables and types as it normally would if it were part of
18303 the program currently being debugged in @value{GDBN}.
18305 Below is a sample program that forms the basis of the examples that
18306 follow. This program has been compiled and loaded into @value{GDBN},
18307 much like any other normal debugging session.
18310 void function1 (void)
18313 printf ("function 1\n");
18316 void function2 (void)
18331 For the purposes of the examples in this section, the program above has
18332 been compiled, loaded into @value{GDBN}, stopped at the function
18333 @code{main}, and @value{GDBN} is awaiting input from the user.
18335 To access variables and types for any program in @value{GDBN}, the
18336 program must be compiled and packaged with debug information. The
18337 @code{compile} command is not an exception to this rule. Without debug
18338 information, you can still use the @code{compile} command, but you will
18339 be very limited in what variables and types you can access.
18341 So with that in mind, the example above has been compiled with debug
18342 information enabled. The @code{compile} command will have access to
18343 all variables and types (except those that may have been optimized
18344 out). Currently, as @value{GDBN} has stopped the program in the
18345 @code{main} function, the @code{compile} command would have access to
18346 the variable @code{k}. You could invoke the @code{compile} command
18347 and type some source code to set the value of @code{k}. You can also
18348 read it, or do anything with that variable you would normally do in
18349 @code{C}. Be aware that changes to inferior variables in the
18350 @code{compile} command are persistent. In the following example:
18353 compile code k = 3;
18357 the variable @code{k} is now 3. It will retain that value until
18358 something else in the example program changes it, or another
18359 @code{compile} command changes it.
18361 Normal scope and access rules apply to source code compiled and
18362 injected by the @code{compile} command. In the example, the variables
18363 @code{j} and @code{k} are not accessible yet, because the program is
18364 currently stopped in the @code{main} function, where these variables
18365 are not in scope. Therefore, the following command
18368 compile code j = 3;
18372 will result in a compilation error message.
18374 Once the program is continued, execution will bring these variables in
18375 scope, and they will become accessible; then the code you specify via
18376 the @code{compile} command will be able to access them.
18378 You can create variables and types with the @code{compile} command as
18379 part of your source code. Variables and types that are created as part
18380 of the @code{compile} command are not visible to the rest of the program for
18381 the duration of its run. This example is valid:
18384 compile code int ff = 5; printf ("ff is %d\n", ff);
18387 However, if you were to type the following into @value{GDBN} after that
18388 command has completed:
18391 compile code printf ("ff is %d\n'', ff);
18395 a compiler error would be raised as the variable @code{ff} no longer
18396 exists. Object code generated and injected by the @code{compile}
18397 command is removed when its execution ends. Caution is advised
18398 when assigning to program variables values of variables created by the
18399 code submitted to the @code{compile} command. This example is valid:
18402 compile code int ff = 5; k = ff;
18405 The value of the variable @code{ff} is assigned to @code{k}. The variable
18406 @code{k} does not require the existence of @code{ff} to maintain the value
18407 it has been assigned. However, pointers require particular care in
18408 assignment. If the source code compiled with the @code{compile} command
18409 changed the address of a pointer in the example program, perhaps to a
18410 variable created in the @code{compile} command, that pointer would point
18411 to an invalid location when the command exits. The following example
18412 would likely cause issues with your debugged program:
18415 compile code int ff = 5; p = &ff;
18418 In this example, @code{p} would point to @code{ff} when the
18419 @code{compile} command is executing the source code provided to it.
18420 However, as variables in the (example) program persist with their
18421 assigned values, the variable @code{p} would point to an invalid
18422 location when the command exists. A general rule should be followed
18423 in that you should either assign @code{NULL} to any assigned pointers,
18424 or restore a valid location to the pointer before the command exits.
18426 Similar caution must be exercised with any structs, unions, and typedefs
18427 defined in @code{compile} command. Types defined in the @code{compile}
18428 command will no longer be available in the next @code{compile} command.
18429 Therefore, if you cast a variable to a type defined in the
18430 @code{compile} command, care must be taken to ensure that any future
18431 need to resolve the type can be achieved.
18434 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18435 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18436 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18437 Compilation failed.
18438 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18442 Variables that have been optimized away by the compiler are not
18443 accessible to the code submitted to the @code{compile} command.
18444 Access to those variables will generate a compiler error which @value{GDBN}
18445 will print to the console.
18448 @subsection Compiler search for the @code{compile} command
18450 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18451 which may not be obvious for remote targets of different architecture
18452 than where @value{GDBN} is running. Environment variable @code{PATH} on
18453 @value{GDBN} host is searched for @value{NGCC} binary matching the
18454 target architecture and operating system. This search can be overriden
18455 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18456 taken from shell that executed @value{GDBN}, it is not the value set by
18457 @value{GDBN} command @code{set environment}). @xref{Environment}.
18460 Specifically @code{PATH} is searched for binaries matching regular expression
18461 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18462 debugged. @var{arch} is processor name --- multiarch is supported, so for
18463 example both @code{i386} and @code{x86_64} targets look for pattern
18464 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18465 for pattern @code{s390x?}. @var{os} is currently supported only for
18466 pattern @code{linux(-gnu)?}.
18468 On Posix hosts the compiler driver @value{GDBN} needs to find also
18469 shared library @file{libcc1.so} from the compiler. It is searched in
18470 default shared library search path (overridable with usual environment
18471 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18472 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18473 according to the installation of the found compiler --- as possibly
18474 specified by the @code{set compile-gcc} command.
18477 @item set compile-gcc
18478 @cindex compile command driver filename override
18479 Set compilation command used for compiling and injecting code with the
18480 @code{compile} commands. If this option is not set (it is set to
18481 an empty string), the search described above will occur --- that is the
18484 @item show compile-gcc
18485 Displays the current compile command @value{NGCC} driver filename.
18486 If set, it is the main command @command{gcc}, found usually for example
18487 under name @file{x86_64-linux-gnu-gcc}.
18491 @chapter @value{GDBN} Files
18493 @value{GDBN} needs to know the file name of the program to be debugged,
18494 both in order to read its symbol table and in order to start your
18495 program. To debug a core dump of a previous run, you must also tell
18496 @value{GDBN} the name of the core dump file.
18499 * Files:: Commands to specify files
18500 * File Caching:: Information about @value{GDBN}'s file caching
18501 * Separate Debug Files:: Debugging information in separate files
18502 * MiniDebugInfo:: Debugging information in a special section
18503 * Index Files:: Index files speed up GDB
18504 * Symbol Errors:: Errors reading symbol files
18505 * Data Files:: GDB data files
18509 @section Commands to Specify Files
18511 @cindex symbol table
18512 @cindex core dump file
18514 You may want to specify executable and core dump file names. The usual
18515 way to do this is at start-up time, using the arguments to
18516 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18517 Out of @value{GDBN}}).
18519 Occasionally it is necessary to change to a different file during a
18520 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18521 specify a file you want to use. Or you are debugging a remote target
18522 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18523 Program}). In these situations the @value{GDBN} commands to specify
18524 new files are useful.
18527 @cindex executable file
18529 @item file @var{filename}
18530 Use @var{filename} as the program to be debugged. It is read for its
18531 symbols and for the contents of pure memory. It is also the program
18532 executed when you use the @code{run} command. If you do not specify a
18533 directory and the file is not found in the @value{GDBN} working directory,
18534 @value{GDBN} uses the environment variable @code{PATH} as a list of
18535 directories to search, just as the shell does when looking for a program
18536 to run. You can change the value of this variable, for both @value{GDBN}
18537 and your program, using the @code{path} command.
18539 @cindex unlinked object files
18540 @cindex patching object files
18541 You can load unlinked object @file{.o} files into @value{GDBN} using
18542 the @code{file} command. You will not be able to ``run'' an object
18543 file, but you can disassemble functions and inspect variables. Also,
18544 if the underlying BFD functionality supports it, you could use
18545 @kbd{gdb -write} to patch object files using this technique. Note
18546 that @value{GDBN} can neither interpret nor modify relocations in this
18547 case, so branches and some initialized variables will appear to go to
18548 the wrong place. But this feature is still handy from time to time.
18551 @code{file} with no argument makes @value{GDBN} discard any information it
18552 has on both executable file and the symbol table.
18555 @item exec-file @r{[} @var{filename} @r{]}
18556 Specify that the program to be run (but not the symbol table) is found
18557 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18558 if necessary to locate your program. Omitting @var{filename} means to
18559 discard information on the executable file.
18561 @kindex symbol-file
18562 @item symbol-file @r{[} @var{filename} @r{]}
18563 Read symbol table information from file @var{filename}. @code{PATH} is
18564 searched when necessary. Use the @code{file} command to get both symbol
18565 table and program to run from the same file.
18567 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18568 program's symbol table.
18570 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18571 some breakpoints and auto-display expressions. This is because they may
18572 contain pointers to the internal data recording symbols and data types,
18573 which are part of the old symbol table data being discarded inside
18576 @code{symbol-file} does not repeat if you press @key{RET} again after
18579 When @value{GDBN} is configured for a particular environment, it
18580 understands debugging information in whatever format is the standard
18581 generated for that environment; you may use either a @sc{gnu} compiler, or
18582 other compilers that adhere to the local conventions.
18583 Best results are usually obtained from @sc{gnu} compilers; for example,
18584 using @code{@value{NGCC}} you can generate debugging information for
18587 For most kinds of object files, with the exception of old SVR3 systems
18588 using COFF, the @code{symbol-file} command does not normally read the
18589 symbol table in full right away. Instead, it scans the symbol table
18590 quickly to find which source files and which symbols are present. The
18591 details are read later, one source file at a time, as they are needed.
18593 The purpose of this two-stage reading strategy is to make @value{GDBN}
18594 start up faster. For the most part, it is invisible except for
18595 occasional pauses while the symbol table details for a particular source
18596 file are being read. (The @code{set verbose} command can turn these
18597 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18598 Warnings and Messages}.)
18600 We have not implemented the two-stage strategy for COFF yet. When the
18601 symbol table is stored in COFF format, @code{symbol-file} reads the
18602 symbol table data in full right away. Note that ``stabs-in-COFF''
18603 still does the two-stage strategy, since the debug info is actually
18607 @cindex reading symbols immediately
18608 @cindex symbols, reading immediately
18609 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18610 @itemx file @r{[} -readnow @r{]} @var{filename}
18611 You can override the @value{GDBN} two-stage strategy for reading symbol
18612 tables by using the @samp{-readnow} option with any of the commands that
18613 load symbol table information, if you want to be sure @value{GDBN} has the
18614 entire symbol table available.
18616 @cindex @code{-readnever}, option for symbol-file command
18617 @cindex never read symbols
18618 @cindex symbols, never read
18619 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18620 @itemx file @r{[} -readnever @r{]} @var{filename}
18621 You can instruct @value{GDBN} to never read the symbolic information
18622 contained in @var{filename} by using the @samp{-readnever} option.
18623 @xref{--readnever}.
18625 @c FIXME: for now no mention of directories, since this seems to be in
18626 @c flux. 13mar1992 status is that in theory GDB would look either in
18627 @c current dir or in same dir as myprog; but issues like competing
18628 @c GDB's, or clutter in system dirs, mean that in practice right now
18629 @c only current dir is used. FFish says maybe a special GDB hierarchy
18630 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18634 @item core-file @r{[}@var{filename}@r{]}
18636 Specify the whereabouts of a core dump file to be used as the ``contents
18637 of memory''. Traditionally, core files contain only some parts of the
18638 address space of the process that generated them; @value{GDBN} can access the
18639 executable file itself for other parts.
18641 @code{core-file} with no argument specifies that no core file is
18644 Note that the core file is ignored when your program is actually running
18645 under @value{GDBN}. So, if you have been running your program and you
18646 wish to debug a core file instead, you must kill the subprocess in which
18647 the program is running. To do this, use the @code{kill} command
18648 (@pxref{Kill Process, ,Killing the Child Process}).
18650 @kindex add-symbol-file
18651 @cindex dynamic linking
18652 @item add-symbol-file @var{filename} @var{address}
18653 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18654 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18655 The @code{add-symbol-file} command reads additional symbol table
18656 information from the file @var{filename}. You would use this command
18657 when @var{filename} has been dynamically loaded (by some other means)
18658 into the program that is running. The @var{address} should give the memory
18659 address at which the file has been loaded; @value{GDBN} cannot figure
18660 this out for itself. You can additionally specify an arbitrary number
18661 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18662 section name and base address for that section. You can specify any
18663 @var{address} as an expression.
18665 The symbol table of the file @var{filename} is added to the symbol table
18666 originally read with the @code{symbol-file} command. You can use the
18667 @code{add-symbol-file} command any number of times; the new symbol data
18668 thus read is kept in addition to the old.
18670 Changes can be reverted using the command @code{remove-symbol-file}.
18672 @cindex relocatable object files, reading symbols from
18673 @cindex object files, relocatable, reading symbols from
18674 @cindex reading symbols from relocatable object files
18675 @cindex symbols, reading from relocatable object files
18676 @cindex @file{.o} files, reading symbols from
18677 Although @var{filename} is typically a shared library file, an
18678 executable file, or some other object file which has been fully
18679 relocated for loading into a process, you can also load symbolic
18680 information from relocatable @file{.o} files, as long as:
18684 the file's symbolic information refers only to linker symbols defined in
18685 that file, not to symbols defined by other object files,
18687 every section the file's symbolic information refers to has actually
18688 been loaded into the inferior, as it appears in the file, and
18690 you can determine the address at which every section was loaded, and
18691 provide these to the @code{add-symbol-file} command.
18695 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18696 relocatable files into an already running program; such systems
18697 typically make the requirements above easy to meet. However, it's
18698 important to recognize that many native systems use complex link
18699 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18700 assembly, for example) that make the requirements difficult to meet. In
18701 general, one cannot assume that using @code{add-symbol-file} to read a
18702 relocatable object file's symbolic information will have the same effect
18703 as linking the relocatable object file into the program in the normal
18706 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18708 @kindex remove-symbol-file
18709 @item remove-symbol-file @var{filename}
18710 @item remove-symbol-file -a @var{address}
18711 Remove a symbol file added via the @code{add-symbol-file} command. The
18712 file to remove can be identified by its @var{filename} or by an @var{address}
18713 that lies within the boundaries of this symbol file in memory. Example:
18716 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18717 add symbol table from file "/home/user/gdb/mylib.so" at
18718 .text_addr = 0x7ffff7ff9480
18720 Reading symbols from /home/user/gdb/mylib.so...done.
18721 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18722 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18727 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18729 @kindex add-symbol-file-from-memory
18730 @cindex @code{syscall DSO}
18731 @cindex load symbols from memory
18732 @item add-symbol-file-from-memory @var{address}
18733 Load symbols from the given @var{address} in a dynamically loaded
18734 object file whose image is mapped directly into the inferior's memory.
18735 For example, the Linux kernel maps a @code{syscall DSO} into each
18736 process's address space; this DSO provides kernel-specific code for
18737 some system calls. The argument can be any expression whose
18738 evaluation yields the address of the file's shared object file header.
18739 For this command to work, you must have used @code{symbol-file} or
18740 @code{exec-file} commands in advance.
18743 @item section @var{section} @var{addr}
18744 The @code{section} command changes the base address of the named
18745 @var{section} of the exec file to @var{addr}. This can be used if the
18746 exec file does not contain section addresses, (such as in the
18747 @code{a.out} format), or when the addresses specified in the file
18748 itself are wrong. Each section must be changed separately. The
18749 @code{info files} command, described below, lists all the sections and
18753 @kindex info target
18756 @code{info files} and @code{info target} are synonymous; both print the
18757 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18758 including the names of the executable and core dump files currently in
18759 use by @value{GDBN}, and the files from which symbols were loaded. The
18760 command @code{help target} lists all possible targets rather than
18763 @kindex maint info sections
18764 @item maint info sections
18765 Another command that can give you extra information about program sections
18766 is @code{maint info sections}. In addition to the section information
18767 displayed by @code{info files}, this command displays the flags and file
18768 offset of each section in the executable and core dump files. In addition,
18769 @code{maint info sections} provides the following command options (which
18770 may be arbitrarily combined):
18774 Display sections for all loaded object files, including shared libraries.
18775 @item @var{sections}
18776 Display info only for named @var{sections}.
18777 @item @var{section-flags}
18778 Display info only for sections for which @var{section-flags} are true.
18779 The section flags that @value{GDBN} currently knows about are:
18782 Section will have space allocated in the process when loaded.
18783 Set for all sections except those containing debug information.
18785 Section will be loaded from the file into the child process memory.
18786 Set for pre-initialized code and data, clear for @code{.bss} sections.
18788 Section needs to be relocated before loading.
18790 Section cannot be modified by the child process.
18792 Section contains executable code only.
18794 Section contains data only (no executable code).
18796 Section will reside in ROM.
18798 Section contains data for constructor/destructor lists.
18800 Section is not empty.
18802 An instruction to the linker to not output the section.
18803 @item COFF_SHARED_LIBRARY
18804 A notification to the linker that the section contains
18805 COFF shared library information.
18807 Section contains common symbols.
18810 @kindex set trust-readonly-sections
18811 @cindex read-only sections
18812 @item set trust-readonly-sections on
18813 Tell @value{GDBN} that readonly sections in your object file
18814 really are read-only (i.e.@: that their contents will not change).
18815 In that case, @value{GDBN} can fetch values from these sections
18816 out of the object file, rather than from the target program.
18817 For some targets (notably embedded ones), this can be a significant
18818 enhancement to debugging performance.
18820 The default is off.
18822 @item set trust-readonly-sections off
18823 Tell @value{GDBN} not to trust readonly sections. This means that
18824 the contents of the section might change while the program is running,
18825 and must therefore be fetched from the target when needed.
18827 @item show trust-readonly-sections
18828 Show the current setting of trusting readonly sections.
18831 All file-specifying commands allow both absolute and relative file names
18832 as arguments. @value{GDBN} always converts the file name to an absolute file
18833 name and remembers it that way.
18835 @cindex shared libraries
18836 @anchor{Shared Libraries}
18837 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18838 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18839 DSBT (TIC6X) shared libraries.
18841 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18842 shared libraries. @xref{Expat}.
18844 @value{GDBN} automatically loads symbol definitions from shared libraries
18845 when you use the @code{run} command, or when you examine a core file.
18846 (Before you issue the @code{run} command, @value{GDBN} does not understand
18847 references to a function in a shared library, however---unless you are
18848 debugging a core file).
18850 @c FIXME: some @value{GDBN} release may permit some refs to undef
18851 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18852 @c FIXME...lib; check this from time to time when updating manual
18854 There are times, however, when you may wish to not automatically load
18855 symbol definitions from shared libraries, such as when they are
18856 particularly large or there are many of them.
18858 To control the automatic loading of shared library symbols, use the
18862 @kindex set auto-solib-add
18863 @item set auto-solib-add @var{mode}
18864 If @var{mode} is @code{on}, symbols from all shared object libraries
18865 will be loaded automatically when the inferior begins execution, you
18866 attach to an independently started inferior, or when the dynamic linker
18867 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18868 is @code{off}, symbols must be loaded manually, using the
18869 @code{sharedlibrary} command. The default value is @code{on}.
18871 @cindex memory used for symbol tables
18872 If your program uses lots of shared libraries with debug info that
18873 takes large amounts of memory, you can decrease the @value{GDBN}
18874 memory footprint by preventing it from automatically loading the
18875 symbols from shared libraries. To that end, type @kbd{set
18876 auto-solib-add off} before running the inferior, then load each
18877 library whose debug symbols you do need with @kbd{sharedlibrary
18878 @var{regexp}}, where @var{regexp} is a regular expression that matches
18879 the libraries whose symbols you want to be loaded.
18881 @kindex show auto-solib-add
18882 @item show auto-solib-add
18883 Display the current autoloading mode.
18886 @cindex load shared library
18887 To explicitly load shared library symbols, use the @code{sharedlibrary}
18891 @kindex info sharedlibrary
18893 @item info share @var{regex}
18894 @itemx info sharedlibrary @var{regex}
18895 Print the names of the shared libraries which are currently loaded
18896 that match @var{regex}. If @var{regex} is omitted then print
18897 all shared libraries that are loaded.
18900 @item info dll @var{regex}
18901 This is an alias of @code{info sharedlibrary}.
18903 @kindex sharedlibrary
18905 @item sharedlibrary @var{regex}
18906 @itemx share @var{regex}
18907 Load shared object library symbols for files matching a
18908 Unix regular expression.
18909 As with files loaded automatically, it only loads shared libraries
18910 required by your program for a core file or after typing @code{run}. If
18911 @var{regex} is omitted all shared libraries required by your program are
18914 @item nosharedlibrary
18915 @kindex nosharedlibrary
18916 @cindex unload symbols from shared libraries
18917 Unload all shared object library symbols. This discards all symbols
18918 that have been loaded from all shared libraries. Symbols from shared
18919 libraries that were loaded by explicit user requests are not
18923 Sometimes you may wish that @value{GDBN} stops and gives you control
18924 when any of shared library events happen. The best way to do this is
18925 to use @code{catch load} and @code{catch unload} (@pxref{Set
18928 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18929 command for this. This command exists for historical reasons. It is
18930 less useful than setting a catchpoint, because it does not allow for
18931 conditions or commands as a catchpoint does.
18934 @item set stop-on-solib-events
18935 @kindex set stop-on-solib-events
18936 This command controls whether @value{GDBN} should give you control
18937 when the dynamic linker notifies it about some shared library event.
18938 The most common event of interest is loading or unloading of a new
18941 @item show stop-on-solib-events
18942 @kindex show stop-on-solib-events
18943 Show whether @value{GDBN} stops and gives you control when shared
18944 library events happen.
18947 Shared libraries are also supported in many cross or remote debugging
18948 configurations. @value{GDBN} needs to have access to the target's libraries;
18949 this can be accomplished either by providing copies of the libraries
18950 on the host system, or by asking @value{GDBN} to automatically retrieve the
18951 libraries from the target. If copies of the target libraries are
18952 provided, they need to be the same as the target libraries, although the
18953 copies on the target can be stripped as long as the copies on the host are
18956 @cindex where to look for shared libraries
18957 For remote debugging, you need to tell @value{GDBN} where the target
18958 libraries are, so that it can load the correct copies---otherwise, it
18959 may try to load the host's libraries. @value{GDBN} has two variables
18960 to specify the search directories for target libraries.
18963 @cindex prefix for executable and shared library file names
18964 @cindex system root, alternate
18965 @kindex set solib-absolute-prefix
18966 @kindex set sysroot
18967 @item set sysroot @var{path}
18968 Use @var{path} as the system root for the program being debugged. Any
18969 absolute shared library paths will be prefixed with @var{path}; many
18970 runtime loaders store the absolute paths to the shared library in the
18971 target program's memory. When starting processes remotely, and when
18972 attaching to already-running processes (local or remote), their
18973 executable filenames will be prefixed with @var{path} if reported to
18974 @value{GDBN} as absolute by the operating system. If you use
18975 @code{set sysroot} to find executables and shared libraries, they need
18976 to be laid out in the same way that they are on the target, with
18977 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18980 If @var{path} starts with the sequence @file{target:} and the target
18981 system is remote then @value{GDBN} will retrieve the target binaries
18982 from the remote system. This is only supported when using a remote
18983 target that supports the @code{remote get} command (@pxref{File
18984 Transfer,,Sending files to a remote system}). The part of @var{path}
18985 following the initial @file{target:} (if present) is used as system
18986 root prefix on the remote file system. If @var{path} starts with the
18987 sequence @file{remote:} this is converted to the sequence
18988 @file{target:} by @code{set sysroot}@footnote{Historically the
18989 functionality to retrieve binaries from the remote system was
18990 provided by prefixing @var{path} with @file{remote:}}. If you want
18991 to specify a local system root using a directory that happens to be
18992 named @file{target:} or @file{remote:}, you need to use some
18993 equivalent variant of the name like @file{./target:}.
18995 For targets with an MS-DOS based filesystem, such as MS-Windows and
18996 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18997 absolute file name with @var{path}. But first, on Unix hosts,
18998 @value{GDBN} converts all backslash directory separators into forward
18999 slashes, because the backslash is not a directory separator on Unix:
19002 c:\foo\bar.dll @result{} c:/foo/bar.dll
19005 Then, @value{GDBN} attempts prefixing the target file name with
19006 @var{path}, and looks for the resulting file name in the host file
19010 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19013 If that does not find the binary, @value{GDBN} tries removing
19014 the @samp{:} character from the drive spec, both for convenience, and,
19015 for the case of the host file system not supporting file names with
19019 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19022 This makes it possible to have a system root that mirrors a target
19023 with more than one drive. E.g., you may want to setup your local
19024 copies of the target system shared libraries like so (note @samp{c} vs
19028 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19029 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19030 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19034 and point the system root at @file{/path/to/sysroot}, so that
19035 @value{GDBN} can find the correct copies of both
19036 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19038 If that still does not find the binary, @value{GDBN} tries
19039 removing the whole drive spec from the target file name:
19042 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19045 This last lookup makes it possible to not care about the drive name,
19046 if you don't want or need to.
19048 The @code{set solib-absolute-prefix} command is an alias for @code{set
19051 @cindex default system root
19052 @cindex @samp{--with-sysroot}
19053 You can set the default system root by using the configure-time
19054 @samp{--with-sysroot} option. If the system root is inside
19055 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19056 @samp{--exec-prefix}), then the default system root will be updated
19057 automatically if the installed @value{GDBN} is moved to a new
19060 @kindex show sysroot
19062 Display the current executable and shared library prefix.
19064 @kindex set solib-search-path
19065 @item set solib-search-path @var{path}
19066 If this variable is set, @var{path} is a colon-separated list of
19067 directories to search for shared libraries. @samp{solib-search-path}
19068 is used after @samp{sysroot} fails to locate the library, or if the
19069 path to the library is relative instead of absolute. If you want to
19070 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19071 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19072 finding your host's libraries. @samp{sysroot} is preferred; setting
19073 it to a nonexistent directory may interfere with automatic loading
19074 of shared library symbols.
19076 @kindex show solib-search-path
19077 @item show solib-search-path
19078 Display the current shared library search path.
19080 @cindex DOS file-name semantics of file names.
19081 @kindex set target-file-system-kind (unix|dos-based|auto)
19082 @kindex show target-file-system-kind
19083 @item set target-file-system-kind @var{kind}
19084 Set assumed file system kind for target reported file names.
19086 Shared library file names as reported by the target system may not
19087 make sense as is on the system @value{GDBN} is running on. For
19088 example, when remote debugging a target that has MS-DOS based file
19089 system semantics, from a Unix host, the target may be reporting to
19090 @value{GDBN} a list of loaded shared libraries with file names such as
19091 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19092 drive letters, so the @samp{c:\} prefix is not normally understood as
19093 indicating an absolute file name, and neither is the backslash
19094 normally considered a directory separator character. In that case,
19095 the native file system would interpret this whole absolute file name
19096 as a relative file name with no directory components. This would make
19097 it impossible to point @value{GDBN} at a copy of the remote target's
19098 shared libraries on the host using @code{set sysroot}, and impractical
19099 with @code{set solib-search-path}. Setting
19100 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19101 to interpret such file names similarly to how the target would, and to
19102 map them to file names valid on @value{GDBN}'s native file system
19103 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19104 to one of the supported file system kinds. In that case, @value{GDBN}
19105 tries to determine the appropriate file system variant based on the
19106 current target's operating system (@pxref{ABI, ,Configuring the
19107 Current ABI}). The supported file system settings are:
19111 Instruct @value{GDBN} to assume the target file system is of Unix
19112 kind. Only file names starting the forward slash (@samp{/}) character
19113 are considered absolute, and the directory separator character is also
19117 Instruct @value{GDBN} to assume the target file system is DOS based.
19118 File names starting with either a forward slash, or a drive letter
19119 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19120 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19121 considered directory separators.
19124 Instruct @value{GDBN} to use the file system kind associated with the
19125 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19126 This is the default.
19130 @cindex file name canonicalization
19131 @cindex base name differences
19132 When processing file names provided by the user, @value{GDBN}
19133 frequently needs to compare them to the file names recorded in the
19134 program's debug info. Normally, @value{GDBN} compares just the
19135 @dfn{base names} of the files as strings, which is reasonably fast
19136 even for very large programs. (The base name of a file is the last
19137 portion of its name, after stripping all the leading directories.)
19138 This shortcut in comparison is based upon the assumption that files
19139 cannot have more than one base name. This is usually true, but
19140 references to files that use symlinks or similar filesystem
19141 facilities violate that assumption. If your program records files
19142 using such facilities, or if you provide file names to @value{GDBN}
19143 using symlinks etc., you can set @code{basenames-may-differ} to
19144 @code{true} to instruct @value{GDBN} to completely canonicalize each
19145 pair of file names it needs to compare. This will make file-name
19146 comparisons accurate, but at a price of a significant slowdown.
19149 @item set basenames-may-differ
19150 @kindex set basenames-may-differ
19151 Set whether a source file may have multiple base names.
19153 @item show basenames-may-differ
19154 @kindex show basenames-may-differ
19155 Show whether a source file may have multiple base names.
19159 @section File Caching
19160 @cindex caching of opened files
19161 @cindex caching of bfd objects
19163 To speed up file loading, and reduce memory usage, @value{GDBN} will
19164 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19165 BFD, bfd, The Binary File Descriptor Library}. The following commands
19166 allow visibility and control of the caching behavior.
19169 @kindex maint info bfds
19170 @item maint info bfds
19171 This prints information about each @code{bfd} object that is known to
19174 @kindex maint set bfd-sharing
19175 @kindex maint show bfd-sharing
19176 @kindex bfd caching
19177 @item maint set bfd-sharing
19178 @item maint show bfd-sharing
19179 Control whether @code{bfd} objects can be shared. When sharing is
19180 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19181 than reopening the same file. Turning sharing off does not cause
19182 already shared @code{bfd} objects to be unshared, but all future files
19183 that are opened will create a new @code{bfd} object. Similarly,
19184 re-enabling sharing does not cause multiple existing @code{bfd}
19185 objects to be collapsed into a single shared @code{bfd} object.
19187 @kindex set debug bfd-cache @var{level}
19188 @kindex bfd caching
19189 @item set debug bfd-cache @var{level}
19190 Turns on debugging of the bfd cache, setting the level to @var{level}.
19192 @kindex show debug bfd-cache
19193 @kindex bfd caching
19194 @item show debug bfd-cache
19195 Show the current debugging level of the bfd cache.
19198 @node Separate Debug Files
19199 @section Debugging Information in Separate Files
19200 @cindex separate debugging information files
19201 @cindex debugging information in separate files
19202 @cindex @file{.debug} subdirectories
19203 @cindex debugging information directory, global
19204 @cindex global debugging information directories
19205 @cindex build ID, and separate debugging files
19206 @cindex @file{.build-id} directory
19208 @value{GDBN} allows you to put a program's debugging information in a
19209 file separate from the executable itself, in a way that allows
19210 @value{GDBN} to find and load the debugging information automatically.
19211 Since debugging information can be very large---sometimes larger
19212 than the executable code itself---some systems distribute debugging
19213 information for their executables in separate files, which users can
19214 install only when they need to debug a problem.
19216 @value{GDBN} supports two ways of specifying the separate debug info
19221 The executable contains a @dfn{debug link} that specifies the name of
19222 the separate debug info file. The separate debug file's name is
19223 usually @file{@var{executable}.debug}, where @var{executable} is the
19224 name of the corresponding executable file without leading directories
19225 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19226 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19227 checksum for the debug file, which @value{GDBN} uses to validate that
19228 the executable and the debug file came from the same build.
19231 The executable contains a @dfn{build ID}, a unique bit string that is
19232 also present in the corresponding debug info file. (This is supported
19233 only on some operating systems, when using the ELF or PE file formats
19234 for binary files and the @sc{gnu} Binutils.) For more details about
19235 this feature, see the description of the @option{--build-id}
19236 command-line option in @ref{Options, , Command Line Options, ld.info,
19237 The GNU Linker}. The debug info file's name is not specified
19238 explicitly by the build ID, but can be computed from the build ID, see
19242 Depending on the way the debug info file is specified, @value{GDBN}
19243 uses two different methods of looking for the debug file:
19247 For the ``debug link'' method, @value{GDBN} looks up the named file in
19248 the directory of the executable file, then in a subdirectory of that
19249 directory named @file{.debug}, and finally under each one of the global debug
19250 directories, in a subdirectory whose name is identical to the leading
19251 directories of the executable's absolute file name.
19254 For the ``build ID'' method, @value{GDBN} looks in the
19255 @file{.build-id} subdirectory of each one of the global debug directories for
19256 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19257 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19258 are the rest of the bit string. (Real build ID strings are 32 or more
19259 hex characters, not 10.)
19262 So, for example, suppose you ask @value{GDBN} to debug
19263 @file{/usr/bin/ls}, which has a debug link that specifies the
19264 file @file{ls.debug}, and a build ID whose value in hex is
19265 @code{abcdef1234}. If the list of the global debug directories includes
19266 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19267 debug information files, in the indicated order:
19271 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19273 @file{/usr/bin/ls.debug}
19275 @file{/usr/bin/.debug/ls.debug}
19277 @file{/usr/lib/debug/usr/bin/ls.debug}.
19280 @anchor{debug-file-directory}
19281 Global debugging info directories default to what is set by @value{GDBN}
19282 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19283 you can also set the global debugging info directories, and view the list
19284 @value{GDBN} is currently using.
19288 @kindex set debug-file-directory
19289 @item set debug-file-directory @var{directories}
19290 Set the directories which @value{GDBN} searches for separate debugging
19291 information files to @var{directory}. Multiple path components can be set
19292 concatenating them by a path separator.
19294 @kindex show debug-file-directory
19295 @item show debug-file-directory
19296 Show the directories @value{GDBN} searches for separate debugging
19301 @cindex @code{.gnu_debuglink} sections
19302 @cindex debug link sections
19303 A debug link is a special section of the executable file named
19304 @code{.gnu_debuglink}. The section must contain:
19308 A filename, with any leading directory components removed, followed by
19311 zero to three bytes of padding, as needed to reach the next four-byte
19312 boundary within the section, and
19314 a four-byte CRC checksum, stored in the same endianness used for the
19315 executable file itself. The checksum is computed on the debugging
19316 information file's full contents by the function given below, passing
19317 zero as the @var{crc} argument.
19320 Any executable file format can carry a debug link, as long as it can
19321 contain a section named @code{.gnu_debuglink} with the contents
19324 @cindex @code{.note.gnu.build-id} sections
19325 @cindex build ID sections
19326 The build ID is a special section in the executable file (and in other
19327 ELF binary files that @value{GDBN} may consider). This section is
19328 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19329 It contains unique identification for the built files---the ID remains
19330 the same across multiple builds of the same build tree. The default
19331 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19332 content for the build ID string. The same section with an identical
19333 value is present in the original built binary with symbols, in its
19334 stripped variant, and in the separate debugging information file.
19336 The debugging information file itself should be an ordinary
19337 executable, containing a full set of linker symbols, sections, and
19338 debugging information. The sections of the debugging information file
19339 should have the same names, addresses, and sizes as the original file,
19340 but they need not contain any data---much like a @code{.bss} section
19341 in an ordinary executable.
19343 The @sc{gnu} binary utilities (Binutils) package includes the
19344 @samp{objcopy} utility that can produce
19345 the separated executable / debugging information file pairs using the
19346 following commands:
19349 @kbd{objcopy --only-keep-debug foo foo.debug}
19354 These commands remove the debugging
19355 information from the executable file @file{foo} and place it in the file
19356 @file{foo.debug}. You can use the first, second or both methods to link the
19361 The debug link method needs the following additional command to also leave
19362 behind a debug link in @file{foo}:
19365 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19368 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19369 a version of the @code{strip} command such that the command @kbd{strip foo -f
19370 foo.debug} has the same functionality as the two @code{objcopy} commands and
19371 the @code{ln -s} command above, together.
19374 Build ID gets embedded into the main executable using @code{ld --build-id} or
19375 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19376 compatibility fixes for debug files separation are present in @sc{gnu} binary
19377 utilities (Binutils) package since version 2.18.
19382 @cindex CRC algorithm definition
19383 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19384 IEEE 802.3 using the polynomial:
19386 @c TexInfo requires naked braces for multi-digit exponents for Tex
19387 @c output, but this causes HTML output to barf. HTML has to be set using
19388 @c raw commands. So we end up having to specify this equation in 2
19393 <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>
19394 + <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
19400 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19401 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19405 The function is computed byte at a time, taking the least
19406 significant bit of each byte first. The initial pattern
19407 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19408 the final result is inverted to ensure trailing zeros also affect the
19411 @emph{Note:} This is the same CRC polynomial as used in handling the
19412 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19413 However in the case of the Remote Serial Protocol, the CRC is computed
19414 @emph{most} significant bit first, and the result is not inverted, so
19415 trailing zeros have no effect on the CRC value.
19417 To complete the description, we show below the code of the function
19418 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19419 initially supplied @code{crc} argument means that an initial call to
19420 this function passing in zero will start computing the CRC using
19423 @kindex gnu_debuglink_crc32
19426 gnu_debuglink_crc32 (unsigned long crc,
19427 unsigned char *buf, size_t len)
19429 static const unsigned long crc32_table[256] =
19431 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19432 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19433 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19434 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19435 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19436 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19437 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19438 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19439 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19440 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19441 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19442 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19443 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19444 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19445 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19446 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19447 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19448 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19449 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19450 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19451 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19452 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19453 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19454 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19455 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19456 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19457 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19458 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19459 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19460 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19461 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19462 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19463 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19464 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19465 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19466 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19467 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19468 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19469 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19470 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19471 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19472 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19473 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19474 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19475 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19476 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19477 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19478 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19479 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19480 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19481 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19484 unsigned char *end;
19486 crc = ~crc & 0xffffffff;
19487 for (end = buf + len; buf < end; ++buf)
19488 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19489 return ~crc & 0xffffffff;
19494 This computation does not apply to the ``build ID'' method.
19496 @node MiniDebugInfo
19497 @section Debugging information in a special section
19498 @cindex separate debug sections
19499 @cindex @samp{.gnu_debugdata} section
19501 Some systems ship pre-built executables and libraries that have a
19502 special @samp{.gnu_debugdata} section. This feature is called
19503 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19504 is used to supply extra symbols for backtraces.
19506 The intent of this section is to provide extra minimal debugging
19507 information for use in simple backtraces. It is not intended to be a
19508 replacement for full separate debugging information (@pxref{Separate
19509 Debug Files}). The example below shows the intended use; however,
19510 @value{GDBN} does not currently put restrictions on what sort of
19511 debugging information might be included in the section.
19513 @value{GDBN} has support for this extension. If the section exists,
19514 then it is used provided that no other source of debugging information
19515 can be found, and that @value{GDBN} was configured with LZMA support.
19517 This section can be easily created using @command{objcopy} and other
19518 standard utilities:
19521 # Extract the dynamic symbols from the main binary, there is no need
19522 # to also have these in the normal symbol table.
19523 nm -D @var{binary} --format=posix --defined-only \
19524 | awk '@{ print $1 @}' | sort > dynsyms
19526 # Extract all the text (i.e. function) symbols from the debuginfo.
19527 # (Note that we actually also accept "D" symbols, for the benefit
19528 # of platforms like PowerPC64 that use function descriptors.)
19529 nm @var{binary} --format=posix --defined-only \
19530 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19533 # Keep all the function symbols not already in the dynamic symbol
19535 comm -13 dynsyms funcsyms > keep_symbols
19537 # Separate full debug info into debug binary.
19538 objcopy --only-keep-debug @var{binary} debug
19540 # Copy the full debuginfo, keeping only a minimal set of symbols and
19541 # removing some unnecessary sections.
19542 objcopy -S --remove-section .gdb_index --remove-section .comment \
19543 --keep-symbols=keep_symbols debug mini_debuginfo
19545 # Drop the full debug info from the original binary.
19546 strip --strip-all -R .comment @var{binary}
19548 # Inject the compressed data into the .gnu_debugdata section of the
19551 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19555 @section Index Files Speed Up @value{GDBN}
19556 @cindex index files
19557 @cindex @samp{.gdb_index} section
19559 When @value{GDBN} finds a symbol file, it scans the symbols in the
19560 file in order to construct an internal symbol table. This lets most
19561 @value{GDBN} operations work quickly---at the cost of a delay early
19562 on. For large programs, this delay can be quite lengthy, so
19563 @value{GDBN} provides a way to build an index, which speeds up
19566 The index is stored as a section in the symbol file. @value{GDBN} can
19567 write the index to a file, then you can put it into the symbol file
19568 using @command{objcopy}.
19570 To create an index file, use the @code{save gdb-index} command:
19573 @item save gdb-index [-dwarf-5] @var{directory}
19574 @kindex save gdb-index
19575 Create index files for all symbol files currently known by
19576 @value{GDBN}. For each known @var{symbol-file}, this command by
19577 default creates it produces a single file
19578 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19579 the @option{-dwarf-5} option, it produces 2 files:
19580 @file{@var{symbol-file}.debug_names} and
19581 @file{@var{symbol-file}.debug_str}. The files are created in the
19582 given @var{directory}.
19585 Once you have created an index file you can merge it into your symbol
19586 file, here named @file{symfile}, using @command{objcopy}:
19589 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19590 --set-section-flags .gdb_index=readonly symfile symfile
19593 Or for @code{-dwarf-5}:
19596 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19597 $ cat symfile.debug_str >>symfile.debug_str.new
19598 $ objcopy --add-section .debug_names=symfile.gdb-index \
19599 --set-section-flags .debug_names=readonly \
19600 --update-section .debug_str=symfile.debug_str.new symfile symfile
19603 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19604 sections that have been deprecated. Usually they are deprecated because
19605 they are missing a new feature or have performance issues.
19606 To tell @value{GDBN} to use a deprecated index section anyway
19607 specify @code{set use-deprecated-index-sections on}.
19608 The default is @code{off}.
19609 This can speed up startup, but may result in some functionality being lost.
19610 @xref{Index Section Format}.
19612 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19613 must be done before gdb reads the file. The following will not work:
19616 $ gdb -ex "set use-deprecated-index-sections on" <program>
19619 Instead you must do, for example,
19622 $ gdb -iex "set use-deprecated-index-sections on" <program>
19625 There are currently some limitation on indices. They only work when
19626 for DWARF debugging information, not stabs. And, they do not
19627 currently work for programs using Ada.
19629 @node Symbol Errors
19630 @section Errors Reading Symbol Files
19632 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19633 such as symbol types it does not recognize, or known bugs in compiler
19634 output. By default, @value{GDBN} does not notify you of such problems, since
19635 they are relatively common and primarily of interest to people
19636 debugging compilers. If you are interested in seeing information
19637 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19638 only one message about each such type of problem, no matter how many
19639 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19640 to see how many times the problems occur, with the @code{set
19641 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19644 The messages currently printed, and their meanings, include:
19647 @item inner block not inside outer block in @var{symbol}
19649 The symbol information shows where symbol scopes begin and end
19650 (such as at the start of a function or a block of statements). This
19651 error indicates that an inner scope block is not fully contained
19652 in its outer scope blocks.
19654 @value{GDBN} circumvents the problem by treating the inner block as if it had
19655 the same scope as the outer block. In the error message, @var{symbol}
19656 may be shown as ``@code{(don't know)}'' if the outer block is not a
19659 @item block at @var{address} out of order
19661 The symbol information for symbol scope blocks should occur in
19662 order of increasing addresses. This error indicates that it does not
19665 @value{GDBN} does not circumvent this problem, and has trouble
19666 locating symbols in the source file whose symbols it is reading. (You
19667 can often determine what source file is affected by specifying
19668 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19671 @item bad block start address patched
19673 The symbol information for a symbol scope block has a start address
19674 smaller than the address of the preceding source line. This is known
19675 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19677 @value{GDBN} circumvents the problem by treating the symbol scope block as
19678 starting on the previous source line.
19680 @item bad string table offset in symbol @var{n}
19683 Symbol number @var{n} contains a pointer into the string table which is
19684 larger than the size of the string table.
19686 @value{GDBN} circumvents the problem by considering the symbol to have the
19687 name @code{foo}, which may cause other problems if many symbols end up
19690 @item unknown symbol type @code{0x@var{nn}}
19692 The symbol information contains new data types that @value{GDBN} does
19693 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19694 uncomprehended information, in hexadecimal.
19696 @value{GDBN} circumvents the error by ignoring this symbol information.
19697 This usually allows you to debug your program, though certain symbols
19698 are not accessible. If you encounter such a problem and feel like
19699 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19700 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19701 and examine @code{*bufp} to see the symbol.
19703 @item stub type has NULL name
19705 @value{GDBN} could not find the full definition for a struct or class.
19707 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19708 The symbol information for a C@t{++} member function is missing some
19709 information that recent versions of the compiler should have output for
19712 @item info mismatch between compiler and debugger
19714 @value{GDBN} could not parse a type specification output by the compiler.
19719 @section GDB Data Files
19721 @cindex prefix for data files
19722 @value{GDBN} will sometimes read an auxiliary data file. These files
19723 are kept in a directory known as the @dfn{data directory}.
19725 You can set the data directory's name, and view the name @value{GDBN}
19726 is currently using.
19729 @kindex set data-directory
19730 @item set data-directory @var{directory}
19731 Set the directory which @value{GDBN} searches for auxiliary data files
19732 to @var{directory}.
19734 @kindex show data-directory
19735 @item show data-directory
19736 Show the directory @value{GDBN} searches for auxiliary data files.
19739 @cindex default data directory
19740 @cindex @samp{--with-gdb-datadir}
19741 You can set the default data directory by using the configure-time
19742 @samp{--with-gdb-datadir} option. If the data directory is inside
19743 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19744 @samp{--exec-prefix}), then the default data directory will be updated
19745 automatically if the installed @value{GDBN} is moved to a new
19748 The data directory may also be specified with the
19749 @code{--data-directory} command line option.
19750 @xref{Mode Options}.
19753 @chapter Specifying a Debugging Target
19755 @cindex debugging target
19756 A @dfn{target} is the execution environment occupied by your program.
19758 Often, @value{GDBN} runs in the same host environment as your program;
19759 in that case, the debugging target is specified as a side effect when
19760 you use the @code{file} or @code{core} commands. When you need more
19761 flexibility---for example, running @value{GDBN} on a physically separate
19762 host, or controlling a standalone system over a serial port or a
19763 realtime system over a TCP/IP connection---you can use the @code{target}
19764 command to specify one of the target types configured for @value{GDBN}
19765 (@pxref{Target Commands, ,Commands for Managing Targets}).
19767 @cindex target architecture
19768 It is possible to build @value{GDBN} for several different @dfn{target
19769 architectures}. When @value{GDBN} is built like that, you can choose
19770 one of the available architectures with the @kbd{set architecture}
19774 @kindex set architecture
19775 @kindex show architecture
19776 @item set architecture @var{arch}
19777 This command sets the current target architecture to @var{arch}. The
19778 value of @var{arch} can be @code{"auto"}, in addition to one of the
19779 supported architectures.
19781 @item show architecture
19782 Show the current target architecture.
19784 @item set processor
19786 @kindex set processor
19787 @kindex show processor
19788 These are alias commands for, respectively, @code{set architecture}
19789 and @code{show architecture}.
19793 * Active Targets:: Active targets
19794 * Target Commands:: Commands for managing targets
19795 * Byte Order:: Choosing target byte order
19798 @node Active Targets
19799 @section Active Targets
19801 @cindex stacking targets
19802 @cindex active targets
19803 @cindex multiple targets
19805 There are multiple classes of targets such as: processes, executable files or
19806 recording sessions. Core files belong to the process class, making core file
19807 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19808 on multiple active targets, one in each class. This allows you to (for
19809 example) start a process and inspect its activity, while still having access to
19810 the executable file after the process finishes. Or if you start process
19811 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19812 presented a virtual layer of the recording target, while the process target
19813 remains stopped at the chronologically last point of the process execution.
19815 Use the @code{core-file} and @code{exec-file} commands to select a new core
19816 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19817 specify as a target a process that is already running, use the @code{attach}
19818 command (@pxref{Attach, ,Debugging an Already-running Process}).
19820 @node Target Commands
19821 @section Commands for Managing Targets
19824 @item target @var{type} @var{parameters}
19825 Connects the @value{GDBN} host environment to a target machine or
19826 process. A target is typically a protocol for talking to debugging
19827 facilities. You use the argument @var{type} to specify the type or
19828 protocol of the target machine.
19830 Further @var{parameters} are interpreted by the target protocol, but
19831 typically include things like device names or host names to connect
19832 with, process numbers, and baud rates.
19834 The @code{target} command does not repeat if you press @key{RET} again
19835 after executing the command.
19837 @kindex help target
19839 Displays the names of all targets available. To display targets
19840 currently selected, use either @code{info target} or @code{info files}
19841 (@pxref{Files, ,Commands to Specify Files}).
19843 @item help target @var{name}
19844 Describe a particular target, including any parameters necessary to
19847 @kindex set gnutarget
19848 @item set gnutarget @var{args}
19849 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19850 knows whether it is reading an @dfn{executable},
19851 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19852 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19853 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19856 @emph{Warning:} To specify a file format with @code{set gnutarget},
19857 you must know the actual BFD name.
19861 @xref{Files, , Commands to Specify Files}.
19863 @kindex show gnutarget
19864 @item show gnutarget
19865 Use the @code{show gnutarget} command to display what file format
19866 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19867 @value{GDBN} will determine the file format for each file automatically,
19868 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19871 @cindex common targets
19872 Here are some common targets (available, or not, depending on the GDB
19877 @item target exec @var{program}
19878 @cindex executable file target
19879 An executable file. @samp{target exec @var{program}} is the same as
19880 @samp{exec-file @var{program}}.
19882 @item target core @var{filename}
19883 @cindex core dump file target
19884 A core dump file. @samp{target core @var{filename}} is the same as
19885 @samp{core-file @var{filename}}.
19887 @item target remote @var{medium}
19888 @cindex remote target
19889 A remote system connected to @value{GDBN} via a serial line or network
19890 connection. This command tells @value{GDBN} to use its own remote
19891 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19893 For example, if you have a board connected to @file{/dev/ttya} on the
19894 machine running @value{GDBN}, you could say:
19897 target remote /dev/ttya
19900 @code{target remote} supports the @code{load} command. This is only
19901 useful if you have some other way of getting the stub to the target
19902 system, and you can put it somewhere in memory where it won't get
19903 clobbered by the download.
19905 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19906 @cindex built-in simulator target
19907 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19915 works; however, you cannot assume that a specific memory map, device
19916 drivers, or even basic I/O is available, although some simulators do
19917 provide these. For info about any processor-specific simulator details,
19918 see the appropriate section in @ref{Embedded Processors, ,Embedded
19921 @item target native
19922 @cindex native target
19923 Setup for local/native process debugging. Useful to make the
19924 @code{run} command spawn native processes (likewise @code{attach},
19925 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19926 (@pxref{set auto-connect-native-target}).
19930 Different targets are available on different configurations of @value{GDBN};
19931 your configuration may have more or fewer targets.
19933 Many remote targets require you to download the executable's code once
19934 you've successfully established a connection. You may wish to control
19935 various aspects of this process.
19940 @kindex set hash@r{, for remote monitors}
19941 @cindex hash mark while downloading
19942 This command controls whether a hash mark @samp{#} is displayed while
19943 downloading a file to the remote monitor. If on, a hash mark is
19944 displayed after each S-record is successfully downloaded to the
19948 @kindex show hash@r{, for remote monitors}
19949 Show the current status of displaying the hash mark.
19951 @item set debug monitor
19952 @kindex set debug monitor
19953 @cindex display remote monitor communications
19954 Enable or disable display of communications messages between
19955 @value{GDBN} and the remote monitor.
19957 @item show debug monitor
19958 @kindex show debug monitor
19959 Show the current status of displaying communications between
19960 @value{GDBN} and the remote monitor.
19965 @kindex load @var{filename} @var{offset}
19966 @item load @var{filename} @var{offset}
19968 Depending on what remote debugging facilities are configured into
19969 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19970 is meant to make @var{filename} (an executable) available for debugging
19971 on the remote system---by downloading, or dynamic linking, for example.
19972 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19973 the @code{add-symbol-file} command.
19975 If your @value{GDBN} does not have a @code{load} command, attempting to
19976 execute it gets the error message ``@code{You can't do that when your
19977 target is @dots{}}''
19979 The file is loaded at whatever address is specified in the executable.
19980 For some object file formats, you can specify the load address when you
19981 link the program; for other formats, like a.out, the object file format
19982 specifies a fixed address.
19983 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19985 It is also possible to tell @value{GDBN} to load the executable file at a
19986 specific offset described by the optional argument @var{offset}. When
19987 @var{offset} is provided, @var{filename} must also be provided.
19989 Depending on the remote side capabilities, @value{GDBN} may be able to
19990 load programs into flash memory.
19992 @code{load} does not repeat if you press @key{RET} again after using it.
19997 @kindex flash-erase
19999 @anchor{flash-erase}
20001 Erases all known flash memory regions on the target.
20006 @section Choosing Target Byte Order
20008 @cindex choosing target byte order
20009 @cindex target byte order
20011 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20012 offer the ability to run either big-endian or little-endian byte
20013 orders. Usually the executable or symbol will include a bit to
20014 designate the endian-ness, and you will not need to worry about
20015 which to use. However, you may still find it useful to adjust
20016 @value{GDBN}'s idea of processor endian-ness manually.
20020 @item set endian big
20021 Instruct @value{GDBN} to assume the target is big-endian.
20023 @item set endian little
20024 Instruct @value{GDBN} to assume the target is little-endian.
20026 @item set endian auto
20027 Instruct @value{GDBN} to use the byte order associated with the
20031 Display @value{GDBN}'s current idea of the target byte order.
20035 Note that these commands merely adjust interpretation of symbolic
20036 data on the host, and that they have absolutely no effect on the
20040 @node Remote Debugging
20041 @chapter Debugging Remote Programs
20042 @cindex remote debugging
20044 If you are trying to debug a program running on a machine that cannot run
20045 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20046 For example, you might use remote debugging on an operating system kernel,
20047 or on a small system which does not have a general purpose operating system
20048 powerful enough to run a full-featured debugger.
20050 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20051 to make this work with particular debugging targets. In addition,
20052 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20053 but not specific to any particular target system) which you can use if you
20054 write the remote stubs---the code that runs on the remote system to
20055 communicate with @value{GDBN}.
20057 Other remote targets may be available in your
20058 configuration of @value{GDBN}; use @code{help target} to list them.
20061 * Connecting:: Connecting to a remote target
20062 * File Transfer:: Sending files to a remote system
20063 * Server:: Using the gdbserver program
20064 * Remote Configuration:: Remote configuration
20065 * Remote Stub:: Implementing a remote stub
20069 @section Connecting to a Remote Target
20070 @cindex remote debugging, connecting
20071 @cindex @code{gdbserver}, connecting
20072 @cindex remote debugging, types of connections
20073 @cindex @code{gdbserver}, types of connections
20074 @cindex @code{gdbserver}, @code{target remote} mode
20075 @cindex @code{gdbserver}, @code{target extended-remote} mode
20077 This section describes how to connect to a remote target, including the
20078 types of connections and their differences, how to set up executable and
20079 symbol files on the host and target, and the commands used for
20080 connecting to and disconnecting from the remote target.
20082 @subsection Types of Remote Connections
20084 @value{GDBN} supports two types of remote connections, @code{target remote}
20085 mode and @code{target extended-remote} mode. Note that many remote targets
20086 support only @code{target remote} mode. There are several major
20087 differences between the two types of connections, enumerated here:
20091 @cindex remote debugging, detach and program exit
20092 @item Result of detach or program exit
20093 @strong{With target remote mode:} When the debugged program exits or you
20094 detach from it, @value{GDBN} disconnects from the target. When using
20095 @code{gdbserver}, @code{gdbserver} will exit.
20097 @strong{With target extended-remote mode:} When the debugged program exits or
20098 you detach from it, @value{GDBN} remains connected to the target, even
20099 though no program is running. You can rerun the program, attach to a
20100 running program, or use @code{monitor} commands specific to the target.
20102 When using @code{gdbserver} in this case, it does not exit unless it was
20103 invoked using the @option{--once} option. If the @option{--once} option
20104 was not used, you can ask @code{gdbserver} to exit using the
20105 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20107 @item Specifying the program to debug
20108 For both connection types you use the @code{file} command to specify the
20109 program on the host system. If you are using @code{gdbserver} there are
20110 some differences in how to specify the location of the program on the
20113 @strong{With target remote mode:} You must either specify the program to debug
20114 on the @code{gdbserver} command line or use the @option{--attach} option
20115 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20117 @cindex @option{--multi}, @code{gdbserver} option
20118 @strong{With target extended-remote mode:} You may specify the program to debug
20119 on the @code{gdbserver} command line, or you can load the program or attach
20120 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20122 @anchor{--multi Option in Types of Remote Connnections}
20123 You can start @code{gdbserver} without supplying an initial command to run
20124 or process ID to attach. To do this, use the @option{--multi} command line
20125 option. Then you can connect using @code{target extended-remote} and start
20126 the program you want to debug (see below for details on using the
20127 @code{run} command in this scenario). Note that the conditions under which
20128 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20129 (@code{target remote} or @code{target extended-remote}). The
20130 @option{--multi} option to @code{gdbserver} has no influence on that.
20132 @item The @code{run} command
20133 @strong{With target remote mode:} The @code{run} command is not
20134 supported. Once a connection has been established, you can use all
20135 the usual @value{GDBN} commands to examine and change data. The
20136 remote program is already running, so you can use commands like
20137 @kbd{step} and @kbd{continue}.
20139 @strong{With target extended-remote mode:} The @code{run} command is
20140 supported. The @code{run} command uses the value set by
20141 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20142 the program to run. Command line arguments are supported, except for
20143 wildcard expansion and I/O redirection (@pxref{Arguments}).
20145 If you specify the program to debug on the command line, then the
20146 @code{run} command is not required to start execution, and you can
20147 resume using commands like @kbd{step} and @kbd{continue} as with
20148 @code{target remote} mode.
20150 @anchor{Attaching in Types of Remote Connections}
20152 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20153 not supported. To attach to a running program using @code{gdbserver}, you
20154 must use the @option{--attach} option (@pxref{Running gdbserver}).
20156 @strong{With target extended-remote mode:} To attach to a running program,
20157 you may use the @code{attach} command after the connection has been
20158 established. If you are using @code{gdbserver}, you may also invoke
20159 @code{gdbserver} using the @option{--attach} option
20160 (@pxref{Running gdbserver}).
20164 @anchor{Host and target files}
20165 @subsection Host and Target Files
20166 @cindex remote debugging, symbol files
20167 @cindex symbol files, remote debugging
20169 @value{GDBN}, running on the host, needs access to symbol and debugging
20170 information for your program running on the target. This requires
20171 access to an unstripped copy of your program, and possibly any associated
20172 symbol files. Note that this section applies equally to both @code{target
20173 remote} mode and @code{target extended-remote} mode.
20175 Some remote targets (@pxref{qXfer executable filename read}, and
20176 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20177 the same connection used to communicate with @value{GDBN}. With such a
20178 target, if the remote program is unstripped, the only command you need is
20179 @code{target remote} (or @code{target extended-remote}).
20181 If the remote program is stripped, or the target does not support remote
20182 program file access, start up @value{GDBN} using the name of the local
20183 unstripped copy of your program as the first argument, or use the
20184 @code{file} command. Use @code{set sysroot} to specify the location (on
20185 the host) of target libraries (unless your @value{GDBN} was compiled with
20186 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20187 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20190 The symbol file and target libraries must exactly match the executable
20191 and libraries on the target, with one exception: the files on the host
20192 system should not be stripped, even if the files on the target system
20193 are. Mismatched or missing files will lead to confusing results
20194 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20195 files may also prevent @code{gdbserver} from debugging multi-threaded
20198 @subsection Remote Connection Commands
20199 @cindex remote connection commands
20200 @value{GDBN} can communicate with the target over a serial line, or
20201 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20202 each case, @value{GDBN} uses the same protocol for debugging your
20203 program; only the medium carrying the debugging packets varies. The
20204 @code{target remote} and @code{target extended-remote} commands
20205 establish a connection to the target. Both commands accept the same
20206 arguments, which indicate the medium to use:
20210 @item target remote @var{serial-device}
20211 @itemx target extended-remote @var{serial-device}
20212 @cindex serial line, @code{target remote}
20213 Use @var{serial-device} to communicate with the target. For example,
20214 to use a serial line connected to the device named @file{/dev/ttyb}:
20217 target remote /dev/ttyb
20220 If you're using a serial line, you may want to give @value{GDBN} the
20221 @samp{--baud} option, or use the @code{set serial baud} command
20222 (@pxref{Remote Configuration, set serial baud}) before the
20223 @code{target} command.
20225 @item target remote @code{@var{host}:@var{port}}
20226 @itemx target remote @code{tcp:@var{host}:@var{port}}
20227 @itemx target extended-remote @code{@var{host}:@var{port}}
20228 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20229 @cindex @acronym{TCP} port, @code{target remote}
20230 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20231 The @var{host} may be either a host name or a numeric @acronym{IP}
20232 address; @var{port} must be a decimal number. The @var{host} could be
20233 the target machine itself, if it is directly connected to the net, or
20234 it might be a terminal server which in turn has a serial line to the
20237 For example, to connect to port 2828 on a terminal server named
20241 target remote manyfarms:2828
20244 If your remote target is actually running on the same machine as your
20245 debugger session (e.g.@: a simulator for your target running on the
20246 same host), you can omit the hostname. For example, to connect to
20247 port 1234 on your local machine:
20250 target remote :1234
20254 Note that the colon is still required here.
20256 @item target remote @code{udp:@var{host}:@var{port}}
20257 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20258 @cindex @acronym{UDP} port, @code{target remote}
20259 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20260 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20263 target remote udp:manyfarms:2828
20266 When using a @acronym{UDP} connection for remote debugging, you should
20267 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20268 can silently drop packets on busy or unreliable networks, which will
20269 cause havoc with your debugging session.
20271 @item target remote | @var{command}
20272 @itemx target extended-remote | @var{command}
20273 @cindex pipe, @code{target remote} to
20274 Run @var{command} in the background and communicate with it using a
20275 pipe. The @var{command} is a shell command, to be parsed and expanded
20276 by the system's command shell, @code{/bin/sh}; it should expect remote
20277 protocol packets on its standard input, and send replies on its
20278 standard output. You could use this to run a stand-alone simulator
20279 that speaks the remote debugging protocol, to make net connections
20280 using programs like @code{ssh}, or for other similar tricks.
20282 If @var{command} closes its standard output (perhaps by exiting),
20283 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20284 program has already exited, this will have no effect.)
20288 @cindex interrupting remote programs
20289 @cindex remote programs, interrupting
20290 Whenever @value{GDBN} is waiting for the remote program, if you type the
20291 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20292 program. This may or may not succeed, depending in part on the hardware
20293 and the serial drivers the remote system uses. If you type the
20294 interrupt character once again, @value{GDBN} displays this prompt:
20297 Interrupted while waiting for the program.
20298 Give up (and stop debugging it)? (y or n)
20301 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20302 the remote debugging session. (If you decide you want to try again later,
20303 you can use @kbd{target remote} again to connect once more.) If you type
20304 @kbd{n}, @value{GDBN} goes back to waiting.
20306 In @code{target extended-remote} mode, typing @kbd{n} will leave
20307 @value{GDBN} connected to the target.
20310 @kindex detach (remote)
20312 When you have finished debugging the remote program, you can use the
20313 @code{detach} command to release it from @value{GDBN} control.
20314 Detaching from the target normally resumes its execution, but the results
20315 will depend on your particular remote stub. After the @code{detach}
20316 command in @code{target remote} mode, @value{GDBN} is free to connect to
20317 another target. In @code{target extended-remote} mode, @value{GDBN} is
20318 still connected to the target.
20322 The @code{disconnect} command closes the connection to the target, and
20323 the target is generally not resumed. It will wait for @value{GDBN}
20324 (this instance or another one) to connect and continue debugging. After
20325 the @code{disconnect} command, @value{GDBN} is again free to connect to
20328 @cindex send command to remote monitor
20329 @cindex extend @value{GDBN} for remote targets
20330 @cindex add new commands for external monitor
20332 @item monitor @var{cmd}
20333 This command allows you to send arbitrary commands directly to the
20334 remote monitor. Since @value{GDBN} doesn't care about the commands it
20335 sends like this, this command is the way to extend @value{GDBN}---you
20336 can add new commands that only the external monitor will understand
20340 @node File Transfer
20341 @section Sending files to a remote system
20342 @cindex remote target, file transfer
20343 @cindex file transfer
20344 @cindex sending files to remote systems
20346 Some remote targets offer the ability to transfer files over the same
20347 connection used to communicate with @value{GDBN}. This is convenient
20348 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20349 running @code{gdbserver} over a network interface. For other targets,
20350 e.g.@: embedded devices with only a single serial port, this may be
20351 the only way to upload or download files.
20353 Not all remote targets support these commands.
20357 @item remote put @var{hostfile} @var{targetfile}
20358 Copy file @var{hostfile} from the host system (the machine running
20359 @value{GDBN}) to @var{targetfile} on the target system.
20362 @item remote get @var{targetfile} @var{hostfile}
20363 Copy file @var{targetfile} from the target system to @var{hostfile}
20364 on the host system.
20366 @kindex remote delete
20367 @item remote delete @var{targetfile}
20368 Delete @var{targetfile} from the target system.
20373 @section Using the @code{gdbserver} Program
20376 @cindex remote connection without stubs
20377 @code{gdbserver} is a control program for Unix-like systems, which
20378 allows you to connect your program with a remote @value{GDBN} via
20379 @code{target remote} or @code{target extended-remote}---but without
20380 linking in the usual debugging stub.
20382 @code{gdbserver} is not a complete replacement for the debugging stubs,
20383 because it requires essentially the same operating-system facilities
20384 that @value{GDBN} itself does. In fact, a system that can run
20385 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20386 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20387 because it is a much smaller program than @value{GDBN} itself. It is
20388 also easier to port than all of @value{GDBN}, so you may be able to get
20389 started more quickly on a new system by using @code{gdbserver}.
20390 Finally, if you develop code for real-time systems, you may find that
20391 the tradeoffs involved in real-time operation make it more convenient to
20392 do as much development work as possible on another system, for example
20393 by cross-compiling. You can use @code{gdbserver} to make a similar
20394 choice for debugging.
20396 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20397 or a TCP connection, using the standard @value{GDBN} remote serial
20401 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20402 Do not run @code{gdbserver} connected to any public network; a
20403 @value{GDBN} connection to @code{gdbserver} provides access to the
20404 target system with the same privileges as the user running
20408 @anchor{Running gdbserver}
20409 @subsection Running @code{gdbserver}
20410 @cindex arguments, to @code{gdbserver}
20411 @cindex @code{gdbserver}, command-line arguments
20413 Run @code{gdbserver} on the target system. You need a copy of the
20414 program you want to debug, including any libraries it requires.
20415 @code{gdbserver} does not need your program's symbol table, so you can
20416 strip the program if necessary to save space. @value{GDBN} on the host
20417 system does all the symbol handling.
20419 To use the server, you must tell it how to communicate with @value{GDBN};
20420 the name of your program; and the arguments for your program. The usual
20424 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20427 @var{comm} is either a device name (to use a serial line), or a TCP
20428 hostname and portnumber, or @code{-} or @code{stdio} to use
20429 stdin/stdout of @code{gdbserver}.
20430 For example, to debug Emacs with the argument
20431 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20435 target> gdbserver /dev/com1 emacs foo.txt
20438 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20441 To use a TCP connection instead of a serial line:
20444 target> gdbserver host:2345 emacs foo.txt
20447 The only difference from the previous example is the first argument,
20448 specifying that you are communicating with the host @value{GDBN} via
20449 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20450 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20451 (Currently, the @samp{host} part is ignored.) You can choose any number
20452 you want for the port number as long as it does not conflict with any
20453 TCP ports already in use on the target system (for example, @code{23} is
20454 reserved for @code{telnet}).@footnote{If you choose a port number that
20455 conflicts with another service, @code{gdbserver} prints an error message
20456 and exits.} You must use the same port number with the host @value{GDBN}
20457 @code{target remote} command.
20459 The @code{stdio} connection is useful when starting @code{gdbserver}
20463 (gdb) target remote | ssh -T hostname gdbserver - hello
20466 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20467 and we don't want escape-character handling. Ssh does this by default when
20468 a command is provided, the flag is provided to make it explicit.
20469 You could elide it if you want to.
20471 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20472 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20473 display through a pipe connected to gdbserver.
20474 Both @code{stdout} and @code{stderr} use the same pipe.
20476 @anchor{Attaching to a program}
20477 @subsubsection Attaching to a Running Program
20478 @cindex attach to a program, @code{gdbserver}
20479 @cindex @option{--attach}, @code{gdbserver} option
20481 On some targets, @code{gdbserver} can also attach to running programs.
20482 This is accomplished via the @code{--attach} argument. The syntax is:
20485 target> gdbserver --attach @var{comm} @var{pid}
20488 @var{pid} is the process ID of a currently running process. It isn't
20489 necessary to point @code{gdbserver} at a binary for the running process.
20491 In @code{target extended-remote} mode, you can also attach using the
20492 @value{GDBN} attach command
20493 (@pxref{Attaching in Types of Remote Connections}).
20496 You can debug processes by name instead of process ID if your target has the
20497 @code{pidof} utility:
20500 target> gdbserver --attach @var{comm} `pidof @var{program}`
20503 In case more than one copy of @var{program} is running, or @var{program}
20504 has multiple threads, most versions of @code{pidof} support the
20505 @code{-s} option to only return the first process ID.
20507 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20509 This section applies only when @code{gdbserver} is run to listen on a TCP
20512 @code{gdbserver} normally terminates after all of its debugged processes have
20513 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20514 extended-remote}, @code{gdbserver} stays running even with no processes left.
20515 @value{GDBN} normally terminates the spawned debugged process on its exit,
20516 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20517 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20518 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20519 stays running even in the @kbd{target remote} mode.
20521 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20522 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20523 completeness, at most one @value{GDBN} can be connected at a time.
20525 @cindex @option{--once}, @code{gdbserver} option
20526 By default, @code{gdbserver} keeps the listening TCP port open, so that
20527 subsequent connections are possible. However, if you start @code{gdbserver}
20528 with the @option{--once} option, it will stop listening for any further
20529 connection attempts after connecting to the first @value{GDBN} session. This
20530 means no further connections to @code{gdbserver} will be possible after the
20531 first one. It also means @code{gdbserver} will terminate after the first
20532 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20533 connections and even in the @kbd{target extended-remote} mode. The
20534 @option{--once} option allows reusing the same port number for connecting to
20535 multiple instances of @code{gdbserver} running on the same host, since each
20536 instance closes its port after the first connection.
20538 @anchor{Other Command-Line Arguments for gdbserver}
20539 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20541 You can use the @option{--multi} option to start @code{gdbserver} without
20542 specifying a program to debug or a process to attach to. Then you can
20543 attach in @code{target extended-remote} mode and run or attach to a
20544 program. For more information,
20545 @pxref{--multi Option in Types of Remote Connnections}.
20547 @cindex @option{--debug}, @code{gdbserver} option
20548 The @option{--debug} option tells @code{gdbserver} to display extra
20549 status information about the debugging process.
20550 @cindex @option{--remote-debug}, @code{gdbserver} option
20551 The @option{--remote-debug} option tells @code{gdbserver} to display
20552 remote protocol debug output. These options are intended for
20553 @code{gdbserver} development and for bug reports to the developers.
20555 @cindex @option{--debug-format}, @code{gdbserver} option
20556 The @option{--debug-format=option1[,option2,...]} option tells
20557 @code{gdbserver} to include additional information in each output.
20558 Possible options are:
20562 Turn off all extra information in debugging output.
20564 Turn on all extra information in debugging output.
20566 Include a timestamp in each line of debugging output.
20569 Options are processed in order. Thus, for example, if @option{none}
20570 appears last then no additional information is added to debugging output.
20572 @cindex @option{--wrapper}, @code{gdbserver} option
20573 The @option{--wrapper} option specifies a wrapper to launch programs
20574 for debugging. The option should be followed by the name of the
20575 wrapper, then any command-line arguments to pass to the wrapper, then
20576 @kbd{--} indicating the end of the wrapper arguments.
20578 @code{gdbserver} runs the specified wrapper program with a combined
20579 command line including the wrapper arguments, then the name of the
20580 program to debug, then any arguments to the program. The wrapper
20581 runs until it executes your program, and then @value{GDBN} gains control.
20583 You can use any program that eventually calls @code{execve} with
20584 its arguments as a wrapper. Several standard Unix utilities do
20585 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20586 with @code{exec "$@@"} will also work.
20588 For example, you can use @code{env} to pass an environment variable to
20589 the debugged program, without setting the variable in @code{gdbserver}'s
20593 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20596 @cindex @option{--selftest}
20597 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20600 $ gdbserver --selftest
20601 Ran 2 unit tests, 0 failed
20604 These tests are disabled in release.
20605 @subsection Connecting to @code{gdbserver}
20607 The basic procedure for connecting to the remote target is:
20611 Run @value{GDBN} on the host system.
20614 Make sure you have the necessary symbol files
20615 (@pxref{Host and target files}).
20616 Load symbols for your application using the @code{file} command before you
20617 connect. Use @code{set sysroot} to locate target libraries (unless your
20618 @value{GDBN} was compiled with the correct sysroot using
20619 @code{--with-sysroot}).
20622 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20623 For TCP connections, you must start up @code{gdbserver} prior to using
20624 the @code{target} command. Otherwise you may get an error whose
20625 text depends on the host system, but which usually looks something like
20626 @samp{Connection refused}. Don't use the @code{load}
20627 command in @value{GDBN} when using @code{target remote} mode, since the
20628 program is already on the target.
20632 @anchor{Monitor Commands for gdbserver}
20633 @subsection Monitor Commands for @code{gdbserver}
20634 @cindex monitor commands, for @code{gdbserver}
20636 During a @value{GDBN} session using @code{gdbserver}, you can use the
20637 @code{monitor} command to send special requests to @code{gdbserver}.
20638 Here are the available commands.
20642 List the available monitor commands.
20644 @item monitor set debug 0
20645 @itemx monitor set debug 1
20646 Disable or enable general debugging messages.
20648 @item monitor set remote-debug 0
20649 @itemx monitor set remote-debug 1
20650 Disable or enable specific debugging messages associated with the remote
20651 protocol (@pxref{Remote Protocol}).
20653 @item monitor set debug-format option1@r{[},option2,...@r{]}
20654 Specify additional text to add to debugging messages.
20655 Possible options are:
20659 Turn off all extra information in debugging output.
20661 Turn on all extra information in debugging output.
20663 Include a timestamp in each line of debugging output.
20666 Options are processed in order. Thus, for example, if @option{none}
20667 appears last then no additional information is added to debugging output.
20669 @item monitor set libthread-db-search-path [PATH]
20670 @cindex gdbserver, search path for @code{libthread_db}
20671 When this command is issued, @var{path} is a colon-separated list of
20672 directories to search for @code{libthread_db} (@pxref{Threads,,set
20673 libthread-db-search-path}). If you omit @var{path},
20674 @samp{libthread-db-search-path} will be reset to its default value.
20676 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20677 not supported in @code{gdbserver}.
20680 Tell gdbserver to exit immediately. This command should be followed by
20681 @code{disconnect} to close the debugging session. @code{gdbserver} will
20682 detach from any attached processes and kill any processes it created.
20683 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20684 of a multi-process mode debug session.
20688 @subsection Tracepoints support in @code{gdbserver}
20689 @cindex tracepoints support in @code{gdbserver}
20691 On some targets, @code{gdbserver} supports tracepoints, fast
20692 tracepoints and static tracepoints.
20694 For fast or static tracepoints to work, a special library called the
20695 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20696 This library is built and distributed as an integral part of
20697 @code{gdbserver}. In addition, support for static tracepoints
20698 requires building the in-process agent library with static tracepoints
20699 support. At present, the UST (LTTng Userspace Tracer,
20700 @url{http://lttng.org/ust}) tracing engine is supported. This support
20701 is automatically available if UST development headers are found in the
20702 standard include path when @code{gdbserver} is built, or if
20703 @code{gdbserver} was explicitly configured using @option{--with-ust}
20704 to point at such headers. You can explicitly disable the support
20705 using @option{--with-ust=no}.
20707 There are several ways to load the in-process agent in your program:
20710 @item Specifying it as dependency at link time
20712 You can link your program dynamically with the in-process agent
20713 library. On most systems, this is accomplished by adding
20714 @code{-linproctrace} to the link command.
20716 @item Using the system's preloading mechanisms
20718 You can force loading the in-process agent at startup time by using
20719 your system's support for preloading shared libraries. Many Unixes
20720 support the concept of preloading user defined libraries. In most
20721 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20722 in the environment. See also the description of @code{gdbserver}'s
20723 @option{--wrapper} command line option.
20725 @item Using @value{GDBN} to force loading the agent at run time
20727 On some systems, you can force the inferior to load a shared library,
20728 by calling a dynamic loader function in the inferior that takes care
20729 of dynamically looking up and loading a shared library. On most Unix
20730 systems, the function is @code{dlopen}. You'll use the @code{call}
20731 command for that. For example:
20734 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20737 Note that on most Unix systems, for the @code{dlopen} function to be
20738 available, the program needs to be linked with @code{-ldl}.
20741 On systems that have a userspace dynamic loader, like most Unix
20742 systems, when you connect to @code{gdbserver} using @code{target
20743 remote}, you'll find that the program is stopped at the dynamic
20744 loader's entry point, and no shared library has been loaded in the
20745 program's address space yet, including the in-process agent. In that
20746 case, before being able to use any of the fast or static tracepoints
20747 features, you need to let the loader run and load the shared
20748 libraries. The simplest way to do that is to run the program to the
20749 main procedure. E.g., if debugging a C or C@t{++} program, start
20750 @code{gdbserver} like so:
20753 $ gdbserver :9999 myprogram
20756 Start GDB and connect to @code{gdbserver} like so, and run to main:
20760 (@value{GDBP}) target remote myhost:9999
20761 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20762 (@value{GDBP}) b main
20763 (@value{GDBP}) continue
20766 The in-process tracing agent library should now be loaded into the
20767 process; you can confirm it with the @code{info sharedlibrary}
20768 command, which will list @file{libinproctrace.so} as loaded in the
20769 process. You are now ready to install fast tracepoints, list static
20770 tracepoint markers, probe static tracepoints markers, and start
20773 @node Remote Configuration
20774 @section Remote Configuration
20777 @kindex show remote
20778 This section documents the configuration options available when
20779 debugging remote programs. For the options related to the File I/O
20780 extensions of the remote protocol, see @ref{system,
20781 system-call-allowed}.
20784 @item set remoteaddresssize @var{bits}
20785 @cindex address size for remote targets
20786 @cindex bits in remote address
20787 Set the maximum size of address in a memory packet to the specified
20788 number of bits. @value{GDBN} will mask off the address bits above
20789 that number, when it passes addresses to the remote target. The
20790 default value is the number of bits in the target's address.
20792 @item show remoteaddresssize
20793 Show the current value of remote address size in bits.
20795 @item set serial baud @var{n}
20796 @cindex baud rate for remote targets
20797 Set the baud rate for the remote serial I/O to @var{n} baud. The
20798 value is used to set the speed of the serial port used for debugging
20801 @item show serial baud
20802 Show the current speed of the remote connection.
20804 @item set serial parity @var{parity}
20805 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20806 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20808 @item show serial parity
20809 Show the current parity of the serial port.
20811 @item set remotebreak
20812 @cindex interrupt remote programs
20813 @cindex BREAK signal instead of Ctrl-C
20814 @anchor{set remotebreak}
20815 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20816 when you type @kbd{Ctrl-c} to interrupt the program running
20817 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20818 character instead. The default is off, since most remote systems
20819 expect to see @samp{Ctrl-C} as the interrupt signal.
20821 @item show remotebreak
20822 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20823 interrupt the remote program.
20825 @item set remoteflow on
20826 @itemx set remoteflow off
20827 @kindex set remoteflow
20828 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20829 on the serial port used to communicate to the remote target.
20831 @item show remoteflow
20832 @kindex show remoteflow
20833 Show the current setting of hardware flow control.
20835 @item set remotelogbase @var{base}
20836 Set the base (a.k.a.@: radix) of logging serial protocol
20837 communications to @var{base}. Supported values of @var{base} are:
20838 @code{ascii}, @code{octal}, and @code{hex}. The default is
20841 @item show remotelogbase
20842 Show the current setting of the radix for logging remote serial
20845 @item set remotelogfile @var{file}
20846 @cindex record serial communications on file
20847 Record remote serial communications on the named @var{file}. The
20848 default is not to record at all.
20850 @item show remotelogfile.
20851 Show the current setting of the file name on which to record the
20852 serial communications.
20854 @item set remotetimeout @var{num}
20855 @cindex timeout for serial communications
20856 @cindex remote timeout
20857 Set the timeout limit to wait for the remote target to respond to
20858 @var{num} seconds. The default is 2 seconds.
20860 @item show remotetimeout
20861 Show the current number of seconds to wait for the remote target
20864 @cindex limit hardware breakpoints and watchpoints
20865 @cindex remote target, limit break- and watchpoints
20866 @anchor{set remote hardware-watchpoint-limit}
20867 @anchor{set remote hardware-breakpoint-limit}
20868 @item set remote hardware-watchpoint-limit @var{limit}
20869 @itemx set remote hardware-breakpoint-limit @var{limit}
20870 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20871 watchpoints. A limit of -1, the default, is treated as unlimited.
20873 @cindex limit hardware watchpoints length
20874 @cindex remote target, limit watchpoints length
20875 @anchor{set remote hardware-watchpoint-length-limit}
20876 @item set remote hardware-watchpoint-length-limit @var{limit}
20877 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20878 a remote hardware watchpoint. A limit of -1, the default, is treated
20881 @item show remote hardware-watchpoint-length-limit
20882 Show the current limit (in bytes) of the maximum length of
20883 a remote hardware watchpoint.
20885 @item set remote exec-file @var{filename}
20886 @itemx show remote exec-file
20887 @anchor{set remote exec-file}
20888 @cindex executable file, for remote target
20889 Select the file used for @code{run} with @code{target
20890 extended-remote}. This should be set to a filename valid on the
20891 target system. If it is not set, the target will use a default
20892 filename (e.g.@: the last program run).
20894 @item set remote interrupt-sequence
20895 @cindex interrupt remote programs
20896 @cindex select Ctrl-C, BREAK or BREAK-g
20897 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20898 @samp{BREAK-g} as the
20899 sequence to the remote target in order to interrupt the execution.
20900 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20901 is high level of serial line for some certain time.
20902 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20903 It is @code{BREAK} signal followed by character @code{g}.
20905 @item show interrupt-sequence
20906 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20907 is sent by @value{GDBN} to interrupt the remote program.
20908 @code{BREAK-g} is BREAK signal followed by @code{g} and
20909 also known as Magic SysRq g.
20911 @item set remote interrupt-on-connect
20912 @cindex send interrupt-sequence on start
20913 Specify whether interrupt-sequence is sent to remote target when
20914 @value{GDBN} connects to it. This is mostly needed when you debug
20915 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20916 which is known as Magic SysRq g in order to connect @value{GDBN}.
20918 @item show interrupt-on-connect
20919 Show whether interrupt-sequence is sent
20920 to remote target when @value{GDBN} connects to it.
20924 @item set tcp auto-retry on
20925 @cindex auto-retry, for remote TCP target
20926 Enable auto-retry for remote TCP connections. This is useful if the remote
20927 debugging agent is launched in parallel with @value{GDBN}; there is a race
20928 condition because the agent may not become ready to accept the connection
20929 before @value{GDBN} attempts to connect. When auto-retry is
20930 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20931 to establish the connection using the timeout specified by
20932 @code{set tcp connect-timeout}.
20934 @item set tcp auto-retry off
20935 Do not auto-retry failed TCP connections.
20937 @item show tcp auto-retry
20938 Show the current auto-retry setting.
20940 @item set tcp connect-timeout @var{seconds}
20941 @itemx set tcp connect-timeout unlimited
20942 @cindex connection timeout, for remote TCP target
20943 @cindex timeout, for remote target connection
20944 Set the timeout for establishing a TCP connection to the remote target to
20945 @var{seconds}. The timeout affects both polling to retry failed connections
20946 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20947 that are merely slow to complete, and represents an approximate cumulative
20948 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20949 @value{GDBN} will keep attempting to establish a connection forever,
20950 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20952 @item show tcp connect-timeout
20953 Show the current connection timeout setting.
20956 @cindex remote packets, enabling and disabling
20957 The @value{GDBN} remote protocol autodetects the packets supported by
20958 your debugging stub. If you need to override the autodetection, you
20959 can use these commands to enable or disable individual packets. Each
20960 packet can be set to @samp{on} (the remote target supports this
20961 packet), @samp{off} (the remote target does not support this packet),
20962 or @samp{auto} (detect remote target support for this packet). They
20963 all default to @samp{auto}. For more information about each packet,
20964 see @ref{Remote Protocol}.
20966 During normal use, you should not have to use any of these commands.
20967 If you do, that may be a bug in your remote debugging stub, or a bug
20968 in @value{GDBN}. You may want to report the problem to the
20969 @value{GDBN} developers.
20971 For each packet @var{name}, the command to enable or disable the
20972 packet is @code{set remote @var{name}-packet}. The available settings
20975 @multitable @columnfractions 0.28 0.32 0.25
20978 @tab Related Features
20980 @item @code{fetch-register}
20982 @tab @code{info registers}
20984 @item @code{set-register}
20988 @item @code{binary-download}
20990 @tab @code{load}, @code{set}
20992 @item @code{read-aux-vector}
20993 @tab @code{qXfer:auxv:read}
20994 @tab @code{info auxv}
20996 @item @code{symbol-lookup}
20997 @tab @code{qSymbol}
20998 @tab Detecting multiple threads
21000 @item @code{attach}
21001 @tab @code{vAttach}
21004 @item @code{verbose-resume}
21006 @tab Stepping or resuming multiple threads
21012 @item @code{software-breakpoint}
21016 @item @code{hardware-breakpoint}
21020 @item @code{write-watchpoint}
21024 @item @code{read-watchpoint}
21028 @item @code{access-watchpoint}
21032 @item @code{pid-to-exec-file}
21033 @tab @code{qXfer:exec-file:read}
21034 @tab @code{attach}, @code{run}
21036 @item @code{target-features}
21037 @tab @code{qXfer:features:read}
21038 @tab @code{set architecture}
21040 @item @code{library-info}
21041 @tab @code{qXfer:libraries:read}
21042 @tab @code{info sharedlibrary}
21044 @item @code{memory-map}
21045 @tab @code{qXfer:memory-map:read}
21046 @tab @code{info mem}
21048 @item @code{read-sdata-object}
21049 @tab @code{qXfer:sdata:read}
21050 @tab @code{print $_sdata}
21052 @item @code{read-spu-object}
21053 @tab @code{qXfer:spu:read}
21054 @tab @code{info spu}
21056 @item @code{write-spu-object}
21057 @tab @code{qXfer:spu:write}
21058 @tab @code{info spu}
21060 @item @code{read-siginfo-object}
21061 @tab @code{qXfer:siginfo:read}
21062 @tab @code{print $_siginfo}
21064 @item @code{write-siginfo-object}
21065 @tab @code{qXfer:siginfo:write}
21066 @tab @code{set $_siginfo}
21068 @item @code{threads}
21069 @tab @code{qXfer:threads:read}
21070 @tab @code{info threads}
21072 @item @code{get-thread-local-@*storage-address}
21073 @tab @code{qGetTLSAddr}
21074 @tab Displaying @code{__thread} variables
21076 @item @code{get-thread-information-block-address}
21077 @tab @code{qGetTIBAddr}
21078 @tab Display MS-Windows Thread Information Block.
21080 @item @code{search-memory}
21081 @tab @code{qSearch:memory}
21084 @item @code{supported-packets}
21085 @tab @code{qSupported}
21086 @tab Remote communications parameters
21088 @item @code{catch-syscalls}
21089 @tab @code{QCatchSyscalls}
21090 @tab @code{catch syscall}
21092 @item @code{pass-signals}
21093 @tab @code{QPassSignals}
21094 @tab @code{handle @var{signal}}
21096 @item @code{program-signals}
21097 @tab @code{QProgramSignals}
21098 @tab @code{handle @var{signal}}
21100 @item @code{hostio-close-packet}
21101 @tab @code{vFile:close}
21102 @tab @code{remote get}, @code{remote put}
21104 @item @code{hostio-open-packet}
21105 @tab @code{vFile:open}
21106 @tab @code{remote get}, @code{remote put}
21108 @item @code{hostio-pread-packet}
21109 @tab @code{vFile:pread}
21110 @tab @code{remote get}, @code{remote put}
21112 @item @code{hostio-pwrite-packet}
21113 @tab @code{vFile:pwrite}
21114 @tab @code{remote get}, @code{remote put}
21116 @item @code{hostio-unlink-packet}
21117 @tab @code{vFile:unlink}
21118 @tab @code{remote delete}
21120 @item @code{hostio-readlink-packet}
21121 @tab @code{vFile:readlink}
21124 @item @code{hostio-fstat-packet}
21125 @tab @code{vFile:fstat}
21128 @item @code{hostio-setfs-packet}
21129 @tab @code{vFile:setfs}
21132 @item @code{noack-packet}
21133 @tab @code{QStartNoAckMode}
21134 @tab Packet acknowledgment
21136 @item @code{osdata}
21137 @tab @code{qXfer:osdata:read}
21138 @tab @code{info os}
21140 @item @code{query-attached}
21141 @tab @code{qAttached}
21142 @tab Querying remote process attach state.
21144 @item @code{trace-buffer-size}
21145 @tab @code{QTBuffer:size}
21146 @tab @code{set trace-buffer-size}
21148 @item @code{trace-status}
21149 @tab @code{qTStatus}
21150 @tab @code{tstatus}
21152 @item @code{traceframe-info}
21153 @tab @code{qXfer:traceframe-info:read}
21154 @tab Traceframe info
21156 @item @code{install-in-trace}
21157 @tab @code{InstallInTrace}
21158 @tab Install tracepoint in tracing
21160 @item @code{disable-randomization}
21161 @tab @code{QDisableRandomization}
21162 @tab @code{set disable-randomization}
21164 @item @code{startup-with-shell}
21165 @tab @code{QStartupWithShell}
21166 @tab @code{set startup-with-shell}
21168 @item @code{environment-hex-encoded}
21169 @tab @code{QEnvironmentHexEncoded}
21170 @tab @code{set environment}
21172 @item @code{environment-unset}
21173 @tab @code{QEnvironmentUnset}
21174 @tab @code{unset environment}
21176 @item @code{environment-reset}
21177 @tab @code{QEnvironmentReset}
21178 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21180 @item @code{set-working-dir}
21181 @tab @code{QSetWorkingDir}
21182 @tab @code{set cwd}
21184 @item @code{conditional-breakpoints-packet}
21185 @tab @code{Z0 and Z1}
21186 @tab @code{Support for target-side breakpoint condition evaluation}
21188 @item @code{multiprocess-extensions}
21189 @tab @code{multiprocess extensions}
21190 @tab Debug multiple processes and remote process PID awareness
21192 @item @code{swbreak-feature}
21193 @tab @code{swbreak stop reason}
21196 @item @code{hwbreak-feature}
21197 @tab @code{hwbreak stop reason}
21200 @item @code{fork-event-feature}
21201 @tab @code{fork stop reason}
21204 @item @code{vfork-event-feature}
21205 @tab @code{vfork stop reason}
21208 @item @code{exec-event-feature}
21209 @tab @code{exec stop reason}
21212 @item @code{thread-events}
21213 @tab @code{QThreadEvents}
21214 @tab Tracking thread lifetime.
21216 @item @code{no-resumed-stop-reply}
21217 @tab @code{no resumed thread left stop reply}
21218 @tab Tracking thread lifetime.
21223 @section Implementing a Remote Stub
21225 @cindex debugging stub, example
21226 @cindex remote stub, example
21227 @cindex stub example, remote debugging
21228 The stub files provided with @value{GDBN} implement the target side of the
21229 communication protocol, and the @value{GDBN} side is implemented in the
21230 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21231 these subroutines to communicate, and ignore the details. (If you're
21232 implementing your own stub file, you can still ignore the details: start
21233 with one of the existing stub files. @file{sparc-stub.c} is the best
21234 organized, and therefore the easiest to read.)
21236 @cindex remote serial debugging, overview
21237 To debug a program running on another machine (the debugging
21238 @dfn{target} machine), you must first arrange for all the usual
21239 prerequisites for the program to run by itself. For example, for a C
21244 A startup routine to set up the C runtime environment; these usually
21245 have a name like @file{crt0}. The startup routine may be supplied by
21246 your hardware supplier, or you may have to write your own.
21249 A C subroutine library to support your program's
21250 subroutine calls, notably managing input and output.
21253 A way of getting your program to the other machine---for example, a
21254 download program. These are often supplied by the hardware
21255 manufacturer, but you may have to write your own from hardware
21259 The next step is to arrange for your program to use a serial port to
21260 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21261 machine). In general terms, the scheme looks like this:
21265 @value{GDBN} already understands how to use this protocol; when everything
21266 else is set up, you can simply use the @samp{target remote} command
21267 (@pxref{Targets,,Specifying a Debugging Target}).
21269 @item On the target,
21270 you must link with your program a few special-purpose subroutines that
21271 implement the @value{GDBN} remote serial protocol. The file containing these
21272 subroutines is called a @dfn{debugging stub}.
21274 On certain remote targets, you can use an auxiliary program
21275 @code{gdbserver} instead of linking a stub into your program.
21276 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21279 The debugging stub is specific to the architecture of the remote
21280 machine; for example, use @file{sparc-stub.c} to debug programs on
21283 @cindex remote serial stub list
21284 These working remote stubs are distributed with @value{GDBN}:
21289 @cindex @file{i386-stub.c}
21292 For Intel 386 and compatible architectures.
21295 @cindex @file{m68k-stub.c}
21296 @cindex Motorola 680x0
21298 For Motorola 680x0 architectures.
21301 @cindex @file{sh-stub.c}
21304 For Renesas SH architectures.
21307 @cindex @file{sparc-stub.c}
21309 For @sc{sparc} architectures.
21311 @item sparcl-stub.c
21312 @cindex @file{sparcl-stub.c}
21315 For Fujitsu @sc{sparclite} architectures.
21319 The @file{README} file in the @value{GDBN} distribution may list other
21320 recently added stubs.
21323 * Stub Contents:: What the stub can do for you
21324 * Bootstrapping:: What you must do for the stub
21325 * Debug Session:: Putting it all together
21328 @node Stub Contents
21329 @subsection What the Stub Can Do for You
21331 @cindex remote serial stub
21332 The debugging stub for your architecture supplies these three
21336 @item set_debug_traps
21337 @findex set_debug_traps
21338 @cindex remote serial stub, initialization
21339 This routine arranges for @code{handle_exception} to run when your
21340 program stops. You must call this subroutine explicitly in your
21341 program's startup code.
21343 @item handle_exception
21344 @findex handle_exception
21345 @cindex remote serial stub, main routine
21346 This is the central workhorse, but your program never calls it
21347 explicitly---the setup code arranges for @code{handle_exception} to
21348 run when a trap is triggered.
21350 @code{handle_exception} takes control when your program stops during
21351 execution (for example, on a breakpoint), and mediates communications
21352 with @value{GDBN} on the host machine. This is where the communications
21353 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21354 representative on the target machine. It begins by sending summary
21355 information on the state of your program, then continues to execute,
21356 retrieving and transmitting any information @value{GDBN} needs, until you
21357 execute a @value{GDBN} command that makes your program resume; at that point,
21358 @code{handle_exception} returns control to your own code on the target
21362 @cindex @code{breakpoint} subroutine, remote
21363 Use this auxiliary subroutine to make your program contain a
21364 breakpoint. Depending on the particular situation, this may be the only
21365 way for @value{GDBN} to get control. For instance, if your target
21366 machine has some sort of interrupt button, you won't need to call this;
21367 pressing the interrupt button transfers control to
21368 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21369 simply receiving characters on the serial port may also trigger a trap;
21370 again, in that situation, you don't need to call @code{breakpoint} from
21371 your own program---simply running @samp{target remote} from the host
21372 @value{GDBN} session gets control.
21374 Call @code{breakpoint} if none of these is true, or if you simply want
21375 to make certain your program stops at a predetermined point for the
21376 start of your debugging session.
21379 @node Bootstrapping
21380 @subsection What You Must Do for the Stub
21382 @cindex remote stub, support routines
21383 The debugging stubs that come with @value{GDBN} are set up for a particular
21384 chip architecture, but they have no information about the rest of your
21385 debugging target machine.
21387 First of all you need to tell the stub how to communicate with the
21391 @item int getDebugChar()
21392 @findex getDebugChar
21393 Write this subroutine to read a single character from the serial port.
21394 It may be identical to @code{getchar} for your target system; a
21395 different name is used to allow you to distinguish the two if you wish.
21397 @item void putDebugChar(int)
21398 @findex putDebugChar
21399 Write this subroutine to write a single character to the serial port.
21400 It may be identical to @code{putchar} for your target system; a
21401 different name is used to allow you to distinguish the two if you wish.
21404 @cindex control C, and remote debugging
21405 @cindex interrupting remote targets
21406 If you want @value{GDBN} to be able to stop your program while it is
21407 running, you need to use an interrupt-driven serial driver, and arrange
21408 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21409 character). That is the character which @value{GDBN} uses to tell the
21410 remote system to stop.
21412 Getting the debugging target to return the proper status to @value{GDBN}
21413 probably requires changes to the standard stub; one quick and dirty way
21414 is to just execute a breakpoint instruction (the ``dirty'' part is that
21415 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21417 Other routines you need to supply are:
21420 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21421 @findex exceptionHandler
21422 Write this function to install @var{exception_address} in the exception
21423 handling tables. You need to do this because the stub does not have any
21424 way of knowing what the exception handling tables on your target system
21425 are like (for example, the processor's table might be in @sc{rom},
21426 containing entries which point to a table in @sc{ram}).
21427 The @var{exception_number} specifies the exception which should be changed;
21428 its meaning is architecture-dependent (for example, different numbers
21429 might represent divide by zero, misaligned access, etc). When this
21430 exception occurs, control should be transferred directly to
21431 @var{exception_address}, and the processor state (stack, registers,
21432 and so on) should be just as it is when a processor exception occurs. So if
21433 you want to use a jump instruction to reach @var{exception_address}, it
21434 should be a simple jump, not a jump to subroutine.
21436 For the 386, @var{exception_address} should be installed as an interrupt
21437 gate so that interrupts are masked while the handler runs. The gate
21438 should be at privilege level 0 (the most privileged level). The
21439 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21440 help from @code{exceptionHandler}.
21442 @item void flush_i_cache()
21443 @findex flush_i_cache
21444 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21445 instruction cache, if any, on your target machine. If there is no
21446 instruction cache, this subroutine may be a no-op.
21448 On target machines that have instruction caches, @value{GDBN} requires this
21449 function to make certain that the state of your program is stable.
21453 You must also make sure this library routine is available:
21456 @item void *memset(void *, int, int)
21458 This is the standard library function @code{memset} that sets an area of
21459 memory to a known value. If you have one of the free versions of
21460 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21461 either obtain it from your hardware manufacturer, or write your own.
21464 If you do not use the GNU C compiler, you may need other standard
21465 library subroutines as well; this varies from one stub to another,
21466 but in general the stubs are likely to use any of the common library
21467 subroutines which @code{@value{NGCC}} generates as inline code.
21470 @node Debug Session
21471 @subsection Putting it All Together
21473 @cindex remote serial debugging summary
21474 In summary, when your program is ready to debug, you must follow these
21479 Make sure you have defined the supporting low-level routines
21480 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21482 @code{getDebugChar}, @code{putDebugChar},
21483 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21487 Insert these lines in your program's startup code, before the main
21488 procedure is called:
21495 On some machines, when a breakpoint trap is raised, the hardware
21496 automatically makes the PC point to the instruction after the
21497 breakpoint. If your machine doesn't do that, you may need to adjust
21498 @code{handle_exception} to arrange for it to return to the instruction
21499 after the breakpoint on this first invocation, so that your program
21500 doesn't keep hitting the initial breakpoint instead of making
21504 For the 680x0 stub only, you need to provide a variable called
21505 @code{exceptionHook}. Normally you just use:
21508 void (*exceptionHook)() = 0;
21512 but if before calling @code{set_debug_traps}, you set it to point to a
21513 function in your program, that function is called when
21514 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21515 error). The function indicated by @code{exceptionHook} is called with
21516 one parameter: an @code{int} which is the exception number.
21519 Compile and link together: your program, the @value{GDBN} debugging stub for
21520 your target architecture, and the supporting subroutines.
21523 Make sure you have a serial connection between your target machine and
21524 the @value{GDBN} host, and identify the serial port on the host.
21527 @c The "remote" target now provides a `load' command, so we should
21528 @c document that. FIXME.
21529 Download your program to your target machine (or get it there by
21530 whatever means the manufacturer provides), and start it.
21533 Start @value{GDBN} on the host, and connect to the target
21534 (@pxref{Connecting,,Connecting to a Remote Target}).
21538 @node Configurations
21539 @chapter Configuration-Specific Information
21541 While nearly all @value{GDBN} commands are available for all native and
21542 cross versions of the debugger, there are some exceptions. This chapter
21543 describes things that are only available in certain configurations.
21545 There are three major categories of configurations: native
21546 configurations, where the host and target are the same, embedded
21547 operating system configurations, which are usually the same for several
21548 different processor architectures, and bare embedded processors, which
21549 are quite different from each other.
21554 * Embedded Processors::
21561 This section describes details specific to particular native
21565 * BSD libkvm Interface:: Debugging BSD kernel memory images
21566 * SVR4 Process Information:: SVR4 process information
21567 * DJGPP Native:: Features specific to the DJGPP port
21568 * Cygwin Native:: Features specific to the Cygwin port
21569 * Hurd Native:: Features specific to @sc{gnu} Hurd
21570 * Darwin:: Features specific to Darwin
21573 @node BSD libkvm Interface
21574 @subsection BSD libkvm Interface
21577 @cindex kernel memory image
21578 @cindex kernel crash dump
21580 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21581 interface that provides a uniform interface for accessing kernel virtual
21582 memory images, including live systems and crash dumps. @value{GDBN}
21583 uses this interface to allow you to debug live kernels and kernel crash
21584 dumps on many native BSD configurations. This is implemented as a
21585 special @code{kvm} debugging target. For debugging a live system, load
21586 the currently running kernel into @value{GDBN} and connect to the
21590 (@value{GDBP}) @b{target kvm}
21593 For debugging crash dumps, provide the file name of the crash dump as an
21597 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21600 Once connected to the @code{kvm} target, the following commands are
21606 Set current context from the @dfn{Process Control Block} (PCB) address.
21609 Set current context from proc address. This command isn't available on
21610 modern FreeBSD systems.
21613 @node SVR4 Process Information
21614 @subsection SVR4 Process Information
21616 @cindex examine process image
21617 @cindex process info via @file{/proc}
21619 Many versions of SVR4 and compatible systems provide a facility called
21620 @samp{/proc} that can be used to examine the image of a running
21621 process using file-system subroutines.
21623 If @value{GDBN} is configured for an operating system with this
21624 facility, the command @code{info proc} is available to report
21625 information about the process running your program, or about any
21626 process running on your system. This includes, as of this writing,
21627 @sc{gnu}/Linux and Solaris, for example.
21629 This command may also work on core files that were created on a system
21630 that has the @samp{/proc} facility.
21636 @itemx info proc @var{process-id}
21637 Summarize available information about any running process. If a
21638 process ID is specified by @var{process-id}, display information about
21639 that process; otherwise display information about the program being
21640 debugged. The summary includes the debugged process ID, the command
21641 line used to invoke it, its current working directory, and its
21642 executable file's absolute file name.
21644 On some systems, @var{process-id} can be of the form
21645 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21646 within a process. If the optional @var{pid} part is missing, it means
21647 a thread from the process being debugged (the leading @samp{/} still
21648 needs to be present, or else @value{GDBN} will interpret the number as
21649 a process ID rather than a thread ID).
21651 @item info proc cmdline
21652 @cindex info proc cmdline
21653 Show the original command line of the process. This command is
21654 specific to @sc{gnu}/Linux.
21656 @item info proc cwd
21657 @cindex info proc cwd
21658 Show the current working directory of the process. This command is
21659 specific to @sc{gnu}/Linux.
21661 @item info proc exe
21662 @cindex info proc exe
21663 Show the name of executable of the process. This command is specific
21666 @item info proc mappings
21667 @cindex memory address space mappings
21668 Report the memory address space ranges accessible in the program, with
21669 information on whether the process has read, write, or execute access
21670 rights to each range. On @sc{gnu}/Linux systems, each memory range
21671 includes the object file which is mapped to that range, instead of the
21672 memory access rights to that range.
21674 @item info proc stat
21675 @itemx info proc status
21676 @cindex process detailed status information
21677 These subcommands are specific to @sc{gnu}/Linux systems. They show
21678 the process-related information, including the user ID and group ID;
21679 how many threads are there in the process; its virtual memory usage;
21680 the signals that are pending, blocked, and ignored; its TTY; its
21681 consumption of system and user time; its stack size; its @samp{nice}
21682 value; etc. For more information, see the @samp{proc} man page
21683 (type @kbd{man 5 proc} from your shell prompt).
21685 @item info proc all
21686 Show all the information about the process described under all of the
21687 above @code{info proc} subcommands.
21690 @comment These sub-options of 'info proc' were not included when
21691 @comment procfs.c was re-written. Keep their descriptions around
21692 @comment against the day when someone finds the time to put them back in.
21693 @kindex info proc times
21694 @item info proc times
21695 Starting time, user CPU time, and system CPU time for your program and
21698 @kindex info proc id
21700 Report on the process IDs related to your program: its own process ID,
21701 the ID of its parent, the process group ID, and the session ID.
21704 @item set procfs-trace
21705 @kindex set procfs-trace
21706 @cindex @code{procfs} API calls
21707 This command enables and disables tracing of @code{procfs} API calls.
21709 @item show procfs-trace
21710 @kindex show procfs-trace
21711 Show the current state of @code{procfs} API call tracing.
21713 @item set procfs-file @var{file}
21714 @kindex set procfs-file
21715 Tell @value{GDBN} to write @code{procfs} API trace to the named
21716 @var{file}. @value{GDBN} appends the trace info to the previous
21717 contents of the file. The default is to display the trace on the
21720 @item show procfs-file
21721 @kindex show procfs-file
21722 Show the file to which @code{procfs} API trace is written.
21724 @item proc-trace-entry
21725 @itemx proc-trace-exit
21726 @itemx proc-untrace-entry
21727 @itemx proc-untrace-exit
21728 @kindex proc-trace-entry
21729 @kindex proc-trace-exit
21730 @kindex proc-untrace-entry
21731 @kindex proc-untrace-exit
21732 These commands enable and disable tracing of entries into and exits
21733 from the @code{syscall} interface.
21736 @kindex info pidlist
21737 @cindex process list, QNX Neutrino
21738 For QNX Neutrino only, this command displays the list of all the
21739 processes and all the threads within each process.
21742 @kindex info meminfo
21743 @cindex mapinfo list, QNX Neutrino
21744 For QNX Neutrino only, this command displays the list of all mapinfos.
21748 @subsection Features for Debugging @sc{djgpp} Programs
21749 @cindex @sc{djgpp} debugging
21750 @cindex native @sc{djgpp} debugging
21751 @cindex MS-DOS-specific commands
21754 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21755 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21756 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21757 top of real-mode DOS systems and their emulations.
21759 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21760 defines a few commands specific to the @sc{djgpp} port. This
21761 subsection describes those commands.
21766 This is a prefix of @sc{djgpp}-specific commands which print
21767 information about the target system and important OS structures.
21770 @cindex MS-DOS system info
21771 @cindex free memory information (MS-DOS)
21772 @item info dos sysinfo
21773 This command displays assorted information about the underlying
21774 platform: the CPU type and features, the OS version and flavor, the
21775 DPMI version, and the available conventional and DPMI memory.
21780 @cindex segment descriptor tables
21781 @cindex descriptor tables display
21783 @itemx info dos ldt
21784 @itemx info dos idt
21785 These 3 commands display entries from, respectively, Global, Local,
21786 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21787 tables are data structures which store a descriptor for each segment
21788 that is currently in use. The segment's selector is an index into a
21789 descriptor table; the table entry for that index holds the
21790 descriptor's base address and limit, and its attributes and access
21793 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21794 segment (used for both data and the stack), and a DOS segment (which
21795 allows access to DOS/BIOS data structures and absolute addresses in
21796 conventional memory). However, the DPMI host will usually define
21797 additional segments in order to support the DPMI environment.
21799 @cindex garbled pointers
21800 These commands allow to display entries from the descriptor tables.
21801 Without an argument, all entries from the specified table are
21802 displayed. An argument, which should be an integer expression, means
21803 display a single entry whose index is given by the argument. For
21804 example, here's a convenient way to display information about the
21805 debugged program's data segment:
21808 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21809 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21813 This comes in handy when you want to see whether a pointer is outside
21814 the data segment's limit (i.e.@: @dfn{garbled}).
21816 @cindex page tables display (MS-DOS)
21818 @itemx info dos pte
21819 These two commands display entries from, respectively, the Page
21820 Directory and the Page Tables. Page Directories and Page Tables are
21821 data structures which control how virtual memory addresses are mapped
21822 into physical addresses. A Page Table includes an entry for every
21823 page of memory that is mapped into the program's address space; there
21824 may be several Page Tables, each one holding up to 4096 entries. A
21825 Page Directory has up to 4096 entries, one each for every Page Table
21826 that is currently in use.
21828 Without an argument, @kbd{info dos pde} displays the entire Page
21829 Directory, and @kbd{info dos pte} displays all the entries in all of
21830 the Page Tables. An argument, an integer expression, given to the
21831 @kbd{info dos pde} command means display only that entry from the Page
21832 Directory table. An argument given to the @kbd{info dos pte} command
21833 means display entries from a single Page Table, the one pointed to by
21834 the specified entry in the Page Directory.
21836 @cindex direct memory access (DMA) on MS-DOS
21837 These commands are useful when your program uses @dfn{DMA} (Direct
21838 Memory Access), which needs physical addresses to program the DMA
21841 These commands are supported only with some DPMI servers.
21843 @cindex physical address from linear address
21844 @item info dos address-pte @var{addr}
21845 This command displays the Page Table entry for a specified linear
21846 address. The argument @var{addr} is a linear address which should
21847 already have the appropriate segment's base address added to it,
21848 because this command accepts addresses which may belong to @emph{any}
21849 segment. For example, here's how to display the Page Table entry for
21850 the page where a variable @code{i} is stored:
21853 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21854 @exdent @code{Page Table entry for address 0x11a00d30:}
21855 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21859 This says that @code{i} is stored at offset @code{0xd30} from the page
21860 whose physical base address is @code{0x02698000}, and shows all the
21861 attributes of that page.
21863 Note that you must cast the addresses of variables to a @code{char *},
21864 since otherwise the value of @code{__djgpp_base_address}, the base
21865 address of all variables and functions in a @sc{djgpp} program, will
21866 be added using the rules of C pointer arithmetics: if @code{i} is
21867 declared an @code{int}, @value{GDBN} will add 4 times the value of
21868 @code{__djgpp_base_address} to the address of @code{i}.
21870 Here's another example, it displays the Page Table entry for the
21874 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21875 @exdent @code{Page Table entry for address 0x29110:}
21876 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21880 (The @code{+ 3} offset is because the transfer buffer's address is the
21881 3rd member of the @code{_go32_info_block} structure.) The output
21882 clearly shows that this DPMI server maps the addresses in conventional
21883 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21884 linear (@code{0x29110}) addresses are identical.
21886 This command is supported only with some DPMI servers.
21889 @cindex DOS serial data link, remote debugging
21890 In addition to native debugging, the DJGPP port supports remote
21891 debugging via a serial data link. The following commands are specific
21892 to remote serial debugging in the DJGPP port of @value{GDBN}.
21895 @kindex set com1base
21896 @kindex set com1irq
21897 @kindex set com2base
21898 @kindex set com2irq
21899 @kindex set com3base
21900 @kindex set com3irq
21901 @kindex set com4base
21902 @kindex set com4irq
21903 @item set com1base @var{addr}
21904 This command sets the base I/O port address of the @file{COM1} serial
21907 @item set com1irq @var{irq}
21908 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21909 for the @file{COM1} serial port.
21911 There are similar commands @samp{set com2base}, @samp{set com3irq},
21912 etc.@: for setting the port address and the @code{IRQ} lines for the
21915 @kindex show com1base
21916 @kindex show com1irq
21917 @kindex show com2base
21918 @kindex show com2irq
21919 @kindex show com3base
21920 @kindex show com3irq
21921 @kindex show com4base
21922 @kindex show com4irq
21923 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21924 display the current settings of the base address and the @code{IRQ}
21925 lines used by the COM ports.
21928 @kindex info serial
21929 @cindex DOS serial port status
21930 This command prints the status of the 4 DOS serial ports. For each
21931 port, it prints whether it's active or not, its I/O base address and
21932 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21933 counts of various errors encountered so far.
21937 @node Cygwin Native
21938 @subsection Features for Debugging MS Windows PE Executables
21939 @cindex MS Windows debugging
21940 @cindex native Cygwin debugging
21941 @cindex Cygwin-specific commands
21943 @value{GDBN} supports native debugging of MS Windows programs, including
21944 DLLs with and without symbolic debugging information.
21946 @cindex Ctrl-BREAK, MS-Windows
21947 @cindex interrupt debuggee on MS-Windows
21948 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21949 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21950 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21951 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21952 sequence, which can be used to interrupt the debuggee even if it
21955 There are various additional Cygwin-specific commands, described in
21956 this section. Working with DLLs that have no debugging symbols is
21957 described in @ref{Non-debug DLL Symbols}.
21962 This is a prefix of MS Windows-specific commands which print
21963 information about the target system and important OS structures.
21965 @item info w32 selector
21966 This command displays information returned by
21967 the Win32 API @code{GetThreadSelectorEntry} function.
21968 It takes an optional argument that is evaluated to
21969 a long value to give the information about this given selector.
21970 Without argument, this command displays information
21971 about the six segment registers.
21973 @item info w32 thread-information-block
21974 This command displays thread specific information stored in the
21975 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21976 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21978 @kindex signal-event
21979 @item signal-event @var{id}
21980 This command signals an event with user-provided @var{id}. Used to resume
21981 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21983 To use it, create or edit the following keys in
21984 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21985 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21986 (for x86_64 versions):
21990 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21991 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21992 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21994 The first @code{%ld} will be replaced by the process ID of the
21995 crashing process, the second @code{%ld} will be replaced by the ID of
21996 the event that blocks the crashing process, waiting for @value{GDBN}
22000 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22001 make the system run debugger specified by the Debugger key
22002 automatically, @code{0} will cause a dialog box with ``OK'' and
22003 ``Cancel'' buttons to appear, which allows the user to either
22004 terminate the crashing process (OK) or debug it (Cancel).
22007 @kindex set cygwin-exceptions
22008 @cindex debugging the Cygwin DLL
22009 @cindex Cygwin DLL, debugging
22010 @item set cygwin-exceptions @var{mode}
22011 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22012 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22013 @value{GDBN} will delay recognition of exceptions, and may ignore some
22014 exceptions which seem to be caused by internal Cygwin DLL
22015 ``bookkeeping''. This option is meant primarily for debugging the
22016 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22017 @value{GDBN} users with false @code{SIGSEGV} signals.
22019 @kindex show cygwin-exceptions
22020 @item show cygwin-exceptions
22021 Displays whether @value{GDBN} will break on exceptions that happen
22022 inside the Cygwin DLL itself.
22024 @kindex set new-console
22025 @item set new-console @var{mode}
22026 If @var{mode} is @code{on} the debuggee will
22027 be started in a new console on next start.
22028 If @var{mode} is @code{off}, the debuggee will
22029 be started in the same console as the debugger.
22031 @kindex show new-console
22032 @item show new-console
22033 Displays whether a new console is used
22034 when the debuggee is started.
22036 @kindex set new-group
22037 @item set new-group @var{mode}
22038 This boolean value controls whether the debuggee should
22039 start a new group or stay in the same group as the debugger.
22040 This affects the way the Windows OS handles
22043 @kindex show new-group
22044 @item show new-group
22045 Displays current value of new-group boolean.
22047 @kindex set debugevents
22048 @item set debugevents
22049 This boolean value adds debug output concerning kernel events related
22050 to the debuggee seen by the debugger. This includes events that
22051 signal thread and process creation and exit, DLL loading and
22052 unloading, console interrupts, and debugging messages produced by the
22053 Windows @code{OutputDebugString} API call.
22055 @kindex set debugexec
22056 @item set debugexec
22057 This boolean value adds debug output concerning execute events
22058 (such as resume thread) seen by the debugger.
22060 @kindex set debugexceptions
22061 @item set debugexceptions
22062 This boolean value adds debug output concerning exceptions in the
22063 debuggee seen by the debugger.
22065 @kindex set debugmemory
22066 @item set debugmemory
22067 This boolean value adds debug output concerning debuggee memory reads
22068 and writes by the debugger.
22072 This boolean values specifies whether the debuggee is called
22073 via a shell or directly (default value is on).
22077 Displays if the debuggee will be started with a shell.
22082 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22085 @node Non-debug DLL Symbols
22086 @subsubsection Support for DLLs without Debugging Symbols
22087 @cindex DLLs with no debugging symbols
22088 @cindex Minimal symbols and DLLs
22090 Very often on windows, some of the DLLs that your program relies on do
22091 not include symbolic debugging information (for example,
22092 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22093 symbols in a DLL, it relies on the minimal amount of symbolic
22094 information contained in the DLL's export table. This section
22095 describes working with such symbols, known internally to @value{GDBN} as
22096 ``minimal symbols''.
22098 Note that before the debugged program has started execution, no DLLs
22099 will have been loaded. The easiest way around this problem is simply to
22100 start the program --- either by setting a breakpoint or letting the
22101 program run once to completion.
22103 @subsubsection DLL Name Prefixes
22105 In keeping with the naming conventions used by the Microsoft debugging
22106 tools, DLL export symbols are made available with a prefix based on the
22107 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22108 also entered into the symbol table, so @code{CreateFileA} is often
22109 sufficient. In some cases there will be name clashes within a program
22110 (particularly if the executable itself includes full debugging symbols)
22111 necessitating the use of the fully qualified name when referring to the
22112 contents of the DLL. Use single-quotes around the name to avoid the
22113 exclamation mark (``!'') being interpreted as a language operator.
22115 Note that the internal name of the DLL may be all upper-case, even
22116 though the file name of the DLL is lower-case, or vice-versa. Since
22117 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22118 some confusion. If in doubt, try the @code{info functions} and
22119 @code{info variables} commands or even @code{maint print msymbols}
22120 (@pxref{Symbols}). Here's an example:
22123 (@value{GDBP}) info function CreateFileA
22124 All functions matching regular expression "CreateFileA":
22126 Non-debugging symbols:
22127 0x77e885f4 CreateFileA
22128 0x77e885f4 KERNEL32!CreateFileA
22132 (@value{GDBP}) info function !
22133 All functions matching regular expression "!":
22135 Non-debugging symbols:
22136 0x6100114c cygwin1!__assert
22137 0x61004034 cygwin1!_dll_crt0@@0
22138 0x61004240 cygwin1!dll_crt0(per_process *)
22142 @subsubsection Working with Minimal Symbols
22144 Symbols extracted from a DLL's export table do not contain very much
22145 type information. All that @value{GDBN} can do is guess whether a symbol
22146 refers to a function or variable depending on the linker section that
22147 contains the symbol. Also note that the actual contents of the memory
22148 contained in a DLL are not available unless the program is running. This
22149 means that you cannot examine the contents of a variable or disassemble
22150 a function within a DLL without a running program.
22152 Variables are generally treated as pointers and dereferenced
22153 automatically. For this reason, it is often necessary to prefix a
22154 variable name with the address-of operator (``&'') and provide explicit
22155 type information in the command. Here's an example of the type of
22159 (@value{GDBP}) print 'cygwin1!__argv'
22160 'cygwin1!__argv' has unknown type; cast it to its declared type
22164 (@value{GDBP}) x 'cygwin1!__argv'
22165 'cygwin1!__argv' has unknown type; cast it to its declared type
22168 And two possible solutions:
22171 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22172 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22176 (@value{GDBP}) x/2x &'cygwin1!__argv'
22177 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22178 (@value{GDBP}) x/x 0x10021608
22179 0x10021608: 0x0022fd98
22180 (@value{GDBP}) x/s 0x0022fd98
22181 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22184 Setting a break point within a DLL is possible even before the program
22185 starts execution. However, under these circumstances, @value{GDBN} can't
22186 examine the initial instructions of the function in order to skip the
22187 function's frame set-up code. You can work around this by using ``*&''
22188 to set the breakpoint at a raw memory address:
22191 (@value{GDBP}) break *&'python22!PyOS_Readline'
22192 Breakpoint 1 at 0x1e04eff0
22195 The author of these extensions is not entirely convinced that setting a
22196 break point within a shared DLL like @file{kernel32.dll} is completely
22200 @subsection Commands Specific to @sc{gnu} Hurd Systems
22201 @cindex @sc{gnu} Hurd debugging
22203 This subsection describes @value{GDBN} commands specific to the
22204 @sc{gnu} Hurd native debugging.
22209 @kindex set signals@r{, Hurd command}
22210 @kindex set sigs@r{, Hurd command}
22211 This command toggles the state of inferior signal interception by
22212 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22213 affected by this command. @code{sigs} is a shorthand alias for
22218 @kindex show signals@r{, Hurd command}
22219 @kindex show sigs@r{, Hurd command}
22220 Show the current state of intercepting inferior's signals.
22222 @item set signal-thread
22223 @itemx set sigthread
22224 @kindex set signal-thread
22225 @kindex set sigthread
22226 This command tells @value{GDBN} which thread is the @code{libc} signal
22227 thread. That thread is run when a signal is delivered to a running
22228 process. @code{set sigthread} is the shorthand alias of @code{set
22231 @item show signal-thread
22232 @itemx show sigthread
22233 @kindex show signal-thread
22234 @kindex show sigthread
22235 These two commands show which thread will run when the inferior is
22236 delivered a signal.
22239 @kindex set stopped@r{, Hurd command}
22240 This commands tells @value{GDBN} that the inferior process is stopped,
22241 as with the @code{SIGSTOP} signal. The stopped process can be
22242 continued by delivering a signal to it.
22245 @kindex show stopped@r{, Hurd command}
22246 This command shows whether @value{GDBN} thinks the debuggee is
22249 @item set exceptions
22250 @kindex set exceptions@r{, Hurd command}
22251 Use this command to turn off trapping of exceptions in the inferior.
22252 When exception trapping is off, neither breakpoints nor
22253 single-stepping will work. To restore the default, set exception
22256 @item show exceptions
22257 @kindex show exceptions@r{, Hurd command}
22258 Show the current state of trapping exceptions in the inferior.
22260 @item set task pause
22261 @kindex set task@r{, Hurd commands}
22262 @cindex task attributes (@sc{gnu} Hurd)
22263 @cindex pause current task (@sc{gnu} Hurd)
22264 This command toggles task suspension when @value{GDBN} has control.
22265 Setting it to on takes effect immediately, and the task is suspended
22266 whenever @value{GDBN} gets control. Setting it to off will take
22267 effect the next time the inferior is continued. If this option is set
22268 to off, you can use @code{set thread default pause on} or @code{set
22269 thread pause on} (see below) to pause individual threads.
22271 @item show task pause
22272 @kindex show task@r{, Hurd commands}
22273 Show the current state of task suspension.
22275 @item set task detach-suspend-count
22276 @cindex task suspend count
22277 @cindex detach from task, @sc{gnu} Hurd
22278 This command sets the suspend count the task will be left with when
22279 @value{GDBN} detaches from it.
22281 @item show task detach-suspend-count
22282 Show the suspend count the task will be left with when detaching.
22284 @item set task exception-port
22285 @itemx set task excp
22286 @cindex task exception port, @sc{gnu} Hurd
22287 This command sets the task exception port to which @value{GDBN} will
22288 forward exceptions. The argument should be the value of the @dfn{send
22289 rights} of the task. @code{set task excp} is a shorthand alias.
22291 @item set noninvasive
22292 @cindex noninvasive task options
22293 This command switches @value{GDBN} to a mode that is the least
22294 invasive as far as interfering with the inferior is concerned. This
22295 is the same as using @code{set task pause}, @code{set exceptions}, and
22296 @code{set signals} to values opposite to the defaults.
22298 @item info send-rights
22299 @itemx info receive-rights
22300 @itemx info port-rights
22301 @itemx info port-sets
22302 @itemx info dead-names
22305 @cindex send rights, @sc{gnu} Hurd
22306 @cindex receive rights, @sc{gnu} Hurd
22307 @cindex port rights, @sc{gnu} Hurd
22308 @cindex port sets, @sc{gnu} Hurd
22309 @cindex dead names, @sc{gnu} Hurd
22310 These commands display information about, respectively, send rights,
22311 receive rights, port rights, port sets, and dead names of a task.
22312 There are also shorthand aliases: @code{info ports} for @code{info
22313 port-rights} and @code{info psets} for @code{info port-sets}.
22315 @item set thread pause
22316 @kindex set thread@r{, Hurd command}
22317 @cindex thread properties, @sc{gnu} Hurd
22318 @cindex pause current thread (@sc{gnu} Hurd)
22319 This command toggles current thread suspension when @value{GDBN} has
22320 control. Setting it to on takes effect immediately, and the current
22321 thread is suspended whenever @value{GDBN} gets control. Setting it to
22322 off will take effect the next time the inferior is continued.
22323 Normally, this command has no effect, since when @value{GDBN} has
22324 control, the whole task is suspended. However, if you used @code{set
22325 task pause off} (see above), this command comes in handy to suspend
22326 only the current thread.
22328 @item show thread pause
22329 @kindex show thread@r{, Hurd command}
22330 This command shows the state of current thread suspension.
22332 @item set thread run
22333 This command sets whether the current thread is allowed to run.
22335 @item show thread run
22336 Show whether the current thread is allowed to run.
22338 @item set thread detach-suspend-count
22339 @cindex thread suspend count, @sc{gnu} Hurd
22340 @cindex detach from thread, @sc{gnu} Hurd
22341 This command sets the suspend count @value{GDBN} will leave on a
22342 thread when detaching. This number is relative to the suspend count
22343 found by @value{GDBN} when it notices the thread; use @code{set thread
22344 takeover-suspend-count} to force it to an absolute value.
22346 @item show thread detach-suspend-count
22347 Show the suspend count @value{GDBN} will leave on the thread when
22350 @item set thread exception-port
22351 @itemx set thread excp
22352 Set the thread exception port to which to forward exceptions. This
22353 overrides the port set by @code{set task exception-port} (see above).
22354 @code{set thread excp} is the shorthand alias.
22356 @item set thread takeover-suspend-count
22357 Normally, @value{GDBN}'s thread suspend counts are relative to the
22358 value @value{GDBN} finds when it notices each thread. This command
22359 changes the suspend counts to be absolute instead.
22361 @item set thread default
22362 @itemx show thread default
22363 @cindex thread default settings, @sc{gnu} Hurd
22364 Each of the above @code{set thread} commands has a @code{set thread
22365 default} counterpart (e.g., @code{set thread default pause}, @code{set
22366 thread default exception-port}, etc.). The @code{thread default}
22367 variety of commands sets the default thread properties for all
22368 threads; you can then change the properties of individual threads with
22369 the non-default commands.
22376 @value{GDBN} provides the following commands specific to the Darwin target:
22379 @item set debug darwin @var{num}
22380 @kindex set debug darwin
22381 When set to a non zero value, enables debugging messages specific to
22382 the Darwin support. Higher values produce more verbose output.
22384 @item show debug darwin
22385 @kindex show debug darwin
22386 Show the current state of Darwin messages.
22388 @item set debug mach-o @var{num}
22389 @kindex set debug mach-o
22390 When set to a non zero value, enables debugging messages while
22391 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22392 file format used on Darwin for object and executable files.) Higher
22393 values produce more verbose output. This is a command to diagnose
22394 problems internal to @value{GDBN} and should not be needed in normal
22397 @item show debug mach-o
22398 @kindex show debug mach-o
22399 Show the current state of Mach-O file messages.
22401 @item set mach-exceptions on
22402 @itemx set mach-exceptions off
22403 @kindex set mach-exceptions
22404 On Darwin, faults are first reported as a Mach exception and are then
22405 mapped to a Posix signal. Use this command to turn on trapping of
22406 Mach exceptions in the inferior. This might be sometimes useful to
22407 better understand the cause of a fault. The default is off.
22409 @item show mach-exceptions
22410 @kindex show mach-exceptions
22411 Show the current state of exceptions trapping.
22416 @section Embedded Operating Systems
22418 This section describes configurations involving the debugging of
22419 embedded operating systems that are available for several different
22422 @value{GDBN} includes the ability to debug programs running on
22423 various real-time operating systems.
22425 @node Embedded Processors
22426 @section Embedded Processors
22428 This section goes into details specific to particular embedded
22431 @cindex send command to simulator
22432 Whenever a specific embedded processor has a simulator, @value{GDBN}
22433 allows to send an arbitrary command to the simulator.
22436 @item sim @var{command}
22437 @kindex sim@r{, a command}
22438 Send an arbitrary @var{command} string to the simulator. Consult the
22439 documentation for the specific simulator in use for information about
22440 acceptable commands.
22445 * ARC:: Synopsys ARC
22447 * M68K:: Motorola M68K
22448 * MicroBlaze:: Xilinx MicroBlaze
22449 * MIPS Embedded:: MIPS Embedded
22450 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22451 * PowerPC Embedded:: PowerPC Embedded
22454 * Super-H:: Renesas Super-H
22458 @subsection Synopsys ARC
22459 @cindex Synopsys ARC
22460 @cindex ARC specific commands
22466 @value{GDBN} provides the following ARC-specific commands:
22469 @item set debug arc
22470 @kindex set debug arc
22471 Control the level of ARC specific debug messages. Use 0 for no messages (the
22472 default), 1 for debug messages, and 2 for even more debug messages.
22474 @item show debug arc
22475 @kindex show debug arc
22476 Show the level of ARC specific debugging in operation.
22478 @item maint print arc arc-instruction @var{address}
22479 @kindex maint print arc arc-instruction
22480 Print internal disassembler information about instruction at a given address.
22487 @value{GDBN} provides the following ARM-specific commands:
22490 @item set arm disassembler
22492 This commands selects from a list of disassembly styles. The
22493 @code{"std"} style is the standard style.
22495 @item show arm disassembler
22497 Show the current disassembly style.
22499 @item set arm apcs32
22500 @cindex ARM 32-bit mode
22501 This command toggles ARM operation mode between 32-bit and 26-bit.
22503 @item show arm apcs32
22504 Display the current usage of the ARM 32-bit mode.
22506 @item set arm fpu @var{fputype}
22507 This command sets the ARM floating-point unit (FPU) type. The
22508 argument @var{fputype} can be one of these:
22512 Determine the FPU type by querying the OS ABI.
22514 Software FPU, with mixed-endian doubles on little-endian ARM
22517 GCC-compiled FPA co-processor.
22519 Software FPU with pure-endian doubles.
22525 Show the current type of the FPU.
22528 This command forces @value{GDBN} to use the specified ABI.
22531 Show the currently used ABI.
22533 @item set arm fallback-mode (arm|thumb|auto)
22534 @value{GDBN} uses the symbol table, when available, to determine
22535 whether instructions are ARM or Thumb. This command controls
22536 @value{GDBN}'s default behavior when the symbol table is not
22537 available. The default is @samp{auto}, which causes @value{GDBN} to
22538 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22541 @item show arm fallback-mode
22542 Show the current fallback instruction mode.
22544 @item set arm force-mode (arm|thumb|auto)
22545 This command overrides use of the symbol table to determine whether
22546 instructions are ARM or Thumb. The default is @samp{auto}, which
22547 causes @value{GDBN} to use the symbol table and then the setting
22548 of @samp{set arm fallback-mode}.
22550 @item show arm force-mode
22551 Show the current forced instruction mode.
22553 @item set debug arm
22554 Toggle whether to display ARM-specific debugging messages from the ARM
22555 target support subsystem.
22557 @item show debug arm
22558 Show whether ARM-specific debugging messages are enabled.
22562 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22563 The @value{GDBN} ARM simulator accepts the following optional arguments.
22566 @item --swi-support=@var{type}
22567 Tell the simulator which SWI interfaces to support. The argument
22568 @var{type} may be a comma separated list of the following values.
22569 The default value is @code{all}.
22584 The Motorola m68k configuration includes ColdFire support.
22587 @subsection MicroBlaze
22588 @cindex Xilinx MicroBlaze
22589 @cindex XMD, Xilinx Microprocessor Debugger
22591 The MicroBlaze is a soft-core processor supported on various Xilinx
22592 FPGAs, such as Spartan or Virtex series. Boards with these processors
22593 usually have JTAG ports which connect to a host system running the Xilinx
22594 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22595 This host system is used to download the configuration bitstream to
22596 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22597 communicates with the target board using the JTAG interface and
22598 presents a @code{gdbserver} interface to the board. By default
22599 @code{xmd} uses port @code{1234}. (While it is possible to change
22600 this default port, it requires the use of undocumented @code{xmd}
22601 commands. Contact Xilinx support if you need to do this.)
22603 Use these GDB commands to connect to the MicroBlaze target processor.
22606 @item target remote :1234
22607 Use this command to connect to the target if you are running @value{GDBN}
22608 on the same system as @code{xmd}.
22610 @item target remote @var{xmd-host}:1234
22611 Use this command to connect to the target if it is connected to @code{xmd}
22612 running on a different system named @var{xmd-host}.
22615 Use this command to download a program to the MicroBlaze target.
22617 @item set debug microblaze @var{n}
22618 Enable MicroBlaze-specific debugging messages if non-zero.
22620 @item show debug microblaze @var{n}
22621 Show MicroBlaze-specific debugging level.
22624 @node MIPS Embedded
22625 @subsection @acronym{MIPS} Embedded
22628 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22631 @item set mipsfpu double
22632 @itemx set mipsfpu single
22633 @itemx set mipsfpu none
22634 @itemx set mipsfpu auto
22635 @itemx show mipsfpu
22636 @kindex set mipsfpu
22637 @kindex show mipsfpu
22638 @cindex @acronym{MIPS} remote floating point
22639 @cindex floating point, @acronym{MIPS} remote
22640 If your target board does not support the @acronym{MIPS} floating point
22641 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22642 need this, you may wish to put the command in your @value{GDBN} init
22643 file). This tells @value{GDBN} how to find the return value of
22644 functions which return floating point values. It also allows
22645 @value{GDBN} to avoid saving the floating point registers when calling
22646 functions on the board. If you are using a floating point coprocessor
22647 with only single precision floating point support, as on the @sc{r4650}
22648 processor, use the command @samp{set mipsfpu single}. The default
22649 double precision floating point coprocessor may be selected using
22650 @samp{set mipsfpu double}.
22652 In previous versions the only choices were double precision or no
22653 floating point, so @samp{set mipsfpu on} will select double precision
22654 and @samp{set mipsfpu off} will select no floating point.
22656 As usual, you can inquire about the @code{mipsfpu} variable with
22657 @samp{show mipsfpu}.
22660 @node OpenRISC 1000
22661 @subsection OpenRISC 1000
22662 @cindex OpenRISC 1000
22665 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22666 mainly provided as a soft-core which can run on Xilinx, Altera and other
22669 @value{GDBN} for OpenRISC supports the below commands when connecting to
22677 Runs the builtin CPU simulator which can run very basic
22678 programs but does not support most hardware functions like MMU.
22679 For more complex use cases the user is advised to run an external
22680 target, and connect using @samp{target remote}.
22682 Example: @code{target sim}
22684 @item set debug or1k
22685 Toggle whether to display OpenRISC-specific debugging messages from the
22686 OpenRISC target support subsystem.
22688 @item show debug or1k
22689 Show whether OpenRISC-specific debugging messages are enabled.
22692 @node PowerPC Embedded
22693 @subsection PowerPC Embedded
22695 @cindex DVC register
22696 @value{GDBN} supports using the DVC (Data Value Compare) register to
22697 implement in hardware simple hardware watchpoint conditions of the form:
22700 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22701 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22704 The DVC register will be automatically used when @value{GDBN} detects
22705 such pattern in a condition expression, and the created watchpoint uses one
22706 debug register (either the @code{exact-watchpoints} option is on and the
22707 variable is scalar, or the variable has a length of one byte). This feature
22708 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22711 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22712 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22713 in which case watchpoints using only one debug register are created when
22714 watching variables of scalar types.
22716 You can create an artificial array to watch an arbitrary memory
22717 region using one of the following commands (@pxref{Expressions}):
22720 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22721 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22724 PowerPC embedded processors support masked watchpoints. See the discussion
22725 about the @code{mask} argument in @ref{Set Watchpoints}.
22727 @cindex ranged breakpoint
22728 PowerPC embedded processors support hardware accelerated
22729 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22730 the inferior whenever it executes an instruction at any address within
22731 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22732 use the @code{break-range} command.
22734 @value{GDBN} provides the following PowerPC-specific commands:
22737 @kindex break-range
22738 @item break-range @var{start-location}, @var{end-location}
22739 Set a breakpoint for an address range given by
22740 @var{start-location} and @var{end-location}, which can specify a function name,
22741 a line number, an offset of lines from the current line or from the start
22742 location, or an address of an instruction (see @ref{Specify Location},
22743 for a list of all the possible ways to specify a @var{location}.)
22744 The breakpoint will stop execution of the inferior whenever it
22745 executes an instruction at any address within the specified range,
22746 (including @var{start-location} and @var{end-location}.)
22748 @kindex set powerpc
22749 @item set powerpc soft-float
22750 @itemx show powerpc soft-float
22751 Force @value{GDBN} to use (or not use) a software floating point calling
22752 convention. By default, @value{GDBN} selects the calling convention based
22753 on the selected architecture and the provided executable file.
22755 @item set powerpc vector-abi
22756 @itemx show powerpc vector-abi
22757 Force @value{GDBN} to use the specified calling convention for vector
22758 arguments and return values. The valid options are @samp{auto};
22759 @samp{generic}, to avoid vector registers even if they are present;
22760 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22761 registers. By default, @value{GDBN} selects the calling convention
22762 based on the selected architecture and the provided executable file.
22764 @item set powerpc exact-watchpoints
22765 @itemx show powerpc exact-watchpoints
22766 Allow @value{GDBN} to use only one debug register when watching a variable
22767 of scalar type, thus assuming that the variable is accessed through the
22768 address of its first byte.
22773 @subsection Atmel AVR
22776 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22777 following AVR-specific commands:
22780 @item info io_registers
22781 @kindex info io_registers@r{, AVR}
22782 @cindex I/O registers (Atmel AVR)
22783 This command displays information about the AVR I/O registers. For
22784 each register, @value{GDBN} prints its number and value.
22791 When configured for debugging CRIS, @value{GDBN} provides the
22792 following CRIS-specific commands:
22795 @item set cris-version @var{ver}
22796 @cindex CRIS version
22797 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22798 The CRIS version affects register names and sizes. This command is useful in
22799 case autodetection of the CRIS version fails.
22801 @item show cris-version
22802 Show the current CRIS version.
22804 @item set cris-dwarf2-cfi
22805 @cindex DWARF-2 CFI and CRIS
22806 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22807 Change to @samp{off} when using @code{gcc-cris} whose version is below
22810 @item show cris-dwarf2-cfi
22811 Show the current state of using DWARF-2 CFI.
22813 @item set cris-mode @var{mode}
22815 Set the current CRIS mode to @var{mode}. It should only be changed when
22816 debugging in guru mode, in which case it should be set to
22817 @samp{guru} (the default is @samp{normal}).
22819 @item show cris-mode
22820 Show the current CRIS mode.
22824 @subsection Renesas Super-H
22827 For the Renesas Super-H processor, @value{GDBN} provides these
22831 @item set sh calling-convention @var{convention}
22832 @kindex set sh calling-convention
22833 Set the calling-convention used when calling functions from @value{GDBN}.
22834 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22835 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22836 convention. If the DWARF-2 information of the called function specifies
22837 that the function follows the Renesas calling convention, the function
22838 is called using the Renesas calling convention. If the calling convention
22839 is set to @samp{renesas}, the Renesas calling convention is always used,
22840 regardless of the DWARF-2 information. This can be used to override the
22841 default of @samp{gcc} if debug information is missing, or the compiler
22842 does not emit the DWARF-2 calling convention entry for a function.
22844 @item show sh calling-convention
22845 @kindex show sh calling-convention
22846 Show the current calling convention setting.
22851 @node Architectures
22852 @section Architectures
22854 This section describes characteristics of architectures that affect
22855 all uses of @value{GDBN} with the architecture, both native and cross.
22862 * HPPA:: HP PA architecture
22863 * SPU:: Cell Broadband Engine SPU architecture
22870 @subsection AArch64
22871 @cindex AArch64 support
22873 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22874 following special commands:
22877 @item set debug aarch64
22878 @kindex set debug aarch64
22879 This command determines whether AArch64 architecture-specific debugging
22880 messages are to be displayed.
22882 @item show debug aarch64
22883 Show whether AArch64 debugging messages are displayed.
22888 @subsection x86 Architecture-specific Issues
22891 @item set struct-convention @var{mode}
22892 @kindex set struct-convention
22893 @cindex struct return convention
22894 @cindex struct/union returned in registers
22895 Set the convention used by the inferior to return @code{struct}s and
22896 @code{union}s from functions to @var{mode}. Possible values of
22897 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22898 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22899 are returned on the stack, while @code{"reg"} means that a
22900 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22901 be returned in a register.
22903 @item show struct-convention
22904 @kindex show struct-convention
22905 Show the current setting of the convention to return @code{struct}s
22910 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22911 @cindex Intel Memory Protection Extensions (MPX).
22913 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22914 @footnote{The register named with capital letters represent the architecture
22915 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22916 which are the lower bound and upper bound. Bounds are effective addresses or
22917 memory locations. The upper bounds are architecturally represented in 1's
22918 complement form. A bound having lower bound = 0, and upper bound = 0
22919 (1's complement of all bits set) will allow access to the entire address space.
22921 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22922 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22923 display the upper bound performing the complement of one operation on the
22924 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22925 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22926 can also be noted that the upper bounds are inclusive.
22928 As an example, assume that the register BND0 holds bounds for a pointer having
22929 access allowed for the range between 0x32 and 0x71. The values present on
22930 bnd0raw and bnd registers are presented as follows:
22933 bnd0raw = @{0x32, 0xffffffff8e@}
22934 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22937 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22938 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22939 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22940 Python, the display includes the memory size, in bits, accessible to
22943 Bounds can also be stored in bounds tables, which are stored in
22944 application memory. These tables store bounds for pointers by specifying
22945 the bounds pointer's value along with its bounds. Evaluating and changing
22946 bounds located in bound tables is therefore interesting while investigating
22947 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22950 @item show mpx bound @var{pointer}
22951 @kindex show mpx bound
22952 Display bounds of the given @var{pointer}.
22954 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22955 @kindex set mpx bound
22956 Set the bounds of a pointer in the bound table.
22957 This command takes three parameters: @var{pointer} is the pointers
22958 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22959 for lower and upper bounds respectively.
22962 When you call an inferior function on an Intel MPX enabled program,
22963 GDB sets the inferior's bound registers to the init (disabled) state
22964 before calling the function. As a consequence, bounds checks for the
22965 pointer arguments passed to the function will always pass.
22967 This is necessary because when you call an inferior function, the
22968 program is usually in the middle of the execution of other function.
22969 Since at that point bound registers are in an arbitrary state, not
22970 clearing them would lead to random bound violations in the called
22973 You can still examine the influence of the bound registers on the
22974 execution of the called function by stopping the execution of the
22975 called function at its prologue, setting bound registers, and
22976 continuing the execution. For example:
22980 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22981 $ print upper (a, b, c, d, 1)
22982 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22984 @{lbound = 0x0, ubound = ffffffff@} : size -1
22987 At this last step the value of bnd0 can be changed for investigation of bound
22988 violations caused along the execution of the call. In order to know how to
22989 set the bound registers or bound table for the call consult the ABI.
22994 See the following section.
22997 @subsection @acronym{MIPS}
22999 @cindex stack on Alpha
23000 @cindex stack on @acronym{MIPS}
23001 @cindex Alpha stack
23002 @cindex @acronym{MIPS} stack
23003 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23004 sometimes requires @value{GDBN} to search backward in the object code to
23005 find the beginning of a function.
23007 @cindex response time, @acronym{MIPS} debugging
23008 To improve response time (especially for embedded applications, where
23009 @value{GDBN} may be restricted to a slow serial line for this search)
23010 you may want to limit the size of this search, using one of these
23014 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23015 @item set heuristic-fence-post @var{limit}
23016 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23017 search for the beginning of a function. A value of @var{0} (the
23018 default) means there is no limit. However, except for @var{0}, the
23019 larger the limit the more bytes @code{heuristic-fence-post} must search
23020 and therefore the longer it takes to run. You should only need to use
23021 this command when debugging a stripped executable.
23023 @item show heuristic-fence-post
23024 Display the current limit.
23028 These commands are available @emph{only} when @value{GDBN} is configured
23029 for debugging programs on Alpha or @acronym{MIPS} processors.
23031 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23035 @item set mips abi @var{arg}
23036 @kindex set mips abi
23037 @cindex set ABI for @acronym{MIPS}
23038 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23039 values of @var{arg} are:
23043 The default ABI associated with the current binary (this is the
23053 @item show mips abi
23054 @kindex show mips abi
23055 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23057 @item set mips compression @var{arg}
23058 @kindex set mips compression
23059 @cindex code compression, @acronym{MIPS}
23060 Tell @value{GDBN} which @acronym{MIPS} compressed
23061 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23062 inferior. @value{GDBN} uses this for code disassembly and other
23063 internal interpretation purposes. This setting is only referred to
23064 when no executable has been associated with the debugging session or
23065 the executable does not provide information about the encoding it uses.
23066 Otherwise this setting is automatically updated from information
23067 provided by the executable.
23069 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23070 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23071 executables containing @acronym{MIPS16} code frequently are not
23072 identified as such.
23074 This setting is ``sticky''; that is, it retains its value across
23075 debugging sessions until reset either explicitly with this command or
23076 implicitly from an executable.
23078 The compiler and/or assembler typically add symbol table annotations to
23079 identify functions compiled for the @acronym{MIPS16} or
23080 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23081 are present, @value{GDBN} uses them in preference to the global
23082 compressed @acronym{ISA} encoding setting.
23084 @item show mips compression
23085 @kindex show mips compression
23086 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23087 @value{GDBN} to debug the inferior.
23090 @itemx show mipsfpu
23091 @xref{MIPS Embedded, set mipsfpu}.
23093 @item set mips mask-address @var{arg}
23094 @kindex set mips mask-address
23095 @cindex @acronym{MIPS} addresses, masking
23096 This command determines whether the most-significant 32 bits of 64-bit
23097 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23098 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23099 setting, which lets @value{GDBN} determine the correct value.
23101 @item show mips mask-address
23102 @kindex show mips mask-address
23103 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23106 @item set remote-mips64-transfers-32bit-regs
23107 @kindex set remote-mips64-transfers-32bit-regs
23108 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23109 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23110 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23111 and 64 bits for other registers, set this option to @samp{on}.
23113 @item show remote-mips64-transfers-32bit-regs
23114 @kindex show remote-mips64-transfers-32bit-regs
23115 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23117 @item set debug mips
23118 @kindex set debug mips
23119 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23120 target code in @value{GDBN}.
23122 @item show debug mips
23123 @kindex show debug mips
23124 Show the current setting of @acronym{MIPS} debugging messages.
23130 @cindex HPPA support
23132 When @value{GDBN} is debugging the HP PA architecture, it provides the
23133 following special commands:
23136 @item set debug hppa
23137 @kindex set debug hppa
23138 This command determines whether HPPA architecture-specific debugging
23139 messages are to be displayed.
23141 @item show debug hppa
23142 Show whether HPPA debugging messages are displayed.
23144 @item maint print unwind @var{address}
23145 @kindex maint print unwind@r{, HPPA}
23146 This command displays the contents of the unwind table entry at the
23147 given @var{address}.
23153 @subsection Cell Broadband Engine SPU architecture
23154 @cindex Cell Broadband Engine
23157 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23158 it provides the following special commands:
23161 @item info spu event
23163 Display SPU event facility status. Shows current event mask
23164 and pending event status.
23166 @item info spu signal
23167 Display SPU signal notification facility status. Shows pending
23168 signal-control word and signal notification mode of both signal
23169 notification channels.
23171 @item info spu mailbox
23172 Display SPU mailbox facility status. Shows all pending entries,
23173 in order of processing, in each of the SPU Write Outbound,
23174 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23177 Display MFC DMA status. Shows all pending commands in the MFC
23178 DMA queue. For each entry, opcode, tag, class IDs, effective
23179 and local store addresses and transfer size are shown.
23181 @item info spu proxydma
23182 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23183 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23184 and local store addresses and transfer size are shown.
23188 When @value{GDBN} is debugging a combined PowerPC/SPU application
23189 on the Cell Broadband Engine, it provides in addition the following
23193 @item set spu stop-on-load @var{arg}
23195 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23196 will give control to the user when a new SPE thread enters its @code{main}
23197 function. The default is @code{off}.
23199 @item show spu stop-on-load
23201 Show whether to stop for new SPE threads.
23203 @item set spu auto-flush-cache @var{arg}
23204 Set whether to automatically flush the software-managed cache. When set to
23205 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23206 cache to be flushed whenever SPE execution stops. This provides a consistent
23207 view of PowerPC memory that is accessed via the cache. If an application
23208 does not use the software-managed cache, this option has no effect.
23210 @item show spu auto-flush-cache
23211 Show whether to automatically flush the software-managed cache.
23216 @subsection PowerPC
23217 @cindex PowerPC architecture
23219 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23220 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23221 numbers stored in the floating point registers. These values must be stored
23222 in two consecutive registers, always starting at an even register like
23223 @code{f0} or @code{f2}.
23225 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23226 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23227 @code{f2} and @code{f3} for @code{$dl1} and so on.
23229 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23230 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23233 @subsection Nios II
23234 @cindex Nios II architecture
23236 When @value{GDBN} is debugging the Nios II architecture,
23237 it provides the following special commands:
23241 @item set debug nios2
23242 @kindex set debug nios2
23243 This command turns on and off debugging messages for the Nios II
23244 target code in @value{GDBN}.
23246 @item show debug nios2
23247 @kindex show debug nios2
23248 Show the current setting of Nios II debugging messages.
23252 @subsection Sparc64
23253 @cindex Sparc64 support
23254 @cindex Application Data Integrity
23255 @subsubsection ADI Support
23257 The M7 processor supports an Application Data Integrity (ADI) feature that
23258 detects invalid data accesses. When software allocates memory and enables
23259 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23260 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23261 the 4-bit version in every cacheline of that data. Hardware saves the latter
23262 in spare bits in the cache and memory hierarchy. On each load and store,
23263 the processor compares the upper 4 VA (virtual address) bits to the
23264 cacheline's version. If there is a mismatch, the processor generates a
23265 version mismatch trap which can be either precise or disrupting. The trap
23266 is an error condition which the kernel delivers to the process as a SIGSEGV
23269 Note that only 64-bit applications can use ADI and need to be built with
23272 Values of the ADI version tags, which are in granularity of a
23273 cacheline (64 bytes), can be viewed or modified.
23277 @kindex adi examine
23278 @item adi (examine | x) [ / @var{n} ] @var{addr}
23280 The @code{adi examine} command displays the value of one ADI version tag per
23283 @var{n} is a decimal integer specifying the number in bytes; the default
23284 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23285 block size, to display.
23287 @var{addr} is the address in user address space where you want @value{GDBN}
23288 to begin displaying the ADI version tags.
23290 Below is an example of displaying ADI versions of variable "shmaddr".
23293 (@value{GDBP}) adi x/100 shmaddr
23294 0xfff800010002c000: 0 0
23298 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23300 The @code{adi assign} command is used to assign new ADI version tag
23303 @var{n} is a decimal integer specifying the number in bytes;
23304 the default is 1. It specifies how much ADI version information, at the
23305 ratio of 1:ADI block size, to modify.
23307 @var{addr} is the address in user address space where you want @value{GDBN}
23308 to begin modifying the ADI version tags.
23310 @var{tag} is the new ADI version tag.
23312 For example, do the following to modify then verify ADI versions of
23313 variable "shmaddr":
23316 (@value{GDBP}) adi a/100 shmaddr = 7
23317 (@value{GDBP}) adi x/100 shmaddr
23318 0xfff800010002c000: 7 7
23323 @node Controlling GDB
23324 @chapter Controlling @value{GDBN}
23326 You can alter the way @value{GDBN} interacts with you by using the
23327 @code{set} command. For commands controlling how @value{GDBN} displays
23328 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23333 * Editing:: Command editing
23334 * Command History:: Command history
23335 * Screen Size:: Screen size
23336 * Numbers:: Numbers
23337 * ABI:: Configuring the current ABI
23338 * Auto-loading:: Automatically loading associated files
23339 * Messages/Warnings:: Optional warnings and messages
23340 * Debugging Output:: Optional messages about internal happenings
23341 * Other Misc Settings:: Other Miscellaneous Settings
23349 @value{GDBN} indicates its readiness to read a command by printing a string
23350 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23351 can change the prompt string with the @code{set prompt} command. For
23352 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23353 the prompt in one of the @value{GDBN} sessions so that you can always tell
23354 which one you are talking to.
23356 @emph{Note:} @code{set prompt} does not add a space for you after the
23357 prompt you set. This allows you to set a prompt which ends in a space
23358 or a prompt that does not.
23362 @item set prompt @var{newprompt}
23363 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23365 @kindex show prompt
23367 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23370 Versions of @value{GDBN} that ship with Python scripting enabled have
23371 prompt extensions. The commands for interacting with these extensions
23375 @kindex set extended-prompt
23376 @item set extended-prompt @var{prompt}
23377 Set an extended prompt that allows for substitutions.
23378 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23379 substitution. Any escape sequences specified as part of the prompt
23380 string are replaced with the corresponding strings each time the prompt
23386 set extended-prompt Current working directory: \w (gdb)
23389 Note that when an extended-prompt is set, it takes control of the
23390 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23392 @kindex show extended-prompt
23393 @item show extended-prompt
23394 Prints the extended prompt. Any escape sequences specified as part of
23395 the prompt string with @code{set extended-prompt}, are replaced with the
23396 corresponding strings each time the prompt is displayed.
23400 @section Command Editing
23402 @cindex command line editing
23404 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23405 @sc{gnu} library provides consistent behavior for programs which provide a
23406 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23407 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23408 substitution, and a storage and recall of command history across
23409 debugging sessions.
23411 You may control the behavior of command line editing in @value{GDBN} with the
23412 command @code{set}.
23415 @kindex set editing
23418 @itemx set editing on
23419 Enable command line editing (enabled by default).
23421 @item set editing off
23422 Disable command line editing.
23424 @kindex show editing
23426 Show whether command line editing is enabled.
23429 @ifset SYSTEM_READLINE
23430 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23432 @ifclear SYSTEM_READLINE
23433 @xref{Command Line Editing},
23435 for more details about the Readline
23436 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23437 encouraged to read that chapter.
23439 @node Command History
23440 @section Command History
23441 @cindex command history
23443 @value{GDBN} can keep track of the commands you type during your
23444 debugging sessions, so that you can be certain of precisely what
23445 happened. Use these commands to manage the @value{GDBN} command
23448 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23449 package, to provide the history facility.
23450 @ifset SYSTEM_READLINE
23451 @xref{Using History Interactively, , , history, GNU History Library},
23453 @ifclear SYSTEM_READLINE
23454 @xref{Using History Interactively},
23456 for the detailed description of the History library.
23458 To issue a command to @value{GDBN} without affecting certain aspects of
23459 the state which is seen by users, prefix it with @samp{server }
23460 (@pxref{Server Prefix}). This
23461 means that this command will not affect the command history, nor will it
23462 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23463 pressed on a line by itself.
23465 @cindex @code{server}, command prefix
23466 The server prefix does not affect the recording of values into the value
23467 history; to print a value without recording it into the value history,
23468 use the @code{output} command instead of the @code{print} command.
23470 Here is the description of @value{GDBN} commands related to command
23474 @cindex history substitution
23475 @cindex history file
23476 @kindex set history filename
23477 @cindex @env{GDBHISTFILE}, environment variable
23478 @item set history filename @var{fname}
23479 Set the name of the @value{GDBN} command history file to @var{fname}.
23480 This is the file where @value{GDBN} reads an initial command history
23481 list, and where it writes the command history from this session when it
23482 exits. You can access this list through history expansion or through
23483 the history command editing characters listed below. This file defaults
23484 to the value of the environment variable @code{GDBHISTFILE}, or to
23485 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23488 @cindex save command history
23489 @kindex set history save
23490 @item set history save
23491 @itemx set history save on
23492 Record command history in a file, whose name may be specified with the
23493 @code{set history filename} command. By default, this option is disabled.
23495 @item set history save off
23496 Stop recording command history in a file.
23498 @cindex history size
23499 @kindex set history size
23500 @cindex @env{GDBHISTSIZE}, environment variable
23501 @item set history size @var{size}
23502 @itemx set history size unlimited
23503 Set the number of commands which @value{GDBN} keeps in its history list.
23504 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23505 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23506 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23507 either a negative number or the empty string, then the number of commands
23508 @value{GDBN} keeps in the history list is unlimited.
23510 @cindex remove duplicate history
23511 @kindex set history remove-duplicates
23512 @item set history remove-duplicates @var{count}
23513 @itemx set history remove-duplicates unlimited
23514 Control the removal of duplicate history entries in the command history list.
23515 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23516 history entries and remove the first entry that is a duplicate of the current
23517 entry being added to the command history list. If @var{count} is
23518 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23519 removal of duplicate history entries is disabled.
23521 Only history entries added during the current session are considered for
23522 removal. This option is set to 0 by default.
23526 History expansion assigns special meaning to the character @kbd{!}.
23527 @ifset SYSTEM_READLINE
23528 @xref{Event Designators, , , history, GNU History Library},
23530 @ifclear SYSTEM_READLINE
23531 @xref{Event Designators},
23535 @cindex history expansion, turn on/off
23536 Since @kbd{!} is also the logical not operator in C, history expansion
23537 is off by default. If you decide to enable history expansion with the
23538 @code{set history expansion on} command, you may sometimes need to
23539 follow @kbd{!} (when it is used as logical not, in an expression) with
23540 a space or a tab to prevent it from being expanded. The readline
23541 history facilities do not attempt substitution on the strings
23542 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23544 The commands to control history expansion are:
23547 @item set history expansion on
23548 @itemx set history expansion
23549 @kindex set history expansion
23550 Enable history expansion. History expansion is off by default.
23552 @item set history expansion off
23553 Disable history expansion.
23556 @kindex show history
23558 @itemx show history filename
23559 @itemx show history save
23560 @itemx show history size
23561 @itemx show history expansion
23562 These commands display the state of the @value{GDBN} history parameters.
23563 @code{show history} by itself displays all four states.
23568 @kindex show commands
23569 @cindex show last commands
23570 @cindex display command history
23571 @item show commands
23572 Display the last ten commands in the command history.
23574 @item show commands @var{n}
23575 Print ten commands centered on command number @var{n}.
23577 @item show commands +
23578 Print ten commands just after the commands last printed.
23582 @section Screen Size
23583 @cindex size of screen
23584 @cindex screen size
23587 @cindex pauses in output
23589 Certain commands to @value{GDBN} may produce large amounts of
23590 information output to the screen. To help you read all of it,
23591 @value{GDBN} pauses and asks you for input at the end of each page of
23592 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23593 to discard the remaining output. Also, the screen width setting
23594 determines when to wrap lines of output. Depending on what is being
23595 printed, @value{GDBN} tries to break the line at a readable place,
23596 rather than simply letting it overflow onto the following line.
23598 Normally @value{GDBN} knows the size of the screen from the terminal
23599 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23600 together with the value of the @code{TERM} environment variable and the
23601 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23602 you can override it with the @code{set height} and @code{set
23609 @kindex show height
23610 @item set height @var{lpp}
23611 @itemx set height unlimited
23613 @itemx set width @var{cpl}
23614 @itemx set width unlimited
23616 These @code{set} commands specify a screen height of @var{lpp} lines and
23617 a screen width of @var{cpl} characters. The associated @code{show}
23618 commands display the current settings.
23620 If you specify a height of either @code{unlimited} or zero lines,
23621 @value{GDBN} does not pause during output no matter how long the
23622 output is. This is useful if output is to a file or to an editor
23625 Likewise, you can specify @samp{set width unlimited} or @samp{set
23626 width 0} to prevent @value{GDBN} from wrapping its output.
23628 @item set pagination on
23629 @itemx set pagination off
23630 @kindex set pagination
23631 Turn the output pagination on or off; the default is on. Turning
23632 pagination off is the alternative to @code{set height unlimited}. Note that
23633 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23634 Options, -batch}) also automatically disables pagination.
23636 @item show pagination
23637 @kindex show pagination
23638 Show the current pagination mode.
23643 @cindex number representation
23644 @cindex entering numbers
23646 You can always enter numbers in octal, decimal, or hexadecimal in
23647 @value{GDBN} by the usual conventions: octal numbers begin with
23648 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23649 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23650 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23651 10; likewise, the default display for numbers---when no particular
23652 format is specified---is base 10. You can change the default base for
23653 both input and output with the commands described below.
23656 @kindex set input-radix
23657 @item set input-radix @var{base}
23658 Set the default base for numeric input. Supported choices
23659 for @var{base} are decimal 8, 10, or 16. The base must itself be
23660 specified either unambiguously or using the current input radix; for
23664 set input-radix 012
23665 set input-radix 10.
23666 set input-radix 0xa
23670 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23671 leaves the input radix unchanged, no matter what it was, since
23672 @samp{10}, being without any leading or trailing signs of its base, is
23673 interpreted in the current radix. Thus, if the current radix is 16,
23674 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23677 @kindex set output-radix
23678 @item set output-radix @var{base}
23679 Set the default base for numeric display. Supported choices
23680 for @var{base} are decimal 8, 10, or 16. The base must itself be
23681 specified either unambiguously or using the current input radix.
23683 @kindex show input-radix
23684 @item show input-radix
23685 Display the current default base for numeric input.
23687 @kindex show output-radix
23688 @item show output-radix
23689 Display the current default base for numeric display.
23691 @item set radix @r{[}@var{base}@r{]}
23695 These commands set and show the default base for both input and output
23696 of numbers. @code{set radix} sets the radix of input and output to
23697 the same base; without an argument, it resets the radix back to its
23698 default value of 10.
23703 @section Configuring the Current ABI
23705 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23706 application automatically. However, sometimes you need to override its
23707 conclusions. Use these commands to manage @value{GDBN}'s view of the
23713 @cindex Newlib OS ABI and its influence on the longjmp handling
23715 One @value{GDBN} configuration can debug binaries for multiple operating
23716 system targets, either via remote debugging or native emulation.
23717 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23718 but you can override its conclusion using the @code{set osabi} command.
23719 One example where this is useful is in debugging of binaries which use
23720 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23721 not have the same identifying marks that the standard C library for your
23724 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23725 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23726 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23727 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23731 Show the OS ABI currently in use.
23734 With no argument, show the list of registered available OS ABI's.
23736 @item set osabi @var{abi}
23737 Set the current OS ABI to @var{abi}.
23740 @cindex float promotion
23742 Generally, the way that an argument of type @code{float} is passed to a
23743 function depends on whether the function is prototyped. For a prototyped
23744 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23745 according to the architecture's convention for @code{float}. For unprototyped
23746 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23747 @code{double} and then passed.
23749 Unfortunately, some forms of debug information do not reliably indicate whether
23750 a function is prototyped. If @value{GDBN} calls a function that is not marked
23751 as prototyped, it consults @kbd{set coerce-float-to-double}.
23754 @kindex set coerce-float-to-double
23755 @item set coerce-float-to-double
23756 @itemx set coerce-float-to-double on
23757 Arguments of type @code{float} will be promoted to @code{double} when passed
23758 to an unprototyped function. This is the default setting.
23760 @item set coerce-float-to-double off
23761 Arguments of type @code{float} will be passed directly to unprototyped
23764 @kindex show coerce-float-to-double
23765 @item show coerce-float-to-double
23766 Show the current setting of promoting @code{float} to @code{double}.
23770 @kindex show cp-abi
23771 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23772 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23773 used to build your application. @value{GDBN} only fully supports
23774 programs with a single C@t{++} ABI; if your program contains code using
23775 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23776 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23777 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23778 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23779 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23780 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23785 Show the C@t{++} ABI currently in use.
23788 With no argument, show the list of supported C@t{++} ABI's.
23790 @item set cp-abi @var{abi}
23791 @itemx set cp-abi auto
23792 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23796 @section Automatically loading associated files
23797 @cindex auto-loading
23799 @value{GDBN} sometimes reads files with commands and settings automatically,
23800 without being explicitly told so by the user. We call this feature
23801 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23802 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23803 results or introduce security risks (e.g., if the file comes from untrusted
23807 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23808 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23810 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23811 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23814 There are various kinds of files @value{GDBN} can automatically load.
23815 In addition to these files, @value{GDBN} supports auto-loading code written
23816 in various extension languages. @xref{Auto-loading extensions}.
23818 Note that loading of these associated files (including the local @file{.gdbinit}
23819 file) requires accordingly configured @code{auto-load safe-path}
23820 (@pxref{Auto-loading safe path}).
23822 For these reasons, @value{GDBN} includes commands and options to let you
23823 control when to auto-load files and which files should be auto-loaded.
23826 @anchor{set auto-load off}
23827 @kindex set auto-load off
23828 @item set auto-load off
23829 Globally disable loading of all auto-loaded files.
23830 You may want to use this command with the @samp{-iex} option
23831 (@pxref{Option -init-eval-command}) such as:
23833 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23836 Be aware that system init file (@pxref{System-wide configuration})
23837 and init files from your home directory (@pxref{Home Directory Init File})
23838 still get read (as they come from generally trusted directories).
23839 To prevent @value{GDBN} from auto-loading even those init files, use the
23840 @option{-nx} option (@pxref{Mode Options}), in addition to
23841 @code{set auto-load no}.
23843 @anchor{show auto-load}
23844 @kindex show auto-load
23845 @item show auto-load
23846 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23850 (gdb) show auto-load
23851 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23852 libthread-db: Auto-loading of inferior specific libthread_db is on.
23853 local-gdbinit: Auto-loading of .gdbinit script from current directory
23855 python-scripts: Auto-loading of Python scripts is on.
23856 safe-path: List of directories from which it is safe to auto-load files
23857 is $debugdir:$datadir/auto-load.
23858 scripts-directory: List of directories from which to load auto-loaded scripts
23859 is $debugdir:$datadir/auto-load.
23862 @anchor{info auto-load}
23863 @kindex info auto-load
23864 @item info auto-load
23865 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23869 (gdb) info auto-load
23872 Yes /home/user/gdb/gdb-gdb.gdb
23873 libthread-db: No auto-loaded libthread-db.
23874 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23878 Yes /home/user/gdb/gdb-gdb.py
23882 These are @value{GDBN} control commands for the auto-loading:
23884 @multitable @columnfractions .5 .5
23885 @item @xref{set auto-load off}.
23886 @tab Disable auto-loading globally.
23887 @item @xref{show auto-load}.
23888 @tab Show setting of all kinds of files.
23889 @item @xref{info auto-load}.
23890 @tab Show state of all kinds of files.
23891 @item @xref{set auto-load gdb-scripts}.
23892 @tab Control for @value{GDBN} command scripts.
23893 @item @xref{show auto-load gdb-scripts}.
23894 @tab Show setting of @value{GDBN} command scripts.
23895 @item @xref{info auto-load gdb-scripts}.
23896 @tab Show state of @value{GDBN} command scripts.
23897 @item @xref{set auto-load python-scripts}.
23898 @tab Control for @value{GDBN} Python scripts.
23899 @item @xref{show auto-load python-scripts}.
23900 @tab Show setting of @value{GDBN} Python scripts.
23901 @item @xref{info auto-load python-scripts}.
23902 @tab Show state of @value{GDBN} Python scripts.
23903 @item @xref{set auto-load guile-scripts}.
23904 @tab Control for @value{GDBN} Guile scripts.
23905 @item @xref{show auto-load guile-scripts}.
23906 @tab Show setting of @value{GDBN} Guile scripts.
23907 @item @xref{info auto-load guile-scripts}.
23908 @tab Show state of @value{GDBN} Guile scripts.
23909 @item @xref{set auto-load scripts-directory}.
23910 @tab Control for @value{GDBN} auto-loaded scripts location.
23911 @item @xref{show auto-load scripts-directory}.
23912 @tab Show @value{GDBN} auto-loaded scripts location.
23913 @item @xref{add-auto-load-scripts-directory}.
23914 @tab Add directory for auto-loaded scripts location list.
23915 @item @xref{set auto-load local-gdbinit}.
23916 @tab Control for init file in the current directory.
23917 @item @xref{show auto-load local-gdbinit}.
23918 @tab Show setting of init file in the current directory.
23919 @item @xref{info auto-load local-gdbinit}.
23920 @tab Show state of init file in the current directory.
23921 @item @xref{set auto-load libthread-db}.
23922 @tab Control for thread debugging library.
23923 @item @xref{show auto-load libthread-db}.
23924 @tab Show setting of thread debugging library.
23925 @item @xref{info auto-load libthread-db}.
23926 @tab Show state of thread debugging library.
23927 @item @xref{set auto-load safe-path}.
23928 @tab Control directories trusted for automatic loading.
23929 @item @xref{show auto-load safe-path}.
23930 @tab Show directories trusted for automatic loading.
23931 @item @xref{add-auto-load-safe-path}.
23932 @tab Add directory trusted for automatic loading.
23935 @node Init File in the Current Directory
23936 @subsection Automatically loading init file in the current directory
23937 @cindex auto-loading init file in the current directory
23939 By default, @value{GDBN} reads and executes the canned sequences of commands
23940 from init file (if any) in the current working directory,
23941 see @ref{Init File in the Current Directory during Startup}.
23943 Note that loading of this local @file{.gdbinit} file also requires accordingly
23944 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23947 @anchor{set auto-load local-gdbinit}
23948 @kindex set auto-load local-gdbinit
23949 @item set auto-load local-gdbinit [on|off]
23950 Enable or disable the auto-loading of canned sequences of commands
23951 (@pxref{Sequences}) found in init file in the current directory.
23953 @anchor{show auto-load local-gdbinit}
23954 @kindex show auto-load local-gdbinit
23955 @item show auto-load local-gdbinit
23956 Show whether auto-loading of canned sequences of commands from init file in the
23957 current directory is enabled or disabled.
23959 @anchor{info auto-load local-gdbinit}
23960 @kindex info auto-load local-gdbinit
23961 @item info auto-load local-gdbinit
23962 Print whether canned sequences of commands from init file in the
23963 current directory have been auto-loaded.
23966 @node libthread_db.so.1 file
23967 @subsection Automatically loading thread debugging library
23968 @cindex auto-loading libthread_db.so.1
23970 This feature is currently present only on @sc{gnu}/Linux native hosts.
23972 @value{GDBN} reads in some cases thread debugging library from places specific
23973 to the inferior (@pxref{set libthread-db-search-path}).
23975 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23976 without checking this @samp{set auto-load libthread-db} switch as system
23977 libraries have to be trusted in general. In all other cases of
23978 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23979 auto-load libthread-db} is enabled before trying to open such thread debugging
23982 Note that loading of this debugging library also requires accordingly configured
23983 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23986 @anchor{set auto-load libthread-db}
23987 @kindex set auto-load libthread-db
23988 @item set auto-load libthread-db [on|off]
23989 Enable or disable the auto-loading of inferior specific thread debugging library.
23991 @anchor{show auto-load libthread-db}
23992 @kindex show auto-load libthread-db
23993 @item show auto-load libthread-db
23994 Show whether auto-loading of inferior specific thread debugging library is
23995 enabled or disabled.
23997 @anchor{info auto-load libthread-db}
23998 @kindex info auto-load libthread-db
23999 @item info auto-load libthread-db
24000 Print the list of all loaded inferior specific thread debugging libraries and
24001 for each such library print list of inferior @var{pid}s using it.
24004 @node Auto-loading safe path
24005 @subsection Security restriction for auto-loading
24006 @cindex auto-loading safe-path
24008 As the files of inferior can come from untrusted source (such as submitted by
24009 an application user) @value{GDBN} does not always load any files automatically.
24010 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24011 directories trusted for loading files not explicitly requested by user.
24012 Each directory can also be a shell wildcard pattern.
24014 If the path is not set properly you will see a warning and the file will not
24019 Reading symbols from /home/user/gdb/gdb...done.
24020 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24021 declined by your `auto-load safe-path' set
24022 to "$debugdir:$datadir/auto-load".
24023 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24024 declined by your `auto-load safe-path' set
24025 to "$debugdir:$datadir/auto-load".
24029 To instruct @value{GDBN} to go ahead and use the init files anyway,
24030 invoke @value{GDBN} like this:
24033 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24036 The list of trusted directories is controlled by the following commands:
24039 @anchor{set auto-load safe-path}
24040 @kindex set auto-load safe-path
24041 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24042 Set the list of directories (and their subdirectories) trusted for automatic
24043 loading and execution of scripts. You can also enter a specific trusted file.
24044 Each directory can also be a shell wildcard pattern; wildcards do not match
24045 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24046 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24047 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24048 its default value as specified during @value{GDBN} compilation.
24050 The list of directories uses path separator (@samp{:} on GNU and Unix
24051 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24052 to the @env{PATH} environment variable.
24054 @anchor{show auto-load safe-path}
24055 @kindex show auto-load safe-path
24056 @item show auto-load safe-path
24057 Show the list of directories trusted for automatic loading and execution of
24060 @anchor{add-auto-load-safe-path}
24061 @kindex add-auto-load-safe-path
24062 @item add-auto-load-safe-path
24063 Add an entry (or list of entries) to the list of directories trusted for
24064 automatic loading and execution of scripts. Multiple entries may be delimited
24065 by the host platform path separator in use.
24068 This variable defaults to what @code{--with-auto-load-dir} has been configured
24069 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24070 substitution applies the same as for @ref{set auto-load scripts-directory}.
24071 The default @code{set auto-load safe-path} value can be also overriden by
24072 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24074 Setting this variable to @file{/} disables this security protection,
24075 corresponding @value{GDBN} configuration option is
24076 @option{--without-auto-load-safe-path}.
24077 This variable is supposed to be set to the system directories writable by the
24078 system superuser only. Users can add their source directories in init files in
24079 their home directories (@pxref{Home Directory Init File}). See also deprecated
24080 init file in the current directory
24081 (@pxref{Init File in the Current Directory during Startup}).
24083 To force @value{GDBN} to load the files it declined to load in the previous
24084 example, you could use one of the following ways:
24087 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24088 Specify this trusted directory (or a file) as additional component of the list.
24089 You have to specify also any existing directories displayed by
24090 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24092 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24093 Specify this directory as in the previous case but just for a single
24094 @value{GDBN} session.
24096 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24097 Disable auto-loading safety for a single @value{GDBN} session.
24098 This assumes all the files you debug during this @value{GDBN} session will come
24099 from trusted sources.
24101 @item @kbd{./configure --without-auto-load-safe-path}
24102 During compilation of @value{GDBN} you may disable any auto-loading safety.
24103 This assumes all the files you will ever debug with this @value{GDBN} come from
24107 On the other hand you can also explicitly forbid automatic files loading which
24108 also suppresses any such warning messages:
24111 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24112 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24114 @item @file{~/.gdbinit}: @samp{set auto-load no}
24115 Disable auto-loading globally for the user
24116 (@pxref{Home Directory Init File}). While it is improbable, you could also
24117 use system init file instead (@pxref{System-wide configuration}).
24120 This setting applies to the file names as entered by user. If no entry matches
24121 @value{GDBN} tries as a last resort to also resolve all the file names into
24122 their canonical form (typically resolving symbolic links) and compare the
24123 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24124 own before starting the comparison so a canonical form of directories is
24125 recommended to be entered.
24127 @node Auto-loading verbose mode
24128 @subsection Displaying files tried for auto-load
24129 @cindex auto-loading verbose mode
24131 For better visibility of all the file locations where you can place scripts to
24132 be auto-loaded with inferior --- or to protect yourself against accidental
24133 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24134 all the files attempted to be loaded. Both existing and non-existing files may
24137 For example the list of directories from which it is safe to auto-load files
24138 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24139 may not be too obvious while setting it up.
24142 (gdb) set debug auto-load on
24143 (gdb) file ~/src/t/true
24144 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24145 for objfile "/tmp/true".
24146 auto-load: Updating directories of "/usr:/opt".
24147 auto-load: Using directory "/usr".
24148 auto-load: Using directory "/opt".
24149 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24150 by your `auto-load safe-path' set to "/usr:/opt".
24154 @anchor{set debug auto-load}
24155 @kindex set debug auto-load
24156 @item set debug auto-load [on|off]
24157 Set whether to print the filenames attempted to be auto-loaded.
24159 @anchor{show debug auto-load}
24160 @kindex show debug auto-load
24161 @item show debug auto-load
24162 Show whether printing of the filenames attempted to be auto-loaded is turned
24166 @node Messages/Warnings
24167 @section Optional Warnings and Messages
24169 @cindex verbose operation
24170 @cindex optional warnings
24171 By default, @value{GDBN} is silent about its inner workings. If you are
24172 running on a slow machine, you may want to use the @code{set verbose}
24173 command. This makes @value{GDBN} tell you when it does a lengthy
24174 internal operation, so you will not think it has crashed.
24176 Currently, the messages controlled by @code{set verbose} are those
24177 which announce that the symbol table for a source file is being read;
24178 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24181 @kindex set verbose
24182 @item set verbose on
24183 Enables @value{GDBN} output of certain informational messages.
24185 @item set verbose off
24186 Disables @value{GDBN} output of certain informational messages.
24188 @kindex show verbose
24190 Displays whether @code{set verbose} is on or off.
24193 By default, if @value{GDBN} encounters bugs in the symbol table of an
24194 object file, it is silent; but if you are debugging a compiler, you may
24195 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24200 @kindex set complaints
24201 @item set complaints @var{limit}
24202 Permits @value{GDBN} to output @var{limit} complaints about each type of
24203 unusual symbols before becoming silent about the problem. Set
24204 @var{limit} to zero to suppress all complaints; set it to a large number
24205 to prevent complaints from being suppressed.
24207 @kindex show complaints
24208 @item show complaints
24209 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24213 @anchor{confirmation requests}
24214 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24215 lot of stupid questions to confirm certain commands. For example, if
24216 you try to run a program which is already running:
24220 The program being debugged has been started already.
24221 Start it from the beginning? (y or n)
24224 If you are willing to unflinchingly face the consequences of your own
24225 commands, you can disable this ``feature'':
24229 @kindex set confirm
24231 @cindex confirmation
24232 @cindex stupid questions
24233 @item set confirm off
24234 Disables confirmation requests. Note that running @value{GDBN} with
24235 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24236 automatically disables confirmation requests.
24238 @item set confirm on
24239 Enables confirmation requests (the default).
24241 @kindex show confirm
24243 Displays state of confirmation requests.
24247 @cindex command tracing
24248 If you need to debug user-defined commands or sourced files you may find it
24249 useful to enable @dfn{command tracing}. In this mode each command will be
24250 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24251 quantity denoting the call depth of each command.
24254 @kindex set trace-commands
24255 @cindex command scripts, debugging
24256 @item set trace-commands on
24257 Enable command tracing.
24258 @item set trace-commands off
24259 Disable command tracing.
24260 @item show trace-commands
24261 Display the current state of command tracing.
24264 @node Debugging Output
24265 @section Optional Messages about Internal Happenings
24266 @cindex optional debugging messages
24268 @value{GDBN} has commands that enable optional debugging messages from
24269 various @value{GDBN} subsystems; normally these commands are of
24270 interest to @value{GDBN} maintainers, or when reporting a bug. This
24271 section documents those commands.
24274 @kindex set exec-done-display
24275 @item set exec-done-display
24276 Turns on or off the notification of asynchronous commands'
24277 completion. When on, @value{GDBN} will print a message when an
24278 asynchronous command finishes its execution. The default is off.
24279 @kindex show exec-done-display
24280 @item show exec-done-display
24281 Displays the current setting of asynchronous command completion
24284 @cindex ARM AArch64
24285 @item set debug aarch64
24286 Turns on or off display of debugging messages related to ARM AArch64.
24287 The default is off.
24289 @item show debug aarch64
24290 Displays the current state of displaying debugging messages related to
24292 @cindex gdbarch debugging info
24293 @cindex architecture debugging info
24294 @item set debug arch
24295 Turns on or off display of gdbarch debugging info. The default is off
24296 @item show debug arch
24297 Displays the current state of displaying gdbarch debugging info.
24298 @item set debug aix-solib
24299 @cindex AIX shared library debugging
24300 Control display of debugging messages from the AIX shared library
24301 support module. The default is off.
24302 @item show debug aix-thread
24303 Show the current state of displaying AIX shared library debugging messages.
24304 @item set debug aix-thread
24305 @cindex AIX threads
24306 Display debugging messages about inner workings of the AIX thread
24308 @item show debug aix-thread
24309 Show the current state of AIX thread debugging info display.
24310 @item set debug check-physname
24312 Check the results of the ``physname'' computation. When reading DWARF
24313 debugging information for C@t{++}, @value{GDBN} attempts to compute
24314 each entity's name. @value{GDBN} can do this computation in two
24315 different ways, depending on exactly what information is present.
24316 When enabled, this setting causes @value{GDBN} to compute the names
24317 both ways and display any discrepancies.
24318 @item show debug check-physname
24319 Show the current state of ``physname'' checking.
24320 @item set debug coff-pe-read
24321 @cindex COFF/PE exported symbols
24322 Control display of debugging messages related to reading of COFF/PE
24323 exported symbols. The default is off.
24324 @item show debug coff-pe-read
24325 Displays the current state of displaying debugging messages related to
24326 reading of COFF/PE exported symbols.
24327 @item set debug dwarf-die
24329 Dump DWARF DIEs after they are read in.
24330 The value is the number of nesting levels to print.
24331 A value of zero turns off the display.
24332 @item show debug dwarf-die
24333 Show the current state of DWARF DIE debugging.
24334 @item set debug dwarf-line
24335 @cindex DWARF Line Tables
24336 Turns on or off display of debugging messages related to reading
24337 DWARF line tables. The default is 0 (off).
24338 A value of 1 provides basic information.
24339 A value greater than 1 provides more verbose information.
24340 @item show debug dwarf-line
24341 Show the current state of DWARF line table debugging.
24342 @item set debug dwarf-read
24343 @cindex DWARF Reading
24344 Turns on or off display of debugging messages related to reading
24345 DWARF debug info. The default is 0 (off).
24346 A value of 1 provides basic information.
24347 A value greater than 1 provides more verbose information.
24348 @item show debug dwarf-read
24349 Show the current state of DWARF reader debugging.
24350 @item set debug displaced
24351 @cindex displaced stepping debugging info
24352 Turns on or off display of @value{GDBN} debugging info for the
24353 displaced stepping support. The default is off.
24354 @item show debug displaced
24355 Displays the current state of displaying @value{GDBN} debugging info
24356 related to displaced stepping.
24357 @item set debug event
24358 @cindex event debugging info
24359 Turns on or off display of @value{GDBN} event debugging info. The
24361 @item show debug event
24362 Displays the current state of displaying @value{GDBN} event debugging
24364 @item set debug expression
24365 @cindex expression debugging info
24366 Turns on or off display of debugging info about @value{GDBN}
24367 expression parsing. The default is off.
24368 @item show debug expression
24369 Displays the current state of displaying debugging info about
24370 @value{GDBN} expression parsing.
24371 @item set debug fbsd-lwp
24372 @cindex FreeBSD LWP debug messages
24373 Turns on or off debugging messages from the FreeBSD LWP debug support.
24374 @item show debug fbsd-lwp
24375 Show the current state of FreeBSD LWP debugging messages.
24376 @item set debug frame
24377 @cindex frame debugging info
24378 Turns on or off display of @value{GDBN} frame debugging info. The
24380 @item show debug frame
24381 Displays the current state of displaying @value{GDBN} frame debugging
24383 @item set debug gnu-nat
24384 @cindex @sc{gnu}/Hurd debug messages
24385 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24386 @item show debug gnu-nat
24387 Show the current state of @sc{gnu}/Hurd debugging messages.
24388 @item set debug infrun
24389 @cindex inferior debugging info
24390 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24391 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24392 for implementing operations such as single-stepping the inferior.
24393 @item show debug infrun
24394 Displays the current state of @value{GDBN} inferior debugging.
24395 @item set debug jit
24396 @cindex just-in-time compilation, debugging messages
24397 Turn on or off debugging messages from JIT debug support.
24398 @item show debug jit
24399 Displays the current state of @value{GDBN} JIT debugging.
24400 @item set debug lin-lwp
24401 @cindex @sc{gnu}/Linux LWP debug messages
24402 @cindex Linux lightweight processes
24403 Turn on or off debugging messages from the Linux LWP debug support.
24404 @item show debug lin-lwp
24405 Show the current state of Linux LWP debugging messages.
24406 @item set debug linux-namespaces
24407 @cindex @sc{gnu}/Linux namespaces debug messages
24408 Turn on or off debugging messages from the Linux namespaces debug support.
24409 @item show debug linux-namespaces
24410 Show the current state of Linux namespaces debugging messages.
24411 @item set debug mach-o
24412 @cindex Mach-O symbols processing
24413 Control display of debugging messages related to Mach-O symbols
24414 processing. The default is off.
24415 @item show debug mach-o
24416 Displays the current state of displaying debugging messages related to
24417 reading of COFF/PE exported symbols.
24418 @item set debug notification
24419 @cindex remote async notification debugging info
24420 Turn on or off debugging messages about remote async notification.
24421 The default is off.
24422 @item show debug notification
24423 Displays the current state of remote async notification debugging messages.
24424 @item set debug observer
24425 @cindex observer debugging info
24426 Turns on or off display of @value{GDBN} observer debugging. This
24427 includes info such as the notification of observable events.
24428 @item show debug observer
24429 Displays the current state of observer debugging.
24430 @item set debug overload
24431 @cindex C@t{++} overload debugging info
24432 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24433 info. This includes info such as ranking of functions, etc. The default
24435 @item show debug overload
24436 Displays the current state of displaying @value{GDBN} C@t{++} overload
24438 @cindex expression parser, debugging info
24439 @cindex debug expression parser
24440 @item set debug parser
24441 Turns on or off the display of expression parser debugging output.
24442 Internally, this sets the @code{yydebug} variable in the expression
24443 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24444 details. The default is off.
24445 @item show debug parser
24446 Show the current state of expression parser debugging.
24447 @cindex packets, reporting on stdout
24448 @cindex serial connections, debugging
24449 @cindex debug remote protocol
24450 @cindex remote protocol debugging
24451 @cindex display remote packets
24452 @item set debug remote
24453 Turns on or off display of reports on all packets sent back and forth across
24454 the serial line to the remote machine. The info is printed on the
24455 @value{GDBN} standard output stream. The default is off.
24456 @item show debug remote
24457 Displays the state of display of remote packets.
24459 @item set debug separate-debug-file
24460 Turns on or off display of debug output about separate debug file search.
24461 @item show debug separate-debug-file
24462 Displays the state of separate debug file search debug output.
24464 @item set debug serial
24465 Turns on or off display of @value{GDBN} serial debugging info. The
24467 @item show debug serial
24468 Displays the current state of displaying @value{GDBN} serial debugging
24470 @item set debug solib-frv
24471 @cindex FR-V shared-library debugging
24472 Turn on or off debugging messages for FR-V shared-library code.
24473 @item show debug solib-frv
24474 Display the current state of FR-V shared-library code debugging
24476 @item set debug symbol-lookup
24477 @cindex symbol lookup
24478 Turns on or off display of debugging messages related to symbol lookup.
24479 The default is 0 (off).
24480 A value of 1 provides basic information.
24481 A value greater than 1 provides more verbose information.
24482 @item show debug symbol-lookup
24483 Show the current state of symbol lookup debugging messages.
24484 @item set debug symfile
24485 @cindex symbol file functions
24486 Turns on or off display of debugging messages related to symbol file functions.
24487 The default is off. @xref{Files}.
24488 @item show debug symfile
24489 Show the current state of symbol file debugging messages.
24490 @item set debug symtab-create
24491 @cindex symbol table creation
24492 Turns on or off display of debugging messages related to symbol table creation.
24493 The default is 0 (off).
24494 A value of 1 provides basic information.
24495 A value greater than 1 provides more verbose information.
24496 @item show debug symtab-create
24497 Show the current state of symbol table creation debugging.
24498 @item set debug target
24499 @cindex target debugging info
24500 Turns on or off display of @value{GDBN} target debugging info. This info
24501 includes what is going on at the target level of GDB, as it happens. The
24502 default is 0. Set it to 1 to track events, and to 2 to also track the
24503 value of large memory transfers.
24504 @item show debug target
24505 Displays the current state of displaying @value{GDBN} target debugging
24507 @item set debug timestamp
24508 @cindex timestampping debugging info
24509 Turns on or off display of timestamps with @value{GDBN} debugging info.
24510 When enabled, seconds and microseconds are displayed before each debugging
24512 @item show debug timestamp
24513 Displays the current state of displaying timestamps with @value{GDBN}
24515 @item set debug varobj
24516 @cindex variable object debugging info
24517 Turns on or off display of @value{GDBN} variable object debugging
24518 info. The default is off.
24519 @item show debug varobj
24520 Displays the current state of displaying @value{GDBN} variable object
24522 @item set debug xml
24523 @cindex XML parser debugging
24524 Turn on or off debugging messages for built-in XML parsers.
24525 @item show debug xml
24526 Displays the current state of XML debugging messages.
24529 @node Other Misc Settings
24530 @section Other Miscellaneous Settings
24531 @cindex miscellaneous settings
24534 @kindex set interactive-mode
24535 @item set interactive-mode
24536 If @code{on}, forces @value{GDBN} to assume that GDB was started
24537 in a terminal. In practice, this means that @value{GDBN} should wait
24538 for the user to answer queries generated by commands entered at
24539 the command prompt. If @code{off}, forces @value{GDBN} to operate
24540 in the opposite mode, and it uses the default answers to all queries.
24541 If @code{auto} (the default), @value{GDBN} tries to determine whether
24542 its standard input is a terminal, and works in interactive-mode if it
24543 is, non-interactively otherwise.
24545 In the vast majority of cases, the debugger should be able to guess
24546 correctly which mode should be used. But this setting can be useful
24547 in certain specific cases, such as running a MinGW @value{GDBN}
24548 inside a cygwin window.
24550 @kindex show interactive-mode
24551 @item show interactive-mode
24552 Displays whether the debugger is operating in interactive mode or not.
24555 @node Extending GDB
24556 @chapter Extending @value{GDBN}
24557 @cindex extending GDB
24559 @value{GDBN} provides several mechanisms for extension.
24560 @value{GDBN} also provides the ability to automatically load
24561 extensions when it reads a file for debugging. This allows the
24562 user to automatically customize @value{GDBN} for the program
24566 * Sequences:: Canned Sequences of @value{GDBN} Commands
24567 * Python:: Extending @value{GDBN} using Python
24568 * Guile:: Extending @value{GDBN} using Guile
24569 * Auto-loading extensions:: Automatically loading extensions
24570 * Multiple Extension Languages:: Working with multiple extension languages
24571 * Aliases:: Creating new spellings of existing commands
24574 To facilitate the use of extension languages, @value{GDBN} is capable
24575 of evaluating the contents of a file. When doing so, @value{GDBN}
24576 can recognize which extension language is being used by looking at
24577 the filename extension. Files with an unrecognized filename extension
24578 are always treated as a @value{GDBN} Command Files.
24579 @xref{Command Files,, Command files}.
24581 You can control how @value{GDBN} evaluates these files with the following
24585 @kindex set script-extension
24586 @kindex show script-extension
24587 @item set script-extension off
24588 All scripts are always evaluated as @value{GDBN} Command Files.
24590 @item set script-extension soft
24591 The debugger determines the scripting language based on filename
24592 extension. If this scripting language is supported, @value{GDBN}
24593 evaluates the script using that language. Otherwise, it evaluates
24594 the file as a @value{GDBN} Command File.
24596 @item set script-extension strict
24597 The debugger determines the scripting language based on filename
24598 extension, and evaluates the script using that language. If the
24599 language is not supported, then the evaluation fails.
24601 @item show script-extension
24602 Display the current value of the @code{script-extension} option.
24607 @section Canned Sequences of Commands
24609 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24610 Command Lists}), @value{GDBN} provides two ways to store sequences of
24611 commands for execution as a unit: user-defined commands and command
24615 * Define:: How to define your own commands
24616 * Hooks:: Hooks for user-defined commands
24617 * Command Files:: How to write scripts of commands to be stored in a file
24618 * Output:: Commands for controlled output
24619 * Auto-loading sequences:: Controlling auto-loaded command files
24623 @subsection User-defined Commands
24625 @cindex user-defined command
24626 @cindex arguments, to user-defined commands
24627 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24628 which you assign a new name as a command. This is done with the
24629 @code{define} command. User commands may accept an unlimited number of arguments
24630 separated by whitespace. Arguments are accessed within the user command
24631 via @code{$arg0@dots{}$argN}. A trivial example:
24635 print $arg0 + $arg1 + $arg2
24640 To execute the command use:
24647 This defines the command @code{adder}, which prints the sum of
24648 its three arguments. Note the arguments are text substitutions, so they may
24649 reference variables, use complex expressions, or even perform inferior
24652 @cindex argument count in user-defined commands
24653 @cindex how many arguments (user-defined commands)
24654 In addition, @code{$argc} may be used to find out how many arguments have
24660 print $arg0 + $arg1
24663 print $arg0 + $arg1 + $arg2
24668 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24669 to process a variable number of arguments:
24676 eval "set $sum = $sum + $arg%d", $i
24686 @item define @var{commandname}
24687 Define a command named @var{commandname}. If there is already a command
24688 by that name, you are asked to confirm that you want to redefine it.
24689 The argument @var{commandname} may be a bare command name consisting of letters,
24690 numbers, dashes, and underscores. It may also start with any predefined
24691 prefix command. For example, @samp{define target my-target} creates
24692 a user-defined @samp{target my-target} command.
24694 The definition of the command is made up of other @value{GDBN} command lines,
24695 which are given following the @code{define} command. The end of these
24696 commands is marked by a line containing @code{end}.
24699 @kindex end@r{ (user-defined commands)}
24700 @item document @var{commandname}
24701 Document the user-defined command @var{commandname}, so that it can be
24702 accessed by @code{help}. The command @var{commandname} must already be
24703 defined. This command reads lines of documentation just as @code{define}
24704 reads the lines of the command definition, ending with @code{end}.
24705 After the @code{document} command is finished, @code{help} on command
24706 @var{commandname} displays the documentation you have written.
24708 You may use the @code{document} command again to change the
24709 documentation of a command. Redefining the command with @code{define}
24710 does not change the documentation.
24712 @kindex dont-repeat
24713 @cindex don't repeat command
24715 Used inside a user-defined command, this tells @value{GDBN} that this
24716 command should not be repeated when the user hits @key{RET}
24717 (@pxref{Command Syntax, repeat last command}).
24719 @kindex help user-defined
24720 @item help user-defined
24721 List all user-defined commands and all python commands defined in class
24722 COMAND_USER. The first line of the documentation or docstring is
24727 @itemx show user @var{commandname}
24728 Display the @value{GDBN} commands used to define @var{commandname} (but
24729 not its documentation). If no @var{commandname} is given, display the
24730 definitions for all user-defined commands.
24731 This does not work for user-defined python commands.
24733 @cindex infinite recursion in user-defined commands
24734 @kindex show max-user-call-depth
24735 @kindex set max-user-call-depth
24736 @item show max-user-call-depth
24737 @itemx set max-user-call-depth
24738 The value of @code{max-user-call-depth} controls how many recursion
24739 levels are allowed in user-defined commands before @value{GDBN} suspects an
24740 infinite recursion and aborts the command.
24741 This does not apply to user-defined python commands.
24744 In addition to the above commands, user-defined commands frequently
24745 use control flow commands, described in @ref{Command Files}.
24747 When user-defined commands are executed, the
24748 commands of the definition are not printed. An error in any command
24749 stops execution of the user-defined command.
24751 If used interactively, commands that would ask for confirmation proceed
24752 without asking when used inside a user-defined command. Many @value{GDBN}
24753 commands that normally print messages to say what they are doing omit the
24754 messages when used in a user-defined command.
24757 @subsection User-defined Command Hooks
24758 @cindex command hooks
24759 @cindex hooks, for commands
24760 @cindex hooks, pre-command
24763 You may define @dfn{hooks}, which are a special kind of user-defined
24764 command. Whenever you run the command @samp{foo}, if the user-defined
24765 command @samp{hook-foo} exists, it is executed (with no arguments)
24766 before that command.
24768 @cindex hooks, post-command
24770 A hook may also be defined which is run after the command you executed.
24771 Whenever you run the command @samp{foo}, if the user-defined command
24772 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24773 that command. Post-execution hooks may exist simultaneously with
24774 pre-execution hooks, for the same command.
24776 It is valid for a hook to call the command which it hooks. If this
24777 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24779 @c It would be nice if hookpost could be passed a parameter indicating
24780 @c if the command it hooks executed properly or not. FIXME!
24782 @kindex stop@r{, a pseudo-command}
24783 In addition, a pseudo-command, @samp{stop} exists. Defining
24784 (@samp{hook-stop}) makes the associated commands execute every time
24785 execution stops in your program: before breakpoint commands are run,
24786 displays are printed, or the stack frame is printed.
24788 For example, to ignore @code{SIGALRM} signals while
24789 single-stepping, but treat them normally during normal execution,
24794 handle SIGALRM nopass
24798 handle SIGALRM pass
24801 define hook-continue
24802 handle SIGALRM pass
24806 As a further example, to hook at the beginning and end of the @code{echo}
24807 command, and to add extra text to the beginning and end of the message,
24815 define hookpost-echo
24819 (@value{GDBP}) echo Hello World
24820 <<<---Hello World--->>>
24825 You can define a hook for any single-word command in @value{GDBN}, but
24826 not for command aliases; you should define a hook for the basic command
24827 name, e.g.@: @code{backtrace} rather than @code{bt}.
24828 @c FIXME! So how does Joe User discover whether a command is an alias
24830 You can hook a multi-word command by adding @code{hook-} or
24831 @code{hookpost-} to the last word of the command, e.g.@:
24832 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24834 If an error occurs during the execution of your hook, execution of
24835 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24836 (before the command that you actually typed had a chance to run).
24838 If you try to define a hook which does not match any known command, you
24839 get a warning from the @code{define} command.
24841 @node Command Files
24842 @subsection Command Files
24844 @cindex command files
24845 @cindex scripting commands
24846 A command file for @value{GDBN} is a text file made of lines that are
24847 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24848 also be included. An empty line in a command file does nothing; it
24849 does not mean to repeat the last command, as it would from the
24852 You can request the execution of a command file with the @code{source}
24853 command. Note that the @code{source} command is also used to evaluate
24854 scripts that are not Command Files. The exact behavior can be configured
24855 using the @code{script-extension} setting.
24856 @xref{Extending GDB,, Extending GDB}.
24860 @cindex execute commands from a file
24861 @item source [-s] [-v] @var{filename}
24862 Execute the command file @var{filename}.
24865 The lines in a command file are generally executed sequentially,
24866 unless the order of execution is changed by one of the
24867 @emph{flow-control commands} described below. The commands are not
24868 printed as they are executed. An error in any command terminates
24869 execution of the command file and control is returned to the console.
24871 @value{GDBN} first searches for @var{filename} in the current directory.
24872 If the file is not found there, and @var{filename} does not specify a
24873 directory, then @value{GDBN} also looks for the file on the source search path
24874 (specified with the @samp{directory} command);
24875 except that @file{$cdir} is not searched because the compilation directory
24876 is not relevant to scripts.
24878 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24879 on the search path even if @var{filename} specifies a directory.
24880 The search is done by appending @var{filename} to each element of the
24881 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24882 and the search path contains @file{/home/user} then @value{GDBN} will
24883 look for the script @file{/home/user/mylib/myscript}.
24884 The search is also done if @var{filename} is an absolute path.
24885 For example, if @var{filename} is @file{/tmp/myscript} and
24886 the search path contains @file{/home/user} then @value{GDBN} will
24887 look for the script @file{/home/user/tmp/myscript}.
24888 For DOS-like systems, if @var{filename} contains a drive specification,
24889 it is stripped before concatenation. For example, if @var{filename} is
24890 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24891 will look for the script @file{c:/tmp/myscript}.
24893 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24894 each command as it is executed. The option must be given before
24895 @var{filename}, and is interpreted as part of the filename anywhere else.
24897 Commands that would ask for confirmation if used interactively proceed
24898 without asking when used in a command file. Many @value{GDBN} commands that
24899 normally print messages to say what they are doing omit the messages
24900 when called from command files.
24902 @value{GDBN} also accepts command input from standard input. In this
24903 mode, normal output goes to standard output and error output goes to
24904 standard error. Errors in a command file supplied on standard input do
24905 not terminate execution of the command file---execution continues with
24909 gdb < cmds > log 2>&1
24912 (The syntax above will vary depending on the shell used.) This example
24913 will execute commands from the file @file{cmds}. All output and errors
24914 would be directed to @file{log}.
24916 Since commands stored on command files tend to be more general than
24917 commands typed interactively, they frequently need to deal with
24918 complicated situations, such as different or unexpected values of
24919 variables and symbols, changes in how the program being debugged is
24920 built, etc. @value{GDBN} provides a set of flow-control commands to
24921 deal with these complexities. Using these commands, you can write
24922 complex scripts that loop over data structures, execute commands
24923 conditionally, etc.
24930 This command allows to include in your script conditionally executed
24931 commands. The @code{if} command takes a single argument, which is an
24932 expression to evaluate. It is followed by a series of commands that
24933 are executed only if the expression is true (its value is nonzero).
24934 There can then optionally be an @code{else} line, followed by a series
24935 of commands that are only executed if the expression was false. The
24936 end of the list is marked by a line containing @code{end}.
24940 This command allows to write loops. Its syntax is similar to
24941 @code{if}: the command takes a single argument, which is an expression
24942 to evaluate, and must be followed by the commands to execute, one per
24943 line, terminated by an @code{end}. These commands are called the
24944 @dfn{body} of the loop. The commands in the body of @code{while} are
24945 executed repeatedly as long as the expression evaluates to true.
24949 This command exits the @code{while} loop in whose body it is included.
24950 Execution of the script continues after that @code{while}s @code{end}
24953 @kindex loop_continue
24954 @item loop_continue
24955 This command skips the execution of the rest of the body of commands
24956 in the @code{while} loop in whose body it is included. Execution
24957 branches to the beginning of the @code{while} loop, where it evaluates
24958 the controlling expression.
24960 @kindex end@r{ (if/else/while commands)}
24962 Terminate the block of commands that are the body of @code{if},
24963 @code{else}, or @code{while} flow-control commands.
24968 @subsection Commands for Controlled Output
24970 During the execution of a command file or a user-defined command, normal
24971 @value{GDBN} output is suppressed; the only output that appears is what is
24972 explicitly printed by the commands in the definition. This section
24973 describes three commands useful for generating exactly the output you
24978 @item echo @var{text}
24979 @c I do not consider backslash-space a standard C escape sequence
24980 @c because it is not in ANSI.
24981 Print @var{text}. Nonprinting characters can be included in
24982 @var{text} using C escape sequences, such as @samp{\n} to print a
24983 newline. @strong{No newline is printed unless you specify one.}
24984 In addition to the standard C escape sequences, a backslash followed
24985 by a space stands for a space. This is useful for displaying a
24986 string with spaces at the beginning or the end, since leading and
24987 trailing spaces are otherwise trimmed from all arguments.
24988 To print @samp{@w{ }and foo =@w{ }}, use the command
24989 @samp{echo \@w{ }and foo = \@w{ }}.
24991 A backslash at the end of @var{text} can be used, as in C, to continue
24992 the command onto subsequent lines. For example,
24995 echo This is some text\n\
24996 which is continued\n\
24997 onto several lines.\n
25000 produces the same output as
25003 echo This is some text\n
25004 echo which is continued\n
25005 echo onto several lines.\n
25009 @item output @var{expression}
25010 Print the value of @var{expression} and nothing but that value: no
25011 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25012 value history either. @xref{Expressions, ,Expressions}, for more information
25015 @item output/@var{fmt} @var{expression}
25016 Print the value of @var{expression} in format @var{fmt}. You can use
25017 the same formats as for @code{print}. @xref{Output Formats,,Output
25018 Formats}, for more information.
25021 @item printf @var{template}, @var{expressions}@dots{}
25022 Print the values of one or more @var{expressions} under the control of
25023 the string @var{template}. To print several values, make
25024 @var{expressions} be a comma-separated list of individual expressions,
25025 which may be either numbers or pointers. Their values are printed as
25026 specified by @var{template}, exactly as a C program would do by
25027 executing the code below:
25030 printf (@var{template}, @var{expressions}@dots{});
25033 As in @code{C} @code{printf}, ordinary characters in @var{template}
25034 are printed verbatim, while @dfn{conversion specification} introduced
25035 by the @samp{%} character cause subsequent @var{expressions} to be
25036 evaluated, their values converted and formatted according to type and
25037 style information encoded in the conversion specifications, and then
25040 For example, you can print two values in hex like this:
25043 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25046 @code{printf} supports all the standard @code{C} conversion
25047 specifications, including the flags and modifiers between the @samp{%}
25048 character and the conversion letter, with the following exceptions:
25052 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25055 The modifier @samp{*} is not supported for specifying precision or
25059 The @samp{'} flag (for separation of digits into groups according to
25060 @code{LC_NUMERIC'}) is not supported.
25063 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25067 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25070 The conversion letters @samp{a} and @samp{A} are not supported.
25074 Note that the @samp{ll} type modifier is supported only if the
25075 underlying @code{C} implementation used to build @value{GDBN} supports
25076 the @code{long long int} type, and the @samp{L} type modifier is
25077 supported only if @code{long double} type is available.
25079 As in @code{C}, @code{printf} supports simple backslash-escape
25080 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25081 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25082 single character. Octal and hexadecimal escape sequences are not
25085 Additionally, @code{printf} supports conversion specifications for DFP
25086 (@dfn{Decimal Floating Point}) types using the following length modifiers
25087 together with a floating point specifier.
25092 @samp{H} for printing @code{Decimal32} types.
25095 @samp{D} for printing @code{Decimal64} types.
25098 @samp{DD} for printing @code{Decimal128} types.
25101 If the underlying @code{C} implementation used to build @value{GDBN} has
25102 support for the three length modifiers for DFP types, other modifiers
25103 such as width and precision will also be available for @value{GDBN} to use.
25105 In case there is no such @code{C} support, no additional modifiers will be
25106 available and the value will be printed in the standard way.
25108 Here's an example of printing DFP types using the above conversion letters:
25110 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25115 @item eval @var{template}, @var{expressions}@dots{}
25116 Convert the values of one or more @var{expressions} under the control of
25117 the string @var{template} to a command line, and call it.
25121 @node Auto-loading sequences
25122 @subsection Controlling auto-loading native @value{GDBN} scripts
25123 @cindex native script auto-loading
25125 When a new object file is read (for example, due to the @code{file}
25126 command, or because the inferior has loaded a shared library),
25127 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25128 @xref{Auto-loading extensions}.
25130 Auto-loading can be enabled or disabled,
25131 and the list of auto-loaded scripts can be printed.
25134 @anchor{set auto-load gdb-scripts}
25135 @kindex set auto-load gdb-scripts
25136 @item set auto-load gdb-scripts [on|off]
25137 Enable or disable the auto-loading of canned sequences of commands scripts.
25139 @anchor{show auto-load gdb-scripts}
25140 @kindex show auto-load gdb-scripts
25141 @item show auto-load gdb-scripts
25142 Show whether auto-loading of canned sequences of commands scripts is enabled or
25145 @anchor{info auto-load gdb-scripts}
25146 @kindex info auto-load gdb-scripts
25147 @cindex print list of auto-loaded canned sequences of commands scripts
25148 @item info auto-load gdb-scripts [@var{regexp}]
25149 Print the list of all canned sequences of commands scripts that @value{GDBN}
25153 If @var{regexp} is supplied only canned sequences of commands scripts with
25154 matching names are printed.
25156 @c Python docs live in a separate file.
25157 @include python.texi
25159 @c Guile docs live in a separate file.
25160 @include guile.texi
25162 @node Auto-loading extensions
25163 @section Auto-loading extensions
25164 @cindex auto-loading extensions
25166 @value{GDBN} provides two mechanisms for automatically loading extensions
25167 when a new object file is read (for example, due to the @code{file}
25168 command, or because the inferior has loaded a shared library):
25169 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25170 section of modern file formats like ELF.
25173 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25174 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25175 * Which flavor to choose?::
25178 The auto-loading feature is useful for supplying application-specific
25179 debugging commands and features.
25181 Auto-loading can be enabled or disabled,
25182 and the list of auto-loaded scripts can be printed.
25183 See the @samp{auto-loading} section of each extension language
25184 for more information.
25185 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25186 For Python files see @ref{Python Auto-loading}.
25188 Note that loading of this script file also requires accordingly configured
25189 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25191 @node objfile-gdbdotext file
25192 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25193 @cindex @file{@var{objfile}-gdb.gdb}
25194 @cindex @file{@var{objfile}-gdb.py}
25195 @cindex @file{@var{objfile}-gdb.scm}
25197 When a new object file is read, @value{GDBN} looks for a file named
25198 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25199 where @var{objfile} is the object file's name and
25200 where @var{ext} is the file extension for the extension language:
25203 @item @file{@var{objfile}-gdb.gdb}
25204 GDB's own command language
25205 @item @file{@var{objfile}-gdb.py}
25207 @item @file{@var{objfile}-gdb.scm}
25211 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25212 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25213 components, and appending the @file{-gdb.@var{ext}} suffix.
25214 If this file exists and is readable, @value{GDBN} will evaluate it as a
25215 script in the specified extension language.
25217 If this file does not exist, then @value{GDBN} will look for
25218 @var{script-name} file in all of the directories as specified below.
25220 Note that loading of these files requires an accordingly configured
25221 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25223 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25224 scripts normally according to its @file{.exe} filename. But if no scripts are
25225 found @value{GDBN} also tries script filenames matching the object file without
25226 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25227 is attempted on any platform. This makes the script filenames compatible
25228 between Unix and MS-Windows hosts.
25231 @anchor{set auto-load scripts-directory}
25232 @kindex set auto-load scripts-directory
25233 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25234 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25235 may be delimited by the host platform path separator in use
25236 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25238 Each entry here needs to be covered also by the security setting
25239 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25241 @anchor{with-auto-load-dir}
25242 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25243 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25244 configuration option @option{--with-auto-load-dir}.
25246 Any reference to @file{$debugdir} will get replaced by
25247 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25248 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25249 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25250 @file{$datadir} must be placed as a directory component --- either alone or
25251 delimited by @file{/} or @file{\} directory separators, depending on the host
25254 The list of directories uses path separator (@samp{:} on GNU and Unix
25255 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25256 to the @env{PATH} environment variable.
25258 @anchor{show auto-load scripts-directory}
25259 @kindex show auto-load scripts-directory
25260 @item show auto-load scripts-directory
25261 Show @value{GDBN} auto-loaded scripts location.
25263 @anchor{add-auto-load-scripts-directory}
25264 @kindex add-auto-load-scripts-directory
25265 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25266 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25267 Multiple entries may be delimited by the host platform path separator in use.
25270 @value{GDBN} does not track which files it has already auto-loaded this way.
25271 @value{GDBN} will load the associated script every time the corresponding
25272 @var{objfile} is opened.
25273 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25274 is evaluated more than once.
25276 @node dotdebug_gdb_scripts section
25277 @subsection The @code{.debug_gdb_scripts} section
25278 @cindex @code{.debug_gdb_scripts} section
25280 For systems using file formats like ELF and COFF,
25281 when @value{GDBN} loads a new object file
25282 it will look for a special section named @code{.debug_gdb_scripts}.
25283 If this section exists, its contents is a list of null-terminated entries
25284 specifying scripts to load. Each entry begins with a non-null prefix byte that
25285 specifies the kind of entry, typically the extension language and whether the
25286 script is in a file or inlined in @code{.debug_gdb_scripts}.
25288 The following entries are supported:
25291 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25292 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25293 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25294 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25297 @subsubsection Script File Entries
25299 If the entry specifies a file, @value{GDBN} will look for the file first
25300 in the current directory and then along the source search path
25301 (@pxref{Source Path, ,Specifying Source Directories}),
25302 except that @file{$cdir} is not searched, since the compilation
25303 directory is not relevant to scripts.
25305 File entries can be placed in section @code{.debug_gdb_scripts} with,
25306 for example, this GCC macro for Python scripts.
25309 /* Note: The "MS" section flags are to remove duplicates. */
25310 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25312 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25313 .byte 1 /* Python */\n\
25314 .asciz \"" script_name "\"\n\
25320 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25321 Then one can reference the macro in a header or source file like this:
25324 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25327 The script name may include directories if desired.
25329 Note that loading of this script file also requires accordingly configured
25330 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25332 If the macro invocation is put in a header, any application or library
25333 using this header will get a reference to the specified script,
25334 and with the use of @code{"MS"} attributes on the section, the linker
25335 will remove duplicates.
25337 @subsubsection Script Text Entries
25339 Script text entries allow to put the executable script in the entry
25340 itself instead of loading it from a file.
25341 The first line of the entry, everything after the prefix byte and up to
25342 the first newline (@code{0xa}) character, is the script name, and must not
25343 contain any kind of space character, e.g., spaces or tabs.
25344 The rest of the entry, up to the trailing null byte, is the script to
25345 execute in the specified language. The name needs to be unique among
25346 all script names, as @value{GDBN} executes each script only once based
25349 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25353 #include "symcat.h"
25354 #include "gdb/section-scripts.h"
25356 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25357 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25358 ".ascii \"gdb.inlined-script\\n\"\n"
25359 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25360 ".ascii \" def __init__ (self):\\n\"\n"
25361 ".ascii \" super (test_cmd, self).__init__ ("
25362 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25363 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25364 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25365 ".ascii \"test_cmd ()\\n\"\n"
25371 Loading of inlined scripts requires a properly configured
25372 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25373 The path to specify in @code{auto-load safe-path} is the path of the file
25374 containing the @code{.debug_gdb_scripts} section.
25376 @node Which flavor to choose?
25377 @subsection Which flavor to choose?
25379 Given the multiple ways of auto-loading extensions, it might not always
25380 be clear which one to choose. This section provides some guidance.
25383 Benefits of the @file{-gdb.@var{ext}} way:
25387 Can be used with file formats that don't support multiple sections.
25390 Ease of finding scripts for public libraries.
25392 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25393 in the source search path.
25394 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25395 isn't a source directory in which to find the script.
25398 Doesn't require source code additions.
25402 Benefits of the @code{.debug_gdb_scripts} way:
25406 Works with static linking.
25408 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25409 trigger their loading. When an application is statically linked the only
25410 objfile available is the executable, and it is cumbersome to attach all the
25411 scripts from all the input libraries to the executable's
25412 @file{-gdb.@var{ext}} script.
25415 Works with classes that are entirely inlined.
25417 Some classes can be entirely inlined, and thus there may not be an associated
25418 shared library to attach a @file{-gdb.@var{ext}} script to.
25421 Scripts needn't be copied out of the source tree.
25423 In some circumstances, apps can be built out of large collections of internal
25424 libraries, and the build infrastructure necessary to install the
25425 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25426 cumbersome. It may be easier to specify the scripts in the
25427 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25428 top of the source tree to the source search path.
25431 @node Multiple Extension Languages
25432 @section Multiple Extension Languages
25434 The Guile and Python extension languages do not share any state,
25435 and generally do not interfere with each other.
25436 There are some things to be aware of, however.
25438 @subsection Python comes first
25440 Python was @value{GDBN}'s first extension language, and to avoid breaking
25441 existing behaviour Python comes first. This is generally solved by the
25442 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25443 extension languages, and when it makes a call to an extension language,
25444 (say to pretty-print a value), it tries each in turn until an extension
25445 language indicates it has performed the request (e.g., has returned the
25446 pretty-printed form of a value).
25447 This extends to errors while performing such requests: If an error happens
25448 while, for example, trying to pretty-print an object then the error is
25449 reported and any following extension languages are not tried.
25452 @section Creating new spellings of existing commands
25453 @cindex aliases for commands
25455 It is often useful to define alternate spellings of existing commands.
25456 For example, if a new @value{GDBN} command defined in Python has
25457 a long name to type, it is handy to have an abbreviated version of it
25458 that involves less typing.
25460 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25461 of the @samp{step} command even though it is otherwise an ambiguous
25462 abbreviation of other commands like @samp{set} and @samp{show}.
25464 Aliases are also used to provide shortened or more common versions
25465 of multi-word commands. For example, @value{GDBN} provides the
25466 @samp{tty} alias of the @samp{set inferior-tty} command.
25468 You can define a new alias with the @samp{alias} command.
25473 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25477 @var{ALIAS} specifies the name of the new alias.
25478 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25481 @var{COMMAND} specifies the name of an existing command
25482 that is being aliased.
25484 The @samp{-a} option specifies that the new alias is an abbreviation
25485 of the command. Abbreviations are not shown in command
25486 lists displayed by the @samp{help} command.
25488 The @samp{--} option specifies the end of options,
25489 and is useful when @var{ALIAS} begins with a dash.
25491 Here is a simple example showing how to make an abbreviation
25492 of a command so that there is less to type.
25493 Suppose you were tired of typing @samp{disas}, the current
25494 shortest unambiguous abbreviation of the @samp{disassemble} command
25495 and you wanted an even shorter version named @samp{di}.
25496 The following will accomplish this.
25499 (gdb) alias -a di = disas
25502 Note that aliases are different from user-defined commands.
25503 With a user-defined command, you also need to write documentation
25504 for it with the @samp{document} command.
25505 An alias automatically picks up the documentation of the existing command.
25507 Here is an example where we make @samp{elms} an abbreviation of
25508 @samp{elements} in the @samp{set print elements} command.
25509 This is to show that you can make an abbreviation of any part
25513 (gdb) alias -a set print elms = set print elements
25514 (gdb) alias -a show print elms = show print elements
25515 (gdb) set p elms 20
25517 Limit on string chars or array elements to print is 200.
25520 Note that if you are defining an alias of a @samp{set} command,
25521 and you want to have an alias for the corresponding @samp{show}
25522 command, then you need to define the latter separately.
25524 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25525 @var{ALIAS}, just as they are normally.
25528 (gdb) alias -a set pr elms = set p ele
25531 Finally, here is an example showing the creation of a one word
25532 alias for a more complex command.
25533 This creates alias @samp{spe} of the command @samp{set print elements}.
25536 (gdb) alias spe = set print elements
25541 @chapter Command Interpreters
25542 @cindex command interpreters
25544 @value{GDBN} supports multiple command interpreters, and some command
25545 infrastructure to allow users or user interface writers to switch
25546 between interpreters or run commands in other interpreters.
25548 @value{GDBN} currently supports two command interpreters, the console
25549 interpreter (sometimes called the command-line interpreter or @sc{cli})
25550 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25551 describes both of these interfaces in great detail.
25553 By default, @value{GDBN} will start with the console interpreter.
25554 However, the user may choose to start @value{GDBN} with another
25555 interpreter by specifying the @option{-i} or @option{--interpreter}
25556 startup options. Defined interpreters include:
25560 @cindex console interpreter
25561 The traditional console or command-line interpreter. This is the most often
25562 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25563 @value{GDBN} will use this interpreter.
25566 @cindex mi interpreter
25567 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25568 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25569 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25573 @cindex mi2 interpreter
25574 The current @sc{gdb/mi} interface.
25577 @cindex mi1 interpreter
25578 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25582 @cindex invoke another interpreter
25584 @kindex interpreter-exec
25585 You may execute commands in any interpreter from the current
25586 interpreter using the appropriate command. If you are running the
25587 console interpreter, simply use the @code{interpreter-exec} command:
25590 interpreter-exec mi "-data-list-register-names"
25593 @sc{gdb/mi} has a similar command, although it is only available in versions of
25594 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25596 Note that @code{interpreter-exec} only changes the interpreter for the
25597 duration of the specified command. It does not change the interpreter
25600 @cindex start a new independent interpreter
25602 Although you may only choose a single interpreter at startup, it is
25603 possible to run an independent interpreter on a specified input/output
25604 device (usually a tty).
25606 For example, consider a debugger GUI or IDE that wants to provide a
25607 @value{GDBN} console view. It may do so by embedding a terminal
25608 emulator widget in its GUI, starting @value{GDBN} in the traditional
25609 command-line mode with stdin/stdout/stderr redirected to that
25610 terminal, and then creating an MI interpreter running on a specified
25611 input/output device. The console interpreter created by @value{GDBN}
25612 at startup handles commands the user types in the terminal widget,
25613 while the GUI controls and synchronizes state with @value{GDBN} using
25614 the separate MI interpreter.
25616 To start a new secondary @dfn{user interface} running MI, use the
25617 @code{new-ui} command:
25620 @cindex new user interface
25622 new-ui @var{interpreter} @var{tty}
25625 The @var{interpreter} parameter specifies the interpreter to run.
25626 This accepts the same values as the @code{interpreter-exec} command.
25627 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25628 @var{tty} parameter specifies the name of the bidirectional file the
25629 interpreter uses for input/output, usually the name of a
25630 pseudoterminal slave on Unix systems. For example:
25633 (@value{GDBP}) new-ui mi /dev/pts/9
25637 runs an MI interpreter on @file{/dev/pts/9}.
25640 @chapter @value{GDBN} Text User Interface
25642 @cindex Text User Interface
25645 * TUI Overview:: TUI overview
25646 * TUI Keys:: TUI key bindings
25647 * TUI Single Key Mode:: TUI single key mode
25648 * TUI Commands:: TUI-specific commands
25649 * TUI Configuration:: TUI configuration variables
25652 The @value{GDBN} Text User Interface (TUI) is a terminal
25653 interface which uses the @code{curses} library to show the source
25654 file, the assembly output, the program registers and @value{GDBN}
25655 commands in separate text windows. The TUI mode is supported only
25656 on platforms where a suitable version of the @code{curses} library
25659 The TUI mode is enabled by default when you invoke @value{GDBN} as
25660 @samp{@value{GDBP} -tui}.
25661 You can also switch in and out of TUI mode while @value{GDBN} runs by
25662 using various TUI commands and key bindings, such as @command{tui
25663 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25664 @ref{TUI Keys, ,TUI Key Bindings}.
25667 @section TUI Overview
25669 In TUI mode, @value{GDBN} can display several text windows:
25673 This window is the @value{GDBN} command window with the @value{GDBN}
25674 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25675 managed using readline.
25678 The source window shows the source file of the program. The current
25679 line and active breakpoints are displayed in this window.
25682 The assembly window shows the disassembly output of the program.
25685 This window shows the processor registers. Registers are highlighted
25686 when their values change.
25689 The source and assembly windows show the current program position
25690 by highlighting the current line and marking it with a @samp{>} marker.
25691 Breakpoints are indicated with two markers. The first marker
25692 indicates the breakpoint type:
25696 Breakpoint which was hit at least once.
25699 Breakpoint which was never hit.
25702 Hardware breakpoint which was hit at least once.
25705 Hardware breakpoint which was never hit.
25708 The second marker indicates whether the breakpoint is enabled or not:
25712 Breakpoint is enabled.
25715 Breakpoint is disabled.
25718 The source, assembly and register windows are updated when the current
25719 thread changes, when the frame changes, or when the program counter
25722 These windows are not all visible at the same time. The command
25723 window is always visible. The others can be arranged in several
25734 source and assembly,
25737 source and registers, or
25740 assembly and registers.
25743 A status line above the command window shows the following information:
25747 Indicates the current @value{GDBN} target.
25748 (@pxref{Targets, ,Specifying a Debugging Target}).
25751 Gives the current process or thread number.
25752 When no process is being debugged, this field is set to @code{No process}.
25755 Gives the current function name for the selected frame.
25756 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25757 When there is no symbol corresponding to the current program counter,
25758 the string @code{??} is displayed.
25761 Indicates the current line number for the selected frame.
25762 When the current line number is not known, the string @code{??} is displayed.
25765 Indicates the current program counter address.
25769 @section TUI Key Bindings
25770 @cindex TUI key bindings
25772 The TUI installs several key bindings in the readline keymaps
25773 @ifset SYSTEM_READLINE
25774 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25776 @ifclear SYSTEM_READLINE
25777 (@pxref{Command Line Editing}).
25779 The following key bindings are installed for both TUI mode and the
25780 @value{GDBN} standard mode.
25789 Enter or leave the TUI mode. When leaving the TUI mode,
25790 the curses window management stops and @value{GDBN} operates using
25791 its standard mode, writing on the terminal directly. When reentering
25792 the TUI mode, control is given back to the curses windows.
25793 The screen is then refreshed.
25797 Use a TUI layout with only one window. The layout will
25798 either be @samp{source} or @samp{assembly}. When the TUI mode
25799 is not active, it will switch to the TUI mode.
25801 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25805 Use a TUI layout with at least two windows. When the current
25806 layout already has two windows, the next layout with two windows is used.
25807 When a new layout is chosen, one window will always be common to the
25808 previous layout and the new one.
25810 Think of it as the Emacs @kbd{C-x 2} binding.
25814 Change the active window. The TUI associates several key bindings
25815 (like scrolling and arrow keys) with the active window. This command
25816 gives the focus to the next TUI window.
25818 Think of it as the Emacs @kbd{C-x o} binding.
25822 Switch in and out of the TUI SingleKey mode that binds single
25823 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25826 The following key bindings only work in the TUI mode:
25831 Scroll the active window one page up.
25835 Scroll the active window one page down.
25839 Scroll the active window one line up.
25843 Scroll the active window one line down.
25847 Scroll the active window one column left.
25851 Scroll the active window one column right.
25855 Refresh the screen.
25858 Because the arrow keys scroll the active window in the TUI mode, they
25859 are not available for their normal use by readline unless the command
25860 window has the focus. When another window is active, you must use
25861 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25862 and @kbd{C-f} to control the command window.
25864 @node TUI Single Key Mode
25865 @section TUI Single Key Mode
25866 @cindex TUI single key mode
25868 The TUI also provides a @dfn{SingleKey} mode, which binds several
25869 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25870 switch into this mode, where the following key bindings are used:
25873 @kindex c @r{(SingleKey TUI key)}
25877 @kindex d @r{(SingleKey TUI key)}
25881 @kindex f @r{(SingleKey TUI key)}
25885 @kindex n @r{(SingleKey TUI key)}
25889 @kindex o @r{(SingleKey TUI key)}
25891 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25893 @kindex q @r{(SingleKey TUI key)}
25895 exit the SingleKey mode.
25897 @kindex r @r{(SingleKey TUI key)}
25901 @kindex s @r{(SingleKey TUI key)}
25905 @kindex i @r{(SingleKey TUI key)}
25907 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25909 @kindex u @r{(SingleKey TUI key)}
25913 @kindex v @r{(SingleKey TUI key)}
25917 @kindex w @r{(SingleKey TUI key)}
25922 Other keys temporarily switch to the @value{GDBN} command prompt.
25923 The key that was pressed is inserted in the editing buffer so that
25924 it is possible to type most @value{GDBN} commands without interaction
25925 with the TUI SingleKey mode. Once the command is entered the TUI
25926 SingleKey mode is restored. The only way to permanently leave
25927 this mode is by typing @kbd{q} or @kbd{C-x s}.
25931 @section TUI-specific Commands
25932 @cindex TUI commands
25934 The TUI has specific commands to control the text windows.
25935 These commands are always available, even when @value{GDBN} is not in
25936 the TUI mode. When @value{GDBN} is in the standard mode, most
25937 of these commands will automatically switch to the TUI mode.
25939 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25940 terminal, or @value{GDBN} has been started with the machine interface
25941 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25942 these commands will fail with an error, because it would not be
25943 possible or desirable to enable curses window management.
25948 Activate TUI mode. The last active TUI window layout will be used if
25949 TUI mode has prevsiouly been used in the current debugging session,
25950 otherwise a default layout is used.
25953 @kindex tui disable
25954 Disable TUI mode, returning to the console interpreter.
25958 List and give the size of all displayed windows.
25960 @item layout @var{name}
25962 Changes which TUI windows are displayed. In each layout the command
25963 window is always displayed, the @var{name} parameter controls which
25964 additional windows are displayed, and can be any of the following:
25968 Display the next layout.
25971 Display the previous layout.
25974 Display the source and command windows.
25977 Display the assembly and command windows.
25980 Display the source, assembly, and command windows.
25983 When in @code{src} layout display the register, source, and command
25984 windows. When in @code{asm} or @code{split} layout display the
25985 register, assembler, and command windows.
25988 @item focus @var{name}
25990 Changes which TUI window is currently active for scrolling. The
25991 @var{name} parameter can be any of the following:
25995 Make the next window active for scrolling.
25998 Make the previous window active for scrolling.
26001 Make the source window active for scrolling.
26004 Make the assembly window active for scrolling.
26007 Make the register window active for scrolling.
26010 Make the command window active for scrolling.
26015 Refresh the screen. This is similar to typing @kbd{C-L}.
26017 @item tui reg @var{group}
26019 Changes the register group displayed in the tui register window to
26020 @var{group}. If the register window is not currently displayed this
26021 command will cause the register window to be displayed. The list of
26022 register groups, as well as their order is target specific. The
26023 following groups are available on most targets:
26026 Repeatedly selecting this group will cause the display to cycle
26027 through all of the available register groups.
26030 Repeatedly selecting this group will cause the display to cycle
26031 through all of the available register groups in the reverse order to
26035 Display the general registers.
26037 Display the floating point registers.
26039 Display the system registers.
26041 Display the vector registers.
26043 Display all registers.
26048 Update the source window and the current execution point.
26050 @item winheight @var{name} +@var{count}
26051 @itemx winheight @var{name} -@var{count}
26053 Change the height of the window @var{name} by @var{count}
26054 lines. Positive counts increase the height, while negative counts
26055 decrease it. The @var{name} parameter can be one of @code{src} (the
26056 source window), @code{cmd} (the command window), @code{asm} (the
26057 disassembly window), or @code{regs} (the register display window).
26059 @item tabset @var{nchars}
26061 Set the width of tab stops to be @var{nchars} characters. This
26062 setting affects the display of TAB characters in the source and
26066 @node TUI Configuration
26067 @section TUI Configuration Variables
26068 @cindex TUI configuration variables
26070 Several configuration variables control the appearance of TUI windows.
26073 @item set tui border-kind @var{kind}
26074 @kindex set tui border-kind
26075 Select the border appearance for the source, assembly and register windows.
26076 The possible values are the following:
26079 Use a space character to draw the border.
26082 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26085 Use the Alternate Character Set to draw the border. The border is
26086 drawn using character line graphics if the terminal supports them.
26089 @item set tui border-mode @var{mode}
26090 @kindex set tui border-mode
26091 @itemx set tui active-border-mode @var{mode}
26092 @kindex set tui active-border-mode
26093 Select the display attributes for the borders of the inactive windows
26094 or the active window. The @var{mode} can be one of the following:
26097 Use normal attributes to display the border.
26103 Use reverse video mode.
26106 Use half bright mode.
26108 @item half-standout
26109 Use half bright and standout mode.
26112 Use extra bright or bold mode.
26114 @item bold-standout
26115 Use extra bright or bold and standout mode.
26120 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26123 @cindex @sc{gnu} Emacs
26124 A special interface allows you to use @sc{gnu} Emacs to view (and
26125 edit) the source files for the program you are debugging with
26128 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26129 executable file you want to debug as an argument. This command starts
26130 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26131 created Emacs buffer.
26132 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26134 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26139 All ``terminal'' input and output goes through an Emacs buffer, called
26142 This applies both to @value{GDBN} commands and their output, and to the input
26143 and output done by the program you are debugging.
26145 This is useful because it means that you can copy the text of previous
26146 commands and input them again; you can even use parts of the output
26149 All the facilities of Emacs' Shell mode are available for interacting
26150 with your program. In particular, you can send signals the usual
26151 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26155 @value{GDBN} displays source code through Emacs.
26157 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26158 source file for that frame and puts an arrow (@samp{=>}) at the
26159 left margin of the current line. Emacs uses a separate buffer for
26160 source display, and splits the screen to show both your @value{GDBN} session
26163 Explicit @value{GDBN} @code{list} or search commands still produce output as
26164 usual, but you probably have no reason to use them from Emacs.
26167 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26168 a graphical mode, enabled by default, which provides further buffers
26169 that can control the execution and describe the state of your program.
26170 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26172 If you specify an absolute file name when prompted for the @kbd{M-x
26173 gdb} argument, then Emacs sets your current working directory to where
26174 your program resides. If you only specify the file name, then Emacs
26175 sets your current working directory to the directory associated
26176 with the previous buffer. In this case, @value{GDBN} may find your
26177 program by searching your environment's @code{PATH} variable, but on
26178 some operating systems it might not find the source. So, although the
26179 @value{GDBN} input and output session proceeds normally, the auxiliary
26180 buffer does not display the current source and line of execution.
26182 The initial working directory of @value{GDBN} is printed on the top
26183 line of the GUD buffer and this serves as a default for the commands
26184 that specify files for @value{GDBN} to operate on. @xref{Files,
26185 ,Commands to Specify Files}.
26187 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26188 need to call @value{GDBN} by a different name (for example, if you
26189 keep several configurations around, with different names) you can
26190 customize the Emacs variable @code{gud-gdb-command-name} to run the
26193 In the GUD buffer, you can use these special Emacs commands in
26194 addition to the standard Shell mode commands:
26198 Describe the features of Emacs' GUD Mode.
26201 Execute to another source line, like the @value{GDBN} @code{step} command; also
26202 update the display window to show the current file and location.
26205 Execute to next source line in this function, skipping all function
26206 calls, like the @value{GDBN} @code{next} command. Then update the display window
26207 to show the current file and location.
26210 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26211 display window accordingly.
26214 Execute until exit from the selected stack frame, like the @value{GDBN}
26215 @code{finish} command.
26218 Continue execution of your program, like the @value{GDBN} @code{continue}
26222 Go up the number of frames indicated by the numeric argument
26223 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26224 like the @value{GDBN} @code{up} command.
26227 Go down the number of frames indicated by the numeric argument, like the
26228 @value{GDBN} @code{down} command.
26231 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26232 tells @value{GDBN} to set a breakpoint on the source line point is on.
26234 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26235 separate frame which shows a backtrace when the GUD buffer is current.
26236 Move point to any frame in the stack and type @key{RET} to make it
26237 become the current frame and display the associated source in the
26238 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26239 selected frame become the current one. In graphical mode, the
26240 speedbar displays watch expressions.
26242 If you accidentally delete the source-display buffer, an easy way to get
26243 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26244 request a frame display; when you run under Emacs, this recreates
26245 the source buffer if necessary to show you the context of the current
26248 The source files displayed in Emacs are in ordinary Emacs buffers
26249 which are visiting the source files in the usual way. You can edit
26250 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26251 communicates with Emacs in terms of line numbers. If you add or
26252 delete lines from the text, the line numbers that @value{GDBN} knows cease
26253 to correspond properly with the code.
26255 A more detailed description of Emacs' interaction with @value{GDBN} is
26256 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26260 @chapter The @sc{gdb/mi} Interface
26262 @unnumberedsec Function and Purpose
26264 @cindex @sc{gdb/mi}, its purpose
26265 @sc{gdb/mi} is a line based machine oriented text interface to
26266 @value{GDBN} and is activated by specifying using the
26267 @option{--interpreter} command line option (@pxref{Mode Options}). It
26268 is specifically intended to support the development of systems which
26269 use the debugger as just one small component of a larger system.
26271 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26272 in the form of a reference manual.
26274 Note that @sc{gdb/mi} is still under construction, so some of the
26275 features described below are incomplete and subject to change
26276 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26278 @unnumberedsec Notation and Terminology
26280 @cindex notational conventions, for @sc{gdb/mi}
26281 This chapter uses the following notation:
26285 @code{|} separates two alternatives.
26288 @code{[ @var{something} ]} indicates that @var{something} is optional:
26289 it may or may not be given.
26292 @code{( @var{group} )*} means that @var{group} inside the parentheses
26293 may repeat zero or more times.
26296 @code{( @var{group} )+} means that @var{group} inside the parentheses
26297 may repeat one or more times.
26300 @code{"@var{string}"} means a literal @var{string}.
26304 @heading Dependencies
26308 * GDB/MI General Design::
26309 * GDB/MI Command Syntax::
26310 * GDB/MI Compatibility with CLI::
26311 * GDB/MI Development and Front Ends::
26312 * GDB/MI Output Records::
26313 * GDB/MI Simple Examples::
26314 * GDB/MI Command Description Format::
26315 * GDB/MI Breakpoint Commands::
26316 * GDB/MI Catchpoint Commands::
26317 * GDB/MI Program Context::
26318 * GDB/MI Thread Commands::
26319 * GDB/MI Ada Tasking Commands::
26320 * GDB/MI Program Execution::
26321 * GDB/MI Stack Manipulation::
26322 * GDB/MI Variable Objects::
26323 * GDB/MI Data Manipulation::
26324 * GDB/MI Tracepoint Commands::
26325 * GDB/MI Symbol Query::
26326 * GDB/MI File Commands::
26328 * GDB/MI Kod Commands::
26329 * GDB/MI Memory Overlay Commands::
26330 * GDB/MI Signal Handling Commands::
26332 * GDB/MI Target Manipulation::
26333 * GDB/MI File Transfer Commands::
26334 * GDB/MI Ada Exceptions Commands::
26335 * GDB/MI Support Commands::
26336 * GDB/MI Miscellaneous Commands::
26339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26340 @node GDB/MI General Design
26341 @section @sc{gdb/mi} General Design
26342 @cindex GDB/MI General Design
26344 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26345 parts---commands sent to @value{GDBN}, responses to those commands
26346 and notifications. Each command results in exactly one response,
26347 indicating either successful completion of the command, or an error.
26348 For the commands that do not resume the target, the response contains the
26349 requested information. For the commands that resume the target, the
26350 response only indicates whether the target was successfully resumed.
26351 Notifications is the mechanism for reporting changes in the state of the
26352 target, or in @value{GDBN} state, that cannot conveniently be associated with
26353 a command and reported as part of that command response.
26355 The important examples of notifications are:
26359 Exec notifications. These are used to report changes in
26360 target state---when a target is resumed, or stopped. It would not
26361 be feasible to include this information in response of resuming
26362 commands, because one resume commands can result in multiple events in
26363 different threads. Also, quite some time may pass before any event
26364 happens in the target, while a frontend needs to know whether the resuming
26365 command itself was successfully executed.
26368 Console output, and status notifications. Console output
26369 notifications are used to report output of CLI commands, as well as
26370 diagnostics for other commands. Status notifications are used to
26371 report the progress of a long-running operation. Naturally, including
26372 this information in command response would mean no output is produced
26373 until the command is finished, which is undesirable.
26376 General notifications. Commands may have various side effects on
26377 the @value{GDBN} or target state beyond their official purpose. For example,
26378 a command may change the selected thread. Although such changes can
26379 be included in command response, using notification allows for more
26380 orthogonal frontend design.
26384 There's no guarantee that whenever an MI command reports an error,
26385 @value{GDBN} or the target are in any specific state, and especially,
26386 the state is not reverted to the state before the MI command was
26387 processed. Therefore, whenever an MI command results in an error,
26388 we recommend that the frontend refreshes all the information shown in
26389 the user interface.
26393 * Context management::
26394 * Asynchronous and non-stop modes::
26398 @node Context management
26399 @subsection Context management
26401 @subsubsection Threads and Frames
26403 In most cases when @value{GDBN} accesses the target, this access is
26404 done in context of a specific thread and frame (@pxref{Frames}).
26405 Often, even when accessing global data, the target requires that a thread
26406 be specified. The CLI interface maintains the selected thread and frame,
26407 and supplies them to target on each command. This is convenient,
26408 because a command line user would not want to specify that information
26409 explicitly on each command, and because user interacts with
26410 @value{GDBN} via a single terminal, so no confusion is possible as
26411 to what thread and frame are the current ones.
26413 In the case of MI, the concept of selected thread and frame is less
26414 useful. First, a frontend can easily remember this information
26415 itself. Second, a graphical frontend can have more than one window,
26416 each one used for debugging a different thread, and the frontend might
26417 want to access additional threads for internal purposes. This
26418 increases the risk that by relying on implicitly selected thread, the
26419 frontend may be operating on a wrong one. Therefore, each MI command
26420 should explicitly specify which thread and frame to operate on. To
26421 make it possible, each MI command accepts the @samp{--thread} and
26422 @samp{--frame} options, the value to each is @value{GDBN} global
26423 identifier for thread and frame to operate on.
26425 Usually, each top-level window in a frontend allows the user to select
26426 a thread and a frame, and remembers the user selection for further
26427 operations. However, in some cases @value{GDBN} may suggest that the
26428 current thread or frame be changed. For example, when stopping on a
26429 breakpoint it is reasonable to switch to the thread where breakpoint is
26430 hit. For another example, if the user issues the CLI @samp{thread} or
26431 @samp{frame} commands via the frontend, it is desirable to change the
26432 frontend's selection to the one specified by user. @value{GDBN}
26433 communicates the suggestion to change current thread and frame using the
26434 @samp{=thread-selected} notification.
26436 Note that historically, MI shares the selected thread with CLI, so
26437 frontends used the @code{-thread-select} to execute commands in the
26438 right context. However, getting this to work right is cumbersome. The
26439 simplest way is for frontend to emit @code{-thread-select} command
26440 before every command. This doubles the number of commands that need
26441 to be sent. The alternative approach is to suppress @code{-thread-select}
26442 if the selected thread in @value{GDBN} is supposed to be identical to the
26443 thread the frontend wants to operate on. However, getting this
26444 optimization right can be tricky. In particular, if the frontend
26445 sends several commands to @value{GDBN}, and one of the commands changes the
26446 selected thread, then the behaviour of subsequent commands will
26447 change. So, a frontend should either wait for response from such
26448 problematic commands, or explicitly add @code{-thread-select} for
26449 all subsequent commands. No frontend is known to do this exactly
26450 right, so it is suggested to just always pass the @samp{--thread} and
26451 @samp{--frame} options.
26453 @subsubsection Language
26455 The execution of several commands depends on which language is selected.
26456 By default, the current language (@pxref{show language}) is used.
26457 But for commands known to be language-sensitive, it is recommended
26458 to use the @samp{--language} option. This option takes one argument,
26459 which is the name of the language to use while executing the command.
26463 -data-evaluate-expression --language c "sizeof (void*)"
26468 The valid language names are the same names accepted by the
26469 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26470 @samp{local} or @samp{unknown}.
26472 @node Asynchronous and non-stop modes
26473 @subsection Asynchronous command execution and non-stop mode
26475 On some targets, @value{GDBN} is capable of processing MI commands
26476 even while the target is running. This is called @dfn{asynchronous
26477 command execution} (@pxref{Background Execution}). The frontend may
26478 specify a preferrence for asynchronous execution using the
26479 @code{-gdb-set mi-async 1} command, which should be emitted before
26480 either running the executable or attaching to the target. After the
26481 frontend has started the executable or attached to the target, it can
26482 find if asynchronous execution is enabled using the
26483 @code{-list-target-features} command.
26486 @item -gdb-set mi-async on
26487 @item -gdb-set mi-async off
26488 Set whether MI is in asynchronous mode.
26490 When @code{off}, which is the default, MI execution commands (e.g.,
26491 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26492 for the program to stop before processing further commands.
26494 When @code{on}, MI execution commands are background execution
26495 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26496 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26497 MI commands even while the target is running.
26499 @item -gdb-show mi-async
26500 Show whether MI asynchronous mode is enabled.
26503 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26504 @code{target-async} instead of @code{mi-async}, and it had the effect
26505 of both putting MI in asynchronous mode and making CLI background
26506 commands possible. CLI background commands are now always possible
26507 ``out of the box'' if the target supports them. The old spelling is
26508 kept as a deprecated alias for backwards compatibility.
26510 Even if @value{GDBN} can accept a command while target is running,
26511 many commands that access the target do not work when the target is
26512 running. Therefore, asynchronous command execution is most useful
26513 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26514 it is possible to examine the state of one thread, while other threads
26517 When a given thread is running, MI commands that try to access the
26518 target in the context of that thread may not work, or may work only on
26519 some targets. In particular, commands that try to operate on thread's
26520 stack will not work, on any target. Commands that read memory, or
26521 modify breakpoints, may work or not work, depending on the target. Note
26522 that even commands that operate on global state, such as @code{print},
26523 @code{set}, and breakpoint commands, still access the target in the
26524 context of a specific thread, so frontend should try to find a
26525 stopped thread and perform the operation on that thread (using the
26526 @samp{--thread} option).
26528 Which commands will work in the context of a running thread is
26529 highly target dependent. However, the two commands
26530 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26531 to find the state of a thread, will always work.
26533 @node Thread groups
26534 @subsection Thread groups
26535 @value{GDBN} may be used to debug several processes at the same time.
26536 On some platfroms, @value{GDBN} may support debugging of several
26537 hardware systems, each one having several cores with several different
26538 processes running on each core. This section describes the MI
26539 mechanism to support such debugging scenarios.
26541 The key observation is that regardless of the structure of the
26542 target, MI can have a global list of threads, because most commands that
26543 accept the @samp{--thread} option do not need to know what process that
26544 thread belongs to. Therefore, it is not necessary to introduce
26545 neither additional @samp{--process} option, nor an notion of the
26546 current process in the MI interface. The only strictly new feature
26547 that is required is the ability to find how the threads are grouped
26550 To allow the user to discover such grouping, and to support arbitrary
26551 hierarchy of machines/cores/processes, MI introduces the concept of a
26552 @dfn{thread group}. Thread group is a collection of threads and other
26553 thread groups. A thread group always has a string identifier, a type,
26554 and may have additional attributes specific to the type. A new
26555 command, @code{-list-thread-groups}, returns the list of top-level
26556 thread groups, which correspond to processes that @value{GDBN} is
26557 debugging at the moment. By passing an identifier of a thread group
26558 to the @code{-list-thread-groups} command, it is possible to obtain
26559 the members of specific thread group.
26561 To allow the user to easily discover processes, and other objects, he
26562 wishes to debug, a concept of @dfn{available thread group} is
26563 introduced. Available thread group is an thread group that
26564 @value{GDBN} is not debugging, but that can be attached to, using the
26565 @code{-target-attach} command. The list of available top-level thread
26566 groups can be obtained using @samp{-list-thread-groups --available}.
26567 In general, the content of a thread group may be only retrieved only
26568 after attaching to that thread group.
26570 Thread groups are related to inferiors (@pxref{Inferiors and
26571 Programs}). Each inferior corresponds to a thread group of a special
26572 type @samp{process}, and some additional operations are permitted on
26573 such thread groups.
26575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26576 @node GDB/MI Command Syntax
26577 @section @sc{gdb/mi} Command Syntax
26580 * GDB/MI Input Syntax::
26581 * GDB/MI Output Syntax::
26584 @node GDB/MI Input Syntax
26585 @subsection @sc{gdb/mi} Input Syntax
26587 @cindex input syntax for @sc{gdb/mi}
26588 @cindex @sc{gdb/mi}, input syntax
26590 @item @var{command} @expansion{}
26591 @code{@var{cli-command} | @var{mi-command}}
26593 @item @var{cli-command} @expansion{}
26594 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26595 @var{cli-command} is any existing @value{GDBN} CLI command.
26597 @item @var{mi-command} @expansion{}
26598 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26599 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26601 @item @var{token} @expansion{}
26602 "any sequence of digits"
26604 @item @var{option} @expansion{}
26605 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26607 @item @var{parameter} @expansion{}
26608 @code{@var{non-blank-sequence} | @var{c-string}}
26610 @item @var{operation} @expansion{}
26611 @emph{any of the operations described in this chapter}
26613 @item @var{non-blank-sequence} @expansion{}
26614 @emph{anything, provided it doesn't contain special characters such as
26615 "-", @var{nl}, """ and of course " "}
26617 @item @var{c-string} @expansion{}
26618 @code{""" @var{seven-bit-iso-c-string-content} """}
26620 @item @var{nl} @expansion{}
26629 The CLI commands are still handled by the @sc{mi} interpreter; their
26630 output is described below.
26633 The @code{@var{token}}, when present, is passed back when the command
26637 Some @sc{mi} commands accept optional arguments as part of the parameter
26638 list. Each option is identified by a leading @samp{-} (dash) and may be
26639 followed by an optional argument parameter. Options occur first in the
26640 parameter list and can be delimited from normal parameters using
26641 @samp{--} (this is useful when some parameters begin with a dash).
26648 We want easy access to the existing CLI syntax (for debugging).
26651 We want it to be easy to spot a @sc{mi} operation.
26654 @node GDB/MI Output Syntax
26655 @subsection @sc{gdb/mi} Output Syntax
26657 @cindex output syntax of @sc{gdb/mi}
26658 @cindex @sc{gdb/mi}, output syntax
26659 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26660 followed, optionally, by a single result record. This result record
26661 is for the most recent command. The sequence of output records is
26662 terminated by @samp{(gdb)}.
26664 If an input command was prefixed with a @code{@var{token}} then the
26665 corresponding output for that command will also be prefixed by that same
26669 @item @var{output} @expansion{}
26670 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26672 @item @var{result-record} @expansion{}
26673 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26675 @item @var{out-of-band-record} @expansion{}
26676 @code{@var{async-record} | @var{stream-record}}
26678 @item @var{async-record} @expansion{}
26679 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26681 @item @var{exec-async-output} @expansion{}
26682 @code{[ @var{token} ] "*" @var{async-output nl}}
26684 @item @var{status-async-output} @expansion{}
26685 @code{[ @var{token} ] "+" @var{async-output nl}}
26687 @item @var{notify-async-output} @expansion{}
26688 @code{[ @var{token} ] "=" @var{async-output nl}}
26690 @item @var{async-output} @expansion{}
26691 @code{@var{async-class} ( "," @var{result} )*}
26693 @item @var{result-class} @expansion{}
26694 @code{"done" | "running" | "connected" | "error" | "exit"}
26696 @item @var{async-class} @expansion{}
26697 @code{"stopped" | @var{others}} (where @var{others} will be added
26698 depending on the needs---this is still in development).
26700 @item @var{result} @expansion{}
26701 @code{ @var{variable} "=" @var{value}}
26703 @item @var{variable} @expansion{}
26704 @code{ @var{string} }
26706 @item @var{value} @expansion{}
26707 @code{ @var{const} | @var{tuple} | @var{list} }
26709 @item @var{const} @expansion{}
26710 @code{@var{c-string}}
26712 @item @var{tuple} @expansion{}
26713 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26715 @item @var{list} @expansion{}
26716 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26717 @var{result} ( "," @var{result} )* "]" }
26719 @item @var{stream-record} @expansion{}
26720 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26722 @item @var{console-stream-output} @expansion{}
26723 @code{"~" @var{c-string nl}}
26725 @item @var{target-stream-output} @expansion{}
26726 @code{"@@" @var{c-string nl}}
26728 @item @var{log-stream-output} @expansion{}
26729 @code{"&" @var{c-string nl}}
26731 @item @var{nl} @expansion{}
26734 @item @var{token} @expansion{}
26735 @emph{any sequence of digits}.
26743 All output sequences end in a single line containing a period.
26746 The @code{@var{token}} is from the corresponding request. Note that
26747 for all async output, while the token is allowed by the grammar and
26748 may be output by future versions of @value{GDBN} for select async
26749 output messages, it is generally omitted. Frontends should treat
26750 all async output as reporting general changes in the state of the
26751 target and there should be no need to associate async output to any
26755 @cindex status output in @sc{gdb/mi}
26756 @var{status-async-output} contains on-going status information about the
26757 progress of a slow operation. It can be discarded. All status output is
26758 prefixed by @samp{+}.
26761 @cindex async output in @sc{gdb/mi}
26762 @var{exec-async-output} contains asynchronous state change on the target
26763 (stopped, started, disappeared). All async output is prefixed by
26767 @cindex notify output in @sc{gdb/mi}
26768 @var{notify-async-output} contains supplementary information that the
26769 client should handle (e.g., a new breakpoint information). All notify
26770 output is prefixed by @samp{=}.
26773 @cindex console output in @sc{gdb/mi}
26774 @var{console-stream-output} is output that should be displayed as is in the
26775 console. It is the textual response to a CLI command. All the console
26776 output is prefixed by @samp{~}.
26779 @cindex target output in @sc{gdb/mi}
26780 @var{target-stream-output} is the output produced by the target program.
26781 All the target output is prefixed by @samp{@@}.
26784 @cindex log output in @sc{gdb/mi}
26785 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26786 instance messages that should be displayed as part of an error log. All
26787 the log output is prefixed by @samp{&}.
26790 @cindex list output in @sc{gdb/mi}
26791 New @sc{gdb/mi} commands should only output @var{lists} containing
26797 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26798 details about the various output records.
26800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26801 @node GDB/MI Compatibility with CLI
26802 @section @sc{gdb/mi} Compatibility with CLI
26804 @cindex compatibility, @sc{gdb/mi} and CLI
26805 @cindex @sc{gdb/mi}, compatibility with CLI
26807 For the developers convenience CLI commands can be entered directly,
26808 but there may be some unexpected behaviour. For example, commands
26809 that query the user will behave as if the user replied yes, breakpoint
26810 command lists are not executed and some CLI commands, such as
26811 @code{if}, @code{when} and @code{define}, prompt for further input with
26812 @samp{>}, which is not valid MI output.
26814 This feature may be removed at some stage in the future and it is
26815 recommended that front ends use the @code{-interpreter-exec} command
26816 (@pxref{-interpreter-exec}).
26818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26819 @node GDB/MI Development and Front Ends
26820 @section @sc{gdb/mi} Development and Front Ends
26821 @cindex @sc{gdb/mi} development
26823 The application which takes the MI output and presents the state of the
26824 program being debugged to the user is called a @dfn{front end}.
26826 Although @sc{gdb/mi} is still incomplete, it is currently being used
26827 by a variety of front ends to @value{GDBN}. This makes it difficult
26828 to introduce new functionality without breaking existing usage. This
26829 section tries to minimize the problems by describing how the protocol
26832 Some changes in MI need not break a carefully designed front end, and
26833 for these the MI version will remain unchanged. The following is a
26834 list of changes that may occur within one level, so front ends should
26835 parse MI output in a way that can handle them:
26839 New MI commands may be added.
26842 New fields may be added to the output of any MI command.
26845 The range of values for fields with specified values, e.g.,
26846 @code{in_scope} (@pxref{-var-update}) may be extended.
26848 @c The format of field's content e.g type prefix, may change so parse it
26849 @c at your own risk. Yes, in general?
26851 @c The order of fields may change? Shouldn't really matter but it might
26852 @c resolve inconsistencies.
26855 If the changes are likely to break front ends, the MI version level
26856 will be increased by one. This will allow the front end to parse the
26857 output according to the MI version. Apart from mi0, new versions of
26858 @value{GDBN} will not support old versions of MI and it will be the
26859 responsibility of the front end to work with the new one.
26861 @c Starting with mi3, add a new command -mi-version that prints the MI
26864 The best way to avoid unexpected changes in MI that might break your front
26865 end is to make your project known to @value{GDBN} developers and
26866 follow development on @email{gdb@@sourceware.org} and
26867 @email{gdb-patches@@sourceware.org}.
26868 @cindex mailing lists
26870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26871 @node GDB/MI Output Records
26872 @section @sc{gdb/mi} Output Records
26875 * GDB/MI Result Records::
26876 * GDB/MI Stream Records::
26877 * GDB/MI Async Records::
26878 * GDB/MI Breakpoint Information::
26879 * GDB/MI Frame Information::
26880 * GDB/MI Thread Information::
26881 * GDB/MI Ada Exception Information::
26884 @node GDB/MI Result Records
26885 @subsection @sc{gdb/mi} Result Records
26887 @cindex result records in @sc{gdb/mi}
26888 @cindex @sc{gdb/mi}, result records
26889 In addition to a number of out-of-band notifications, the response to a
26890 @sc{gdb/mi} command includes one of the following result indications:
26894 @item "^done" [ "," @var{results} ]
26895 The synchronous operation was successful, @code{@var{results}} are the return
26900 This result record is equivalent to @samp{^done}. Historically, it
26901 was output instead of @samp{^done} if the command has resumed the
26902 target. This behaviour is maintained for backward compatibility, but
26903 all frontends should treat @samp{^done} and @samp{^running}
26904 identically and rely on the @samp{*running} output record to determine
26905 which threads are resumed.
26909 @value{GDBN} has connected to a remote target.
26911 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26913 The operation failed. The @code{msg=@var{c-string}} variable contains
26914 the corresponding error message.
26916 If present, the @code{code=@var{c-string}} variable provides an error
26917 code on which consumers can rely on to detect the corresponding
26918 error condition. At present, only one error code is defined:
26921 @item "undefined-command"
26922 Indicates that the command causing the error does not exist.
26927 @value{GDBN} has terminated.
26931 @node GDB/MI Stream Records
26932 @subsection @sc{gdb/mi} Stream Records
26934 @cindex @sc{gdb/mi}, stream records
26935 @cindex stream records in @sc{gdb/mi}
26936 @value{GDBN} internally maintains a number of output streams: the console, the
26937 target, and the log. The output intended for each of these streams is
26938 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26940 Each stream record begins with a unique @dfn{prefix character} which
26941 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26942 Syntax}). In addition to the prefix, each stream record contains a
26943 @code{@var{string-output}}. This is either raw text (with an implicit new
26944 line) or a quoted C string (which does not contain an implicit newline).
26947 @item "~" @var{string-output}
26948 The console output stream contains text that should be displayed in the
26949 CLI console window. It contains the textual responses to CLI commands.
26951 @item "@@" @var{string-output}
26952 The target output stream contains any textual output from the running
26953 target. This is only present when GDB's event loop is truly
26954 asynchronous, which is currently only the case for remote targets.
26956 @item "&" @var{string-output}
26957 The log stream contains debugging messages being produced by @value{GDBN}'s
26961 @node GDB/MI Async Records
26962 @subsection @sc{gdb/mi} Async Records
26964 @cindex async records in @sc{gdb/mi}
26965 @cindex @sc{gdb/mi}, async records
26966 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26967 additional changes that have occurred. Those changes can either be a
26968 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26969 target activity (e.g., target stopped).
26971 The following is the list of possible async records:
26975 @item *running,thread-id="@var{thread}"
26976 The target is now running. The @var{thread} field can be the global
26977 thread ID of the the thread that is now running, and it can be
26978 @samp{all} if all threads are running. The frontend should assume
26979 that no interaction with a running thread is possible after this
26980 notification is produced. The frontend should not assume that this
26981 notification is output only once for any command. @value{GDBN} may
26982 emit this notification several times, either for different threads,
26983 because it cannot resume all threads together, or even for a single
26984 thread, if the thread must be stepped though some code before letting
26987 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26988 The target has stopped. The @var{reason} field can have one of the
26992 @item breakpoint-hit
26993 A breakpoint was reached.
26994 @item watchpoint-trigger
26995 A watchpoint was triggered.
26996 @item read-watchpoint-trigger
26997 A read watchpoint was triggered.
26998 @item access-watchpoint-trigger
26999 An access watchpoint was triggered.
27000 @item function-finished
27001 An -exec-finish or similar CLI command was accomplished.
27002 @item location-reached
27003 An -exec-until or similar CLI command was accomplished.
27004 @item watchpoint-scope
27005 A watchpoint has gone out of scope.
27006 @item end-stepping-range
27007 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27008 similar CLI command was accomplished.
27009 @item exited-signalled
27010 The inferior exited because of a signal.
27012 The inferior exited.
27013 @item exited-normally
27014 The inferior exited normally.
27015 @item signal-received
27016 A signal was received by the inferior.
27018 The inferior has stopped due to a library being loaded or unloaded.
27019 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27020 set or when a @code{catch load} or @code{catch unload} catchpoint is
27021 in use (@pxref{Set Catchpoints}).
27023 The inferior has forked. This is reported when @code{catch fork}
27024 (@pxref{Set Catchpoints}) has been used.
27026 The inferior has vforked. This is reported in when @code{catch vfork}
27027 (@pxref{Set Catchpoints}) has been used.
27028 @item syscall-entry
27029 The inferior entered a system call. This is reported when @code{catch
27030 syscall} (@pxref{Set Catchpoints}) has been used.
27031 @item syscall-return
27032 The inferior returned from a system call. This is reported when
27033 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27035 The inferior called @code{exec}. This is reported when @code{catch exec}
27036 (@pxref{Set Catchpoints}) has been used.
27039 The @var{id} field identifies the global thread ID of the thread
27040 that directly caused the stop -- for example by hitting a breakpoint.
27041 Depending on whether all-stop
27042 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27043 stop all threads, or only the thread that directly triggered the stop.
27044 If all threads are stopped, the @var{stopped} field will have the
27045 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27046 field will be a list of thread identifiers. Presently, this list will
27047 always include a single thread, but frontend should be prepared to see
27048 several threads in the list. The @var{core} field reports the
27049 processor core on which the stop event has happened. This field may be absent
27050 if such information is not available.
27052 @item =thread-group-added,id="@var{id}"
27053 @itemx =thread-group-removed,id="@var{id}"
27054 A thread group was either added or removed. The @var{id} field
27055 contains the @value{GDBN} identifier of the thread group. When a thread
27056 group is added, it generally might not be associated with a running
27057 process. When a thread group is removed, its id becomes invalid and
27058 cannot be used in any way.
27060 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27061 A thread group became associated with a running program,
27062 either because the program was just started or the thread group
27063 was attached to a program. The @var{id} field contains the
27064 @value{GDBN} identifier of the thread group. The @var{pid} field
27065 contains process identifier, specific to the operating system.
27067 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27068 A thread group is no longer associated with a running program,
27069 either because the program has exited, or because it was detached
27070 from. The @var{id} field contains the @value{GDBN} identifier of the
27071 thread group. The @var{code} field is the exit code of the inferior; it exists
27072 only when the inferior exited with some code.
27074 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27075 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27076 A thread either was created, or has exited. The @var{id} field
27077 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27078 field identifies the thread group this thread belongs to.
27080 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27081 Informs that the selected thread or frame were changed. This notification
27082 is not emitted as result of the @code{-thread-select} or
27083 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27084 that is not documented to change the selected thread and frame actually
27085 changes them. In particular, invoking, directly or indirectly
27086 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27087 will generate this notification. Changing the thread or frame from another
27088 user interface (see @ref{Interpreters}) will also generate this notification.
27090 The @var{frame} field is only present if the newly selected thread is
27091 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27093 We suggest that in response to this notification, front ends
27094 highlight the selected thread and cause subsequent commands to apply to
27097 @item =library-loaded,...
27098 Reports that a new library file was loaded by the program. This
27099 notification has 5 fields---@var{id}, @var{target-name},
27100 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27101 opaque identifier of the library. For remote debugging case,
27102 @var{target-name} and @var{host-name} fields give the name of the
27103 library file on the target, and on the host respectively. For native
27104 debugging, both those fields have the same value. The
27105 @var{symbols-loaded} field is emitted only for backward compatibility
27106 and should not be relied on to convey any useful information. The
27107 @var{thread-group} field, if present, specifies the id of the thread
27108 group in whose context the library was loaded. If the field is
27109 absent, it means the library was loaded in the context of all present
27110 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27113 @item =library-unloaded,...
27114 Reports that a library was unloaded by the program. This notification
27115 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27116 the same meaning as for the @code{=library-loaded} notification.
27117 The @var{thread-group} field, if present, specifies the id of the
27118 thread group in whose context the library was unloaded. If the field is
27119 absent, it means the library was unloaded in the context of all present
27122 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27123 @itemx =traceframe-changed,end
27124 Reports that the trace frame was changed and its new number is
27125 @var{tfnum}. The number of the tracepoint associated with this trace
27126 frame is @var{tpnum}.
27128 @item =tsv-created,name=@var{name},initial=@var{initial}
27129 Reports that the new trace state variable @var{name} is created with
27130 initial value @var{initial}.
27132 @item =tsv-deleted,name=@var{name}
27133 @itemx =tsv-deleted
27134 Reports that the trace state variable @var{name} is deleted or all
27135 trace state variables are deleted.
27137 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27138 Reports that the trace state variable @var{name} is modified with
27139 the initial value @var{initial}. The current value @var{current} of
27140 trace state variable is optional and is reported if the current
27141 value of trace state variable is known.
27143 @item =breakpoint-created,bkpt=@{...@}
27144 @itemx =breakpoint-modified,bkpt=@{...@}
27145 @itemx =breakpoint-deleted,id=@var{number}
27146 Reports that a breakpoint was created, modified, or deleted,
27147 respectively. Only user-visible breakpoints are reported to the MI
27150 The @var{bkpt} argument is of the same form as returned by the various
27151 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27152 @var{number} is the ordinal number of the breakpoint.
27154 Note that if a breakpoint is emitted in the result record of a
27155 command, then it will not also be emitted in an async record.
27157 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27158 @itemx =record-stopped,thread-group="@var{id}"
27159 Execution log recording was either started or stopped on an
27160 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27161 group corresponding to the affected inferior.
27163 The @var{method} field indicates the method used to record execution. If the
27164 method in use supports multiple recording formats, @var{format} will be present
27165 and contain the currently used format. @xref{Process Record and Replay},
27166 for existing method and format values.
27168 @item =cmd-param-changed,param=@var{param},value=@var{value}
27169 Reports that a parameter of the command @code{set @var{param}} is
27170 changed to @var{value}. In the multi-word @code{set} command,
27171 the @var{param} is the whole parameter list to @code{set} command.
27172 For example, In command @code{set check type on}, @var{param}
27173 is @code{check type} and @var{value} is @code{on}.
27175 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27176 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27177 written in an inferior. The @var{id} is the identifier of the
27178 thread group corresponding to the affected inferior. The optional
27179 @code{type="code"} part is reported if the memory written to holds
27183 @node GDB/MI Breakpoint Information
27184 @subsection @sc{gdb/mi} Breakpoint Information
27186 When @value{GDBN} reports information about a breakpoint, a
27187 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27192 The breakpoint number. For a breakpoint that represents one location
27193 of a multi-location breakpoint, this will be a dotted pair, like
27197 The type of the breakpoint. For ordinary breakpoints this will be
27198 @samp{breakpoint}, but many values are possible.
27201 If the type of the breakpoint is @samp{catchpoint}, then this
27202 indicates the exact type of catchpoint.
27205 This is the breakpoint disposition---either @samp{del}, meaning that
27206 the breakpoint will be deleted at the next stop, or @samp{keep},
27207 meaning that the breakpoint will not be deleted.
27210 This indicates whether the breakpoint is enabled, in which case the
27211 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27212 Note that this is not the same as the field @code{enable}.
27215 The address of the breakpoint. This may be a hexidecimal number,
27216 giving the address; or the string @samp{<PENDING>}, for a pending
27217 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27218 multiple locations. This field will not be present if no address can
27219 be determined. For example, a watchpoint does not have an address.
27222 If known, the function in which the breakpoint appears.
27223 If not known, this field is not present.
27226 The name of the source file which contains this function, if known.
27227 If not known, this field is not present.
27230 The full file name of the source file which contains this function, if
27231 known. If not known, this field is not present.
27234 The line number at which this breakpoint appears, if known.
27235 If not known, this field is not present.
27238 If the source file is not known, this field may be provided. If
27239 provided, this holds the address of the breakpoint, possibly followed
27243 If this breakpoint is pending, this field is present and holds the
27244 text used to set the breakpoint, as entered by the user.
27247 Where this breakpoint's condition is evaluated, either @samp{host} or
27251 If this is a thread-specific breakpoint, then this identifies the
27252 thread in which the breakpoint can trigger.
27255 If this breakpoint is restricted to a particular Ada task, then this
27256 field will hold the task identifier.
27259 If the breakpoint is conditional, this is the condition expression.
27262 The ignore count of the breakpoint.
27265 The enable count of the breakpoint.
27267 @item traceframe-usage
27270 @item static-tracepoint-marker-string-id
27271 For a static tracepoint, the name of the static tracepoint marker.
27274 For a masked watchpoint, this is the mask.
27277 A tracepoint's pass count.
27279 @item original-location
27280 The location of the breakpoint as originally specified by the user.
27281 This field is optional.
27284 The number of times the breakpoint has been hit.
27287 This field is only given for tracepoints. This is either @samp{y},
27288 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27292 Some extra data, the exact contents of which are type-dependent.
27296 For example, here is what the output of @code{-break-insert}
27297 (@pxref{GDB/MI Breakpoint Commands}) might be:
27300 -> -break-insert main
27301 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27302 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27303 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27308 @node GDB/MI Frame Information
27309 @subsection @sc{gdb/mi} Frame Information
27311 Response from many MI commands includes an information about stack
27312 frame. This information is a tuple that may have the following
27317 The level of the stack frame. The innermost frame has the level of
27318 zero. This field is always present.
27321 The name of the function corresponding to the frame. This field may
27322 be absent if @value{GDBN} is unable to determine the function name.
27325 The code address for the frame. This field is always present.
27328 The name of the source files that correspond to the frame's code
27329 address. This field may be absent.
27332 The source line corresponding to the frames' code address. This field
27336 The name of the binary file (either executable or shared library) the
27337 corresponds to the frame's code address. This field may be absent.
27341 @node GDB/MI Thread Information
27342 @subsection @sc{gdb/mi} Thread Information
27344 Whenever @value{GDBN} has to report an information about a thread, it
27345 uses a tuple with the following fields. The fields are always present unless
27350 The global numeric id assigned to the thread by @value{GDBN}.
27353 The target-specific string identifying the thread.
27356 Additional information about the thread provided by the target.
27357 It is supposed to be human-readable and not interpreted by the
27358 frontend. This field is optional.
27361 The name of the thread. If the user specified a name using the
27362 @code{thread name} command, then this name is given. Otherwise, if
27363 @value{GDBN} can extract the thread name from the target, then that
27364 name is given. If @value{GDBN} cannot find the thread name, then this
27368 The execution state of the thread, either @samp{stopped} or @samp{running},
27369 depending on whether the thread is presently running.
27372 The stack frame currently executing in the thread. This field is only present
27373 if the thread is stopped. Its format is documented in
27374 @ref{GDB/MI Frame Information}.
27377 The value of this field is an integer number of the processor core the
27378 thread was last seen on. This field is optional.
27381 @node GDB/MI Ada Exception Information
27382 @subsection @sc{gdb/mi} Ada Exception Information
27384 Whenever a @code{*stopped} record is emitted because the program
27385 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27386 @value{GDBN} provides the name of the exception that was raised via
27387 the @code{exception-name} field. Also, for exceptions that were raised
27388 with an exception message, @value{GDBN} provides that message via
27389 the @code{exception-message} field.
27391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27392 @node GDB/MI Simple Examples
27393 @section Simple Examples of @sc{gdb/mi} Interaction
27394 @cindex @sc{gdb/mi}, simple examples
27396 This subsection presents several simple examples of interaction using
27397 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27398 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27399 the output received from @sc{gdb/mi}.
27401 Note the line breaks shown in the examples are here only for
27402 readability, they don't appear in the real output.
27404 @subheading Setting a Breakpoint
27406 Setting a breakpoint generates synchronous output which contains detailed
27407 information of the breakpoint.
27410 -> -break-insert main
27411 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27412 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27413 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27418 @subheading Program Execution
27420 Program execution generates asynchronous records and MI gives the
27421 reason that execution stopped.
27427 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27428 frame=@{addr="0x08048564",func="main",
27429 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27430 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27435 <- *stopped,reason="exited-normally"
27439 @subheading Quitting @value{GDBN}
27441 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27449 Please note that @samp{^exit} is printed immediately, but it might
27450 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27451 performs necessary cleanups, including killing programs being debugged
27452 or disconnecting from debug hardware, so the frontend should wait till
27453 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27454 fails to exit in reasonable time.
27456 @subheading A Bad Command
27458 Here's what happens if you pass a non-existent command:
27462 <- ^error,msg="Undefined MI command: rubbish"
27467 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27468 @node GDB/MI Command Description Format
27469 @section @sc{gdb/mi} Command Description Format
27471 The remaining sections describe blocks of commands. Each block of
27472 commands is laid out in a fashion similar to this section.
27474 @subheading Motivation
27476 The motivation for this collection of commands.
27478 @subheading Introduction
27480 A brief introduction to this collection of commands as a whole.
27482 @subheading Commands
27484 For each command in the block, the following is described:
27486 @subsubheading Synopsis
27489 -command @var{args}@dots{}
27492 @subsubheading Result
27494 @subsubheading @value{GDBN} Command
27496 The corresponding @value{GDBN} CLI command(s), if any.
27498 @subsubheading Example
27500 Example(s) formatted for readability. Some of the described commands have
27501 not been implemented yet and these are labeled N.A.@: (not available).
27504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27505 @node GDB/MI Breakpoint Commands
27506 @section @sc{gdb/mi} Breakpoint Commands
27508 @cindex breakpoint commands for @sc{gdb/mi}
27509 @cindex @sc{gdb/mi}, breakpoint commands
27510 This section documents @sc{gdb/mi} commands for manipulating
27513 @subheading The @code{-break-after} Command
27514 @findex -break-after
27516 @subsubheading Synopsis
27519 -break-after @var{number} @var{count}
27522 The breakpoint number @var{number} is not in effect until it has been
27523 hit @var{count} times. To see how this is reflected in the output of
27524 the @samp{-break-list} command, see the description of the
27525 @samp{-break-list} command below.
27527 @subsubheading @value{GDBN} Command
27529 The corresponding @value{GDBN} command is @samp{ignore}.
27531 @subsubheading Example
27536 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27537 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27538 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27546 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27547 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27548 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27549 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27550 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27551 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27552 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27553 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27554 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27555 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27560 @subheading The @code{-break-catch} Command
27561 @findex -break-catch
27564 @subheading The @code{-break-commands} Command
27565 @findex -break-commands
27567 @subsubheading Synopsis
27570 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27573 Specifies the CLI commands that should be executed when breakpoint
27574 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27575 are the commands. If no command is specified, any previously-set
27576 commands are cleared. @xref{Break Commands}. Typical use of this
27577 functionality is tracing a program, that is, printing of values of
27578 some variables whenever breakpoint is hit and then continuing.
27580 @subsubheading @value{GDBN} Command
27582 The corresponding @value{GDBN} command is @samp{commands}.
27584 @subsubheading Example
27589 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27590 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27591 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27594 -break-commands 1 "print v" "continue"
27599 @subheading The @code{-break-condition} Command
27600 @findex -break-condition
27602 @subsubheading Synopsis
27605 -break-condition @var{number} @var{expr}
27608 Breakpoint @var{number} will stop the program only if the condition in
27609 @var{expr} is true. The condition becomes part of the
27610 @samp{-break-list} output (see the description of the @samp{-break-list}
27613 @subsubheading @value{GDBN} Command
27615 The corresponding @value{GDBN} command is @samp{condition}.
27617 @subsubheading Example
27621 -break-condition 1 1
27625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27632 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27633 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27634 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27638 @subheading The @code{-break-delete} Command
27639 @findex -break-delete
27641 @subsubheading Synopsis
27644 -break-delete ( @var{breakpoint} )+
27647 Delete the breakpoint(s) whose number(s) are specified in the argument
27648 list. This is obviously reflected in the breakpoint list.
27650 @subsubheading @value{GDBN} Command
27652 The corresponding @value{GDBN} command is @samp{delete}.
27654 @subsubheading Example
27662 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27663 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27664 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27665 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27666 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27667 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27668 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27673 @subheading The @code{-break-disable} Command
27674 @findex -break-disable
27676 @subsubheading Synopsis
27679 -break-disable ( @var{breakpoint} )+
27682 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27683 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27685 @subsubheading @value{GDBN} Command
27687 The corresponding @value{GDBN} command is @samp{disable}.
27689 @subsubheading Example
27697 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27698 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27699 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27700 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27701 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27702 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27703 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27704 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27705 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27706 line="5",thread-groups=["i1"],times="0"@}]@}
27710 @subheading The @code{-break-enable} Command
27711 @findex -break-enable
27713 @subsubheading Synopsis
27716 -break-enable ( @var{breakpoint} )+
27719 Enable (previously disabled) @var{breakpoint}(s).
27721 @subsubheading @value{GDBN} Command
27723 The corresponding @value{GDBN} command is @samp{enable}.
27725 @subsubheading Example
27733 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27740 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27741 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27742 line="5",thread-groups=["i1"],times="0"@}]@}
27746 @subheading The @code{-break-info} Command
27747 @findex -break-info
27749 @subsubheading Synopsis
27752 -break-info @var{breakpoint}
27756 Get information about a single breakpoint.
27758 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27759 Information}, for details on the format of each breakpoint in the
27762 @subsubheading @value{GDBN} Command
27764 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27766 @subsubheading Example
27769 @subheading The @code{-break-insert} Command
27770 @findex -break-insert
27771 @anchor{-break-insert}
27773 @subsubheading Synopsis
27776 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27777 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27778 [ -p @var{thread-id} ] [ @var{location} ]
27782 If specified, @var{location}, can be one of:
27785 @item linespec location
27786 A linespec location. @xref{Linespec Locations}.
27788 @item explicit location
27789 An explicit location. @sc{gdb/mi} explicit locations are
27790 analogous to the CLI's explicit locations using the option names
27791 listed below. @xref{Explicit Locations}.
27794 @item --source @var{filename}
27795 The source file name of the location. This option requires the use
27796 of either @samp{--function} or @samp{--line}.
27798 @item --function @var{function}
27799 The name of a function or method.
27801 @item --label @var{label}
27802 The name of a label.
27804 @item --line @var{lineoffset}
27805 An absolute or relative line offset from the start of the location.
27808 @item address location
27809 An address location, *@var{address}. @xref{Address Locations}.
27813 The possible optional parameters of this command are:
27817 Insert a temporary breakpoint.
27819 Insert a hardware breakpoint.
27821 If @var{location} cannot be parsed (for example if it
27822 refers to unknown files or functions), create a pending
27823 breakpoint. Without this flag, @value{GDBN} will report
27824 an error, and won't create a breakpoint, if @var{location}
27827 Create a disabled breakpoint.
27829 Create a tracepoint. @xref{Tracepoints}. When this parameter
27830 is used together with @samp{-h}, a fast tracepoint is created.
27831 @item -c @var{condition}
27832 Make the breakpoint conditional on @var{condition}.
27833 @item -i @var{ignore-count}
27834 Initialize the @var{ignore-count}.
27835 @item -p @var{thread-id}
27836 Restrict the breakpoint to the thread with the specified global
27840 @subsubheading Result
27842 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27843 resulting breakpoint.
27845 Note: this format is open to change.
27846 @c An out-of-band breakpoint instead of part of the result?
27848 @subsubheading @value{GDBN} Command
27850 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27851 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27853 @subsubheading Example
27858 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27859 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27862 -break-insert -t foo
27863 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27864 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27868 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27869 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27870 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27871 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27872 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27873 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27874 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27875 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27876 addr="0x0001072c", func="main",file="recursive2.c",
27877 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27879 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27880 addr="0x00010774",func="foo",file="recursive2.c",
27881 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27884 @c -break-insert -r foo.*
27885 @c ~int foo(int, int);
27886 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27887 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27892 @subheading The @code{-dprintf-insert} Command
27893 @findex -dprintf-insert
27895 @subsubheading Synopsis
27898 -dprintf-insert [ -t ] [ -f ] [ -d ]
27899 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27900 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27905 If supplied, @var{location} may be specified the same way as for
27906 the @code{-break-insert} command. @xref{-break-insert}.
27908 The possible optional parameters of this command are:
27912 Insert a temporary breakpoint.
27914 If @var{location} cannot be parsed (for example, if it
27915 refers to unknown files or functions), create a pending
27916 breakpoint. Without this flag, @value{GDBN} will report
27917 an error, and won't create a breakpoint, if @var{location}
27920 Create a disabled breakpoint.
27921 @item -c @var{condition}
27922 Make the breakpoint conditional on @var{condition}.
27923 @item -i @var{ignore-count}
27924 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27925 to @var{ignore-count}.
27926 @item -p @var{thread-id}
27927 Restrict the breakpoint to the thread with the specified global
27931 @subsubheading Result
27933 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27934 resulting breakpoint.
27936 @c An out-of-band breakpoint instead of part of the result?
27938 @subsubheading @value{GDBN} Command
27940 The corresponding @value{GDBN} command is @samp{dprintf}.
27942 @subsubheading Example
27946 4-dprintf-insert foo "At foo entry\n"
27947 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27948 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27949 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27950 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27951 original-location="foo"@}
27953 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27954 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27955 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27956 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27957 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27958 original-location="mi-dprintf.c:26"@}
27962 @subheading The @code{-break-list} Command
27963 @findex -break-list
27965 @subsubheading Synopsis
27971 Displays the list of inserted breakpoints, showing the following fields:
27975 number of the breakpoint
27977 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27979 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27982 is the breakpoint enabled or no: @samp{y} or @samp{n}
27984 memory location at which the breakpoint is set
27986 logical location of the breakpoint, expressed by function name, file
27988 @item Thread-groups
27989 list of thread groups to which this breakpoint applies
27991 number of times the breakpoint has been hit
27994 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27995 @code{body} field is an empty list.
27997 @subsubheading @value{GDBN} Command
27999 The corresponding @value{GDBN} command is @samp{info break}.
28001 @subsubheading Example
28006 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28007 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28008 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28009 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28010 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28011 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28012 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28013 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28014 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28016 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28017 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28018 line="13",thread-groups=["i1"],times="0"@}]@}
28022 Here's an example of the result when there are no breakpoints:
28027 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28028 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28029 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28030 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28031 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28032 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28033 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28038 @subheading The @code{-break-passcount} Command
28039 @findex -break-passcount
28041 @subsubheading Synopsis
28044 -break-passcount @var{tracepoint-number} @var{passcount}
28047 Set the passcount for tracepoint @var{tracepoint-number} to
28048 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28049 is not a tracepoint, error is emitted. This corresponds to CLI
28050 command @samp{passcount}.
28052 @subheading The @code{-break-watch} Command
28053 @findex -break-watch
28055 @subsubheading Synopsis
28058 -break-watch [ -a | -r ]
28061 Create a watchpoint. With the @samp{-a} option it will create an
28062 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28063 read from or on a write to the memory location. With the @samp{-r}
28064 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28065 trigger only when the memory location is accessed for reading. Without
28066 either of the options, the watchpoint created is a regular watchpoint,
28067 i.e., it will trigger when the memory location is accessed for writing.
28068 @xref{Set Watchpoints, , Setting Watchpoints}.
28070 Note that @samp{-break-list} will report a single list of watchpoints and
28071 breakpoints inserted.
28073 @subsubheading @value{GDBN} Command
28075 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28078 @subsubheading Example
28080 Setting a watchpoint on a variable in the @code{main} function:
28085 ^done,wpt=@{number="2",exp="x"@}
28090 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28091 value=@{old="-268439212",new="55"@},
28092 frame=@{func="main",args=[],file="recursive2.c",
28093 fullname="/home/foo/bar/recursive2.c",line="5"@}
28097 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28098 the program execution twice: first for the variable changing value, then
28099 for the watchpoint going out of scope.
28104 ^done,wpt=@{number="5",exp="C"@}
28109 *stopped,reason="watchpoint-trigger",
28110 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28111 frame=@{func="callee4",args=[],
28112 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28113 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28118 *stopped,reason="watchpoint-scope",wpnum="5",
28119 frame=@{func="callee3",args=[@{name="strarg",
28120 value="0x11940 \"A string argument.\""@}],
28121 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28122 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28126 Listing breakpoints and watchpoints, at different points in the program
28127 execution. Note that once the watchpoint goes out of scope, it is
28133 ^done,wpt=@{number="2",exp="C"@}
28136 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28137 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28138 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28139 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28140 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28141 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28142 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28143 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28144 addr="0x00010734",func="callee4",
28145 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28146 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28148 bkpt=@{number="2",type="watchpoint",disp="keep",
28149 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28154 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28155 value=@{old="-276895068",new="3"@},
28156 frame=@{func="callee4",args=[],
28157 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28158 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28161 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28169 addr="0x00010734",func="callee4",
28170 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28171 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28173 bkpt=@{number="2",type="watchpoint",disp="keep",
28174 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28178 ^done,reason="watchpoint-scope",wpnum="2",
28179 frame=@{func="callee3",args=[@{name="strarg",
28180 value="0x11940 \"A string argument.\""@}],
28181 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28182 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28185 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28186 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28187 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28188 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28189 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28190 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28191 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28192 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28193 addr="0x00010734",func="callee4",
28194 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28195 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28196 thread-groups=["i1"],times="1"@}]@}
28201 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28202 @node GDB/MI Catchpoint Commands
28203 @section @sc{gdb/mi} Catchpoint Commands
28205 This section documents @sc{gdb/mi} commands for manipulating
28209 * Shared Library GDB/MI Catchpoint Commands::
28210 * Ada Exception GDB/MI Catchpoint Commands::
28213 @node Shared Library GDB/MI Catchpoint Commands
28214 @subsection Shared Library @sc{gdb/mi} Catchpoints
28216 @subheading The @code{-catch-load} Command
28217 @findex -catch-load
28219 @subsubheading Synopsis
28222 -catch-load [ -t ] [ -d ] @var{regexp}
28225 Add a catchpoint for library load events. If the @samp{-t} option is used,
28226 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28227 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28228 in a disabled state. The @samp{regexp} argument is a regular
28229 expression used to match the name of the loaded library.
28232 @subsubheading @value{GDBN} Command
28234 The corresponding @value{GDBN} command is @samp{catch load}.
28236 @subsubheading Example
28239 -catch-load -t foo.so
28240 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28241 what="load of library matching foo.so",catch-type="load",times="0"@}
28246 @subheading The @code{-catch-unload} Command
28247 @findex -catch-unload
28249 @subsubheading Synopsis
28252 -catch-unload [ -t ] [ -d ] @var{regexp}
28255 Add a catchpoint for library unload events. If the @samp{-t} option is
28256 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28257 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28258 created in a disabled state. The @samp{regexp} argument is a regular
28259 expression used to match the name of the unloaded library.
28261 @subsubheading @value{GDBN} Command
28263 The corresponding @value{GDBN} command is @samp{catch unload}.
28265 @subsubheading Example
28268 -catch-unload -d bar.so
28269 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28270 what="load of library matching bar.so",catch-type="unload",times="0"@}
28274 @node Ada Exception GDB/MI Catchpoint Commands
28275 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28277 The following @sc{gdb/mi} commands can be used to create catchpoints
28278 that stop the execution when Ada exceptions are being raised.
28280 @subheading The @code{-catch-assert} Command
28281 @findex -catch-assert
28283 @subsubheading Synopsis
28286 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28289 Add a catchpoint for failed Ada assertions.
28291 The possible optional parameters for this command are:
28294 @item -c @var{condition}
28295 Make the catchpoint conditional on @var{condition}.
28297 Create a disabled catchpoint.
28299 Create a temporary catchpoint.
28302 @subsubheading @value{GDBN} Command
28304 The corresponding @value{GDBN} command is @samp{catch assert}.
28306 @subsubheading Example
28310 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28311 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28312 thread-groups=["i1"],times="0",
28313 original-location="__gnat_debug_raise_assert_failure"@}
28317 @subheading The @code{-catch-exception} Command
28318 @findex -catch-exception
28320 @subsubheading Synopsis
28323 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28327 Add a catchpoint stopping when Ada exceptions are raised.
28328 By default, the command stops the program when any Ada exception
28329 gets raised. But it is also possible, by using some of the
28330 optional parameters described below, to create more selective
28333 The possible optional parameters for this command are:
28336 @item -c @var{condition}
28337 Make the catchpoint conditional on @var{condition}.
28339 Create a disabled catchpoint.
28340 @item -e @var{exception-name}
28341 Only stop when @var{exception-name} is raised. This option cannot
28342 be used combined with @samp{-u}.
28344 Create a temporary catchpoint.
28346 Stop only when an unhandled exception gets raised. This option
28347 cannot be used combined with @samp{-e}.
28350 @subsubheading @value{GDBN} Command
28352 The corresponding @value{GDBN} commands are @samp{catch exception}
28353 and @samp{catch exception unhandled}.
28355 @subsubheading Example
28358 -catch-exception -e Program_Error
28359 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28360 enabled="y",addr="0x0000000000404874",
28361 what="`Program_Error' Ada exception", thread-groups=["i1"],
28362 times="0",original-location="__gnat_debug_raise_exception"@}
28366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28367 @node GDB/MI Program Context
28368 @section @sc{gdb/mi} Program Context
28370 @subheading The @code{-exec-arguments} Command
28371 @findex -exec-arguments
28374 @subsubheading Synopsis
28377 -exec-arguments @var{args}
28380 Set the inferior program arguments, to be used in the next
28383 @subsubheading @value{GDBN} Command
28385 The corresponding @value{GDBN} command is @samp{set args}.
28387 @subsubheading Example
28391 -exec-arguments -v word
28398 @subheading The @code{-exec-show-arguments} Command
28399 @findex -exec-show-arguments
28401 @subsubheading Synopsis
28404 -exec-show-arguments
28407 Print the arguments of the program.
28409 @subsubheading @value{GDBN} Command
28411 The corresponding @value{GDBN} command is @samp{show args}.
28413 @subsubheading Example
28418 @subheading The @code{-environment-cd} Command
28419 @findex -environment-cd
28421 @subsubheading Synopsis
28424 -environment-cd @var{pathdir}
28427 Set @value{GDBN}'s working directory.
28429 @subsubheading @value{GDBN} Command
28431 The corresponding @value{GDBN} command is @samp{cd}.
28433 @subsubheading Example
28437 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28443 @subheading The @code{-environment-directory} Command
28444 @findex -environment-directory
28446 @subsubheading Synopsis
28449 -environment-directory [ -r ] [ @var{pathdir} ]+
28452 Add directories @var{pathdir} to beginning of search path for source files.
28453 If the @samp{-r} option is used, the search path is reset to the default
28454 search path. If directories @var{pathdir} are supplied in addition to the
28455 @samp{-r} option, the search path is first reset and then addition
28457 Multiple directories may be specified, separated by blanks. Specifying
28458 multiple directories in a single command
28459 results in the directories added to the beginning of the
28460 search path in the same order they were presented in the command.
28461 If blanks are needed as
28462 part of a directory name, double-quotes should be used around
28463 the name. In the command output, the path will show up separated
28464 by the system directory-separator character. The directory-separator
28465 character must not be used
28466 in any directory name.
28467 If no directories are specified, the current search path is displayed.
28469 @subsubheading @value{GDBN} Command
28471 The corresponding @value{GDBN} command is @samp{dir}.
28473 @subsubheading Example
28477 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28478 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28480 -environment-directory ""
28481 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28483 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28484 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28486 -environment-directory -r
28487 ^done,source-path="$cdir:$cwd"
28492 @subheading The @code{-environment-path} Command
28493 @findex -environment-path
28495 @subsubheading Synopsis
28498 -environment-path [ -r ] [ @var{pathdir} ]+
28501 Add directories @var{pathdir} to beginning of search path for object files.
28502 If the @samp{-r} option is used, the search path is reset to the original
28503 search path that existed at gdb start-up. If directories @var{pathdir} are
28504 supplied in addition to the
28505 @samp{-r} option, the search path is first reset and then addition
28507 Multiple directories may be specified, separated by blanks. Specifying
28508 multiple directories in a single command
28509 results in the directories added to the beginning of the
28510 search path in the same order they were presented in the command.
28511 If blanks are needed as
28512 part of a directory name, double-quotes should be used around
28513 the name. In the command output, the path will show up separated
28514 by the system directory-separator character. The directory-separator
28515 character must not be used
28516 in any directory name.
28517 If no directories are specified, the current path is displayed.
28520 @subsubheading @value{GDBN} Command
28522 The corresponding @value{GDBN} command is @samp{path}.
28524 @subsubheading Example
28529 ^done,path="/usr/bin"
28531 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28532 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28534 -environment-path -r /usr/local/bin
28535 ^done,path="/usr/local/bin:/usr/bin"
28540 @subheading The @code{-environment-pwd} Command
28541 @findex -environment-pwd
28543 @subsubheading Synopsis
28549 Show the current working directory.
28551 @subsubheading @value{GDBN} Command
28553 The corresponding @value{GDBN} command is @samp{pwd}.
28555 @subsubheading Example
28560 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28564 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28565 @node GDB/MI Thread Commands
28566 @section @sc{gdb/mi} Thread Commands
28569 @subheading The @code{-thread-info} Command
28570 @findex -thread-info
28572 @subsubheading Synopsis
28575 -thread-info [ @var{thread-id} ]
28578 Reports information about either a specific thread, if the
28579 @var{thread-id} parameter is present, or about all threads.
28580 @var{thread-id} is the thread's global thread ID. When printing
28581 information about all threads, also reports the global ID of the
28584 @subsubheading @value{GDBN} Command
28586 The @samp{info thread} command prints the same information
28589 @subsubheading Result
28591 The result contains the following attributes:
28595 A list of threads. The format of the elements of the list is described in
28596 @ref{GDB/MI Thread Information}.
28598 @item current-thread-id
28599 The global id of the currently selected thread. This field is omitted if there
28600 is no selected thread (for example, when the selected inferior is not running,
28601 and therefore has no threads) or if a @var{thread-id} argument was passed to
28606 @subsubheading Example
28611 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28612 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28613 args=[]@},state="running"@},
28614 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28615 frame=@{level="0",addr="0x0804891f",func="foo",
28616 args=[@{name="i",value="10"@}],
28617 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28618 state="running"@}],
28619 current-thread-id="1"
28623 @subheading The @code{-thread-list-ids} Command
28624 @findex -thread-list-ids
28626 @subsubheading Synopsis
28632 Produces a list of the currently known global @value{GDBN} thread ids.
28633 At the end of the list it also prints the total number of such
28636 This command is retained for historical reasons, the
28637 @code{-thread-info} command should be used instead.
28639 @subsubheading @value{GDBN} Command
28641 Part of @samp{info threads} supplies the same information.
28643 @subsubheading Example
28648 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28649 current-thread-id="1",number-of-threads="3"
28654 @subheading The @code{-thread-select} Command
28655 @findex -thread-select
28657 @subsubheading Synopsis
28660 -thread-select @var{thread-id}
28663 Make thread with global thread number @var{thread-id} the current
28664 thread. It prints the number of the new current thread, and the
28665 topmost frame for that thread.
28667 This command is deprecated in favor of explicitly using the
28668 @samp{--thread} option to each command.
28670 @subsubheading @value{GDBN} Command
28672 The corresponding @value{GDBN} command is @samp{thread}.
28674 @subsubheading Example
28681 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28682 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28686 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28687 number-of-threads="3"
28690 ^done,new-thread-id="3",
28691 frame=@{level="0",func="vprintf",
28692 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28693 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28698 @node GDB/MI Ada Tasking Commands
28699 @section @sc{gdb/mi} Ada Tasking Commands
28701 @subheading The @code{-ada-task-info} Command
28702 @findex -ada-task-info
28704 @subsubheading Synopsis
28707 -ada-task-info [ @var{task-id} ]
28710 Reports information about either a specific Ada task, if the
28711 @var{task-id} parameter is present, or about all Ada tasks.
28713 @subsubheading @value{GDBN} Command
28715 The @samp{info tasks} command prints the same information
28716 about all Ada tasks (@pxref{Ada Tasks}).
28718 @subsubheading Result
28720 The result is a table of Ada tasks. The following columns are
28721 defined for each Ada task:
28725 This field exists only for the current thread. It has the value @samp{*}.
28728 The identifier that @value{GDBN} uses to refer to the Ada task.
28731 The identifier that the target uses to refer to the Ada task.
28734 The global thread identifier of the thread corresponding to the Ada
28737 This field should always exist, as Ada tasks are always implemented
28738 on top of a thread. But if @value{GDBN} cannot find this corresponding
28739 thread for any reason, the field is omitted.
28742 This field exists only when the task was created by another task.
28743 In this case, it provides the ID of the parent task.
28746 The base priority of the task.
28749 The current state of the task. For a detailed description of the
28750 possible states, see @ref{Ada Tasks}.
28753 The name of the task.
28757 @subsubheading Example
28761 ^done,tasks=@{nr_rows="3",nr_cols="8",
28762 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28763 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28764 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28765 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28766 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28767 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28768 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28769 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28770 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28771 state="Child Termination Wait",name="main_task"@}]@}
28775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28776 @node GDB/MI Program Execution
28777 @section @sc{gdb/mi} Program Execution
28779 These are the asynchronous commands which generate the out-of-band
28780 record @samp{*stopped}. Currently @value{GDBN} only really executes
28781 asynchronously with remote targets and this interaction is mimicked in
28784 @subheading The @code{-exec-continue} Command
28785 @findex -exec-continue
28787 @subsubheading Synopsis
28790 -exec-continue [--reverse] [--all|--thread-group N]
28793 Resumes the execution of the inferior program, which will continue
28794 to execute until it reaches a debugger stop event. If the
28795 @samp{--reverse} option is specified, execution resumes in reverse until
28796 it reaches a stop event. Stop events may include
28799 breakpoints or watchpoints
28801 signals or exceptions
28803 the end of the process (or its beginning under @samp{--reverse})
28805 the end or beginning of a replay log if one is being used.
28807 In all-stop mode (@pxref{All-Stop
28808 Mode}), may resume only one thread, or all threads, depending on the
28809 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28810 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28811 ignored in all-stop mode. If the @samp{--thread-group} options is
28812 specified, then all threads in that thread group are resumed.
28814 @subsubheading @value{GDBN} Command
28816 The corresponding @value{GDBN} corresponding is @samp{continue}.
28818 @subsubheading Example
28825 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28826 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28832 @subheading The @code{-exec-finish} Command
28833 @findex -exec-finish
28835 @subsubheading Synopsis
28838 -exec-finish [--reverse]
28841 Resumes the execution of the inferior program until the current
28842 function is exited. Displays the results returned by the function.
28843 If the @samp{--reverse} option is specified, resumes the reverse
28844 execution of the inferior program until the point where current
28845 function was called.
28847 @subsubheading @value{GDBN} Command
28849 The corresponding @value{GDBN} command is @samp{finish}.
28851 @subsubheading Example
28853 Function returning @code{void}.
28860 *stopped,reason="function-finished",frame=@{func="main",args=[],
28861 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28865 Function returning other than @code{void}. The name of the internal
28866 @value{GDBN} variable storing the result is printed, together with the
28873 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28874 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28875 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28876 gdb-result-var="$1",return-value="0"
28881 @subheading The @code{-exec-interrupt} Command
28882 @findex -exec-interrupt
28884 @subsubheading Synopsis
28887 -exec-interrupt [--all|--thread-group N]
28890 Interrupts the background execution of the target. Note how the token
28891 associated with the stop message is the one for the execution command
28892 that has been interrupted. The token for the interrupt itself only
28893 appears in the @samp{^done} output. If the user is trying to
28894 interrupt a non-running program, an error message will be printed.
28896 Note that when asynchronous execution is enabled, this command is
28897 asynchronous just like other execution commands. That is, first the
28898 @samp{^done} response will be printed, and the target stop will be
28899 reported after that using the @samp{*stopped} notification.
28901 In non-stop mode, only the context thread is interrupted by default.
28902 All threads (in all inferiors) will be interrupted if the
28903 @samp{--all} option is specified. If the @samp{--thread-group}
28904 option is specified, all threads in that group will be interrupted.
28906 @subsubheading @value{GDBN} Command
28908 The corresponding @value{GDBN} command is @samp{interrupt}.
28910 @subsubheading Example
28921 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28922 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28923 fullname="/home/foo/bar/try.c",line="13"@}
28928 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28932 @subheading The @code{-exec-jump} Command
28935 @subsubheading Synopsis
28938 -exec-jump @var{location}
28941 Resumes execution of the inferior program at the location specified by
28942 parameter. @xref{Specify Location}, for a description of the
28943 different forms of @var{location}.
28945 @subsubheading @value{GDBN} Command
28947 The corresponding @value{GDBN} command is @samp{jump}.
28949 @subsubheading Example
28952 -exec-jump foo.c:10
28953 *running,thread-id="all"
28958 @subheading The @code{-exec-next} Command
28961 @subsubheading Synopsis
28964 -exec-next [--reverse]
28967 Resumes execution of the inferior program, stopping when the beginning
28968 of the next source line is reached.
28970 If the @samp{--reverse} option is specified, resumes reverse execution
28971 of the inferior program, stopping at the beginning of the previous
28972 source line. If you issue this command on the first line of a
28973 function, it will take you back to the caller of that function, to the
28974 source line where the function was called.
28977 @subsubheading @value{GDBN} Command
28979 The corresponding @value{GDBN} command is @samp{next}.
28981 @subsubheading Example
28987 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28992 @subheading The @code{-exec-next-instruction} Command
28993 @findex -exec-next-instruction
28995 @subsubheading Synopsis
28998 -exec-next-instruction [--reverse]
29001 Executes one machine instruction. If the instruction is a function
29002 call, continues until the function returns. If the program stops at an
29003 instruction in the middle of a source line, the address will be
29006 If the @samp{--reverse} option is specified, resumes reverse execution
29007 of the inferior program, stopping at the previous instruction. If the
29008 previously executed instruction was a return from another function,
29009 it will continue to execute in reverse until the call to that function
29010 (from the current stack frame) is reached.
29012 @subsubheading @value{GDBN} Command
29014 The corresponding @value{GDBN} command is @samp{nexti}.
29016 @subsubheading Example
29020 -exec-next-instruction
29024 *stopped,reason="end-stepping-range",
29025 addr="0x000100d4",line="5",file="hello.c"
29030 @subheading The @code{-exec-return} Command
29031 @findex -exec-return
29033 @subsubheading Synopsis
29039 Makes current function return immediately. Doesn't execute the inferior.
29040 Displays the new current frame.
29042 @subsubheading @value{GDBN} Command
29044 The corresponding @value{GDBN} command is @samp{return}.
29046 @subsubheading Example
29050 200-break-insert callee4
29051 200^done,bkpt=@{number="1",addr="0x00010734",
29052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29057 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29058 frame=@{func="callee4",args=[],
29059 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29060 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29066 111^done,frame=@{level="0",func="callee3",
29067 args=[@{name="strarg",
29068 value="0x11940 \"A string argument.\""@}],
29069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29075 @subheading The @code{-exec-run} Command
29078 @subsubheading Synopsis
29081 -exec-run [ --all | --thread-group N ] [ --start ]
29084 Starts execution of the inferior from the beginning. The inferior
29085 executes until either a breakpoint is encountered or the program
29086 exits. In the latter case the output will include an exit code, if
29087 the program has exited exceptionally.
29089 When neither the @samp{--all} nor the @samp{--thread-group} option
29090 is specified, the current inferior is started. If the
29091 @samp{--thread-group} option is specified, it should refer to a thread
29092 group of type @samp{process}, and that thread group will be started.
29093 If the @samp{--all} option is specified, then all inferiors will be started.
29095 Using the @samp{--start} option instructs the debugger to stop
29096 the execution at the start of the inferior's main subprogram,
29097 following the same behavior as the @code{start} command
29098 (@pxref{Starting}).
29100 @subsubheading @value{GDBN} Command
29102 The corresponding @value{GDBN} command is @samp{run}.
29104 @subsubheading Examples
29109 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29114 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29115 frame=@{func="main",args=[],file="recursive2.c",
29116 fullname="/home/foo/bar/recursive2.c",line="4"@}
29121 Program exited normally:
29129 *stopped,reason="exited-normally"
29134 Program exited exceptionally:
29142 *stopped,reason="exited",exit-code="01"
29146 Another way the program can terminate is if it receives a signal such as
29147 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29151 *stopped,reason="exited-signalled",signal-name="SIGINT",
29152 signal-meaning="Interrupt"
29156 @c @subheading -exec-signal
29159 @subheading The @code{-exec-step} Command
29162 @subsubheading Synopsis
29165 -exec-step [--reverse]
29168 Resumes execution of the inferior program, stopping when the beginning
29169 of the next source line is reached, if the next source line is not a
29170 function call. If it is, stop at the first instruction of the called
29171 function. If the @samp{--reverse} option is specified, resumes reverse
29172 execution of the inferior program, stopping at the beginning of the
29173 previously executed source line.
29175 @subsubheading @value{GDBN} Command
29177 The corresponding @value{GDBN} command is @samp{step}.
29179 @subsubheading Example
29181 Stepping into a function:
29187 *stopped,reason="end-stepping-range",
29188 frame=@{func="foo",args=[@{name="a",value="10"@},
29189 @{name="b",value="0"@}],file="recursive2.c",
29190 fullname="/home/foo/bar/recursive2.c",line="11"@}
29200 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29205 @subheading The @code{-exec-step-instruction} Command
29206 @findex -exec-step-instruction
29208 @subsubheading Synopsis
29211 -exec-step-instruction [--reverse]
29214 Resumes the inferior which executes one machine instruction. If the
29215 @samp{--reverse} option is specified, resumes reverse execution of the
29216 inferior program, stopping at the previously executed instruction.
29217 The output, once @value{GDBN} has stopped, will vary depending on
29218 whether we have stopped in the middle of a source line or not. In the
29219 former case, the address at which the program stopped will be printed
29222 @subsubheading @value{GDBN} Command
29224 The corresponding @value{GDBN} command is @samp{stepi}.
29226 @subsubheading Example
29230 -exec-step-instruction
29234 *stopped,reason="end-stepping-range",
29235 frame=@{func="foo",args=[],file="try.c",
29236 fullname="/home/foo/bar/try.c",line="10"@}
29238 -exec-step-instruction
29242 *stopped,reason="end-stepping-range",
29243 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29244 fullname="/home/foo/bar/try.c",line="10"@}
29249 @subheading The @code{-exec-until} Command
29250 @findex -exec-until
29252 @subsubheading Synopsis
29255 -exec-until [ @var{location} ]
29258 Executes the inferior until the @var{location} specified in the
29259 argument is reached. If there is no argument, the inferior executes
29260 until a source line greater than the current one is reached. The
29261 reason for stopping in this case will be @samp{location-reached}.
29263 @subsubheading @value{GDBN} Command
29265 The corresponding @value{GDBN} command is @samp{until}.
29267 @subsubheading Example
29271 -exec-until recursive2.c:6
29275 *stopped,reason="location-reached",frame=@{func="main",args=[],
29276 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29281 @subheading -file-clear
29282 Is this going away????
29285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29286 @node GDB/MI Stack Manipulation
29287 @section @sc{gdb/mi} Stack Manipulation Commands
29289 @subheading The @code{-enable-frame-filters} Command
29290 @findex -enable-frame-filters
29293 -enable-frame-filters
29296 @value{GDBN} allows Python-based frame filters to affect the output of
29297 the MI commands relating to stack traces. As there is no way to
29298 implement this in a fully backward-compatible way, a front end must
29299 request that this functionality be enabled.
29301 Once enabled, this feature cannot be disabled.
29303 Note that if Python support has not been compiled into @value{GDBN},
29304 this command will still succeed (and do nothing).
29306 @subheading The @code{-stack-info-frame} Command
29307 @findex -stack-info-frame
29309 @subsubheading Synopsis
29315 Get info on the selected frame.
29317 @subsubheading @value{GDBN} Command
29319 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29320 (without arguments).
29322 @subsubheading Example
29327 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29328 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29329 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29333 @subheading The @code{-stack-info-depth} Command
29334 @findex -stack-info-depth
29336 @subsubheading Synopsis
29339 -stack-info-depth [ @var{max-depth} ]
29342 Return the depth of the stack. If the integer argument @var{max-depth}
29343 is specified, do not count beyond @var{max-depth} frames.
29345 @subsubheading @value{GDBN} Command
29347 There's no equivalent @value{GDBN} command.
29349 @subsubheading Example
29351 For a stack with frame levels 0 through 11:
29358 -stack-info-depth 4
29361 -stack-info-depth 12
29364 -stack-info-depth 11
29367 -stack-info-depth 13
29372 @anchor{-stack-list-arguments}
29373 @subheading The @code{-stack-list-arguments} Command
29374 @findex -stack-list-arguments
29376 @subsubheading Synopsis
29379 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29380 [ @var{low-frame} @var{high-frame} ]
29383 Display a list of the arguments for the frames between @var{low-frame}
29384 and @var{high-frame} (inclusive). If @var{low-frame} and
29385 @var{high-frame} are not provided, list the arguments for the whole
29386 call stack. If the two arguments are equal, show the single frame
29387 at the corresponding level. It is an error if @var{low-frame} is
29388 larger than the actual number of frames. On the other hand,
29389 @var{high-frame} may be larger than the actual number of frames, in
29390 which case only existing frames will be returned.
29392 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29393 the variables; if it is 1 or @code{--all-values}, print also their
29394 values; and if it is 2 or @code{--simple-values}, print the name,
29395 type and value for simple data types, and the name and type for arrays,
29396 structures and unions. If the option @code{--no-frame-filters} is
29397 supplied, then Python frame filters will not be executed.
29399 If the @code{--skip-unavailable} option is specified, arguments that
29400 are not available are not listed. Partially available arguments
29401 are still displayed, however.
29403 Use of this command to obtain arguments in a single frame is
29404 deprecated in favor of the @samp{-stack-list-variables} command.
29406 @subsubheading @value{GDBN} Command
29408 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29409 @samp{gdb_get_args} command which partially overlaps with the
29410 functionality of @samp{-stack-list-arguments}.
29412 @subsubheading Example
29419 frame=@{level="0",addr="0x00010734",func="callee4",
29420 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29421 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29422 frame=@{level="1",addr="0x0001076c",func="callee3",
29423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29424 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29425 frame=@{level="2",addr="0x0001078c",func="callee2",
29426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29428 frame=@{level="3",addr="0x000107b4",func="callee1",
29429 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29430 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29431 frame=@{level="4",addr="0x000107e0",func="main",
29432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29433 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29435 -stack-list-arguments 0
29438 frame=@{level="0",args=[]@},
29439 frame=@{level="1",args=[name="strarg"]@},
29440 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29441 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29442 frame=@{level="4",args=[]@}]
29444 -stack-list-arguments 1
29447 frame=@{level="0",args=[]@},
29449 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29450 frame=@{level="2",args=[
29451 @{name="intarg",value="2"@},
29452 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29453 @{frame=@{level="3",args=[
29454 @{name="intarg",value="2"@},
29455 @{name="strarg",value="0x11940 \"A string argument.\""@},
29456 @{name="fltarg",value="3.5"@}]@},
29457 frame=@{level="4",args=[]@}]
29459 -stack-list-arguments 0 2 2
29460 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29462 -stack-list-arguments 1 2 2
29463 ^done,stack-args=[frame=@{level="2",
29464 args=[@{name="intarg",value="2"@},
29465 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29469 @c @subheading -stack-list-exception-handlers
29472 @anchor{-stack-list-frames}
29473 @subheading The @code{-stack-list-frames} Command
29474 @findex -stack-list-frames
29476 @subsubheading Synopsis
29479 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29482 List the frames currently on the stack. For each frame it displays the
29487 The frame number, 0 being the topmost frame, i.e., the innermost function.
29489 The @code{$pc} value for that frame.
29493 File name of the source file where the function lives.
29494 @item @var{fullname}
29495 The full file name of the source file where the function lives.
29497 Line number corresponding to the @code{$pc}.
29499 The shared library where this function is defined. This is only given
29500 if the frame's function is not known.
29503 If invoked without arguments, this command prints a backtrace for the
29504 whole stack. If given two integer arguments, it shows the frames whose
29505 levels are between the two arguments (inclusive). If the two arguments
29506 are equal, it shows the single frame at the corresponding level. It is
29507 an error if @var{low-frame} is larger than the actual number of
29508 frames. On the other hand, @var{high-frame} may be larger than the
29509 actual number of frames, in which case only existing frames will be
29510 returned. If the option @code{--no-frame-filters} is supplied, then
29511 Python frame filters will not be executed.
29513 @subsubheading @value{GDBN} Command
29515 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29517 @subsubheading Example
29519 Full stack backtrace:
29525 [frame=@{level="0",addr="0x0001076c",func="foo",
29526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29527 frame=@{level="1",addr="0x000107a4",func="foo",
29528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29529 frame=@{level="2",addr="0x000107a4",func="foo",
29530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29531 frame=@{level="3",addr="0x000107a4",func="foo",
29532 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29533 frame=@{level="4",addr="0x000107a4",func="foo",
29534 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29535 frame=@{level="5",addr="0x000107a4",func="foo",
29536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29537 frame=@{level="6",addr="0x000107a4",func="foo",
29538 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29539 frame=@{level="7",addr="0x000107a4",func="foo",
29540 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29541 frame=@{level="8",addr="0x000107a4",func="foo",
29542 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29543 frame=@{level="9",addr="0x000107a4",func="foo",
29544 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29545 frame=@{level="10",addr="0x000107a4",func="foo",
29546 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29547 frame=@{level="11",addr="0x00010738",func="main",
29548 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29552 Show frames between @var{low_frame} and @var{high_frame}:
29556 -stack-list-frames 3 5
29558 [frame=@{level="3",addr="0x000107a4",func="foo",
29559 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29560 frame=@{level="4",addr="0x000107a4",func="foo",
29561 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29562 frame=@{level="5",addr="0x000107a4",func="foo",
29563 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29567 Show a single frame:
29571 -stack-list-frames 3 3
29573 [frame=@{level="3",addr="0x000107a4",func="foo",
29574 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29579 @subheading The @code{-stack-list-locals} Command
29580 @findex -stack-list-locals
29581 @anchor{-stack-list-locals}
29583 @subsubheading Synopsis
29586 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29589 Display the local variable names for the selected frame. If
29590 @var{print-values} is 0 or @code{--no-values}, print only the names of
29591 the variables; if it is 1 or @code{--all-values}, print also their
29592 values; and if it is 2 or @code{--simple-values}, print the name,
29593 type and value for simple data types, and the name and type for arrays,
29594 structures and unions. In this last case, a frontend can immediately
29595 display the value of simple data types and create variable objects for
29596 other data types when the user wishes to explore their values in
29597 more detail. If the option @code{--no-frame-filters} is supplied, then
29598 Python frame filters will not be executed.
29600 If the @code{--skip-unavailable} option is specified, local variables
29601 that are not available are not listed. Partially available local
29602 variables are still displayed, however.
29604 This command is deprecated in favor of the
29605 @samp{-stack-list-variables} command.
29607 @subsubheading @value{GDBN} Command
29609 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29611 @subsubheading Example
29615 -stack-list-locals 0
29616 ^done,locals=[name="A",name="B",name="C"]
29618 -stack-list-locals --all-values
29619 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29620 @{name="C",value="@{1, 2, 3@}"@}]
29621 -stack-list-locals --simple-values
29622 ^done,locals=[@{name="A",type="int",value="1"@},
29623 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29627 @anchor{-stack-list-variables}
29628 @subheading The @code{-stack-list-variables} Command
29629 @findex -stack-list-variables
29631 @subsubheading Synopsis
29634 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29637 Display the names of local variables and function arguments for the selected frame. If
29638 @var{print-values} is 0 or @code{--no-values}, print only the names of
29639 the variables; if it is 1 or @code{--all-values}, print also their
29640 values; and if it is 2 or @code{--simple-values}, print the name,
29641 type and value for simple data types, and the name and type for arrays,
29642 structures and unions. If the option @code{--no-frame-filters} is
29643 supplied, then Python frame filters will not be executed.
29645 If the @code{--skip-unavailable} option is specified, local variables
29646 and arguments that are not available are not listed. Partially
29647 available arguments and local variables are still displayed, however.
29649 @subsubheading Example
29653 -stack-list-variables --thread 1 --frame 0 --all-values
29654 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29659 @subheading The @code{-stack-select-frame} Command
29660 @findex -stack-select-frame
29662 @subsubheading Synopsis
29665 -stack-select-frame @var{framenum}
29668 Change the selected frame. Select a different frame @var{framenum} on
29671 This command in deprecated in favor of passing the @samp{--frame}
29672 option to every command.
29674 @subsubheading @value{GDBN} Command
29676 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29677 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29679 @subsubheading Example
29683 -stack-select-frame 2
29688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29689 @node GDB/MI Variable Objects
29690 @section @sc{gdb/mi} Variable Objects
29694 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29696 For the implementation of a variable debugger window (locals, watched
29697 expressions, etc.), we are proposing the adaptation of the existing code
29698 used by @code{Insight}.
29700 The two main reasons for that are:
29704 It has been proven in practice (it is already on its second generation).
29707 It will shorten development time (needless to say how important it is
29711 The original interface was designed to be used by Tcl code, so it was
29712 slightly changed so it could be used through @sc{gdb/mi}. This section
29713 describes the @sc{gdb/mi} operations that will be available and gives some
29714 hints about their use.
29716 @emph{Note}: In addition to the set of operations described here, we
29717 expect the @sc{gui} implementation of a variable window to require, at
29718 least, the following operations:
29721 @item @code{-gdb-show} @code{output-radix}
29722 @item @code{-stack-list-arguments}
29723 @item @code{-stack-list-locals}
29724 @item @code{-stack-select-frame}
29729 @subheading Introduction to Variable Objects
29731 @cindex variable objects in @sc{gdb/mi}
29733 Variable objects are "object-oriented" MI interface for examining and
29734 changing values of expressions. Unlike some other MI interfaces that
29735 work with expressions, variable objects are specifically designed for
29736 simple and efficient presentation in the frontend. A variable object
29737 is identified by string name. When a variable object is created, the
29738 frontend specifies the expression for that variable object. The
29739 expression can be a simple variable, or it can be an arbitrary complex
29740 expression, and can even involve CPU registers. After creating a
29741 variable object, the frontend can invoke other variable object
29742 operations---for example to obtain or change the value of a variable
29743 object, or to change display format.
29745 Variable objects have hierarchical tree structure. Any variable object
29746 that corresponds to a composite type, such as structure in C, has
29747 a number of child variable objects, for example corresponding to each
29748 element of a structure. A child variable object can itself have
29749 children, recursively. Recursion ends when we reach
29750 leaf variable objects, which always have built-in types. Child variable
29751 objects are created only by explicit request, so if a frontend
29752 is not interested in the children of a particular variable object, no
29753 child will be created.
29755 For a leaf variable object it is possible to obtain its value as a
29756 string, or set the value from a string. String value can be also
29757 obtained for a non-leaf variable object, but it's generally a string
29758 that only indicates the type of the object, and does not list its
29759 contents. Assignment to a non-leaf variable object is not allowed.
29761 A frontend does not need to read the values of all variable objects each time
29762 the program stops. Instead, MI provides an update command that lists all
29763 variable objects whose values has changed since the last update
29764 operation. This considerably reduces the amount of data that must
29765 be transferred to the frontend. As noted above, children variable
29766 objects are created on demand, and only leaf variable objects have a
29767 real value. As result, gdb will read target memory only for leaf
29768 variables that frontend has created.
29770 The automatic update is not always desirable. For example, a frontend
29771 might want to keep a value of some expression for future reference,
29772 and never update it. For another example, fetching memory is
29773 relatively slow for embedded targets, so a frontend might want
29774 to disable automatic update for the variables that are either not
29775 visible on the screen, or ``closed''. This is possible using so
29776 called ``frozen variable objects''. Such variable objects are never
29777 implicitly updated.
29779 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29780 fixed variable object, the expression is parsed when the variable
29781 object is created, including associating identifiers to specific
29782 variables. The meaning of expression never changes. For a floating
29783 variable object the values of variables whose names appear in the
29784 expressions are re-evaluated every time in the context of the current
29785 frame. Consider this example:
29790 struct work_state state;
29797 If a fixed variable object for the @code{state} variable is created in
29798 this function, and we enter the recursive call, the variable
29799 object will report the value of @code{state} in the top-level
29800 @code{do_work} invocation. On the other hand, a floating variable
29801 object will report the value of @code{state} in the current frame.
29803 If an expression specified when creating a fixed variable object
29804 refers to a local variable, the variable object becomes bound to the
29805 thread and frame in which the variable object is created. When such
29806 variable object is updated, @value{GDBN} makes sure that the
29807 thread/frame combination the variable object is bound to still exists,
29808 and re-evaluates the variable object in context of that thread/frame.
29810 The following is the complete set of @sc{gdb/mi} operations defined to
29811 access this functionality:
29813 @multitable @columnfractions .4 .6
29814 @item @strong{Operation}
29815 @tab @strong{Description}
29817 @item @code{-enable-pretty-printing}
29818 @tab enable Python-based pretty-printing
29819 @item @code{-var-create}
29820 @tab create a variable object
29821 @item @code{-var-delete}
29822 @tab delete the variable object and/or its children
29823 @item @code{-var-set-format}
29824 @tab set the display format of this variable
29825 @item @code{-var-show-format}
29826 @tab show the display format of this variable
29827 @item @code{-var-info-num-children}
29828 @tab tells how many children this object has
29829 @item @code{-var-list-children}
29830 @tab return a list of the object's children
29831 @item @code{-var-info-type}
29832 @tab show the type of this variable object
29833 @item @code{-var-info-expression}
29834 @tab print parent-relative expression that this variable object represents
29835 @item @code{-var-info-path-expression}
29836 @tab print full expression that this variable object represents
29837 @item @code{-var-show-attributes}
29838 @tab is this variable editable? does it exist here?
29839 @item @code{-var-evaluate-expression}
29840 @tab get the value of this variable
29841 @item @code{-var-assign}
29842 @tab set the value of this variable
29843 @item @code{-var-update}
29844 @tab update the variable and its children
29845 @item @code{-var-set-frozen}
29846 @tab set frozeness attribute
29847 @item @code{-var-set-update-range}
29848 @tab set range of children to display on update
29851 In the next subsection we describe each operation in detail and suggest
29852 how it can be used.
29854 @subheading Description And Use of Operations on Variable Objects
29856 @subheading The @code{-enable-pretty-printing} Command
29857 @findex -enable-pretty-printing
29860 -enable-pretty-printing
29863 @value{GDBN} allows Python-based visualizers to affect the output of the
29864 MI variable object commands. However, because there was no way to
29865 implement this in a fully backward-compatible way, a front end must
29866 request that this functionality be enabled.
29868 Once enabled, this feature cannot be disabled.
29870 Note that if Python support has not been compiled into @value{GDBN},
29871 this command will still succeed (and do nothing).
29873 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29874 may work differently in future versions of @value{GDBN}.
29876 @subheading The @code{-var-create} Command
29877 @findex -var-create
29879 @subsubheading Synopsis
29882 -var-create @{@var{name} | "-"@}
29883 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29886 This operation creates a variable object, which allows the monitoring of
29887 a variable, the result of an expression, a memory cell or a CPU
29890 The @var{name} parameter is the string by which the object can be
29891 referenced. It must be unique. If @samp{-} is specified, the varobj
29892 system will generate a string ``varNNNNNN'' automatically. It will be
29893 unique provided that one does not specify @var{name} of that format.
29894 The command fails if a duplicate name is found.
29896 The frame under which the expression should be evaluated can be
29897 specified by @var{frame-addr}. A @samp{*} indicates that the current
29898 frame should be used. A @samp{@@} indicates that a floating variable
29899 object must be created.
29901 @var{expression} is any expression valid on the current language set (must not
29902 begin with a @samp{*}), or one of the following:
29906 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29909 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29912 @samp{$@var{regname}} --- a CPU register name
29915 @cindex dynamic varobj
29916 A varobj's contents may be provided by a Python-based pretty-printer. In this
29917 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29918 have slightly different semantics in some cases. If the
29919 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29920 will never create a dynamic varobj. This ensures backward
29921 compatibility for existing clients.
29923 @subsubheading Result
29925 This operation returns attributes of the newly-created varobj. These
29930 The name of the varobj.
29933 The number of children of the varobj. This number is not necessarily
29934 reliable for a dynamic varobj. Instead, you must examine the
29935 @samp{has_more} attribute.
29938 The varobj's scalar value. For a varobj whose type is some sort of
29939 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29940 will not be interesting.
29943 The varobj's type. This is a string representation of the type, as
29944 would be printed by the @value{GDBN} CLI. If @samp{print object}
29945 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29946 @emph{actual} (derived) type of the object is shown rather than the
29947 @emph{declared} one.
29950 If a variable object is bound to a specific thread, then this is the
29951 thread's global identifier.
29954 For a dynamic varobj, this indicates whether there appear to be any
29955 children available. For a non-dynamic varobj, this will be 0.
29958 This attribute will be present and have the value @samp{1} if the
29959 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29960 then this attribute will not be present.
29963 A dynamic varobj can supply a display hint to the front end. The
29964 value comes directly from the Python pretty-printer object's
29965 @code{display_hint} method. @xref{Pretty Printing API}.
29968 Typical output will look like this:
29971 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29972 has_more="@var{has_more}"
29976 @subheading The @code{-var-delete} Command
29977 @findex -var-delete
29979 @subsubheading Synopsis
29982 -var-delete [ -c ] @var{name}
29985 Deletes a previously created variable object and all of its children.
29986 With the @samp{-c} option, just deletes the children.
29988 Returns an error if the object @var{name} is not found.
29991 @subheading The @code{-var-set-format} Command
29992 @findex -var-set-format
29994 @subsubheading Synopsis
29997 -var-set-format @var{name} @var{format-spec}
30000 Sets the output format for the value of the object @var{name} to be
30003 @anchor{-var-set-format}
30004 The syntax for the @var{format-spec} is as follows:
30007 @var{format-spec} @expansion{}
30008 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30011 The natural format is the default format choosen automatically
30012 based on the variable type (like decimal for an @code{int}, hex
30013 for pointers, etc.).
30015 The zero-hexadecimal format has a representation similar to hexadecimal
30016 but with padding zeroes to the left of the value. For example, a 32-bit
30017 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30018 zero-hexadecimal format.
30020 For a variable with children, the format is set only on the
30021 variable itself, and the children are not affected.
30023 @subheading The @code{-var-show-format} Command
30024 @findex -var-show-format
30026 @subsubheading Synopsis
30029 -var-show-format @var{name}
30032 Returns the format used to display the value of the object @var{name}.
30035 @var{format} @expansion{}
30040 @subheading The @code{-var-info-num-children} Command
30041 @findex -var-info-num-children
30043 @subsubheading Synopsis
30046 -var-info-num-children @var{name}
30049 Returns the number of children of a variable object @var{name}:
30055 Note that this number is not completely reliable for a dynamic varobj.
30056 It will return the current number of children, but more children may
30060 @subheading The @code{-var-list-children} Command
30061 @findex -var-list-children
30063 @subsubheading Synopsis
30066 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30068 @anchor{-var-list-children}
30070 Return a list of the children of the specified variable object and
30071 create variable objects for them, if they do not already exist. With
30072 a single argument or if @var{print-values} has a value of 0 or
30073 @code{--no-values}, print only the names of the variables; if
30074 @var{print-values} is 1 or @code{--all-values}, also print their
30075 values; and if it is 2 or @code{--simple-values} print the name and
30076 value for simple data types and just the name for arrays, structures
30079 @var{from} and @var{to}, if specified, indicate the range of children
30080 to report. If @var{from} or @var{to} is less than zero, the range is
30081 reset and all children will be reported. Otherwise, children starting
30082 at @var{from} (zero-based) and up to and excluding @var{to} will be
30085 If a child range is requested, it will only affect the current call to
30086 @code{-var-list-children}, but not future calls to @code{-var-update}.
30087 For this, you must instead use @code{-var-set-update-range}. The
30088 intent of this approach is to enable a front end to implement any
30089 update approach it likes; for example, scrolling a view may cause the
30090 front end to request more children with @code{-var-list-children}, and
30091 then the front end could call @code{-var-set-update-range} with a
30092 different range to ensure that future updates are restricted to just
30095 For each child the following results are returned:
30100 Name of the variable object created for this child.
30103 The expression to be shown to the user by the front end to designate this child.
30104 For example this may be the name of a structure member.
30106 For a dynamic varobj, this value cannot be used to form an
30107 expression. There is no way to do this at all with a dynamic varobj.
30109 For C/C@t{++} structures there are several pseudo children returned to
30110 designate access qualifiers. For these pseudo children @var{exp} is
30111 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30112 type and value are not present.
30114 A dynamic varobj will not report the access qualifying
30115 pseudo-children, regardless of the language. This information is not
30116 available at all with a dynamic varobj.
30119 Number of children this child has. For a dynamic varobj, this will be
30123 The type of the child. If @samp{print object}
30124 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30125 @emph{actual} (derived) type of the object is shown rather than the
30126 @emph{declared} one.
30129 If values were requested, this is the value.
30132 If this variable object is associated with a thread, this is the
30133 thread's global thread id. Otherwise this result is not present.
30136 If the variable object is frozen, this variable will be present with a value of 1.
30139 A dynamic varobj can supply a display hint to the front end. The
30140 value comes directly from the Python pretty-printer object's
30141 @code{display_hint} method. @xref{Pretty Printing API}.
30144 This attribute will be present and have the value @samp{1} if the
30145 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30146 then this attribute will not be present.
30150 The result may have its own attributes:
30154 A dynamic varobj can supply a display hint to the front end. The
30155 value comes directly from the Python pretty-printer object's
30156 @code{display_hint} method. @xref{Pretty Printing API}.
30159 This is an integer attribute which is nonzero if there are children
30160 remaining after the end of the selected range.
30163 @subsubheading Example
30167 -var-list-children n
30168 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30169 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30171 -var-list-children --all-values n
30172 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30173 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30177 @subheading The @code{-var-info-type} Command
30178 @findex -var-info-type
30180 @subsubheading Synopsis
30183 -var-info-type @var{name}
30186 Returns the type of the specified variable @var{name}. The type is
30187 returned as a string in the same format as it is output by the
30191 type=@var{typename}
30195 @subheading The @code{-var-info-expression} Command
30196 @findex -var-info-expression
30198 @subsubheading Synopsis
30201 -var-info-expression @var{name}
30204 Returns a string that is suitable for presenting this
30205 variable object in user interface. The string is generally
30206 not valid expression in the current language, and cannot be evaluated.
30208 For example, if @code{a} is an array, and variable object
30209 @code{A} was created for @code{a}, then we'll get this output:
30212 (gdb) -var-info-expression A.1
30213 ^done,lang="C",exp="1"
30217 Here, the value of @code{lang} is the language name, which can be
30218 found in @ref{Supported Languages}.
30220 Note that the output of the @code{-var-list-children} command also
30221 includes those expressions, so the @code{-var-info-expression} command
30224 @subheading The @code{-var-info-path-expression} Command
30225 @findex -var-info-path-expression
30227 @subsubheading Synopsis
30230 -var-info-path-expression @var{name}
30233 Returns an expression that can be evaluated in the current
30234 context and will yield the same value that a variable object has.
30235 Compare this with the @code{-var-info-expression} command, which
30236 result can be used only for UI presentation. Typical use of
30237 the @code{-var-info-path-expression} command is creating a
30238 watchpoint from a variable object.
30240 This command is currently not valid for children of a dynamic varobj,
30241 and will give an error when invoked on one.
30243 For example, suppose @code{C} is a C@t{++} class, derived from class
30244 @code{Base}, and that the @code{Base} class has a member called
30245 @code{m_size}. Assume a variable @code{c} is has the type of
30246 @code{C} and a variable object @code{C} was created for variable
30247 @code{c}. Then, we'll get this output:
30249 (gdb) -var-info-path-expression C.Base.public.m_size
30250 ^done,path_expr=((Base)c).m_size)
30253 @subheading The @code{-var-show-attributes} Command
30254 @findex -var-show-attributes
30256 @subsubheading Synopsis
30259 -var-show-attributes @var{name}
30262 List attributes of the specified variable object @var{name}:
30265 status=@var{attr} [ ( ,@var{attr} )* ]
30269 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30271 @subheading The @code{-var-evaluate-expression} Command
30272 @findex -var-evaluate-expression
30274 @subsubheading Synopsis
30277 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30280 Evaluates the expression that is represented by the specified variable
30281 object and returns its value as a string. The format of the string
30282 can be specified with the @samp{-f} option. The possible values of
30283 this option are the same as for @code{-var-set-format}
30284 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30285 the current display format will be used. The current display format
30286 can be changed using the @code{-var-set-format} command.
30292 Note that one must invoke @code{-var-list-children} for a variable
30293 before the value of a child variable can be evaluated.
30295 @subheading The @code{-var-assign} Command
30296 @findex -var-assign
30298 @subsubheading Synopsis
30301 -var-assign @var{name} @var{expression}
30304 Assigns the value of @var{expression} to the variable object specified
30305 by @var{name}. The object must be @samp{editable}. If the variable's
30306 value is altered by the assign, the variable will show up in any
30307 subsequent @code{-var-update} list.
30309 @subsubheading Example
30317 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30321 @subheading The @code{-var-update} Command
30322 @findex -var-update
30324 @subsubheading Synopsis
30327 -var-update [@var{print-values}] @{@var{name} | "*"@}
30330 Reevaluate the expressions corresponding to the variable object
30331 @var{name} and all its direct and indirect children, and return the
30332 list of variable objects whose values have changed; @var{name} must
30333 be a root variable object. Here, ``changed'' means that the result of
30334 @code{-var-evaluate-expression} before and after the
30335 @code{-var-update} is different. If @samp{*} is used as the variable
30336 object names, all existing variable objects are updated, except
30337 for frozen ones (@pxref{-var-set-frozen}). The option
30338 @var{print-values} determines whether both names and values, or just
30339 names are printed. The possible values of this option are the same
30340 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30341 recommended to use the @samp{--all-values} option, to reduce the
30342 number of MI commands needed on each program stop.
30344 With the @samp{*} parameter, if a variable object is bound to a
30345 currently running thread, it will not be updated, without any
30348 If @code{-var-set-update-range} was previously used on a varobj, then
30349 only the selected range of children will be reported.
30351 @code{-var-update} reports all the changed varobjs in a tuple named
30354 Each item in the change list is itself a tuple holding:
30358 The name of the varobj.
30361 If values were requested for this update, then this field will be
30362 present and will hold the value of the varobj.
30365 @anchor{-var-update}
30366 This field is a string which may take one of three values:
30370 The variable object's current value is valid.
30373 The variable object does not currently hold a valid value but it may
30374 hold one in the future if its associated expression comes back into
30378 The variable object no longer holds a valid value.
30379 This can occur when the executable file being debugged has changed,
30380 either through recompilation or by using the @value{GDBN} @code{file}
30381 command. The front end should normally choose to delete these variable
30385 In the future new values may be added to this list so the front should
30386 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30389 This is only present if the varobj is still valid. If the type
30390 changed, then this will be the string @samp{true}; otherwise it will
30393 When a varobj's type changes, its children are also likely to have
30394 become incorrect. Therefore, the varobj's children are automatically
30395 deleted when this attribute is @samp{true}. Also, the varobj's update
30396 range, when set using the @code{-var-set-update-range} command, is
30400 If the varobj's type changed, then this field will be present and will
30403 @item new_num_children
30404 For a dynamic varobj, if the number of children changed, or if the
30405 type changed, this will be the new number of children.
30407 The @samp{numchild} field in other varobj responses is generally not
30408 valid for a dynamic varobj -- it will show the number of children that
30409 @value{GDBN} knows about, but because dynamic varobjs lazily
30410 instantiate their children, this will not reflect the number of
30411 children which may be available.
30413 The @samp{new_num_children} attribute only reports changes to the
30414 number of children known by @value{GDBN}. This is the only way to
30415 detect whether an update has removed children (which necessarily can
30416 only happen at the end of the update range).
30419 The display hint, if any.
30422 This is an integer value, which will be 1 if there are more children
30423 available outside the varobj's update range.
30426 This attribute will be present and have the value @samp{1} if the
30427 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30428 then this attribute will not be present.
30431 If new children were added to a dynamic varobj within the selected
30432 update range (as set by @code{-var-set-update-range}), then they will
30433 be listed in this attribute.
30436 @subsubheading Example
30443 -var-update --all-values var1
30444 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30445 type_changed="false"@}]
30449 @subheading The @code{-var-set-frozen} Command
30450 @findex -var-set-frozen
30451 @anchor{-var-set-frozen}
30453 @subsubheading Synopsis
30456 -var-set-frozen @var{name} @var{flag}
30459 Set the frozenness flag on the variable object @var{name}. The
30460 @var{flag} parameter should be either @samp{1} to make the variable
30461 frozen or @samp{0} to make it unfrozen. If a variable object is
30462 frozen, then neither itself, nor any of its children, are
30463 implicitly updated by @code{-var-update} of
30464 a parent variable or by @code{-var-update *}. Only
30465 @code{-var-update} of the variable itself will update its value and
30466 values of its children. After a variable object is unfrozen, it is
30467 implicitly updated by all subsequent @code{-var-update} operations.
30468 Unfreezing a variable does not update it, only subsequent
30469 @code{-var-update} does.
30471 @subsubheading Example
30475 -var-set-frozen V 1
30480 @subheading The @code{-var-set-update-range} command
30481 @findex -var-set-update-range
30482 @anchor{-var-set-update-range}
30484 @subsubheading Synopsis
30487 -var-set-update-range @var{name} @var{from} @var{to}
30490 Set the range of children to be returned by future invocations of
30491 @code{-var-update}.
30493 @var{from} and @var{to} indicate the range of children to report. If
30494 @var{from} or @var{to} is less than zero, the range is reset and all
30495 children will be reported. Otherwise, children starting at @var{from}
30496 (zero-based) and up to and excluding @var{to} will be reported.
30498 @subsubheading Example
30502 -var-set-update-range V 1 2
30506 @subheading The @code{-var-set-visualizer} command
30507 @findex -var-set-visualizer
30508 @anchor{-var-set-visualizer}
30510 @subsubheading Synopsis
30513 -var-set-visualizer @var{name} @var{visualizer}
30516 Set a visualizer for the variable object @var{name}.
30518 @var{visualizer} is the visualizer to use. The special value
30519 @samp{None} means to disable any visualizer in use.
30521 If not @samp{None}, @var{visualizer} must be a Python expression.
30522 This expression must evaluate to a callable object which accepts a
30523 single argument. @value{GDBN} will call this object with the value of
30524 the varobj @var{name} as an argument (this is done so that the same
30525 Python pretty-printing code can be used for both the CLI and MI).
30526 When called, this object must return an object which conforms to the
30527 pretty-printing interface (@pxref{Pretty Printing API}).
30529 The pre-defined function @code{gdb.default_visualizer} may be used to
30530 select a visualizer by following the built-in process
30531 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30532 a varobj is created, and so ordinarily is not needed.
30534 This feature is only available if Python support is enabled. The MI
30535 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30536 can be used to check this.
30538 @subsubheading Example
30540 Resetting the visualizer:
30544 -var-set-visualizer V None
30548 Reselecting the default (type-based) visualizer:
30552 -var-set-visualizer V gdb.default_visualizer
30556 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30557 can be used to instantiate this class for a varobj:
30561 -var-set-visualizer V "lambda val: SomeClass()"
30565 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30566 @node GDB/MI Data Manipulation
30567 @section @sc{gdb/mi} Data Manipulation
30569 @cindex data manipulation, in @sc{gdb/mi}
30570 @cindex @sc{gdb/mi}, data manipulation
30571 This section describes the @sc{gdb/mi} commands that manipulate data:
30572 examine memory and registers, evaluate expressions, etc.
30574 For details about what an addressable memory unit is,
30575 @pxref{addressable memory unit}.
30577 @c REMOVED FROM THE INTERFACE.
30578 @c @subheading -data-assign
30579 @c Change the value of a program variable. Plenty of side effects.
30580 @c @subsubheading GDB Command
30582 @c @subsubheading Example
30585 @subheading The @code{-data-disassemble} Command
30586 @findex -data-disassemble
30588 @subsubheading Synopsis
30592 [ -s @var{start-addr} -e @var{end-addr} ]
30593 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30601 @item @var{start-addr}
30602 is the beginning address (or @code{$pc})
30603 @item @var{end-addr}
30605 @item @var{filename}
30606 is the name of the file to disassemble
30607 @item @var{linenum}
30608 is the line number to disassemble around
30610 is the number of disassembly lines to be produced. If it is -1,
30611 the whole function will be disassembled, in case no @var{end-addr} is
30612 specified. If @var{end-addr} is specified as a non-zero value, and
30613 @var{lines} is lower than the number of disassembly lines between
30614 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30615 displayed; if @var{lines} is higher than the number of lines between
30616 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30621 @item 0 disassembly only
30622 @item 1 mixed source and disassembly (deprecated)
30623 @item 2 disassembly with raw opcodes
30624 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30625 @item 4 mixed source and disassembly
30626 @item 5 mixed source and disassembly with raw opcodes
30629 Modes 1 and 3 are deprecated. The output is ``source centric''
30630 which hasn't proved useful in practice.
30631 @xref{Machine Code}, for a discussion of the difference between
30632 @code{/m} and @code{/s} output of the @code{disassemble} command.
30635 @subsubheading Result
30637 The result of the @code{-data-disassemble} command will be a list named
30638 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30639 used with the @code{-data-disassemble} command.
30641 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30646 The address at which this instruction was disassembled.
30649 The name of the function this instruction is within.
30652 The decimal offset in bytes from the start of @samp{func-name}.
30655 The text disassembly for this @samp{address}.
30658 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30659 bytes for the @samp{inst} field.
30663 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30664 @samp{src_and_asm_line}, each of which has the following fields:
30668 The line number within @samp{file}.
30671 The file name from the compilation unit. This might be an absolute
30672 file name or a relative file name depending on the compile command
30676 Absolute file name of @samp{file}. It is converted to a canonical form
30677 using the source file search path
30678 (@pxref{Source Path, ,Specifying Source Directories})
30679 and after resolving all the symbolic links.
30681 If the source file is not found this field will contain the path as
30682 present in the debug information.
30684 @item line_asm_insn
30685 This is a list of tuples containing the disassembly for @samp{line} in
30686 @samp{file}. The fields of each tuple are the same as for
30687 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30688 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30693 Note that whatever included in the @samp{inst} field, is not
30694 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30697 @subsubheading @value{GDBN} Command
30699 The corresponding @value{GDBN} command is @samp{disassemble}.
30701 @subsubheading Example
30703 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30707 -data-disassemble -s $pc -e "$pc + 20" -- 0
30710 @{address="0x000107c0",func-name="main",offset="4",
30711 inst="mov 2, %o0"@},
30712 @{address="0x000107c4",func-name="main",offset="8",
30713 inst="sethi %hi(0x11800), %o2"@},
30714 @{address="0x000107c8",func-name="main",offset="12",
30715 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30716 @{address="0x000107cc",func-name="main",offset="16",
30717 inst="sethi %hi(0x11800), %o2"@},
30718 @{address="0x000107d0",func-name="main",offset="20",
30719 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30723 Disassemble the whole @code{main} function. Line 32 is part of
30727 -data-disassemble -f basics.c -l 32 -- 0
30729 @{address="0x000107bc",func-name="main",offset="0",
30730 inst="save %sp, -112, %sp"@},
30731 @{address="0x000107c0",func-name="main",offset="4",
30732 inst="mov 2, %o0"@},
30733 @{address="0x000107c4",func-name="main",offset="8",
30734 inst="sethi %hi(0x11800), %o2"@},
30736 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30737 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30741 Disassemble 3 instructions from the start of @code{main}:
30745 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30747 @{address="0x000107bc",func-name="main",offset="0",
30748 inst="save %sp, -112, %sp"@},
30749 @{address="0x000107c0",func-name="main",offset="4",
30750 inst="mov 2, %o0"@},
30751 @{address="0x000107c4",func-name="main",offset="8",
30752 inst="sethi %hi(0x11800), %o2"@}]
30756 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30760 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30762 src_and_asm_line=@{line="31",
30763 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30764 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30765 line_asm_insn=[@{address="0x000107bc",
30766 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30767 src_and_asm_line=@{line="32",
30768 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30769 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30770 line_asm_insn=[@{address="0x000107c0",
30771 func-name="main",offset="4",inst="mov 2, %o0"@},
30772 @{address="0x000107c4",func-name="main",offset="8",
30773 inst="sethi %hi(0x11800), %o2"@}]@}]
30778 @subheading The @code{-data-evaluate-expression} Command
30779 @findex -data-evaluate-expression
30781 @subsubheading Synopsis
30784 -data-evaluate-expression @var{expr}
30787 Evaluate @var{expr} as an expression. The expression could contain an
30788 inferior function call. The function call will execute synchronously.
30789 If the expression contains spaces, it must be enclosed in double quotes.
30791 @subsubheading @value{GDBN} Command
30793 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30794 @samp{call}. In @code{gdbtk} only, there's a corresponding
30795 @samp{gdb_eval} command.
30797 @subsubheading Example
30799 In the following example, the numbers that precede the commands are the
30800 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30801 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30805 211-data-evaluate-expression A
30808 311-data-evaluate-expression &A
30809 311^done,value="0xefffeb7c"
30811 411-data-evaluate-expression A+3
30814 511-data-evaluate-expression "A + 3"
30820 @subheading The @code{-data-list-changed-registers} Command
30821 @findex -data-list-changed-registers
30823 @subsubheading Synopsis
30826 -data-list-changed-registers
30829 Display a list of the registers that have changed.
30831 @subsubheading @value{GDBN} Command
30833 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30834 has the corresponding command @samp{gdb_changed_register_list}.
30836 @subsubheading Example
30838 On a PPC MBX board:
30846 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30847 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30850 -data-list-changed-registers
30851 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30852 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30853 "24","25","26","27","28","30","31","64","65","66","67","69"]
30858 @subheading The @code{-data-list-register-names} Command
30859 @findex -data-list-register-names
30861 @subsubheading Synopsis
30864 -data-list-register-names [ ( @var{regno} )+ ]
30867 Show a list of register names for the current target. If no arguments
30868 are given, it shows a list of the names of all the registers. If
30869 integer numbers are given as arguments, it will print a list of the
30870 names of the registers corresponding to the arguments. To ensure
30871 consistency between a register name and its number, the output list may
30872 include empty register names.
30874 @subsubheading @value{GDBN} Command
30876 @value{GDBN} does not have a command which corresponds to
30877 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30878 corresponding command @samp{gdb_regnames}.
30880 @subsubheading Example
30882 For the PPC MBX board:
30885 -data-list-register-names
30886 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30887 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30888 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30889 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30890 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30891 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30892 "", "pc","ps","cr","lr","ctr","xer"]
30894 -data-list-register-names 1 2 3
30895 ^done,register-names=["r1","r2","r3"]
30899 @subheading The @code{-data-list-register-values} Command
30900 @findex -data-list-register-values
30902 @subsubheading Synopsis
30905 -data-list-register-values
30906 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30909 Display the registers' contents. The format according to which the
30910 registers' contents are to be returned is given by @var{fmt}, followed
30911 by an optional list of numbers specifying the registers to display. A
30912 missing list of numbers indicates that the contents of all the
30913 registers must be returned. The @code{--skip-unavailable} option
30914 indicates that only the available registers are to be returned.
30916 Allowed formats for @var{fmt} are:
30933 @subsubheading @value{GDBN} Command
30935 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30936 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30938 @subsubheading Example
30940 For a PPC MBX board (note: line breaks are for readability only, they
30941 don't appear in the actual output):
30945 -data-list-register-values r 64 65
30946 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30947 @{number="65",value="0x00029002"@}]
30949 -data-list-register-values x
30950 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30951 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30952 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30953 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30954 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30955 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30956 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30957 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30958 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30959 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30960 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30961 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30962 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30963 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30964 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30965 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30966 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30967 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30968 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30969 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30970 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30971 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30972 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30973 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30974 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30975 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30976 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30977 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30978 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30979 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30980 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30981 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30982 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30983 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30984 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30985 @{number="69",value="0x20002b03"@}]
30990 @subheading The @code{-data-read-memory} Command
30991 @findex -data-read-memory
30993 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30995 @subsubheading Synopsis
30998 -data-read-memory [ -o @var{byte-offset} ]
30999 @var{address} @var{word-format} @var{word-size}
31000 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31007 @item @var{address}
31008 An expression specifying the address of the first memory word to be
31009 read. Complex expressions containing embedded white space should be
31010 quoted using the C convention.
31012 @item @var{word-format}
31013 The format to be used to print the memory words. The notation is the
31014 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31017 @item @var{word-size}
31018 The size of each memory word in bytes.
31020 @item @var{nr-rows}
31021 The number of rows in the output table.
31023 @item @var{nr-cols}
31024 The number of columns in the output table.
31027 If present, indicates that each row should include an @sc{ascii} dump. The
31028 value of @var{aschar} is used as a padding character when a byte is not a
31029 member of the printable @sc{ascii} character set (printable @sc{ascii}
31030 characters are those whose code is between 32 and 126, inclusively).
31032 @item @var{byte-offset}
31033 An offset to add to the @var{address} before fetching memory.
31036 This command displays memory contents as a table of @var{nr-rows} by
31037 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31038 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31039 (returned as @samp{total-bytes}). Should less than the requested number
31040 of bytes be returned by the target, the missing words are identified
31041 using @samp{N/A}. The number of bytes read from the target is returned
31042 in @samp{nr-bytes} and the starting address used to read memory in
31045 The address of the next/previous row or page is available in
31046 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31049 @subsubheading @value{GDBN} Command
31051 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31052 @samp{gdb_get_mem} memory read command.
31054 @subsubheading Example
31056 Read six bytes of memory starting at @code{bytes+6} but then offset by
31057 @code{-6} bytes. Format as three rows of two columns. One byte per
31058 word. Display each word in hex.
31062 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31063 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31064 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31065 prev-page="0x0000138a",memory=[
31066 @{addr="0x00001390",data=["0x00","0x01"]@},
31067 @{addr="0x00001392",data=["0x02","0x03"]@},
31068 @{addr="0x00001394",data=["0x04","0x05"]@}]
31072 Read two bytes of memory starting at address @code{shorts + 64} and
31073 display as a single word formatted in decimal.
31077 5-data-read-memory shorts+64 d 2 1 1
31078 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31079 next-row="0x00001512",prev-row="0x0000150e",
31080 next-page="0x00001512",prev-page="0x0000150e",memory=[
31081 @{addr="0x00001510",data=["128"]@}]
31085 Read thirty two bytes of memory starting at @code{bytes+16} and format
31086 as eight rows of four columns. Include a string encoding with @samp{x}
31087 used as the non-printable character.
31091 4-data-read-memory bytes+16 x 1 8 4 x
31092 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31093 next-row="0x000013c0",prev-row="0x0000139c",
31094 next-page="0x000013c0",prev-page="0x00001380",memory=[
31095 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31096 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31097 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31098 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31099 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31100 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31101 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31102 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31106 @subheading The @code{-data-read-memory-bytes} Command
31107 @findex -data-read-memory-bytes
31109 @subsubheading Synopsis
31112 -data-read-memory-bytes [ -o @var{offset} ]
31113 @var{address} @var{count}
31120 @item @var{address}
31121 An expression specifying the address of the first addressable memory unit
31122 to be read. Complex expressions containing embedded white space should be
31123 quoted using the C convention.
31126 The number of addressable memory units to read. This should be an integer
31130 The offset relative to @var{address} at which to start reading. This
31131 should be an integer literal. This option is provided so that a frontend
31132 is not required to first evaluate address and then perform address
31133 arithmetics itself.
31137 This command attempts to read all accessible memory regions in the
31138 specified range. First, all regions marked as unreadable in the memory
31139 map (if one is defined) will be skipped. @xref{Memory Region
31140 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31141 regions. For each one, if reading full region results in an errors,
31142 @value{GDBN} will try to read a subset of the region.
31144 In general, every single memory unit in the region may be readable or not,
31145 and the only way to read every readable unit is to try a read at
31146 every address, which is not practical. Therefore, @value{GDBN} will
31147 attempt to read all accessible memory units at either beginning or the end
31148 of the region, using a binary division scheme. This heuristic works
31149 well for reading accross a memory map boundary. Note that if a region
31150 has a readable range that is neither at the beginning or the end,
31151 @value{GDBN} will not read it.
31153 The result record (@pxref{GDB/MI Result Records}) that is output of
31154 the command includes a field named @samp{memory} whose content is a
31155 list of tuples. Each tuple represent a successfully read memory block
31156 and has the following fields:
31160 The start address of the memory block, as hexadecimal literal.
31163 The end address of the memory block, as hexadecimal literal.
31166 The offset of the memory block, as hexadecimal literal, relative to
31167 the start address passed to @code{-data-read-memory-bytes}.
31170 The contents of the memory block, in hex.
31176 @subsubheading @value{GDBN} Command
31178 The corresponding @value{GDBN} command is @samp{x}.
31180 @subsubheading Example
31184 -data-read-memory-bytes &a 10
31185 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31187 contents="01000000020000000300"@}]
31192 @subheading The @code{-data-write-memory-bytes} Command
31193 @findex -data-write-memory-bytes
31195 @subsubheading Synopsis
31198 -data-write-memory-bytes @var{address} @var{contents}
31199 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31206 @item @var{address}
31207 An expression specifying the address of the first addressable memory unit
31208 to be written. Complex expressions containing embedded white space should
31209 be quoted using the C convention.
31211 @item @var{contents}
31212 The hex-encoded data to write. It is an error if @var{contents} does
31213 not represent an integral number of addressable memory units.
31216 Optional argument indicating the number of addressable memory units to be
31217 written. If @var{count} is greater than @var{contents}' length,
31218 @value{GDBN} will repeatedly write @var{contents} until it fills
31219 @var{count} memory units.
31223 @subsubheading @value{GDBN} Command
31225 There's no corresponding @value{GDBN} command.
31227 @subsubheading Example
31231 -data-write-memory-bytes &a "aabbccdd"
31238 -data-write-memory-bytes &a "aabbccdd" 16e
31243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31244 @node GDB/MI Tracepoint Commands
31245 @section @sc{gdb/mi} Tracepoint Commands
31247 The commands defined in this section implement MI support for
31248 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31250 @subheading The @code{-trace-find} Command
31251 @findex -trace-find
31253 @subsubheading Synopsis
31256 -trace-find @var{mode} [@var{parameters}@dots{}]
31259 Find a trace frame using criteria defined by @var{mode} and
31260 @var{parameters}. The following table lists permissible
31261 modes and their parameters. For details of operation, see @ref{tfind}.
31266 No parameters are required. Stops examining trace frames.
31269 An integer is required as parameter. Selects tracepoint frame with
31272 @item tracepoint-number
31273 An integer is required as parameter. Finds next
31274 trace frame that corresponds to tracepoint with the specified number.
31277 An address is required as parameter. Finds
31278 next trace frame that corresponds to any tracepoint at the specified
31281 @item pc-inside-range
31282 Two addresses are required as parameters. Finds next trace
31283 frame that corresponds to a tracepoint at an address inside the
31284 specified range. Both bounds are considered to be inside the range.
31286 @item pc-outside-range
31287 Two addresses are required as parameters. Finds
31288 next trace frame that corresponds to a tracepoint at an address outside
31289 the specified range. Both bounds are considered to be inside the range.
31292 Line specification is required as parameter. @xref{Specify Location}.
31293 Finds next trace frame that corresponds to a tracepoint at
31294 the specified location.
31298 If @samp{none} was passed as @var{mode}, the response does not
31299 have fields. Otherwise, the response may have the following fields:
31303 This field has either @samp{0} or @samp{1} as the value, depending
31304 on whether a matching tracepoint was found.
31307 The index of the found traceframe. This field is present iff
31308 the @samp{found} field has value of @samp{1}.
31311 The index of the found tracepoint. This field is present iff
31312 the @samp{found} field has value of @samp{1}.
31315 The information about the frame corresponding to the found trace
31316 frame. This field is present only if a trace frame was found.
31317 @xref{GDB/MI Frame Information}, for description of this field.
31321 @subsubheading @value{GDBN} Command
31323 The corresponding @value{GDBN} command is @samp{tfind}.
31325 @subheading -trace-define-variable
31326 @findex -trace-define-variable
31328 @subsubheading Synopsis
31331 -trace-define-variable @var{name} [ @var{value} ]
31334 Create trace variable @var{name} if it does not exist. If
31335 @var{value} is specified, sets the initial value of the specified
31336 trace variable to that value. Note that the @var{name} should start
31337 with the @samp{$} character.
31339 @subsubheading @value{GDBN} Command
31341 The corresponding @value{GDBN} command is @samp{tvariable}.
31343 @subheading The @code{-trace-frame-collected} Command
31344 @findex -trace-frame-collected
31346 @subsubheading Synopsis
31349 -trace-frame-collected
31350 [--var-print-values @var{var_pval}]
31351 [--comp-print-values @var{comp_pval}]
31352 [--registers-format @var{regformat}]
31353 [--memory-contents]
31356 This command returns the set of collected objects, register names,
31357 trace state variable names, memory ranges and computed expressions
31358 that have been collected at a particular trace frame. The optional
31359 parameters to the command affect the output format in different ways.
31360 See the output description table below for more details.
31362 The reported names can be used in the normal manner to create
31363 varobjs and inspect the objects themselves. The items returned by
31364 this command are categorized so that it is clear which is a variable,
31365 which is a register, which is a trace state variable, which is a
31366 memory range and which is a computed expression.
31368 For instance, if the actions were
31370 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31371 collect *(int*)0xaf02bef0@@40
31375 the object collected in its entirety would be @code{myVar}. The
31376 object @code{myArray} would be partially collected, because only the
31377 element at index @code{myIndex} would be collected. The remaining
31378 objects would be computed expressions.
31380 An example output would be:
31384 -trace-frame-collected
31386 explicit-variables=[@{name="myVar",value="1"@}],
31387 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31388 @{name="myObj.field",value="0"@},
31389 @{name="myPtr->field",value="1"@},
31390 @{name="myCount + 2",value="3"@},
31391 @{name="$tvar1 + 1",value="43970027"@}],
31392 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31393 @{number="1",value="0x0"@},
31394 @{number="2",value="0x4"@},
31396 @{number="125",value="0x0"@}],
31397 tvars=[@{name="$tvar1",current="43970026"@}],
31398 memory=[@{address="0x0000000000602264",length="4"@},
31399 @{address="0x0000000000615bc0",length="4"@}]
31406 @item explicit-variables
31407 The set of objects that have been collected in their entirety (as
31408 opposed to collecting just a few elements of an array or a few struct
31409 members). For each object, its name and value are printed.
31410 The @code{--var-print-values} option affects how or whether the value
31411 field is output. If @var{var_pval} is 0, then print only the names;
31412 if it is 1, print also their values; and if it is 2, print the name,
31413 type and value for simple data types, and the name and type for
31414 arrays, structures and unions.
31416 @item computed-expressions
31417 The set of computed expressions that have been collected at the
31418 current trace frame. The @code{--comp-print-values} option affects
31419 this set like the @code{--var-print-values} option affects the
31420 @code{explicit-variables} set. See above.
31423 The registers that have been collected at the current trace frame.
31424 For each register collected, the name and current value are returned.
31425 The value is formatted according to the @code{--registers-format}
31426 option. See the @command{-data-list-register-values} command for a
31427 list of the allowed formats. The default is @samp{x}.
31430 The trace state variables that have been collected at the current
31431 trace frame. For each trace state variable collected, the name and
31432 current value are returned.
31435 The set of memory ranges that have been collected at the current trace
31436 frame. Its content is a list of tuples. Each tuple represents a
31437 collected memory range and has the following fields:
31441 The start address of the memory range, as hexadecimal literal.
31444 The length of the memory range, as decimal literal.
31447 The contents of the memory block, in hex. This field is only present
31448 if the @code{--memory-contents} option is specified.
31454 @subsubheading @value{GDBN} Command
31456 There is no corresponding @value{GDBN} command.
31458 @subsubheading Example
31460 @subheading -trace-list-variables
31461 @findex -trace-list-variables
31463 @subsubheading Synopsis
31466 -trace-list-variables
31469 Return a table of all defined trace variables. Each element of the
31470 table has the following fields:
31474 The name of the trace variable. This field is always present.
31477 The initial value. This is a 64-bit signed integer. This
31478 field is always present.
31481 The value the trace variable has at the moment. This is a 64-bit
31482 signed integer. This field is absent iff current value is
31483 not defined, for example if the trace was never run, or is
31488 @subsubheading @value{GDBN} Command
31490 The corresponding @value{GDBN} command is @samp{tvariables}.
31492 @subsubheading Example
31496 -trace-list-variables
31497 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31498 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31499 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31500 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31501 body=[variable=@{name="$trace_timestamp",initial="0"@}
31502 variable=@{name="$foo",initial="10",current="15"@}]@}
31506 @subheading -trace-save
31507 @findex -trace-save
31509 @subsubheading Synopsis
31512 -trace-save [ -r ] [ -ctf ] @var{filename}
31515 Saves the collected trace data to @var{filename}. Without the
31516 @samp{-r} option, the data is downloaded from the target and saved
31517 in a local file. With the @samp{-r} option the target is asked
31518 to perform the save.
31520 By default, this command will save the trace in the tfile format. You can
31521 supply the optional @samp{-ctf} argument to save it the CTF format. See
31522 @ref{Trace Files} for more information about CTF.
31524 @subsubheading @value{GDBN} Command
31526 The corresponding @value{GDBN} command is @samp{tsave}.
31529 @subheading -trace-start
31530 @findex -trace-start
31532 @subsubheading Synopsis
31538 Starts a tracing experiment. The result of this command does not
31541 @subsubheading @value{GDBN} Command
31543 The corresponding @value{GDBN} command is @samp{tstart}.
31545 @subheading -trace-status
31546 @findex -trace-status
31548 @subsubheading Synopsis
31554 Obtains the status of a tracing experiment. The result may include
31555 the following fields:
31560 May have a value of either @samp{0}, when no tracing operations are
31561 supported, @samp{1}, when all tracing operations are supported, or
31562 @samp{file} when examining trace file. In the latter case, examining
31563 of trace frame is possible but new tracing experiement cannot be
31564 started. This field is always present.
31567 May have a value of either @samp{0} or @samp{1} depending on whether
31568 tracing experiement is in progress on target. This field is present
31569 if @samp{supported} field is not @samp{0}.
31572 Report the reason why the tracing was stopped last time. This field
31573 may be absent iff tracing was never stopped on target yet. The
31574 value of @samp{request} means the tracing was stopped as result of
31575 the @code{-trace-stop} command. The value of @samp{overflow} means
31576 the tracing buffer is full. The value of @samp{disconnection} means
31577 tracing was automatically stopped when @value{GDBN} has disconnected.
31578 The value of @samp{passcount} means tracing was stopped when a
31579 tracepoint was passed a maximal number of times for that tracepoint.
31580 This field is present if @samp{supported} field is not @samp{0}.
31582 @item stopping-tracepoint
31583 The number of tracepoint whose passcount as exceeded. This field is
31584 present iff the @samp{stop-reason} field has the value of
31588 @itemx frames-created
31589 The @samp{frames} field is a count of the total number of trace frames
31590 in the trace buffer, while @samp{frames-created} is the total created
31591 during the run, including ones that were discarded, such as when a
31592 circular trace buffer filled up. Both fields are optional.
31596 These fields tell the current size of the tracing buffer and the
31597 remaining space. These fields are optional.
31600 The value of the circular trace buffer flag. @code{1} means that the
31601 trace buffer is circular and old trace frames will be discarded if
31602 necessary to make room, @code{0} means that the trace buffer is linear
31606 The value of the disconnected tracing flag. @code{1} means that
31607 tracing will continue after @value{GDBN} disconnects, @code{0} means
31608 that the trace run will stop.
31611 The filename of the trace file being examined. This field is
31612 optional, and only present when examining a trace file.
31616 @subsubheading @value{GDBN} Command
31618 The corresponding @value{GDBN} command is @samp{tstatus}.
31620 @subheading -trace-stop
31621 @findex -trace-stop
31623 @subsubheading Synopsis
31629 Stops a tracing experiment. The result of this command has the same
31630 fields as @code{-trace-status}, except that the @samp{supported} and
31631 @samp{running} fields are not output.
31633 @subsubheading @value{GDBN} Command
31635 The corresponding @value{GDBN} command is @samp{tstop}.
31638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31639 @node GDB/MI Symbol Query
31640 @section @sc{gdb/mi} Symbol Query Commands
31644 @subheading The @code{-symbol-info-address} Command
31645 @findex -symbol-info-address
31647 @subsubheading Synopsis
31650 -symbol-info-address @var{symbol}
31653 Describe where @var{symbol} is stored.
31655 @subsubheading @value{GDBN} Command
31657 The corresponding @value{GDBN} command is @samp{info address}.
31659 @subsubheading Example
31663 @subheading The @code{-symbol-info-file} Command
31664 @findex -symbol-info-file
31666 @subsubheading Synopsis
31672 Show the file for the symbol.
31674 @subsubheading @value{GDBN} Command
31676 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31677 @samp{gdb_find_file}.
31679 @subsubheading Example
31683 @subheading The @code{-symbol-info-function} Command
31684 @findex -symbol-info-function
31686 @subsubheading Synopsis
31689 -symbol-info-function
31692 Show which function the symbol lives in.
31694 @subsubheading @value{GDBN} Command
31696 @samp{gdb_get_function} in @code{gdbtk}.
31698 @subsubheading Example
31702 @subheading The @code{-symbol-info-line} Command
31703 @findex -symbol-info-line
31705 @subsubheading Synopsis
31711 Show the core addresses of the code for a source line.
31713 @subsubheading @value{GDBN} Command
31715 The corresponding @value{GDBN} command is @samp{info line}.
31716 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31718 @subsubheading Example
31722 @subheading The @code{-symbol-info-symbol} Command
31723 @findex -symbol-info-symbol
31725 @subsubheading Synopsis
31728 -symbol-info-symbol @var{addr}
31731 Describe what symbol is at location @var{addr}.
31733 @subsubheading @value{GDBN} Command
31735 The corresponding @value{GDBN} command is @samp{info symbol}.
31737 @subsubheading Example
31741 @subheading The @code{-symbol-list-functions} Command
31742 @findex -symbol-list-functions
31744 @subsubheading Synopsis
31747 -symbol-list-functions
31750 List the functions in the executable.
31752 @subsubheading @value{GDBN} Command
31754 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31755 @samp{gdb_search} in @code{gdbtk}.
31757 @subsubheading Example
31762 @subheading The @code{-symbol-list-lines} Command
31763 @findex -symbol-list-lines
31765 @subsubheading Synopsis
31768 -symbol-list-lines @var{filename}
31771 Print the list of lines that contain code and their associated program
31772 addresses for the given source filename. The entries are sorted in
31773 ascending PC order.
31775 @subsubheading @value{GDBN} Command
31777 There is no corresponding @value{GDBN} command.
31779 @subsubheading Example
31782 -symbol-list-lines basics.c
31783 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31789 @subheading The @code{-symbol-list-types} Command
31790 @findex -symbol-list-types
31792 @subsubheading Synopsis
31798 List all the type names.
31800 @subsubheading @value{GDBN} Command
31802 The corresponding commands are @samp{info types} in @value{GDBN},
31803 @samp{gdb_search} in @code{gdbtk}.
31805 @subsubheading Example
31809 @subheading The @code{-symbol-list-variables} Command
31810 @findex -symbol-list-variables
31812 @subsubheading Synopsis
31815 -symbol-list-variables
31818 List all the global and static variable names.
31820 @subsubheading @value{GDBN} Command
31822 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31824 @subsubheading Example
31828 @subheading The @code{-symbol-locate} Command
31829 @findex -symbol-locate
31831 @subsubheading Synopsis
31837 @subsubheading @value{GDBN} Command
31839 @samp{gdb_loc} in @code{gdbtk}.
31841 @subsubheading Example
31845 @subheading The @code{-symbol-type} Command
31846 @findex -symbol-type
31848 @subsubheading Synopsis
31851 -symbol-type @var{variable}
31854 Show type of @var{variable}.
31856 @subsubheading @value{GDBN} Command
31858 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31859 @samp{gdb_obj_variable}.
31861 @subsubheading Example
31866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31867 @node GDB/MI File Commands
31868 @section @sc{gdb/mi} File Commands
31870 This section describes the GDB/MI commands to specify executable file names
31871 and to read in and obtain symbol table information.
31873 @subheading The @code{-file-exec-and-symbols} Command
31874 @findex -file-exec-and-symbols
31876 @subsubheading Synopsis
31879 -file-exec-and-symbols @var{file}
31882 Specify the executable file to be debugged. This file is the one from
31883 which the symbol table is also read. If no file is specified, the
31884 command clears the executable and symbol information. If breakpoints
31885 are set when using this command with no arguments, @value{GDBN} will produce
31886 error messages. Otherwise, no output is produced, except a completion
31889 @subsubheading @value{GDBN} Command
31891 The corresponding @value{GDBN} command is @samp{file}.
31893 @subsubheading Example
31897 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31903 @subheading The @code{-file-exec-file} Command
31904 @findex -file-exec-file
31906 @subsubheading Synopsis
31909 -file-exec-file @var{file}
31912 Specify the executable file to be debugged. Unlike
31913 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31914 from this file. If used without argument, @value{GDBN} clears the information
31915 about the executable file. No output is produced, except a completion
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} command is @samp{exec-file}.
31922 @subsubheading Example
31926 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31933 @subheading The @code{-file-list-exec-sections} Command
31934 @findex -file-list-exec-sections
31936 @subsubheading Synopsis
31939 -file-list-exec-sections
31942 List the sections of the current executable file.
31944 @subsubheading @value{GDBN} Command
31946 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31947 information as this command. @code{gdbtk} has a corresponding command
31948 @samp{gdb_load_info}.
31950 @subsubheading Example
31955 @subheading The @code{-file-list-exec-source-file} Command
31956 @findex -file-list-exec-source-file
31958 @subsubheading Synopsis
31961 -file-list-exec-source-file
31964 List the line number, the current source file, and the absolute path
31965 to the current source file for the current executable. The macro
31966 information field has a value of @samp{1} or @samp{0} depending on
31967 whether or not the file includes preprocessor macro information.
31969 @subsubheading @value{GDBN} Command
31971 The @value{GDBN} equivalent is @samp{info source}
31973 @subsubheading Example
31977 123-file-list-exec-source-file
31978 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31983 @subheading The @code{-file-list-exec-source-files} Command
31984 @findex -file-list-exec-source-files
31986 @subsubheading Synopsis
31989 -file-list-exec-source-files
31992 List the source files for the current executable.
31994 It will always output both the filename and fullname (absolute file
31995 name) of a source file.
31997 @subsubheading @value{GDBN} Command
31999 The @value{GDBN} equivalent is @samp{info sources}.
32000 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32002 @subsubheading Example
32005 -file-list-exec-source-files
32007 @{file=foo.c,fullname=/home/foo.c@},
32008 @{file=/home/bar.c,fullname=/home/bar.c@},
32009 @{file=gdb_could_not_find_fullpath.c@}]
32013 @subheading The @code{-file-list-shared-libraries} Command
32014 @findex -file-list-shared-libraries
32016 @subsubheading Synopsis
32019 -file-list-shared-libraries [ @var{regexp} ]
32022 List the shared libraries in the program.
32023 With a regular expression @var{regexp}, only those libraries whose
32024 names match @var{regexp} are listed.
32026 @subsubheading @value{GDBN} Command
32028 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32029 have a similar meaning to the @code{=library-loaded} notification.
32030 The @code{ranges} field specifies the multiple segments belonging to this
32031 library. Each range has the following fields:
32035 The address defining the inclusive lower bound of the segment.
32037 The address defining the exclusive upper bound of the segment.
32040 @subsubheading Example
32043 -file-list-exec-source-files
32044 ^done,shared-libraries=[
32045 @{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"@}]@},
32046 @{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"@}]@}]
32052 @subheading The @code{-file-list-symbol-files} Command
32053 @findex -file-list-symbol-files
32055 @subsubheading Synopsis
32058 -file-list-symbol-files
32063 @subsubheading @value{GDBN} Command
32065 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32067 @subsubheading Example
32072 @subheading The @code{-file-symbol-file} Command
32073 @findex -file-symbol-file
32075 @subsubheading Synopsis
32078 -file-symbol-file @var{file}
32081 Read symbol table info from the specified @var{file} argument. When
32082 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32083 produced, except for a completion notification.
32085 @subsubheading @value{GDBN} Command
32087 The corresponding @value{GDBN} command is @samp{symbol-file}.
32089 @subsubheading Example
32093 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32099 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32100 @node GDB/MI Memory Overlay Commands
32101 @section @sc{gdb/mi} Memory Overlay Commands
32103 The memory overlay commands are not implemented.
32105 @c @subheading -overlay-auto
32107 @c @subheading -overlay-list-mapping-state
32109 @c @subheading -overlay-list-overlays
32111 @c @subheading -overlay-map
32113 @c @subheading -overlay-off
32115 @c @subheading -overlay-on
32117 @c @subheading -overlay-unmap
32119 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32120 @node GDB/MI Signal Handling Commands
32121 @section @sc{gdb/mi} Signal Handling Commands
32123 Signal handling commands are not implemented.
32125 @c @subheading -signal-handle
32127 @c @subheading -signal-list-handle-actions
32129 @c @subheading -signal-list-signal-types
32133 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32134 @node GDB/MI Target Manipulation
32135 @section @sc{gdb/mi} Target Manipulation Commands
32138 @subheading The @code{-target-attach} Command
32139 @findex -target-attach
32141 @subsubheading Synopsis
32144 -target-attach @var{pid} | @var{gid} | @var{file}
32147 Attach to a process @var{pid} or a file @var{file} outside of
32148 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32149 group, the id previously returned by
32150 @samp{-list-thread-groups --available} must be used.
32152 @subsubheading @value{GDBN} Command
32154 The corresponding @value{GDBN} command is @samp{attach}.
32156 @subsubheading Example
32160 =thread-created,id="1"
32161 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32167 @subheading The @code{-target-compare-sections} Command
32168 @findex -target-compare-sections
32170 @subsubheading Synopsis
32173 -target-compare-sections [ @var{section} ]
32176 Compare data of section @var{section} on target to the exec file.
32177 Without the argument, all sections are compared.
32179 @subsubheading @value{GDBN} Command
32181 The @value{GDBN} equivalent is @samp{compare-sections}.
32183 @subsubheading Example
32188 @subheading The @code{-target-detach} Command
32189 @findex -target-detach
32191 @subsubheading Synopsis
32194 -target-detach [ @var{pid} | @var{gid} ]
32197 Detach from the remote target which normally resumes its execution.
32198 If either @var{pid} or @var{gid} is specified, detaches from either
32199 the specified process, or specified thread group. There's no output.
32201 @subsubheading @value{GDBN} Command
32203 The corresponding @value{GDBN} command is @samp{detach}.
32205 @subsubheading Example
32215 @subheading The @code{-target-disconnect} Command
32216 @findex -target-disconnect
32218 @subsubheading Synopsis
32224 Disconnect from the remote target. There's no output and the target is
32225 generally not resumed.
32227 @subsubheading @value{GDBN} Command
32229 The corresponding @value{GDBN} command is @samp{disconnect}.
32231 @subsubheading Example
32241 @subheading The @code{-target-download} Command
32242 @findex -target-download
32244 @subsubheading Synopsis
32250 Loads the executable onto the remote target.
32251 It prints out an update message every half second, which includes the fields:
32255 The name of the section.
32257 The size of what has been sent so far for that section.
32259 The size of the section.
32261 The total size of what was sent so far (the current and the previous sections).
32263 The size of the overall executable to download.
32267 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32268 @sc{gdb/mi} Output Syntax}).
32270 In addition, it prints the name and size of the sections, as they are
32271 downloaded. These messages include the following fields:
32275 The name of the section.
32277 The size of the section.
32279 The size of the overall executable to download.
32283 At the end, a summary is printed.
32285 @subsubheading @value{GDBN} Command
32287 The corresponding @value{GDBN} command is @samp{load}.
32289 @subsubheading Example
32291 Note: each status message appears on a single line. Here the messages
32292 have been broken down so that they can fit onto a page.
32297 +download,@{section=".text",section-size="6668",total-size="9880"@}
32298 +download,@{section=".text",section-sent="512",section-size="6668",
32299 total-sent="512",total-size="9880"@}
32300 +download,@{section=".text",section-sent="1024",section-size="6668",
32301 total-sent="1024",total-size="9880"@}
32302 +download,@{section=".text",section-sent="1536",section-size="6668",
32303 total-sent="1536",total-size="9880"@}
32304 +download,@{section=".text",section-sent="2048",section-size="6668",
32305 total-sent="2048",total-size="9880"@}
32306 +download,@{section=".text",section-sent="2560",section-size="6668",
32307 total-sent="2560",total-size="9880"@}
32308 +download,@{section=".text",section-sent="3072",section-size="6668",
32309 total-sent="3072",total-size="9880"@}
32310 +download,@{section=".text",section-sent="3584",section-size="6668",
32311 total-sent="3584",total-size="9880"@}
32312 +download,@{section=".text",section-sent="4096",section-size="6668",
32313 total-sent="4096",total-size="9880"@}
32314 +download,@{section=".text",section-sent="4608",section-size="6668",
32315 total-sent="4608",total-size="9880"@}
32316 +download,@{section=".text",section-sent="5120",section-size="6668",
32317 total-sent="5120",total-size="9880"@}
32318 +download,@{section=".text",section-sent="5632",section-size="6668",
32319 total-sent="5632",total-size="9880"@}
32320 +download,@{section=".text",section-sent="6144",section-size="6668",
32321 total-sent="6144",total-size="9880"@}
32322 +download,@{section=".text",section-sent="6656",section-size="6668",
32323 total-sent="6656",total-size="9880"@}
32324 +download,@{section=".init",section-size="28",total-size="9880"@}
32325 +download,@{section=".fini",section-size="28",total-size="9880"@}
32326 +download,@{section=".data",section-size="3156",total-size="9880"@}
32327 +download,@{section=".data",section-sent="512",section-size="3156",
32328 total-sent="7236",total-size="9880"@}
32329 +download,@{section=".data",section-sent="1024",section-size="3156",
32330 total-sent="7748",total-size="9880"@}
32331 +download,@{section=".data",section-sent="1536",section-size="3156",
32332 total-sent="8260",total-size="9880"@}
32333 +download,@{section=".data",section-sent="2048",section-size="3156",
32334 total-sent="8772",total-size="9880"@}
32335 +download,@{section=".data",section-sent="2560",section-size="3156",
32336 total-sent="9284",total-size="9880"@}
32337 +download,@{section=".data",section-sent="3072",section-size="3156",
32338 total-sent="9796",total-size="9880"@}
32339 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32346 @subheading The @code{-target-exec-status} Command
32347 @findex -target-exec-status
32349 @subsubheading Synopsis
32352 -target-exec-status
32355 Provide information on the state of the target (whether it is running or
32356 not, for instance).
32358 @subsubheading @value{GDBN} Command
32360 There's no equivalent @value{GDBN} command.
32362 @subsubheading Example
32366 @subheading The @code{-target-list-available-targets} Command
32367 @findex -target-list-available-targets
32369 @subsubheading Synopsis
32372 -target-list-available-targets
32375 List the possible targets to connect to.
32377 @subsubheading @value{GDBN} Command
32379 The corresponding @value{GDBN} command is @samp{help target}.
32381 @subsubheading Example
32385 @subheading The @code{-target-list-current-targets} Command
32386 @findex -target-list-current-targets
32388 @subsubheading Synopsis
32391 -target-list-current-targets
32394 Describe the current target.
32396 @subsubheading @value{GDBN} Command
32398 The corresponding information is printed by @samp{info file} (among
32401 @subsubheading Example
32405 @subheading The @code{-target-list-parameters} Command
32406 @findex -target-list-parameters
32408 @subsubheading Synopsis
32411 -target-list-parameters
32417 @subsubheading @value{GDBN} Command
32421 @subsubheading Example
32424 @subheading The @code{-target-flash-erase} Command
32425 @findex -target-flash-erase
32427 @subsubheading Synopsis
32430 -target-flash-erase
32433 Erases all known flash memory regions on the target.
32435 The corresponding @value{GDBN} command is @samp{flash-erase}.
32437 The output is a list of flash regions that have been erased, with starting
32438 addresses and memory region sizes.
32442 -target-flash-erase
32443 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32447 @subheading The @code{-target-select} Command
32448 @findex -target-select
32450 @subsubheading Synopsis
32453 -target-select @var{type} @var{parameters @dots{}}
32456 Connect @value{GDBN} to the remote target. This command takes two args:
32460 The type of target, for instance @samp{remote}, etc.
32461 @item @var{parameters}
32462 Device names, host names and the like. @xref{Target Commands, ,
32463 Commands for Managing Targets}, for more details.
32466 The output is a connection notification, followed by the address at
32467 which the target program is, in the following form:
32470 ^connected,addr="@var{address}",func="@var{function name}",
32471 args=[@var{arg list}]
32474 @subsubheading @value{GDBN} Command
32476 The corresponding @value{GDBN} command is @samp{target}.
32478 @subsubheading Example
32482 -target-select remote /dev/ttya
32483 ^connected,addr="0xfe00a300",func="??",args=[]
32487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32488 @node GDB/MI File Transfer Commands
32489 @section @sc{gdb/mi} File Transfer Commands
32492 @subheading The @code{-target-file-put} Command
32493 @findex -target-file-put
32495 @subsubheading Synopsis
32498 -target-file-put @var{hostfile} @var{targetfile}
32501 Copy file @var{hostfile} from the host system (the machine running
32502 @value{GDBN}) to @var{targetfile} on the target system.
32504 @subsubheading @value{GDBN} Command
32506 The corresponding @value{GDBN} command is @samp{remote put}.
32508 @subsubheading Example
32512 -target-file-put localfile remotefile
32518 @subheading The @code{-target-file-get} Command
32519 @findex -target-file-get
32521 @subsubheading Synopsis
32524 -target-file-get @var{targetfile} @var{hostfile}
32527 Copy file @var{targetfile} from the target system to @var{hostfile}
32528 on the host system.
32530 @subsubheading @value{GDBN} Command
32532 The corresponding @value{GDBN} command is @samp{remote get}.
32534 @subsubheading Example
32538 -target-file-get remotefile localfile
32544 @subheading The @code{-target-file-delete} Command
32545 @findex -target-file-delete
32547 @subsubheading Synopsis
32550 -target-file-delete @var{targetfile}
32553 Delete @var{targetfile} from the target system.
32555 @subsubheading @value{GDBN} Command
32557 The corresponding @value{GDBN} command is @samp{remote delete}.
32559 @subsubheading Example
32563 -target-file-delete remotefile
32569 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32570 @node GDB/MI Ada Exceptions Commands
32571 @section Ada Exceptions @sc{gdb/mi} Commands
32573 @subheading The @code{-info-ada-exceptions} Command
32574 @findex -info-ada-exceptions
32576 @subsubheading Synopsis
32579 -info-ada-exceptions [ @var{regexp}]
32582 List all Ada exceptions defined within the program being debugged.
32583 With a regular expression @var{regexp}, only those exceptions whose
32584 names match @var{regexp} are listed.
32586 @subsubheading @value{GDBN} Command
32588 The corresponding @value{GDBN} command is @samp{info exceptions}.
32590 @subsubheading Result
32592 The result is a table of Ada exceptions. The following columns are
32593 defined for each exception:
32597 The name of the exception.
32600 The address of the exception.
32604 @subsubheading Example
32607 -info-ada-exceptions aint
32608 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32609 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32610 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32611 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32612 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32615 @subheading Catching Ada Exceptions
32617 The commands describing how to ask @value{GDBN} to stop when a program
32618 raises an exception are described at @ref{Ada Exception GDB/MI
32619 Catchpoint Commands}.
32622 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32623 @node GDB/MI Support Commands
32624 @section @sc{gdb/mi} Support Commands
32626 Since new commands and features get regularly added to @sc{gdb/mi},
32627 some commands are available to help front-ends query the debugger
32628 about support for these capabilities. Similarly, it is also possible
32629 to query @value{GDBN} about target support of certain features.
32631 @subheading The @code{-info-gdb-mi-command} Command
32632 @cindex @code{-info-gdb-mi-command}
32633 @findex -info-gdb-mi-command
32635 @subsubheading Synopsis
32638 -info-gdb-mi-command @var{cmd_name}
32641 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32643 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32644 is technically not part of the command name (@pxref{GDB/MI Input
32645 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32646 for ease of use, this command also accepts the form with the leading
32649 @subsubheading @value{GDBN} Command
32651 There is no corresponding @value{GDBN} command.
32653 @subsubheading Result
32655 The result is a tuple. There is currently only one field:
32659 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32660 @code{"false"} otherwise.
32664 @subsubheading Example
32666 Here is an example where the @sc{gdb/mi} command does not exist:
32669 -info-gdb-mi-command unsupported-command
32670 ^done,command=@{exists="false"@}
32674 And here is an example where the @sc{gdb/mi} command is known
32678 -info-gdb-mi-command symbol-list-lines
32679 ^done,command=@{exists="true"@}
32682 @subheading The @code{-list-features} Command
32683 @findex -list-features
32684 @cindex supported @sc{gdb/mi} features, list
32686 Returns a list of particular features of the MI protocol that
32687 this version of gdb implements. A feature can be a command,
32688 or a new field in an output of some command, or even an
32689 important bugfix. While a frontend can sometimes detect presence
32690 of a feature at runtime, it is easier to perform detection at debugger
32693 The command returns a list of strings, with each string naming an
32694 available feature. Each returned string is just a name, it does not
32695 have any internal structure. The list of possible feature names
32701 (gdb) -list-features
32702 ^done,result=["feature1","feature2"]
32705 The current list of features is:
32708 @item frozen-varobjs
32709 Indicates support for the @code{-var-set-frozen} command, as well
32710 as possible presense of the @code{frozen} field in the output
32711 of @code{-varobj-create}.
32712 @item pending-breakpoints
32713 Indicates support for the @option{-f} option to the @code{-break-insert}
32716 Indicates Python scripting support, Python-based
32717 pretty-printing commands, and possible presence of the
32718 @samp{display_hint} field in the output of @code{-var-list-children}
32720 Indicates support for the @code{-thread-info} command.
32721 @item data-read-memory-bytes
32722 Indicates support for the @code{-data-read-memory-bytes} and the
32723 @code{-data-write-memory-bytes} commands.
32724 @item breakpoint-notifications
32725 Indicates that changes to breakpoints and breakpoints created via the
32726 CLI will be announced via async records.
32727 @item ada-task-info
32728 Indicates support for the @code{-ada-task-info} command.
32729 @item language-option
32730 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32731 option (@pxref{Context management}).
32732 @item info-gdb-mi-command
32733 Indicates support for the @code{-info-gdb-mi-command} command.
32734 @item undefined-command-error-code
32735 Indicates support for the "undefined-command" error code in error result
32736 records, produced when trying to execute an undefined @sc{gdb/mi} command
32737 (@pxref{GDB/MI Result Records}).
32738 @item exec-run-start-option
32739 Indicates that the @code{-exec-run} command supports the @option{--start}
32740 option (@pxref{GDB/MI Program Execution}).
32743 @subheading The @code{-list-target-features} Command
32744 @findex -list-target-features
32746 Returns a list of particular features that are supported by the
32747 target. Those features affect the permitted MI commands, but
32748 unlike the features reported by the @code{-list-features} command, the
32749 features depend on which target GDB is using at the moment. Whenever
32750 a target can change, due to commands such as @code{-target-select},
32751 @code{-target-attach} or @code{-exec-run}, the list of target features
32752 may change, and the frontend should obtain it again.
32756 (gdb) -list-target-features
32757 ^done,result=["async"]
32760 The current list of features is:
32764 Indicates that the target is capable of asynchronous command
32765 execution, which means that @value{GDBN} will accept further commands
32766 while the target is running.
32769 Indicates that the target is capable of reverse execution.
32770 @xref{Reverse Execution}, for more information.
32774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32775 @node GDB/MI Miscellaneous Commands
32776 @section Miscellaneous @sc{gdb/mi} Commands
32778 @c @subheading -gdb-complete
32780 @subheading The @code{-gdb-exit} Command
32783 @subsubheading Synopsis
32789 Exit @value{GDBN} immediately.
32791 @subsubheading @value{GDBN} Command
32793 Approximately corresponds to @samp{quit}.
32795 @subsubheading Example
32805 @subheading The @code{-exec-abort} Command
32806 @findex -exec-abort
32808 @subsubheading Synopsis
32814 Kill the inferior running program.
32816 @subsubheading @value{GDBN} Command
32818 The corresponding @value{GDBN} command is @samp{kill}.
32820 @subsubheading Example
32825 @subheading The @code{-gdb-set} Command
32828 @subsubheading Synopsis
32834 Set an internal @value{GDBN} variable.
32835 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32837 @subsubheading @value{GDBN} Command
32839 The corresponding @value{GDBN} command is @samp{set}.
32841 @subsubheading Example
32851 @subheading The @code{-gdb-show} Command
32854 @subsubheading Synopsis
32860 Show the current value of a @value{GDBN} variable.
32862 @subsubheading @value{GDBN} Command
32864 The corresponding @value{GDBN} command is @samp{show}.
32866 @subsubheading Example
32875 @c @subheading -gdb-source
32878 @subheading The @code{-gdb-version} Command
32879 @findex -gdb-version
32881 @subsubheading Synopsis
32887 Show version information for @value{GDBN}. Used mostly in testing.
32889 @subsubheading @value{GDBN} Command
32891 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32892 default shows this information when you start an interactive session.
32894 @subsubheading Example
32896 @c This example modifies the actual output from GDB to avoid overfull
32902 ~Copyright 2000 Free Software Foundation, Inc.
32903 ~GDB is free software, covered by the GNU General Public License, and
32904 ~you are welcome to change it and/or distribute copies of it under
32905 ~ certain conditions.
32906 ~Type "show copying" to see the conditions.
32907 ~There is absolutely no warranty for GDB. Type "show warranty" for
32909 ~This GDB was configured as
32910 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32915 @subheading The @code{-list-thread-groups} Command
32916 @findex -list-thread-groups
32918 @subheading Synopsis
32921 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32924 Lists thread groups (@pxref{Thread groups}). When a single thread
32925 group is passed as the argument, lists the children of that group.
32926 When several thread group are passed, lists information about those
32927 thread groups. Without any parameters, lists information about all
32928 top-level thread groups.
32930 Normally, thread groups that are being debugged are reported.
32931 With the @samp{--available} option, @value{GDBN} reports thread groups
32932 available on the target.
32934 The output of this command may have either a @samp{threads} result or
32935 a @samp{groups} result. The @samp{thread} result has a list of tuples
32936 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32937 Information}). The @samp{groups} result has a list of tuples as value,
32938 each tuple describing a thread group. If top-level groups are
32939 requested (that is, no parameter is passed), or when several groups
32940 are passed, the output always has a @samp{groups} result. The format
32941 of the @samp{group} result is described below.
32943 To reduce the number of roundtrips it's possible to list thread groups
32944 together with their children, by passing the @samp{--recurse} option
32945 and the recursion depth. Presently, only recursion depth of 1 is
32946 permitted. If this option is present, then every reported thread group
32947 will also include its children, either as @samp{group} or
32948 @samp{threads} field.
32950 In general, any combination of option and parameters is permitted, with
32951 the following caveats:
32955 When a single thread group is passed, the output will typically
32956 be the @samp{threads} result. Because threads may not contain
32957 anything, the @samp{recurse} option will be ignored.
32960 When the @samp{--available} option is passed, limited information may
32961 be available. In particular, the list of threads of a process might
32962 be inaccessible. Further, specifying specific thread groups might
32963 not give any performance advantage over listing all thread groups.
32964 The frontend should assume that @samp{-list-thread-groups --available}
32965 is always an expensive operation and cache the results.
32969 The @samp{groups} result is a list of tuples, where each tuple may
32970 have the following fields:
32974 Identifier of the thread group. This field is always present.
32975 The identifier is an opaque string; frontends should not try to
32976 convert it to an integer, even though it might look like one.
32979 The type of the thread group. At present, only @samp{process} is a
32983 The target-specific process identifier. This field is only present
32984 for thread groups of type @samp{process} and only if the process exists.
32987 The exit code of this group's last exited thread, formatted in octal.
32988 This field is only present for thread groups of type @samp{process} and
32989 only if the process is not running.
32992 The number of children this thread group has. This field may be
32993 absent for an available thread group.
32996 This field has a list of tuples as value, each tuple describing a
32997 thread. It may be present if the @samp{--recurse} option is
32998 specified, and it's actually possible to obtain the threads.
33001 This field is a list of integers, each identifying a core that one
33002 thread of the group is running on. This field may be absent if
33003 such information is not available.
33006 The name of the executable file that corresponds to this thread group.
33007 The field is only present for thread groups of type @samp{process},
33008 and only if there is a corresponding executable file.
33012 @subheading Example
33016 -list-thread-groups
33017 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33018 -list-thread-groups 17
33019 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33020 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33021 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33022 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33023 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33024 -list-thread-groups --available
33025 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33026 -list-thread-groups --available --recurse 1
33027 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33028 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33029 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33030 -list-thread-groups --available --recurse 1 17 18
33031 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33032 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33033 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33036 @subheading The @code{-info-os} Command
33039 @subsubheading Synopsis
33042 -info-os [ @var{type} ]
33045 If no argument is supplied, the command returns a table of available
33046 operating-system-specific information types. If one of these types is
33047 supplied as an argument @var{type}, then the command returns a table
33048 of data of that type.
33050 The types of information available depend on the target operating
33053 @subsubheading @value{GDBN} Command
33055 The corresponding @value{GDBN} command is @samp{info os}.
33057 @subsubheading Example
33059 When run on a @sc{gnu}/Linux system, the output will look something
33065 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33066 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33067 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33068 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33069 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33071 item=@{col0="files",col1="Listing of all file descriptors",
33072 col2="File descriptors"@},
33073 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33074 col2="Kernel modules"@},
33075 item=@{col0="msg",col1="Listing of all message queues",
33076 col2="Message queues"@},
33077 item=@{col0="processes",col1="Listing of all processes",
33078 col2="Processes"@},
33079 item=@{col0="procgroups",col1="Listing of all process groups",
33080 col2="Process groups"@},
33081 item=@{col0="semaphores",col1="Listing of all semaphores",
33082 col2="Semaphores"@},
33083 item=@{col0="shm",col1="Listing of all shared-memory regions",
33084 col2="Shared-memory regions"@},
33085 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33087 item=@{col0="threads",col1="Listing of all threads",
33091 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33092 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33093 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33094 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33095 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33096 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33097 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33098 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33100 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33101 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33105 (Note that the MI output here includes a @code{"Title"} column that
33106 does not appear in command-line @code{info os}; this column is useful
33107 for MI clients that want to enumerate the types of data, such as in a
33108 popup menu, but is needless clutter on the command line, and
33109 @code{info os} omits it.)
33111 @subheading The @code{-add-inferior} Command
33112 @findex -add-inferior
33114 @subheading Synopsis
33120 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33121 inferior is not associated with any executable. Such association may
33122 be established with the @samp{-file-exec-and-symbols} command
33123 (@pxref{GDB/MI File Commands}). The command response has a single
33124 field, @samp{inferior}, whose value is the identifier of the
33125 thread group corresponding to the new inferior.
33127 @subheading Example
33132 ^done,inferior="i3"
33135 @subheading The @code{-interpreter-exec} Command
33136 @findex -interpreter-exec
33138 @subheading Synopsis
33141 -interpreter-exec @var{interpreter} @var{command}
33143 @anchor{-interpreter-exec}
33145 Execute the specified @var{command} in the given @var{interpreter}.
33147 @subheading @value{GDBN} Command
33149 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33151 @subheading Example
33155 -interpreter-exec console "break main"
33156 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33157 &"During symbol reading, bad structure-type format.\n"
33158 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33163 @subheading The @code{-inferior-tty-set} Command
33164 @findex -inferior-tty-set
33166 @subheading Synopsis
33169 -inferior-tty-set /dev/pts/1
33172 Set terminal for future runs of the program being debugged.
33174 @subheading @value{GDBN} Command
33176 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33178 @subheading Example
33182 -inferior-tty-set /dev/pts/1
33187 @subheading The @code{-inferior-tty-show} Command
33188 @findex -inferior-tty-show
33190 @subheading Synopsis
33196 Show terminal for future runs of program being debugged.
33198 @subheading @value{GDBN} Command
33200 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33202 @subheading Example
33206 -inferior-tty-set /dev/pts/1
33210 ^done,inferior_tty_terminal="/dev/pts/1"
33214 @subheading The @code{-enable-timings} Command
33215 @findex -enable-timings
33217 @subheading Synopsis
33220 -enable-timings [yes | no]
33223 Toggle the printing of the wallclock, user and system times for an MI
33224 command as a field in its output. This command is to help frontend
33225 developers optimize the performance of their code. No argument is
33226 equivalent to @samp{yes}.
33228 @subheading @value{GDBN} Command
33232 @subheading Example
33240 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33241 addr="0x080484ed",func="main",file="myprog.c",
33242 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33244 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33252 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33253 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33254 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33255 fullname="/home/nickrob/myprog.c",line="73"@}
33260 @chapter @value{GDBN} Annotations
33262 This chapter describes annotations in @value{GDBN}. Annotations were
33263 designed to interface @value{GDBN} to graphical user interfaces or other
33264 similar programs which want to interact with @value{GDBN} at a
33265 relatively high level.
33267 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33271 This is Edition @value{EDITION}, @value{DATE}.
33275 * Annotations Overview:: What annotations are; the general syntax.
33276 * Server Prefix:: Issuing a command without affecting user state.
33277 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33278 * Errors:: Annotations for error messages.
33279 * Invalidation:: Some annotations describe things now invalid.
33280 * Annotations for Running::
33281 Whether the program is running, how it stopped, etc.
33282 * Source Annotations:: Annotations describing source code.
33285 @node Annotations Overview
33286 @section What is an Annotation?
33287 @cindex annotations
33289 Annotations start with a newline character, two @samp{control-z}
33290 characters, and the name of the annotation. If there is no additional
33291 information associated with this annotation, the name of the annotation
33292 is followed immediately by a newline. If there is additional
33293 information, the name of the annotation is followed by a space, the
33294 additional information, and a newline. The additional information
33295 cannot contain newline characters.
33297 Any output not beginning with a newline and two @samp{control-z}
33298 characters denotes literal output from @value{GDBN}. Currently there is
33299 no need for @value{GDBN} to output a newline followed by two
33300 @samp{control-z} characters, but if there was such a need, the
33301 annotations could be extended with an @samp{escape} annotation which
33302 means those three characters as output.
33304 The annotation @var{level}, which is specified using the
33305 @option{--annotate} command line option (@pxref{Mode Options}), controls
33306 how much information @value{GDBN} prints together with its prompt,
33307 values of expressions, source lines, and other types of output. Level 0
33308 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33309 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33310 for programs that control @value{GDBN}, and level 2 annotations have
33311 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33312 Interface, annotate, GDB's Obsolete Annotations}).
33315 @kindex set annotate
33316 @item set annotate @var{level}
33317 The @value{GDBN} command @code{set annotate} sets the level of
33318 annotations to the specified @var{level}.
33320 @item show annotate
33321 @kindex show annotate
33322 Show the current annotation level.
33325 This chapter describes level 3 annotations.
33327 A simple example of starting up @value{GDBN} with annotations is:
33330 $ @kbd{gdb --annotate=3}
33332 Copyright 2003 Free Software Foundation, Inc.
33333 GDB is free software, covered by the GNU General Public License,
33334 and you are welcome to change it and/or distribute copies of it
33335 under certain conditions.
33336 Type "show copying" to see the conditions.
33337 There is absolutely no warranty for GDB. Type "show warranty"
33339 This GDB was configured as "i386-pc-linux-gnu"
33350 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33351 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33352 denotes a @samp{control-z} character) are annotations; the rest is
33353 output from @value{GDBN}.
33355 @node Server Prefix
33356 @section The Server Prefix
33357 @cindex server prefix
33359 If you prefix a command with @samp{server } then it will not affect
33360 the command history, nor will it affect @value{GDBN}'s notion of which
33361 command to repeat if @key{RET} is pressed on a line by itself. This
33362 means that commands can be run behind a user's back by a front-end in
33363 a transparent manner.
33365 The @code{server } prefix does not affect the recording of values into
33366 the value history; to print a value without recording it into the
33367 value history, use the @code{output} command instead of the
33368 @code{print} command.
33370 Using this prefix also disables confirmation requests
33371 (@pxref{confirmation requests}).
33374 @section Annotation for @value{GDBN} Input
33376 @cindex annotations for prompts
33377 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33378 to know when to send output, when the output from a given command is
33381 Different kinds of input each have a different @dfn{input type}. Each
33382 input type has three annotations: a @code{pre-} annotation, which
33383 denotes the beginning of any prompt which is being output, a plain
33384 annotation, which denotes the end of the prompt, and then a @code{post-}
33385 annotation which denotes the end of any echo which may (or may not) be
33386 associated with the input. For example, the @code{prompt} input type
33387 features the following annotations:
33395 The input types are
33398 @findex pre-prompt annotation
33399 @findex prompt annotation
33400 @findex post-prompt annotation
33402 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33404 @findex pre-commands annotation
33405 @findex commands annotation
33406 @findex post-commands annotation
33408 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33409 command. The annotations are repeated for each command which is input.
33411 @findex pre-overload-choice annotation
33412 @findex overload-choice annotation
33413 @findex post-overload-choice annotation
33414 @item overload-choice
33415 When @value{GDBN} wants the user to select between various overloaded functions.
33417 @findex pre-query annotation
33418 @findex query annotation
33419 @findex post-query annotation
33421 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33423 @findex pre-prompt-for-continue annotation
33424 @findex prompt-for-continue annotation
33425 @findex post-prompt-for-continue annotation
33426 @item prompt-for-continue
33427 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33428 expect this to work well; instead use @code{set height 0} to disable
33429 prompting. This is because the counting of lines is buggy in the
33430 presence of annotations.
33435 @cindex annotations for errors, warnings and interrupts
33437 @findex quit annotation
33442 This annotation occurs right before @value{GDBN} responds to an interrupt.
33444 @findex error annotation
33449 This annotation occurs right before @value{GDBN} responds to an error.
33451 Quit and error annotations indicate that any annotations which @value{GDBN} was
33452 in the middle of may end abruptly. For example, if a
33453 @code{value-history-begin} annotation is followed by a @code{error}, one
33454 cannot expect to receive the matching @code{value-history-end}. One
33455 cannot expect not to receive it either, however; an error annotation
33456 does not necessarily mean that @value{GDBN} is immediately returning all the way
33459 @findex error-begin annotation
33460 A quit or error annotation may be preceded by
33466 Any output between that and the quit or error annotation is the error
33469 Warning messages are not yet annotated.
33470 @c If we want to change that, need to fix warning(), type_error(),
33471 @c range_error(), and possibly other places.
33474 @section Invalidation Notices
33476 @cindex annotations for invalidation messages
33477 The following annotations say that certain pieces of state may have
33481 @findex frames-invalid annotation
33482 @item ^Z^Zframes-invalid
33484 The frames (for example, output from the @code{backtrace} command) may
33487 @findex breakpoints-invalid annotation
33488 @item ^Z^Zbreakpoints-invalid
33490 The breakpoints may have changed. For example, the user just added or
33491 deleted a breakpoint.
33494 @node Annotations for Running
33495 @section Running the Program
33496 @cindex annotations for running programs
33498 @findex starting annotation
33499 @findex stopping annotation
33500 When the program starts executing due to a @value{GDBN} command such as
33501 @code{step} or @code{continue},
33507 is output. When the program stops,
33513 is output. Before the @code{stopped} annotation, a variety of
33514 annotations describe how the program stopped.
33517 @findex exited annotation
33518 @item ^Z^Zexited @var{exit-status}
33519 The program exited, and @var{exit-status} is the exit status (zero for
33520 successful exit, otherwise nonzero).
33522 @findex signalled annotation
33523 @findex signal-name annotation
33524 @findex signal-name-end annotation
33525 @findex signal-string annotation
33526 @findex signal-string-end annotation
33527 @item ^Z^Zsignalled
33528 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33529 annotation continues:
33535 ^Z^Zsignal-name-end
33539 ^Z^Zsignal-string-end
33544 where @var{name} is the name of the signal, such as @code{SIGILL} or
33545 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33546 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33547 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33548 user's benefit and have no particular format.
33550 @findex signal annotation
33552 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33553 just saying that the program received the signal, not that it was
33554 terminated with it.
33556 @findex breakpoint annotation
33557 @item ^Z^Zbreakpoint @var{number}
33558 The program hit breakpoint number @var{number}.
33560 @findex watchpoint annotation
33561 @item ^Z^Zwatchpoint @var{number}
33562 The program hit watchpoint number @var{number}.
33565 @node Source Annotations
33566 @section Displaying Source
33567 @cindex annotations for source display
33569 @findex source annotation
33570 The following annotation is used instead of displaying source code:
33573 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33576 where @var{filename} is an absolute file name indicating which source
33577 file, @var{line} is the line number within that file (where 1 is the
33578 first line in the file), @var{character} is the character position
33579 within the file (where 0 is the first character in the file) (for most
33580 debug formats this will necessarily point to the beginning of a line),
33581 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33582 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33583 @var{addr} is the address in the target program associated with the
33584 source which is being displayed. The @var{addr} is in the form @samp{0x}
33585 followed by one or more lowercase hex digits (note that this does not
33586 depend on the language).
33588 @node JIT Interface
33589 @chapter JIT Compilation Interface
33590 @cindex just-in-time compilation
33591 @cindex JIT compilation interface
33593 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33594 interface. A JIT compiler is a program or library that generates native
33595 executable code at runtime and executes it, usually in order to achieve good
33596 performance while maintaining platform independence.
33598 Programs that use JIT compilation are normally difficult to debug because
33599 portions of their code are generated at runtime, instead of being loaded from
33600 object files, which is where @value{GDBN} normally finds the program's symbols
33601 and debug information. In order to debug programs that use JIT compilation,
33602 @value{GDBN} has an interface that allows the program to register in-memory
33603 symbol files with @value{GDBN} at runtime.
33605 If you are using @value{GDBN} to debug a program that uses this interface, then
33606 it should work transparently so long as you have not stripped the binary. If
33607 you are developing a JIT compiler, then the interface is documented in the rest
33608 of this chapter. At this time, the only known client of this interface is the
33611 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33612 JIT compiler communicates with @value{GDBN} by writing data into a global
33613 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33614 attaches, it reads a linked list of symbol files from the global variable to
33615 find existing code, and puts a breakpoint in the function so that it can find
33616 out about additional code.
33619 * Declarations:: Relevant C struct declarations
33620 * Registering Code:: Steps to register code
33621 * Unregistering Code:: Steps to unregister code
33622 * Custom Debug Info:: Emit debug information in a custom format
33626 @section JIT Declarations
33628 These are the relevant struct declarations that a C program should include to
33629 implement the interface:
33639 struct jit_code_entry
33641 struct jit_code_entry *next_entry;
33642 struct jit_code_entry *prev_entry;
33643 const char *symfile_addr;
33644 uint64_t symfile_size;
33647 struct jit_descriptor
33650 /* This type should be jit_actions_t, but we use uint32_t
33651 to be explicit about the bitwidth. */
33652 uint32_t action_flag;
33653 struct jit_code_entry *relevant_entry;
33654 struct jit_code_entry *first_entry;
33657 /* GDB puts a breakpoint in this function. */
33658 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33660 /* Make sure to specify the version statically, because the
33661 debugger may check the version before we can set it. */
33662 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33665 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33666 modifications to this global data properly, which can easily be done by putting
33667 a global mutex around modifications to these structures.
33669 @node Registering Code
33670 @section Registering Code
33672 To register code with @value{GDBN}, the JIT should follow this protocol:
33676 Generate an object file in memory with symbols and other desired debug
33677 information. The file must include the virtual addresses of the sections.
33680 Create a code entry for the file, which gives the start and size of the symbol
33684 Add it to the linked list in the JIT descriptor.
33687 Point the relevant_entry field of the descriptor at the entry.
33690 Set @code{action_flag} to @code{JIT_REGISTER} and call
33691 @code{__jit_debug_register_code}.
33694 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33695 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33696 new code. However, the linked list must still be maintained in order to allow
33697 @value{GDBN} to attach to a running process and still find the symbol files.
33699 @node Unregistering Code
33700 @section Unregistering Code
33702 If code is freed, then the JIT should use the following protocol:
33706 Remove the code entry corresponding to the code from the linked list.
33709 Point the @code{relevant_entry} field of the descriptor at the code entry.
33712 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33713 @code{__jit_debug_register_code}.
33716 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33717 and the JIT will leak the memory used for the associated symbol files.
33719 @node Custom Debug Info
33720 @section Custom Debug Info
33721 @cindex custom JIT debug info
33722 @cindex JIT debug info reader
33724 Generating debug information in platform-native file formats (like ELF
33725 or COFF) may be an overkill for JIT compilers; especially if all the
33726 debug info is used for is displaying a meaningful backtrace. The
33727 issue can be resolved by having the JIT writers decide on a debug info
33728 format and also provide a reader that parses the debug info generated
33729 by the JIT compiler. This section gives a brief overview on writing
33730 such a parser. More specific details can be found in the source file
33731 @file{gdb/jit-reader.in}, which is also installed as a header at
33732 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33734 The reader is implemented as a shared object (so this functionality is
33735 not available on platforms which don't allow loading shared objects at
33736 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33737 @code{jit-reader-unload} are provided, to be used to load and unload
33738 the readers from a preconfigured directory. Once loaded, the shared
33739 object is used the parse the debug information emitted by the JIT
33743 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33744 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33747 @node Using JIT Debug Info Readers
33748 @subsection Using JIT Debug Info Readers
33749 @kindex jit-reader-load
33750 @kindex jit-reader-unload
33752 Readers can be loaded and unloaded using the @code{jit-reader-load}
33753 and @code{jit-reader-unload} commands.
33756 @item jit-reader-load @var{reader}
33757 Load the JIT reader named @var{reader}, which is a shared
33758 object specified as either an absolute or a relative file name. In
33759 the latter case, @value{GDBN} will try to load the reader from a
33760 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33761 system (here @var{libdir} is the system library directory, often
33762 @file{/usr/local/lib}).
33764 Only one reader can be active at a time; trying to load a second
33765 reader when one is already loaded will result in @value{GDBN}
33766 reporting an error. A new JIT reader can be loaded by first unloading
33767 the current one using @code{jit-reader-unload} and then invoking
33768 @code{jit-reader-load}.
33770 @item jit-reader-unload
33771 Unload the currently loaded JIT reader.
33775 @node Writing JIT Debug Info Readers
33776 @subsection Writing JIT Debug Info Readers
33777 @cindex writing JIT debug info readers
33779 As mentioned, a reader is essentially a shared object conforming to a
33780 certain ABI. This ABI is described in @file{jit-reader.h}.
33782 @file{jit-reader.h} defines the structures, macros and functions
33783 required to write a reader. It is installed (along with
33784 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33785 the system include directory.
33787 Readers need to be released under a GPL compatible license. A reader
33788 can be declared as released under such a license by placing the macro
33789 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33791 The entry point for readers is the symbol @code{gdb_init_reader},
33792 which is expected to be a function with the prototype
33794 @findex gdb_init_reader
33796 extern struct gdb_reader_funcs *gdb_init_reader (void);
33799 @cindex @code{struct gdb_reader_funcs}
33801 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33802 functions. These functions are executed to read the debug info
33803 generated by the JIT compiler (@code{read}), to unwind stack frames
33804 (@code{unwind}) and to create canonical frame IDs
33805 (@code{get_Frame_id}). It also has a callback that is called when the
33806 reader is being unloaded (@code{destroy}). The struct looks like this
33809 struct gdb_reader_funcs
33811 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33812 int reader_version;
33814 /* For use by the reader. */
33817 gdb_read_debug_info *read;
33818 gdb_unwind_frame *unwind;
33819 gdb_get_frame_id *get_frame_id;
33820 gdb_destroy_reader *destroy;
33824 @cindex @code{struct gdb_symbol_callbacks}
33825 @cindex @code{struct gdb_unwind_callbacks}
33827 The callbacks are provided with another set of callbacks by
33828 @value{GDBN} to do their job. For @code{read}, these callbacks are
33829 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33830 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33831 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33832 files and new symbol tables inside those object files. @code{struct
33833 gdb_unwind_callbacks} has callbacks to read registers off the current
33834 frame and to write out the values of the registers in the previous
33835 frame. Both have a callback (@code{target_read}) to read bytes off the
33836 target's address space.
33838 @node In-Process Agent
33839 @chapter In-Process Agent
33840 @cindex debugging agent
33841 The traditional debugging model is conceptually low-speed, but works fine,
33842 because most bugs can be reproduced in debugging-mode execution. However,
33843 as multi-core or many-core processors are becoming mainstream, and
33844 multi-threaded programs become more and more popular, there should be more
33845 and more bugs that only manifest themselves at normal-mode execution, for
33846 example, thread races, because debugger's interference with the program's
33847 timing may conceal the bugs. On the other hand, in some applications,
33848 it is not feasible for the debugger to interrupt the program's execution
33849 long enough for the developer to learn anything helpful about its behavior.
33850 If the program's correctness depends on its real-time behavior, delays
33851 introduced by a debugger might cause the program to fail, even when the
33852 code itself is correct. It is useful to be able to observe the program's
33853 behavior without interrupting it.
33855 Therefore, traditional debugging model is too intrusive to reproduce
33856 some bugs. In order to reduce the interference with the program, we can
33857 reduce the number of operations performed by debugger. The
33858 @dfn{In-Process Agent}, a shared library, is running within the same
33859 process with inferior, and is able to perform some debugging operations
33860 itself. As a result, debugger is only involved when necessary, and
33861 performance of debugging can be improved accordingly. Note that
33862 interference with program can be reduced but can't be removed completely,
33863 because the in-process agent will still stop or slow down the program.
33865 The in-process agent can interpret and execute Agent Expressions
33866 (@pxref{Agent Expressions}) during performing debugging operations. The
33867 agent expressions can be used for different purposes, such as collecting
33868 data in tracepoints, and condition evaluation in breakpoints.
33870 @anchor{Control Agent}
33871 You can control whether the in-process agent is used as an aid for
33872 debugging with the following commands:
33875 @kindex set agent on
33877 Causes the in-process agent to perform some operations on behalf of the
33878 debugger. Just which operations requested by the user will be done
33879 by the in-process agent depends on the its capabilities. For example,
33880 if you request to evaluate breakpoint conditions in the in-process agent,
33881 and the in-process agent has such capability as well, then breakpoint
33882 conditions will be evaluated in the in-process agent.
33884 @kindex set agent off
33885 @item set agent off
33886 Disables execution of debugging operations by the in-process agent. All
33887 of the operations will be performed by @value{GDBN}.
33891 Display the current setting of execution of debugging operations by
33892 the in-process agent.
33896 * In-Process Agent Protocol::
33899 @node In-Process Agent Protocol
33900 @section In-Process Agent Protocol
33901 @cindex in-process agent protocol
33903 The in-process agent is able to communicate with both @value{GDBN} and
33904 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33905 used for communications between @value{GDBN} or GDBserver and the IPA.
33906 In general, @value{GDBN} or GDBserver sends commands
33907 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33908 in-process agent replies back with the return result of the command, or
33909 some other information. The data sent to in-process agent is composed
33910 of primitive data types, such as 4-byte or 8-byte type, and composite
33911 types, which are called objects (@pxref{IPA Protocol Objects}).
33914 * IPA Protocol Objects::
33915 * IPA Protocol Commands::
33918 @node IPA Protocol Objects
33919 @subsection IPA Protocol Objects
33920 @cindex ipa protocol objects
33922 The commands sent to and results received from agent may contain some
33923 complex data types called @dfn{objects}.
33925 The in-process agent is running on the same machine with @value{GDBN}
33926 or GDBserver, so it doesn't have to handle as much differences between
33927 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33928 However, there are still some differences of two ends in two processes:
33932 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33933 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33935 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33936 GDBserver is compiled with one, and in-process agent is compiled with
33940 Here are the IPA Protocol Objects:
33944 agent expression object. It represents an agent expression
33945 (@pxref{Agent Expressions}).
33946 @anchor{agent expression object}
33948 tracepoint action object. It represents a tracepoint action
33949 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33950 memory, static trace data and to evaluate expression.
33951 @anchor{tracepoint action object}
33953 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33954 @anchor{tracepoint object}
33958 The following table describes important attributes of each IPA protocol
33961 @multitable @columnfractions .30 .20 .50
33962 @headitem Name @tab Size @tab Description
33963 @item @emph{agent expression object} @tab @tab
33964 @item length @tab 4 @tab length of bytes code
33965 @item byte code @tab @var{length} @tab contents of byte code
33966 @item @emph{tracepoint action for collecting memory} @tab @tab
33967 @item 'M' @tab 1 @tab type of tracepoint action
33968 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33969 address of the lowest byte to collect, otherwise @var{addr} is the offset
33970 of @var{basereg} for memory collecting.
33971 @item len @tab 8 @tab length of memory for collecting
33972 @item basereg @tab 4 @tab the register number containing the starting
33973 memory address for collecting.
33974 @item @emph{tracepoint action for collecting registers} @tab @tab
33975 @item 'R' @tab 1 @tab type of tracepoint action
33976 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33977 @item 'L' @tab 1 @tab type of tracepoint action
33978 @item @emph{tracepoint action for expression evaluation} @tab @tab
33979 @item 'X' @tab 1 @tab type of tracepoint action
33980 @item agent expression @tab length of @tab @ref{agent expression object}
33981 @item @emph{tracepoint object} @tab @tab
33982 @item number @tab 4 @tab number of tracepoint
33983 @item address @tab 8 @tab address of tracepoint inserted on
33984 @item type @tab 4 @tab type of tracepoint
33985 @item enabled @tab 1 @tab enable or disable of tracepoint
33986 @item step_count @tab 8 @tab step
33987 @item pass_count @tab 8 @tab pass
33988 @item numactions @tab 4 @tab number of tracepoint actions
33989 @item hit count @tab 8 @tab hit count
33990 @item trace frame usage @tab 8 @tab trace frame usage
33991 @item compiled_cond @tab 8 @tab compiled condition
33992 @item orig_size @tab 8 @tab orig size
33993 @item condition @tab 4 if condition is NULL otherwise length of
33994 @ref{agent expression object}
33995 @tab zero if condition is NULL, otherwise is
33996 @ref{agent expression object}
33997 @item actions @tab variable
33998 @tab numactions number of @ref{tracepoint action object}
34001 @node IPA Protocol Commands
34002 @subsection IPA Protocol Commands
34003 @cindex ipa protocol commands
34005 The spaces in each command are delimiters to ease reading this commands
34006 specification. They don't exist in real commands.
34010 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34011 Installs a new fast tracepoint described by @var{tracepoint_object}
34012 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34013 head of @dfn{jumppad}, which is used to jump to data collection routine
34018 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34019 @var{target_address} is address of tracepoint in the inferior.
34020 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34021 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34022 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34023 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34030 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34031 is about to kill inferiors.
34039 @item probe_marker_at:@var{address}
34040 Asks in-process agent to probe the marker at @var{address}.
34047 @item unprobe_marker_at:@var{address}
34048 Asks in-process agent to unprobe the marker at @var{address}.
34052 @chapter Reporting Bugs in @value{GDBN}
34053 @cindex bugs in @value{GDBN}
34054 @cindex reporting bugs in @value{GDBN}
34056 Your bug reports play an essential role in making @value{GDBN} reliable.
34058 Reporting a bug may help you by bringing a solution to your problem, or it
34059 may not. But in any case the principal function of a bug report is to help
34060 the entire community by making the next version of @value{GDBN} work better. Bug
34061 reports are your contribution to the maintenance of @value{GDBN}.
34063 In order for a bug report to serve its purpose, you must include the
34064 information that enables us to fix the bug.
34067 * Bug Criteria:: Have you found a bug?
34068 * Bug Reporting:: How to report bugs
34072 @section Have You Found a Bug?
34073 @cindex bug criteria
34075 If you are not sure whether you have found a bug, here are some guidelines:
34078 @cindex fatal signal
34079 @cindex debugger crash
34080 @cindex crash of debugger
34082 If the debugger gets a fatal signal, for any input whatever, that is a
34083 @value{GDBN} bug. Reliable debuggers never crash.
34085 @cindex error on valid input
34087 If @value{GDBN} produces an error message for valid input, that is a
34088 bug. (Note that if you're cross debugging, the problem may also be
34089 somewhere in the connection to the target.)
34091 @cindex invalid input
34093 If @value{GDBN} does not produce an error message for invalid input,
34094 that is a bug. However, you should note that your idea of
34095 ``invalid input'' might be our idea of ``an extension'' or ``support
34096 for traditional practice''.
34099 If you are an experienced user of debugging tools, your suggestions
34100 for improvement of @value{GDBN} are welcome in any case.
34103 @node Bug Reporting
34104 @section How to Report Bugs
34105 @cindex bug reports
34106 @cindex @value{GDBN} bugs, reporting
34108 A number of companies and individuals offer support for @sc{gnu} products.
34109 If you obtained @value{GDBN} from a support organization, we recommend you
34110 contact that organization first.
34112 You can find contact information for many support companies and
34113 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34115 @c should add a web page ref...
34118 @ifset BUGURL_DEFAULT
34119 In any event, we also recommend that you submit bug reports for
34120 @value{GDBN}. The preferred method is to submit them directly using
34121 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34122 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34125 @strong{Do not send bug reports to @samp{info-gdb}, or to
34126 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34127 not want to receive bug reports. Those that do have arranged to receive
34130 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34131 serves as a repeater. The mailing list and the newsgroup carry exactly
34132 the same messages. Often people think of posting bug reports to the
34133 newsgroup instead of mailing them. This appears to work, but it has one
34134 problem which can be crucial: a newsgroup posting often lacks a mail
34135 path back to the sender. Thus, if we need to ask for more information,
34136 we may be unable to reach you. For this reason, it is better to send
34137 bug reports to the mailing list.
34139 @ifclear BUGURL_DEFAULT
34140 In any event, we also recommend that you submit bug reports for
34141 @value{GDBN} to @value{BUGURL}.
34145 The fundamental principle of reporting bugs usefully is this:
34146 @strong{report all the facts}. If you are not sure whether to state a
34147 fact or leave it out, state it!
34149 Often people omit facts because they think they know what causes the
34150 problem and assume that some details do not matter. Thus, you might
34151 assume that the name of the variable you use in an example does not matter.
34152 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34153 stray memory reference which happens to fetch from the location where that
34154 name is stored in memory; perhaps, if the name were different, the contents
34155 of that location would fool the debugger into doing the right thing despite
34156 the bug. Play it safe and give a specific, complete example. That is the
34157 easiest thing for you to do, and the most helpful.
34159 Keep in mind that the purpose of a bug report is to enable us to fix the
34160 bug. It may be that the bug has been reported previously, but neither
34161 you nor we can know that unless your bug report is complete and
34164 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34165 bell?'' Those bug reports are useless, and we urge everyone to
34166 @emph{refuse to respond to them} except to chide the sender to report
34169 To enable us to fix the bug, you should include all these things:
34173 The version of @value{GDBN}. @value{GDBN} announces it if you start
34174 with no arguments; you can also print it at any time using @code{show
34177 Without this, we will not know whether there is any point in looking for
34178 the bug in the current version of @value{GDBN}.
34181 The type of machine you are using, and the operating system name and
34185 The details of the @value{GDBN} build-time configuration.
34186 @value{GDBN} shows these details if you invoke it with the
34187 @option{--configuration} command-line option, or if you type
34188 @code{show configuration} at @value{GDBN}'s prompt.
34191 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34192 ``@value{GCC}--2.8.1''.
34195 What compiler (and its version) was used to compile the program you are
34196 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34197 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34198 to get this information; for other compilers, see the documentation for
34202 The command arguments you gave the compiler to compile your example and
34203 observe the bug. For example, did you use @samp{-O}? To guarantee
34204 you will not omit something important, list them all. A copy of the
34205 Makefile (or the output from make) is sufficient.
34207 If we were to try to guess the arguments, we would probably guess wrong
34208 and then we might not encounter the bug.
34211 A complete input script, and all necessary source files, that will
34215 A description of what behavior you observe that you believe is
34216 incorrect. For example, ``It gets a fatal signal.''
34218 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34219 will certainly notice it. But if the bug is incorrect output, we might
34220 not notice unless it is glaringly wrong. You might as well not give us
34221 a chance to make a mistake.
34223 Even if the problem you experience is a fatal signal, you should still
34224 say so explicitly. Suppose something strange is going on, such as, your
34225 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34226 the C library on your system. (This has happened!) Your copy might
34227 crash and ours would not. If you told us to expect a crash, then when
34228 ours fails to crash, we would know that the bug was not happening for
34229 us. If you had not told us to expect a crash, then we would not be able
34230 to draw any conclusion from our observations.
34233 @cindex recording a session script
34234 To collect all this information, you can use a session recording program
34235 such as @command{script}, which is available on many Unix systems.
34236 Just run your @value{GDBN} session inside @command{script} and then
34237 include the @file{typescript} file with your bug report.
34239 Another way to record a @value{GDBN} session is to run @value{GDBN}
34240 inside Emacs and then save the entire buffer to a file.
34243 If you wish to suggest changes to the @value{GDBN} source, send us context
34244 diffs. If you even discuss something in the @value{GDBN} source, refer to
34245 it by context, not by line number.
34247 The line numbers in our development sources will not match those in your
34248 sources. Your line numbers would convey no useful information to us.
34252 Here are some things that are not necessary:
34256 A description of the envelope of the bug.
34258 Often people who encounter a bug spend a lot of time investigating
34259 which changes to the input file will make the bug go away and which
34260 changes will not affect it.
34262 This is often time consuming and not very useful, because the way we
34263 will find the bug is by running a single example under the debugger
34264 with breakpoints, not by pure deduction from a series of examples.
34265 We recommend that you save your time for something else.
34267 Of course, if you can find a simpler example to report @emph{instead}
34268 of the original one, that is a convenience for us. Errors in the
34269 output will be easier to spot, running under the debugger will take
34270 less time, and so on.
34272 However, simplification is not vital; if you do not want to do this,
34273 report the bug anyway and send us the entire test case you used.
34276 A patch for the bug.
34278 A patch for the bug does help us if it is a good one. But do not omit
34279 the necessary information, such as the test case, on the assumption that
34280 a patch is all we need. We might see problems with your patch and decide
34281 to fix the problem another way, or we might not understand it at all.
34283 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34284 construct an example that will make the program follow a certain path
34285 through the code. If you do not send us the example, we will not be able
34286 to construct one, so we will not be able to verify that the bug is fixed.
34288 And if we cannot understand what bug you are trying to fix, or why your
34289 patch should be an improvement, we will not install it. A test case will
34290 help us to understand.
34293 A guess about what the bug is or what it depends on.
34295 Such guesses are usually wrong. Even we cannot guess right about such
34296 things without first using the debugger to find the facts.
34299 @c The readline documentation is distributed with the readline code
34300 @c and consists of the two following files:
34303 @c Use -I with makeinfo to point to the appropriate directory,
34304 @c environment var TEXINPUTS with TeX.
34305 @ifclear SYSTEM_READLINE
34306 @include rluser.texi
34307 @include hsuser.texi
34311 @appendix In Memoriam
34313 The @value{GDBN} project mourns the loss of the following long-time
34318 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34319 to Free Software in general. Outside of @value{GDBN}, he was known in
34320 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34322 @item Michael Snyder
34323 Michael was one of the Global Maintainers of the @value{GDBN} project,
34324 with contributions recorded as early as 1996, until 2011. In addition
34325 to his day to day participation, he was a large driving force behind
34326 adding Reverse Debugging to @value{GDBN}.
34329 Beyond their technical contributions to the project, they were also
34330 enjoyable members of the Free Software Community. We will miss them.
34332 @node Formatting Documentation
34333 @appendix Formatting Documentation
34335 @cindex @value{GDBN} reference card
34336 @cindex reference card
34337 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34338 for printing with PostScript or Ghostscript, in the @file{gdb}
34339 subdirectory of the main source directory@footnote{In
34340 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34341 release.}. If you can use PostScript or Ghostscript with your printer,
34342 you can print the reference card immediately with @file{refcard.ps}.
34344 The release also includes the source for the reference card. You
34345 can format it, using @TeX{}, by typing:
34351 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34352 mode on US ``letter'' size paper;
34353 that is, on a sheet 11 inches wide by 8.5 inches
34354 high. You will need to specify this form of printing as an option to
34355 your @sc{dvi} output program.
34357 @cindex documentation
34359 All the documentation for @value{GDBN} comes as part of the machine-readable
34360 distribution. The documentation is written in Texinfo format, which is
34361 a documentation system that uses a single source file to produce both
34362 on-line information and a printed manual. You can use one of the Info
34363 formatting commands to create the on-line version of the documentation
34364 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34366 @value{GDBN} includes an already formatted copy of the on-line Info
34367 version of this manual in the @file{gdb} subdirectory. The main Info
34368 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34369 subordinate files matching @samp{gdb.info*} in the same directory. If
34370 necessary, you can print out these files, or read them with any editor;
34371 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34372 Emacs or the standalone @code{info} program, available as part of the
34373 @sc{gnu} Texinfo distribution.
34375 If you want to format these Info files yourself, you need one of the
34376 Info formatting programs, such as @code{texinfo-format-buffer} or
34379 If you have @code{makeinfo} installed, and are in the top level
34380 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34381 version @value{GDBVN}), you can make the Info file by typing:
34388 If you want to typeset and print copies of this manual, you need @TeX{},
34389 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34390 Texinfo definitions file.
34392 @TeX{} is a typesetting program; it does not print files directly, but
34393 produces output files called @sc{dvi} files. To print a typeset
34394 document, you need a program to print @sc{dvi} files. If your system
34395 has @TeX{} installed, chances are it has such a program. The precise
34396 command to use depends on your system; @kbd{lpr -d} is common; another
34397 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34398 require a file name without any extension or a @samp{.dvi} extension.
34400 @TeX{} also requires a macro definitions file called
34401 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34402 written in Texinfo format. On its own, @TeX{} cannot either read or
34403 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34404 and is located in the @file{gdb-@var{version-number}/texinfo}
34407 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34408 typeset and print this manual. First switch to the @file{gdb}
34409 subdirectory of the main source directory (for example, to
34410 @file{gdb-@value{GDBVN}/gdb}) and type:
34416 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34418 @node Installing GDB
34419 @appendix Installing @value{GDBN}
34420 @cindex installation
34423 * Requirements:: Requirements for building @value{GDBN}
34424 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34425 * Separate Objdir:: Compiling @value{GDBN} in another directory
34426 * Config Names:: Specifying names for hosts and targets
34427 * Configure Options:: Summary of options for configure
34428 * System-wide configuration:: Having a system-wide init file
34432 @section Requirements for Building @value{GDBN}
34433 @cindex building @value{GDBN}, requirements for
34435 Building @value{GDBN} requires various tools and packages to be available.
34436 Other packages will be used only if they are found.
34438 @heading Tools/Packages Necessary for Building @value{GDBN}
34440 @item ISO C90 compiler
34441 @value{GDBN} is written in ISO C90. It should be buildable with any
34442 working C90 compiler, e.g.@: GCC.
34446 @heading Tools/Packages Optional for Building @value{GDBN}
34450 @value{GDBN} can use the Expat XML parsing library. This library may be
34451 included with your operating system distribution; if it is not, you
34452 can get the latest version from @url{http://expat.sourceforge.net}.
34453 The @file{configure} script will search for this library in several
34454 standard locations; if it is installed in an unusual path, you can
34455 use the @option{--with-libexpat-prefix} option to specify its location.
34461 Remote protocol memory maps (@pxref{Memory Map Format})
34463 Target descriptions (@pxref{Target Descriptions})
34465 Remote shared library lists (@xref{Library List Format},
34466 or alternatively @pxref{Library List Format for SVR4 Targets})
34468 MS-Windows shared libraries (@pxref{Shared Libraries})
34470 Traceframe info (@pxref{Traceframe Info Format})
34472 Branch trace (@pxref{Branch Trace Format},
34473 @pxref{Branch Trace Configuration Format})
34478 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34479 library. This library may be included with your operating system
34480 distribution; if it is not, you can get the latest version from
34481 @url{http://www.mpfr.org}. The @file{configure} script will search
34482 for this library in several standard locations; if it is installed
34483 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34484 option to specify its location.
34486 GNU MPFR is used to emulate target floating-point arithmetic during
34487 expression evaluation when the target uses different floating-point
34488 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34489 will fall back to using host floating-point arithmetic.
34492 @cindex compressed debug sections
34493 @value{GDBN} will use the @samp{zlib} library, if available, to read
34494 compressed debug sections. Some linkers, such as GNU gold, are capable
34495 of producing binaries with compressed debug sections. If @value{GDBN}
34496 is compiled with @samp{zlib}, it will be able to read the debug
34497 information in such binaries.
34499 The @samp{zlib} library is likely included with your operating system
34500 distribution; if it is not, you can get the latest version from
34501 @url{http://zlib.net}.
34504 @value{GDBN}'s features related to character sets (@pxref{Character
34505 Sets}) require a functioning @code{iconv} implementation. If you are
34506 on a GNU system, then this is provided by the GNU C Library. Some
34507 other systems also provide a working @code{iconv}.
34509 If @value{GDBN} is using the @code{iconv} program which is installed
34510 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34511 This is done with @option{--with-iconv-bin} which specifies the
34512 directory that contains the @code{iconv} program.
34514 On systems without @code{iconv}, you can install GNU Libiconv. If you
34515 have previously installed Libiconv, you can use the
34516 @option{--with-libiconv-prefix} option to configure.
34518 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34519 arrange to build Libiconv if a directory named @file{libiconv} appears
34520 in the top-most source directory. If Libiconv is built this way, and
34521 if the operating system does not provide a suitable @code{iconv}
34522 implementation, then the just-built library will automatically be used
34523 by @value{GDBN}. One easy way to set this up is to download GNU
34524 Libiconv, unpack it, and then rename the directory holding the
34525 Libiconv source code to @samp{libiconv}.
34528 @node Running Configure
34529 @section Invoking the @value{GDBN} @file{configure} Script
34530 @cindex configuring @value{GDBN}
34531 @value{GDBN} comes with a @file{configure} script that automates the process
34532 of preparing @value{GDBN} for installation; you can then use @code{make} to
34533 build the @code{gdb} program.
34535 @c irrelevant in info file; it's as current as the code it lives with.
34536 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34537 look at the @file{README} file in the sources; we may have improved the
34538 installation procedures since publishing this manual.}
34541 The @value{GDBN} distribution includes all the source code you need for
34542 @value{GDBN} in a single directory, whose name is usually composed by
34543 appending the version number to @samp{gdb}.
34545 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34546 @file{gdb-@value{GDBVN}} directory. That directory contains:
34549 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34550 script for configuring @value{GDBN} and all its supporting libraries
34552 @item gdb-@value{GDBVN}/gdb
34553 the source specific to @value{GDBN} itself
34555 @item gdb-@value{GDBVN}/bfd
34556 source for the Binary File Descriptor library
34558 @item gdb-@value{GDBVN}/include
34559 @sc{gnu} include files
34561 @item gdb-@value{GDBVN}/libiberty
34562 source for the @samp{-liberty} free software library
34564 @item gdb-@value{GDBVN}/opcodes
34565 source for the library of opcode tables and disassemblers
34567 @item gdb-@value{GDBVN}/readline
34568 source for the @sc{gnu} command-line interface
34570 @item gdb-@value{GDBVN}/glob
34571 source for the @sc{gnu} filename pattern-matching subroutine
34573 @item gdb-@value{GDBVN}/mmalloc
34574 source for the @sc{gnu} memory-mapped malloc package
34577 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34578 from the @file{gdb-@var{version-number}} source directory, which in
34579 this example is the @file{gdb-@value{GDBVN}} directory.
34581 First switch to the @file{gdb-@var{version-number}} source directory
34582 if you are not already in it; then run @file{configure}. Pass the
34583 identifier for the platform on which @value{GDBN} will run as an
34589 cd gdb-@value{GDBVN}
34590 ./configure @var{host}
34595 where @var{host} is an identifier such as @samp{sun4} or
34596 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34597 (You can often leave off @var{host}; @file{configure} tries to guess the
34598 correct value by examining your system.)
34600 Running @samp{configure @var{host}} and then running @code{make} builds the
34601 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34602 libraries, then @code{gdb} itself. The configured source files, and the
34603 binaries, are left in the corresponding source directories.
34606 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34607 system does not recognize this automatically when you run a different
34608 shell, you may need to run @code{sh} on it explicitly:
34611 sh configure @var{host}
34614 If you run @file{configure} from a directory that contains source
34615 directories for multiple libraries or programs, such as the
34616 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34618 creates configuration files for every directory level underneath (unless
34619 you tell it not to, with the @samp{--norecursion} option).
34621 You should run the @file{configure} script from the top directory in the
34622 source tree, the @file{gdb-@var{version-number}} directory. If you run
34623 @file{configure} from one of the subdirectories, you will configure only
34624 that subdirectory. That is usually not what you want. In particular,
34625 if you run the first @file{configure} from the @file{gdb} subdirectory
34626 of the @file{gdb-@var{version-number}} directory, you will omit the
34627 configuration of @file{bfd}, @file{readline}, and other sibling
34628 directories of the @file{gdb} subdirectory. This leads to build errors
34629 about missing include files such as @file{bfd/bfd.h}.
34631 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34632 However, you should make sure that the shell on your path (named by
34633 the @samp{SHELL} environment variable) is publicly readable. Remember
34634 that @value{GDBN} uses the shell to start your program---some systems refuse to
34635 let @value{GDBN} debug child processes whose programs are not readable.
34637 @node Separate Objdir
34638 @section Compiling @value{GDBN} in Another Directory
34640 If you want to run @value{GDBN} versions for several host or target machines,
34641 you need a different @code{gdb} compiled for each combination of
34642 host and target. @file{configure} is designed to make this easy by
34643 allowing you to generate each configuration in a separate subdirectory,
34644 rather than in the source directory. If your @code{make} program
34645 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34646 @code{make} in each of these directories builds the @code{gdb}
34647 program specified there.
34649 To build @code{gdb} in a separate directory, run @file{configure}
34650 with the @samp{--srcdir} option to specify where to find the source.
34651 (You also need to specify a path to find @file{configure}
34652 itself from your working directory. If the path to @file{configure}
34653 would be the same as the argument to @samp{--srcdir}, you can leave out
34654 the @samp{--srcdir} option; it is assumed.)
34656 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34657 separate directory for a Sun 4 like this:
34661 cd gdb-@value{GDBVN}
34664 ../gdb-@value{GDBVN}/configure sun4
34669 When @file{configure} builds a configuration using a remote source
34670 directory, it creates a tree for the binaries with the same structure
34671 (and using the same names) as the tree under the source directory. In
34672 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34673 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34674 @file{gdb-sun4/gdb}.
34676 Make sure that your path to the @file{configure} script has just one
34677 instance of @file{gdb} in it. If your path to @file{configure} looks
34678 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34679 one subdirectory of @value{GDBN}, not the whole package. This leads to
34680 build errors about missing include files such as @file{bfd/bfd.h}.
34682 One popular reason to build several @value{GDBN} configurations in separate
34683 directories is to configure @value{GDBN} for cross-compiling (where
34684 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34685 programs that run on another machine---the @dfn{target}).
34686 You specify a cross-debugging target by
34687 giving the @samp{--target=@var{target}} option to @file{configure}.
34689 When you run @code{make} to build a program or library, you must run
34690 it in a configured directory---whatever directory you were in when you
34691 called @file{configure} (or one of its subdirectories).
34693 The @code{Makefile} that @file{configure} generates in each source
34694 directory also runs recursively. If you type @code{make} in a source
34695 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34696 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34697 will build all the required libraries, and then build GDB.
34699 When you have multiple hosts or targets configured in separate
34700 directories, you can run @code{make} on them in parallel (for example,
34701 if they are NFS-mounted on each of the hosts); they will not interfere
34705 @section Specifying Names for Hosts and Targets
34707 The specifications used for hosts and targets in the @file{configure}
34708 script are based on a three-part naming scheme, but some short predefined
34709 aliases are also supported. The full naming scheme encodes three pieces
34710 of information in the following pattern:
34713 @var{architecture}-@var{vendor}-@var{os}
34716 For example, you can use the alias @code{sun4} as a @var{host} argument,
34717 or as the value for @var{target} in a @code{--target=@var{target}}
34718 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34720 The @file{configure} script accompanying @value{GDBN} does not provide
34721 any query facility to list all supported host and target names or
34722 aliases. @file{configure} calls the Bourne shell script
34723 @code{config.sub} to map abbreviations to full names; you can read the
34724 script, if you wish, or you can use it to test your guesses on
34725 abbreviations---for example:
34728 % sh config.sub i386-linux
34730 % sh config.sub alpha-linux
34731 alpha-unknown-linux-gnu
34732 % sh config.sub hp9k700
34734 % sh config.sub sun4
34735 sparc-sun-sunos4.1.1
34736 % sh config.sub sun3
34737 m68k-sun-sunos4.1.1
34738 % sh config.sub i986v
34739 Invalid configuration `i986v': machine `i986v' not recognized
34743 @code{config.sub} is also distributed in the @value{GDBN} source
34744 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34746 @node Configure Options
34747 @section @file{configure} Options
34749 Here is a summary of the @file{configure} options and arguments that
34750 are most often useful for building @value{GDBN}. @file{configure} also has
34751 several other options not listed here. @inforef{What Configure
34752 Does,,configure.info}, for a full explanation of @file{configure}.
34755 configure @r{[}--help@r{]}
34756 @r{[}--prefix=@var{dir}@r{]}
34757 @r{[}--exec-prefix=@var{dir}@r{]}
34758 @r{[}--srcdir=@var{dirname}@r{]}
34759 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34760 @r{[}--target=@var{target}@r{]}
34765 You may introduce options with a single @samp{-} rather than
34766 @samp{--} if you prefer; but you may abbreviate option names if you use
34771 Display a quick summary of how to invoke @file{configure}.
34773 @item --prefix=@var{dir}
34774 Configure the source to install programs and files under directory
34777 @item --exec-prefix=@var{dir}
34778 Configure the source to install programs under directory
34781 @c avoid splitting the warning from the explanation:
34783 @item --srcdir=@var{dirname}
34784 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34785 @code{make} that implements the @code{VPATH} feature.}@*
34786 Use this option to make configurations in directories separate from the
34787 @value{GDBN} source directories. Among other things, you can use this to
34788 build (or maintain) several configurations simultaneously, in separate
34789 directories. @file{configure} writes configuration-specific files in
34790 the current directory, but arranges for them to use the source in the
34791 directory @var{dirname}. @file{configure} creates directories under
34792 the working directory in parallel to the source directories below
34795 @item --norecursion
34796 Configure only the directory level where @file{configure} is executed; do not
34797 propagate configuration to subdirectories.
34799 @item --target=@var{target}
34800 Configure @value{GDBN} for cross-debugging programs running on the specified
34801 @var{target}. Without this option, @value{GDBN} is configured to debug
34802 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34804 There is no convenient way to generate a list of all available targets.
34806 @item @var{host} @dots{}
34807 Configure @value{GDBN} to run on the specified @var{host}.
34809 There is no convenient way to generate a list of all available hosts.
34812 There are many other options available as well, but they are generally
34813 needed for special purposes only.
34815 @node System-wide configuration
34816 @section System-wide configuration and settings
34817 @cindex system-wide init file
34819 @value{GDBN} can be configured to have a system-wide init file;
34820 this file will be read and executed at startup (@pxref{Startup, , What
34821 @value{GDBN} does during startup}).
34823 Here is the corresponding configure option:
34826 @item --with-system-gdbinit=@var{file}
34827 Specify that the default location of the system-wide init file is
34831 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34832 it may be subject to relocation. Two possible cases:
34836 If the default location of this init file contains @file{$prefix},
34837 it will be subject to relocation. Suppose that the configure options
34838 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34839 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34840 init file is looked for as @file{$install/etc/gdbinit} instead of
34841 @file{$prefix/etc/gdbinit}.
34844 By contrast, if the default location does not contain the prefix,
34845 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34846 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34847 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34848 wherever @value{GDBN} is installed.
34851 If the configured location of the system-wide init file (as given by the
34852 @option{--with-system-gdbinit} option at configure time) is in the
34853 data-directory (as specified by @option{--with-gdb-datadir} at configure
34854 time) or in one of its subdirectories, then @value{GDBN} will look for the
34855 system-wide init file in the directory specified by the
34856 @option{--data-directory} command-line option.
34857 Note that the system-wide init file is only read once, during @value{GDBN}
34858 initialization. If the data-directory is changed after @value{GDBN} has
34859 started with the @code{set data-directory} command, the file will not be
34863 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34866 @node System-wide Configuration Scripts
34867 @subsection Installed System-wide Configuration Scripts
34868 @cindex system-wide configuration scripts
34870 The @file{system-gdbinit} directory, located inside the data-directory
34871 (as specified by @option{--with-gdb-datadir} at configure time) contains
34872 a number of scripts which can be used as system-wide init files. To
34873 automatically source those scripts at startup, @value{GDBN} should be
34874 configured with @option{--with-system-gdbinit}. Otherwise, any user
34875 should be able to source them by hand as needed.
34877 The following scripts are currently available:
34880 @item @file{elinos.py}
34882 @cindex ELinOS system-wide configuration script
34883 This script is useful when debugging a program on an ELinOS target.
34884 It takes advantage of the environment variables defined in a standard
34885 ELinOS environment in order to determine the location of the system
34886 shared libraries, and then sets the @samp{solib-absolute-prefix}
34887 and @samp{solib-search-path} variables appropriately.
34889 @item @file{wrs-linux.py}
34890 @pindex wrs-linux.py
34891 @cindex Wind River Linux system-wide configuration script
34892 This script is useful when debugging a program on a target running
34893 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34894 the host-side sysroot used by the target system.
34898 @node Maintenance Commands
34899 @appendix Maintenance Commands
34900 @cindex maintenance commands
34901 @cindex internal commands
34903 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34904 includes a number of commands intended for @value{GDBN} developers,
34905 that are not documented elsewhere in this manual. These commands are
34906 provided here for reference. (For commands that turn on debugging
34907 messages, see @ref{Debugging Output}.)
34910 @kindex maint agent
34911 @kindex maint agent-eval
34912 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34913 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34914 Translate the given @var{expression} into remote agent bytecodes.
34915 This command is useful for debugging the Agent Expression mechanism
34916 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34917 expression useful for data collection, such as by tracepoints, while
34918 @samp{maint agent-eval} produces an expression that evaluates directly
34919 to a result. For instance, a collection expression for @code{globa +
34920 globb} will include bytecodes to record four bytes of memory at each
34921 of the addresses of @code{globa} and @code{globb}, while discarding
34922 the result of the addition, while an evaluation expression will do the
34923 addition and return the sum.
34924 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34925 If not, generate remote agent bytecode for current frame PC address.
34927 @kindex maint agent-printf
34928 @item maint agent-printf @var{format},@var{expr},...
34929 Translate the given format string and list of argument expressions
34930 into remote agent bytecodes and display them as a disassembled list.
34931 This command is useful for debugging the agent version of dynamic
34932 printf (@pxref{Dynamic Printf}).
34934 @kindex maint info breakpoints
34935 @item @anchor{maint info breakpoints}maint info breakpoints
34936 Using the same format as @samp{info breakpoints}, display both the
34937 breakpoints you've set explicitly, and those @value{GDBN} is using for
34938 internal purposes. Internal breakpoints are shown with negative
34939 breakpoint numbers. The type column identifies what kind of breakpoint
34944 Normal, explicitly set breakpoint.
34947 Normal, explicitly set watchpoint.
34950 Internal breakpoint, used to handle correctly stepping through
34951 @code{longjmp} calls.
34953 @item longjmp resume
34954 Internal breakpoint at the target of a @code{longjmp}.
34957 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34960 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34963 Shared library events.
34967 @kindex maint info btrace
34968 @item maint info btrace
34969 Pint information about raw branch tracing data.
34971 @kindex maint btrace packet-history
34972 @item maint btrace packet-history
34973 Print the raw branch trace packets that are used to compute the
34974 execution history for the @samp{record btrace} command. Both the
34975 information and the format in which it is printed depend on the btrace
34980 For the BTS recording format, print a list of blocks of sequential
34981 code. For each block, the following information is printed:
34985 Newer blocks have higher numbers. The oldest block has number zero.
34986 @item Lowest @samp{PC}
34987 @item Highest @samp{PC}
34991 For the Intel Processor Trace recording format, print a list of
34992 Intel Processor Trace packets. For each packet, the following
34993 information is printed:
34996 @item Packet number
34997 Newer packets have higher numbers. The oldest packet has number zero.
34999 The packet's offset in the trace stream.
35000 @item Packet opcode and payload
35004 @kindex maint btrace clear-packet-history
35005 @item maint btrace clear-packet-history
35006 Discards the cached packet history printed by the @samp{maint btrace
35007 packet-history} command. The history will be computed again when
35010 @kindex maint btrace clear
35011 @item maint btrace clear
35012 Discard the branch trace data. The data will be fetched anew and the
35013 branch trace will be recomputed when needed.
35015 This implicitly truncates the branch trace to a single branch trace
35016 buffer. When updating branch trace incrementally, the branch trace
35017 available to @value{GDBN} may be bigger than a single branch trace
35020 @kindex maint set btrace pt skip-pad
35021 @item maint set btrace pt skip-pad
35022 @kindex maint show btrace pt skip-pad
35023 @item maint show btrace pt skip-pad
35024 Control whether @value{GDBN} will skip PAD packets when computing the
35027 @kindex set displaced-stepping
35028 @kindex show displaced-stepping
35029 @cindex displaced stepping support
35030 @cindex out-of-line single-stepping
35031 @item set displaced-stepping
35032 @itemx show displaced-stepping
35033 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35034 if the target supports it. Displaced stepping is a way to single-step
35035 over breakpoints without removing them from the inferior, by executing
35036 an out-of-line copy of the instruction that was originally at the
35037 breakpoint location. It is also known as out-of-line single-stepping.
35040 @item set displaced-stepping on
35041 If the target architecture supports it, @value{GDBN} will use
35042 displaced stepping to step over breakpoints.
35044 @item set displaced-stepping off
35045 @value{GDBN} will not use displaced stepping to step over breakpoints,
35046 even if such is supported by the target architecture.
35048 @cindex non-stop mode, and @samp{set displaced-stepping}
35049 @item set displaced-stepping auto
35050 This is the default mode. @value{GDBN} will use displaced stepping
35051 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35052 architecture supports displaced stepping.
35055 @kindex maint check-psymtabs
35056 @item maint check-psymtabs
35057 Check the consistency of currently expanded psymtabs versus symtabs.
35058 Use this to check, for example, whether a symbol is in one but not the other.
35060 @kindex maint check-symtabs
35061 @item maint check-symtabs
35062 Check the consistency of currently expanded symtabs.
35064 @kindex maint expand-symtabs
35065 @item maint expand-symtabs [@var{regexp}]
35066 Expand symbol tables.
35067 If @var{regexp} is specified, only expand symbol tables for file
35068 names matching @var{regexp}.
35070 @kindex maint set catch-demangler-crashes
35071 @kindex maint show catch-demangler-crashes
35072 @cindex demangler crashes
35073 @item maint set catch-demangler-crashes [on|off]
35074 @itemx maint show catch-demangler-crashes
35075 Control whether @value{GDBN} should attempt to catch crashes in the
35076 symbol name demangler. The default is to attempt to catch crashes.
35077 If enabled, the first time a crash is caught, a core file is created,
35078 the offending symbol is displayed and the user is presented with the
35079 option to terminate the current session.
35081 @kindex maint cplus first_component
35082 @item maint cplus first_component @var{name}
35083 Print the first C@t{++} class/namespace component of @var{name}.
35085 @kindex maint cplus namespace
35086 @item maint cplus namespace
35087 Print the list of possible C@t{++} namespaces.
35089 @kindex maint deprecate
35090 @kindex maint undeprecate
35091 @cindex deprecated commands
35092 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35093 @itemx maint undeprecate @var{command}
35094 Deprecate or undeprecate the named @var{command}. Deprecated commands
35095 cause @value{GDBN} to issue a warning when you use them. The optional
35096 argument @var{replacement} says which newer command should be used in
35097 favor of the deprecated one; if it is given, @value{GDBN} will mention
35098 the replacement as part of the warning.
35100 @kindex maint dump-me
35101 @item maint dump-me
35102 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35103 Cause a fatal signal in the debugger and force it to dump its core.
35104 This is supported only on systems which support aborting a program
35105 with the @code{SIGQUIT} signal.
35107 @kindex maint internal-error
35108 @kindex maint internal-warning
35109 @kindex maint demangler-warning
35110 @cindex demangler crashes
35111 @item maint internal-error @r{[}@var{message-text}@r{]}
35112 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35113 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35115 Cause @value{GDBN} to call the internal function @code{internal_error},
35116 @code{internal_warning} or @code{demangler_warning} and hence behave
35117 as though an internal problem has been detected. In addition to
35118 reporting the internal problem, these functions give the user the
35119 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35120 and @code{internal_warning}) create a core file of the current
35121 @value{GDBN} session.
35123 These commands take an optional parameter @var{message-text} that is
35124 used as the text of the error or warning message.
35126 Here's an example of using @code{internal-error}:
35129 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35130 @dots{}/maint.c:121: internal-error: testing, 1, 2
35131 A problem internal to GDB has been detected. Further
35132 debugging may prove unreliable.
35133 Quit this debugging session? (y or n) @kbd{n}
35134 Create a core file? (y or n) @kbd{n}
35138 @cindex @value{GDBN} internal error
35139 @cindex internal errors, control of @value{GDBN} behavior
35140 @cindex demangler crashes
35142 @kindex maint set internal-error
35143 @kindex maint show internal-error
35144 @kindex maint set internal-warning
35145 @kindex maint show internal-warning
35146 @kindex maint set demangler-warning
35147 @kindex maint show demangler-warning
35148 @item maint set internal-error @var{action} [ask|yes|no]
35149 @itemx maint show internal-error @var{action}
35150 @itemx maint set internal-warning @var{action} [ask|yes|no]
35151 @itemx maint show internal-warning @var{action}
35152 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35153 @itemx maint show demangler-warning @var{action}
35154 When @value{GDBN} reports an internal problem (error or warning) it
35155 gives the user the opportunity to both quit @value{GDBN} and create a
35156 core file of the current @value{GDBN} session. These commands let you
35157 override the default behaviour for each particular @var{action},
35158 described in the table below.
35162 You can specify that @value{GDBN} should always (yes) or never (no)
35163 quit. The default is to ask the user what to do.
35166 You can specify that @value{GDBN} should always (yes) or never (no)
35167 create a core file. The default is to ask the user what to do. Note
35168 that there is no @code{corefile} option for @code{demangler-warning}:
35169 demangler warnings always create a core file and this cannot be
35173 @kindex maint packet
35174 @item maint packet @var{text}
35175 If @value{GDBN} is talking to an inferior via the serial protocol,
35176 then this command sends the string @var{text} to the inferior, and
35177 displays the response packet. @value{GDBN} supplies the initial
35178 @samp{$} character, the terminating @samp{#} character, and the
35181 @kindex maint print architecture
35182 @item maint print architecture @r{[}@var{file}@r{]}
35183 Print the entire architecture configuration. The optional argument
35184 @var{file} names the file where the output goes.
35186 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35187 @item maint print c-tdesc
35188 Print the target description (@pxref{Target Descriptions}) as
35189 a C source file. By default, the target description is for the current
35190 target, but if the optional argument @var{file} is provided, that file
35191 is used to produce the description. The @var{file} should be an XML
35192 document, of the form described in @ref{Target Description Format}.
35193 The created source file is built into @value{GDBN} when @value{GDBN} is
35194 built again. This command is used by developers after they add or
35195 modify XML target descriptions.
35197 @kindex maint check xml-descriptions
35198 @item maint check xml-descriptions @var{dir}
35199 Check that the target descriptions dynamically created by @value{GDBN}
35200 equal the descriptions created from XML files found in @var{dir}.
35202 @kindex maint print dummy-frames
35203 @item maint print dummy-frames
35204 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35207 (@value{GDBP}) @kbd{b add}
35209 (@value{GDBP}) @kbd{print add(2,3)}
35210 Breakpoint 2, add (a=2, b=3) at @dots{}
35212 The program being debugged stopped while in a function called from GDB.
35214 (@value{GDBP}) @kbd{maint print dummy-frames}
35215 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35219 Takes an optional file parameter.
35221 @kindex maint print registers
35222 @kindex maint print raw-registers
35223 @kindex maint print cooked-registers
35224 @kindex maint print register-groups
35225 @kindex maint print remote-registers
35226 @item maint print registers @r{[}@var{file}@r{]}
35227 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35228 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35229 @itemx maint print register-groups @r{[}@var{file}@r{]}
35230 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35231 Print @value{GDBN}'s internal register data structures.
35233 The command @code{maint print raw-registers} includes the contents of
35234 the raw register cache; the command @code{maint print
35235 cooked-registers} includes the (cooked) value of all registers,
35236 including registers which aren't available on the target nor visible
35237 to user; the command @code{maint print register-groups} includes the
35238 groups that each register is a member of; and the command @code{maint
35239 print remote-registers} includes the remote target's register numbers
35240 and offsets in the `G' packets.
35242 These commands take an optional parameter, a file name to which to
35243 write the information.
35245 @kindex maint print reggroups
35246 @item maint print reggroups @r{[}@var{file}@r{]}
35247 Print @value{GDBN}'s internal register group data structures. The
35248 optional argument @var{file} tells to what file to write the
35251 The register groups info looks like this:
35254 (@value{GDBP}) @kbd{maint print reggroups}
35267 This command forces @value{GDBN} to flush its internal register cache.
35269 @kindex maint print objfiles
35270 @cindex info for known object files
35271 @item maint print objfiles @r{[}@var{regexp}@r{]}
35272 Print a dump of all known object files.
35273 If @var{regexp} is specified, only print object files whose names
35274 match @var{regexp}. For each object file, this command prints its name,
35275 address in memory, and all of its psymtabs and symtabs.
35277 @kindex maint print user-registers
35278 @cindex user registers
35279 @item maint print user-registers
35280 List all currently available @dfn{user registers}. User registers
35281 typically provide alternate names for actual hardware registers. They
35282 include the four ``standard'' registers @code{$fp}, @code{$pc},
35283 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35284 registers can be used in expressions in the same way as the canonical
35285 register names, but only the latter are listed by the @code{info
35286 registers} and @code{maint print registers} commands.
35288 @kindex maint print section-scripts
35289 @cindex info for known .debug_gdb_scripts-loaded scripts
35290 @item maint print section-scripts [@var{regexp}]
35291 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35292 If @var{regexp} is specified, only print scripts loaded by object files
35293 matching @var{regexp}.
35294 For each script, this command prints its name as specified in the objfile,
35295 and the full path if known.
35296 @xref{dotdebug_gdb_scripts section}.
35298 @kindex maint print statistics
35299 @cindex bcache statistics
35300 @item maint print statistics
35301 This command prints, for each object file in the program, various data
35302 about that object file followed by the byte cache (@dfn{bcache})
35303 statistics for the object file. The objfile data includes the number
35304 of minimal, partial, full, and stabs symbols, the number of types
35305 defined by the objfile, the number of as yet unexpanded psym tables,
35306 the number of line tables and string tables, and the amount of memory
35307 used by the various tables. The bcache statistics include the counts,
35308 sizes, and counts of duplicates of all and unique objects, max,
35309 average, and median entry size, total memory used and its overhead and
35310 savings, and various measures of the hash table size and chain
35313 @kindex maint print target-stack
35314 @cindex target stack description
35315 @item maint print target-stack
35316 A @dfn{target} is an interface between the debugger and a particular
35317 kind of file or process. Targets can be stacked in @dfn{strata},
35318 so that more than one target can potentially respond to a request.
35319 In particular, memory accesses will walk down the stack of targets
35320 until they find a target that is interested in handling that particular
35323 This command prints a short description of each layer that was pushed on
35324 the @dfn{target stack}, starting from the top layer down to the bottom one.
35326 @kindex maint print type
35327 @cindex type chain of a data type
35328 @item maint print type @var{expr}
35329 Print the type chain for a type specified by @var{expr}. The argument
35330 can be either a type name or a symbol. If it is a symbol, the type of
35331 that symbol is described. The type chain produced by this command is
35332 a recursive definition of the data type as stored in @value{GDBN}'s
35333 data structures, including its flags and contained types.
35335 @kindex maint selftest
35337 @item maint selftest @r{[}@var{filter}@r{]}
35338 Run any self tests that were compiled in to @value{GDBN}. This will
35339 print a message showing how many tests were run, and how many failed.
35340 If a @var{filter} is passed, only the tests with @var{filter} in their
35343 @kindex "maint info selftests"
35345 @item maint info selftests
35346 List the selftests compiled in to @value{GDBN}.
35348 @kindex maint set dwarf always-disassemble
35349 @kindex maint show dwarf always-disassemble
35350 @item maint set dwarf always-disassemble
35351 @item maint show dwarf always-disassemble
35352 Control the behavior of @code{info address} when using DWARF debugging
35355 The default is @code{off}, which means that @value{GDBN} should try to
35356 describe a variable's location in an easily readable format. When
35357 @code{on}, @value{GDBN} will instead display the DWARF location
35358 expression in an assembly-like format. Note that some locations are
35359 too complex for @value{GDBN} to describe simply; in this case you will
35360 always see the disassembly form.
35362 Here is an example of the resulting disassembly:
35365 (gdb) info addr argc
35366 Symbol "argc" is a complex DWARF expression:
35370 For more information on these expressions, see
35371 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35373 @kindex maint set dwarf max-cache-age
35374 @kindex maint show dwarf max-cache-age
35375 @item maint set dwarf max-cache-age
35376 @itemx maint show dwarf max-cache-age
35377 Control the DWARF compilation unit cache.
35379 @cindex DWARF compilation units cache
35380 In object files with inter-compilation-unit references, such as those
35381 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35382 reader needs to frequently refer to previously read compilation units.
35383 This setting controls how long a compilation unit will remain in the
35384 cache if it is not referenced. A higher limit means that cached
35385 compilation units will be stored in memory longer, and more total
35386 memory will be used. Setting it to zero disables caching, which will
35387 slow down @value{GDBN} startup, but reduce memory consumption.
35389 @kindex maint set profile
35390 @kindex maint show profile
35391 @cindex profiling GDB
35392 @item maint set profile
35393 @itemx maint show profile
35394 Control profiling of @value{GDBN}.
35396 Profiling will be disabled until you use the @samp{maint set profile}
35397 command to enable it. When you enable profiling, the system will begin
35398 collecting timing and execution count data; when you disable profiling or
35399 exit @value{GDBN}, the results will be written to a log file. Remember that
35400 if you use profiling, @value{GDBN} will overwrite the profiling log file
35401 (often called @file{gmon.out}). If you have a record of important profiling
35402 data in a @file{gmon.out} file, be sure to move it to a safe location.
35404 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35405 compiled with the @samp{-pg} compiler option.
35407 @kindex maint set show-debug-regs
35408 @kindex maint show show-debug-regs
35409 @cindex hardware debug registers
35410 @item maint set show-debug-regs
35411 @itemx maint show show-debug-regs
35412 Control whether to show variables that mirror the hardware debug
35413 registers. Use @code{on} to enable, @code{off} to disable. If
35414 enabled, the debug registers values are shown when @value{GDBN} inserts or
35415 removes a hardware breakpoint or watchpoint, and when the inferior
35416 triggers a hardware-assisted breakpoint or watchpoint.
35418 @kindex maint set show-all-tib
35419 @kindex maint show show-all-tib
35420 @item maint set show-all-tib
35421 @itemx maint show show-all-tib
35422 Control whether to show all non zero areas within a 1k block starting
35423 at thread local base, when using the @samp{info w32 thread-information-block}
35426 @kindex maint set target-async
35427 @kindex maint show target-async
35428 @item maint set target-async
35429 @itemx maint show target-async
35430 This controls whether @value{GDBN} targets operate in synchronous or
35431 asynchronous mode (@pxref{Background Execution}). Normally the
35432 default is asynchronous, if it is available; but this can be changed
35433 to more easily debug problems occurring only in synchronous mode.
35435 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35436 @kindex maint show target-non-stop
35437 @item maint set target-non-stop
35438 @itemx maint show target-non-stop
35440 This controls whether @value{GDBN} targets always operate in non-stop
35441 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35442 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35443 if supported by the target.
35446 @item maint set target-non-stop auto
35447 This is the default mode. @value{GDBN} controls the target in
35448 non-stop mode if the target supports it.
35450 @item maint set target-non-stop on
35451 @value{GDBN} controls the target in non-stop mode even if the target
35452 does not indicate support.
35454 @item maint set target-non-stop off
35455 @value{GDBN} does not control the target in non-stop mode even if the
35456 target supports it.
35459 @kindex maint set per-command
35460 @kindex maint show per-command
35461 @item maint set per-command
35462 @itemx maint show per-command
35463 @cindex resources used by commands
35465 @value{GDBN} can display the resources used by each command.
35466 This is useful in debugging performance problems.
35469 @item maint set per-command space [on|off]
35470 @itemx maint show per-command space
35471 Enable or disable the printing of the memory used by GDB for each command.
35472 If enabled, @value{GDBN} will display how much memory each command
35473 took, following the command's own output.
35474 This can also be requested by invoking @value{GDBN} with the
35475 @option{--statistics} command-line switch (@pxref{Mode Options}).
35477 @item maint set per-command time [on|off]
35478 @itemx maint show per-command time
35479 Enable or disable the printing of the execution time of @value{GDBN}
35481 If enabled, @value{GDBN} will display how much time it
35482 took to execute each command, following the command's own output.
35483 Both CPU time and wallclock time are printed.
35484 Printing both is useful when trying to determine whether the cost is
35485 CPU or, e.g., disk/network latency.
35486 Note that the CPU time printed is for @value{GDBN} only, it does not include
35487 the execution time of the inferior because there's no mechanism currently
35488 to compute how much time was spent by @value{GDBN} and how much time was
35489 spent by the program been debugged.
35490 This can also be requested by invoking @value{GDBN} with the
35491 @option{--statistics} command-line switch (@pxref{Mode Options}).
35493 @item maint set per-command symtab [on|off]
35494 @itemx maint show per-command symtab
35495 Enable or disable the printing of basic symbol table statistics
35497 If enabled, @value{GDBN} will display the following information:
35501 number of symbol tables
35503 number of primary symbol tables
35505 number of blocks in the blockvector
35509 @kindex maint space
35510 @cindex memory used by commands
35511 @item maint space @var{value}
35512 An alias for @code{maint set per-command space}.
35513 A non-zero value enables it, zero disables it.
35516 @cindex time of command execution
35517 @item maint time @var{value}
35518 An alias for @code{maint set per-command time}.
35519 A non-zero value enables it, zero disables it.
35521 @kindex maint translate-address
35522 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35523 Find the symbol stored at the location specified by the address
35524 @var{addr} and an optional section name @var{section}. If found,
35525 @value{GDBN} prints the name of the closest symbol and an offset from
35526 the symbol's location to the specified address. This is similar to
35527 the @code{info address} command (@pxref{Symbols}), except that this
35528 command also allows to find symbols in other sections.
35530 If section was not specified, the section in which the symbol was found
35531 is also printed. For dynamically linked executables, the name of
35532 executable or shared library containing the symbol is printed as well.
35536 The following command is useful for non-interactive invocations of
35537 @value{GDBN}, such as in the test suite.
35540 @item set watchdog @var{nsec}
35541 @kindex set watchdog
35542 @cindex watchdog timer
35543 @cindex timeout for commands
35544 Set the maximum number of seconds @value{GDBN} will wait for the
35545 target operation to finish. If this time expires, @value{GDBN}
35546 reports and error and the command is aborted.
35548 @item show watchdog
35549 Show the current setting of the target wait timeout.
35552 @node Remote Protocol
35553 @appendix @value{GDBN} Remote Serial Protocol
35558 * Stop Reply Packets::
35559 * General Query Packets::
35560 * Architecture-Specific Protocol Details::
35561 * Tracepoint Packets::
35562 * Host I/O Packets::
35564 * Notification Packets::
35565 * Remote Non-Stop::
35566 * Packet Acknowledgment::
35568 * File-I/O Remote Protocol Extension::
35569 * Library List Format::
35570 * Library List Format for SVR4 Targets::
35571 * Memory Map Format::
35572 * Thread List Format::
35573 * Traceframe Info Format::
35574 * Branch Trace Format::
35575 * Branch Trace Configuration Format::
35581 There may be occasions when you need to know something about the
35582 protocol---for example, if there is only one serial port to your target
35583 machine, you might want your program to do something special if it
35584 recognizes a packet meant for @value{GDBN}.
35586 In the examples below, @samp{->} and @samp{<-} are used to indicate
35587 transmitted and received data, respectively.
35589 @cindex protocol, @value{GDBN} remote serial
35590 @cindex serial protocol, @value{GDBN} remote
35591 @cindex remote serial protocol
35592 All @value{GDBN} commands and responses (other than acknowledgments
35593 and notifications, see @ref{Notification Packets}) are sent as a
35594 @var{packet}. A @var{packet} is introduced with the character
35595 @samp{$}, the actual @var{packet-data}, and the terminating character
35596 @samp{#} followed by a two-digit @var{checksum}:
35599 @code{$}@var{packet-data}@code{#}@var{checksum}
35603 @cindex checksum, for @value{GDBN} remote
35605 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35606 characters between the leading @samp{$} and the trailing @samp{#} (an
35607 eight bit unsigned checksum).
35609 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35610 specification also included an optional two-digit @var{sequence-id}:
35613 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35616 @cindex sequence-id, for @value{GDBN} remote
35618 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35619 has never output @var{sequence-id}s. Stubs that handle packets added
35620 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35622 When either the host or the target machine receives a packet, the first
35623 response expected is an acknowledgment: either @samp{+} (to indicate
35624 the package was received correctly) or @samp{-} (to request
35628 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35633 The @samp{+}/@samp{-} acknowledgments can be disabled
35634 once a connection is established.
35635 @xref{Packet Acknowledgment}, for details.
35637 The host (@value{GDBN}) sends @var{command}s, and the target (the
35638 debugging stub incorporated in your program) sends a @var{response}. In
35639 the case of step and continue @var{command}s, the response is only sent
35640 when the operation has completed, and the target has again stopped all
35641 threads in all attached processes. This is the default all-stop mode
35642 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35643 execution mode; see @ref{Remote Non-Stop}, for details.
35645 @var{packet-data} consists of a sequence of characters with the
35646 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35649 @cindex remote protocol, field separator
35650 Fields within the packet should be separated using @samp{,} @samp{;} or
35651 @samp{:}. Except where otherwise noted all numbers are represented in
35652 @sc{hex} with leading zeros suppressed.
35654 Implementors should note that prior to @value{GDBN} 5.0, the character
35655 @samp{:} could not appear as the third character in a packet (as it
35656 would potentially conflict with the @var{sequence-id}).
35658 @cindex remote protocol, binary data
35659 @anchor{Binary Data}
35660 Binary data in most packets is encoded either as two hexadecimal
35661 digits per byte of binary data. This allowed the traditional remote
35662 protocol to work over connections which were only seven-bit clean.
35663 Some packets designed more recently assume an eight-bit clean
35664 connection, and use a more efficient encoding to send and receive
35667 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35668 as an escape character. Any escaped byte is transmitted as the escape
35669 character followed by the original character XORed with @code{0x20}.
35670 For example, the byte @code{0x7d} would be transmitted as the two
35671 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35672 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35673 @samp{@}}) must always be escaped. Responses sent by the stub
35674 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35675 is not interpreted as the start of a run-length encoded sequence
35678 Response @var{data} can be run-length encoded to save space.
35679 Run-length encoding replaces runs of identical characters with one
35680 instance of the repeated character, followed by a @samp{*} and a
35681 repeat count. The repeat count is itself sent encoded, to avoid
35682 binary characters in @var{data}: a value of @var{n} is sent as
35683 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35684 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35685 code 32) for a repeat count of 3. (This is because run-length
35686 encoding starts to win for counts 3 or more.) Thus, for example,
35687 @samp{0* } is a run-length encoding of ``0000'': the space character
35688 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35691 The printable characters @samp{#} and @samp{$} or with a numeric value
35692 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35693 seven repeats (@samp{$}) can be expanded using a repeat count of only
35694 five (@samp{"}). For example, @samp{00000000} can be encoded as
35697 The error response returned for some packets includes a two character
35698 error number. That number is not well defined.
35700 @cindex empty response, for unsupported packets
35701 For any @var{command} not supported by the stub, an empty response
35702 (@samp{$#00}) should be returned. That way it is possible to extend the
35703 protocol. A newer @value{GDBN} can tell if a packet is supported based
35706 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35707 commands for register access, and the @samp{m} and @samp{M} commands
35708 for memory access. Stubs that only control single-threaded targets
35709 can implement run control with the @samp{c} (continue), and @samp{s}
35710 (step) commands. Stubs that support multi-threading targets should
35711 support the @samp{vCont} command. All other commands are optional.
35716 The following table provides a complete list of all currently defined
35717 @var{command}s and their corresponding response @var{data}.
35718 @xref{File-I/O Remote Protocol Extension}, for details about the File
35719 I/O extension of the remote protocol.
35721 Each packet's description has a template showing the packet's overall
35722 syntax, followed by an explanation of the packet's meaning. We
35723 include spaces in some of the templates for clarity; these are not
35724 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35725 separate its components. For example, a template like @samp{foo
35726 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35727 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35728 @var{baz}. @value{GDBN} does not transmit a space character between the
35729 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35732 @cindex @var{thread-id}, in remote protocol
35733 @anchor{thread-id syntax}
35734 Several packets and replies include a @var{thread-id} field to identify
35735 a thread. Normally these are positive numbers with a target-specific
35736 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35737 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35740 In addition, the remote protocol supports a multiprocess feature in
35741 which the @var{thread-id} syntax is extended to optionally include both
35742 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35743 The @var{pid} (process) and @var{tid} (thread) components each have the
35744 format described above: a positive number with target-specific
35745 interpretation formatted as a big-endian hex string, literal @samp{-1}
35746 to indicate all processes or threads (respectively), or @samp{0} to
35747 indicate an arbitrary process or thread. Specifying just a process, as
35748 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35749 error to specify all processes but a specific thread, such as
35750 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35751 for those packets and replies explicitly documented to include a process
35752 ID, rather than a @var{thread-id}.
35754 The multiprocess @var{thread-id} syntax extensions are only used if both
35755 @value{GDBN} and the stub report support for the @samp{multiprocess}
35756 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35759 Note that all packet forms beginning with an upper- or lower-case
35760 letter, other than those described here, are reserved for future use.
35762 Here are the packet descriptions.
35767 @cindex @samp{!} packet
35768 @anchor{extended mode}
35769 Enable extended mode. In extended mode, the remote server is made
35770 persistent. The @samp{R} packet is used to restart the program being
35776 The remote target both supports and has enabled extended mode.
35780 @cindex @samp{?} packet
35782 Indicate the reason the target halted. The reply is the same as for
35783 step and continue. This packet has a special interpretation when the
35784 target is in non-stop mode; see @ref{Remote Non-Stop}.
35787 @xref{Stop Reply Packets}, for the reply specifications.
35789 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35790 @cindex @samp{A} packet
35791 Initialized @code{argv[]} array passed into program. @var{arglen}
35792 specifies the number of bytes in the hex encoded byte stream
35793 @var{arg}. See @code{gdbserver} for more details.
35798 The arguments were set.
35804 @cindex @samp{b} packet
35805 (Don't use this packet; its behavior is not well-defined.)
35806 Change the serial line speed to @var{baud}.
35808 JTC: @emph{When does the transport layer state change? When it's
35809 received, or after the ACK is transmitted. In either case, there are
35810 problems if the command or the acknowledgment packet is dropped.}
35812 Stan: @emph{If people really wanted to add something like this, and get
35813 it working for the first time, they ought to modify ser-unix.c to send
35814 some kind of out-of-band message to a specially-setup stub and have the
35815 switch happen "in between" packets, so that from remote protocol's point
35816 of view, nothing actually happened.}
35818 @item B @var{addr},@var{mode}
35819 @cindex @samp{B} packet
35820 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35821 breakpoint at @var{addr}.
35823 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35824 (@pxref{insert breakpoint or watchpoint packet}).
35826 @cindex @samp{bc} packet
35829 Backward continue. Execute the target system in reverse. No parameter.
35830 @xref{Reverse Execution}, for more information.
35833 @xref{Stop Reply Packets}, for the reply specifications.
35835 @cindex @samp{bs} packet
35838 Backward single step. Execute one instruction in reverse. No parameter.
35839 @xref{Reverse Execution}, for more information.
35842 @xref{Stop Reply Packets}, for the reply specifications.
35844 @item c @r{[}@var{addr}@r{]}
35845 @cindex @samp{c} packet
35846 Continue at @var{addr}, which is the address to resume. If @var{addr}
35847 is omitted, resume at current address.
35849 This packet is deprecated for multi-threading support. @xref{vCont
35853 @xref{Stop Reply Packets}, for the reply specifications.
35855 @item C @var{sig}@r{[};@var{addr}@r{]}
35856 @cindex @samp{C} packet
35857 Continue with signal @var{sig} (hex signal number). If
35858 @samp{;@var{addr}} is omitted, resume at same address.
35860 This packet is deprecated for multi-threading support. @xref{vCont
35864 @xref{Stop Reply Packets}, for the reply specifications.
35867 @cindex @samp{d} packet
35870 Don't use this packet; instead, define a general set packet
35871 (@pxref{General Query Packets}).
35875 @cindex @samp{D} packet
35876 The first form of the packet is used to detach @value{GDBN} from the
35877 remote system. It is sent to the remote target
35878 before @value{GDBN} disconnects via the @code{detach} command.
35880 The second form, including a process ID, is used when multiprocess
35881 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35882 detach only a specific process. The @var{pid} is specified as a
35883 big-endian hex string.
35893 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35894 @cindex @samp{F} packet
35895 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35896 This is part of the File-I/O protocol extension. @xref{File-I/O
35897 Remote Protocol Extension}, for the specification.
35900 @anchor{read registers packet}
35901 @cindex @samp{g} packet
35902 Read general registers.
35906 @item @var{XX@dots{}}
35907 Each byte of register data is described by two hex digits. The bytes
35908 with the register are transmitted in target byte order. The size of
35909 each register and their position within the @samp{g} packet are
35910 determined by the @value{GDBN} internal gdbarch functions
35911 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35913 When reading registers from a trace frame (@pxref{Analyze Collected
35914 Data,,Using the Collected Data}), the stub may also return a string of
35915 literal @samp{x}'s in place of the register data digits, to indicate
35916 that the corresponding register has not been collected, thus its value
35917 is unavailable. For example, for an architecture with 4 registers of
35918 4 bytes each, the following reply indicates to @value{GDBN} that
35919 registers 0 and 2 have not been collected, while registers 1 and 3
35920 have been collected, and both have zero value:
35924 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35931 @item G @var{XX@dots{}}
35932 @cindex @samp{G} packet
35933 Write general registers. @xref{read registers packet}, for a
35934 description of the @var{XX@dots{}} data.
35944 @item H @var{op} @var{thread-id}
35945 @cindex @samp{H} packet
35946 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35947 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35948 should be @samp{c} for step and continue operations (note that this
35949 is deprecated, supporting the @samp{vCont} command is a better
35950 option), and @samp{g} for other operations. The thread designator
35951 @var{thread-id} has the format and interpretation described in
35952 @ref{thread-id syntax}.
35963 @c 'H': How restrictive (or permissive) is the thread model. If a
35964 @c thread is selected and stopped, are other threads allowed
35965 @c to continue to execute? As I mentioned above, I think the
35966 @c semantics of each command when a thread is selected must be
35967 @c described. For example:
35969 @c 'g': If the stub supports threads and a specific thread is
35970 @c selected, returns the register block from that thread;
35971 @c otherwise returns current registers.
35973 @c 'G' If the stub supports threads and a specific thread is
35974 @c selected, sets the registers of the register block of
35975 @c that thread; otherwise sets current registers.
35977 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35978 @anchor{cycle step packet}
35979 @cindex @samp{i} packet
35980 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35981 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35982 step starting at that address.
35985 @cindex @samp{I} packet
35986 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35990 @cindex @samp{k} packet
35993 The exact effect of this packet is not specified.
35995 For a bare-metal target, it may power cycle or reset the target
35996 system. For that reason, the @samp{k} packet has no reply.
35998 For a single-process target, it may kill that process if possible.
36000 A multiple-process target may choose to kill just one process, or all
36001 that are under @value{GDBN}'s control. For more precise control, use
36002 the vKill packet (@pxref{vKill packet}).
36004 If the target system immediately closes the connection in response to
36005 @samp{k}, @value{GDBN} does not consider the lack of packet
36006 acknowledgment to be an error, and assumes the kill was successful.
36008 If connected using @kbd{target extended-remote}, and the target does
36009 not close the connection in response to a kill request, @value{GDBN}
36010 probes the target state as if a new connection was opened
36011 (@pxref{? packet}).
36013 @item m @var{addr},@var{length}
36014 @cindex @samp{m} packet
36015 Read @var{length} addressable memory units starting at address @var{addr}
36016 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36017 any particular boundary.
36019 The stub need not use any particular size or alignment when gathering
36020 data from memory for the response; even if @var{addr} is word-aligned
36021 and @var{length} is a multiple of the word size, the stub is free to
36022 use byte accesses, or not. For this reason, this packet may not be
36023 suitable for accessing memory-mapped I/O devices.
36024 @cindex alignment of remote memory accesses
36025 @cindex size of remote memory accesses
36026 @cindex memory, alignment and size of remote accesses
36030 @item @var{XX@dots{}}
36031 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36032 The reply may contain fewer addressable memory units than requested if the
36033 server was able to read only part of the region of memory.
36038 @item M @var{addr},@var{length}:@var{XX@dots{}}
36039 @cindex @samp{M} packet
36040 Write @var{length} addressable memory units starting at address @var{addr}
36041 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36042 byte is transmitted as a two-digit hexadecimal number.
36049 for an error (this includes the case where only part of the data was
36054 @cindex @samp{p} packet
36055 Read the value of register @var{n}; @var{n} is in hex.
36056 @xref{read registers packet}, for a description of how the returned
36057 register value is encoded.
36061 @item @var{XX@dots{}}
36062 the register's value
36066 Indicating an unrecognized @var{query}.
36069 @item P @var{n@dots{}}=@var{r@dots{}}
36070 @anchor{write register packet}
36071 @cindex @samp{P} packet
36072 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36073 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36074 digits for each byte in the register (target byte order).
36084 @item q @var{name} @var{params}@dots{}
36085 @itemx Q @var{name} @var{params}@dots{}
36086 @cindex @samp{q} packet
36087 @cindex @samp{Q} packet
36088 General query (@samp{q}) and set (@samp{Q}). These packets are
36089 described fully in @ref{General Query Packets}.
36092 @cindex @samp{r} packet
36093 Reset the entire system.
36095 Don't use this packet; use the @samp{R} packet instead.
36098 @cindex @samp{R} packet
36099 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36100 This packet is only available in extended mode (@pxref{extended mode}).
36102 The @samp{R} packet has no reply.
36104 @item s @r{[}@var{addr}@r{]}
36105 @cindex @samp{s} packet
36106 Single step, resuming at @var{addr}. If
36107 @var{addr} is omitted, resume at same address.
36109 This packet is deprecated for multi-threading support. @xref{vCont
36113 @xref{Stop Reply Packets}, for the reply specifications.
36115 @item S @var{sig}@r{[};@var{addr}@r{]}
36116 @anchor{step with signal packet}
36117 @cindex @samp{S} packet
36118 Step with signal. This is analogous to the @samp{C} packet, but
36119 requests a single-step, rather than a normal resumption of execution.
36121 This packet is deprecated for multi-threading support. @xref{vCont
36125 @xref{Stop Reply Packets}, for the reply specifications.
36127 @item t @var{addr}:@var{PP},@var{MM}
36128 @cindex @samp{t} packet
36129 Search backwards starting at address @var{addr} for a match with pattern
36130 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36131 There must be at least 3 digits in @var{addr}.
36133 @item T @var{thread-id}
36134 @cindex @samp{T} packet
36135 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36140 thread is still alive
36146 Packets starting with @samp{v} are identified by a multi-letter name,
36147 up to the first @samp{;} or @samp{?} (or the end of the packet).
36149 @item vAttach;@var{pid}
36150 @cindex @samp{vAttach} packet
36151 Attach to a new process with the specified process ID @var{pid}.
36152 The process ID is a
36153 hexadecimal integer identifying the process. In all-stop mode, all
36154 threads in the attached process are stopped; in non-stop mode, it may be
36155 attached without being stopped if that is supported by the target.
36157 @c In non-stop mode, on a successful vAttach, the stub should set the
36158 @c current thread to a thread of the newly-attached process. After
36159 @c attaching, GDB queries for the attached process's thread ID with qC.
36160 @c Also note that, from a user perspective, whether or not the
36161 @c target is stopped on attach in non-stop mode depends on whether you
36162 @c use the foreground or background version of the attach command, not
36163 @c on what vAttach does; GDB does the right thing with respect to either
36164 @c stopping or restarting threads.
36166 This packet is only available in extended mode (@pxref{extended mode}).
36172 @item @r{Any stop packet}
36173 for success in all-stop mode (@pxref{Stop Reply Packets})
36175 for success in non-stop mode (@pxref{Remote Non-Stop})
36178 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36179 @cindex @samp{vCont} packet
36180 @anchor{vCont packet}
36181 Resume the inferior, specifying different actions for each thread.
36183 For each inferior thread, the leftmost action with a matching
36184 @var{thread-id} is applied. Threads that don't match any action
36185 remain in their current state. Thread IDs are specified using the
36186 syntax described in @ref{thread-id syntax}. If multiprocess
36187 extensions (@pxref{multiprocess extensions}) are supported, actions
36188 can be specified to match all threads in a process by using the
36189 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36190 @var{thread-id} matches all threads. Specifying no actions is an
36193 Currently supported actions are:
36199 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36203 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36206 @item r @var{start},@var{end}
36207 Step once, and then keep stepping as long as the thread stops at
36208 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36209 The remote stub reports a stop reply when either the thread goes out
36210 of the range or is stopped due to an unrelated reason, such as hitting
36211 a breakpoint. @xref{range stepping}.
36213 If the range is empty (@var{start} == @var{end}), then the action
36214 becomes equivalent to the @samp{s} action. In other words,
36215 single-step once, and report the stop (even if the stepped instruction
36216 jumps to @var{start}).
36218 (A stop reply may be sent at any point even if the PC is still within
36219 the stepping range; for example, it is valid to implement this packet
36220 in a degenerate way as a single instruction step operation.)
36224 The optional argument @var{addr} normally associated with the
36225 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36226 not supported in @samp{vCont}.
36228 The @samp{t} action is only relevant in non-stop mode
36229 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36230 A stop reply should be generated for any affected thread not already stopped.
36231 When a thread is stopped by means of a @samp{t} action,
36232 the corresponding stop reply should indicate that the thread has stopped with
36233 signal @samp{0}, regardless of whether the target uses some other signal
36234 as an implementation detail.
36236 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36237 @samp{r} actions for threads that are already running. Conversely,
36238 the server must ignore @samp{t} actions for threads that are already
36241 @emph{Note:} In non-stop mode, a thread is considered running until
36242 @value{GDBN} acknowleges an asynchronous stop notification for it with
36243 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36245 The stub must support @samp{vCont} if it reports support for
36246 multiprocess extensions (@pxref{multiprocess extensions}).
36249 @xref{Stop Reply Packets}, for the reply specifications.
36252 @cindex @samp{vCont?} packet
36253 Request a list of actions supported by the @samp{vCont} packet.
36257 @item vCont@r{[};@var{action}@dots{}@r{]}
36258 The @samp{vCont} packet is supported. Each @var{action} is a supported
36259 command in the @samp{vCont} packet.
36261 The @samp{vCont} packet is not supported.
36264 @anchor{vCtrlC packet}
36266 @cindex @samp{vCtrlC} packet
36267 Interrupt remote target as if a control-C was pressed on the remote
36268 terminal. This is the equivalent to reacting to the @code{^C}
36269 (@samp{\003}, the control-C character) character in all-stop mode
36270 while the target is running, except this works in non-stop mode.
36271 @xref{interrupting remote targets}, for more info on the all-stop
36282 @item vFile:@var{operation}:@var{parameter}@dots{}
36283 @cindex @samp{vFile} packet
36284 Perform a file operation on the target system. For details,
36285 see @ref{Host I/O Packets}.
36287 @item vFlashErase:@var{addr},@var{length}
36288 @cindex @samp{vFlashErase} packet
36289 Direct the stub to erase @var{length} bytes of flash starting at
36290 @var{addr}. The region may enclose any number of flash blocks, but
36291 its start and end must fall on block boundaries, as indicated by the
36292 flash block size appearing in the memory map (@pxref{Memory Map
36293 Format}). @value{GDBN} groups flash memory programming operations
36294 together, and sends a @samp{vFlashDone} request after each group; the
36295 stub is allowed to delay erase operation until the @samp{vFlashDone}
36296 packet is received.
36306 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36307 @cindex @samp{vFlashWrite} packet
36308 Direct the stub to write data to flash address @var{addr}. The data
36309 is passed in binary form using the same encoding as for the @samp{X}
36310 packet (@pxref{Binary Data}). The memory ranges specified by
36311 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36312 not overlap, and must appear in order of increasing addresses
36313 (although @samp{vFlashErase} packets for higher addresses may already
36314 have been received; the ordering is guaranteed only between
36315 @samp{vFlashWrite} packets). If a packet writes to an address that was
36316 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36317 target-specific method, the results are unpredictable.
36325 for vFlashWrite addressing non-flash memory
36331 @cindex @samp{vFlashDone} packet
36332 Indicate to the stub that flash programming operation is finished.
36333 The stub is permitted to delay or batch the effects of a group of
36334 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36335 @samp{vFlashDone} packet is received. The contents of the affected
36336 regions of flash memory are unpredictable until the @samp{vFlashDone}
36337 request is completed.
36339 @item vKill;@var{pid}
36340 @cindex @samp{vKill} packet
36341 @anchor{vKill packet}
36342 Kill the process with the specified process ID @var{pid}, which is a
36343 hexadecimal integer identifying the process. This packet is used in
36344 preference to @samp{k} when multiprocess protocol extensions are
36345 supported; see @ref{multiprocess extensions}.
36355 @item vMustReplyEmpty
36356 @cindex @samp{vMustReplyEmpty} packet
36357 The correct reply to an unknown @samp{v} packet is to return the empty
36358 string, however, some older versions of @command{gdbserver} would
36359 incorrectly return @samp{OK} for unknown @samp{v} packets.
36361 The @samp{vMustReplyEmpty} is used as a feature test to check how
36362 @command{gdbserver} handles unknown packets, it is important that this
36363 packet be handled in the same way as other unknown @samp{v} packets.
36364 If this packet is handled differently to other unknown @samp{v}
36365 packets then it is possile that @value{GDBN} may run into problems in
36366 other areas, specifically around use of @samp{vFile:setfs:}.
36368 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36369 @cindex @samp{vRun} packet
36370 Run the program @var{filename}, passing it each @var{argument} on its
36371 command line. The file and arguments are hex-encoded strings. If
36372 @var{filename} is an empty string, the stub may use a default program
36373 (e.g.@: the last program run). The program is created in the stopped
36376 @c FIXME: What about non-stop mode?
36378 This packet is only available in extended mode (@pxref{extended mode}).
36384 @item @r{Any stop packet}
36385 for success (@pxref{Stop Reply Packets})
36389 @cindex @samp{vStopped} packet
36390 @xref{Notification Packets}.
36392 @item X @var{addr},@var{length}:@var{XX@dots{}}
36394 @cindex @samp{X} packet
36395 Write data to memory, where the data is transmitted in binary.
36396 Memory is specified by its address @var{addr} and number of addressable memory
36397 units @var{length} (@pxref{addressable memory unit});
36398 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36408 @item z @var{type},@var{addr},@var{kind}
36409 @itemx Z @var{type},@var{addr},@var{kind}
36410 @anchor{insert breakpoint or watchpoint packet}
36411 @cindex @samp{z} packet
36412 @cindex @samp{Z} packets
36413 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36414 watchpoint starting at address @var{address} of kind @var{kind}.
36416 Each breakpoint and watchpoint packet @var{type} is documented
36419 @emph{Implementation notes: A remote target shall return an empty string
36420 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36421 remote target shall support either both or neither of a given
36422 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36423 avoid potential problems with duplicate packets, the operations should
36424 be implemented in an idempotent way.}
36426 @item z0,@var{addr},@var{kind}
36427 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36428 @cindex @samp{z0} packet
36429 @cindex @samp{Z0} packet
36430 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36431 @var{addr} of type @var{kind}.
36433 A software breakpoint is implemented by replacing the instruction at
36434 @var{addr} with a software breakpoint or trap instruction. The
36435 @var{kind} is target-specific and typically indicates the size of the
36436 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36437 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36438 architectures have additional meanings for @var{kind}
36439 (@pxref{Architecture-Specific Protocol Details}); if no
36440 architecture-specific value is being used, it should be @samp{0}.
36441 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36442 conditional expressions in bytecode form that should be evaluated on
36443 the target's side. These are the conditions that should be taken into
36444 consideration when deciding if the breakpoint trigger should be
36445 reported back to @value{GDBN}.
36447 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36448 for how to best report a software breakpoint event to @value{GDBN}.
36450 The @var{cond_list} parameter is comprised of a series of expressions,
36451 concatenated without separators. Each expression has the following form:
36455 @item X @var{len},@var{expr}
36456 @var{len} is the length of the bytecode expression and @var{expr} is the
36457 actual conditional expression in bytecode form.
36461 The optional @var{cmd_list} parameter introduces commands that may be
36462 run on the target, rather than being reported back to @value{GDBN}.
36463 The parameter starts with a numeric flag @var{persist}; if the flag is
36464 nonzero, then the breakpoint may remain active and the commands
36465 continue to be run even when @value{GDBN} disconnects from the target.
36466 Following this flag is a series of expressions concatenated with no
36467 separators. Each expression has the following form:
36471 @item X @var{len},@var{expr}
36472 @var{len} is the length of the bytecode expression and @var{expr} is the
36473 actual commands expression in bytecode form.
36477 @emph{Implementation note: It is possible for a target to copy or move
36478 code that contains software breakpoints (e.g., when implementing
36479 overlays). The behavior of this packet, in the presence of such a
36480 target, is not defined.}
36492 @item z1,@var{addr},@var{kind}
36493 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36494 @cindex @samp{z1} packet
36495 @cindex @samp{Z1} packet
36496 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36497 address @var{addr}.
36499 A hardware breakpoint is implemented using a mechanism that is not
36500 dependent on being able to modify the target's memory. The
36501 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36502 same meaning as in @samp{Z0} packets.
36504 @emph{Implementation note: A hardware breakpoint is not affected by code
36517 @item z2,@var{addr},@var{kind}
36518 @itemx Z2,@var{addr},@var{kind}
36519 @cindex @samp{z2} packet
36520 @cindex @samp{Z2} packet
36521 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36522 The number of bytes to watch is specified by @var{kind}.
36534 @item z3,@var{addr},@var{kind}
36535 @itemx Z3,@var{addr},@var{kind}
36536 @cindex @samp{z3} packet
36537 @cindex @samp{Z3} packet
36538 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36539 The number of bytes to watch is specified by @var{kind}.
36551 @item z4,@var{addr},@var{kind}
36552 @itemx Z4,@var{addr},@var{kind}
36553 @cindex @samp{z4} packet
36554 @cindex @samp{Z4} packet
36555 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36556 The number of bytes to watch is specified by @var{kind}.
36570 @node Stop Reply Packets
36571 @section Stop Reply Packets
36572 @cindex stop reply packets
36574 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36575 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36576 receive any of the below as a reply. Except for @samp{?}
36577 and @samp{vStopped}, that reply is only returned
36578 when the target halts. In the below the exact meaning of @dfn{signal
36579 number} is defined by the header @file{include/gdb/signals.h} in the
36580 @value{GDBN} source code.
36582 In non-stop mode, the server will simply reply @samp{OK} to commands
36583 such as @samp{vCont}; any stop will be the subject of a future
36584 notification. @xref{Remote Non-Stop}.
36586 As in the description of request packets, we include spaces in the
36587 reply templates for clarity; these are not part of the reply packet's
36588 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36594 The program received signal number @var{AA} (a two-digit hexadecimal
36595 number). This is equivalent to a @samp{T} response with no
36596 @var{n}:@var{r} pairs.
36598 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36599 @cindex @samp{T} packet reply
36600 The program received signal number @var{AA} (a two-digit hexadecimal
36601 number). This is equivalent to an @samp{S} response, except that the
36602 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36603 and other information directly in the stop reply packet, reducing
36604 round-trip latency. Single-step and breakpoint traps are reported
36605 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36609 If @var{n} is a hexadecimal number, it is a register number, and the
36610 corresponding @var{r} gives that register's value. The data @var{r} is a
36611 series of bytes in target byte order, with each byte given by a
36612 two-digit hex number.
36615 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36616 the stopped thread, as specified in @ref{thread-id syntax}.
36619 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36620 the core on which the stop event was detected.
36623 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36624 specific event that stopped the target. The currently defined stop
36625 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36626 signal. At most one stop reason should be present.
36629 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36630 and go on to the next; this allows us to extend the protocol in the
36634 The currently defined stop reasons are:
36640 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36643 @item syscall_entry
36644 @itemx syscall_return
36645 The packet indicates a syscall entry or return, and @var{r} is the
36646 syscall number, in hex.
36648 @cindex shared library events, remote reply
36650 The packet indicates that the loaded libraries have changed.
36651 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36652 list of loaded libraries. The @var{r} part is ignored.
36654 @cindex replay log events, remote reply
36656 The packet indicates that the target cannot continue replaying
36657 logged execution events, because it has reached the end (or the
36658 beginning when executing backward) of the log. The value of @var{r}
36659 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36660 for more information.
36663 @anchor{swbreak stop reason}
36664 The packet indicates a software breakpoint instruction was executed,
36665 irrespective of whether it was @value{GDBN} that planted the
36666 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36667 part must be left empty.
36669 On some architectures, such as x86, at the architecture level, when a
36670 breakpoint instruction executes the program counter points at the
36671 breakpoint address plus an offset. On such targets, the stub is
36672 responsible for adjusting the PC to point back at the breakpoint
36675 This packet should not be sent by default; older @value{GDBN} versions
36676 did not support it. @value{GDBN} requests it, by supplying an
36677 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36678 remote stub must also supply the appropriate @samp{qSupported} feature
36679 indicating support.
36681 This packet is required for correct non-stop mode operation.
36684 The packet indicates the target stopped for a hardware breakpoint.
36685 The @var{r} part must be left empty.
36687 The same remarks about @samp{qSupported} and non-stop mode above
36690 @cindex fork events, remote reply
36692 The packet indicates that @code{fork} was called, and @var{r}
36693 is the thread ID of the new child process. Refer to
36694 @ref{thread-id syntax} for the format of the @var{thread-id}
36695 field. This packet is only applicable to targets that support
36698 This packet should not be sent by default; older @value{GDBN} versions
36699 did not support it. @value{GDBN} requests it, by supplying an
36700 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36701 remote stub must also supply the appropriate @samp{qSupported} feature
36702 indicating support.
36704 @cindex vfork events, remote reply
36706 The packet indicates that @code{vfork} was called, and @var{r}
36707 is the thread ID of the new child process. Refer to
36708 @ref{thread-id syntax} for the format of the @var{thread-id}
36709 field. This packet is only applicable to targets that support
36712 This packet should not be sent by default; older @value{GDBN} versions
36713 did not support it. @value{GDBN} requests it, by supplying an
36714 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36715 remote stub must also supply the appropriate @samp{qSupported} feature
36716 indicating support.
36718 @cindex vforkdone events, remote reply
36720 The packet indicates that a child process created by a vfork
36721 has either called @code{exec} or terminated, so that the
36722 address spaces of the parent and child process are no longer
36723 shared. The @var{r} part is ignored. This packet is only
36724 applicable to targets that support vforkdone events.
36726 This packet should not be sent by default; older @value{GDBN} versions
36727 did not support it. @value{GDBN} requests it, by supplying an
36728 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36729 remote stub must also supply the appropriate @samp{qSupported} feature
36730 indicating support.
36732 @cindex exec events, remote reply
36734 The packet indicates that @code{execve} was called, and @var{r}
36735 is the absolute pathname of the file that was executed, in hex.
36736 This packet is only applicable to targets that support exec events.
36738 This packet should not be sent by default; older @value{GDBN} versions
36739 did not support it. @value{GDBN} requests it, by supplying an
36740 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36741 remote stub must also supply the appropriate @samp{qSupported} feature
36742 indicating support.
36744 @cindex thread create event, remote reply
36745 @anchor{thread create event}
36747 The packet indicates that the thread was just created. The new thread
36748 is stopped until @value{GDBN} sets it running with a resumption packet
36749 (@pxref{vCont packet}). This packet should not be sent by default;
36750 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36751 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36752 @var{r} part is ignored.
36757 @itemx W @var{AA} ; process:@var{pid}
36758 The process exited, and @var{AA} is the exit status. This is only
36759 applicable to certain targets.
36761 The second form of the response, including the process ID of the
36762 exited process, can be used only when @value{GDBN} has reported
36763 support for multiprocess protocol extensions; see @ref{multiprocess
36764 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36768 @itemx X @var{AA} ; process:@var{pid}
36769 The process terminated with signal @var{AA}.
36771 The second form of the response, including the process ID of the
36772 terminated process, can be used only when @value{GDBN} has reported
36773 support for multiprocess protocol extensions; see @ref{multiprocess
36774 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36777 @anchor{thread exit event}
36778 @cindex thread exit event, remote reply
36779 @item w @var{AA} ; @var{tid}
36781 The thread exited, and @var{AA} is the exit status. This response
36782 should not be sent by default; @value{GDBN} requests it with the
36783 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36784 @var{AA} is formatted as a big-endian hex string.
36787 There are no resumed threads left in the target. In other words, even
36788 though the process is alive, the last resumed thread has exited. For
36789 example, say the target process has two threads: thread 1 and thread
36790 2. The client leaves thread 1 stopped, and resumes thread 2, which
36791 subsequently exits. At this point, even though the process is still
36792 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36793 executing either. The @samp{N} stop reply thus informs the client
36794 that it can stop waiting for stop replies. This packet should not be
36795 sent by default; older @value{GDBN} versions did not support it.
36796 @value{GDBN} requests it, by supplying an appropriate
36797 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36798 also supply the appropriate @samp{qSupported} feature indicating
36801 @item O @var{XX}@dots{}
36802 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36803 written as the program's console output. This can happen at any time
36804 while the program is running and the debugger should continue to wait
36805 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36807 @item F @var{call-id},@var{parameter}@dots{}
36808 @var{call-id} is the identifier which says which host system call should
36809 be called. This is just the name of the function. Translation into the
36810 correct system call is only applicable as it's defined in @value{GDBN}.
36811 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36814 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36815 this very system call.
36817 The target replies with this packet when it expects @value{GDBN} to
36818 call a host system call on behalf of the target. @value{GDBN} replies
36819 with an appropriate @samp{F} packet and keeps up waiting for the next
36820 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36821 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36822 Protocol Extension}, for more details.
36826 @node General Query Packets
36827 @section General Query Packets
36828 @cindex remote query requests
36830 Packets starting with @samp{q} are @dfn{general query packets};
36831 packets starting with @samp{Q} are @dfn{general set packets}. General
36832 query and set packets are a semi-unified form for retrieving and
36833 sending information to and from the stub.
36835 The initial letter of a query or set packet is followed by a name
36836 indicating what sort of thing the packet applies to. For example,
36837 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36838 definitions with the stub. These packet names follow some
36843 The name must not contain commas, colons or semicolons.
36845 Most @value{GDBN} query and set packets have a leading upper case
36848 The names of custom vendor packets should use a company prefix, in
36849 lower case, followed by a period. For example, packets designed at
36850 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36851 foos) or @samp{Qacme.bar} (for setting bars).
36854 The name of a query or set packet should be separated from any
36855 parameters by a @samp{:}; the parameters themselves should be
36856 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36857 full packet name, and check for a separator or the end of the packet,
36858 in case two packet names share a common prefix. New packets should not begin
36859 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36860 packets predate these conventions, and have arguments without any terminator
36861 for the packet name; we suspect they are in widespread use in places that
36862 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36863 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36866 Like the descriptions of the other packets, each description here
36867 has a template showing the packet's overall syntax, followed by an
36868 explanation of the packet's meaning. We include spaces in some of the
36869 templates for clarity; these are not part of the packet's syntax. No
36870 @value{GDBN} packet uses spaces to separate its components.
36872 Here are the currently defined query and set packets:
36878 Turn on or off the agent as a helper to perform some debugging operations
36879 delegated from @value{GDBN} (@pxref{Control Agent}).
36881 @item QAllow:@var{op}:@var{val}@dots{}
36882 @cindex @samp{QAllow} packet
36883 Specify which operations @value{GDBN} expects to request of the
36884 target, as a semicolon-separated list of operation name and value
36885 pairs. Possible values for @var{op} include @samp{WriteReg},
36886 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36887 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36888 indicating that @value{GDBN} will not request the operation, or 1,
36889 indicating that it may. (The target can then use this to set up its
36890 own internals optimally, for instance if the debugger never expects to
36891 insert breakpoints, it may not need to install its own trap handler.)
36894 @cindex current thread, remote request
36895 @cindex @samp{qC} packet
36896 Return the current thread ID.
36900 @item QC @var{thread-id}
36901 Where @var{thread-id} is a thread ID as documented in
36902 @ref{thread-id syntax}.
36903 @item @r{(anything else)}
36904 Any other reply implies the old thread ID.
36907 @item qCRC:@var{addr},@var{length}
36908 @cindex CRC of memory block, remote request
36909 @cindex @samp{qCRC} packet
36910 @anchor{qCRC packet}
36911 Compute the CRC checksum of a block of memory using CRC-32 defined in
36912 IEEE 802.3. The CRC is computed byte at a time, taking the most
36913 significant bit of each byte first. The initial pattern code
36914 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36916 @emph{Note:} This is the same CRC used in validating separate debug
36917 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36918 Files}). However the algorithm is slightly different. When validating
36919 separate debug files, the CRC is computed taking the @emph{least}
36920 significant bit of each byte first, and the final result is inverted to
36921 detect trailing zeros.
36926 An error (such as memory fault)
36927 @item C @var{crc32}
36928 The specified memory region's checksum is @var{crc32}.
36931 @item QDisableRandomization:@var{value}
36932 @cindex disable address space randomization, remote request
36933 @cindex @samp{QDisableRandomization} packet
36934 Some target operating systems will randomize the virtual address space
36935 of the inferior process as a security feature, but provide a feature
36936 to disable such randomization, e.g.@: to allow for a more deterministic
36937 debugging experience. On such systems, this packet with a @var{value}
36938 of 1 directs the target to disable address space randomization for
36939 processes subsequently started via @samp{vRun} packets, while a packet
36940 with a @var{value} of 0 tells the target to enable address space
36943 This packet is only available in extended mode (@pxref{extended mode}).
36948 The request succeeded.
36951 An error occurred. The error number @var{nn} is given as hex digits.
36954 An empty reply indicates that @samp{QDisableRandomization} is not supported
36958 This packet is not probed by default; the remote stub must request it,
36959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36960 This should only be done on targets that actually support disabling
36961 address space randomization.
36963 @item QStartupWithShell:@var{value}
36964 @cindex startup with shell, remote request
36965 @cindex @samp{QStartupWithShell} packet
36966 On UNIX-like targets, it is possible to start the inferior using a
36967 shell program. This is the default behavior on both @value{GDBN} and
36968 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36969 used to inform @command{gdbserver} whether it should start the
36970 inferior using a shell or not.
36972 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36973 to start the inferior. If @var{value} is @samp{1},
36974 @command{gdbserver} will use a shell to start the inferior. All other
36975 values are considered an error.
36977 This packet is only available in extended mode (@pxref{extended
36983 The request succeeded.
36986 An error occurred. The error number @var{nn} is given as hex digits.
36989 This packet is not probed by default; the remote stub must request it,
36990 by supplying an appropriate @samp{qSupported} response
36991 (@pxref{qSupported}). This should only be done on targets that
36992 actually support starting the inferior using a shell.
36994 Use of this packet is controlled by the @code{set startup-with-shell}
36995 command; @pxref{set startup-with-shell}.
36997 @item QEnvironmentHexEncoded:@var{hex-value}
36998 @anchor{QEnvironmentHexEncoded}
36999 @cindex set environment variable, remote request
37000 @cindex @samp{QEnvironmentHexEncoded} packet
37001 On UNIX-like targets, it is possible to set environment variables that
37002 will be passed to the inferior during the startup process. This
37003 packet is used to inform @command{gdbserver} of an environment
37004 variable that has been defined by the user on @value{GDBN} (@pxref{set
37007 The packet is composed by @var{hex-value}, an hex encoded
37008 representation of the @var{name=value} format representing an
37009 environment variable. The name of the environment variable is
37010 represented by @var{name}, and the value to be assigned to the
37011 environment variable is represented by @var{value}. If the variable
37012 has no value (i.e., the value is @code{null}), then @var{value} will
37015 This packet is only available in extended mode (@pxref{extended
37021 The request succeeded.
37024 This packet is not probed by default; the remote stub must request it,
37025 by supplying an appropriate @samp{qSupported} response
37026 (@pxref{qSupported}). This should only be done on targets that
37027 actually support passing environment variables to the starting
37030 This packet is related to the @code{set environment} command;
37031 @pxref{set environment}.
37033 @item QEnvironmentUnset:@var{hex-value}
37034 @anchor{QEnvironmentUnset}
37035 @cindex unset environment variable, remote request
37036 @cindex @samp{QEnvironmentUnset} packet
37037 On UNIX-like targets, it is possible to unset environment variables
37038 before starting the inferior in the remote target. This packet is
37039 used to inform @command{gdbserver} of an environment variable that has
37040 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37042 The packet is composed by @var{hex-value}, an hex encoded
37043 representation of the name of the environment variable to be unset.
37045 This packet is only available in extended mode (@pxref{extended
37051 The request succeeded.
37054 This packet is not probed by default; the remote stub must request it,
37055 by supplying an appropriate @samp{qSupported} response
37056 (@pxref{qSupported}). This should only be done on targets that
37057 actually support passing environment variables to the starting
37060 This packet is related to the @code{unset environment} command;
37061 @pxref{unset environment}.
37063 @item QEnvironmentReset
37064 @anchor{QEnvironmentReset}
37065 @cindex reset environment, remote request
37066 @cindex @samp{QEnvironmentReset} packet
37067 On UNIX-like targets, this packet is used to reset the state of
37068 environment variables in the remote target before starting the
37069 inferior. In this context, reset means unsetting all environment
37070 variables that were previously set by the user (i.e., were not
37071 initially present in the environment). It is sent to
37072 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37073 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37074 (@pxref{QEnvironmentUnset}) packets.
37076 This packet is only available in extended mode (@pxref{extended
37082 The request succeeded.
37085 This packet is not probed by default; the remote stub must request it,
37086 by supplying an appropriate @samp{qSupported} response
37087 (@pxref{qSupported}). This should only be done on targets that
37088 actually support passing environment variables to the starting
37091 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37092 @anchor{QSetWorkingDir packet}
37093 @cindex set working directory, remote request
37094 @cindex @samp{QSetWorkingDir} packet
37095 This packet is used to inform the remote server of the intended
37096 current working directory for programs that are going to be executed.
37098 The packet is composed by @var{directory}, an hex encoded
37099 representation of the directory that the remote inferior will use as
37100 its current working directory. If @var{directory} is an empty string,
37101 the remote server should reset the inferior's current working
37102 directory to its original, empty value.
37104 This packet is only available in extended mode (@pxref{extended
37110 The request succeeded.
37114 @itemx qsThreadInfo
37115 @cindex list active threads, remote request
37116 @cindex @samp{qfThreadInfo} packet
37117 @cindex @samp{qsThreadInfo} packet
37118 Obtain a list of all active thread IDs from the target (OS). Since there
37119 may be too many active threads to fit into one reply packet, this query
37120 works iteratively: it may require more than one query/reply sequence to
37121 obtain the entire list of threads. The first query of the sequence will
37122 be the @samp{qfThreadInfo} query; subsequent queries in the
37123 sequence will be the @samp{qsThreadInfo} query.
37125 NOTE: This packet replaces the @samp{qL} query (see below).
37129 @item m @var{thread-id}
37131 @item m @var{thread-id},@var{thread-id}@dots{}
37132 a comma-separated list of thread IDs
37134 (lower case letter @samp{L}) denotes end of list.
37137 In response to each query, the target will reply with a list of one or
37138 more thread IDs, separated by commas.
37139 @value{GDBN} will respond to each reply with a request for more thread
37140 ids (using the @samp{qs} form of the query), until the target responds
37141 with @samp{l} (lower-case ell, for @dfn{last}).
37142 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37145 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37146 initial connection with the remote target, and the very first thread ID
37147 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37148 message. Therefore, the stub should ensure that the first thread ID in
37149 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37151 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37152 @cindex get thread-local storage address, remote request
37153 @cindex @samp{qGetTLSAddr} packet
37154 Fetch the address associated with thread local storage specified
37155 by @var{thread-id}, @var{offset}, and @var{lm}.
37157 @var{thread-id} is the thread ID associated with the
37158 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37160 @var{offset} is the (big endian, hex encoded) offset associated with the
37161 thread local variable. (This offset is obtained from the debug
37162 information associated with the variable.)
37164 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37165 load module associated with the thread local storage. For example,
37166 a @sc{gnu}/Linux system will pass the link map address of the shared
37167 object associated with the thread local storage under consideration.
37168 Other operating environments may choose to represent the load module
37169 differently, so the precise meaning of this parameter will vary.
37173 @item @var{XX}@dots{}
37174 Hex encoded (big endian) bytes representing the address of the thread
37175 local storage requested.
37178 An error occurred. The error number @var{nn} is given as hex digits.
37181 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37184 @item qGetTIBAddr:@var{thread-id}
37185 @cindex get thread information block address
37186 @cindex @samp{qGetTIBAddr} packet
37187 Fetch address of the Windows OS specific Thread Information Block.
37189 @var{thread-id} is the thread ID associated with the thread.
37193 @item @var{XX}@dots{}
37194 Hex encoded (big endian) bytes representing the linear address of the
37195 thread information block.
37198 An error occured. This means that either the thread was not found, or the
37199 address could not be retrieved.
37202 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37205 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37206 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37207 digit) is one to indicate the first query and zero to indicate a
37208 subsequent query; @var{threadcount} (two hex digits) is the maximum
37209 number of threads the response packet can contain; and @var{nextthread}
37210 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37211 returned in the response as @var{argthread}.
37213 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37217 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37218 Where: @var{count} (two hex digits) is the number of threads being
37219 returned; @var{done} (one hex digit) is zero to indicate more threads
37220 and one indicates no further threads; @var{argthreadid} (eight hex
37221 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37222 is a sequence of thread IDs, @var{threadid} (eight hex
37223 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37227 @cindex section offsets, remote request
37228 @cindex @samp{qOffsets} packet
37229 Get section offsets that the target used when relocating the downloaded
37234 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37235 Relocate the @code{Text} section by @var{xxx} from its original address.
37236 Relocate the @code{Data} section by @var{yyy} from its original address.
37237 If the object file format provides segment information (e.g.@: @sc{elf}
37238 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37239 segments by the supplied offsets.
37241 @emph{Note: while a @code{Bss} offset may be included in the response,
37242 @value{GDBN} ignores this and instead applies the @code{Data} offset
37243 to the @code{Bss} section.}
37245 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37246 Relocate the first segment of the object file, which conventionally
37247 contains program code, to a starting address of @var{xxx}. If
37248 @samp{DataSeg} is specified, relocate the second segment, which
37249 conventionally contains modifiable data, to a starting address of
37250 @var{yyy}. @value{GDBN} will report an error if the object file
37251 does not contain segment information, or does not contain at least
37252 as many segments as mentioned in the reply. Extra segments are
37253 kept at fixed offsets relative to the last relocated segment.
37256 @item qP @var{mode} @var{thread-id}
37257 @cindex thread information, remote request
37258 @cindex @samp{qP} packet
37259 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37260 encoded 32 bit mode; @var{thread-id} is a thread ID
37261 (@pxref{thread-id syntax}).
37263 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37266 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37270 @cindex non-stop mode, remote request
37271 @cindex @samp{QNonStop} packet
37273 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37274 @xref{Remote Non-Stop}, for more information.
37279 The request succeeded.
37282 An error occurred. The error number @var{nn} is given as hex digits.
37285 An empty reply indicates that @samp{QNonStop} is not supported by
37289 This packet is not probed by default; the remote stub must request it,
37290 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37291 Use of this packet is controlled by the @code{set non-stop} command;
37292 @pxref{Non-Stop Mode}.
37294 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37295 @itemx QCatchSyscalls:0
37296 @cindex catch syscalls from inferior, remote request
37297 @cindex @samp{QCatchSyscalls} packet
37298 @anchor{QCatchSyscalls}
37299 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37300 catching syscalls from the inferior process.
37302 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37303 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37304 is listed, every system call should be reported.
37306 Note that if a syscall not in the list is reported, @value{GDBN} will
37307 still filter the event according to its own list from all corresponding
37308 @code{catch syscall} commands. However, it is more efficient to only
37309 report the requested syscalls.
37311 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37312 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37314 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37315 kept for the new process too. On targets where exec may affect syscall
37316 numbers, for example with exec between 32 and 64-bit processes, the
37317 client should send a new packet with the new syscall list.
37322 The request succeeded.
37325 An error occurred. @var{nn} are hex digits.
37328 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37332 Use of this packet is controlled by the @code{set remote catch-syscalls}
37333 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37334 This packet is not probed by default; the remote stub must request it,
37335 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37337 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37338 @cindex pass signals to inferior, remote request
37339 @cindex @samp{QPassSignals} packet
37340 @anchor{QPassSignals}
37341 Each listed @var{signal} should be passed directly to the inferior process.
37342 Signals are numbered identically to continue packets and stop replies
37343 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37344 strictly greater than the previous item. These signals do not need to stop
37345 the inferior, or be reported to @value{GDBN}. All other signals should be
37346 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37347 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37348 new list. This packet improves performance when using @samp{handle
37349 @var{signal} nostop noprint pass}.
37354 The request succeeded.
37357 An error occurred. The error number @var{nn} is given as hex digits.
37360 An empty reply indicates that @samp{QPassSignals} is not supported by
37364 Use of this packet is controlled by the @code{set remote pass-signals}
37365 command (@pxref{Remote Configuration, set remote pass-signals}).
37366 This packet is not probed by default; the remote stub must request it,
37367 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37369 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37370 @cindex signals the inferior may see, remote request
37371 @cindex @samp{QProgramSignals} packet
37372 @anchor{QProgramSignals}
37373 Each listed @var{signal} may be delivered to the inferior process.
37374 Others should be silently discarded.
37376 In some cases, the remote stub may need to decide whether to deliver a
37377 signal to the program or not without @value{GDBN} involvement. One
37378 example of that is while detaching --- the program's threads may have
37379 stopped for signals that haven't yet had a chance of being reported to
37380 @value{GDBN}, and so the remote stub can use the signal list specified
37381 by this packet to know whether to deliver or ignore those pending
37384 This does not influence whether to deliver a signal as requested by a
37385 resumption packet (@pxref{vCont packet}).
37387 Signals are numbered identically to continue packets and stop replies
37388 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37389 strictly greater than the previous item. Multiple
37390 @samp{QProgramSignals} packets do not combine; any earlier
37391 @samp{QProgramSignals} list is completely replaced by the new list.
37396 The request succeeded.
37399 An error occurred. The error number @var{nn} is given as hex digits.
37402 An empty reply indicates that @samp{QProgramSignals} is not supported
37406 Use of this packet is controlled by the @code{set remote program-signals}
37407 command (@pxref{Remote Configuration, set remote program-signals}).
37408 This packet is not probed by default; the remote stub must request it,
37409 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37411 @anchor{QThreadEvents}
37412 @item QThreadEvents:1
37413 @itemx QThreadEvents:0
37414 @cindex thread create/exit events, remote request
37415 @cindex @samp{QThreadEvents} packet
37417 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37418 reporting of thread create and exit events. @xref{thread create
37419 event}, for the reply specifications. For example, this is used in
37420 non-stop mode when @value{GDBN} stops a set of threads and
37421 synchronously waits for the their corresponding stop replies. Without
37422 exit events, if one of the threads exits, @value{GDBN} would hang
37423 forever not knowing that it should no longer expect a stop for that
37424 same thread. @value{GDBN} does not enable this feature unless the
37425 stub reports that it supports it by including @samp{QThreadEvents+} in
37426 its @samp{qSupported} reply.
37431 The request succeeded.
37434 An error occurred. The error number @var{nn} is given as hex digits.
37437 An empty reply indicates that @samp{QThreadEvents} is not supported by
37441 Use of this packet is controlled by the @code{set remote thread-events}
37442 command (@pxref{Remote Configuration, set remote thread-events}).
37444 @item qRcmd,@var{command}
37445 @cindex execute remote command, remote request
37446 @cindex @samp{qRcmd} packet
37447 @var{command} (hex encoded) is passed to the local interpreter for
37448 execution. Invalid commands should be reported using the output
37449 string. Before the final result packet, the target may also respond
37450 with a number of intermediate @samp{O@var{output}} console output
37451 packets. @emph{Implementors should note that providing access to a
37452 stubs's interpreter may have security implications}.
37457 A command response with no output.
37459 A command response with the hex encoded output string @var{OUTPUT}.
37461 Indicate a badly formed request.
37463 An empty reply indicates that @samp{qRcmd} is not recognized.
37466 (Note that the @code{qRcmd} packet's name is separated from the
37467 command by a @samp{,}, not a @samp{:}, contrary to the naming
37468 conventions above. Please don't use this packet as a model for new
37471 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37472 @cindex searching memory, in remote debugging
37474 @cindex @samp{qSearch:memory} packet
37476 @cindex @samp{qSearch memory} packet
37477 @anchor{qSearch memory}
37478 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37479 Both @var{address} and @var{length} are encoded in hex;
37480 @var{search-pattern} is a sequence of bytes, also hex encoded.
37485 The pattern was not found.
37487 The pattern was found at @var{address}.
37489 A badly formed request or an error was encountered while searching memory.
37491 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37494 @item QStartNoAckMode
37495 @cindex @samp{QStartNoAckMode} packet
37496 @anchor{QStartNoAckMode}
37497 Request that the remote stub disable the normal @samp{+}/@samp{-}
37498 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37503 The stub has switched to no-acknowledgment mode.
37504 @value{GDBN} acknowledges this reponse,
37505 but neither the stub nor @value{GDBN} shall send or expect further
37506 @samp{+}/@samp{-} acknowledgments in the current connection.
37508 An empty reply indicates that the stub does not support no-acknowledgment mode.
37511 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37512 @cindex supported packets, remote query
37513 @cindex features of the remote protocol
37514 @cindex @samp{qSupported} packet
37515 @anchor{qSupported}
37516 Tell the remote stub about features supported by @value{GDBN}, and
37517 query the stub for features it supports. This packet allows
37518 @value{GDBN} and the remote stub to take advantage of each others'
37519 features. @samp{qSupported} also consolidates multiple feature probes
37520 at startup, to improve @value{GDBN} performance---a single larger
37521 packet performs better than multiple smaller probe packets on
37522 high-latency links. Some features may enable behavior which must not
37523 be on by default, e.g.@: because it would confuse older clients or
37524 stubs. Other features may describe packets which could be
37525 automatically probed for, but are not. These features must be
37526 reported before @value{GDBN} will use them. This ``default
37527 unsupported'' behavior is not appropriate for all packets, but it
37528 helps to keep the initial connection time under control with new
37529 versions of @value{GDBN} which support increasing numbers of packets.
37533 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37534 The stub supports or does not support each returned @var{stubfeature},
37535 depending on the form of each @var{stubfeature} (see below for the
37538 An empty reply indicates that @samp{qSupported} is not recognized,
37539 or that no features needed to be reported to @value{GDBN}.
37542 The allowed forms for each feature (either a @var{gdbfeature} in the
37543 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37547 @item @var{name}=@var{value}
37548 The remote protocol feature @var{name} is supported, and associated
37549 with the specified @var{value}. The format of @var{value} depends
37550 on the feature, but it must not include a semicolon.
37552 The remote protocol feature @var{name} is supported, and does not
37553 need an associated value.
37555 The remote protocol feature @var{name} is not supported.
37557 The remote protocol feature @var{name} may be supported, and
37558 @value{GDBN} should auto-detect support in some other way when it is
37559 needed. This form will not be used for @var{gdbfeature} notifications,
37560 but may be used for @var{stubfeature} responses.
37563 Whenever the stub receives a @samp{qSupported} request, the
37564 supplied set of @value{GDBN} features should override any previous
37565 request. This allows @value{GDBN} to put the stub in a known
37566 state, even if the stub had previously been communicating with
37567 a different version of @value{GDBN}.
37569 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37574 This feature indicates whether @value{GDBN} supports multiprocess
37575 extensions to the remote protocol. @value{GDBN} does not use such
37576 extensions unless the stub also reports that it supports them by
37577 including @samp{multiprocess+} in its @samp{qSupported} reply.
37578 @xref{multiprocess extensions}, for details.
37581 This feature indicates that @value{GDBN} supports the XML target
37582 description. If the stub sees @samp{xmlRegisters=} with target
37583 specific strings separated by a comma, it will report register
37587 This feature indicates whether @value{GDBN} supports the
37588 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37589 instruction reply packet}).
37592 This feature indicates whether @value{GDBN} supports the swbreak stop
37593 reason in stop replies. @xref{swbreak stop reason}, for details.
37596 This feature indicates whether @value{GDBN} supports the hwbreak stop
37597 reason in stop replies. @xref{swbreak stop reason}, for details.
37600 This feature indicates whether @value{GDBN} supports fork event
37601 extensions to the remote protocol. @value{GDBN} does not use such
37602 extensions unless the stub also reports that it supports them by
37603 including @samp{fork-events+} in its @samp{qSupported} reply.
37606 This feature indicates whether @value{GDBN} supports vfork event
37607 extensions to the remote protocol. @value{GDBN} does not use such
37608 extensions unless the stub also reports that it supports them by
37609 including @samp{vfork-events+} in its @samp{qSupported} reply.
37612 This feature indicates whether @value{GDBN} supports exec event
37613 extensions to the remote protocol. @value{GDBN} does not use such
37614 extensions unless the stub also reports that it supports them by
37615 including @samp{exec-events+} in its @samp{qSupported} reply.
37617 @item vContSupported
37618 This feature indicates whether @value{GDBN} wants to know the
37619 supported actions in the reply to @samp{vCont?} packet.
37622 Stubs should ignore any unknown values for
37623 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37624 packet supports receiving packets of unlimited length (earlier
37625 versions of @value{GDBN} may reject overly long responses). Additional values
37626 for @var{gdbfeature} may be defined in the future to let the stub take
37627 advantage of new features in @value{GDBN}, e.g.@: incompatible
37628 improvements in the remote protocol---the @samp{multiprocess} feature is
37629 an example of such a feature. The stub's reply should be independent
37630 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37631 describes all the features it supports, and then the stub replies with
37632 all the features it supports.
37634 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37635 responses, as long as each response uses one of the standard forms.
37637 Some features are flags. A stub which supports a flag feature
37638 should respond with a @samp{+} form response. Other features
37639 require values, and the stub should respond with an @samp{=}
37642 Each feature has a default value, which @value{GDBN} will use if
37643 @samp{qSupported} is not available or if the feature is not mentioned
37644 in the @samp{qSupported} response. The default values are fixed; a
37645 stub is free to omit any feature responses that match the defaults.
37647 Not all features can be probed, but for those which can, the probing
37648 mechanism is useful: in some cases, a stub's internal
37649 architecture may not allow the protocol layer to know some information
37650 about the underlying target in advance. This is especially common in
37651 stubs which may be configured for multiple targets.
37653 These are the currently defined stub features and their properties:
37655 @multitable @columnfractions 0.35 0.2 0.12 0.2
37656 @c NOTE: The first row should be @headitem, but we do not yet require
37657 @c a new enough version of Texinfo (4.7) to use @headitem.
37659 @tab Value Required
37663 @item @samp{PacketSize}
37668 @item @samp{qXfer:auxv:read}
37673 @item @samp{qXfer:btrace:read}
37678 @item @samp{qXfer:btrace-conf:read}
37683 @item @samp{qXfer:exec-file:read}
37688 @item @samp{qXfer:features:read}
37693 @item @samp{qXfer:libraries:read}
37698 @item @samp{qXfer:libraries-svr4:read}
37703 @item @samp{augmented-libraries-svr4-read}
37708 @item @samp{qXfer:memory-map:read}
37713 @item @samp{qXfer:sdata:read}
37718 @item @samp{qXfer:spu:read}
37723 @item @samp{qXfer:spu:write}
37728 @item @samp{qXfer:siginfo:read}
37733 @item @samp{qXfer:siginfo:write}
37738 @item @samp{qXfer:threads:read}
37743 @item @samp{qXfer:traceframe-info:read}
37748 @item @samp{qXfer:uib:read}
37753 @item @samp{qXfer:fdpic:read}
37758 @item @samp{Qbtrace:off}
37763 @item @samp{Qbtrace:bts}
37768 @item @samp{Qbtrace:pt}
37773 @item @samp{Qbtrace-conf:bts:size}
37778 @item @samp{Qbtrace-conf:pt:size}
37783 @item @samp{QNonStop}
37788 @item @samp{QCatchSyscalls}
37793 @item @samp{QPassSignals}
37798 @item @samp{QStartNoAckMode}
37803 @item @samp{multiprocess}
37808 @item @samp{ConditionalBreakpoints}
37813 @item @samp{ConditionalTracepoints}
37818 @item @samp{ReverseContinue}
37823 @item @samp{ReverseStep}
37828 @item @samp{TracepointSource}
37833 @item @samp{QAgent}
37838 @item @samp{QAllow}
37843 @item @samp{QDisableRandomization}
37848 @item @samp{EnableDisableTracepoints}
37853 @item @samp{QTBuffer:size}
37858 @item @samp{tracenz}
37863 @item @samp{BreakpointCommands}
37868 @item @samp{swbreak}
37873 @item @samp{hwbreak}
37878 @item @samp{fork-events}
37883 @item @samp{vfork-events}
37888 @item @samp{exec-events}
37893 @item @samp{QThreadEvents}
37898 @item @samp{no-resumed}
37905 These are the currently defined stub features, in more detail:
37908 @cindex packet size, remote protocol
37909 @item PacketSize=@var{bytes}
37910 The remote stub can accept packets up to at least @var{bytes} in
37911 length. @value{GDBN} will send packets up to this size for bulk
37912 transfers, and will never send larger packets. This is a limit on the
37913 data characters in the packet, including the frame and checksum.
37914 There is no trailing NUL byte in a remote protocol packet; if the stub
37915 stores packets in a NUL-terminated format, it should allow an extra
37916 byte in its buffer for the NUL. If this stub feature is not supported,
37917 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37919 @item qXfer:auxv:read
37920 The remote stub understands the @samp{qXfer:auxv:read} packet
37921 (@pxref{qXfer auxiliary vector read}).
37923 @item qXfer:btrace:read
37924 The remote stub understands the @samp{qXfer:btrace:read}
37925 packet (@pxref{qXfer btrace read}).
37927 @item qXfer:btrace-conf:read
37928 The remote stub understands the @samp{qXfer:btrace-conf:read}
37929 packet (@pxref{qXfer btrace-conf read}).
37931 @item qXfer:exec-file:read
37932 The remote stub understands the @samp{qXfer:exec-file:read} packet
37933 (@pxref{qXfer executable filename read}).
37935 @item qXfer:features:read
37936 The remote stub understands the @samp{qXfer:features:read} packet
37937 (@pxref{qXfer target description read}).
37939 @item qXfer:libraries:read
37940 The remote stub understands the @samp{qXfer:libraries:read} packet
37941 (@pxref{qXfer library list read}).
37943 @item qXfer:libraries-svr4:read
37944 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37945 (@pxref{qXfer svr4 library list read}).
37947 @item augmented-libraries-svr4-read
37948 The remote stub understands the augmented form of the
37949 @samp{qXfer:libraries-svr4:read} packet
37950 (@pxref{qXfer svr4 library list read}).
37952 @item qXfer:memory-map:read
37953 The remote stub understands the @samp{qXfer:memory-map:read} packet
37954 (@pxref{qXfer memory map read}).
37956 @item qXfer:sdata:read
37957 The remote stub understands the @samp{qXfer:sdata:read} packet
37958 (@pxref{qXfer sdata read}).
37960 @item qXfer:spu:read
37961 The remote stub understands the @samp{qXfer:spu:read} packet
37962 (@pxref{qXfer spu read}).
37964 @item qXfer:spu:write
37965 The remote stub understands the @samp{qXfer:spu:write} packet
37966 (@pxref{qXfer spu write}).
37968 @item qXfer:siginfo:read
37969 The remote stub understands the @samp{qXfer:siginfo:read} packet
37970 (@pxref{qXfer siginfo read}).
37972 @item qXfer:siginfo:write
37973 The remote stub understands the @samp{qXfer:siginfo:write} packet
37974 (@pxref{qXfer siginfo write}).
37976 @item qXfer:threads:read
37977 The remote stub understands the @samp{qXfer:threads:read} packet
37978 (@pxref{qXfer threads read}).
37980 @item qXfer:traceframe-info:read
37981 The remote stub understands the @samp{qXfer:traceframe-info:read}
37982 packet (@pxref{qXfer traceframe info read}).
37984 @item qXfer:uib:read
37985 The remote stub understands the @samp{qXfer:uib:read}
37986 packet (@pxref{qXfer unwind info block}).
37988 @item qXfer:fdpic:read
37989 The remote stub understands the @samp{qXfer:fdpic:read}
37990 packet (@pxref{qXfer fdpic loadmap read}).
37993 The remote stub understands the @samp{QNonStop} packet
37994 (@pxref{QNonStop}).
37996 @item QCatchSyscalls
37997 The remote stub understands the @samp{QCatchSyscalls} packet
37998 (@pxref{QCatchSyscalls}).
38001 The remote stub understands the @samp{QPassSignals} packet
38002 (@pxref{QPassSignals}).
38004 @item QStartNoAckMode
38005 The remote stub understands the @samp{QStartNoAckMode} packet and
38006 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38009 @anchor{multiprocess extensions}
38010 @cindex multiprocess extensions, in remote protocol
38011 The remote stub understands the multiprocess extensions to the remote
38012 protocol syntax. The multiprocess extensions affect the syntax of
38013 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38014 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38015 replies. Note that reporting this feature indicates support for the
38016 syntactic extensions only, not that the stub necessarily supports
38017 debugging of more than one process at a time. The stub must not use
38018 multiprocess extensions in packet replies unless @value{GDBN} has also
38019 indicated it supports them in its @samp{qSupported} request.
38021 @item qXfer:osdata:read
38022 The remote stub understands the @samp{qXfer:osdata:read} packet
38023 ((@pxref{qXfer osdata read}).
38025 @item ConditionalBreakpoints
38026 The target accepts and implements evaluation of conditional expressions
38027 defined for breakpoints. The target will only report breakpoint triggers
38028 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38030 @item ConditionalTracepoints
38031 The remote stub accepts and implements conditional expressions defined
38032 for tracepoints (@pxref{Tracepoint Conditions}).
38034 @item ReverseContinue
38035 The remote stub accepts and implements the reverse continue packet
38039 The remote stub accepts and implements the reverse step packet
38042 @item TracepointSource
38043 The remote stub understands the @samp{QTDPsrc} packet that supplies
38044 the source form of tracepoint definitions.
38047 The remote stub understands the @samp{QAgent} packet.
38050 The remote stub understands the @samp{QAllow} packet.
38052 @item QDisableRandomization
38053 The remote stub understands the @samp{QDisableRandomization} packet.
38055 @item StaticTracepoint
38056 @cindex static tracepoints, in remote protocol
38057 The remote stub supports static tracepoints.
38059 @item InstallInTrace
38060 @anchor{install tracepoint in tracing}
38061 The remote stub supports installing tracepoint in tracing.
38063 @item EnableDisableTracepoints
38064 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38065 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38066 to be enabled and disabled while a trace experiment is running.
38068 @item QTBuffer:size
38069 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38070 packet that allows to change the size of the trace buffer.
38073 @cindex string tracing, in remote protocol
38074 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38075 See @ref{Bytecode Descriptions} for details about the bytecode.
38077 @item BreakpointCommands
38078 @cindex breakpoint commands, in remote protocol
38079 The remote stub supports running a breakpoint's command list itself,
38080 rather than reporting the hit to @value{GDBN}.
38083 The remote stub understands the @samp{Qbtrace:off} packet.
38086 The remote stub understands the @samp{Qbtrace:bts} packet.
38089 The remote stub understands the @samp{Qbtrace:pt} packet.
38091 @item Qbtrace-conf:bts:size
38092 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38094 @item Qbtrace-conf:pt:size
38095 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38098 The remote stub reports the @samp{swbreak} stop reason for memory
38102 The remote stub reports the @samp{hwbreak} stop reason for hardware
38106 The remote stub reports the @samp{fork} stop reason for fork events.
38109 The remote stub reports the @samp{vfork} stop reason for vfork events
38110 and vforkdone events.
38113 The remote stub reports the @samp{exec} stop reason for exec events.
38115 @item vContSupported
38116 The remote stub reports the supported actions in the reply to
38117 @samp{vCont?} packet.
38119 @item QThreadEvents
38120 The remote stub understands the @samp{QThreadEvents} packet.
38123 The remote stub reports the @samp{N} stop reply.
38128 @cindex symbol lookup, remote request
38129 @cindex @samp{qSymbol} packet
38130 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38131 requests. Accept requests from the target for the values of symbols.
38136 The target does not need to look up any (more) symbols.
38137 @item qSymbol:@var{sym_name}
38138 The target requests the value of symbol @var{sym_name} (hex encoded).
38139 @value{GDBN} may provide the value by using the
38140 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38144 @item qSymbol:@var{sym_value}:@var{sym_name}
38145 Set the value of @var{sym_name} to @var{sym_value}.
38147 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38148 target has previously requested.
38150 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38151 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38157 The target does not need to look up any (more) symbols.
38158 @item qSymbol:@var{sym_name}
38159 The target requests the value of a new symbol @var{sym_name} (hex
38160 encoded). @value{GDBN} will continue to supply the values of symbols
38161 (if available), until the target ceases to request them.
38166 @itemx QTDisconnected
38173 @itemx qTMinFTPILen
38175 @xref{Tracepoint Packets}.
38177 @item qThreadExtraInfo,@var{thread-id}
38178 @cindex thread attributes info, remote request
38179 @cindex @samp{qThreadExtraInfo} packet
38180 Obtain from the target OS a printable string description of thread
38181 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38182 for the forms of @var{thread-id}. This
38183 string may contain anything that the target OS thinks is interesting
38184 for @value{GDBN} to tell the user about the thread. The string is
38185 displayed in @value{GDBN}'s @code{info threads} display. Some
38186 examples of possible thread extra info strings are @samp{Runnable}, or
38187 @samp{Blocked on Mutex}.
38191 @item @var{XX}@dots{}
38192 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38193 comprising the printable string containing the extra information about
38194 the thread's attributes.
38197 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38198 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38199 conventions above. Please don't use this packet as a model for new
38218 @xref{Tracepoint Packets}.
38220 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38221 @cindex read special object, remote request
38222 @cindex @samp{qXfer} packet
38223 @anchor{qXfer read}
38224 Read uninterpreted bytes from the target's special data area
38225 identified by the keyword @var{object}. Request @var{length} bytes
38226 starting at @var{offset} bytes into the data. The content and
38227 encoding of @var{annex} is specific to @var{object}; it can supply
38228 additional details about what data to access.
38233 Data @var{data} (@pxref{Binary Data}) has been read from the
38234 target. There may be more data at a higher address (although
38235 it is permitted to return @samp{m} even for the last valid
38236 block of data, as long as at least one byte of data was read).
38237 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38241 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38242 There is no more data to be read. It is possible for @var{data} to
38243 have fewer bytes than the @var{length} in the request.
38246 The @var{offset} in the request is at the end of the data.
38247 There is no more data to be read.
38250 The request was malformed, or @var{annex} was invalid.
38253 The offset was invalid, or there was an error encountered reading the data.
38254 The @var{nn} part is a hex-encoded @code{errno} value.
38257 An empty reply indicates the @var{object} string was not recognized by
38258 the stub, or that the object does not support reading.
38261 Here are the specific requests of this form defined so far. All the
38262 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38263 formats, listed above.
38266 @item qXfer:auxv:read::@var{offset},@var{length}
38267 @anchor{qXfer auxiliary vector read}
38268 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38269 auxiliary vector}. Note @var{annex} must be empty.
38271 This packet is not probed by default; the remote stub must request it,
38272 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38274 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38275 @anchor{qXfer btrace read}
38277 Return a description of the current branch trace.
38278 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38279 packet may have one of the following values:
38283 Returns all available branch trace.
38286 Returns all available branch trace if the branch trace changed since
38287 the last read request.
38290 Returns the new branch trace since the last read request. Adds a new
38291 block to the end of the trace that begins at zero and ends at the source
38292 location of the first branch in the trace buffer. This extra block is
38293 used to stitch traces together.
38295 If the trace buffer overflowed, returns an error indicating the overflow.
38298 This packet is not probed by default; the remote stub must request it
38299 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38301 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38302 @anchor{qXfer btrace-conf read}
38304 Return a description of the current branch trace configuration.
38305 @xref{Branch Trace Configuration Format}.
38307 This packet is not probed by default; the remote stub must request it
38308 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38310 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38311 @anchor{qXfer executable filename read}
38312 Return the full absolute name of the file that was executed to create
38313 a process running on the remote system. The annex specifies the
38314 numeric process ID of the process to query, encoded as a hexadecimal
38315 number. If the annex part is empty the remote stub should return the
38316 filename corresponding to the currently executing process.
38318 This packet is not probed by default; the remote stub must request it,
38319 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38321 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38322 @anchor{qXfer target description read}
38323 Access the @dfn{target description}. @xref{Target Descriptions}. The
38324 annex specifies which XML document to access. The main description is
38325 always loaded from the @samp{target.xml} annex.
38327 This packet is not probed by default; the remote stub must request it,
38328 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38330 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38331 @anchor{qXfer library list read}
38332 Access the target's list of loaded libraries. @xref{Library List Format}.
38333 The annex part of the generic @samp{qXfer} packet must be empty
38334 (@pxref{qXfer read}).
38336 Targets which maintain a list of libraries in the program's memory do
38337 not need to implement this packet; it is designed for platforms where
38338 the operating system manages the list of loaded libraries.
38340 This packet is not probed by default; the remote stub must request it,
38341 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38343 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38344 @anchor{qXfer svr4 library list read}
38345 Access the target's list of loaded libraries when the target is an SVR4
38346 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38347 of the generic @samp{qXfer} packet must be empty unless the remote
38348 stub indicated it supports the augmented form of this packet
38349 by supplying an appropriate @samp{qSupported} response
38350 (@pxref{qXfer read}, @ref{qSupported}).
38352 This packet is optional for better performance on SVR4 targets.
38353 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38355 This packet is not probed by default; the remote stub must request it,
38356 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38358 If the remote stub indicates it supports the augmented form of this
38359 packet then the annex part of the generic @samp{qXfer} packet may
38360 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38361 arguments. The currently supported arguments are:
38364 @item start=@var{address}
38365 A hexadecimal number specifying the address of the @samp{struct
38366 link_map} to start reading the library list from. If unset or zero
38367 then the first @samp{struct link_map} in the library list will be
38368 chosen as the starting point.
38370 @item prev=@var{address}
38371 A hexadecimal number specifying the address of the @samp{struct
38372 link_map} immediately preceding the @samp{struct link_map}
38373 specified by the @samp{start} argument. If unset or zero then
38374 the remote stub will expect that no @samp{struct link_map}
38375 exists prior to the starting point.
38379 Arguments that are not understood by the remote stub will be silently
38382 @item qXfer:memory-map:read::@var{offset},@var{length}
38383 @anchor{qXfer memory map read}
38384 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38385 annex part of the generic @samp{qXfer} packet must be empty
38386 (@pxref{qXfer read}).
38388 This packet is not probed by default; the remote stub must request it,
38389 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38391 @item qXfer:sdata:read::@var{offset},@var{length}
38392 @anchor{qXfer sdata read}
38394 Read contents of the extra collected static tracepoint marker
38395 information. The annex part of the generic @samp{qXfer} packet must
38396 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38399 This packet is not probed by default; the remote stub must request it,
38400 by supplying an appropriate @samp{qSupported} response
38401 (@pxref{qSupported}).
38403 @item qXfer:siginfo:read::@var{offset},@var{length}
38404 @anchor{qXfer siginfo read}
38405 Read contents of the extra signal information on the target
38406 system. The annex part of the generic @samp{qXfer} packet must be
38407 empty (@pxref{qXfer read}).
38409 This packet is not probed by default; the remote stub must request it,
38410 by supplying an appropriate @samp{qSupported} response
38411 (@pxref{qSupported}).
38413 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38414 @anchor{qXfer spu read}
38415 Read contents of an @code{spufs} file on the target system. The
38416 annex specifies which file to read; it must be of the form
38417 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38418 in the target process, and @var{name} identifes the @code{spufs} file
38419 in that context to be accessed.
38421 This packet is not probed by default; the remote stub must request it,
38422 by supplying an appropriate @samp{qSupported} response
38423 (@pxref{qSupported}).
38425 @item qXfer:threads:read::@var{offset},@var{length}
38426 @anchor{qXfer threads read}
38427 Access the list of threads on target. @xref{Thread List Format}. The
38428 annex part of the generic @samp{qXfer} packet must be empty
38429 (@pxref{qXfer read}).
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:traceframe-info:read::@var{offset},@var{length}
38435 @anchor{qXfer traceframe info read}
38437 Return a description of the current traceframe's contents.
38438 @xref{Traceframe Info Format}. The annex part of the generic
38439 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38441 This packet is not probed by default; the remote stub must request it,
38442 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38444 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38445 @anchor{qXfer unwind info block}
38447 Return the unwind information block for @var{pc}. This packet is used
38448 on OpenVMS/ia64 to ask the kernel unwind information.
38450 This packet is not probed by default.
38452 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38453 @anchor{qXfer fdpic loadmap read}
38454 Read contents of @code{loadmap}s on the target system. The
38455 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38456 executable @code{loadmap} or interpreter @code{loadmap} to read.
38458 This packet is not probed by default; the remote stub must request it,
38459 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38461 @item qXfer:osdata:read::@var{offset},@var{length}
38462 @anchor{qXfer osdata read}
38463 Access the target's @dfn{operating system information}.
38464 @xref{Operating System Information}.
38468 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38469 @cindex write data into object, remote request
38470 @anchor{qXfer write}
38471 Write uninterpreted bytes into the target's special data area
38472 identified by the keyword @var{object}, starting at @var{offset} bytes
38473 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38474 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38475 is specific to @var{object}; it can supply additional details about what data
38481 @var{nn} (hex encoded) is the number of bytes written.
38482 This may be fewer bytes than supplied in the request.
38485 The request was malformed, or @var{annex} was invalid.
38488 The offset was invalid, or there was an error encountered writing the data.
38489 The @var{nn} part is a hex-encoded @code{errno} value.
38492 An empty reply indicates the @var{object} string was not
38493 recognized by the stub, or that the object does not support writing.
38496 Here are the specific requests of this form defined so far. All the
38497 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38498 formats, listed above.
38501 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38502 @anchor{qXfer siginfo write}
38503 Write @var{data} to the extra signal information on the target system.
38504 The annex part of the generic @samp{qXfer} packet must be
38505 empty (@pxref{qXfer write}).
38507 This packet is not probed by default; the remote stub must request it,
38508 by supplying an appropriate @samp{qSupported} response
38509 (@pxref{qSupported}).
38511 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38512 @anchor{qXfer spu write}
38513 Write @var{data} to an @code{spufs} file on the target system. The
38514 annex specifies which file to write; it must be of the form
38515 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38516 in the target process, and @var{name} identifes the @code{spufs} file
38517 in that context to be accessed.
38519 This packet is not probed by default; the remote stub must request it,
38520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38523 @item qXfer:@var{object}:@var{operation}:@dots{}
38524 Requests of this form may be added in the future. When a stub does
38525 not recognize the @var{object} keyword, or its support for
38526 @var{object} does not recognize the @var{operation} keyword, the stub
38527 must respond with an empty packet.
38529 @item qAttached:@var{pid}
38530 @cindex query attached, remote request
38531 @cindex @samp{qAttached} packet
38532 Return an indication of whether the remote server attached to an
38533 existing process or created a new process. When the multiprocess
38534 protocol extensions are supported (@pxref{multiprocess extensions}),
38535 @var{pid} is an integer in hexadecimal format identifying the target
38536 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38537 the query packet will be simplified as @samp{qAttached}.
38539 This query is used, for example, to know whether the remote process
38540 should be detached or killed when a @value{GDBN} session is ended with
38541 the @code{quit} command.
38546 The remote server attached to an existing process.
38548 The remote server created a new process.
38550 A badly formed request or an error was encountered.
38554 Enable branch tracing for the current thread using Branch Trace Store.
38559 Branch tracing has been enabled.
38561 A badly formed request or an error was encountered.
38565 Enable branch tracing for the current thread using Intel Processor Trace.
38570 Branch tracing has been enabled.
38572 A badly formed request or an error was encountered.
38576 Disable branch tracing for the current thread.
38581 Branch tracing has been disabled.
38583 A badly formed request or an error was encountered.
38586 @item Qbtrace-conf:bts:size=@var{value}
38587 Set the requested ring buffer size for new threads that use the
38588 btrace recording method in bts format.
38593 The ring buffer size has been set.
38595 A badly formed request or an error was encountered.
38598 @item Qbtrace-conf:pt:size=@var{value}
38599 Set the requested ring buffer size for new threads that use the
38600 btrace recording method in pt format.
38605 The ring buffer size has been set.
38607 A badly formed request or an error was encountered.
38612 @node Architecture-Specific Protocol Details
38613 @section Architecture-Specific Protocol Details
38615 This section describes how the remote protocol is applied to specific
38616 target architectures. Also see @ref{Standard Target Features}, for
38617 details of XML target descriptions for each architecture.
38620 * ARM-Specific Protocol Details::
38621 * MIPS-Specific Protocol Details::
38624 @node ARM-Specific Protocol Details
38625 @subsection @acronym{ARM}-specific Protocol Details
38628 * ARM Breakpoint Kinds::
38631 @node ARM Breakpoint Kinds
38632 @subsubsection @acronym{ARM} Breakpoint Kinds
38633 @cindex breakpoint kinds, @acronym{ARM}
38635 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38640 16-bit Thumb mode breakpoint.
38643 32-bit Thumb mode (Thumb-2) breakpoint.
38646 32-bit @acronym{ARM} mode breakpoint.
38650 @node MIPS-Specific Protocol Details
38651 @subsection @acronym{MIPS}-specific Protocol Details
38654 * MIPS Register packet Format::
38655 * MIPS Breakpoint Kinds::
38658 @node MIPS Register packet Format
38659 @subsubsection @acronym{MIPS} Register Packet Format
38660 @cindex register packet format, @acronym{MIPS}
38662 The following @code{g}/@code{G} packets have previously been defined.
38663 In the below, some thirty-two bit registers are transferred as
38664 sixty-four bits. Those registers should be zero/sign extended (which?)
38665 to fill the space allocated. Register bytes are transferred in target
38666 byte order. The two nibbles within a register byte are transferred
38667 most-significant -- least-significant.
38672 All registers are transferred as thirty-two bit quantities in the order:
38673 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38674 registers; fsr; fir; fp.
38677 All registers are transferred as sixty-four bit quantities (including
38678 thirty-two bit registers such as @code{sr}). The ordering is the same
38683 @node MIPS Breakpoint Kinds
38684 @subsubsection @acronym{MIPS} Breakpoint Kinds
38685 @cindex breakpoint kinds, @acronym{MIPS}
38687 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38692 16-bit @acronym{MIPS16} mode breakpoint.
38695 16-bit @acronym{microMIPS} mode breakpoint.
38698 32-bit standard @acronym{MIPS} mode breakpoint.
38701 32-bit @acronym{microMIPS} mode breakpoint.
38705 @node Tracepoint Packets
38706 @section Tracepoint Packets
38707 @cindex tracepoint packets
38708 @cindex packets, tracepoint
38710 Here we describe the packets @value{GDBN} uses to implement
38711 tracepoints (@pxref{Tracepoints}).
38715 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38716 @cindex @samp{QTDP} packet
38717 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38718 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38719 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38720 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38721 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38722 the number of bytes that the target should copy elsewhere to make room
38723 for the tracepoint. If an @samp{X} is present, it introduces a
38724 tracepoint condition, which consists of a hexadecimal length, followed
38725 by a comma and hex-encoded bytes, in a manner similar to action
38726 encodings as described below. If the trailing @samp{-} is present,
38727 further @samp{QTDP} packets will follow to specify this tracepoint's
38733 The packet was understood and carried out.
38735 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38737 The packet was not recognized.
38740 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38741 Define actions to be taken when a tracepoint is hit. The @var{n} and
38742 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38743 this tracepoint. This packet may only be sent immediately after
38744 another @samp{QTDP} packet that ended with a @samp{-}. If the
38745 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38746 specifying more actions for this tracepoint.
38748 In the series of action packets for a given tracepoint, at most one
38749 can have an @samp{S} before its first @var{action}. If such a packet
38750 is sent, it and the following packets define ``while-stepping''
38751 actions. Any prior packets define ordinary actions --- that is, those
38752 taken when the tracepoint is first hit. If no action packet has an
38753 @samp{S}, then all the packets in the series specify ordinary
38754 tracepoint actions.
38756 The @samp{@var{action}@dots{}} portion of the packet is a series of
38757 actions, concatenated without separators. Each action has one of the
38763 Collect the registers whose bits are set in @var{mask},
38764 a hexadecimal number whose @var{i}'th bit is set if register number
38765 @var{i} should be collected. (The least significant bit is numbered
38766 zero.) Note that @var{mask} may be any number of digits long; it may
38767 not fit in a 32-bit word.
38769 @item M @var{basereg},@var{offset},@var{len}
38770 Collect @var{len} bytes of memory starting at the address in register
38771 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38772 @samp{-1}, then the range has a fixed address: @var{offset} is the
38773 address of the lowest byte to collect. The @var{basereg},
38774 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38775 values (the @samp{-1} value for @var{basereg} is a special case).
38777 @item X @var{len},@var{expr}
38778 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38779 it directs. The agent expression @var{expr} is as described in
38780 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38781 two-digit hex number in the packet; @var{len} is the number of bytes
38782 in the expression (and thus one-half the number of hex digits in the
38787 Any number of actions may be packed together in a single @samp{QTDP}
38788 packet, as long as the packet does not exceed the maximum packet
38789 length (400 bytes, for many stubs). There may be only one @samp{R}
38790 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38791 actions. Any registers referred to by @samp{M} and @samp{X} actions
38792 must be collected by a preceding @samp{R} action. (The
38793 ``while-stepping'' actions are treated as if they were attached to a
38794 separate tracepoint, as far as these restrictions are concerned.)
38799 The packet was understood and carried out.
38801 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38803 The packet was not recognized.
38806 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38807 @cindex @samp{QTDPsrc} packet
38808 Specify a source string of tracepoint @var{n} at address @var{addr}.
38809 This is useful to get accurate reproduction of the tracepoints
38810 originally downloaded at the beginning of the trace run. The @var{type}
38811 is the name of the tracepoint part, such as @samp{cond} for the
38812 tracepoint's conditional expression (see below for a list of types), while
38813 @var{bytes} is the string, encoded in hexadecimal.
38815 @var{start} is the offset of the @var{bytes} within the overall source
38816 string, while @var{slen} is the total length of the source string.
38817 This is intended for handling source strings that are longer than will
38818 fit in a single packet.
38819 @c Add detailed example when this info is moved into a dedicated
38820 @c tracepoint descriptions section.
38822 The available string types are @samp{at} for the location,
38823 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38824 @value{GDBN} sends a separate packet for each command in the action
38825 list, in the same order in which the commands are stored in the list.
38827 The target does not need to do anything with source strings except
38828 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38831 Although this packet is optional, and @value{GDBN} will only send it
38832 if the target replies with @samp{TracepointSource} @xref{General
38833 Query Packets}, it makes both disconnected tracing and trace files
38834 much easier to use. Otherwise the user must be careful that the
38835 tracepoints in effect while looking at trace frames are identical to
38836 the ones in effect during the trace run; even a small discrepancy
38837 could cause @samp{tdump} not to work, or a particular trace frame not
38840 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38841 @cindex define trace state variable, remote request
38842 @cindex @samp{QTDV} packet
38843 Create a new trace state variable, number @var{n}, with an initial
38844 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38845 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38846 the option of not using this packet for initial values of zero; the
38847 target should simply create the trace state variables as they are
38848 mentioned in expressions. The value @var{builtin} should be 1 (one)
38849 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38850 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38851 @samp{qTsV} packet had it set. The contents of @var{name} is the
38852 hex-encoded name (without the leading @samp{$}) of the trace state
38855 @item QTFrame:@var{n}
38856 @cindex @samp{QTFrame} packet
38857 Select the @var{n}'th tracepoint frame from the buffer, and use the
38858 register and memory contents recorded there to answer subsequent
38859 request packets from @value{GDBN}.
38861 A successful reply from the stub indicates that the stub has found the
38862 requested frame. The response is a series of parts, concatenated
38863 without separators, describing the frame we selected. Each part has
38864 one of the following forms:
38868 The selected frame is number @var{n} in the trace frame buffer;
38869 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38870 was no frame matching the criteria in the request packet.
38873 The selected trace frame records a hit of tracepoint number @var{t};
38874 @var{t} is a hexadecimal number.
38878 @item QTFrame:pc:@var{addr}
38879 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38880 currently selected frame whose PC is @var{addr};
38881 @var{addr} is a hexadecimal number.
38883 @item QTFrame:tdp:@var{t}
38884 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38885 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38886 is a hexadecimal number.
38888 @item QTFrame:range:@var{start}:@var{end}
38889 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38890 currently selected frame whose PC is between @var{start} (inclusive)
38891 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38894 @item QTFrame:outside:@var{start}:@var{end}
38895 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38896 frame @emph{outside} the given range of addresses (exclusive).
38899 @cindex @samp{qTMinFTPILen} packet
38900 This packet requests the minimum length of instruction at which a fast
38901 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38902 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38903 it depends on the target system being able to create trampolines in
38904 the first 64K of memory, which might or might not be possible for that
38905 system. So the reply to this packet will be 4 if it is able to
38912 The minimum instruction length is currently unknown.
38914 The minimum instruction length is @var{length}, where @var{length}
38915 is a hexadecimal number greater or equal to 1. A reply
38916 of 1 means that a fast tracepoint may be placed on any instruction
38917 regardless of size.
38919 An error has occurred.
38921 An empty reply indicates that the request is not supported by the stub.
38925 @cindex @samp{QTStart} packet
38926 Begin the tracepoint experiment. Begin collecting data from
38927 tracepoint hits in the trace frame buffer. This packet supports the
38928 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38929 instruction reply packet}).
38932 @cindex @samp{QTStop} packet
38933 End the tracepoint experiment. Stop collecting trace frames.
38935 @item QTEnable:@var{n}:@var{addr}
38937 @cindex @samp{QTEnable} packet
38938 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38939 experiment. If the tracepoint was previously disabled, then collection
38940 of data from it will resume.
38942 @item QTDisable:@var{n}:@var{addr}
38944 @cindex @samp{QTDisable} packet
38945 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38946 experiment. No more data will be collected from the tracepoint unless
38947 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38950 @cindex @samp{QTinit} packet
38951 Clear the table of tracepoints, and empty the trace frame buffer.
38953 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38954 @cindex @samp{QTro} packet
38955 Establish the given ranges of memory as ``transparent''. The stub
38956 will answer requests for these ranges from memory's current contents,
38957 if they were not collected as part of the tracepoint hit.
38959 @value{GDBN} uses this to mark read-only regions of memory, like those
38960 containing program code. Since these areas never change, they should
38961 still have the same contents they did when the tracepoint was hit, so
38962 there's no reason for the stub to refuse to provide their contents.
38964 @item QTDisconnected:@var{value}
38965 @cindex @samp{QTDisconnected} packet
38966 Set the choice to what to do with the tracing run when @value{GDBN}
38967 disconnects from the target. A @var{value} of 1 directs the target to
38968 continue the tracing run, while 0 tells the target to stop tracing if
38969 @value{GDBN} is no longer in the picture.
38972 @cindex @samp{qTStatus} packet
38973 Ask the stub if there is a trace experiment running right now.
38975 The reply has the form:
38979 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38980 @var{running} is a single digit @code{1} if the trace is presently
38981 running, or @code{0} if not. It is followed by semicolon-separated
38982 optional fields that an agent may use to report additional status.
38986 If the trace is not running, the agent may report any of several
38987 explanations as one of the optional fields:
38992 No trace has been run yet.
38994 @item tstop[:@var{text}]:0
38995 The trace was stopped by a user-originated stop command. The optional
38996 @var{text} field is a user-supplied string supplied as part of the
38997 stop command (for instance, an explanation of why the trace was
38998 stopped manually). It is hex-encoded.
39001 The trace stopped because the trace buffer filled up.
39003 @item tdisconnected:0
39004 The trace stopped because @value{GDBN} disconnected from the target.
39006 @item tpasscount:@var{tpnum}
39007 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39009 @item terror:@var{text}:@var{tpnum}
39010 The trace stopped because tracepoint @var{tpnum} had an error. The
39011 string @var{text} is available to describe the nature of the error
39012 (for instance, a divide by zero in the condition expression); it
39016 The trace stopped for some other reason.
39020 Additional optional fields supply statistical and other information.
39021 Although not required, they are extremely useful for users monitoring
39022 the progress of a trace run. If a trace has stopped, and these
39023 numbers are reported, they must reflect the state of the just-stopped
39028 @item tframes:@var{n}
39029 The number of trace frames in the buffer.
39031 @item tcreated:@var{n}
39032 The total number of trace frames created during the run. This may
39033 be larger than the trace frame count, if the buffer is circular.
39035 @item tsize:@var{n}
39036 The total size of the trace buffer, in bytes.
39038 @item tfree:@var{n}
39039 The number of bytes still unused in the buffer.
39041 @item circular:@var{n}
39042 The value of the circular trace buffer flag. @code{1} means that the
39043 trace buffer is circular and old trace frames will be discarded if
39044 necessary to make room, @code{0} means that the trace buffer is linear
39047 @item disconn:@var{n}
39048 The value of the disconnected tracing flag. @code{1} means that
39049 tracing will continue after @value{GDBN} disconnects, @code{0} means
39050 that the trace run will stop.
39054 @item qTP:@var{tp}:@var{addr}
39055 @cindex tracepoint status, remote request
39056 @cindex @samp{qTP} packet
39057 Ask the stub for the current state of tracepoint number @var{tp} at
39058 address @var{addr}.
39062 @item V@var{hits}:@var{usage}
39063 The tracepoint has been hit @var{hits} times so far during the trace
39064 run, and accounts for @var{usage} in the trace buffer. Note that
39065 @code{while-stepping} steps are not counted as separate hits, but the
39066 steps' space consumption is added into the usage number.
39070 @item qTV:@var{var}
39071 @cindex trace state variable value, remote request
39072 @cindex @samp{qTV} packet
39073 Ask the stub for the value of the trace state variable number @var{var}.
39078 The value of the variable is @var{value}. This will be the current
39079 value of the variable if the user is examining a running target, or a
39080 saved value if the variable was collected in the trace frame that the
39081 user is looking at. Note that multiple requests may result in
39082 different reply values, such as when requesting values while the
39083 program is running.
39086 The value of the variable is unknown. This would occur, for example,
39087 if the user is examining a trace frame in which the requested variable
39092 @cindex @samp{qTfP} packet
39094 @cindex @samp{qTsP} packet
39095 These packets request data about tracepoints that are being used by
39096 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39097 of data, and multiple @code{qTsP} to get additional pieces. Replies
39098 to these packets generally take the form of the @code{QTDP} packets
39099 that define tracepoints. (FIXME add detailed syntax)
39102 @cindex @samp{qTfV} packet
39104 @cindex @samp{qTsV} packet
39105 These packets request data about trace state variables that are on the
39106 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39107 and multiple @code{qTsV} to get additional variables. Replies to
39108 these packets follow the syntax of the @code{QTDV} packets that define
39109 trace state variables.
39115 @cindex @samp{qTfSTM} packet
39116 @cindex @samp{qTsSTM} packet
39117 These packets request data about static tracepoint markers that exist
39118 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39119 first piece of data, and multiple @code{qTsSTM} to get additional
39120 pieces. Replies to these packets take the following form:
39124 @item m @var{address}:@var{id}:@var{extra}
39126 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39127 a comma-separated list of markers
39129 (lower case letter @samp{L}) denotes end of list.
39131 An error occurred. The error number @var{nn} is given as hex digits.
39133 An empty reply indicates that the request is not supported by the
39137 The @var{address} is encoded in hex;
39138 @var{id} and @var{extra} are strings encoded in hex.
39140 In response to each query, the target will reply with a list of one or
39141 more markers, separated by commas. @value{GDBN} will respond to each
39142 reply with a request for more markers (using the @samp{qs} form of the
39143 query), until the target responds with @samp{l} (lower-case ell, for
39146 @item qTSTMat:@var{address}
39148 @cindex @samp{qTSTMat} packet
39149 This packets requests data about static tracepoint markers in the
39150 target program at @var{address}. Replies to this packet follow the
39151 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39152 tracepoint markers.
39154 @item QTSave:@var{filename}
39155 @cindex @samp{QTSave} packet
39156 This packet directs the target to save trace data to the file name
39157 @var{filename} in the target's filesystem. The @var{filename} is encoded
39158 as a hex string; the interpretation of the file name (relative vs
39159 absolute, wild cards, etc) is up to the target.
39161 @item qTBuffer:@var{offset},@var{len}
39162 @cindex @samp{qTBuffer} packet
39163 Return up to @var{len} bytes of the current contents of trace buffer,
39164 starting at @var{offset}. The trace buffer is treated as if it were
39165 a contiguous collection of traceframes, as per the trace file format.
39166 The reply consists as many hex-encoded bytes as the target can deliver
39167 in a packet; it is not an error to return fewer than were asked for.
39168 A reply consisting of just @code{l} indicates that no bytes are
39171 @item QTBuffer:circular:@var{value}
39172 This packet directs the target to use a circular trace buffer if
39173 @var{value} is 1, or a linear buffer if the value is 0.
39175 @item QTBuffer:size:@var{size}
39176 @anchor{QTBuffer-size}
39177 @cindex @samp{QTBuffer size} packet
39178 This packet directs the target to make the trace buffer be of size
39179 @var{size} if possible. A value of @code{-1} tells the target to
39180 use whatever size it prefers.
39182 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39183 @cindex @samp{QTNotes} packet
39184 This packet adds optional textual notes to the trace run. Allowable
39185 types include @code{user}, @code{notes}, and @code{tstop}, the
39186 @var{text} fields are arbitrary strings, hex-encoded.
39190 @subsection Relocate instruction reply packet
39191 When installing fast tracepoints in memory, the target may need to
39192 relocate the instruction currently at the tracepoint address to a
39193 different address in memory. For most instructions, a simple copy is
39194 enough, but, for example, call instructions that implicitly push the
39195 return address on the stack, and relative branches or other
39196 PC-relative instructions require offset adjustment, so that the effect
39197 of executing the instruction at a different address is the same as if
39198 it had executed in the original location.
39200 In response to several of the tracepoint packets, the target may also
39201 respond with a number of intermediate @samp{qRelocInsn} request
39202 packets before the final result packet, to have @value{GDBN} handle
39203 this relocation operation. If a packet supports this mechanism, its
39204 documentation will explicitly say so. See for example the above
39205 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39206 format of the request is:
39209 @item qRelocInsn:@var{from};@var{to}
39211 This requests @value{GDBN} to copy instruction at address @var{from}
39212 to address @var{to}, possibly adjusted so that executing the
39213 instruction at @var{to} has the same effect as executing it at
39214 @var{from}. @value{GDBN} writes the adjusted instruction to target
39215 memory starting at @var{to}.
39220 @item qRelocInsn:@var{adjusted_size}
39221 Informs the stub the relocation is complete. The @var{adjusted_size} is
39222 the length in bytes of resulting relocated instruction sequence.
39224 A badly formed request was detected, or an error was encountered while
39225 relocating the instruction.
39228 @node Host I/O Packets
39229 @section Host I/O Packets
39230 @cindex Host I/O, remote protocol
39231 @cindex file transfer, remote protocol
39233 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39234 operations on the far side of a remote link. For example, Host I/O is
39235 used to upload and download files to a remote target with its own
39236 filesystem. Host I/O uses the same constant values and data structure
39237 layout as the target-initiated File-I/O protocol. However, the
39238 Host I/O packets are structured differently. The target-initiated
39239 protocol relies on target memory to store parameters and buffers.
39240 Host I/O requests are initiated by @value{GDBN}, and the
39241 target's memory is not involved. @xref{File-I/O Remote Protocol
39242 Extension}, for more details on the target-initiated protocol.
39244 The Host I/O request packets all encode a single operation along with
39245 its arguments. They have this format:
39249 @item vFile:@var{operation}: @var{parameter}@dots{}
39250 @var{operation} is the name of the particular request; the target
39251 should compare the entire packet name up to the second colon when checking
39252 for a supported operation. The format of @var{parameter} depends on
39253 the operation. Numbers are always passed in hexadecimal. Negative
39254 numbers have an explicit minus sign (i.e.@: two's complement is not
39255 used). Strings (e.g.@: filenames) are encoded as a series of
39256 hexadecimal bytes. The last argument to a system call may be a
39257 buffer of escaped binary data (@pxref{Binary Data}).
39261 The valid responses to Host I/O packets are:
39265 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39266 @var{result} is the integer value returned by this operation, usually
39267 non-negative for success and -1 for errors. If an error has occured,
39268 @var{errno} will be included in the result specifying a
39269 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39270 operations which return data, @var{attachment} supplies the data as a
39271 binary buffer. Binary buffers in response packets are escaped in the
39272 normal way (@pxref{Binary Data}). See the individual packet
39273 documentation for the interpretation of @var{result} and
39277 An empty response indicates that this operation is not recognized.
39281 These are the supported Host I/O operations:
39284 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39285 Open a file at @var{filename} and return a file descriptor for it, or
39286 return -1 if an error occurs. The @var{filename} is a string,
39287 @var{flags} is an integer indicating a mask of open flags
39288 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39289 of mode bits to use if the file is created (@pxref{mode_t Values}).
39290 @xref{open}, for details of the open flags and mode values.
39292 @item vFile:close: @var{fd}
39293 Close the open file corresponding to @var{fd} and return 0, or
39294 -1 if an error occurs.
39296 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39297 Read data from the open file corresponding to @var{fd}. Up to
39298 @var{count} bytes will be read from the file, starting at @var{offset}
39299 relative to the start of the file. The target may read fewer bytes;
39300 common reasons include packet size limits and an end-of-file
39301 condition. The number of bytes read is returned. Zero should only be
39302 returned for a successful read at the end of the file, or if
39303 @var{count} was zero.
39305 The data read should be returned as a binary attachment on success.
39306 If zero bytes were read, the response should include an empty binary
39307 attachment (i.e.@: a trailing semicolon). The return value is the
39308 number of target bytes read; the binary attachment may be longer if
39309 some characters were escaped.
39311 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39312 Write @var{data} (a binary buffer) to the open file corresponding
39313 to @var{fd}. Start the write at @var{offset} from the start of the
39314 file. Unlike many @code{write} system calls, there is no
39315 separate @var{count} argument; the length of @var{data} in the
39316 packet is used. @samp{vFile:write} returns the number of bytes written,
39317 which may be shorter than the length of @var{data}, or -1 if an
39320 @item vFile:fstat: @var{fd}
39321 Get information about the open file corresponding to @var{fd}.
39322 On success the information is returned as a binary attachment
39323 and the return value is the size of this attachment in bytes.
39324 If an error occurs the return value is -1. The format of the
39325 returned binary attachment is as described in @ref{struct stat}.
39327 @item vFile:unlink: @var{filename}
39328 Delete the file at @var{filename} on the target. Return 0,
39329 or -1 if an error occurs. The @var{filename} is a string.
39331 @item vFile:readlink: @var{filename}
39332 Read value of symbolic link @var{filename} on the target. Return
39333 the number of bytes read, or -1 if an error occurs.
39335 The data read should be returned as a binary attachment on success.
39336 If zero bytes were read, the response should include an empty binary
39337 attachment (i.e.@: a trailing semicolon). The return value is the
39338 number of target bytes read; the binary attachment may be longer if
39339 some characters were escaped.
39341 @item vFile:setfs: @var{pid}
39342 Select the filesystem on which @code{vFile} operations with
39343 @var{filename} arguments will operate. This is required for
39344 @value{GDBN} to be able to access files on remote targets where
39345 the remote stub does not share a common filesystem with the
39348 If @var{pid} is nonzero, select the filesystem as seen by process
39349 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39350 the remote stub. Return 0 on success, or -1 if an error occurs.
39351 If @code{vFile:setfs:} indicates success, the selected filesystem
39352 remains selected until the next successful @code{vFile:setfs:}
39358 @section Interrupts
39359 @cindex interrupts (remote protocol)
39360 @anchor{interrupting remote targets}
39362 In all-stop mode, when a program on the remote target is running,
39363 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39364 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39365 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39367 The precise meaning of @code{BREAK} is defined by the transport
39368 mechanism and may, in fact, be undefined. @value{GDBN} does not
39369 currently define a @code{BREAK} mechanism for any of the network
39370 interfaces except for TCP, in which case @value{GDBN} sends the
39371 @code{telnet} BREAK sequence.
39373 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39374 transport mechanisms. It is represented by sending the single byte
39375 @code{0x03} without any of the usual packet overhead described in
39376 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39377 transmitted as part of a packet, it is considered to be packet data
39378 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39379 (@pxref{X packet}), used for binary downloads, may include an unescaped
39380 @code{0x03} as part of its packet.
39382 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39383 When Linux kernel receives this sequence from serial port,
39384 it stops execution and connects to gdb.
39386 In non-stop mode, because packet resumptions are asynchronous
39387 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39388 command to the remote stub, even when the target is running. For that
39389 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39390 packet}) with the usual packet framing instead of the single byte
39393 Stubs are not required to recognize these interrupt mechanisms and the
39394 precise meaning associated with receipt of the interrupt is
39395 implementation defined. If the target supports debugging of multiple
39396 threads and/or processes, it should attempt to interrupt all
39397 currently-executing threads and processes.
39398 If the stub is successful at interrupting the
39399 running program, it should send one of the stop
39400 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39401 of successfully stopping the program in all-stop mode, and a stop reply
39402 for each stopped thread in non-stop mode.
39403 Interrupts received while the
39404 program is stopped are queued and the program will be interrupted when
39405 it is resumed next time.
39407 @node Notification Packets
39408 @section Notification Packets
39409 @cindex notification packets
39410 @cindex packets, notification
39412 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39413 packets that require no acknowledgment. Both the GDB and the stub
39414 may send notifications (although the only notifications defined at
39415 present are sent by the stub). Notifications carry information
39416 without incurring the round-trip latency of an acknowledgment, and so
39417 are useful for low-impact communications where occasional packet loss
39420 A notification packet has the form @samp{% @var{data} #
39421 @var{checksum}}, where @var{data} is the content of the notification,
39422 and @var{checksum} is a checksum of @var{data}, computed and formatted
39423 as for ordinary @value{GDBN} packets. A notification's @var{data}
39424 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39425 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39426 to acknowledge the notification's receipt or to report its corruption.
39428 Every notification's @var{data} begins with a name, which contains no
39429 colon characters, followed by a colon character.
39431 Recipients should silently ignore corrupted notifications and
39432 notifications they do not understand. Recipients should restart
39433 timeout periods on receipt of a well-formed notification, whether or
39434 not they understand it.
39436 Senders should only send the notifications described here when this
39437 protocol description specifies that they are permitted. In the
39438 future, we may extend the protocol to permit existing notifications in
39439 new contexts; this rule helps older senders avoid confusing newer
39442 (Older versions of @value{GDBN} ignore bytes received until they see
39443 the @samp{$} byte that begins an ordinary packet, so new stubs may
39444 transmit notifications without fear of confusing older clients. There
39445 are no notifications defined for @value{GDBN} to send at the moment, but we
39446 assume that most older stubs would ignore them, as well.)
39448 Each notification is comprised of three parts:
39450 @item @var{name}:@var{event}
39451 The notification packet is sent by the side that initiates the
39452 exchange (currently, only the stub does that), with @var{event}
39453 carrying the specific information about the notification, and
39454 @var{name} specifying the name of the notification.
39456 The acknowledge sent by the other side, usually @value{GDBN}, to
39457 acknowledge the exchange and request the event.
39460 The purpose of an asynchronous notification mechanism is to report to
39461 @value{GDBN} that something interesting happened in the remote stub.
39463 The remote stub may send notification @var{name}:@var{event}
39464 at any time, but @value{GDBN} acknowledges the notification when
39465 appropriate. The notification event is pending before @value{GDBN}
39466 acknowledges. Only one notification at a time may be pending; if
39467 additional events occur before @value{GDBN} has acknowledged the
39468 previous notification, they must be queued by the stub for later
39469 synchronous transmission in response to @var{ack} packets from
39470 @value{GDBN}. Because the notification mechanism is unreliable,
39471 the stub is permitted to resend a notification if it believes
39472 @value{GDBN} may not have received it.
39474 Specifically, notifications may appear when @value{GDBN} is not
39475 otherwise reading input from the stub, or when @value{GDBN} is
39476 expecting to read a normal synchronous response or a
39477 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39478 Notification packets are distinct from any other communication from
39479 the stub so there is no ambiguity.
39481 After receiving a notification, @value{GDBN} shall acknowledge it by
39482 sending a @var{ack} packet as a regular, synchronous request to the
39483 stub. Such acknowledgment is not required to happen immediately, as
39484 @value{GDBN} is permitted to send other, unrelated packets to the
39485 stub first, which the stub should process normally.
39487 Upon receiving a @var{ack} packet, if the stub has other queued
39488 events to report to @value{GDBN}, it shall respond by sending a
39489 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39490 packet to solicit further responses; again, it is permitted to send
39491 other, unrelated packets as well which the stub should process
39494 If the stub receives a @var{ack} packet and there are no additional
39495 @var{event} to report, the stub shall return an @samp{OK} response.
39496 At this point, @value{GDBN} has finished processing a notification
39497 and the stub has completed sending any queued events. @value{GDBN}
39498 won't accept any new notifications until the final @samp{OK} is
39499 received . If further notification events occur, the stub shall send
39500 a new notification, @value{GDBN} shall accept the notification, and
39501 the process shall be repeated.
39503 The process of asynchronous notification can be illustrated by the
39506 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39509 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39511 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39516 The following notifications are defined:
39517 @multitable @columnfractions 0.12 0.12 0.38 0.38
39526 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39527 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39528 for information on how these notifications are acknowledged by
39530 @tab Report an asynchronous stop event in non-stop mode.
39534 @node Remote Non-Stop
39535 @section Remote Protocol Support for Non-Stop Mode
39537 @value{GDBN}'s remote protocol supports non-stop debugging of
39538 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39539 supports non-stop mode, it should report that to @value{GDBN} by including
39540 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39542 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39543 establishing a new connection with the stub. Entering non-stop mode
39544 does not alter the state of any currently-running threads, but targets
39545 must stop all threads in any already-attached processes when entering
39546 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39547 probe the target state after a mode change.
39549 In non-stop mode, when an attached process encounters an event that
39550 would otherwise be reported with a stop reply, it uses the
39551 asynchronous notification mechanism (@pxref{Notification Packets}) to
39552 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39553 in all processes are stopped when a stop reply is sent, in non-stop
39554 mode only the thread reporting the stop event is stopped. That is,
39555 when reporting a @samp{S} or @samp{T} response to indicate completion
39556 of a step operation, hitting a breakpoint, or a fault, only the
39557 affected thread is stopped; any other still-running threads continue
39558 to run. When reporting a @samp{W} or @samp{X} response, all running
39559 threads belonging to other attached processes continue to run.
39561 In non-stop mode, the target shall respond to the @samp{?} packet as
39562 follows. First, any incomplete stop reply notification/@samp{vStopped}
39563 sequence in progress is abandoned. The target must begin a new
39564 sequence reporting stop events for all stopped threads, whether or not
39565 it has previously reported those events to @value{GDBN}. The first
39566 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39567 subsequent stop replies are sent as responses to @samp{vStopped} packets
39568 using the mechanism described above. The target must not send
39569 asynchronous stop reply notifications until the sequence is complete.
39570 If all threads are running when the target receives the @samp{?} packet,
39571 or if the target is not attached to any process, it shall respond
39574 If the stub supports non-stop mode, it should also support the
39575 @samp{swbreak} stop reason if software breakpoints are supported, and
39576 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39577 (@pxref{swbreak stop reason}). This is because given the asynchronous
39578 nature of non-stop mode, between the time a thread hits a breakpoint
39579 and the time the event is finally processed by @value{GDBN}, the
39580 breakpoint may have already been removed from the target. Due to
39581 this, @value{GDBN} needs to be able to tell whether a trap stop was
39582 caused by a delayed breakpoint event, which should be ignored, as
39583 opposed to a random trap signal, which should be reported to the user.
39584 Note the @samp{swbreak} feature implies that the target is responsible
39585 for adjusting the PC when a software breakpoint triggers, if
39586 necessary, such as on the x86 architecture.
39588 @node Packet Acknowledgment
39589 @section Packet Acknowledgment
39591 @cindex acknowledgment, for @value{GDBN} remote
39592 @cindex packet acknowledgment, for @value{GDBN} remote
39593 By default, when either the host or the target machine receives a packet,
39594 the first response expected is an acknowledgment: either @samp{+} (to indicate
39595 the package was received correctly) or @samp{-} (to request retransmission).
39596 This mechanism allows the @value{GDBN} remote protocol to operate over
39597 unreliable transport mechanisms, such as a serial line.
39599 In cases where the transport mechanism is itself reliable (such as a pipe or
39600 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39601 It may be desirable to disable them in that case to reduce communication
39602 overhead, or for other reasons. This can be accomplished by means of the
39603 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39605 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39606 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39607 and response format still includes the normal checksum, as described in
39608 @ref{Overview}, but the checksum may be ignored by the receiver.
39610 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39611 no-acknowledgment mode, it should report that to @value{GDBN}
39612 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39613 @pxref{qSupported}.
39614 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39615 disabled via the @code{set remote noack-packet off} command
39616 (@pxref{Remote Configuration}),
39617 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39618 Only then may the stub actually turn off packet acknowledgments.
39619 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39620 response, which can be safely ignored by the stub.
39622 Note that @code{set remote noack-packet} command only affects negotiation
39623 between @value{GDBN} and the stub when subsequent connections are made;
39624 it does not affect the protocol acknowledgment state for any current
39626 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39627 new connection is established,
39628 there is also no protocol request to re-enable the acknowledgments
39629 for the current connection, once disabled.
39634 Example sequence of a target being re-started. Notice how the restart
39635 does not get any direct output:
39640 @emph{target restarts}
39643 <- @code{T001:1234123412341234}
39647 Example sequence of a target being stepped by a single instruction:
39650 -> @code{G1445@dots{}}
39655 <- @code{T001:1234123412341234}
39659 <- @code{1455@dots{}}
39663 @node File-I/O Remote Protocol Extension
39664 @section File-I/O Remote Protocol Extension
39665 @cindex File-I/O remote protocol extension
39668 * File-I/O Overview::
39669 * Protocol Basics::
39670 * The F Request Packet::
39671 * The F Reply Packet::
39672 * The Ctrl-C Message::
39674 * List of Supported Calls::
39675 * Protocol-specific Representation of Datatypes::
39677 * File-I/O Examples::
39680 @node File-I/O Overview
39681 @subsection File-I/O Overview
39682 @cindex file-i/o overview
39684 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39685 target to use the host's file system and console I/O to perform various
39686 system calls. System calls on the target system are translated into a
39687 remote protocol packet to the host system, which then performs the needed
39688 actions and returns a response packet to the target system.
39689 This simulates file system operations even on targets that lack file systems.
39691 The protocol is defined to be independent of both the host and target systems.
39692 It uses its own internal representation of datatypes and values. Both
39693 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39694 translating the system-dependent value representations into the internal
39695 protocol representations when data is transmitted.
39697 The communication is synchronous. A system call is possible only when
39698 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39699 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39700 the target is stopped to allow deterministic access to the target's
39701 memory. Therefore File-I/O is not interruptible by target signals. On
39702 the other hand, it is possible to interrupt File-I/O by a user interrupt
39703 (@samp{Ctrl-C}) within @value{GDBN}.
39705 The target's request to perform a host system call does not finish
39706 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39707 after finishing the system call, the target returns to continuing the
39708 previous activity (continue, step). No additional continue or step
39709 request from @value{GDBN} is required.
39712 (@value{GDBP}) continue
39713 <- target requests 'system call X'
39714 target is stopped, @value{GDBN} executes system call
39715 -> @value{GDBN} returns result
39716 ... target continues, @value{GDBN} returns to wait for the target
39717 <- target hits breakpoint and sends a Txx packet
39720 The protocol only supports I/O on the console and to regular files on
39721 the host file system. Character or block special devices, pipes,
39722 named pipes, sockets or any other communication method on the host
39723 system are not supported by this protocol.
39725 File I/O is not supported in non-stop mode.
39727 @node Protocol Basics
39728 @subsection Protocol Basics
39729 @cindex protocol basics, file-i/o
39731 The File-I/O protocol uses the @code{F} packet as the request as well
39732 as reply packet. Since a File-I/O system call can only occur when
39733 @value{GDBN} is waiting for a response from the continuing or stepping target,
39734 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39735 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39736 This @code{F} packet contains all information needed to allow @value{GDBN}
39737 to call the appropriate host system call:
39741 A unique identifier for the requested system call.
39744 All parameters to the system call. Pointers are given as addresses
39745 in the target memory address space. Pointers to strings are given as
39746 pointer/length pair. Numerical values are given as they are.
39747 Numerical control flags are given in a protocol-specific representation.
39751 At this point, @value{GDBN} has to perform the following actions.
39755 If the parameters include pointer values to data needed as input to a
39756 system call, @value{GDBN} requests this data from the target with a
39757 standard @code{m} packet request. This additional communication has to be
39758 expected by the target implementation and is handled as any other @code{m}
39762 @value{GDBN} translates all value from protocol representation to host
39763 representation as needed. Datatypes are coerced into the host types.
39766 @value{GDBN} calls the system call.
39769 It then coerces datatypes back to protocol representation.
39772 If the system call is expected to return data in buffer space specified
39773 by pointer parameters to the call, the data is transmitted to the
39774 target using a @code{M} or @code{X} packet. This packet has to be expected
39775 by the target implementation and is handled as any other @code{M} or @code{X}
39780 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39781 necessary information for the target to continue. This at least contains
39788 @code{errno}, if has been changed by the system call.
39795 After having done the needed type and value coercion, the target continues
39796 the latest continue or step action.
39798 @node The F Request Packet
39799 @subsection The @code{F} Request Packet
39800 @cindex file-i/o request packet
39801 @cindex @code{F} request packet
39803 The @code{F} request packet has the following format:
39806 @item F@var{call-id},@var{parameter@dots{}}
39808 @var{call-id} is the identifier to indicate the host system call to be called.
39809 This is just the name of the function.
39811 @var{parameter@dots{}} are the parameters to the system call.
39812 Parameters are hexadecimal integer values, either the actual values in case
39813 of scalar datatypes, pointers to target buffer space in case of compound
39814 datatypes and unspecified memory areas, or pointer/length pairs in case
39815 of string parameters. These are appended to the @var{call-id} as a
39816 comma-delimited list. All values are transmitted in ASCII
39817 string representation, pointer/length pairs separated by a slash.
39823 @node The F Reply Packet
39824 @subsection The @code{F} Reply Packet
39825 @cindex file-i/o reply packet
39826 @cindex @code{F} reply packet
39828 The @code{F} reply packet has the following format:
39832 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39834 @var{retcode} is the return code of the system call as hexadecimal value.
39836 @var{errno} is the @code{errno} set by the call, in protocol-specific
39838 This parameter can be omitted if the call was successful.
39840 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39841 case, @var{errno} must be sent as well, even if the call was successful.
39842 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39849 or, if the call was interrupted before the host call has been performed:
39856 assuming 4 is the protocol-specific representation of @code{EINTR}.
39861 @node The Ctrl-C Message
39862 @subsection The @samp{Ctrl-C} Message
39863 @cindex ctrl-c message, in file-i/o protocol
39865 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39866 reply packet (@pxref{The F Reply Packet}),
39867 the target should behave as if it had
39868 gotten a break message. The meaning for the target is ``system call
39869 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39870 (as with a break message) and return to @value{GDBN} with a @code{T02}
39873 It's important for the target to know in which
39874 state the system call was interrupted. There are two possible cases:
39878 The system call hasn't been performed on the host yet.
39881 The system call on the host has been finished.
39885 These two states can be distinguished by the target by the value of the
39886 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39887 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39888 on POSIX systems. In any other case, the target may presume that the
39889 system call has been finished --- successfully or not --- and should behave
39890 as if the break message arrived right after the system call.
39892 @value{GDBN} must behave reliably. If the system call has not been called
39893 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39894 @code{errno} in the packet. If the system call on the host has been finished
39895 before the user requests a break, the full action must be finished by
39896 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39897 The @code{F} packet may only be sent when either nothing has happened
39898 or the full action has been completed.
39901 @subsection Console I/O
39902 @cindex console i/o as part of file-i/o
39904 By default and if not explicitly closed by the target system, the file
39905 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39906 on the @value{GDBN} console is handled as any other file output operation
39907 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39908 by @value{GDBN} so that after the target read request from file descriptor
39909 0 all following typing is buffered until either one of the following
39914 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39916 system call is treated as finished.
39919 The user presses @key{RET}. This is treated as end of input with a trailing
39923 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39924 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39928 If the user has typed more characters than fit in the buffer given to
39929 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39930 either another @code{read(0, @dots{})} is requested by the target, or debugging
39931 is stopped at the user's request.
39934 @node List of Supported Calls
39935 @subsection List of Supported Calls
39936 @cindex list of supported file-i/o calls
39953 @unnumberedsubsubsec open
39954 @cindex open, file-i/o system call
39959 int open(const char *pathname, int flags);
39960 int open(const char *pathname, int flags, mode_t mode);
39964 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39967 @var{flags} is the bitwise @code{OR} of the following values:
39971 If the file does not exist it will be created. The host
39972 rules apply as far as file ownership and time stamps
39976 When used with @code{O_CREAT}, if the file already exists it is
39977 an error and open() fails.
39980 If the file already exists and the open mode allows
39981 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39982 truncated to zero length.
39985 The file is opened in append mode.
39988 The file is opened for reading only.
39991 The file is opened for writing only.
39994 The file is opened for reading and writing.
39998 Other bits are silently ignored.
40002 @var{mode} is the bitwise @code{OR} of the following values:
40006 User has read permission.
40009 User has write permission.
40012 Group has read permission.
40015 Group has write permission.
40018 Others have read permission.
40021 Others have write permission.
40025 Other bits are silently ignored.
40028 @item Return value:
40029 @code{open} returns the new file descriptor or -1 if an error
40036 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40039 @var{pathname} refers to a directory.
40042 The requested access is not allowed.
40045 @var{pathname} was too long.
40048 A directory component in @var{pathname} does not exist.
40051 @var{pathname} refers to a device, pipe, named pipe or socket.
40054 @var{pathname} refers to a file on a read-only filesystem and
40055 write access was requested.
40058 @var{pathname} is an invalid pointer value.
40061 No space on device to create the file.
40064 The process already has the maximum number of files open.
40067 The limit on the total number of files open on the system
40071 The call was interrupted by the user.
40077 @unnumberedsubsubsec close
40078 @cindex close, file-i/o system call
40087 @samp{Fclose,@var{fd}}
40089 @item Return value:
40090 @code{close} returns zero on success, or -1 if an error occurred.
40096 @var{fd} isn't a valid open file descriptor.
40099 The call was interrupted by the user.
40105 @unnumberedsubsubsec read
40106 @cindex read, file-i/o system call
40111 int read(int fd, void *buf, unsigned int count);
40115 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40117 @item Return value:
40118 On success, the number of bytes read is returned.
40119 Zero indicates end of file. If count is zero, read
40120 returns zero as well. On error, -1 is returned.
40126 @var{fd} is not a valid file descriptor or is not open for
40130 @var{bufptr} is an invalid pointer value.
40133 The call was interrupted by the user.
40139 @unnumberedsubsubsec write
40140 @cindex write, file-i/o system call
40145 int write(int fd, const void *buf, unsigned int count);
40149 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40151 @item Return value:
40152 On success, the number of bytes written are returned.
40153 Zero indicates nothing was written. On error, -1
40160 @var{fd} is not a valid file descriptor or is not open for
40164 @var{bufptr} is an invalid pointer value.
40167 An attempt was made to write a file that exceeds the
40168 host-specific maximum file size allowed.
40171 No space on device to write the data.
40174 The call was interrupted by the user.
40180 @unnumberedsubsubsec lseek
40181 @cindex lseek, file-i/o system call
40186 long lseek (int fd, long offset, int flag);
40190 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40192 @var{flag} is one of:
40196 The offset is set to @var{offset} bytes.
40199 The offset is set to its current location plus @var{offset}
40203 The offset is set to the size of the file plus @var{offset}
40207 @item Return value:
40208 On success, the resulting unsigned offset in bytes from
40209 the beginning of the file is returned. Otherwise, a
40210 value of -1 is returned.
40216 @var{fd} is not a valid open file descriptor.
40219 @var{fd} is associated with the @value{GDBN} console.
40222 @var{flag} is not a proper value.
40225 The call was interrupted by the user.
40231 @unnumberedsubsubsec rename
40232 @cindex rename, file-i/o system call
40237 int rename(const char *oldpath, const char *newpath);
40241 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40243 @item Return value:
40244 On success, zero is returned. On error, -1 is returned.
40250 @var{newpath} is an existing directory, but @var{oldpath} is not a
40254 @var{newpath} is a non-empty directory.
40257 @var{oldpath} or @var{newpath} is a directory that is in use by some
40261 An attempt was made to make a directory a subdirectory
40265 A component used as a directory in @var{oldpath} or new
40266 path is not a directory. Or @var{oldpath} is a directory
40267 and @var{newpath} exists but is not a directory.
40270 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40273 No access to the file or the path of the file.
40277 @var{oldpath} or @var{newpath} was too long.
40280 A directory component in @var{oldpath} or @var{newpath} does not exist.
40283 The file is on a read-only filesystem.
40286 The device containing the file has no room for the new
40290 The call was interrupted by the user.
40296 @unnumberedsubsubsec unlink
40297 @cindex unlink, file-i/o system call
40302 int unlink(const char *pathname);
40306 @samp{Funlink,@var{pathnameptr}/@var{len}}
40308 @item Return value:
40309 On success, zero is returned. On error, -1 is returned.
40315 No access to the file or the path of the file.
40318 The system does not allow unlinking of directories.
40321 The file @var{pathname} cannot be unlinked because it's
40322 being used by another process.
40325 @var{pathnameptr} is an invalid pointer value.
40328 @var{pathname} was too long.
40331 A directory component in @var{pathname} does not exist.
40334 A component of the path is not a directory.
40337 The file is on a read-only filesystem.
40340 The call was interrupted by the user.
40346 @unnumberedsubsubsec stat/fstat
40347 @cindex fstat, file-i/o system call
40348 @cindex stat, file-i/o system call
40353 int stat(const char *pathname, struct stat *buf);
40354 int fstat(int fd, struct stat *buf);
40358 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40359 @samp{Ffstat,@var{fd},@var{bufptr}}
40361 @item Return value:
40362 On success, zero is returned. On error, -1 is returned.
40368 @var{fd} is not a valid open file.
40371 A directory component in @var{pathname} does not exist or the
40372 path is an empty string.
40375 A component of the path is not a directory.
40378 @var{pathnameptr} is an invalid pointer value.
40381 No access to the file or the path of the file.
40384 @var{pathname} was too long.
40387 The call was interrupted by the user.
40393 @unnumberedsubsubsec gettimeofday
40394 @cindex gettimeofday, file-i/o system call
40399 int gettimeofday(struct timeval *tv, void *tz);
40403 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40405 @item Return value:
40406 On success, 0 is returned, -1 otherwise.
40412 @var{tz} is a non-NULL pointer.
40415 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40421 @unnumberedsubsubsec isatty
40422 @cindex isatty, file-i/o system call
40427 int isatty(int fd);
40431 @samp{Fisatty,@var{fd}}
40433 @item Return value:
40434 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40440 The call was interrupted by the user.
40445 Note that the @code{isatty} call is treated as a special case: it returns
40446 1 to the target if the file descriptor is attached
40447 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40448 would require implementing @code{ioctl} and would be more complex than
40453 @unnumberedsubsubsec system
40454 @cindex system, file-i/o system call
40459 int system(const char *command);
40463 @samp{Fsystem,@var{commandptr}/@var{len}}
40465 @item Return value:
40466 If @var{len} is zero, the return value indicates whether a shell is
40467 available. A zero return value indicates a shell is not available.
40468 For non-zero @var{len}, the value returned is -1 on error and the
40469 return status of the command otherwise. Only the exit status of the
40470 command is returned, which is extracted from the host's @code{system}
40471 return value by calling @code{WEXITSTATUS(retval)}. In case
40472 @file{/bin/sh} could not be executed, 127 is returned.
40478 The call was interrupted by the user.
40483 @value{GDBN} takes over the full task of calling the necessary host calls
40484 to perform the @code{system} call. The return value of @code{system} on
40485 the host is simplified before it's returned
40486 to the target. Any termination signal information from the child process
40487 is discarded, and the return value consists
40488 entirely of the exit status of the called command.
40490 Due to security concerns, the @code{system} call is by default refused
40491 by @value{GDBN}. The user has to allow this call explicitly with the
40492 @code{set remote system-call-allowed 1} command.
40495 @item set remote system-call-allowed
40496 @kindex set remote system-call-allowed
40497 Control whether to allow the @code{system} calls in the File I/O
40498 protocol for the remote target. The default is zero (disabled).
40500 @item show remote system-call-allowed
40501 @kindex show remote system-call-allowed
40502 Show whether the @code{system} calls are allowed in the File I/O
40506 @node Protocol-specific Representation of Datatypes
40507 @subsection Protocol-specific Representation of Datatypes
40508 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40511 * Integral Datatypes::
40513 * Memory Transfer::
40518 @node Integral Datatypes
40519 @unnumberedsubsubsec Integral Datatypes
40520 @cindex integral datatypes, in file-i/o protocol
40522 The integral datatypes used in the system calls are @code{int},
40523 @code{unsigned int}, @code{long}, @code{unsigned long},
40524 @code{mode_t}, and @code{time_t}.
40526 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40527 implemented as 32 bit values in this protocol.
40529 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40531 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40532 in @file{limits.h}) to allow range checking on host and target.
40534 @code{time_t} datatypes are defined as seconds since the Epoch.
40536 All integral datatypes transferred as part of a memory read or write of a
40537 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40540 @node Pointer Values
40541 @unnumberedsubsubsec Pointer Values
40542 @cindex pointer values, in file-i/o protocol
40544 Pointers to target data are transmitted as they are. An exception
40545 is made for pointers to buffers for which the length isn't
40546 transmitted as part of the function call, namely strings. Strings
40547 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40554 which is a pointer to data of length 18 bytes at position 0x1aaf.
40555 The length is defined as the full string length in bytes, including
40556 the trailing null byte. For example, the string @code{"hello world"}
40557 at address 0x123456 is transmitted as
40563 @node Memory Transfer
40564 @unnumberedsubsubsec Memory Transfer
40565 @cindex memory transfer, in file-i/o protocol
40567 Structured data which is transferred using a memory read or write (for
40568 example, a @code{struct stat}) is expected to be in a protocol-specific format
40569 with all scalar multibyte datatypes being big endian. Translation to
40570 this representation needs to be done both by the target before the @code{F}
40571 packet is sent, and by @value{GDBN} before
40572 it transfers memory to the target. Transferred pointers to structured
40573 data should point to the already-coerced data at any time.
40577 @unnumberedsubsubsec struct stat
40578 @cindex struct stat, in file-i/o protocol
40580 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40581 is defined as follows:
40585 unsigned int st_dev; /* device */
40586 unsigned int st_ino; /* inode */
40587 mode_t st_mode; /* protection */
40588 unsigned int st_nlink; /* number of hard links */
40589 unsigned int st_uid; /* user ID of owner */
40590 unsigned int st_gid; /* group ID of owner */
40591 unsigned int st_rdev; /* device type (if inode device) */
40592 unsigned long st_size; /* total size, in bytes */
40593 unsigned long st_blksize; /* blocksize for filesystem I/O */
40594 unsigned long st_blocks; /* number of blocks allocated */
40595 time_t st_atime; /* time of last access */
40596 time_t st_mtime; /* time of last modification */
40597 time_t st_ctime; /* time of last change */
40601 The integral datatypes conform to the definitions given in the
40602 appropriate section (see @ref{Integral Datatypes}, for details) so this
40603 structure is of size 64 bytes.
40605 The values of several fields have a restricted meaning and/or
40611 A value of 0 represents a file, 1 the console.
40614 No valid meaning for the target. Transmitted unchanged.
40617 Valid mode bits are described in @ref{Constants}. Any other
40618 bits have currently no meaning for the target.
40623 No valid meaning for the target. Transmitted unchanged.
40628 These values have a host and file system dependent
40629 accuracy. Especially on Windows hosts, the file system may not
40630 support exact timing values.
40633 The target gets a @code{struct stat} of the above representation and is
40634 responsible for coercing it to the target representation before
40637 Note that due to size differences between the host, target, and protocol
40638 representations of @code{struct stat} members, these members could eventually
40639 get truncated on the target.
40641 @node struct timeval
40642 @unnumberedsubsubsec struct timeval
40643 @cindex struct timeval, in file-i/o protocol
40645 The buffer of type @code{struct timeval} used by the File-I/O protocol
40646 is defined as follows:
40650 time_t tv_sec; /* second */
40651 long tv_usec; /* microsecond */
40655 The integral datatypes conform to the definitions given in the
40656 appropriate section (see @ref{Integral Datatypes}, for details) so this
40657 structure is of size 8 bytes.
40660 @subsection Constants
40661 @cindex constants, in file-i/o protocol
40663 The following values are used for the constants inside of the
40664 protocol. @value{GDBN} and target are responsible for translating these
40665 values before and after the call as needed.
40676 @unnumberedsubsubsec Open Flags
40677 @cindex open flags, in file-i/o protocol
40679 All values are given in hexadecimal representation.
40691 @node mode_t Values
40692 @unnumberedsubsubsec mode_t Values
40693 @cindex mode_t values, in file-i/o protocol
40695 All values are given in octal representation.
40712 @unnumberedsubsubsec Errno Values
40713 @cindex errno values, in file-i/o protocol
40715 All values are given in decimal representation.
40740 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40741 any error value not in the list of supported error numbers.
40744 @unnumberedsubsubsec Lseek Flags
40745 @cindex lseek flags, in file-i/o protocol
40754 @unnumberedsubsubsec Limits
40755 @cindex limits, in file-i/o protocol
40757 All values are given in decimal representation.
40760 INT_MIN -2147483648
40762 UINT_MAX 4294967295
40763 LONG_MIN -9223372036854775808
40764 LONG_MAX 9223372036854775807
40765 ULONG_MAX 18446744073709551615
40768 @node File-I/O Examples
40769 @subsection File-I/O Examples
40770 @cindex file-i/o examples
40772 Example sequence of a write call, file descriptor 3, buffer is at target
40773 address 0x1234, 6 bytes should be written:
40776 <- @code{Fwrite,3,1234,6}
40777 @emph{request memory read from target}
40780 @emph{return "6 bytes written"}
40784 Example sequence of a read call, file descriptor 3, buffer is at target
40785 address 0x1234, 6 bytes should be read:
40788 <- @code{Fread,3,1234,6}
40789 @emph{request memory write to target}
40790 -> @code{X1234,6:XXXXXX}
40791 @emph{return "6 bytes read"}
40795 Example sequence of a read call, call fails on the host due to invalid
40796 file descriptor (@code{EBADF}):
40799 <- @code{Fread,3,1234,6}
40803 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40807 <- @code{Fread,3,1234,6}
40812 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40816 <- @code{Fread,3,1234,6}
40817 -> @code{X1234,6:XXXXXX}
40821 @node Library List Format
40822 @section Library List Format
40823 @cindex library list format, remote protocol
40825 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40826 same process as your application to manage libraries. In this case,
40827 @value{GDBN} can use the loader's symbol table and normal memory
40828 operations to maintain a list of shared libraries. On other
40829 platforms, the operating system manages loaded libraries.
40830 @value{GDBN} can not retrieve the list of currently loaded libraries
40831 through memory operations, so it uses the @samp{qXfer:libraries:read}
40832 packet (@pxref{qXfer library list read}) instead. The remote stub
40833 queries the target's operating system and reports which libraries
40836 The @samp{qXfer:libraries:read} packet returns an XML document which
40837 lists loaded libraries and their offsets. Each library has an
40838 associated name and one or more segment or section base addresses,
40839 which report where the library was loaded in memory.
40841 For the common case of libraries that are fully linked binaries, the
40842 library should have a list of segments. If the target supports
40843 dynamic linking of a relocatable object file, its library XML element
40844 should instead include a list of allocated sections. The segment or
40845 section bases are start addresses, not relocation offsets; they do not
40846 depend on the library's link-time base addresses.
40848 @value{GDBN} must be linked with the Expat library to support XML
40849 library lists. @xref{Expat}.
40851 A simple memory map, with one loaded library relocated by a single
40852 offset, looks like this:
40856 <library name="/lib/libc.so.6">
40857 <segment address="0x10000000"/>
40862 Another simple memory map, with one loaded library with three
40863 allocated sections (.text, .data, .bss), looks like this:
40867 <library name="sharedlib.o">
40868 <section address="0x10000000"/>
40869 <section address="0x20000000"/>
40870 <section address="0x30000000"/>
40875 The format of a library list is described by this DTD:
40878 <!-- library-list: Root element with versioning -->
40879 <!ELEMENT library-list (library)*>
40880 <!ATTLIST library-list version CDATA #FIXED "1.0">
40881 <!ELEMENT library (segment*, section*)>
40882 <!ATTLIST library name CDATA #REQUIRED>
40883 <!ELEMENT segment EMPTY>
40884 <!ATTLIST segment address CDATA #REQUIRED>
40885 <!ELEMENT section EMPTY>
40886 <!ATTLIST section address CDATA #REQUIRED>
40889 In addition, segments and section descriptors cannot be mixed within a
40890 single library element, and you must supply at least one segment or
40891 section for each library.
40893 @node Library List Format for SVR4 Targets
40894 @section Library List Format for SVR4 Targets
40895 @cindex library list format, remote protocol
40897 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40898 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40899 shared libraries. Still a special library list provided by this packet is
40900 more efficient for the @value{GDBN} remote protocol.
40902 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40903 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40904 target, the following parameters are reported:
40908 @code{name}, the absolute file name from the @code{l_name} field of
40909 @code{struct link_map}.
40911 @code{lm} with address of @code{struct link_map} used for TLS
40912 (Thread Local Storage) access.
40914 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40915 @code{struct link_map}. For prelinked libraries this is not an absolute
40916 memory address. It is a displacement of absolute memory address against
40917 address the file was prelinked to during the library load.
40919 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40922 Additionally the single @code{main-lm} attribute specifies address of
40923 @code{struct link_map} used for the main executable. This parameter is used
40924 for TLS access and its presence is optional.
40926 @value{GDBN} must be linked with the Expat library to support XML
40927 SVR4 library lists. @xref{Expat}.
40929 A simple memory map, with two loaded libraries (which do not use prelink),
40933 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40934 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40936 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40938 </library-list-svr>
40941 The format of an SVR4 library list is described by this DTD:
40944 <!-- library-list-svr4: Root element with versioning -->
40945 <!ELEMENT library-list-svr4 (library)*>
40946 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40947 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40948 <!ELEMENT library EMPTY>
40949 <!ATTLIST library name CDATA #REQUIRED>
40950 <!ATTLIST library lm CDATA #REQUIRED>
40951 <!ATTLIST library l_addr CDATA #REQUIRED>
40952 <!ATTLIST library l_ld CDATA #REQUIRED>
40955 @node Memory Map Format
40956 @section Memory Map Format
40957 @cindex memory map format
40959 To be able to write into flash memory, @value{GDBN} needs to obtain a
40960 memory map from the target. This section describes the format of the
40963 The memory map is obtained using the @samp{qXfer:memory-map:read}
40964 (@pxref{qXfer memory map read}) packet and is an XML document that
40965 lists memory regions.
40967 @value{GDBN} must be linked with the Expat library to support XML
40968 memory maps. @xref{Expat}.
40970 The top-level structure of the document is shown below:
40973 <?xml version="1.0"?>
40974 <!DOCTYPE memory-map
40975 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40976 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40982 Each region can be either:
40987 A region of RAM starting at @var{addr} and extending for @var{length}
40991 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40996 A region of read-only memory:
40999 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41004 A region of flash memory, with erasure blocks @var{blocksize}
41008 <memory type="flash" start="@var{addr}" length="@var{length}">
41009 <property name="blocksize">@var{blocksize}</property>
41015 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41016 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41017 packets to write to addresses in such ranges.
41019 The formal DTD for memory map format is given below:
41022 <!-- ................................................... -->
41023 <!-- Memory Map XML DTD ................................ -->
41024 <!-- File: memory-map.dtd .............................. -->
41025 <!-- .................................... .............. -->
41026 <!-- memory-map.dtd -->
41027 <!-- memory-map: Root element with versioning -->
41028 <!ELEMENT memory-map (memory)*>
41029 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41030 <!ELEMENT memory (property)*>
41031 <!-- memory: Specifies a memory region,
41032 and its type, or device. -->
41033 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41034 start CDATA #REQUIRED
41035 length CDATA #REQUIRED>
41036 <!-- property: Generic attribute tag -->
41037 <!ELEMENT property (#PCDATA | property)*>
41038 <!ATTLIST property name (blocksize) #REQUIRED>
41041 @node Thread List Format
41042 @section Thread List Format
41043 @cindex thread list format
41045 To efficiently update the list of threads and their attributes,
41046 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41047 (@pxref{qXfer threads read}) and obtains the XML document with
41048 the following structure:
41051 <?xml version="1.0"?>
41053 <thread id="id" core="0" name="name">
41054 ... description ...
41059 Each @samp{thread} element must have the @samp{id} attribute that
41060 identifies the thread (@pxref{thread-id syntax}). The
41061 @samp{core} attribute, if present, specifies which processor core
41062 the thread was last executing on. The @samp{name} attribute, if
41063 present, specifies the human-readable name of the thread. The content
41064 of the of @samp{thread} element is interpreted as human-readable
41065 auxiliary information. The @samp{handle} attribute, if present,
41066 is a hex encoded representation of the thread handle.
41069 @node Traceframe Info Format
41070 @section Traceframe Info Format
41071 @cindex traceframe info format
41073 To be able to know which objects in the inferior can be examined when
41074 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41075 memory ranges, registers and trace state variables that have been
41076 collected in a traceframe.
41078 This list is obtained using the @samp{qXfer:traceframe-info:read}
41079 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41081 @value{GDBN} must be linked with the Expat library to support XML
41082 traceframe info discovery. @xref{Expat}.
41084 The top-level structure of the document is shown below:
41087 <?xml version="1.0"?>
41088 <!DOCTYPE traceframe-info
41089 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41090 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41096 Each traceframe block can be either:
41101 A region of collected memory starting at @var{addr} and extending for
41102 @var{length} bytes from there:
41105 <memory start="@var{addr}" length="@var{length}"/>
41109 A block indicating trace state variable numbered @var{number} has been
41113 <tvar id="@var{number}"/>
41118 The formal DTD for the traceframe info format is given below:
41121 <!ELEMENT traceframe-info (memory | tvar)* >
41122 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41124 <!ELEMENT memory EMPTY>
41125 <!ATTLIST memory start CDATA #REQUIRED
41126 length CDATA #REQUIRED>
41128 <!ATTLIST tvar id CDATA #REQUIRED>
41131 @node Branch Trace Format
41132 @section Branch Trace Format
41133 @cindex branch trace format
41135 In order to display the branch trace of an inferior thread,
41136 @value{GDBN} needs to obtain the list of branches. This list is
41137 represented as list of sequential code blocks that are connected via
41138 branches. The code in each block has been executed sequentially.
41140 This list is obtained using the @samp{qXfer:btrace:read}
41141 (@pxref{qXfer btrace read}) packet and is an XML document.
41143 @value{GDBN} must be linked with the Expat library to support XML
41144 traceframe info discovery. @xref{Expat}.
41146 The top-level structure of the document is shown below:
41149 <?xml version="1.0"?>
41151 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41152 "http://sourceware.org/gdb/gdb-btrace.dtd">
41161 A block of sequentially executed instructions starting at @var{begin}
41162 and ending at @var{end}:
41165 <block begin="@var{begin}" end="@var{end}"/>
41170 The formal DTD for the branch trace format is given below:
41173 <!ELEMENT btrace (block* | pt) >
41174 <!ATTLIST btrace version CDATA #FIXED "1.0">
41176 <!ELEMENT block EMPTY>
41177 <!ATTLIST block begin CDATA #REQUIRED
41178 end CDATA #REQUIRED>
41180 <!ELEMENT pt (pt-config?, raw?)>
41182 <!ELEMENT pt-config (cpu?)>
41184 <!ELEMENT cpu EMPTY>
41185 <!ATTLIST cpu vendor CDATA #REQUIRED
41186 family CDATA #REQUIRED
41187 model CDATA #REQUIRED
41188 stepping CDATA #REQUIRED>
41190 <!ELEMENT raw (#PCDATA)>
41193 @node Branch Trace Configuration Format
41194 @section Branch Trace Configuration Format
41195 @cindex branch trace configuration format
41197 For each inferior thread, @value{GDBN} can obtain the branch trace
41198 configuration using the @samp{qXfer:btrace-conf:read}
41199 (@pxref{qXfer btrace-conf read}) packet.
41201 The configuration describes the branch trace format and configuration
41202 settings for that format. The following information is described:
41206 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41209 The size of the @acronym{BTS} ring buffer in bytes.
41212 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41216 The size of the @acronym{Intel PT} ring buffer in bytes.
41220 @value{GDBN} must be linked with the Expat library to support XML
41221 branch trace configuration discovery. @xref{Expat}.
41223 The formal DTD for the branch trace configuration format is given below:
41226 <!ELEMENT btrace-conf (bts?, pt?)>
41227 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41229 <!ELEMENT bts EMPTY>
41230 <!ATTLIST bts size CDATA #IMPLIED>
41232 <!ELEMENT pt EMPTY>
41233 <!ATTLIST pt size CDATA #IMPLIED>
41236 @include agentexpr.texi
41238 @node Target Descriptions
41239 @appendix Target Descriptions
41240 @cindex target descriptions
41242 One of the challenges of using @value{GDBN} to debug embedded systems
41243 is that there are so many minor variants of each processor
41244 architecture in use. It is common practice for vendors to start with
41245 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41246 and then make changes to adapt it to a particular market niche. Some
41247 architectures have hundreds of variants, available from dozens of
41248 vendors. This leads to a number of problems:
41252 With so many different customized processors, it is difficult for
41253 the @value{GDBN} maintainers to keep up with the changes.
41255 Since individual variants may have short lifetimes or limited
41256 audiences, it may not be worthwhile to carry information about every
41257 variant in the @value{GDBN} source tree.
41259 When @value{GDBN} does support the architecture of the embedded system
41260 at hand, the task of finding the correct architecture name to give the
41261 @command{set architecture} command can be error-prone.
41264 To address these problems, the @value{GDBN} remote protocol allows a
41265 target system to not only identify itself to @value{GDBN}, but to
41266 actually describe its own features. This lets @value{GDBN} support
41267 processor variants it has never seen before --- to the extent that the
41268 descriptions are accurate, and that @value{GDBN} understands them.
41270 @value{GDBN} must be linked with the Expat library to support XML
41271 target descriptions. @xref{Expat}.
41274 * Retrieving Descriptions:: How descriptions are fetched from a target.
41275 * Target Description Format:: The contents of a target description.
41276 * Predefined Target Types:: Standard types available for target
41278 * Enum Target Types:: How to define enum target types.
41279 * Standard Target Features:: Features @value{GDBN} knows about.
41282 @node Retrieving Descriptions
41283 @section Retrieving Descriptions
41285 Target descriptions can be read from the target automatically, or
41286 specified by the user manually. The default behavior is to read the
41287 description from the target. @value{GDBN} retrieves it via the remote
41288 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41289 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41290 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41291 XML document, of the form described in @ref{Target Description
41294 Alternatively, you can specify a file to read for the target description.
41295 If a file is set, the target will not be queried. The commands to
41296 specify a file are:
41299 @cindex set tdesc filename
41300 @item set tdesc filename @var{path}
41301 Read the target description from @var{path}.
41303 @cindex unset tdesc filename
41304 @item unset tdesc filename
41305 Do not read the XML target description from a file. @value{GDBN}
41306 will use the description supplied by the current target.
41308 @cindex show tdesc filename
41309 @item show tdesc filename
41310 Show the filename to read for a target description, if any.
41314 @node Target Description Format
41315 @section Target Description Format
41316 @cindex target descriptions, XML format
41318 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41319 document which complies with the Document Type Definition provided in
41320 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41321 means you can use generally available tools like @command{xmllint} to
41322 check that your feature descriptions are well-formed and valid.
41323 However, to help people unfamiliar with XML write descriptions for
41324 their targets, we also describe the grammar here.
41326 Target descriptions can identify the architecture of the remote target
41327 and (for some architectures) provide information about custom register
41328 sets. They can also identify the OS ABI of the remote target.
41329 @value{GDBN} can use this information to autoconfigure for your
41330 target, or to warn you if you connect to an unsupported target.
41332 Here is a simple target description:
41335 <target version="1.0">
41336 <architecture>i386:x86-64</architecture>
41341 This minimal description only says that the target uses
41342 the x86-64 architecture.
41344 A target description has the following overall form, with [ ] marking
41345 optional elements and @dots{} marking repeatable elements. The elements
41346 are explained further below.
41349 <?xml version="1.0"?>
41350 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41351 <target version="1.0">
41352 @r{[}@var{architecture}@r{]}
41353 @r{[}@var{osabi}@r{]}
41354 @r{[}@var{compatible}@r{]}
41355 @r{[}@var{feature}@dots{}@r{]}
41360 The description is generally insensitive to whitespace and line
41361 breaks, under the usual common-sense rules. The XML version
41362 declaration and document type declaration can generally be omitted
41363 (@value{GDBN} does not require them), but specifying them may be
41364 useful for XML validation tools. The @samp{version} attribute for
41365 @samp{<target>} may also be omitted, but we recommend
41366 including it; if future versions of @value{GDBN} use an incompatible
41367 revision of @file{gdb-target.dtd}, they will detect and report
41368 the version mismatch.
41370 @subsection Inclusion
41371 @cindex target descriptions, inclusion
41374 @cindex <xi:include>
41377 It can sometimes be valuable to split a target description up into
41378 several different annexes, either for organizational purposes, or to
41379 share files between different possible target descriptions. You can
41380 divide a description into multiple files by replacing any element of
41381 the target description with an inclusion directive of the form:
41384 <xi:include href="@var{document}"/>
41388 When @value{GDBN} encounters an element of this form, it will retrieve
41389 the named XML @var{document}, and replace the inclusion directive with
41390 the contents of that document. If the current description was read
41391 using @samp{qXfer}, then so will be the included document;
41392 @var{document} will be interpreted as the name of an annex. If the
41393 current description was read from a file, @value{GDBN} will look for
41394 @var{document} as a file in the same directory where it found the
41395 original description.
41397 @subsection Architecture
41398 @cindex <architecture>
41400 An @samp{<architecture>} element has this form:
41403 <architecture>@var{arch}</architecture>
41406 @var{arch} is one of the architectures from the set accepted by
41407 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41410 @cindex @code{<osabi>}
41412 This optional field was introduced in @value{GDBN} version 7.0.
41413 Previous versions of @value{GDBN} ignore it.
41415 An @samp{<osabi>} element has this form:
41418 <osabi>@var{abi-name}</osabi>
41421 @var{abi-name} is an OS ABI name from the same selection accepted by
41422 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41424 @subsection Compatible Architecture
41425 @cindex @code{<compatible>}
41427 This optional field was introduced in @value{GDBN} version 7.0.
41428 Previous versions of @value{GDBN} ignore it.
41430 A @samp{<compatible>} element has this form:
41433 <compatible>@var{arch}</compatible>
41436 @var{arch} is one of the architectures from the set accepted by
41437 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41439 A @samp{<compatible>} element is used to specify that the target
41440 is able to run binaries in some other than the main target architecture
41441 given by the @samp{<architecture>} element. For example, on the
41442 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41443 or @code{powerpc:common64}, but the system is able to run binaries
41444 in the @code{spu} architecture as well. The way to describe this
41445 capability with @samp{<compatible>} is as follows:
41448 <architecture>powerpc:common</architecture>
41449 <compatible>spu</compatible>
41452 @subsection Features
41455 Each @samp{<feature>} describes some logical portion of the target
41456 system. Features are currently used to describe available CPU
41457 registers and the types of their contents. A @samp{<feature>} element
41461 <feature name="@var{name}">
41462 @r{[}@var{type}@dots{}@r{]}
41468 Each feature's name should be unique within the description. The name
41469 of a feature does not matter unless @value{GDBN} has some special
41470 knowledge of the contents of that feature; if it does, the feature
41471 should have its standard name. @xref{Standard Target Features}.
41475 Any register's value is a collection of bits which @value{GDBN} must
41476 interpret. The default interpretation is a two's complement integer,
41477 but other types can be requested by name in the register description.
41478 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41479 Target Types}), and the description can define additional composite
41482 Each type element must have an @samp{id} attribute, which gives
41483 a unique (within the containing @samp{<feature>}) name to the type.
41484 Types must be defined before they are used.
41487 Some targets offer vector registers, which can be treated as arrays
41488 of scalar elements. These types are written as @samp{<vector>} elements,
41489 specifying the array element type, @var{type}, and the number of elements,
41493 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41497 If a register's value is usefully viewed in multiple ways, define it
41498 with a union type containing the useful representations. The
41499 @samp{<union>} element contains one or more @samp{<field>} elements,
41500 each of which has a @var{name} and a @var{type}:
41503 <union id="@var{id}">
41504 <field name="@var{name}" type="@var{type}"/>
41511 If a register's value is composed from several separate values, define
41512 it with either a structure type or a flags type.
41513 A flags type may only contain bitfields.
41514 A structure type may either contain only bitfields or contain no bitfields.
41515 If the value contains only bitfields, its total size in bytes must be
41518 Non-bitfield values have a @var{name} and @var{type}.
41521 <struct id="@var{id}">
41522 <field name="@var{name}" type="@var{type}"/>
41527 Both @var{name} and @var{type} values are required.
41528 No implicit padding is added.
41530 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41533 <struct id="@var{id}" size="@var{size}">
41534 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41540 <flags id="@var{id}" size="@var{size}">
41541 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41546 The @var{name} value is required.
41547 Bitfield values may be named with the empty string, @samp{""},
41548 in which case the field is ``filler'' and its value is not printed.
41549 Not all bits need to be specified, so ``filler'' fields are optional.
41551 The @var{start} and @var{end} values are required, and @var{type}
41553 The field's @var{start} must be less than or equal to its @var{end},
41554 and zero represents the least significant bit.
41556 The default value of @var{type} is @code{bool} for single bit fields,
41557 and an unsigned integer otherwise.
41559 Which to choose? Structures or flags?
41561 Registers defined with @samp{flags} have these advantages over
41562 defining them with @samp{struct}:
41566 Arithmetic may be performed on them as if they were integers.
41568 They are printed in a more readable fashion.
41571 Registers defined with @samp{struct} have one advantage over
41572 defining them with @samp{flags}:
41576 One can fetch individual fields like in @samp{C}.
41579 (gdb) print $my_struct_reg.field3
41585 @subsection Registers
41588 Each register is represented as an element with this form:
41591 <reg name="@var{name}"
41592 bitsize="@var{size}"
41593 @r{[}regnum="@var{num}"@r{]}
41594 @r{[}save-restore="@var{save-restore}"@r{]}
41595 @r{[}type="@var{type}"@r{]}
41596 @r{[}group="@var{group}"@r{]}/>
41600 The components are as follows:
41605 The register's name; it must be unique within the target description.
41608 The register's size, in bits.
41611 The register's number. If omitted, a register's number is one greater
41612 than that of the previous register (either in the current feature or in
41613 a preceding feature); the first register in the target description
41614 defaults to zero. This register number is used to read or write
41615 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41616 packets, and registers appear in the @code{g} and @code{G} packets
41617 in order of increasing register number.
41620 Whether the register should be preserved across inferior function
41621 calls; this must be either @code{yes} or @code{no}. The default is
41622 @code{yes}, which is appropriate for most registers except for
41623 some system control registers; this is not related to the target's
41627 The type of the register. It may be a predefined type, a type
41628 defined in the current feature, or one of the special types @code{int}
41629 and @code{float}. @code{int} is an integer type of the correct size
41630 for @var{bitsize}, and @code{float} is a floating point type (in the
41631 architecture's normal floating point format) of the correct size for
41632 @var{bitsize}. The default is @code{int}.
41635 The register group to which this register belongs. It must
41636 be either @code{general}, @code{float}, or @code{vector}. If no
41637 @var{group} is specified, @value{GDBN} will not display the register
41638 in @code{info registers}.
41642 @node Predefined Target Types
41643 @section Predefined Target Types
41644 @cindex target descriptions, predefined types
41646 Type definitions in the self-description can build up composite types
41647 from basic building blocks, but can not define fundamental types. Instead,
41648 standard identifiers are provided by @value{GDBN} for the fundamental
41649 types. The currently supported types are:
41654 Boolean type, occupying a single bit.
41661 Signed integer types holding the specified number of bits.
41668 Unsigned integer types holding the specified number of bits.
41672 Pointers to unspecified code and data. The program counter and
41673 any dedicated return address register may be marked as code
41674 pointers; printing a code pointer converts it into a symbolic
41675 address. The stack pointer and any dedicated address registers
41676 may be marked as data pointers.
41679 Single precision IEEE floating point.
41682 Double precision IEEE floating point.
41685 The 12-byte extended precision format used by ARM FPA registers.
41688 The 10-byte extended precision format used by x87 registers.
41691 32bit @sc{eflags} register used by x86.
41694 32bit @sc{mxcsr} register used by x86.
41698 @node Enum Target Types
41699 @section Enum Target Types
41700 @cindex target descriptions, enum types
41702 Enum target types are useful in @samp{struct} and @samp{flags}
41703 register descriptions. @xref{Target Description Format}.
41705 Enum types have a name, size and a list of name/value pairs.
41708 <enum id="@var{id}" size="@var{size}">
41709 <evalue name="@var{name}" value="@var{value}"/>
41714 Enums must be defined before they are used.
41717 <enum id="levels_type" size="4">
41718 <evalue name="low" value="0"/>
41719 <evalue name="high" value="1"/>
41721 <flags id="flags_type" size="4">
41722 <field name="X" start="0"/>
41723 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41725 <reg name="flags" bitsize="32" type="flags_type"/>
41728 Given that description, a value of 3 for the @samp{flags} register
41729 would be printed as:
41732 (gdb) info register flags
41733 flags 0x3 [ X LEVEL=high ]
41736 @node Standard Target Features
41737 @section Standard Target Features
41738 @cindex target descriptions, standard features
41740 A target description must contain either no registers or all the
41741 target's registers. If the description contains no registers, then
41742 @value{GDBN} will assume a default register layout, selected based on
41743 the architecture. If the description contains any registers, the
41744 default layout will not be used; the standard registers must be
41745 described in the target description, in such a way that @value{GDBN}
41746 can recognize them.
41748 This is accomplished by giving specific names to feature elements
41749 which contain standard registers. @value{GDBN} will look for features
41750 with those names and verify that they contain the expected registers;
41751 if any known feature is missing required registers, or if any required
41752 feature is missing, @value{GDBN} will reject the target
41753 description. You can add additional registers to any of the
41754 standard features --- @value{GDBN} will display them just as if
41755 they were added to an unrecognized feature.
41757 This section lists the known features and their expected contents.
41758 Sample XML documents for these features are included in the
41759 @value{GDBN} source tree, in the directory @file{gdb/features}.
41761 Names recognized by @value{GDBN} should include the name of the
41762 company or organization which selected the name, and the overall
41763 architecture to which the feature applies; so e.g.@: the feature
41764 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41766 The names of registers are not case sensitive for the purpose
41767 of recognizing standard features, but @value{GDBN} will only display
41768 registers using the capitalization used in the description.
41771 * AArch64 Features::
41775 * MicroBlaze Features::
41779 * Nios II Features::
41780 * OpenRISC 1000 Features::
41781 * PowerPC Features::
41782 * S/390 and System z Features::
41788 @node AArch64 Features
41789 @subsection AArch64 Features
41790 @cindex target descriptions, AArch64 features
41792 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41793 targets. It should contain registers @samp{x0} through @samp{x30},
41794 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41796 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41797 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41801 @subsection ARC Features
41802 @cindex target descriptions, ARC Features
41804 ARC processors are highly configurable, so even core registers and their number
41805 are not completely predetermined. In addition flags and PC registers which are
41806 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41807 that one of the core registers features is present.
41808 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41810 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41811 targets with a normal register file. It should contain registers @samp{r0}
41812 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41813 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41814 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41815 @samp{ilink} and extension core registers are not available to read/write, when
41816 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41818 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41819 ARC HS targets with a reduced register file. It should contain registers
41820 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41821 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41822 This feature may contain register @samp{ilink} and any of extension core
41823 registers @samp{r32} through @samp{r59/acch}.
41825 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41826 targets with a normal register file. It should contain registers @samp{r0}
41827 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41828 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41829 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41830 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41831 registers are not available when debugging GNU/Linux applications. The only
41832 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41833 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41834 ARC v2, but @samp{ilink2} is optional on ARCompact.
41836 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41837 targets. It should contain registers @samp{pc} and @samp{status32}.
41840 @subsection ARM Features
41841 @cindex target descriptions, ARM features
41843 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41845 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41846 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41848 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41849 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41850 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41853 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41854 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41856 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41857 it should contain at least registers @samp{wR0} through @samp{wR15} and
41858 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41859 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41861 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41862 should contain at least registers @samp{d0} through @samp{d15}. If
41863 they are present, @samp{d16} through @samp{d31} should also be included.
41864 @value{GDBN} will synthesize the single-precision registers from
41865 halves of the double-precision registers.
41867 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41868 need to contain registers; it instructs @value{GDBN} to display the
41869 VFP double-precision registers as vectors and to synthesize the
41870 quad-precision registers from pairs of double-precision registers.
41871 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41872 be present and include 32 double-precision registers.
41874 @node i386 Features
41875 @subsection i386 Features
41876 @cindex target descriptions, i386 features
41878 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41879 targets. It should describe the following registers:
41883 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41885 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41887 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41888 @samp{fs}, @samp{gs}
41890 @samp{st0} through @samp{st7}
41892 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41893 @samp{foseg}, @samp{fooff} and @samp{fop}
41896 The register sets may be different, depending on the target.
41898 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41899 describe registers:
41903 @samp{xmm0} through @samp{xmm7} for i386
41905 @samp{xmm0} through @samp{xmm15} for amd64
41910 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41911 @samp{org.gnu.gdb.i386.sse} feature. It should
41912 describe the upper 128 bits of @sc{ymm} registers:
41916 @samp{ymm0h} through @samp{ymm7h} for i386
41918 @samp{ymm0h} through @samp{ymm15h} for amd64
41921 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41922 Memory Protection Extension (MPX). It should describe the following registers:
41926 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41928 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41931 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41932 describe a single register, @samp{orig_eax}.
41934 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41935 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41937 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41938 @samp{org.gnu.gdb.i386.avx} feature. It should
41939 describe additional @sc{xmm} registers:
41943 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41946 It should describe the upper 128 bits of additional @sc{ymm} registers:
41950 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41954 describe the upper 256 bits of @sc{zmm} registers:
41958 @samp{zmm0h} through @samp{zmm7h} for i386.
41960 @samp{zmm0h} through @samp{zmm15h} for amd64.
41964 describe the additional @sc{zmm} registers:
41968 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41971 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41972 describe a single register, @samp{pkru}. It is a 32-bit register
41973 valid for i386 and amd64.
41975 @node MicroBlaze Features
41976 @subsection MicroBlaze Features
41977 @cindex target descriptions, MicroBlaze features
41979 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41980 targets. It should contain registers @samp{r0} through @samp{r31},
41981 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41982 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41983 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41985 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41986 If present, it should contain registers @samp{rshr} and @samp{rslr}
41988 @node MIPS Features
41989 @subsection @acronym{MIPS} Features
41990 @cindex target descriptions, @acronym{MIPS} features
41992 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41993 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41994 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41997 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41998 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41999 registers. They may be 32-bit or 64-bit depending on the target.
42001 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42002 it may be optional in a future version of @value{GDBN}. It should
42003 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42004 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42006 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42007 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42008 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42009 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42011 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42012 contain a single register, @samp{restart}, which is used by the
42013 Linux kernel to control restartable syscalls.
42015 @node M68K Features
42016 @subsection M68K Features
42017 @cindex target descriptions, M68K features
42020 @item @samp{org.gnu.gdb.m68k.core}
42021 @itemx @samp{org.gnu.gdb.coldfire.core}
42022 @itemx @samp{org.gnu.gdb.fido.core}
42023 One of those features must be always present.
42024 The feature that is present determines which flavor of m68k is
42025 used. The feature that is present should contain registers
42026 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42027 @samp{sp}, @samp{ps} and @samp{pc}.
42029 @item @samp{org.gnu.gdb.coldfire.fp}
42030 This feature is optional. If present, it should contain registers
42031 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42035 @node NDS32 Features
42036 @subsection NDS32 Features
42037 @cindex target descriptions, NDS32 features
42039 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42040 targets. It should contain at least registers @samp{r0} through
42041 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42044 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42045 it should contain 64-bit double-precision floating-point registers
42046 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42047 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42049 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42050 registers are overlapped with the thirty-two 32-bit single-precision
42051 floating-point registers. The 32-bit single-precision registers, if
42052 not being listed explicitly, will be synthesized from halves of the
42053 overlapping 64-bit double-precision registers. Listing 32-bit
42054 single-precision registers explicitly is deprecated, and the
42055 support to it could be totally removed some day.
42057 @node Nios II Features
42058 @subsection Nios II Features
42059 @cindex target descriptions, Nios II features
42061 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42062 targets. It should contain the 32 core registers (@samp{zero},
42063 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42064 @samp{pc}, and the 16 control registers (@samp{status} through
42067 @node OpenRISC 1000 Features
42068 @subsection Openrisc 1000 Features
42069 @cindex target descriptions, OpenRISC 1000 features
42071 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42072 targets. It should contain the 32 general purpose registers (@samp{r0}
42073 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42075 @node PowerPC Features
42076 @subsection PowerPC Features
42077 @cindex target descriptions, PowerPC features
42079 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42080 targets. It should contain registers @samp{r0} through @samp{r31},
42081 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42082 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42084 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42085 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42087 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42088 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42091 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42092 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42093 will combine these registers with the floating point registers
42094 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42095 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42096 through @samp{vs63}, the set of vector registers for POWER7.
42098 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42099 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42100 @samp{spefscr}. SPE targets should provide 32-bit registers in
42101 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42102 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42103 these to present registers @samp{ev0} through @samp{ev31} to the
42106 @node S/390 and System z Features
42107 @subsection S/390 and System z Features
42108 @cindex target descriptions, S/390 features
42109 @cindex target descriptions, System z features
42111 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42112 System z targets. It should contain the PSW and the 16 general
42113 registers. In particular, System z targets should provide the 64-bit
42114 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42115 S/390 targets should provide the 32-bit versions of these registers.
42116 A System z target that runs in 31-bit addressing mode should provide
42117 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42118 register's upper halves @samp{r0h} through @samp{r15h}, and their
42119 lower halves @samp{r0l} through @samp{r15l}.
42121 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42122 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42125 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42126 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42128 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42129 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42130 targets and 32-bit otherwise. In addition, the feature may contain
42131 the @samp{last_break} register, whose width depends on the addressing
42132 mode, as well as the @samp{system_call} register, which is always
42135 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42136 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42137 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42139 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42140 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42141 combined by @value{GDBN} with the floating point registers @samp{f0}
42142 through @samp{f15} to present the 128-bit wide vector registers
42143 @samp{v0} through @samp{v15}. In addition, this feature should
42144 contain the 128-bit wide vector registers @samp{v16} through
42147 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42148 the 64-bit wide guarded-storage-control registers @samp{gsd},
42149 @samp{gssm}, and @samp{gsepla}.
42151 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42152 the 64-bit wide guarded-storage broadcast control registers
42153 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42155 @node Sparc Features
42156 @subsection Sparc Features
42157 @cindex target descriptions, sparc32 features
42158 @cindex target descriptions, sparc64 features
42159 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42160 targets. It should describe the following registers:
42164 @samp{g0} through @samp{g7}
42166 @samp{o0} through @samp{o7}
42168 @samp{l0} through @samp{l7}
42170 @samp{i0} through @samp{i7}
42173 They may be 32-bit or 64-bit depending on the target.
42175 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42176 targets. It should describe the following registers:
42180 @samp{f0} through @samp{f31}
42182 @samp{f32} through @samp{f62} for sparc64
42185 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42186 targets. It should describe the following registers:
42190 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42191 @samp{fsr}, and @samp{csr} for sparc32
42193 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42197 @node TIC6x Features
42198 @subsection TMS320C6x Features
42199 @cindex target descriptions, TIC6x features
42200 @cindex target descriptions, TMS320C6x features
42201 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42202 targets. It should contain registers @samp{A0} through @samp{A15},
42203 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42205 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42206 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42207 through @samp{B31}.
42209 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42210 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42212 @node Operating System Information
42213 @appendix Operating System Information
42214 @cindex operating system information
42220 Users of @value{GDBN} often wish to obtain information about the state of
42221 the operating system running on the target---for example the list of
42222 processes, or the list of open files. This section describes the
42223 mechanism that makes it possible. This mechanism is similar to the
42224 target features mechanism (@pxref{Target Descriptions}), but focuses
42225 on a different aspect of target.
42227 Operating system information is retrived from the target via the
42228 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42229 read}). The object name in the request should be @samp{osdata}, and
42230 the @var{annex} identifies the data to be fetched.
42233 @appendixsection Process list
42234 @cindex operating system information, process list
42236 When requesting the process list, the @var{annex} field in the
42237 @samp{qXfer} request should be @samp{processes}. The returned data is
42238 an XML document. The formal syntax of this document is defined in
42239 @file{gdb/features/osdata.dtd}.
42241 An example document is:
42244 <?xml version="1.0"?>
42245 <!DOCTYPE target SYSTEM "osdata.dtd">
42246 <osdata type="processes">
42248 <column name="pid">1</column>
42249 <column name="user">root</column>
42250 <column name="command">/sbin/init</column>
42251 <column name="cores">1,2,3</column>
42256 Each item should include a column whose name is @samp{pid}. The value
42257 of that column should identify the process on the target. The
42258 @samp{user} and @samp{command} columns are optional, and will be
42259 displayed by @value{GDBN}. The @samp{cores} column, if present,
42260 should contain a comma-separated list of cores that this process
42261 is running on. Target may provide additional columns,
42262 which @value{GDBN} currently ignores.
42264 @node Trace File Format
42265 @appendix Trace File Format
42266 @cindex trace file format
42268 The trace file comes in three parts: a header, a textual description
42269 section, and a trace frame section with binary data.
42271 The header has the form @code{\x7fTRACE0\n}. The first byte is
42272 @code{0x7f} so as to indicate that the file contains binary data,
42273 while the @code{0} is a version number that may have different values
42276 The description section consists of multiple lines of @sc{ascii} text
42277 separated by newline characters (@code{0xa}). The lines may include a
42278 variety of optional descriptive or context-setting information, such
42279 as tracepoint definitions or register set size. @value{GDBN} will
42280 ignore any line that it does not recognize. An empty line marks the end
42285 Specifies the size of a register block in bytes. This is equal to the
42286 size of a @code{g} packet payload in the remote protocol. @var{size}
42287 is an ascii decimal number. There should be only one such line in
42288 a single trace file.
42290 @item status @var{status}
42291 Trace status. @var{status} has the same format as a @code{qTStatus}
42292 remote packet reply. There should be only one such line in a single trace
42295 @item tp @var{payload}
42296 Tracepoint definition. The @var{payload} has the same format as
42297 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42298 may take multiple lines of definition, corresponding to the multiple
42301 @item tsv @var{payload}
42302 Trace state variable definition. The @var{payload} has the same format as
42303 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42304 may take multiple lines of definition, corresponding to the multiple
42307 @item tdesc @var{payload}
42308 Target description in XML format. The @var{payload} is a single line of
42309 the XML file. All such lines should be concatenated together to get
42310 the original XML file. This file is in the same format as @code{qXfer}
42311 @code{features} payload, and corresponds to the main @code{target.xml}
42312 file. Includes are not allowed.
42316 The trace frame section consists of a number of consecutive frames.
42317 Each frame begins with a two-byte tracepoint number, followed by a
42318 four-byte size giving the amount of data in the frame. The data in
42319 the frame consists of a number of blocks, each introduced by a
42320 character indicating its type (at least register, memory, and trace
42321 state variable). The data in this section is raw binary, not a
42322 hexadecimal or other encoding; its endianness matches the target's
42325 @c FIXME bi-arch may require endianness/arch info in description section
42328 @item R @var{bytes}
42329 Register block. The number and ordering of bytes matches that of a
42330 @code{g} packet in the remote protocol. Note that these are the
42331 actual bytes, in target order, not a hexadecimal encoding.
42333 @item M @var{address} @var{length} @var{bytes}...
42334 Memory block. This is a contiguous block of memory, at the 8-byte
42335 address @var{address}, with a 2-byte length @var{length}, followed by
42336 @var{length} bytes.
42338 @item V @var{number} @var{value}
42339 Trace state variable block. This records the 8-byte signed value
42340 @var{value} of trace state variable numbered @var{number}.
42344 Future enhancements of the trace file format may include additional types
42347 @node Index Section Format
42348 @appendix @code{.gdb_index} section format
42349 @cindex .gdb_index section format
42350 @cindex index section format
42352 This section documents the index section that is created by @code{save
42353 gdb-index} (@pxref{Index Files}). The index section is
42354 DWARF-specific; some knowledge of DWARF is assumed in this
42357 The mapped index file format is designed to be directly
42358 @code{mmap}able on any architecture. In most cases, a datum is
42359 represented using a little-endian 32-bit integer value, called an
42360 @code{offset_type}. Big endian machines must byte-swap the values
42361 before using them. Exceptions to this rule are noted. The data is
42362 laid out such that alignment is always respected.
42364 A mapped index consists of several areas, laid out in order.
42368 The file header. This is a sequence of values, of @code{offset_type}
42369 unless otherwise noted:
42373 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42374 Version 4 uses a different hashing function from versions 5 and 6.
42375 Version 6 includes symbols for inlined functions, whereas versions 4
42376 and 5 do not. Version 7 adds attributes to the CU indices in the
42377 symbol table. Version 8 specifies that symbols from DWARF type units
42378 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42379 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42381 @value{GDBN} will only read version 4, 5, or 6 indices
42382 by specifying @code{set use-deprecated-index-sections on}.
42383 GDB has a workaround for potentially broken version 7 indices so it is
42384 currently not flagged as deprecated.
42387 The offset, from the start of the file, of the CU list.
42390 The offset, from the start of the file, of the types CU list. Note
42391 that this area can be empty, in which case this offset will be equal
42392 to the next offset.
42395 The offset, from the start of the file, of the address area.
42398 The offset, from the start of the file, of the symbol table.
42401 The offset, from the start of the file, of the constant pool.
42405 The CU list. This is a sequence of pairs of 64-bit little-endian
42406 values, sorted by the CU offset. The first element in each pair is
42407 the offset of a CU in the @code{.debug_info} section. The second
42408 element in each pair is the length of that CU. References to a CU
42409 elsewhere in the map are done using a CU index, which is just the
42410 0-based index into this table. Note that if there are type CUs, then
42411 conceptually CUs and type CUs form a single list for the purposes of
42415 The types CU list. This is a sequence of triplets of 64-bit
42416 little-endian values. In a triplet, the first value is the CU offset,
42417 the second value is the type offset in the CU, and the third value is
42418 the type signature. The types CU list is not sorted.
42421 The address area. The address area consists of a sequence of address
42422 entries. Each address entry has three elements:
42426 The low address. This is a 64-bit little-endian value.
42429 The high address. This is a 64-bit little-endian value. Like
42430 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42433 The CU index. This is an @code{offset_type} value.
42437 The symbol table. This is an open-addressed hash table. The size of
42438 the hash table is always a power of 2.
42440 Each slot in the hash table consists of a pair of @code{offset_type}
42441 values. The first value is the offset of the symbol's name in the
42442 constant pool. The second value is the offset of the CU vector in the
42445 If both values are 0, then this slot in the hash table is empty. This
42446 is ok because while 0 is a valid constant pool index, it cannot be a
42447 valid index for both a string and a CU vector.
42449 The hash value for a table entry is computed by applying an
42450 iterative hash function to the symbol's name. Starting with an
42451 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42452 the string is incorporated into the hash using the formula depending on the
42457 The formula is @code{r = r * 67 + c - 113}.
42459 @item Versions 5 to 7
42460 The formula is @code{r = r * 67 + tolower (c) - 113}.
42463 The terminating @samp{\0} is not incorporated into the hash.
42465 The step size used in the hash table is computed via
42466 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42467 value, and @samp{size} is the size of the hash table. The step size
42468 is used to find the next candidate slot when handling a hash
42471 The names of C@t{++} symbols in the hash table are canonicalized. We
42472 don't currently have a simple description of the canonicalization
42473 algorithm; if you intend to create new index sections, you must read
42477 The constant pool. This is simply a bunch of bytes. It is organized
42478 so that alignment is correct: CU vectors are stored first, followed by
42481 A CU vector in the constant pool is a sequence of @code{offset_type}
42482 values. The first value is the number of CU indices in the vector.
42483 Each subsequent value is the index and symbol attributes of a CU in
42484 the CU list. This element in the hash table is used to indicate which
42485 CUs define the symbol and how the symbol is used.
42486 See below for the format of each CU index+attributes entry.
42488 A string in the constant pool is zero-terminated.
42491 Attributes were added to CU index values in @code{.gdb_index} version 7.
42492 If a symbol has multiple uses within a CU then there is one
42493 CU index+attributes value for each use.
42495 The format of each CU index+attributes entry is as follows
42501 This is the index of the CU in the CU list.
42503 These bits are reserved for future purposes and must be zero.
42505 The kind of the symbol in the CU.
42509 This value is reserved and should not be used.
42510 By reserving zero the full @code{offset_type} value is backwards compatible
42511 with previous versions of the index.
42513 The symbol is a type.
42515 The symbol is a variable or an enum value.
42517 The symbol is a function.
42519 Any other kind of symbol.
42521 These values are reserved.
42525 This bit is zero if the value is global and one if it is static.
42527 The determination of whether a symbol is global or static is complicated.
42528 The authorative reference is the file @file{dwarf2read.c} in
42529 @value{GDBN} sources.
42533 This pseudo-code describes the computation of a symbol's kind and
42534 global/static attributes in the index.
42537 is_external = get_attribute (die, DW_AT_external);
42538 language = get_attribute (cu_die, DW_AT_language);
42541 case DW_TAG_typedef:
42542 case DW_TAG_base_type:
42543 case DW_TAG_subrange_type:
42547 case DW_TAG_enumerator:
42549 is_static = language != CPLUS;
42551 case DW_TAG_subprogram:
42553 is_static = ! (is_external || language == ADA);
42555 case DW_TAG_constant:
42557 is_static = ! is_external;
42559 case DW_TAG_variable:
42561 is_static = ! is_external;
42563 case DW_TAG_namespace:
42567 case DW_TAG_class_type:
42568 case DW_TAG_interface_type:
42569 case DW_TAG_structure_type:
42570 case DW_TAG_union_type:
42571 case DW_TAG_enumeration_type:
42573 is_static = language != CPLUS;
42581 @appendix Manual pages
42585 * gdb man:: The GNU Debugger man page
42586 * gdbserver man:: Remote Server for the GNU Debugger man page
42587 * gcore man:: Generate a core file of a running program
42588 * gdbinit man:: gdbinit scripts
42594 @c man title gdb The GNU Debugger
42596 @c man begin SYNOPSIS gdb
42597 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42598 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42599 [@option{-b}@w{ }@var{bps}]
42600 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42601 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42602 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42603 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42604 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42607 @c man begin DESCRIPTION gdb
42608 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42609 going on ``inside'' another program while it executes -- or what another
42610 program was doing at the moment it crashed.
42612 @value{GDBN} can do four main kinds of things (plus other things in support of
42613 these) to help you catch bugs in the act:
42617 Start your program, specifying anything that might affect its behavior.
42620 Make your program stop on specified conditions.
42623 Examine what has happened, when your program has stopped.
42626 Change things in your program, so you can experiment with correcting the
42627 effects of one bug and go on to learn about another.
42630 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42633 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42634 commands from the terminal until you tell it to exit with the @value{GDBN}
42635 command @code{quit}. You can get online help from @value{GDBN} itself
42636 by using the command @code{help}.
42638 You can run @code{gdb} with no arguments or options; but the most
42639 usual way to start @value{GDBN} is with one argument or two, specifying an
42640 executable program as the argument:
42646 You can also start with both an executable program and a core file specified:
42652 You can, instead, specify a process ID as a second argument, if you want
42653 to debug a running process:
42661 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42662 named @file{1234}; @value{GDBN} does check for a core file first).
42663 With option @option{-p} you can omit the @var{program} filename.
42665 Here are some of the most frequently needed @value{GDBN} commands:
42667 @c pod2man highlights the right hand side of the @item lines.
42669 @item break [@var{file}:]@var{function}
42670 Set a breakpoint at @var{function} (in @var{file}).
42672 @item run [@var{arglist}]
42673 Start your program (with @var{arglist}, if specified).
42676 Backtrace: display the program stack.
42678 @item print @var{expr}
42679 Display the value of an expression.
42682 Continue running your program (after stopping, e.g. at a breakpoint).
42685 Execute next program line (after stopping); step @emph{over} any
42686 function calls in the line.
42688 @item edit [@var{file}:]@var{function}
42689 look at the program line where it is presently stopped.
42691 @item list [@var{file}:]@var{function}
42692 type the text of the program in the vicinity of where it is presently stopped.
42695 Execute next program line (after stopping); step @emph{into} any
42696 function calls in the line.
42698 @item help [@var{name}]
42699 Show information about @value{GDBN} command @var{name}, or general information
42700 about using @value{GDBN}.
42703 Exit from @value{GDBN}.
42707 For full details on @value{GDBN},
42708 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42709 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42710 as the @code{gdb} entry in the @code{info} program.
42714 @c man begin OPTIONS gdb
42715 Any arguments other than options specify an executable
42716 file and core file (or process ID); that is, the first argument
42717 encountered with no
42718 associated option flag is equivalent to a @option{-se} option, and the second,
42719 if any, is equivalent to a @option{-c} option if it's the name of a file.
42721 both long and short forms; both are shown here. The long forms are also
42722 recognized if you truncate them, so long as enough of the option is
42723 present to be unambiguous. (If you prefer, you can flag option
42724 arguments with @option{+} rather than @option{-}, though we illustrate the
42725 more usual convention.)
42727 All the options and command line arguments you give are processed
42728 in sequential order. The order makes a difference when the @option{-x}
42734 List all options, with brief explanations.
42736 @item -symbols=@var{file}
42737 @itemx -s @var{file}
42738 Read symbol table from file @var{file}.
42741 Enable writing into executable and core files.
42743 @item -exec=@var{file}
42744 @itemx -e @var{file}
42745 Use file @var{file} as the executable file to execute when
42746 appropriate, and for examining pure data in conjunction with a core
42749 @item -se=@var{file}
42750 Read symbol table from file @var{file} and use it as the executable
42753 @item -core=@var{file}
42754 @itemx -c @var{file}
42755 Use file @var{file} as a core dump to examine.
42757 @item -command=@var{file}
42758 @itemx -x @var{file}
42759 Execute @value{GDBN} commands from file @var{file}.
42761 @item -ex @var{command}
42762 Execute given @value{GDBN} @var{command}.
42764 @item -directory=@var{directory}
42765 @itemx -d @var{directory}
42766 Add @var{directory} to the path to search for source files.
42769 Do not execute commands from @file{~/.gdbinit}.
42773 Do not execute commands from any @file{.gdbinit} initialization files.
42777 ``Quiet''. Do not print the introductory and copyright messages. These
42778 messages are also suppressed in batch mode.
42781 Run in batch mode. Exit with status @code{0} after processing all the command
42782 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42783 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42784 commands in the command files.
42786 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42787 download and run a program on another computer; in order to make this
42788 more useful, the message
42791 Program exited normally.
42795 (which is ordinarily issued whenever a program running under @value{GDBN} control
42796 terminates) is not issued when running in batch mode.
42798 @item -cd=@var{directory}
42799 Run @value{GDBN} using @var{directory} as its working directory,
42800 instead of the current directory.
42804 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42805 @value{GDBN} to output the full file name and line number in a standard,
42806 recognizable fashion each time a stack frame is displayed (which
42807 includes each time the program stops). This recognizable format looks
42808 like two @samp{\032} characters, followed by the file name, line number
42809 and character position separated by colons, and a newline. The
42810 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42811 characters as a signal to display the source code for the frame.
42814 Set the line speed (baud rate or bits per second) of any serial
42815 interface used by @value{GDBN} for remote debugging.
42817 @item -tty=@var{device}
42818 Run using @var{device} for your program's standard input and output.
42822 @c man begin SEEALSO gdb
42824 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42825 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42826 documentation are properly installed at your site, the command
42833 should give you access to the complete manual.
42835 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42836 Richard M. Stallman and Roland H. Pesch, July 1991.
42840 @node gdbserver man
42841 @heading gdbserver man
42843 @c man title gdbserver Remote Server for the GNU Debugger
42845 @c man begin SYNOPSIS gdbserver
42846 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42848 gdbserver --attach @var{comm} @var{pid}
42850 gdbserver --multi @var{comm}
42854 @c man begin DESCRIPTION gdbserver
42855 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42856 than the one which is running the program being debugged.
42859 @subheading Usage (server (target) side)
42862 Usage (server (target) side):
42865 First, you need to have a copy of the program you want to debug put onto
42866 the target system. The program can be stripped to save space if needed, as
42867 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42868 the @value{GDBN} running on the host system.
42870 To use the server, you log on to the target system, and run the @command{gdbserver}
42871 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42872 your program, and (c) its arguments. The general syntax is:
42875 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42878 For example, using a serial port, you might say:
42882 @c @file would wrap it as F</dev/com1>.
42883 target> gdbserver /dev/com1 emacs foo.txt
42886 target> gdbserver @file{/dev/com1} emacs foo.txt
42890 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42891 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42892 waits patiently for the host @value{GDBN} to communicate with it.
42894 To use a TCP connection, you could say:
42897 target> gdbserver host:2345 emacs foo.txt
42900 This says pretty much the same thing as the last example, except that we are
42901 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42902 that we are expecting to see a TCP connection from @code{host} to local TCP port
42903 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42904 want for the port number as long as it does not conflict with any existing TCP
42905 ports on the target system. This same port number must be used in the host
42906 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42907 you chose a port number that conflicts with another service, @command{gdbserver} will
42908 print an error message and exit.
42910 @command{gdbserver} can also attach to running programs.
42911 This is accomplished via the @option{--attach} argument. The syntax is:
42914 target> gdbserver --attach @var{comm} @var{pid}
42917 @var{pid} is the process ID of a currently running process. It isn't
42918 necessary to point @command{gdbserver} at a binary for the running process.
42920 To start @code{gdbserver} without supplying an initial command to run
42921 or process ID to attach, use the @option{--multi} command line option.
42922 In such case you should connect using @kbd{target extended-remote} to start
42923 the program you want to debug.
42926 target> gdbserver --multi @var{comm}
42930 @subheading Usage (host side)
42936 You need an unstripped copy of the target program on your host system, since
42937 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42938 would, with the target program as the first argument. (You may need to use the
42939 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42940 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42941 new command you need to know about is @code{target remote}
42942 (or @code{target extended-remote}). Its argument is either
42943 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42944 descriptor. For example:
42948 @c @file would wrap it as F</dev/ttyb>.
42949 (gdb) target remote /dev/ttyb
42952 (gdb) target remote @file{/dev/ttyb}
42957 communicates with the server via serial line @file{/dev/ttyb}, and:
42960 (gdb) target remote the-target:2345
42964 communicates via a TCP connection to port 2345 on host `the-target', where
42965 you previously started up @command{gdbserver} with the same port number. Note that for
42966 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42967 command, otherwise you may get an error that looks something like
42968 `Connection refused'.
42970 @command{gdbserver} can also debug multiple inferiors at once,
42973 the @value{GDBN} manual in node @code{Inferiors and Programs}
42974 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42977 @ref{Inferiors and Programs}.
42979 In such case use the @code{extended-remote} @value{GDBN} command variant:
42982 (gdb) target extended-remote the-target:2345
42985 The @command{gdbserver} option @option{--multi} may or may not be used in such
42989 @c man begin OPTIONS gdbserver
42990 There are three different modes for invoking @command{gdbserver}:
42995 Debug a specific program specified by its program name:
42998 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43001 The @var{comm} parameter specifies how should the server communicate
43002 with @value{GDBN}; it is either a device name (to use a serial line),
43003 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43004 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43005 debug in @var{prog}. Any remaining arguments will be passed to the
43006 program verbatim. When the program exits, @value{GDBN} will close the
43007 connection, and @code{gdbserver} will exit.
43010 Debug a specific program by specifying the process ID of a running
43014 gdbserver --attach @var{comm} @var{pid}
43017 The @var{comm} parameter is as described above. Supply the process ID
43018 of a running program in @var{pid}; @value{GDBN} will do everything
43019 else. Like with the previous mode, when the process @var{pid} exits,
43020 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43023 Multi-process mode -- debug more than one program/process:
43026 gdbserver --multi @var{comm}
43029 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43030 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43031 close the connection when a process being debugged exits, so you can
43032 debug several processes in the same session.
43035 In each of the modes you may specify these options:
43040 List all options, with brief explanations.
43043 This option causes @command{gdbserver} to print its version number and exit.
43046 @command{gdbserver} will attach to a running program. The syntax is:
43049 target> gdbserver --attach @var{comm} @var{pid}
43052 @var{pid} is the process ID of a currently running process. It isn't
43053 necessary to point @command{gdbserver} at a binary for the running process.
43056 To start @code{gdbserver} without supplying an initial command to run
43057 or process ID to attach, use this command line option.
43058 Then you can connect using @kbd{target extended-remote} and start
43059 the program you want to debug. The syntax is:
43062 target> gdbserver --multi @var{comm}
43066 Instruct @code{gdbserver} to display extra status information about the debugging
43068 This option is intended for @code{gdbserver} development and for bug reports to
43071 @item --remote-debug
43072 Instruct @code{gdbserver} to display remote protocol debug output.
43073 This option is intended for @code{gdbserver} development and for bug reports to
43076 @item --debug-format=option1@r{[},option2,...@r{]}
43077 Instruct @code{gdbserver} to include extra information in each line
43078 of debugging output.
43079 @xref{Other Command-Line Arguments for gdbserver}.
43082 Specify a wrapper to launch programs
43083 for debugging. The option should be followed by the name of the
43084 wrapper, then any command-line arguments to pass to the wrapper, then
43085 @kbd{--} indicating the end of the wrapper arguments.
43088 By default, @command{gdbserver} keeps the listening TCP port open, so that
43089 additional connections are possible. However, if you start @code{gdbserver}
43090 with the @option{--once} option, it will stop listening for any further
43091 connection attempts after connecting to the first @value{GDBN} session.
43093 @c --disable-packet is not documented for users.
43095 @c --disable-randomization and --no-disable-randomization are superseded by
43096 @c QDisableRandomization.
43101 @c man begin SEEALSO gdbserver
43103 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43104 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43105 documentation are properly installed at your site, the command
43111 should give you access to the complete manual.
43113 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43114 Richard M. Stallman and Roland H. Pesch, July 1991.
43121 @c man title gcore Generate a core file of a running program
43124 @c man begin SYNOPSIS gcore
43125 gcore [-a] [-o @var{filename}] @var{pid}
43129 @c man begin DESCRIPTION gcore
43130 Generate a core dump of a running program with process ID @var{pid}.
43131 Produced file is equivalent to a kernel produced core file as if the process
43132 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43133 limit). Unlike after a crash, after @command{gcore} the program remains
43134 running without any change.
43137 @c man begin OPTIONS gcore
43140 Dump all memory mappings. The actual effect of this option depends on
43141 the Operating System. On @sc{gnu}/Linux, it will disable
43142 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43143 enable @code{dump-excluded-mappings} (@pxref{set
43144 dump-excluded-mappings}).
43146 @item -o @var{filename}
43147 The optional argument
43148 @var{filename} specifies the file name where to put the core dump.
43149 If not specified, the file name defaults to @file{core.@var{pid}},
43150 where @var{pid} is the running program process ID.
43154 @c man begin SEEALSO gcore
43156 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43157 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43158 documentation are properly installed at your site, the command
43165 should give you access to the complete manual.
43167 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43168 Richard M. Stallman and Roland H. Pesch, July 1991.
43175 @c man title gdbinit GDB initialization scripts
43178 @c man begin SYNOPSIS gdbinit
43179 @ifset SYSTEM_GDBINIT
43180 @value{SYSTEM_GDBINIT}
43189 @c man begin DESCRIPTION gdbinit
43190 These files contain @value{GDBN} commands to automatically execute during
43191 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43194 the @value{GDBN} manual in node @code{Sequences}
43195 -- shell command @code{info -f gdb -n Sequences}.
43201 Please read more in
43203 the @value{GDBN} manual in node @code{Startup}
43204 -- shell command @code{info -f gdb -n Startup}.
43211 @ifset SYSTEM_GDBINIT
43212 @item @value{SYSTEM_GDBINIT}
43214 @ifclear SYSTEM_GDBINIT
43215 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43217 System-wide initialization file. It is executed unless user specified
43218 @value{GDBN} option @code{-nx} or @code{-n}.
43221 the @value{GDBN} manual in node @code{System-wide configuration}
43222 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43225 @ref{System-wide configuration}.
43229 User initialization file. It is executed unless user specified
43230 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43233 Initialization file for current directory. It may need to be enabled with
43234 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43237 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43238 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43241 @ref{Init File in the Current Directory}.
43246 @c man begin SEEALSO gdbinit
43248 gdb(1), @code{info -f gdb -n Startup}
43250 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43251 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43252 documentation are properly installed at your site, the command
43258 should give you access to the complete manual.
43260 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43261 Richard M. Stallman and Roland H. Pesch, July 1991.
43267 @node GNU Free Documentation License
43268 @appendix GNU Free Documentation License
43271 @node Concept Index
43272 @unnumbered Concept Index
43276 @node Command and Variable Index
43277 @unnumbered Command, Variable, and Function Index
43282 % I think something like @@colophon should be in texinfo. In the
43284 \long\def\colophon{\hbox to0pt{}\vfill
43285 \centerline{The body of this manual is set in}
43286 \centerline{\fontname\tenrm,}
43287 \centerline{with headings in {\bf\fontname\tenbf}}
43288 \centerline{and examples in {\tt\fontname\tentt}.}
43289 \centerline{{\it\fontname\tenit\/},}
43290 \centerline{{\bf\fontname\tenbf}, and}
43291 \centerline{{\sl\fontname\tensl\/}}
43292 \centerline{are used for emphasis.}\vfill}
43294 % Blame: doc@@cygnus.com, 1991.