1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2016 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{} 1988-2016 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) 1988-2016 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.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2661 @vindex $_inferior@r{, convenience variable}
2662 The debugger convenience variable @samp{$_inferior} contains the
2663 number of the current inferior. You may find this useful in writing
2664 breakpoint conditional expressions, command scripts, and so forth.
2665 @xref{Convenience Vars,, Convenience Variables}, for general
2666 information on convenience variables.
2668 You can get multiple executables into a debugging session via the
2669 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2670 systems @value{GDBN} can add inferiors to the debug session
2671 automatically by following calls to @code{fork} and @code{exec}. To
2672 remove inferiors from the debugging session use the
2673 @w{@code{remove-inferiors}} command.
2676 @kindex add-inferior
2677 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2678 Adds @var{n} inferiors to be run using @var{executable} as the
2679 executable; @var{n} defaults to 1. If no executable is specified,
2680 the inferiors begins empty, with no program. You can still assign or
2681 change the program assigned to the inferior at any time by using the
2682 @code{file} command with the executable name as its argument.
2684 @kindex clone-inferior
2685 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2686 Adds @var{n} inferiors ready to execute the same program as inferior
2687 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2688 number of the current inferior. This is a convenient command when you
2689 want to run another instance of the inferior you are debugging.
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2694 * 1 process 29964 helloworld
2695 (@value{GDBP}) clone-inferior
2698 (@value{GDBP}) info inferiors
2699 Num Description Executable
2701 * 1 process 29964 helloworld
2704 You can now simply switch focus to inferior 2 and run it.
2706 @kindex remove-inferiors
2707 @item remove-inferiors @var{infno}@dots{}
2708 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2709 possible to remove an inferior that is running with this command. For
2710 those, use the @code{kill} or @code{detach} command first.
2714 To quit debugging one of the running inferiors that is not the current
2715 inferior, you can either detach from it by using the @w{@code{detach
2716 inferior}} command (allowing it to run independently), or kill it
2717 using the @w{@code{kill inferiors}} command:
2720 @kindex detach inferiors @var{infno}@dots{}
2721 @item detach inferior @var{infno}@dots{}
2722 Detach from the inferior or inferiors identified by @value{GDBN}
2723 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2724 still stays on the list of inferiors shown by @code{info inferiors},
2725 but its Description will show @samp{<null>}.
2727 @kindex kill inferiors @var{infno}@dots{}
2728 @item kill inferiors @var{infno}@dots{}
2729 Kill the inferior or inferiors identified by @value{GDBN} inferior
2730 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2731 stays on the list of inferiors shown by @code{info inferiors}, but its
2732 Description will show @samp{<null>}.
2735 After the successful completion of a command such as @code{detach},
2736 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2737 a normal process exit, the inferior is still valid and listed with
2738 @code{info inferiors}, ready to be restarted.
2741 To be notified when inferiors are started or exit under @value{GDBN}'s
2742 control use @w{@code{set print inferior-events}}:
2745 @kindex set print inferior-events
2746 @cindex print messages on inferior start and exit
2747 @item set print inferior-events
2748 @itemx set print inferior-events on
2749 @itemx set print inferior-events off
2750 The @code{set print inferior-events} command allows you to enable or
2751 disable printing of messages when @value{GDBN} notices that new
2752 inferiors have started or that inferiors have exited or have been
2753 detached. By default, these messages will not be printed.
2755 @kindex show print inferior-events
2756 @item show print inferior-events
2757 Show whether messages will be printed when @value{GDBN} detects that
2758 inferiors have started, exited or have been detached.
2761 Many commands will work the same with multiple programs as with a
2762 single program: e.g., @code{print myglobal} will simply display the
2763 value of @code{myglobal} in the current inferior.
2766 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2767 get more info about the relationship of inferiors, programs, address
2768 spaces in a debug session. You can do that with the @w{@code{maint
2769 info program-spaces}} command.
2772 @kindex maint info program-spaces
2773 @item maint info program-spaces
2774 Print a list of all program spaces currently being managed by
2777 @value{GDBN} displays for each program space (in this order):
2781 the program space number assigned by @value{GDBN}
2784 the name of the executable loaded into the program space, with e.g.,
2785 the @code{file} command.
2790 An asterisk @samp{*} preceding the @value{GDBN} program space number
2791 indicates the current program space.
2793 In addition, below each program space line, @value{GDBN} prints extra
2794 information that isn't suitable to display in tabular form. For
2795 example, the list of inferiors bound to the program space.
2798 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2805 Here we can see that no inferior is running the program @code{hello},
2806 while @code{process 21561} is running the program @code{goodbye}. On
2807 some targets, it is possible that multiple inferiors are bound to the
2808 same program space. The most common example is that of debugging both
2809 the parent and child processes of a @code{vfork} call. For example,
2812 (@value{GDBP}) maint info program-spaces
2815 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2818 Here, both inferior 2 and inferior 1 are running in the same program
2819 space as a result of inferior 1 having executed a @code{vfork} call.
2823 @section Debugging Programs with Multiple Threads
2825 @cindex threads of execution
2826 @cindex multiple threads
2827 @cindex switching threads
2828 In some operating systems, such as GNU/Linux and Solaris, a single program
2829 may have more than one @dfn{thread} of execution. The precise semantics
2830 of threads differ from one operating system to another, but in general
2831 the threads of a single program are akin to multiple processes---except
2832 that they share one address space (that is, they can all examine and
2833 modify the same variables). On the other hand, each thread has its own
2834 registers and execution stack, and perhaps private memory.
2836 @value{GDBN} provides these facilities for debugging multi-thread
2840 @item automatic notification of new threads
2841 @item @samp{thread @var{thread-id}}, a command to switch among threads
2842 @item @samp{info threads}, a command to inquire about existing threads
2843 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2844 a command to apply a command to a list of threads
2845 @item thread-specific breakpoints
2846 @item @samp{set print thread-events}, which controls printing of
2847 messages on thread start and exit.
2848 @item @samp{set libthread-db-search-path @var{path}}, which lets
2849 the user specify which @code{libthread_db} to use if the default choice
2850 isn't compatible with the program.
2853 @cindex focus of debugging
2854 @cindex current thread
2855 The @value{GDBN} thread debugging facility allows you to observe all
2856 threads while your program runs---but whenever @value{GDBN} takes
2857 control, one thread in particular is always the focus of debugging.
2858 This thread is called the @dfn{current thread}. Debugging commands show
2859 program information from the perspective of the current thread.
2861 @cindex @code{New} @var{systag} message
2862 @cindex thread identifier (system)
2863 @c FIXME-implementors!! It would be more helpful if the [New...] message
2864 @c included GDB's numeric thread handle, so you could just go to that
2865 @c thread without first checking `info threads'.
2866 Whenever @value{GDBN} detects a new thread in your program, it displays
2867 the target system's identification for the thread with a message in the
2868 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2869 whose form varies depending on the particular system. For example, on
2870 @sc{gnu}/Linux, you might see
2873 [New Thread 0x41e02940 (LWP 25582)]
2877 when @value{GDBN} notices a new thread. In contrast, on other systems,
2878 the @var{systag} is simply something like @samp{process 368}, with no
2881 @c FIXME!! (1) Does the [New...] message appear even for the very first
2882 @c thread of a program, or does it only appear for the
2883 @c second---i.e.@: when it becomes obvious we have a multithread
2885 @c (2) *Is* there necessarily a first thread always? Or do some
2886 @c multithread systems permit starting a program with multiple
2887 @c threads ab initio?
2889 @anchor{thread numbers}
2890 @cindex thread number, per inferior
2891 @cindex thread identifier (GDB)
2892 For debugging purposes, @value{GDBN} associates its own thread number
2893 ---always a single integer---with each thread of an inferior. This
2894 number is unique between all threads of an inferior, but not unique
2895 between threads of different inferiors.
2897 @cindex qualified thread ID
2898 You can refer to a given thread in an inferior using the qualified
2899 @var{inferior-num}.@var{thread-num} syntax, also known as
2900 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2901 number and @var{thread-num} being the thread number of the given
2902 inferior. For example, thread @code{2.3} refers to thread number 3 of
2903 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2904 then @value{GDBN} infers you're referring to a thread of the current
2907 Until you create a second inferior, @value{GDBN} does not show the
2908 @var{inferior-num} part of thread IDs, even though you can always use
2909 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2910 of inferior 1, the initial inferior.
2912 @anchor{thread ID lists}
2913 @cindex thread ID lists
2914 Some commands accept a space-separated @dfn{thread ID list} as
2915 argument. A list element can be:
2919 A thread ID as shown in the first field of the @samp{info threads}
2920 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2924 A range of thread numbers, again with or without an inferior
2925 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2926 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2929 All threads of an inferior, specified with a star wildcard, with or
2930 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2931 @samp{1.*}) or @code{*}. The former refers to all threads of the
2932 given inferior, and the latter form without an inferior qualifier
2933 refers to all threads of the current inferior.
2937 For example, if the current inferior is 1, and inferior 7 has one
2938 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2939 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2940 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2941 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2945 @anchor{global thread numbers}
2946 @cindex global thread number
2947 @cindex global thread identifier (GDB)
2948 In addition to a @emph{per-inferior} number, each thread is also
2949 assigned a unique @emph{global} number, also known as @dfn{global
2950 thread ID}, a single integer. Unlike the thread number component of
2951 the thread ID, no two threads have the same global ID, even when
2952 you're debugging multiple inferiors.
2954 From @value{GDBN}'s perspective, a process always has at least one
2955 thread. In other words, @value{GDBN} assigns a thread number to the
2956 program's ``main thread'' even if the program is not multi-threaded.
2958 @vindex $_thread@r{, convenience variable}
2959 @vindex $_gthread@r{, convenience variable}
2960 The debugger convenience variables @samp{$_thread} and
2961 @samp{$_gthread} contain, respectively, the per-inferior thread number
2962 and the global thread number of the current thread. You may find this
2963 useful in writing breakpoint conditional expressions, command scripts,
2964 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2965 general information on convenience variables.
2967 If @value{GDBN} detects the program is multi-threaded, it augments the
2968 usual message about stopping at a breakpoint with the ID and name of
2969 the thread that hit the breakpoint.
2972 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2975 Likewise when the program receives a signal:
2978 Thread 1 "main" received signal SIGINT, Interrupt.
2982 @kindex info threads
2983 @item info threads @r{[}@var{thread-id-list}@r{]}
2985 Display information about one or more threads. With no arguments
2986 displays information about all threads. You can specify the list of
2987 threads that you want to display using the thread ID list syntax
2988 (@pxref{thread ID lists}).
2990 @value{GDBN} displays for each thread (in this order):
2994 the per-inferior thread number assigned by @value{GDBN}
2997 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
2998 option was specified
3001 the target system's thread identifier (@var{systag})
3004 the thread's name, if one is known. A thread can either be named by
3005 the user (see @code{thread name}, below), or, in some cases, by the
3009 the current stack frame summary for that thread
3013 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3014 indicates the current thread.
3018 @c end table here to get a little more width for example
3021 (@value{GDBP}) info threads
3023 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3024 2 process 35 thread 23 0x34e5 in sigpause ()
3025 3 process 35 thread 27 0x34e5 in sigpause ()
3029 If you're debugging multiple inferiors, @value{GDBN} displays thread
3030 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3031 Otherwise, only @var{thread-num} is shown.
3033 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3034 indicating each thread's global thread ID:
3037 (@value{GDBP}) info threads
3038 Id GId Target Id Frame
3039 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3040 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3041 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3042 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3045 On Solaris, you can display more information about user threads with a
3046 Solaris-specific command:
3049 @item maint info sol-threads
3050 @kindex maint info sol-threads
3051 @cindex thread info (Solaris)
3052 Display info on Solaris user threads.
3056 @kindex thread @var{thread-id}
3057 @item thread @var{thread-id}
3058 Make thread ID @var{thread-id} the current thread. The command
3059 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3060 the first field of the @samp{info threads} display, with or without an
3061 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3063 @value{GDBN} responds by displaying the system identifier of the
3064 thread you selected, and its current stack frame summary:
3067 (@value{GDBP}) thread 2
3068 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3069 #0 some_function (ignore=0x0) at example.c:8
3070 8 printf ("hello\n");
3074 As with the @samp{[New @dots{}]} message, the form of the text after
3075 @samp{Switching to} depends on your system's conventions for identifying
3078 @kindex thread apply
3079 @cindex apply command to several threads
3080 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3081 The @code{thread apply} command allows you to apply the named
3082 @var{command} to one or more threads. Specify the threads that you
3083 want affected using the thread ID list syntax (@pxref{thread ID
3084 lists}), or specify @code{all} to apply to all threads. To apply a
3085 command to all threads in descending order, type @kbd{thread apply all
3086 @var{command}}. To apply a command to all threads in ascending order,
3087 type @kbd{thread apply all -ascending @var{command}}.
3091 @cindex name a thread
3092 @item thread name [@var{name}]
3093 This command assigns a name to the current thread. If no argument is
3094 given, any existing user-specified name is removed. The thread name
3095 appears in the @samp{info threads} display.
3097 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3098 determine the name of the thread as given by the OS. On these
3099 systems, a name specified with @samp{thread name} will override the
3100 system-give name, and removing the user-specified name will cause
3101 @value{GDBN} to once again display the system-specified name.
3104 @cindex search for a thread
3105 @item thread find [@var{regexp}]
3106 Search for and display thread ids whose name or @var{systag}
3107 matches the supplied regular expression.
3109 As well as being the complement to the @samp{thread name} command,
3110 this command also allows you to identify a thread by its target
3111 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3115 (@value{GDBN}) thread find 26688
3116 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3117 (@value{GDBN}) info thread 4
3119 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3122 @kindex set print thread-events
3123 @cindex print messages on thread start and exit
3124 @item set print thread-events
3125 @itemx set print thread-events on
3126 @itemx set print thread-events off
3127 The @code{set print thread-events} command allows you to enable or
3128 disable printing of messages when @value{GDBN} notices that new threads have
3129 started or that threads have exited. By default, these messages will
3130 be printed if detection of these events is supported by the target.
3131 Note that these messages cannot be disabled on all targets.
3133 @kindex show print thread-events
3134 @item show print thread-events
3135 Show whether messages will be printed when @value{GDBN} detects that threads
3136 have started and exited.
3139 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3140 more information about how @value{GDBN} behaves when you stop and start
3141 programs with multiple threads.
3143 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3144 watchpoints in programs with multiple threads.
3146 @anchor{set libthread-db-search-path}
3148 @kindex set libthread-db-search-path
3149 @cindex search path for @code{libthread_db}
3150 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3151 If this variable is set, @var{path} is a colon-separated list of
3152 directories @value{GDBN} will use to search for @code{libthread_db}.
3153 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3154 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3155 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3158 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3159 @code{libthread_db} library to obtain information about threads in the
3160 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3161 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3162 specific thread debugging library loading is enabled
3163 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3165 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3166 refers to the default system directories that are
3167 normally searched for loading shared libraries. The @samp{$sdir} entry
3168 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3169 (@pxref{libthread_db.so.1 file}).
3171 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3172 refers to the directory from which @code{libpthread}
3173 was loaded in the inferior process.
3175 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3176 @value{GDBN} attempts to initialize it with the current inferior process.
3177 If this initialization fails (which could happen because of a version
3178 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3179 will unload @code{libthread_db}, and continue with the next directory.
3180 If none of @code{libthread_db} libraries initialize successfully,
3181 @value{GDBN} will issue a warning and thread debugging will be disabled.
3183 Setting @code{libthread-db-search-path} is currently implemented
3184 only on some platforms.
3186 @kindex show libthread-db-search-path
3187 @item show libthread-db-search-path
3188 Display current libthread_db search path.
3190 @kindex set debug libthread-db
3191 @kindex show debug libthread-db
3192 @cindex debugging @code{libthread_db}
3193 @item set debug libthread-db
3194 @itemx show debug libthread-db
3195 Turns on or off display of @code{libthread_db}-related events.
3196 Use @code{1} to enable, @code{0} to disable.
3200 @section Debugging Forks
3202 @cindex fork, debugging programs which call
3203 @cindex multiple processes
3204 @cindex processes, multiple
3205 On most systems, @value{GDBN} has no special support for debugging
3206 programs which create additional processes using the @code{fork}
3207 function. When a program forks, @value{GDBN} will continue to debug the
3208 parent process and the child process will run unimpeded. If you have
3209 set a breakpoint in any code which the child then executes, the child
3210 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3211 will cause it to terminate.
3213 However, if you want to debug the child process there is a workaround
3214 which isn't too painful. Put a call to @code{sleep} in the code which
3215 the child process executes after the fork. It may be useful to sleep
3216 only if a certain environment variable is set, or a certain file exists,
3217 so that the delay need not occur when you don't want to run @value{GDBN}
3218 on the child. While the child is sleeping, use the @code{ps} program to
3219 get its process ID. Then tell @value{GDBN} (a new invocation of
3220 @value{GDBN} if you are also debugging the parent process) to attach to
3221 the child process (@pxref{Attach}). From that point on you can debug
3222 the child process just like any other process which you attached to.
3224 On some systems, @value{GDBN} provides support for debugging programs
3225 that create additional processes using the @code{fork} or @code{vfork}
3226 functions. On @sc{gnu}/Linux platforms, this feature is supported
3227 with kernel version 2.5.46 and later.
3229 The fork debugging commands are supported in native mode and when
3230 connected to @code{gdbserver} in either @code{target remote} mode or
3231 @code{target extended-remote} mode.
3233 By default, when a program forks, @value{GDBN} will continue to debug
3234 the parent process and the child process will run unimpeded.
3236 If you want to follow the child process instead of the parent process,
3237 use the command @w{@code{set follow-fork-mode}}.
3240 @kindex set follow-fork-mode
3241 @item set follow-fork-mode @var{mode}
3242 Set the debugger response to a program call of @code{fork} or
3243 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3244 process. The @var{mode} argument can be:
3248 The original process is debugged after a fork. The child process runs
3249 unimpeded. This is the default.
3252 The new process is debugged after a fork. The parent process runs
3257 @kindex show follow-fork-mode
3258 @item show follow-fork-mode
3259 Display the current debugger response to a @code{fork} or @code{vfork} call.
3262 @cindex debugging multiple processes
3263 On Linux, if you want to debug both the parent and child processes, use the
3264 command @w{@code{set detach-on-fork}}.
3267 @kindex set detach-on-fork
3268 @item set detach-on-fork @var{mode}
3269 Tells gdb whether to detach one of the processes after a fork, or
3270 retain debugger control over them both.
3274 The child process (or parent process, depending on the value of
3275 @code{follow-fork-mode}) will be detached and allowed to run
3276 independently. This is the default.
3279 Both processes will be held under the control of @value{GDBN}.
3280 One process (child or parent, depending on the value of
3281 @code{follow-fork-mode}) is debugged as usual, while the other
3286 @kindex show detach-on-fork
3287 @item show detach-on-fork
3288 Show whether detach-on-fork mode is on/off.
3291 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3292 will retain control of all forked processes (including nested forks).
3293 You can list the forked processes under the control of @value{GDBN} by
3294 using the @w{@code{info inferiors}} command, and switch from one fork
3295 to another by using the @code{inferior} command (@pxref{Inferiors and
3296 Programs, ,Debugging Multiple Inferiors and Programs}).
3298 To quit debugging one of the forked processes, you can either detach
3299 from it by using the @w{@code{detach inferiors}} command (allowing it
3300 to run independently), or kill it using the @w{@code{kill inferiors}}
3301 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3304 If you ask to debug a child process and a @code{vfork} is followed by an
3305 @code{exec}, @value{GDBN} executes the new target up to the first
3306 breakpoint in the new target. If you have a breakpoint set on
3307 @code{main} in your original program, the breakpoint will also be set on
3308 the child process's @code{main}.
3310 On some systems, when a child process is spawned by @code{vfork}, you
3311 cannot debug the child or parent until an @code{exec} call completes.
3313 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3314 call executes, the new target restarts. To restart the parent
3315 process, use the @code{file} command with the parent executable name
3316 as its argument. By default, after an @code{exec} call executes,
3317 @value{GDBN} discards the symbols of the previous executable image.
3318 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3322 @kindex set follow-exec-mode
3323 @item set follow-exec-mode @var{mode}
3325 Set debugger response to a program call of @code{exec}. An
3326 @code{exec} call replaces the program image of a process.
3328 @code{follow-exec-mode} can be:
3332 @value{GDBN} creates a new inferior and rebinds the process to this
3333 new inferior. The program the process was running before the
3334 @code{exec} call can be restarted afterwards by restarting the
3340 (@value{GDBP}) info inferiors
3342 Id Description Executable
3345 process 12020 is executing new program: prog2
3346 Program exited normally.
3347 (@value{GDBP}) info inferiors
3348 Id Description Executable
3354 @value{GDBN} keeps the process bound to the same inferior. The new
3355 executable image replaces the previous executable loaded in the
3356 inferior. Restarting the inferior after the @code{exec} call, with
3357 e.g., the @code{run} command, restarts the executable the process was
3358 running after the @code{exec} call. This is the default mode.
3363 (@value{GDBP}) info inferiors
3364 Id Description Executable
3367 process 12020 is executing new program: prog2
3368 Program exited normally.
3369 (@value{GDBP}) info inferiors
3370 Id Description Executable
3377 @code{follow-exec-mode} is supported in native mode and
3378 @code{target extended-remote} mode.
3380 You can use the @code{catch} command to make @value{GDBN} stop whenever
3381 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3382 Catchpoints, ,Setting Catchpoints}.
3384 @node Checkpoint/Restart
3385 @section Setting a @emph{Bookmark} to Return to Later
3390 @cindex snapshot of a process
3391 @cindex rewind program state
3393 On certain operating systems@footnote{Currently, only
3394 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3395 program's state, called a @dfn{checkpoint}, and come back to it
3398 Returning to a checkpoint effectively undoes everything that has
3399 happened in the program since the @code{checkpoint} was saved. This
3400 includes changes in memory, registers, and even (within some limits)
3401 system state. Effectively, it is like going back in time to the
3402 moment when the checkpoint was saved.
3404 Thus, if you're stepping thru a program and you think you're
3405 getting close to the point where things go wrong, you can save
3406 a checkpoint. Then, if you accidentally go too far and miss
3407 the critical statement, instead of having to restart your program
3408 from the beginning, you can just go back to the checkpoint and
3409 start again from there.
3411 This can be especially useful if it takes a lot of time or
3412 steps to reach the point where you think the bug occurs.
3414 To use the @code{checkpoint}/@code{restart} method of debugging:
3419 Save a snapshot of the debugged program's current execution state.
3420 The @code{checkpoint} command takes no arguments, but each checkpoint
3421 is assigned a small integer id, similar to a breakpoint id.
3423 @kindex info checkpoints
3424 @item info checkpoints
3425 List the checkpoints that have been saved in the current debugging
3426 session. For each checkpoint, the following information will be
3433 @item Source line, or label
3436 @kindex restart @var{checkpoint-id}
3437 @item restart @var{checkpoint-id}
3438 Restore the program state that was saved as checkpoint number
3439 @var{checkpoint-id}. All program variables, registers, stack frames
3440 etc.@: will be returned to the values that they had when the checkpoint
3441 was saved. In essence, gdb will ``wind back the clock'' to the point
3442 in time when the checkpoint was saved.
3444 Note that breakpoints, @value{GDBN} variables, command history etc.
3445 are not affected by restoring a checkpoint. In general, a checkpoint
3446 only restores things that reside in the program being debugged, not in
3449 @kindex delete checkpoint @var{checkpoint-id}
3450 @item delete checkpoint @var{checkpoint-id}
3451 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3455 Returning to a previously saved checkpoint will restore the user state
3456 of the program being debugged, plus a significant subset of the system
3457 (OS) state, including file pointers. It won't ``un-write'' data from
3458 a file, but it will rewind the file pointer to the previous location,
3459 so that the previously written data can be overwritten. For files
3460 opened in read mode, the pointer will also be restored so that the
3461 previously read data can be read again.
3463 Of course, characters that have been sent to a printer (or other
3464 external device) cannot be ``snatched back'', and characters received
3465 from eg.@: a serial device can be removed from internal program buffers,
3466 but they cannot be ``pushed back'' into the serial pipeline, ready to
3467 be received again. Similarly, the actual contents of files that have
3468 been changed cannot be restored (at this time).
3470 However, within those constraints, you actually can ``rewind'' your
3471 program to a previously saved point in time, and begin debugging it
3472 again --- and you can change the course of events so as to debug a
3473 different execution path this time.
3475 @cindex checkpoints and process id
3476 Finally, there is one bit of internal program state that will be
3477 different when you return to a checkpoint --- the program's process
3478 id. Each checkpoint will have a unique process id (or @var{pid}),
3479 and each will be different from the program's original @var{pid}.
3480 If your program has saved a local copy of its process id, this could
3481 potentially pose a problem.
3483 @subsection A Non-obvious Benefit of Using Checkpoints
3485 On some systems such as @sc{gnu}/Linux, address space randomization
3486 is performed on new processes for security reasons. This makes it
3487 difficult or impossible to set a breakpoint, or watchpoint, on an
3488 absolute address if you have to restart the program, since the
3489 absolute location of a symbol will change from one execution to the
3492 A checkpoint, however, is an @emph{identical} copy of a process.
3493 Therefore if you create a checkpoint at (eg.@:) the start of main,
3494 and simply return to that checkpoint instead of restarting the
3495 process, you can avoid the effects of address randomization and
3496 your symbols will all stay in the same place.
3499 @chapter Stopping and Continuing
3501 The principal purposes of using a debugger are so that you can stop your
3502 program before it terminates; or so that, if your program runs into
3503 trouble, you can investigate and find out why.
3505 Inside @value{GDBN}, your program may stop for any of several reasons,
3506 such as a signal, a breakpoint, or reaching a new line after a
3507 @value{GDBN} command such as @code{step}. You may then examine and
3508 change variables, set new breakpoints or remove old ones, and then
3509 continue execution. Usually, the messages shown by @value{GDBN} provide
3510 ample explanation of the status of your program---but you can also
3511 explicitly request this information at any time.
3514 @kindex info program
3516 Display information about the status of your program: whether it is
3517 running or not, what process it is, and why it stopped.
3521 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3522 * Continuing and Stepping:: Resuming execution
3523 * Skipping Over Functions and Files::
3524 Skipping over functions and files
3526 * Thread Stops:: Stopping and starting multi-thread programs
3530 @section Breakpoints, Watchpoints, and Catchpoints
3533 A @dfn{breakpoint} makes your program stop whenever a certain point in
3534 the program is reached. For each breakpoint, you can add conditions to
3535 control in finer detail whether your program stops. You can set
3536 breakpoints with the @code{break} command and its variants (@pxref{Set
3537 Breaks, ,Setting Breakpoints}), to specify the place where your program
3538 should stop by line number, function name or exact address in the
3541 On some systems, you can set breakpoints in shared libraries before
3542 the executable is run.
3545 @cindex data breakpoints
3546 @cindex memory tracing
3547 @cindex breakpoint on memory address
3548 @cindex breakpoint on variable modification
3549 A @dfn{watchpoint} is a special breakpoint that stops your program
3550 when the value of an expression changes. The expression may be a value
3551 of a variable, or it could involve values of one or more variables
3552 combined by operators, such as @samp{a + b}. This is sometimes called
3553 @dfn{data breakpoints}. You must use a different command to set
3554 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3555 from that, you can manage a watchpoint like any other breakpoint: you
3556 enable, disable, and delete both breakpoints and watchpoints using the
3559 You can arrange to have values from your program displayed automatically
3560 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3564 @cindex breakpoint on events
3565 A @dfn{catchpoint} is another special breakpoint that stops your program
3566 when a certain kind of event occurs, such as the throwing of a C@t{++}
3567 exception or the loading of a library. As with watchpoints, you use a
3568 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3569 Catchpoints}), but aside from that, you can manage a catchpoint like any
3570 other breakpoint. (To stop when your program receives a signal, use the
3571 @code{handle} command; see @ref{Signals, ,Signals}.)
3573 @cindex breakpoint numbers
3574 @cindex numbers for breakpoints
3575 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3576 catchpoint when you create it; these numbers are successive integers
3577 starting with one. In many of the commands for controlling various
3578 features of breakpoints you use the breakpoint number to say which
3579 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3580 @dfn{disabled}; if disabled, it has no effect on your program until you
3583 @cindex breakpoint ranges
3584 @cindex ranges of breakpoints
3585 Some @value{GDBN} commands accept a range of breakpoints on which to
3586 operate. A breakpoint range is either a single breakpoint number, like
3587 @samp{5}, or two such numbers, in increasing order, separated by a
3588 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3589 all breakpoints in that range are operated on.
3592 * Set Breaks:: Setting breakpoints
3593 * Set Watchpoints:: Setting watchpoints
3594 * Set Catchpoints:: Setting catchpoints
3595 * Delete Breaks:: Deleting breakpoints
3596 * Disabling:: Disabling breakpoints
3597 * Conditions:: Break conditions
3598 * Break Commands:: Breakpoint command lists
3599 * Dynamic Printf:: Dynamic printf
3600 * Save Breakpoints:: How to save breakpoints in a file
3601 * Static Probe Points:: Listing static probe points
3602 * Error in Breakpoints:: ``Cannot insert breakpoints''
3603 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3607 @subsection Setting Breakpoints
3609 @c FIXME LMB what does GDB do if no code on line of breakpt?
3610 @c consider in particular declaration with/without initialization.
3612 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3615 @kindex b @r{(@code{break})}
3616 @vindex $bpnum@r{, convenience variable}
3617 @cindex latest breakpoint
3618 Breakpoints are set with the @code{break} command (abbreviated
3619 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3620 number of the breakpoint you've set most recently; see @ref{Convenience
3621 Vars,, Convenience Variables}, for a discussion of what you can do with
3622 convenience variables.
3625 @item break @var{location}
3626 Set a breakpoint at the given @var{location}, which can specify a
3627 function name, a line number, or an address of an instruction.
3628 (@xref{Specify Location}, for a list of all the possible ways to
3629 specify a @var{location}.) The breakpoint will stop your program just
3630 before it executes any of the code in the specified @var{location}.
3632 When using source languages that permit overloading of symbols, such as
3633 C@t{++}, a function name may refer to more than one possible place to break.
3634 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3637 It is also possible to insert a breakpoint that will stop the program
3638 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3639 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3642 When called without any arguments, @code{break} sets a breakpoint at
3643 the next instruction to be executed in the selected stack frame
3644 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3645 innermost, this makes your program stop as soon as control
3646 returns to that frame. This is similar to the effect of a
3647 @code{finish} command in the frame inside the selected frame---except
3648 that @code{finish} does not leave an active breakpoint. If you use
3649 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3650 the next time it reaches the current location; this may be useful
3653 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3654 least one instruction has been executed. If it did not do this, you
3655 would be unable to proceed past a breakpoint without first disabling the
3656 breakpoint. This rule applies whether or not the breakpoint already
3657 existed when your program stopped.
3659 @item break @dots{} if @var{cond}
3660 Set a breakpoint with condition @var{cond}; evaluate the expression
3661 @var{cond} each time the breakpoint is reached, and stop only if the
3662 value is nonzero---that is, if @var{cond} evaluates as true.
3663 @samp{@dots{}} stands for one of the possible arguments described
3664 above (or no argument) specifying where to break. @xref{Conditions,
3665 ,Break Conditions}, for more information on breakpoint conditions.
3668 @item tbreak @var{args}
3669 Set a breakpoint enabled only for one stop. The @var{args} are the
3670 same as for the @code{break} command, and the breakpoint is set in the same
3671 way, but the breakpoint is automatically deleted after the first time your
3672 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3675 @cindex hardware breakpoints
3676 @item hbreak @var{args}
3677 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3678 @code{break} command and the breakpoint is set in the same way, but the
3679 breakpoint requires hardware support and some target hardware may not
3680 have this support. The main purpose of this is EPROM/ROM code
3681 debugging, so you can set a breakpoint at an instruction without
3682 changing the instruction. This can be used with the new trap-generation
3683 provided by SPARClite DSU and most x86-based targets. These targets
3684 will generate traps when a program accesses some data or instruction
3685 address that is assigned to the debug registers. However the hardware
3686 breakpoint registers can take a limited number of breakpoints. For
3687 example, on the DSU, only two data breakpoints can be set at a time, and
3688 @value{GDBN} will reject this command if more than two are used. Delete
3689 or disable unused hardware breakpoints before setting new ones
3690 (@pxref{Disabling, ,Disabling Breakpoints}).
3691 @xref{Conditions, ,Break Conditions}.
3692 For remote targets, you can restrict the number of hardware
3693 breakpoints @value{GDBN} will use, see @ref{set remote
3694 hardware-breakpoint-limit}.
3697 @item thbreak @var{args}
3698 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3699 are the same as for the @code{hbreak} command and the breakpoint is set in
3700 the same way. However, like the @code{tbreak} command,
3701 the breakpoint is automatically deleted after the
3702 first time your program stops there. Also, like the @code{hbreak}
3703 command, the breakpoint requires hardware support and some target hardware
3704 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3705 See also @ref{Conditions, ,Break Conditions}.
3708 @cindex regular expression
3709 @cindex breakpoints at functions matching a regexp
3710 @cindex set breakpoints in many functions
3711 @item rbreak @var{regex}
3712 Set breakpoints on all functions matching the regular expression
3713 @var{regex}. This command sets an unconditional breakpoint on all
3714 matches, printing a list of all breakpoints it set. Once these
3715 breakpoints are set, they are treated just like the breakpoints set with
3716 the @code{break} command. You can delete them, disable them, or make
3717 them conditional the same way as any other breakpoint.
3719 The syntax of the regular expression is the standard one used with tools
3720 like @file{grep}. Note that this is different from the syntax used by
3721 shells, so for instance @code{foo*} matches all functions that include
3722 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3723 @code{.*} leading and trailing the regular expression you supply, so to
3724 match only functions that begin with @code{foo}, use @code{^foo}.
3726 @cindex non-member C@t{++} functions, set breakpoint in
3727 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3728 breakpoints on overloaded functions that are not members of any special
3731 @cindex set breakpoints on all functions
3732 The @code{rbreak} command can be used to set breakpoints in
3733 @strong{all} the functions in a program, like this:
3736 (@value{GDBP}) rbreak .
3739 @item rbreak @var{file}:@var{regex}
3740 If @code{rbreak} is called with a filename qualification, it limits
3741 the search for functions matching the given regular expression to the
3742 specified @var{file}. This can be used, for example, to set breakpoints on
3743 every function in a given file:
3746 (@value{GDBP}) rbreak file.c:.
3749 The colon separating the filename qualifier from the regex may
3750 optionally be surrounded by spaces.
3752 @kindex info breakpoints
3753 @cindex @code{$_} and @code{info breakpoints}
3754 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3755 @itemx info break @r{[}@var{n}@dots{}@r{]}
3756 Print a table of all breakpoints, watchpoints, and catchpoints set and
3757 not deleted. Optional argument @var{n} means print information only
3758 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3759 For each breakpoint, following columns are printed:
3762 @item Breakpoint Numbers
3764 Breakpoint, watchpoint, or catchpoint.
3766 Whether the breakpoint is marked to be disabled or deleted when hit.
3767 @item Enabled or Disabled
3768 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3769 that are not enabled.
3771 Where the breakpoint is in your program, as a memory address. For a
3772 pending breakpoint whose address is not yet known, this field will
3773 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3774 library that has the symbol or line referred by breakpoint is loaded.
3775 See below for details. A breakpoint with several locations will
3776 have @samp{<MULTIPLE>} in this field---see below for details.
3778 Where the breakpoint is in the source for your program, as a file and
3779 line number. For a pending breakpoint, the original string passed to
3780 the breakpoint command will be listed as it cannot be resolved until
3781 the appropriate shared library is loaded in the future.
3785 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3786 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3787 @value{GDBN} on the host's side. If it is ``target'', then the condition
3788 is evaluated by the target. The @code{info break} command shows
3789 the condition on the line following the affected breakpoint, together with
3790 its condition evaluation mode in between parentheses.
3792 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3793 allowed to have a condition specified for it. The condition is not parsed for
3794 validity until a shared library is loaded that allows the pending
3795 breakpoint to resolve to a valid location.
3798 @code{info break} with a breakpoint
3799 number @var{n} as argument lists only that breakpoint. The
3800 convenience variable @code{$_} and the default examining-address for
3801 the @code{x} command are set to the address of the last breakpoint
3802 listed (@pxref{Memory, ,Examining Memory}).
3805 @code{info break} displays a count of the number of times the breakpoint
3806 has been hit. This is especially useful in conjunction with the
3807 @code{ignore} command. You can ignore a large number of breakpoint
3808 hits, look at the breakpoint info to see how many times the breakpoint
3809 was hit, and then run again, ignoring one less than that number. This
3810 will get you quickly to the last hit of that breakpoint.
3813 For a breakpoints with an enable count (xref) greater than 1,
3814 @code{info break} also displays that count.
3818 @value{GDBN} allows you to set any number of breakpoints at the same place in
3819 your program. There is nothing silly or meaningless about this. When
3820 the breakpoints are conditional, this is even useful
3821 (@pxref{Conditions, ,Break Conditions}).
3823 @cindex multiple locations, breakpoints
3824 @cindex breakpoints, multiple locations
3825 It is possible that a breakpoint corresponds to several locations
3826 in your program. Examples of this situation are:
3830 Multiple functions in the program may have the same name.
3833 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3834 instances of the function body, used in different cases.
3837 For a C@t{++} template function, a given line in the function can
3838 correspond to any number of instantiations.
3841 For an inlined function, a given source line can correspond to
3842 several places where that function is inlined.
3845 In all those cases, @value{GDBN} will insert a breakpoint at all
3846 the relevant locations.
3848 A breakpoint with multiple locations is displayed in the breakpoint
3849 table using several rows---one header row, followed by one row for
3850 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3851 address column. The rows for individual locations contain the actual
3852 addresses for locations, and show the functions to which those
3853 locations belong. The number column for a location is of the form
3854 @var{breakpoint-number}.@var{location-number}.
3859 Num Type Disp Enb Address What
3860 1 breakpoint keep y <MULTIPLE>
3862 breakpoint already hit 1 time
3863 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3864 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3867 Each location can be individually enabled or disabled by passing
3868 @var{breakpoint-number}.@var{location-number} as argument to the
3869 @code{enable} and @code{disable} commands. Note that you cannot
3870 delete the individual locations from the list, you can only delete the
3871 entire list of locations that belong to their parent breakpoint (with
3872 the @kbd{delete @var{num}} command, where @var{num} is the number of
3873 the parent breakpoint, 1 in the above example). Disabling or enabling
3874 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3875 that belong to that breakpoint.
3877 @cindex pending breakpoints
3878 It's quite common to have a breakpoint inside a shared library.
3879 Shared libraries can be loaded and unloaded explicitly,
3880 and possibly repeatedly, as the program is executed. To support
3881 this use case, @value{GDBN} updates breakpoint locations whenever
3882 any shared library is loaded or unloaded. Typically, you would
3883 set a breakpoint in a shared library at the beginning of your
3884 debugging session, when the library is not loaded, and when the
3885 symbols from the library are not available. When you try to set
3886 breakpoint, @value{GDBN} will ask you if you want to set
3887 a so called @dfn{pending breakpoint}---breakpoint whose address
3888 is not yet resolved.
3890 After the program is run, whenever a new shared library is loaded,
3891 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3892 shared library contains the symbol or line referred to by some
3893 pending breakpoint, that breakpoint is resolved and becomes an
3894 ordinary breakpoint. When a library is unloaded, all breakpoints
3895 that refer to its symbols or source lines become pending again.
3897 This logic works for breakpoints with multiple locations, too. For
3898 example, if you have a breakpoint in a C@t{++} template function, and
3899 a newly loaded shared library has an instantiation of that template,
3900 a new location is added to the list of locations for the breakpoint.
3902 Except for having unresolved address, pending breakpoints do not
3903 differ from regular breakpoints. You can set conditions or commands,
3904 enable and disable them and perform other breakpoint operations.
3906 @value{GDBN} provides some additional commands for controlling what
3907 happens when the @samp{break} command cannot resolve breakpoint
3908 address specification to an address:
3910 @kindex set breakpoint pending
3911 @kindex show breakpoint pending
3913 @item set breakpoint pending auto
3914 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3915 location, it queries you whether a pending breakpoint should be created.
3917 @item set breakpoint pending on
3918 This indicates that an unrecognized breakpoint location should automatically
3919 result in a pending breakpoint being created.
3921 @item set breakpoint pending off
3922 This indicates that pending breakpoints are not to be created. Any
3923 unrecognized breakpoint location results in an error. This setting does
3924 not affect any pending breakpoints previously created.
3926 @item show breakpoint pending
3927 Show the current behavior setting for creating pending breakpoints.
3930 The settings above only affect the @code{break} command and its
3931 variants. Once breakpoint is set, it will be automatically updated
3932 as shared libraries are loaded and unloaded.
3934 @cindex automatic hardware breakpoints
3935 For some targets, @value{GDBN} can automatically decide if hardware or
3936 software breakpoints should be used, depending on whether the
3937 breakpoint address is read-only or read-write. This applies to
3938 breakpoints set with the @code{break} command as well as to internal
3939 breakpoints set by commands like @code{next} and @code{finish}. For
3940 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3943 You can control this automatic behaviour with the following commands::
3945 @kindex set breakpoint auto-hw
3946 @kindex show breakpoint auto-hw
3948 @item set breakpoint auto-hw on
3949 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3950 will try to use the target memory map to decide if software or hardware
3951 breakpoint must be used.
3953 @item set breakpoint auto-hw off
3954 This indicates @value{GDBN} should not automatically select breakpoint
3955 type. If the target provides a memory map, @value{GDBN} will warn when
3956 trying to set software breakpoint at a read-only address.
3959 @value{GDBN} normally implements breakpoints by replacing the program code
3960 at the breakpoint address with a special instruction, which, when
3961 executed, given control to the debugger. By default, the program
3962 code is so modified only when the program is resumed. As soon as
3963 the program stops, @value{GDBN} restores the original instructions. This
3964 behaviour guards against leaving breakpoints inserted in the
3965 target should gdb abrubptly disconnect. However, with slow remote
3966 targets, inserting and removing breakpoint can reduce the performance.
3967 This behavior can be controlled with the following commands::
3969 @kindex set breakpoint always-inserted
3970 @kindex show breakpoint always-inserted
3972 @item set breakpoint always-inserted off
3973 All breakpoints, including newly added by the user, are inserted in
3974 the target only when the target is resumed. All breakpoints are
3975 removed from the target when it stops. This is the default mode.
3977 @item set breakpoint always-inserted on
3978 Causes all breakpoints to be inserted in the target at all times. If
3979 the user adds a new breakpoint, or changes an existing breakpoint, the
3980 breakpoints in the target are updated immediately. A breakpoint is
3981 removed from the target only when breakpoint itself is deleted.
3984 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3985 when a breakpoint breaks. If the condition is true, then the process being
3986 debugged stops, otherwise the process is resumed.
3988 If the target supports evaluating conditions on its end, @value{GDBN} may
3989 download the breakpoint, together with its conditions, to it.
3991 This feature can be controlled via the following commands:
3993 @kindex set breakpoint condition-evaluation
3994 @kindex show breakpoint condition-evaluation
3996 @item set breakpoint condition-evaluation host
3997 This option commands @value{GDBN} to evaluate the breakpoint
3998 conditions on the host's side. Unconditional breakpoints are sent to
3999 the target which in turn receives the triggers and reports them back to GDB
4000 for condition evaluation. This is the standard evaluation mode.
4002 @item set breakpoint condition-evaluation target
4003 This option commands @value{GDBN} to download breakpoint conditions
4004 to the target at the moment of their insertion. The target
4005 is responsible for evaluating the conditional expression and reporting
4006 breakpoint stop events back to @value{GDBN} whenever the condition
4007 is true. Due to limitations of target-side evaluation, some conditions
4008 cannot be evaluated there, e.g., conditions that depend on local data
4009 that is only known to the host. Examples include
4010 conditional expressions involving convenience variables, complex types
4011 that cannot be handled by the agent expression parser and expressions
4012 that are too long to be sent over to the target, specially when the
4013 target is a remote system. In these cases, the conditions will be
4014 evaluated by @value{GDBN}.
4016 @item set breakpoint condition-evaluation auto
4017 This is the default mode. If the target supports evaluating breakpoint
4018 conditions on its end, @value{GDBN} will download breakpoint conditions to
4019 the target (limitations mentioned previously apply). If the target does
4020 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4021 to evaluating all these conditions on the host's side.
4025 @cindex negative breakpoint numbers
4026 @cindex internal @value{GDBN} breakpoints
4027 @value{GDBN} itself sometimes sets breakpoints in your program for
4028 special purposes, such as proper handling of @code{longjmp} (in C
4029 programs). These internal breakpoints are assigned negative numbers,
4030 starting with @code{-1}; @samp{info breakpoints} does not display them.
4031 You can see these breakpoints with the @value{GDBN} maintenance command
4032 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4035 @node Set Watchpoints
4036 @subsection Setting Watchpoints
4038 @cindex setting watchpoints
4039 You can use a watchpoint to stop execution whenever the value of an
4040 expression changes, without having to predict a particular place where
4041 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4042 The expression may be as simple as the value of a single variable, or
4043 as complex as many variables combined by operators. Examples include:
4047 A reference to the value of a single variable.
4050 An address cast to an appropriate data type. For example,
4051 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4052 address (assuming an @code{int} occupies 4 bytes).
4055 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4056 expression can use any operators valid in the program's native
4057 language (@pxref{Languages}).
4060 You can set a watchpoint on an expression even if the expression can
4061 not be evaluated yet. For instance, you can set a watchpoint on
4062 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4063 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4064 the expression produces a valid value. If the expression becomes
4065 valid in some other way than changing a variable (e.g.@: if the memory
4066 pointed to by @samp{*global_ptr} becomes readable as the result of a
4067 @code{malloc} call), @value{GDBN} may not stop until the next time
4068 the expression changes.
4070 @cindex software watchpoints
4071 @cindex hardware watchpoints
4072 Depending on your system, watchpoints may be implemented in software or
4073 hardware. @value{GDBN} does software watchpointing by single-stepping your
4074 program and testing the variable's value each time, which is hundreds of
4075 times slower than normal execution. (But this may still be worth it, to
4076 catch errors where you have no clue what part of your program is the
4079 On some systems, such as most PowerPC or x86-based targets,
4080 @value{GDBN} includes support for hardware watchpoints, which do not
4081 slow down the running of your program.
4085 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4086 Set a watchpoint for an expression. @value{GDBN} will break when the
4087 expression @var{expr} is written into by the program and its value
4088 changes. The simplest (and the most popular) use of this command is
4089 to watch the value of a single variable:
4092 (@value{GDBP}) watch foo
4095 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4096 argument, @value{GDBN} breaks only when the thread identified by
4097 @var{thread-id} changes the value of @var{expr}. If any other threads
4098 change the value of @var{expr}, @value{GDBN} will not break. Note
4099 that watchpoints restricted to a single thread in this way only work
4100 with Hardware Watchpoints.
4102 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4103 (see below). The @code{-location} argument tells @value{GDBN} to
4104 instead watch the memory referred to by @var{expr}. In this case,
4105 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4106 and watch the memory at that address. The type of the result is used
4107 to determine the size of the watched memory. If the expression's
4108 result does not have an address, then @value{GDBN} will print an
4111 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4112 of masked watchpoints, if the current architecture supports this
4113 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4114 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4115 to an address to watch. The mask specifies that some bits of an address
4116 (the bits which are reset in the mask) should be ignored when matching
4117 the address accessed by the inferior against the watchpoint address.
4118 Thus, a masked watchpoint watches many addresses simultaneously---those
4119 addresses whose unmasked bits are identical to the unmasked bits in the
4120 watchpoint address. The @code{mask} argument implies @code{-location}.
4124 (@value{GDBP}) watch foo mask 0xffff00ff
4125 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4129 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4130 Set a watchpoint that will break when the value of @var{expr} is read
4134 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4135 Set a watchpoint that will break when @var{expr} is either read from
4136 or written into by the program.
4138 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4139 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4140 This command prints a list of watchpoints, using the same format as
4141 @code{info break} (@pxref{Set Breaks}).
4144 If you watch for a change in a numerically entered address you need to
4145 dereference it, as the address itself is just a constant number which will
4146 never change. @value{GDBN} refuses to create a watchpoint that watches
4147 a never-changing value:
4150 (@value{GDBP}) watch 0x600850
4151 Cannot watch constant value 0x600850.
4152 (@value{GDBP}) watch *(int *) 0x600850
4153 Watchpoint 1: *(int *) 6293584
4156 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4157 watchpoints execute very quickly, and the debugger reports a change in
4158 value at the exact instruction where the change occurs. If @value{GDBN}
4159 cannot set a hardware watchpoint, it sets a software watchpoint, which
4160 executes more slowly and reports the change in value at the next
4161 @emph{statement}, not the instruction, after the change occurs.
4163 @cindex use only software watchpoints
4164 You can force @value{GDBN} to use only software watchpoints with the
4165 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4166 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4167 the underlying system supports them. (Note that hardware-assisted
4168 watchpoints that were set @emph{before} setting
4169 @code{can-use-hw-watchpoints} to zero will still use the hardware
4170 mechanism of watching expression values.)
4173 @item set can-use-hw-watchpoints
4174 @kindex set can-use-hw-watchpoints
4175 Set whether or not to use hardware watchpoints.
4177 @item show can-use-hw-watchpoints
4178 @kindex show can-use-hw-watchpoints
4179 Show the current mode of using hardware watchpoints.
4182 For remote targets, you can restrict the number of hardware
4183 watchpoints @value{GDBN} will use, see @ref{set remote
4184 hardware-breakpoint-limit}.
4186 When you issue the @code{watch} command, @value{GDBN} reports
4189 Hardware watchpoint @var{num}: @var{expr}
4193 if it was able to set a hardware watchpoint.
4195 Currently, the @code{awatch} and @code{rwatch} commands can only set
4196 hardware watchpoints, because accesses to data that don't change the
4197 value of the watched expression cannot be detected without examining
4198 every instruction as it is being executed, and @value{GDBN} does not do
4199 that currently. If @value{GDBN} finds that it is unable to set a
4200 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4201 will print a message like this:
4204 Expression cannot be implemented with read/access watchpoint.
4207 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4208 data type of the watched expression is wider than what a hardware
4209 watchpoint on the target machine can handle. For example, some systems
4210 can only watch regions that are up to 4 bytes wide; on such systems you
4211 cannot set hardware watchpoints for an expression that yields a
4212 double-precision floating-point number (which is typically 8 bytes
4213 wide). As a work-around, it might be possible to break the large region
4214 into a series of smaller ones and watch them with separate watchpoints.
4216 If you set too many hardware watchpoints, @value{GDBN} might be unable
4217 to insert all of them when you resume the execution of your program.
4218 Since the precise number of active watchpoints is unknown until such
4219 time as the program is about to be resumed, @value{GDBN} might not be
4220 able to warn you about this when you set the watchpoints, and the
4221 warning will be printed only when the program is resumed:
4224 Hardware watchpoint @var{num}: Could not insert watchpoint
4228 If this happens, delete or disable some of the watchpoints.
4230 Watching complex expressions that reference many variables can also
4231 exhaust the resources available for hardware-assisted watchpoints.
4232 That's because @value{GDBN} needs to watch every variable in the
4233 expression with separately allocated resources.
4235 If you call a function interactively using @code{print} or @code{call},
4236 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4237 kind of breakpoint or the call completes.
4239 @value{GDBN} automatically deletes watchpoints that watch local
4240 (automatic) variables, or expressions that involve such variables, when
4241 they go out of scope, that is, when the execution leaves the block in
4242 which these variables were defined. In particular, when the program
4243 being debugged terminates, @emph{all} local variables go out of scope,
4244 and so only watchpoints that watch global variables remain set. If you
4245 rerun the program, you will need to set all such watchpoints again. One
4246 way of doing that would be to set a code breakpoint at the entry to the
4247 @code{main} function and when it breaks, set all the watchpoints.
4249 @cindex watchpoints and threads
4250 @cindex threads and watchpoints
4251 In multi-threaded programs, watchpoints will detect changes to the
4252 watched expression from every thread.
4255 @emph{Warning:} In multi-threaded programs, software watchpoints
4256 have only limited usefulness. If @value{GDBN} creates a software
4257 watchpoint, it can only watch the value of an expression @emph{in a
4258 single thread}. If you are confident that the expression can only
4259 change due to the current thread's activity (and if you are also
4260 confident that no other thread can become current), then you can use
4261 software watchpoints as usual. However, @value{GDBN} may not notice
4262 when a non-current thread's activity changes the expression. (Hardware
4263 watchpoints, in contrast, watch an expression in all threads.)
4266 @xref{set remote hardware-watchpoint-limit}.
4268 @node Set Catchpoints
4269 @subsection Setting Catchpoints
4270 @cindex catchpoints, setting
4271 @cindex exception handlers
4272 @cindex event handling
4274 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4275 kinds of program events, such as C@t{++} exceptions or the loading of a
4276 shared library. Use the @code{catch} command to set a catchpoint.
4280 @item catch @var{event}
4281 Stop when @var{event} occurs. The @var{event} can be any of the following:
4284 @item throw @r{[}@var{regexp}@r{]}
4285 @itemx rethrow @r{[}@var{regexp}@r{]}
4286 @itemx catch @r{[}@var{regexp}@r{]}
4288 @kindex catch rethrow
4290 @cindex stop on C@t{++} exceptions
4291 The throwing, re-throwing, or catching of a C@t{++} exception.
4293 If @var{regexp} is given, then only exceptions whose type matches the
4294 regular expression will be caught.
4296 @vindex $_exception@r{, convenience variable}
4297 The convenience variable @code{$_exception} is available at an
4298 exception-related catchpoint, on some systems. This holds the
4299 exception being thrown.
4301 There are currently some limitations to C@t{++} exception handling in
4306 The support for these commands is system-dependent. Currently, only
4307 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4311 The regular expression feature and the @code{$_exception} convenience
4312 variable rely on the presence of some SDT probes in @code{libstdc++}.
4313 If these probes are not present, then these features cannot be used.
4314 These probes were first available in the GCC 4.8 release, but whether
4315 or not they are available in your GCC also depends on how it was
4319 The @code{$_exception} convenience variable is only valid at the
4320 instruction at which an exception-related catchpoint is set.
4323 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4324 location in the system library which implements runtime exception
4325 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4326 (@pxref{Selection}) to get to your code.
4329 If you call a function interactively, @value{GDBN} normally returns
4330 control to you when the function has finished executing. If the call
4331 raises an exception, however, the call may bypass the mechanism that
4332 returns control to you and cause your program either to abort or to
4333 simply continue running until it hits a breakpoint, catches a signal
4334 that @value{GDBN} is listening for, or exits. This is the case even if
4335 you set a catchpoint for the exception; catchpoints on exceptions are
4336 disabled within interactive calls. @xref{Calling}, for information on
4337 controlling this with @code{set unwind-on-terminating-exception}.
4340 You cannot raise an exception interactively.
4343 You cannot install an exception handler interactively.
4347 @kindex catch exception
4348 @cindex Ada exception catching
4349 @cindex catch Ada exceptions
4350 An Ada exception being raised. If an exception name is specified
4351 at the end of the command (eg @code{catch exception Program_Error}),
4352 the debugger will stop only when this specific exception is raised.
4353 Otherwise, the debugger stops execution when any Ada exception is raised.
4355 When inserting an exception catchpoint on a user-defined exception whose
4356 name is identical to one of the exceptions defined by the language, the
4357 fully qualified name must be used as the exception name. Otherwise,
4358 @value{GDBN} will assume that it should stop on the pre-defined exception
4359 rather than the user-defined one. For instance, assuming an exception
4360 called @code{Constraint_Error} is defined in package @code{Pck}, then
4361 the command to use to catch such exceptions is @kbd{catch exception
4362 Pck.Constraint_Error}.
4364 @item exception unhandled
4365 @kindex catch exception unhandled
4366 An exception that was raised but is not handled by the program.
4369 @kindex catch assert
4370 A failed Ada assertion.
4374 @cindex break on fork/exec
4375 A call to @code{exec}.
4378 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4379 @kindex catch syscall
4380 @cindex break on a system call.
4381 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4382 syscall is a mechanism for application programs to request a service
4383 from the operating system (OS) or one of the OS system services.
4384 @value{GDBN} can catch some or all of the syscalls issued by the
4385 debuggee, and show the related information for each syscall. If no
4386 argument is specified, calls to and returns from all system calls
4389 @var{name} can be any system call name that is valid for the
4390 underlying OS. Just what syscalls are valid depends on the OS. On
4391 GNU and Unix systems, you can find the full list of valid syscall
4392 names on @file{/usr/include/asm/unistd.h}.
4394 @c For MS-Windows, the syscall names and the corresponding numbers
4395 @c can be found, e.g., on this URL:
4396 @c http://www.metasploit.com/users/opcode/syscalls.html
4397 @c but we don't support Windows syscalls yet.
4399 Normally, @value{GDBN} knows in advance which syscalls are valid for
4400 each OS, so you can use the @value{GDBN} command-line completion
4401 facilities (@pxref{Completion,, command completion}) to list the
4404 You may also specify the system call numerically. A syscall's
4405 number is the value passed to the OS's syscall dispatcher to
4406 identify the requested service. When you specify the syscall by its
4407 name, @value{GDBN} uses its database of syscalls to convert the name
4408 into the corresponding numeric code, but using the number directly
4409 may be useful if @value{GDBN}'s database does not have the complete
4410 list of syscalls on your system (e.g., because @value{GDBN} lags
4411 behind the OS upgrades).
4413 The example below illustrates how this command works if you don't provide
4417 (@value{GDBP}) catch syscall
4418 Catchpoint 1 (syscall)
4420 Starting program: /tmp/catch-syscall
4422 Catchpoint 1 (call to syscall 'close'), \
4423 0xffffe424 in __kernel_vsyscall ()
4427 Catchpoint 1 (returned from syscall 'close'), \
4428 0xffffe424 in __kernel_vsyscall ()
4432 Here is an example of catching a system call by name:
4435 (@value{GDBP}) catch syscall chroot
4436 Catchpoint 1 (syscall 'chroot' [61])
4438 Starting program: /tmp/catch-syscall
4440 Catchpoint 1 (call to syscall 'chroot'), \
4441 0xffffe424 in __kernel_vsyscall ()
4445 Catchpoint 1 (returned from syscall 'chroot'), \
4446 0xffffe424 in __kernel_vsyscall ()
4450 An example of specifying a system call numerically. In the case
4451 below, the syscall number has a corresponding entry in the XML
4452 file, so @value{GDBN} finds its name and prints it:
4455 (@value{GDBP}) catch syscall 252
4456 Catchpoint 1 (syscall(s) 'exit_group')
4458 Starting program: /tmp/catch-syscall
4460 Catchpoint 1 (call to syscall 'exit_group'), \
4461 0xffffe424 in __kernel_vsyscall ()
4465 Program exited normally.
4469 However, there can be situations when there is no corresponding name
4470 in XML file for that syscall number. In this case, @value{GDBN} prints
4471 a warning message saying that it was not able to find the syscall name,
4472 but the catchpoint will be set anyway. See the example below:
4475 (@value{GDBP}) catch syscall 764
4476 warning: The number '764' does not represent a known syscall.
4477 Catchpoint 2 (syscall 764)
4481 If you configure @value{GDBN} using the @samp{--without-expat} option,
4482 it will not be able to display syscall names. Also, if your
4483 architecture does not have an XML file describing its system calls,
4484 you will not be able to see the syscall names. It is important to
4485 notice that these two features are used for accessing the syscall
4486 name database. In either case, you will see a warning like this:
4489 (@value{GDBP}) catch syscall
4490 warning: Could not open "syscalls/i386-linux.xml"
4491 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4492 GDB will not be able to display syscall names.
4493 Catchpoint 1 (syscall)
4497 Of course, the file name will change depending on your architecture and system.
4499 Still using the example above, you can also try to catch a syscall by its
4500 number. In this case, you would see something like:
4503 (@value{GDBP}) catch syscall 252
4504 Catchpoint 1 (syscall(s) 252)
4507 Again, in this case @value{GDBN} would not be able to display syscall's names.
4511 A call to @code{fork}.
4515 A call to @code{vfork}.
4517 @item load @r{[}regexp@r{]}
4518 @itemx unload @r{[}regexp@r{]}
4520 @kindex catch unload
4521 The loading or unloading of a shared library. If @var{regexp} is
4522 given, then the catchpoint will stop only if the regular expression
4523 matches one of the affected libraries.
4525 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4526 @kindex catch signal
4527 The delivery of a signal.
4529 With no arguments, this catchpoint will catch any signal that is not
4530 used internally by @value{GDBN}, specifically, all signals except
4531 @samp{SIGTRAP} and @samp{SIGINT}.
4533 With the argument @samp{all}, all signals, including those used by
4534 @value{GDBN}, will be caught. This argument cannot be used with other
4537 Otherwise, the arguments are a list of signal names as given to
4538 @code{handle} (@pxref{Signals}). Only signals specified in this list
4541 One reason that @code{catch signal} can be more useful than
4542 @code{handle} is that you can attach commands and conditions to the
4545 When a signal is caught by a catchpoint, the signal's @code{stop} and
4546 @code{print} settings, as specified by @code{handle}, are ignored.
4547 However, whether the signal is still delivered to the inferior depends
4548 on the @code{pass} setting; this can be changed in the catchpoint's
4553 @item tcatch @var{event}
4555 Set a catchpoint that is enabled only for one stop. The catchpoint is
4556 automatically deleted after the first time the event is caught.
4560 Use the @code{info break} command to list the current catchpoints.
4564 @subsection Deleting Breakpoints
4566 @cindex clearing breakpoints, watchpoints, catchpoints
4567 @cindex deleting breakpoints, watchpoints, catchpoints
4568 It is often necessary to eliminate a breakpoint, watchpoint, or
4569 catchpoint once it has done its job and you no longer want your program
4570 to stop there. This is called @dfn{deleting} the breakpoint. A
4571 breakpoint that has been deleted no longer exists; it is forgotten.
4573 With the @code{clear} command you can delete breakpoints according to
4574 where they are in your program. With the @code{delete} command you can
4575 delete individual breakpoints, watchpoints, or catchpoints by specifying
4576 their breakpoint numbers.
4578 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4579 automatically ignores breakpoints on the first instruction to be executed
4580 when you continue execution without changing the execution address.
4585 Delete any breakpoints at the next instruction to be executed in the
4586 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4587 the innermost frame is selected, this is a good way to delete a
4588 breakpoint where your program just stopped.
4590 @item clear @var{location}
4591 Delete any breakpoints set at the specified @var{location}.
4592 @xref{Specify Location}, for the various forms of @var{location}; the
4593 most useful ones are listed below:
4596 @item clear @var{function}
4597 @itemx clear @var{filename}:@var{function}
4598 Delete any breakpoints set at entry to the named @var{function}.
4600 @item clear @var{linenum}
4601 @itemx clear @var{filename}:@var{linenum}
4602 Delete any breakpoints set at or within the code of the specified
4603 @var{linenum} of the specified @var{filename}.
4606 @cindex delete breakpoints
4608 @kindex d @r{(@code{delete})}
4609 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4610 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4611 ranges specified as arguments. If no argument is specified, delete all
4612 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4613 confirm off}). You can abbreviate this command as @code{d}.
4617 @subsection Disabling Breakpoints
4619 @cindex enable/disable a breakpoint
4620 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4621 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4622 it had been deleted, but remembers the information on the breakpoint so
4623 that you can @dfn{enable} it again later.
4625 You disable and enable breakpoints, watchpoints, and catchpoints with
4626 the @code{enable} and @code{disable} commands, optionally specifying
4627 one or more breakpoint numbers as arguments. Use @code{info break} to
4628 print a list of all breakpoints, watchpoints, and catchpoints if you
4629 do not know which numbers to use.
4631 Disabling and enabling a breakpoint that has multiple locations
4632 affects all of its locations.
4634 A breakpoint, watchpoint, or catchpoint can have any of several
4635 different states of enablement:
4639 Enabled. The breakpoint stops your program. A breakpoint set
4640 with the @code{break} command starts out in this state.
4642 Disabled. The breakpoint has no effect on your program.
4644 Enabled once. The breakpoint stops your program, but then becomes
4647 Enabled for a count. The breakpoint stops your program for the next
4648 N times, then becomes disabled.
4650 Enabled for deletion. The breakpoint stops your program, but
4651 immediately after it does so it is deleted permanently. A breakpoint
4652 set with the @code{tbreak} command starts out in this state.
4655 You can use the following commands to enable or disable breakpoints,
4656 watchpoints, and catchpoints:
4660 @kindex dis @r{(@code{disable})}
4661 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4662 Disable the specified breakpoints---or all breakpoints, if none are
4663 listed. A disabled breakpoint has no effect but is not forgotten. All
4664 options such as ignore-counts, conditions and commands are remembered in
4665 case the breakpoint is enabled again later. You may abbreviate
4666 @code{disable} as @code{dis}.
4669 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4670 Enable the specified breakpoints (or all defined breakpoints). They
4671 become effective once again in stopping your program.
4673 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4674 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4675 of these breakpoints immediately after stopping your program.
4677 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4678 Enable the specified breakpoints temporarily. @value{GDBN} records
4679 @var{count} with each of the specified breakpoints, and decrements a
4680 breakpoint's count when it is hit. When any count reaches 0,
4681 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4682 count (@pxref{Conditions, ,Break Conditions}), that will be
4683 decremented to 0 before @var{count} is affected.
4685 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4686 Enable the specified breakpoints to work once, then die. @value{GDBN}
4687 deletes any of these breakpoints as soon as your program stops there.
4688 Breakpoints set by the @code{tbreak} command start out in this state.
4691 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4692 @c confusing: tbreak is also initially enabled.
4693 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4694 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4695 subsequently, they become disabled or enabled only when you use one of
4696 the commands above. (The command @code{until} can set and delete a
4697 breakpoint of its own, but it does not change the state of your other
4698 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4702 @subsection Break Conditions
4703 @cindex conditional breakpoints
4704 @cindex breakpoint conditions
4706 @c FIXME what is scope of break condition expr? Context where wanted?
4707 @c in particular for a watchpoint?
4708 The simplest sort of breakpoint breaks every time your program reaches a
4709 specified place. You can also specify a @dfn{condition} for a
4710 breakpoint. A condition is just a Boolean expression in your
4711 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4712 a condition evaluates the expression each time your program reaches it,
4713 and your program stops only if the condition is @emph{true}.
4715 This is the converse of using assertions for program validation; in that
4716 situation, you want to stop when the assertion is violated---that is,
4717 when the condition is false. In C, if you want to test an assertion expressed
4718 by the condition @var{assert}, you should set the condition
4719 @samp{! @var{assert}} on the appropriate breakpoint.
4721 Conditions are also accepted for watchpoints; you may not need them,
4722 since a watchpoint is inspecting the value of an expression anyhow---but
4723 it might be simpler, say, to just set a watchpoint on a variable name,
4724 and specify a condition that tests whether the new value is an interesting
4727 Break conditions can have side effects, and may even call functions in
4728 your program. This can be useful, for example, to activate functions
4729 that log program progress, or to use your own print functions to
4730 format special data structures. The effects are completely predictable
4731 unless there is another enabled breakpoint at the same address. (In
4732 that case, @value{GDBN} might see the other breakpoint first and stop your
4733 program without checking the condition of this one.) Note that
4734 breakpoint commands are usually more convenient and flexible than break
4736 purpose of performing side effects when a breakpoint is reached
4737 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4739 Breakpoint conditions can also be evaluated on the target's side if
4740 the target supports it. Instead of evaluating the conditions locally,
4741 @value{GDBN} encodes the expression into an agent expression
4742 (@pxref{Agent Expressions}) suitable for execution on the target,
4743 independently of @value{GDBN}. Global variables become raw memory
4744 locations, locals become stack accesses, and so forth.
4746 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4747 when its condition evaluates to true. This mechanism may provide faster
4748 response times depending on the performance characteristics of the target
4749 since it does not need to keep @value{GDBN} informed about
4750 every breakpoint trigger, even those with false conditions.
4752 Break conditions can be specified when a breakpoint is set, by using
4753 @samp{if} in the arguments to the @code{break} command. @xref{Set
4754 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4755 with the @code{condition} command.
4757 You can also use the @code{if} keyword with the @code{watch} command.
4758 The @code{catch} command does not recognize the @code{if} keyword;
4759 @code{condition} is the only way to impose a further condition on a
4764 @item condition @var{bnum} @var{expression}
4765 Specify @var{expression} as the break condition for breakpoint,
4766 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4767 breakpoint @var{bnum} stops your program only if the value of
4768 @var{expression} is true (nonzero, in C). When you use
4769 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4770 syntactic correctness, and to determine whether symbols in it have
4771 referents in the context of your breakpoint. If @var{expression} uses
4772 symbols not referenced in the context of the breakpoint, @value{GDBN}
4773 prints an error message:
4776 No symbol "foo" in current context.
4781 not actually evaluate @var{expression} at the time the @code{condition}
4782 command (or a command that sets a breakpoint with a condition, like
4783 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4785 @item condition @var{bnum}
4786 Remove the condition from breakpoint number @var{bnum}. It becomes
4787 an ordinary unconditional breakpoint.
4790 @cindex ignore count (of breakpoint)
4791 A special case of a breakpoint condition is to stop only when the
4792 breakpoint has been reached a certain number of times. This is so
4793 useful that there is a special way to do it, using the @dfn{ignore
4794 count} of the breakpoint. Every breakpoint has an ignore count, which
4795 is an integer. Most of the time, the ignore count is zero, and
4796 therefore has no effect. But if your program reaches a breakpoint whose
4797 ignore count is positive, then instead of stopping, it just decrements
4798 the ignore count by one and continues. As a result, if the ignore count
4799 value is @var{n}, the breakpoint does not stop the next @var{n} times
4800 your program reaches it.
4804 @item ignore @var{bnum} @var{count}
4805 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4806 The next @var{count} times the breakpoint is reached, your program's
4807 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4810 To make the breakpoint stop the next time it is reached, specify
4813 When you use @code{continue} to resume execution of your program from a
4814 breakpoint, you can specify an ignore count directly as an argument to
4815 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4816 Stepping,,Continuing and Stepping}.
4818 If a breakpoint has a positive ignore count and a condition, the
4819 condition is not checked. Once the ignore count reaches zero,
4820 @value{GDBN} resumes checking the condition.
4822 You could achieve the effect of the ignore count with a condition such
4823 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4824 is decremented each time. @xref{Convenience Vars, ,Convenience
4828 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4831 @node Break Commands
4832 @subsection Breakpoint Command Lists
4834 @cindex breakpoint commands
4835 You can give any breakpoint (or watchpoint or catchpoint) a series of
4836 commands to execute when your program stops due to that breakpoint. For
4837 example, you might want to print the values of certain expressions, or
4838 enable other breakpoints.
4842 @kindex end@r{ (breakpoint commands)}
4843 @item commands @r{[}@var{range}@dots{}@r{]}
4844 @itemx @dots{} @var{command-list} @dots{}
4846 Specify a list of commands for the given breakpoints. The commands
4847 themselves appear on the following lines. Type a line containing just
4848 @code{end} to terminate the commands.
4850 To remove all commands from a breakpoint, type @code{commands} and
4851 follow it immediately with @code{end}; that is, give no commands.
4853 With no argument, @code{commands} refers to the last breakpoint,
4854 watchpoint, or catchpoint set (not to the breakpoint most recently
4855 encountered). If the most recent breakpoints were set with a single
4856 command, then the @code{commands} will apply to all the breakpoints
4857 set by that command. This applies to breakpoints set by
4858 @code{rbreak}, and also applies when a single @code{break} command
4859 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4863 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4864 disabled within a @var{command-list}.
4866 You can use breakpoint commands to start your program up again. Simply
4867 use the @code{continue} command, or @code{step}, or any other command
4868 that resumes execution.
4870 Any other commands in the command list, after a command that resumes
4871 execution, are ignored. This is because any time you resume execution
4872 (even with a simple @code{next} or @code{step}), you may encounter
4873 another breakpoint---which could have its own command list, leading to
4874 ambiguities about which list to execute.
4877 If the first command you specify in a command list is @code{silent}, the
4878 usual message about stopping at a breakpoint is not printed. This may
4879 be desirable for breakpoints that are to print a specific message and
4880 then continue. If none of the remaining commands print anything, you
4881 see no sign that the breakpoint was reached. @code{silent} is
4882 meaningful only at the beginning of a breakpoint command list.
4884 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4885 print precisely controlled output, and are often useful in silent
4886 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4888 For example, here is how you could use breakpoint commands to print the
4889 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4895 printf "x is %d\n",x
4900 One application for breakpoint commands is to compensate for one bug so
4901 you can test for another. Put a breakpoint just after the erroneous line
4902 of code, give it a condition to detect the case in which something
4903 erroneous has been done, and give it commands to assign correct values
4904 to any variables that need them. End with the @code{continue} command
4905 so that your program does not stop, and start with the @code{silent}
4906 command so that no output is produced. Here is an example:
4917 @node Dynamic Printf
4918 @subsection Dynamic Printf
4920 @cindex dynamic printf
4922 The dynamic printf command @code{dprintf} combines a breakpoint with
4923 formatted printing of your program's data to give you the effect of
4924 inserting @code{printf} calls into your program on-the-fly, without
4925 having to recompile it.
4927 In its most basic form, the output goes to the GDB console. However,
4928 you can set the variable @code{dprintf-style} for alternate handling.
4929 For instance, you can ask to format the output by calling your
4930 program's @code{printf} function. This has the advantage that the
4931 characters go to the program's output device, so they can recorded in
4932 redirects to files and so forth.
4934 If you are doing remote debugging with a stub or agent, you can also
4935 ask to have the printf handled by the remote agent. In addition to
4936 ensuring that the output goes to the remote program's device along
4937 with any other output the program might produce, you can also ask that
4938 the dprintf remain active even after disconnecting from the remote
4939 target. Using the stub/agent is also more efficient, as it can do
4940 everything without needing to communicate with @value{GDBN}.
4944 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4945 Whenever execution reaches @var{location}, print the values of one or
4946 more @var{expressions} under the control of the string @var{template}.
4947 To print several values, separate them with commas.
4949 @item set dprintf-style @var{style}
4950 Set the dprintf output to be handled in one of several different
4951 styles enumerated below. A change of style affects all existing
4952 dynamic printfs immediately. (If you need individual control over the
4953 print commands, simply define normal breakpoints with
4954 explicitly-supplied command lists.)
4957 @kindex dprintf-style gdb
4958 Handle the output using the @value{GDBN} @code{printf} command.
4961 @kindex dprintf-style call
4962 Handle the output by calling a function in your program (normally
4966 @kindex dprintf-style agent
4967 Have the remote debugging agent (such as @code{gdbserver}) handle
4968 the output itself. This style is only available for agents that
4969 support running commands on the target.
4971 @item set dprintf-function @var{function}
4972 Set the function to call if the dprintf style is @code{call}. By
4973 default its value is @code{printf}. You may set it to any expression.
4974 that @value{GDBN} can evaluate to a function, as per the @code{call}
4977 @item set dprintf-channel @var{channel}
4978 Set a ``channel'' for dprintf. If set to a non-empty value,
4979 @value{GDBN} will evaluate it as an expression and pass the result as
4980 a first argument to the @code{dprintf-function}, in the manner of
4981 @code{fprintf} and similar functions. Otherwise, the dprintf format
4982 string will be the first argument, in the manner of @code{printf}.
4984 As an example, if you wanted @code{dprintf} output to go to a logfile
4985 that is a standard I/O stream assigned to the variable @code{mylog},
4986 you could do the following:
4989 (gdb) set dprintf-style call
4990 (gdb) set dprintf-function fprintf
4991 (gdb) set dprintf-channel mylog
4992 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4993 Dprintf 1 at 0x123456: file main.c, line 25.
4995 1 dprintf keep y 0x00123456 in main at main.c:25
4996 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5001 Note that the @code{info break} displays the dynamic printf commands
5002 as normal breakpoint commands; you can thus easily see the effect of
5003 the variable settings.
5005 @item set disconnected-dprintf on
5006 @itemx set disconnected-dprintf off
5007 @kindex set disconnected-dprintf
5008 Choose whether @code{dprintf} commands should continue to run if
5009 @value{GDBN} has disconnected from the target. This only applies
5010 if the @code{dprintf-style} is @code{agent}.
5012 @item show disconnected-dprintf off
5013 @kindex show disconnected-dprintf
5014 Show the current choice for disconnected @code{dprintf}.
5018 @value{GDBN} does not check the validity of function and channel,
5019 relying on you to supply values that are meaningful for the contexts
5020 in which they are being used. For instance, the function and channel
5021 may be the values of local variables, but if that is the case, then
5022 all enabled dynamic prints must be at locations within the scope of
5023 those locals. If evaluation fails, @value{GDBN} will report an error.
5025 @node Save Breakpoints
5026 @subsection How to save breakpoints to a file
5028 To save breakpoint definitions to a file use the @w{@code{save
5029 breakpoints}} command.
5032 @kindex save breakpoints
5033 @cindex save breakpoints to a file for future sessions
5034 @item save breakpoints [@var{filename}]
5035 This command saves all current breakpoint definitions together with
5036 their commands and ignore counts, into a file @file{@var{filename}}
5037 suitable for use in a later debugging session. This includes all
5038 types of breakpoints (breakpoints, watchpoints, catchpoints,
5039 tracepoints). To read the saved breakpoint definitions, use the
5040 @code{source} command (@pxref{Command Files}). Note that watchpoints
5041 with expressions involving local variables may fail to be recreated
5042 because it may not be possible to access the context where the
5043 watchpoint is valid anymore. Because the saved breakpoint definitions
5044 are simply a sequence of @value{GDBN} commands that recreate the
5045 breakpoints, you can edit the file in your favorite editing program,
5046 and remove the breakpoint definitions you're not interested in, or
5047 that can no longer be recreated.
5050 @node Static Probe Points
5051 @subsection Static Probe Points
5053 @cindex static probe point, SystemTap
5054 @cindex static probe point, DTrace
5055 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5056 for Statically Defined Tracing, and the probes are designed to have a tiny
5057 runtime code and data footprint, and no dynamic relocations.
5059 Currently, the following types of probes are supported on
5060 ELF-compatible systems:
5064 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5065 @acronym{SDT} probes@footnote{See
5066 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5067 for more information on how to add @code{SystemTap} @acronym{SDT}
5068 probes in your applications.}. @code{SystemTap} probes are usable
5069 from assembly, C and C@t{++} languages@footnote{See
5070 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5071 for a good reference on how the @acronym{SDT} probes are implemented.}.
5073 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5074 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5078 @cindex semaphores on static probe points
5079 Some @code{SystemTap} probes have an associated semaphore variable;
5080 for instance, this happens automatically if you defined your probe
5081 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5082 @value{GDBN} will automatically enable it when you specify a
5083 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5084 breakpoint at a probe's location by some other method (e.g.,
5085 @code{break file:line}), then @value{GDBN} will not automatically set
5086 the semaphore. @code{DTrace} probes do not support semaphores.
5088 You can examine the available static static probes using @code{info
5089 probes}, with optional arguments:
5093 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5094 If given, @var{type} is either @code{stap} for listing
5095 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5096 probes. If omitted all probes are listed regardless of their types.
5098 If given, @var{provider} is a regular expression used to match against provider
5099 names when selecting which probes to list. If omitted, probes by all
5100 probes from all providers are listed.
5102 If given, @var{name} is a regular expression to match against probe names
5103 when selecting which probes to list. If omitted, probe names are not
5104 considered when deciding whether to display them.
5106 If given, @var{objfile} is a regular expression used to select which
5107 object files (executable or shared libraries) to examine. If not
5108 given, all object files are considered.
5110 @item info probes all
5111 List the available static probes, from all types.
5114 @cindex enabling and disabling probes
5115 Some probe points can be enabled and/or disabled. The effect of
5116 enabling or disabling a probe depends on the type of probe being
5117 handled. Some @code{DTrace} probes can be enabled or
5118 disabled, but @code{SystemTap} probes cannot be disabled.
5120 You can enable (or disable) one or more probes using the following
5121 commands, with optional arguments:
5124 @kindex enable probes
5125 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5126 If given, @var{provider} is a regular expression used to match against
5127 provider names when selecting which probes to enable. If omitted,
5128 all probes from all providers are enabled.
5130 If given, @var{name} is a regular expression to match against probe
5131 names when selecting which probes to enable. If omitted, probe names
5132 are not considered when deciding whether to enable them.
5134 If given, @var{objfile} is a regular expression used to select which
5135 object files (executable or shared libraries) to examine. If not
5136 given, all object files are considered.
5138 @kindex disable probes
5139 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5140 See the @code{enable probes} command above for a description of the
5141 optional arguments accepted by this command.
5144 @vindex $_probe_arg@r{, convenience variable}
5145 A probe may specify up to twelve arguments. These are available at the
5146 point at which the probe is defined---that is, when the current PC is
5147 at the probe's location. The arguments are available using the
5148 convenience variables (@pxref{Convenience Vars})
5149 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5150 probes each probe argument is an integer of the appropriate size;
5151 types are not preserved. In @code{DTrace} probes types are preserved
5152 provided that they are recognized as such by @value{GDBN}; otherwise
5153 the value of the probe argument will be a long integer. The
5154 convenience variable @code{$_probe_argc} holds the number of arguments
5155 at the current probe point.
5157 These variables are always available, but attempts to access them at
5158 any location other than a probe point will cause @value{GDBN} to give
5162 @c @ifclear BARETARGET
5163 @node Error in Breakpoints
5164 @subsection ``Cannot insert breakpoints''
5166 If you request too many active hardware-assisted breakpoints and
5167 watchpoints, you will see this error message:
5169 @c FIXME: the precise wording of this message may change; the relevant
5170 @c source change is not committed yet (Sep 3, 1999).
5172 Stopped; cannot insert breakpoints.
5173 You may have requested too many hardware breakpoints and watchpoints.
5177 This message is printed when you attempt to resume the program, since
5178 only then @value{GDBN} knows exactly how many hardware breakpoints and
5179 watchpoints it needs to insert.
5181 When this message is printed, you need to disable or remove some of the
5182 hardware-assisted breakpoints and watchpoints, and then continue.
5184 @node Breakpoint-related Warnings
5185 @subsection ``Breakpoint address adjusted...''
5186 @cindex breakpoint address adjusted
5188 Some processor architectures place constraints on the addresses at
5189 which breakpoints may be placed. For architectures thus constrained,
5190 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5191 with the constraints dictated by the architecture.
5193 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5194 a VLIW architecture in which a number of RISC-like instructions may be
5195 bundled together for parallel execution. The FR-V architecture
5196 constrains the location of a breakpoint instruction within such a
5197 bundle to the instruction with the lowest address. @value{GDBN}
5198 honors this constraint by adjusting a breakpoint's address to the
5199 first in the bundle.
5201 It is not uncommon for optimized code to have bundles which contain
5202 instructions from different source statements, thus it may happen that
5203 a breakpoint's address will be adjusted from one source statement to
5204 another. Since this adjustment may significantly alter @value{GDBN}'s
5205 breakpoint related behavior from what the user expects, a warning is
5206 printed when the breakpoint is first set and also when the breakpoint
5209 A warning like the one below is printed when setting a breakpoint
5210 that's been subject to address adjustment:
5213 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5216 Such warnings are printed both for user settable and @value{GDBN}'s
5217 internal breakpoints. If you see one of these warnings, you should
5218 verify that a breakpoint set at the adjusted address will have the
5219 desired affect. If not, the breakpoint in question may be removed and
5220 other breakpoints may be set which will have the desired behavior.
5221 E.g., it may be sufficient to place the breakpoint at a later
5222 instruction. A conditional breakpoint may also be useful in some
5223 cases to prevent the breakpoint from triggering too often.
5225 @value{GDBN} will also issue a warning when stopping at one of these
5226 adjusted breakpoints:
5229 warning: Breakpoint 1 address previously adjusted from 0x00010414
5233 When this warning is encountered, it may be too late to take remedial
5234 action except in cases where the breakpoint is hit earlier or more
5235 frequently than expected.
5237 @node Continuing and Stepping
5238 @section Continuing and Stepping
5242 @cindex resuming execution
5243 @dfn{Continuing} means resuming program execution until your program
5244 completes normally. In contrast, @dfn{stepping} means executing just
5245 one more ``step'' of your program, where ``step'' may mean either one
5246 line of source code, or one machine instruction (depending on what
5247 particular command you use). Either when continuing or when stepping,
5248 your program may stop even sooner, due to a breakpoint or a signal. (If
5249 it stops due to a signal, you may want to use @code{handle}, or use
5250 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5251 or you may step into the signal's handler (@pxref{stepping and signal
5256 @kindex c @r{(@code{continue})}
5257 @kindex fg @r{(resume foreground execution)}
5258 @item continue @r{[}@var{ignore-count}@r{]}
5259 @itemx c @r{[}@var{ignore-count}@r{]}
5260 @itemx fg @r{[}@var{ignore-count}@r{]}
5261 Resume program execution, at the address where your program last stopped;
5262 any breakpoints set at that address are bypassed. The optional argument
5263 @var{ignore-count} allows you to specify a further number of times to
5264 ignore a breakpoint at this location; its effect is like that of
5265 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5267 The argument @var{ignore-count} is meaningful only when your program
5268 stopped due to a breakpoint. At other times, the argument to
5269 @code{continue} is ignored.
5271 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5272 debugged program is deemed to be the foreground program) are provided
5273 purely for convenience, and have exactly the same behavior as
5277 To resume execution at a different place, you can use @code{return}
5278 (@pxref{Returning, ,Returning from a Function}) to go back to the
5279 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5280 Different Address}) to go to an arbitrary location in your program.
5282 A typical technique for using stepping is to set a breakpoint
5283 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5284 beginning of the function or the section of your program where a problem
5285 is believed to lie, run your program until it stops at that breakpoint,
5286 and then step through the suspect area, examining the variables that are
5287 interesting, until you see the problem happen.
5291 @kindex s @r{(@code{step})}
5293 Continue running your program until control reaches a different source
5294 line, then stop it and return control to @value{GDBN}. This command is
5295 abbreviated @code{s}.
5298 @c "without debugging information" is imprecise; actually "without line
5299 @c numbers in the debugging information". (gcc -g1 has debugging info but
5300 @c not line numbers). But it seems complex to try to make that
5301 @c distinction here.
5302 @emph{Warning:} If you use the @code{step} command while control is
5303 within a function that was compiled without debugging information,
5304 execution proceeds until control reaches a function that does have
5305 debugging information. Likewise, it will not step into a function which
5306 is compiled without debugging information. To step through functions
5307 without debugging information, use the @code{stepi} command, described
5311 The @code{step} command only stops at the first instruction of a source
5312 line. This prevents the multiple stops that could otherwise occur in
5313 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5314 to stop if a function that has debugging information is called within
5315 the line. In other words, @code{step} @emph{steps inside} any functions
5316 called within the line.
5318 Also, the @code{step} command only enters a function if there is line
5319 number information for the function. Otherwise it acts like the
5320 @code{next} command. This avoids problems when using @code{cc -gl}
5321 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5322 was any debugging information about the routine.
5324 @item step @var{count}
5325 Continue running as in @code{step}, but do so @var{count} times. If a
5326 breakpoint is reached, or a signal not related to stepping occurs before
5327 @var{count} steps, stepping stops right away.
5330 @kindex n @r{(@code{next})}
5331 @item next @r{[}@var{count}@r{]}
5332 Continue to the next source line in the current (innermost) stack frame.
5333 This is similar to @code{step}, but function calls that appear within
5334 the line of code are executed without stopping. Execution stops when
5335 control reaches a different line of code at the original stack level
5336 that was executing when you gave the @code{next} command. This command
5337 is abbreviated @code{n}.
5339 An argument @var{count} is a repeat count, as for @code{step}.
5342 @c FIX ME!! Do we delete this, or is there a way it fits in with
5343 @c the following paragraph? --- Vctoria
5345 @c @code{next} within a function that lacks debugging information acts like
5346 @c @code{step}, but any function calls appearing within the code of the
5347 @c function are executed without stopping.
5349 The @code{next} command only stops at the first instruction of a
5350 source line. This prevents multiple stops that could otherwise occur in
5351 @code{switch} statements, @code{for} loops, etc.
5353 @kindex set step-mode
5355 @cindex functions without line info, and stepping
5356 @cindex stepping into functions with no line info
5357 @itemx set step-mode on
5358 The @code{set step-mode on} command causes the @code{step} command to
5359 stop at the first instruction of a function which contains no debug line
5360 information rather than stepping over it.
5362 This is useful in cases where you may be interested in inspecting the
5363 machine instructions of a function which has no symbolic info and do not
5364 want @value{GDBN} to automatically skip over this function.
5366 @item set step-mode off
5367 Causes the @code{step} command to step over any functions which contains no
5368 debug information. This is the default.
5370 @item show step-mode
5371 Show whether @value{GDBN} will stop in or step over functions without
5372 source line debug information.
5375 @kindex fin @r{(@code{finish})}
5377 Continue running until just after function in the selected stack frame
5378 returns. Print the returned value (if any). This command can be
5379 abbreviated as @code{fin}.
5381 Contrast this with the @code{return} command (@pxref{Returning,
5382 ,Returning from a Function}).
5385 @kindex u @r{(@code{until})}
5386 @cindex run until specified location
5389 Continue running until a source line past the current line, in the
5390 current stack frame, is reached. This command is used to avoid single
5391 stepping through a loop more than once. It is like the @code{next}
5392 command, except that when @code{until} encounters a jump, it
5393 automatically continues execution until the program counter is greater
5394 than the address of the jump.
5396 This means that when you reach the end of a loop after single stepping
5397 though it, @code{until} makes your program continue execution until it
5398 exits the loop. In contrast, a @code{next} command at the end of a loop
5399 simply steps back to the beginning of the loop, which forces you to step
5400 through the next iteration.
5402 @code{until} always stops your program if it attempts to exit the current
5405 @code{until} may produce somewhat counterintuitive results if the order
5406 of machine code does not match the order of the source lines. For
5407 example, in the following excerpt from a debugging session, the @code{f}
5408 (@code{frame}) command shows that execution is stopped at line
5409 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5413 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5415 (@value{GDBP}) until
5416 195 for ( ; argc > 0; NEXTARG) @{
5419 This happened because, for execution efficiency, the compiler had
5420 generated code for the loop closure test at the end, rather than the
5421 start, of the loop---even though the test in a C @code{for}-loop is
5422 written before the body of the loop. The @code{until} command appeared
5423 to step back to the beginning of the loop when it advanced to this
5424 expression; however, it has not really gone to an earlier
5425 statement---not in terms of the actual machine code.
5427 @code{until} with no argument works by means of single
5428 instruction stepping, and hence is slower than @code{until} with an
5431 @item until @var{location}
5432 @itemx u @var{location}
5433 Continue running your program until either the specified @var{location} is
5434 reached, or the current stack frame returns. The location is any of
5435 the forms described in @ref{Specify Location}.
5436 This form of the command uses temporary breakpoints, and
5437 hence is quicker than @code{until} without an argument. The specified
5438 location is actually reached only if it is in the current frame. This
5439 implies that @code{until} can be used to skip over recursive function
5440 invocations. For instance in the code below, if the current location is
5441 line @code{96}, issuing @code{until 99} will execute the program up to
5442 line @code{99} in the same invocation of factorial, i.e., after the inner
5443 invocations have returned.
5446 94 int factorial (int value)
5448 96 if (value > 1) @{
5449 97 value *= factorial (value - 1);
5456 @kindex advance @var{location}
5457 @item advance @var{location}
5458 Continue running the program up to the given @var{location}. An argument is
5459 required, which should be of one of the forms described in
5460 @ref{Specify Location}.
5461 Execution will also stop upon exit from the current stack
5462 frame. This command is similar to @code{until}, but @code{advance} will
5463 not skip over recursive function calls, and the target location doesn't
5464 have to be in the same frame as the current one.
5468 @kindex si @r{(@code{stepi})}
5470 @itemx stepi @var{arg}
5472 Execute one machine instruction, then stop and return to the debugger.
5474 It is often useful to do @samp{display/i $pc} when stepping by machine
5475 instructions. This makes @value{GDBN} automatically display the next
5476 instruction to be executed, each time your program stops. @xref{Auto
5477 Display,, Automatic Display}.
5479 An argument is a repeat count, as in @code{step}.
5483 @kindex ni @r{(@code{nexti})}
5485 @itemx nexti @var{arg}
5487 Execute one machine instruction, but if it is a function call,
5488 proceed until the function returns.
5490 An argument is a repeat count, as in @code{next}.
5494 @anchor{range stepping}
5495 @cindex range stepping
5496 @cindex target-assisted range stepping
5497 By default, and if available, @value{GDBN} makes use of
5498 target-assisted @dfn{range stepping}. In other words, whenever you
5499 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5500 tells the target to step the corresponding range of instruction
5501 addresses instead of issuing multiple single-steps. This speeds up
5502 line stepping, particularly for remote targets. Ideally, there should
5503 be no reason you would want to turn range stepping off. However, it's
5504 possible that a bug in the debug info, a bug in the remote stub (for
5505 remote targets), or even a bug in @value{GDBN} could make line
5506 stepping behave incorrectly when target-assisted range stepping is
5507 enabled. You can use the following command to turn off range stepping
5511 @kindex set range-stepping
5512 @kindex show range-stepping
5513 @item set range-stepping
5514 @itemx show range-stepping
5515 Control whether range stepping is enabled.
5517 If @code{on}, and the target supports it, @value{GDBN} tells the
5518 target to step a range of addresses itself, instead of issuing
5519 multiple single-steps. If @code{off}, @value{GDBN} always issues
5520 single-steps, even if range stepping is supported by the target. The
5521 default is @code{on}.
5525 @node Skipping Over Functions and Files
5526 @section Skipping Over Functions and Files
5527 @cindex skipping over functions and files
5529 The program you are debugging may contain some functions which are
5530 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5531 skip a function, all functions in a file or a particular function in
5532 a particular file when stepping.
5534 For example, consider the following C function:
5545 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5546 are not interested in stepping through @code{boring}. If you run @code{step}
5547 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5548 step over both @code{foo} and @code{boring}!
5550 One solution is to @code{step} into @code{boring} and use the @code{finish}
5551 command to immediately exit it. But this can become tedious if @code{boring}
5552 is called from many places.
5554 A more flexible solution is to execute @kbd{skip boring}. This instructs
5555 @value{GDBN} never to step into @code{boring}. Now when you execute
5556 @code{step} at line 103, you'll step over @code{boring} and directly into
5559 Functions may be skipped by providing either a function name, linespec
5560 (@pxref{Specify Location}), regular expression that matches the function's
5561 name, file name or a @code{glob}-style pattern that matches the file name.
5563 On Posix systems the form of the regular expression is
5564 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5565 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5566 expression is whatever is provided by the @code{regcomp} function of
5567 the underlying system.
5568 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5569 description of @code{glob}-style patterns.
5573 @item skip @r{[}@var{options}@r{]}
5574 The basic form of the @code{skip} command takes zero or more options
5575 that specify what to skip.
5576 The @var{options} argument is any useful combination of the following:
5579 @item -file @var{file}
5580 @itemx -fi @var{file}
5581 Functions in @var{file} will be skipped over when stepping.
5583 @item -gfile @var{file-glob-pattern}
5584 @itemx -gfi @var{file-glob-pattern}
5585 @cindex skipping over files via glob-style patterns
5586 Functions in files matching @var{file-glob-pattern} will be skipped
5590 (gdb) skip -gfi utils/*.c
5593 @item -function @var{linespec}
5594 @itemx -fu @var{linespec}
5595 Functions named by @var{linespec} or the function containing the line
5596 named by @var{linespec} will be skipped over when stepping.
5597 @xref{Specify Location}.
5599 @item -rfunction @var{regexp}
5600 @itemx -rfu @var{regexp}
5601 @cindex skipping over functions via regular expressions
5602 Functions whose name matches @var{regexp} will be skipped over when stepping.
5604 This form is useful for complex function names.
5605 For example, there is generally no need to step into C@t{++} @code{std::string}
5606 constructors or destructors. Plus with C@t{++} templates it can be hard to
5607 write out the full name of the function, and often it doesn't matter what
5608 the template arguments are. Specifying the function to be skipped as a
5609 regular expression makes this easier.
5612 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5615 If you want to skip every templated C@t{++} constructor and destructor
5616 in the @code{std} namespace you can do:
5619 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5623 If no options are specified, the function you're currently debugging
5626 @kindex skip function
5627 @item skip function @r{[}@var{linespec}@r{]}
5628 After running this command, the function named by @var{linespec} or the
5629 function containing the line named by @var{linespec} will be skipped over when
5630 stepping. @xref{Specify Location}.
5632 If you do not specify @var{linespec}, the function you're currently debugging
5635 (If you have a function called @code{file} that you want to skip, use
5636 @kbd{skip function file}.)
5639 @item skip file @r{[}@var{filename}@r{]}
5640 After running this command, any function whose source lives in @var{filename}
5641 will be skipped over when stepping.
5644 (gdb) skip file boring.c
5645 File boring.c will be skipped when stepping.
5648 If you do not specify @var{filename}, functions whose source lives in the file
5649 you're currently debugging will be skipped.
5652 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5653 These are the commands for managing your list of skips:
5657 @item info skip @r{[}@var{range}@r{]}
5658 Print details about the specified skip(s). If @var{range} is not specified,
5659 print a table with details about all functions and files marked for skipping.
5660 @code{info skip} prints the following information about each skip:
5664 A number identifying this skip.
5665 @item Enabled or Disabled
5666 Enabled skips are marked with @samp{y}.
5667 Disabled skips are marked with @samp{n}.
5669 If the file name is a @samp{glob} pattern this is @samp{y}.
5670 Otherwise it is @samp{n}.
5672 The name or @samp{glob} pattern of the file to be skipped.
5673 If no file is specified this is @samp{<none>}.
5675 If the function name is a @samp{regular expression} this is @samp{y}.
5676 Otherwise it is @samp{n}.
5678 The name or regular expression of the function to skip.
5679 If no function is specified this is @samp{<none>}.
5683 @item skip delete @r{[}@var{range}@r{]}
5684 Delete the specified skip(s). If @var{range} is not specified, delete all
5688 @item skip enable @r{[}@var{range}@r{]}
5689 Enable the specified skip(s). If @var{range} is not specified, enable all
5692 @kindex skip disable
5693 @item skip disable @r{[}@var{range}@r{]}
5694 Disable the specified skip(s). If @var{range} is not specified, disable all
5703 A signal is an asynchronous event that can happen in a program. The
5704 operating system defines the possible kinds of signals, and gives each
5705 kind a name and a number. For example, in Unix @code{SIGINT} is the
5706 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5707 @code{SIGSEGV} is the signal a program gets from referencing a place in
5708 memory far away from all the areas in use; @code{SIGALRM} occurs when
5709 the alarm clock timer goes off (which happens only if your program has
5710 requested an alarm).
5712 @cindex fatal signals
5713 Some signals, including @code{SIGALRM}, are a normal part of the
5714 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5715 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5716 program has not specified in advance some other way to handle the signal.
5717 @code{SIGINT} does not indicate an error in your program, but it is normally
5718 fatal so it can carry out the purpose of the interrupt: to kill the program.
5720 @value{GDBN} has the ability to detect any occurrence of a signal in your
5721 program. You can tell @value{GDBN} in advance what to do for each kind of
5724 @cindex handling signals
5725 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5726 @code{SIGALRM} be silently passed to your program
5727 (so as not to interfere with their role in the program's functioning)
5728 but to stop your program immediately whenever an error signal happens.
5729 You can change these settings with the @code{handle} command.
5732 @kindex info signals
5736 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5737 handle each one. You can use this to see the signal numbers of all
5738 the defined types of signals.
5740 @item info signals @var{sig}
5741 Similar, but print information only about the specified signal number.
5743 @code{info handle} is an alias for @code{info signals}.
5745 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5746 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5747 for details about this command.
5750 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5751 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5752 can be the number of a signal or its name (with or without the
5753 @samp{SIG} at the beginning); a list of signal numbers of the form
5754 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5755 known signals. Optional arguments @var{keywords}, described below,
5756 say what change to make.
5760 The keywords allowed by the @code{handle} command can be abbreviated.
5761 Their full names are:
5765 @value{GDBN} should not stop your program when this signal happens. It may
5766 still print a message telling you that the signal has come in.
5769 @value{GDBN} should stop your program when this signal happens. This implies
5770 the @code{print} keyword as well.
5773 @value{GDBN} should print a message when this signal happens.
5776 @value{GDBN} should not mention the occurrence of the signal at all. This
5777 implies the @code{nostop} keyword as well.
5781 @value{GDBN} should allow your program to see this signal; your program
5782 can handle the signal, or else it may terminate if the signal is fatal
5783 and not handled. @code{pass} and @code{noignore} are synonyms.
5787 @value{GDBN} should not allow your program to see this signal.
5788 @code{nopass} and @code{ignore} are synonyms.
5792 When a signal stops your program, the signal is not visible to the
5794 continue. Your program sees the signal then, if @code{pass} is in
5795 effect for the signal in question @emph{at that time}. In other words,
5796 after @value{GDBN} reports a signal, you can use the @code{handle}
5797 command with @code{pass} or @code{nopass} to control whether your
5798 program sees that signal when you continue.
5800 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5801 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5802 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5805 You can also use the @code{signal} command to prevent your program from
5806 seeing a signal, or cause it to see a signal it normally would not see,
5807 or to give it any signal at any time. For example, if your program stopped
5808 due to some sort of memory reference error, you might store correct
5809 values into the erroneous variables and continue, hoping to see more
5810 execution; but your program would probably terminate immediately as
5811 a result of the fatal signal once it saw the signal. To prevent this,
5812 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5815 @cindex stepping and signal handlers
5816 @anchor{stepping and signal handlers}
5818 @value{GDBN} optimizes for stepping the mainline code. If a signal
5819 that has @code{handle nostop} and @code{handle pass} set arrives while
5820 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5821 in progress, @value{GDBN} lets the signal handler run and then resumes
5822 stepping the mainline code once the signal handler returns. In other
5823 words, @value{GDBN} steps over the signal handler. This prevents
5824 signals that you've specified as not interesting (with @code{handle
5825 nostop}) from changing the focus of debugging unexpectedly. Note that
5826 the signal handler itself may still hit a breakpoint, stop for another
5827 signal that has @code{handle stop} in effect, or for any other event
5828 that normally results in stopping the stepping command sooner. Also
5829 note that @value{GDBN} still informs you that the program received a
5830 signal if @code{handle print} is set.
5832 @anchor{stepping into signal handlers}
5834 If you set @code{handle pass} for a signal, and your program sets up a
5835 handler for it, then issuing a stepping command, such as @code{step}
5836 or @code{stepi}, when your program is stopped due to the signal will
5837 step @emph{into} the signal handler (if the target supports that).
5839 Likewise, if you use the @code{queue-signal} command to queue a signal
5840 to be delivered to the current thread when execution of the thread
5841 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5842 stepping command will step into the signal handler.
5844 Here's an example, using @code{stepi} to step to the first instruction
5845 of @code{SIGUSR1}'s handler:
5848 (@value{GDBP}) handle SIGUSR1
5849 Signal Stop Print Pass to program Description
5850 SIGUSR1 Yes Yes Yes User defined signal 1
5854 Program received signal SIGUSR1, User defined signal 1.
5855 main () sigusr1.c:28
5858 sigusr1_handler () at sigusr1.c:9
5862 The same, but using @code{queue-signal} instead of waiting for the
5863 program to receive the signal first:
5868 (@value{GDBP}) queue-signal SIGUSR1
5870 sigusr1_handler () at sigusr1.c:9
5875 @cindex extra signal information
5876 @anchor{extra signal information}
5878 On some targets, @value{GDBN} can inspect extra signal information
5879 associated with the intercepted signal, before it is actually
5880 delivered to the program being debugged. This information is exported
5881 by the convenience variable @code{$_siginfo}, and consists of data
5882 that is passed by the kernel to the signal handler at the time of the
5883 receipt of a signal. The data type of the information itself is
5884 target dependent. You can see the data type using the @code{ptype
5885 $_siginfo} command. On Unix systems, it typically corresponds to the
5886 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5889 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5890 referenced address that raised a segmentation fault.
5894 (@value{GDBP}) continue
5895 Program received signal SIGSEGV, Segmentation fault.
5896 0x0000000000400766 in main ()
5898 (@value{GDBP}) ptype $_siginfo
5905 struct @{...@} _kill;
5906 struct @{...@} _timer;
5908 struct @{...@} _sigchld;
5909 struct @{...@} _sigfault;
5910 struct @{...@} _sigpoll;
5913 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5917 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5918 $1 = (void *) 0x7ffff7ff7000
5922 Depending on target support, @code{$_siginfo} may also be writable.
5924 @cindex Intel MPX boundary violations
5925 @cindex boundary violations, Intel MPX
5926 On some targets, a @code{SIGSEGV} can be caused by a boundary
5927 violation, i.e., accessing an address outside of the allowed range.
5928 In those cases @value{GDBN} may displays additional information,
5929 depending on how @value{GDBN} has been told to handle the signal.
5930 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5931 kind: "Upper" or "Lower", the memory address accessed and the
5932 bounds, while with @code{handle nostop SIGSEGV} no additional
5933 information is displayed.
5935 The usual output of a segfault is:
5937 Program received signal SIGSEGV, Segmentation fault
5938 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5939 68 value = *(p + len);
5942 While a bound violation is presented as:
5944 Program received signal SIGSEGV, Segmentation fault
5945 Upper bound violation while accessing address 0x7fffffffc3b3
5946 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5947 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5948 68 value = *(p + len);
5952 @section Stopping and Starting Multi-thread Programs
5954 @cindex stopped threads
5955 @cindex threads, stopped
5957 @cindex continuing threads
5958 @cindex threads, continuing
5960 @value{GDBN} supports debugging programs with multiple threads
5961 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5962 are two modes of controlling execution of your program within the
5963 debugger. In the default mode, referred to as @dfn{all-stop mode},
5964 when any thread in your program stops (for example, at a breakpoint
5965 or while being stepped), all other threads in the program are also stopped by
5966 @value{GDBN}. On some targets, @value{GDBN} also supports
5967 @dfn{non-stop mode}, in which other threads can continue to run freely while
5968 you examine the stopped thread in the debugger.
5971 * All-Stop Mode:: All threads stop when GDB takes control
5972 * Non-Stop Mode:: Other threads continue to execute
5973 * Background Execution:: Running your program asynchronously
5974 * Thread-Specific Breakpoints:: Controlling breakpoints
5975 * Interrupted System Calls:: GDB may interfere with system calls
5976 * Observer Mode:: GDB does not alter program behavior
5980 @subsection All-Stop Mode
5982 @cindex all-stop mode
5984 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5985 @emph{all} threads of execution stop, not just the current thread. This
5986 allows you to examine the overall state of the program, including
5987 switching between threads, without worrying that things may change
5990 Conversely, whenever you restart the program, @emph{all} threads start
5991 executing. @emph{This is true even when single-stepping} with commands
5992 like @code{step} or @code{next}.
5994 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5995 Since thread scheduling is up to your debugging target's operating
5996 system (not controlled by @value{GDBN}), other threads may
5997 execute more than one statement while the current thread completes a
5998 single step. Moreover, in general other threads stop in the middle of a
5999 statement, rather than at a clean statement boundary, when the program
6002 You might even find your program stopped in another thread after
6003 continuing or even single-stepping. This happens whenever some other
6004 thread runs into a breakpoint, a signal, or an exception before the
6005 first thread completes whatever you requested.
6007 @cindex automatic thread selection
6008 @cindex switching threads automatically
6009 @cindex threads, automatic switching
6010 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6011 signal, it automatically selects the thread where that breakpoint or
6012 signal happened. @value{GDBN} alerts you to the context switch with a
6013 message such as @samp{[Switching to Thread @var{n}]} to identify the
6016 On some OSes, you can modify @value{GDBN}'s default behavior by
6017 locking the OS scheduler to allow only a single thread to run.
6020 @item set scheduler-locking @var{mode}
6021 @cindex scheduler locking mode
6022 @cindex lock scheduler
6023 Set the scheduler locking mode. It applies to normal execution,
6024 record mode, and replay mode. If it is @code{off}, then there is no
6025 locking and any thread may run at any time. If @code{on}, then only
6026 the current thread may run when the inferior is resumed. The
6027 @code{step} mode optimizes for single-stepping; it prevents other
6028 threads from preempting the current thread while you are stepping, so
6029 that the focus of debugging does not change unexpectedly. Other
6030 threads never get a chance to run when you step, and they are
6031 completely free to run when you use commands like @samp{continue},
6032 @samp{until}, or @samp{finish}. However, unless another thread hits a
6033 breakpoint during its timeslice, @value{GDBN} does not change the
6034 current thread away from the thread that you are debugging. The
6035 @code{replay} mode behaves like @code{off} in record mode and like
6036 @code{on} in replay mode.
6038 @item show scheduler-locking
6039 Display the current scheduler locking mode.
6042 @cindex resume threads of multiple processes simultaneously
6043 By default, when you issue one of the execution commands such as
6044 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6045 threads of the current inferior to run. For example, if @value{GDBN}
6046 is attached to two inferiors, each with two threads, the
6047 @code{continue} command resumes only the two threads of the current
6048 inferior. This is useful, for example, when you debug a program that
6049 forks and you want to hold the parent stopped (so that, for instance,
6050 it doesn't run to exit), while you debug the child. In other
6051 situations, you may not be interested in inspecting the current state
6052 of any of the processes @value{GDBN} is attached to, and you may want
6053 to resume them all until some breakpoint is hit. In the latter case,
6054 you can instruct @value{GDBN} to allow all threads of all the
6055 inferiors to run with the @w{@code{set schedule-multiple}} command.
6058 @kindex set schedule-multiple
6059 @item set schedule-multiple
6060 Set the mode for allowing threads of multiple processes to be resumed
6061 when an execution command is issued. When @code{on}, all threads of
6062 all processes are allowed to run. When @code{off}, only the threads
6063 of the current process are resumed. The default is @code{off}. The
6064 @code{scheduler-locking} mode takes precedence when set to @code{on},
6065 or while you are stepping and set to @code{step}.
6067 @item show schedule-multiple
6068 Display the current mode for resuming the execution of threads of
6073 @subsection Non-Stop Mode
6075 @cindex non-stop mode
6077 @c This section is really only a place-holder, and needs to be expanded
6078 @c with more details.
6080 For some multi-threaded targets, @value{GDBN} supports an optional
6081 mode of operation in which you can examine stopped program threads in
6082 the debugger while other threads continue to execute freely. This
6083 minimizes intrusion when debugging live systems, such as programs
6084 where some threads have real-time constraints or must continue to
6085 respond to external events. This is referred to as @dfn{non-stop} mode.
6087 In non-stop mode, when a thread stops to report a debugging event,
6088 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6089 threads as well, in contrast to the all-stop mode behavior. Additionally,
6090 execution commands such as @code{continue} and @code{step} apply by default
6091 only to the current thread in non-stop mode, rather than all threads as
6092 in all-stop mode. This allows you to control threads explicitly in
6093 ways that are not possible in all-stop mode --- for example, stepping
6094 one thread while allowing others to run freely, stepping
6095 one thread while holding all others stopped, or stepping several threads
6096 independently and simultaneously.
6098 To enter non-stop mode, use this sequence of commands before you run
6099 or attach to your program:
6102 # If using the CLI, pagination breaks non-stop.
6105 # Finally, turn it on!
6109 You can use these commands to manipulate the non-stop mode setting:
6112 @kindex set non-stop
6113 @item set non-stop on
6114 Enable selection of non-stop mode.
6115 @item set non-stop off
6116 Disable selection of non-stop mode.
6117 @kindex show non-stop
6119 Show the current non-stop enablement setting.
6122 Note these commands only reflect whether non-stop mode is enabled,
6123 not whether the currently-executing program is being run in non-stop mode.
6124 In particular, the @code{set non-stop} preference is only consulted when
6125 @value{GDBN} starts or connects to the target program, and it is generally
6126 not possible to switch modes once debugging has started. Furthermore,
6127 since not all targets support non-stop mode, even when you have enabled
6128 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6131 In non-stop mode, all execution commands apply only to the current thread
6132 by default. That is, @code{continue} only continues one thread.
6133 To continue all threads, issue @code{continue -a} or @code{c -a}.
6135 You can use @value{GDBN}'s background execution commands
6136 (@pxref{Background Execution}) to run some threads in the background
6137 while you continue to examine or step others from @value{GDBN}.
6138 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6139 always executed asynchronously in non-stop mode.
6141 Suspending execution is done with the @code{interrupt} command when
6142 running in the background, or @kbd{Ctrl-c} during foreground execution.
6143 In all-stop mode, this stops the whole process;
6144 but in non-stop mode the interrupt applies only to the current thread.
6145 To stop the whole program, use @code{interrupt -a}.
6147 Other execution commands do not currently support the @code{-a} option.
6149 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6150 that thread current, as it does in all-stop mode. This is because the
6151 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6152 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6153 changed to a different thread just as you entered a command to operate on the
6154 previously current thread.
6156 @node Background Execution
6157 @subsection Background Execution
6159 @cindex foreground execution
6160 @cindex background execution
6161 @cindex asynchronous execution
6162 @cindex execution, foreground, background and asynchronous
6164 @value{GDBN}'s execution commands have two variants: the normal
6165 foreground (synchronous) behavior, and a background
6166 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6167 the program to report that some thread has stopped before prompting for
6168 another command. In background execution, @value{GDBN} immediately gives
6169 a command prompt so that you can issue other commands while your program runs.
6171 If the target doesn't support async mode, @value{GDBN} issues an error
6172 message if you attempt to use the background execution commands.
6174 To specify background execution, add a @code{&} to the command. For example,
6175 the background form of the @code{continue} command is @code{continue&}, or
6176 just @code{c&}. The execution commands that accept background execution
6182 @xref{Starting, , Starting your Program}.
6186 @xref{Attach, , Debugging an Already-running Process}.
6190 @xref{Continuing and Stepping, step}.
6194 @xref{Continuing and Stepping, stepi}.
6198 @xref{Continuing and Stepping, next}.
6202 @xref{Continuing and Stepping, nexti}.
6206 @xref{Continuing and Stepping, continue}.
6210 @xref{Continuing and Stepping, finish}.
6214 @xref{Continuing and Stepping, until}.
6218 Background execution is especially useful in conjunction with non-stop
6219 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6220 However, you can also use these commands in the normal all-stop mode with
6221 the restriction that you cannot issue another execution command until the
6222 previous one finishes. Examples of commands that are valid in all-stop
6223 mode while the program is running include @code{help} and @code{info break}.
6225 You can interrupt your program while it is running in the background by
6226 using the @code{interrupt} command.
6233 Suspend execution of the running program. In all-stop mode,
6234 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6235 only the current thread. To stop the whole program in non-stop mode,
6236 use @code{interrupt -a}.
6239 @node Thread-Specific Breakpoints
6240 @subsection Thread-Specific Breakpoints
6242 When your program has multiple threads (@pxref{Threads,, Debugging
6243 Programs with Multiple Threads}), you can choose whether to set
6244 breakpoints on all threads, or on a particular thread.
6247 @cindex breakpoints and threads
6248 @cindex thread breakpoints
6249 @kindex break @dots{} thread @var{thread-id}
6250 @item break @var{location} thread @var{thread-id}
6251 @itemx break @var{location} thread @var{thread-id} if @dots{}
6252 @var{location} specifies source lines; there are several ways of
6253 writing them (@pxref{Specify Location}), but the effect is always to
6254 specify some source line.
6256 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6257 to specify that you only want @value{GDBN} to stop the program when a
6258 particular thread reaches this breakpoint. The @var{thread-id} specifier
6259 is one of the thread identifiers assigned by @value{GDBN}, shown
6260 in the first column of the @samp{info threads} display.
6262 If you do not specify @samp{thread @var{thread-id}} when you set a
6263 breakpoint, the breakpoint applies to @emph{all} threads of your
6266 You can use the @code{thread} qualifier on conditional breakpoints as
6267 well; in this case, place @samp{thread @var{thread-id}} before or
6268 after the breakpoint condition, like this:
6271 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6276 Thread-specific breakpoints are automatically deleted when
6277 @value{GDBN} detects the corresponding thread is no longer in the
6278 thread list. For example:
6282 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6285 There are several ways for a thread to disappear, such as a regular
6286 thread exit, but also when you detach from the process with the
6287 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6288 Process}), or if @value{GDBN} loses the remote connection
6289 (@pxref{Remote Debugging}), etc. Note that with some targets,
6290 @value{GDBN} is only able to detect a thread has exited when the user
6291 explictly asks for the thread list with the @code{info threads}
6294 @node Interrupted System Calls
6295 @subsection Interrupted System Calls
6297 @cindex thread breakpoints and system calls
6298 @cindex system calls and thread breakpoints
6299 @cindex premature return from system calls
6300 There is an unfortunate side effect when using @value{GDBN} to debug
6301 multi-threaded programs. If one thread stops for a
6302 breakpoint, or for some other reason, and another thread is blocked in a
6303 system call, then the system call may return prematurely. This is a
6304 consequence of the interaction between multiple threads and the signals
6305 that @value{GDBN} uses to implement breakpoints and other events that
6308 To handle this problem, your program should check the return value of
6309 each system call and react appropriately. This is good programming
6312 For example, do not write code like this:
6318 The call to @code{sleep} will return early if a different thread stops
6319 at a breakpoint or for some other reason.
6321 Instead, write this:
6326 unslept = sleep (unslept);
6329 A system call is allowed to return early, so the system is still
6330 conforming to its specification. But @value{GDBN} does cause your
6331 multi-threaded program to behave differently than it would without
6334 Also, @value{GDBN} uses internal breakpoints in the thread library to
6335 monitor certain events such as thread creation and thread destruction.
6336 When such an event happens, a system call in another thread may return
6337 prematurely, even though your program does not appear to stop.
6340 @subsection Observer Mode
6342 If you want to build on non-stop mode and observe program behavior
6343 without any chance of disruption by @value{GDBN}, you can set
6344 variables to disable all of the debugger's attempts to modify state,
6345 whether by writing memory, inserting breakpoints, etc. These operate
6346 at a low level, intercepting operations from all commands.
6348 When all of these are set to @code{off}, then @value{GDBN} is said to
6349 be @dfn{observer mode}. As a convenience, the variable
6350 @code{observer} can be set to disable these, plus enable non-stop
6353 Note that @value{GDBN} will not prevent you from making nonsensical
6354 combinations of these settings. For instance, if you have enabled
6355 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6356 then breakpoints that work by writing trap instructions into the code
6357 stream will still not be able to be placed.
6362 @item set observer on
6363 @itemx set observer off
6364 When set to @code{on}, this disables all the permission variables
6365 below (except for @code{insert-fast-tracepoints}), plus enables
6366 non-stop debugging. Setting this to @code{off} switches back to
6367 normal debugging, though remaining in non-stop mode.
6370 Show whether observer mode is on or off.
6372 @kindex may-write-registers
6373 @item set may-write-registers on
6374 @itemx set may-write-registers off
6375 This controls whether @value{GDBN} will attempt to alter the values of
6376 registers, such as with assignment expressions in @code{print}, or the
6377 @code{jump} command. It defaults to @code{on}.
6379 @item show may-write-registers
6380 Show the current permission to write registers.
6382 @kindex may-write-memory
6383 @item set may-write-memory on
6384 @itemx set may-write-memory off
6385 This controls whether @value{GDBN} will attempt to alter the contents
6386 of memory, such as with assignment expressions in @code{print}. It
6387 defaults to @code{on}.
6389 @item show may-write-memory
6390 Show the current permission to write memory.
6392 @kindex may-insert-breakpoints
6393 @item set may-insert-breakpoints on
6394 @itemx set may-insert-breakpoints off
6395 This controls whether @value{GDBN} will attempt to insert breakpoints.
6396 This affects all breakpoints, including internal breakpoints defined
6397 by @value{GDBN}. It defaults to @code{on}.
6399 @item show may-insert-breakpoints
6400 Show the current permission to insert breakpoints.
6402 @kindex may-insert-tracepoints
6403 @item set may-insert-tracepoints on
6404 @itemx set may-insert-tracepoints off
6405 This controls whether @value{GDBN} will attempt to insert (regular)
6406 tracepoints at the beginning of a tracing experiment. It affects only
6407 non-fast tracepoints, fast tracepoints being under the control of
6408 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6410 @item show may-insert-tracepoints
6411 Show the current permission to insert tracepoints.
6413 @kindex may-insert-fast-tracepoints
6414 @item set may-insert-fast-tracepoints on
6415 @itemx set may-insert-fast-tracepoints off
6416 This controls whether @value{GDBN} will attempt to insert fast
6417 tracepoints at the beginning of a tracing experiment. It affects only
6418 fast tracepoints, regular (non-fast) tracepoints being under the
6419 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6421 @item show may-insert-fast-tracepoints
6422 Show the current permission to insert fast tracepoints.
6424 @kindex may-interrupt
6425 @item set may-interrupt on
6426 @itemx set may-interrupt off
6427 This controls whether @value{GDBN} will attempt to interrupt or stop
6428 program execution. When this variable is @code{off}, the
6429 @code{interrupt} command will have no effect, nor will
6430 @kbd{Ctrl-c}. It defaults to @code{on}.
6432 @item show may-interrupt
6433 Show the current permission to interrupt or stop the program.
6437 @node Reverse Execution
6438 @chapter Running programs backward
6439 @cindex reverse execution
6440 @cindex running programs backward
6442 When you are debugging a program, it is not unusual to realize that
6443 you have gone too far, and some event of interest has already happened.
6444 If the target environment supports it, @value{GDBN} can allow you to
6445 ``rewind'' the program by running it backward.
6447 A target environment that supports reverse execution should be able
6448 to ``undo'' the changes in machine state that have taken place as the
6449 program was executing normally. Variables, registers etc.@: should
6450 revert to their previous values. Obviously this requires a great
6451 deal of sophistication on the part of the target environment; not
6452 all target environments can support reverse execution.
6454 When a program is executed in reverse, the instructions that
6455 have most recently been executed are ``un-executed'', in reverse
6456 order. The program counter runs backward, following the previous
6457 thread of execution in reverse. As each instruction is ``un-executed'',
6458 the values of memory and/or registers that were changed by that
6459 instruction are reverted to their previous states. After executing
6460 a piece of source code in reverse, all side effects of that code
6461 should be ``undone'', and all variables should be returned to their
6462 prior values@footnote{
6463 Note that some side effects are easier to undo than others. For instance,
6464 memory and registers are relatively easy, but device I/O is hard. Some
6465 targets may be able undo things like device I/O, and some may not.
6467 The contract between @value{GDBN} and the reverse executing target
6468 requires only that the target do something reasonable when
6469 @value{GDBN} tells it to execute backwards, and then report the
6470 results back to @value{GDBN}. Whatever the target reports back to
6471 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6472 assumes that the memory and registers that the target reports are in a
6473 consistant state, but @value{GDBN} accepts whatever it is given.
6476 If you are debugging in a target environment that supports
6477 reverse execution, @value{GDBN} provides the following commands.
6480 @kindex reverse-continue
6481 @kindex rc @r{(@code{reverse-continue})}
6482 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6483 @itemx rc @r{[}@var{ignore-count}@r{]}
6484 Beginning at the point where your program last stopped, start executing
6485 in reverse. Reverse execution will stop for breakpoints and synchronous
6486 exceptions (signals), just like normal execution. Behavior of
6487 asynchronous signals depends on the target environment.
6489 @kindex reverse-step
6490 @kindex rs @r{(@code{step})}
6491 @item reverse-step @r{[}@var{count}@r{]}
6492 Run the program backward until control reaches the start of a
6493 different source line; then stop it, and return control to @value{GDBN}.
6495 Like the @code{step} command, @code{reverse-step} will only stop
6496 at the beginning of a source line. It ``un-executes'' the previously
6497 executed source line. If the previous source line included calls to
6498 debuggable functions, @code{reverse-step} will step (backward) into
6499 the called function, stopping at the beginning of the @emph{last}
6500 statement in the called function (typically a return statement).
6502 Also, as with the @code{step} command, if non-debuggable functions are
6503 called, @code{reverse-step} will run thru them backward without stopping.
6505 @kindex reverse-stepi
6506 @kindex rsi @r{(@code{reverse-stepi})}
6507 @item reverse-stepi @r{[}@var{count}@r{]}
6508 Reverse-execute one machine instruction. Note that the instruction
6509 to be reverse-executed is @emph{not} the one pointed to by the program
6510 counter, but the instruction executed prior to that one. For instance,
6511 if the last instruction was a jump, @code{reverse-stepi} will take you
6512 back from the destination of the jump to the jump instruction itself.
6514 @kindex reverse-next
6515 @kindex rn @r{(@code{reverse-next})}
6516 @item reverse-next @r{[}@var{count}@r{]}
6517 Run backward to the beginning of the previous line executed in
6518 the current (innermost) stack frame. If the line contains function
6519 calls, they will be ``un-executed'' without stopping. Starting from
6520 the first line of a function, @code{reverse-next} will take you back
6521 to the caller of that function, @emph{before} the function was called,
6522 just as the normal @code{next} command would take you from the last
6523 line of a function back to its return to its caller
6524 @footnote{Unless the code is too heavily optimized.}.
6526 @kindex reverse-nexti
6527 @kindex rni @r{(@code{reverse-nexti})}
6528 @item reverse-nexti @r{[}@var{count}@r{]}
6529 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6530 in reverse, except that called functions are ``un-executed'' atomically.
6531 That is, if the previously executed instruction was a return from
6532 another function, @code{reverse-nexti} will continue to execute
6533 in reverse until the call to that function (from the current stack
6536 @kindex reverse-finish
6537 @item reverse-finish
6538 Just as the @code{finish} command takes you to the point where the
6539 current function returns, @code{reverse-finish} takes you to the point
6540 where it was called. Instead of ending up at the end of the current
6541 function invocation, you end up at the beginning.
6543 @kindex set exec-direction
6544 @item set exec-direction
6545 Set the direction of target execution.
6546 @item set exec-direction reverse
6547 @cindex execute forward or backward in time
6548 @value{GDBN} will perform all execution commands in reverse, until the
6549 exec-direction mode is changed to ``forward''. Affected commands include
6550 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6551 command cannot be used in reverse mode.
6552 @item set exec-direction forward
6553 @value{GDBN} will perform all execution commands in the normal fashion.
6554 This is the default.
6558 @node Process Record and Replay
6559 @chapter Recording Inferior's Execution and Replaying It
6560 @cindex process record and replay
6561 @cindex recording inferior's execution and replaying it
6563 On some platforms, @value{GDBN} provides a special @dfn{process record
6564 and replay} target that can record a log of the process execution, and
6565 replay it later with both forward and reverse execution commands.
6568 When this target is in use, if the execution log includes the record
6569 for the next instruction, @value{GDBN} will debug in @dfn{replay
6570 mode}. In the replay mode, the inferior does not really execute code
6571 instructions. Instead, all the events that normally happen during
6572 code execution are taken from the execution log. While code is not
6573 really executed in replay mode, the values of registers (including the
6574 program counter register) and the memory of the inferior are still
6575 changed as they normally would. Their contents are taken from the
6579 If the record for the next instruction is not in the execution log,
6580 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6581 inferior executes normally, and @value{GDBN} records the execution log
6584 The process record and replay target supports reverse execution
6585 (@pxref{Reverse Execution}), even if the platform on which the
6586 inferior runs does not. However, the reverse execution is limited in
6587 this case by the range of the instructions recorded in the execution
6588 log. In other words, reverse execution on platforms that don't
6589 support it directly can only be done in the replay mode.
6591 When debugging in the reverse direction, @value{GDBN} will work in
6592 replay mode as long as the execution log includes the record for the
6593 previous instruction; otherwise, it will work in record mode, if the
6594 platform supports reverse execution, or stop if not.
6596 For architecture environments that support process record and replay,
6597 @value{GDBN} provides the following commands:
6600 @kindex target record
6601 @kindex target record-full
6602 @kindex target record-btrace
6605 @kindex record btrace
6606 @kindex record btrace bts
6607 @kindex record btrace pt
6613 @kindex rec btrace bts
6614 @kindex rec btrace pt
6617 @item record @var{method}
6618 This command starts the process record and replay target. The
6619 recording method can be specified as parameter. Without a parameter
6620 the command uses the @code{full} recording method. The following
6621 recording methods are available:
6625 Full record/replay recording using @value{GDBN}'s software record and
6626 replay implementation. This method allows replaying and reverse
6629 @item btrace @var{format}
6630 Hardware-supported instruction recording. This method does not record
6631 data. Further, the data is collected in a ring buffer so old data will
6632 be overwritten when the buffer is full. It allows limited reverse
6633 execution. Variables and registers are not available during reverse
6636 The recording format can be specified as parameter. Without a parameter
6637 the command chooses the recording format. The following recording
6638 formats are available:
6642 @cindex branch trace store
6643 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6644 this format, the processor stores a from/to record for each executed
6645 branch in the btrace ring buffer.
6648 @cindex Intel Processor Trace
6649 Use the @dfn{Intel Processor Trace} recording format. In this
6650 format, the processor stores the execution trace in a compressed form
6651 that is afterwards decoded by @value{GDBN}.
6653 The trace can be recorded with very low overhead. The compressed
6654 trace format also allows small trace buffers to already contain a big
6655 number of instructions compared to @acronym{BTS}.
6657 Decoding the recorded execution trace, on the other hand, is more
6658 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6659 increased number of instructions to process. You should increase the
6660 buffer-size with care.
6663 Not all recording formats may be available on all processors.
6666 The process record and replay target can only debug a process that is
6667 already running. Therefore, you need first to start the process with
6668 the @kbd{run} or @kbd{start} commands, and then start the recording
6669 with the @kbd{record @var{method}} command.
6671 @cindex displaced stepping, and process record and replay
6672 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6673 will be automatically disabled when process record and replay target
6674 is started. That's because the process record and replay target
6675 doesn't support displaced stepping.
6677 @cindex non-stop mode, and process record and replay
6678 @cindex asynchronous execution, and process record and replay
6679 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6680 the asynchronous execution mode (@pxref{Background Execution}), not
6681 all recording methods are available. The @code{full} recording method
6682 does not support these two modes.
6687 Stop the process record and replay target. When process record and
6688 replay target stops, the entire execution log will be deleted and the
6689 inferior will either be terminated, or will remain in its final state.
6691 When you stop the process record and replay target in record mode (at
6692 the end of the execution log), the inferior will be stopped at the
6693 next instruction that would have been recorded. In other words, if
6694 you record for a while and then stop recording, the inferior process
6695 will be left in the same state as if the recording never happened.
6697 On the other hand, if the process record and replay target is stopped
6698 while in replay mode (that is, not at the end of the execution log,
6699 but at some earlier point), the inferior process will become ``live''
6700 at that earlier state, and it will then be possible to continue the
6701 usual ``live'' debugging of the process from that state.
6703 When the inferior process exits, or @value{GDBN} detaches from it,
6704 process record and replay target will automatically stop itself.
6708 Go to a specific location in the execution log. There are several
6709 ways to specify the location to go to:
6712 @item record goto begin
6713 @itemx record goto start
6714 Go to the beginning of the execution log.
6716 @item record goto end
6717 Go to the end of the execution log.
6719 @item record goto @var{n}
6720 Go to instruction number @var{n} in the execution log.
6724 @item record save @var{filename}
6725 Save the execution log to a file @file{@var{filename}}.
6726 Default filename is @file{gdb_record.@var{process_id}}, where
6727 @var{process_id} is the process ID of the inferior.
6729 This command may not be available for all recording methods.
6731 @kindex record restore
6732 @item record restore @var{filename}
6733 Restore the execution log from a file @file{@var{filename}}.
6734 File must have been created with @code{record save}.
6736 @kindex set record full
6737 @item set record full insn-number-max @var{limit}
6738 @itemx set record full insn-number-max unlimited
6739 Set the limit of instructions to be recorded for the @code{full}
6740 recording method. Default value is 200000.
6742 If @var{limit} is a positive number, then @value{GDBN} will start
6743 deleting instructions from the log once the number of the record
6744 instructions becomes greater than @var{limit}. For every new recorded
6745 instruction, @value{GDBN} will delete the earliest recorded
6746 instruction to keep the number of recorded instructions at the limit.
6747 (Since deleting recorded instructions loses information, @value{GDBN}
6748 lets you control what happens when the limit is reached, by means of
6749 the @code{stop-at-limit} option, described below.)
6751 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6752 delete recorded instructions from the execution log. The number of
6753 recorded instructions is limited only by the available memory.
6755 @kindex show record full
6756 @item show record full insn-number-max
6757 Show the limit of instructions to be recorded with the @code{full}
6760 @item set record full stop-at-limit
6761 Control the behavior of the @code{full} recording method when the
6762 number of recorded instructions reaches the limit. If ON (the
6763 default), @value{GDBN} will stop when the limit is reached for the
6764 first time and ask you whether you want to stop the inferior or
6765 continue running it and recording the execution log. If you decide
6766 to continue recording, each new recorded instruction will cause the
6767 oldest one to be deleted.
6769 If this option is OFF, @value{GDBN} will automatically delete the
6770 oldest record to make room for each new one, without asking.
6772 @item show record full stop-at-limit
6773 Show the current setting of @code{stop-at-limit}.
6775 @item set record full memory-query
6776 Control the behavior when @value{GDBN} is unable to record memory
6777 changes caused by an instruction for the @code{full} recording method.
6778 If ON, @value{GDBN} will query whether to stop the inferior in that
6781 If this option is OFF (the default), @value{GDBN} will automatically
6782 ignore the effect of such instructions on memory. Later, when
6783 @value{GDBN} replays this execution log, it will mark the log of this
6784 instruction as not accessible, and it will not affect the replay
6787 @item show record full memory-query
6788 Show the current setting of @code{memory-query}.
6790 @kindex set record btrace
6791 The @code{btrace} record target does not trace data. As a
6792 convenience, when replaying, @value{GDBN} reads read-only memory off
6793 the live program directly, assuming that the addresses of the
6794 read-only areas don't change. This for example makes it possible to
6795 disassemble code while replaying, but not to print variables.
6796 In some cases, being able to inspect variables might be useful.
6797 You can use the following command for that:
6799 @item set record btrace replay-memory-access
6800 Control the behavior of the @code{btrace} recording method when
6801 accessing memory during replay. If @code{read-only} (the default),
6802 @value{GDBN} will only allow accesses to read-only memory.
6803 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6804 and to read-write memory. Beware that the accessed memory corresponds
6805 to the live target and not necessarily to the current replay
6808 @kindex show record btrace
6809 @item show record btrace replay-memory-access
6810 Show the current setting of @code{replay-memory-access}.
6812 @kindex set record btrace bts
6813 @item set record btrace bts buffer-size @var{size}
6814 @itemx set record btrace bts buffer-size unlimited
6815 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6816 format. Default is 64KB.
6818 If @var{size} is a positive number, then @value{GDBN} will try to
6819 allocate a buffer of at least @var{size} bytes for each new thread
6820 that uses the btrace recording method and the @acronym{BTS} format.
6821 The actually obtained buffer size may differ from the requested
6822 @var{size}. Use the @code{info record} command to see the actual
6823 buffer size for each thread that uses the btrace recording method and
6824 the @acronym{BTS} format.
6826 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6827 allocate a buffer of 4MB.
6829 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6830 also need longer to process the branch trace data before it can be used.
6832 @item show record btrace bts buffer-size @var{size}
6833 Show the current setting of the requested ring buffer size for branch
6834 tracing in @acronym{BTS} format.
6836 @kindex set record btrace pt
6837 @item set record btrace pt buffer-size @var{size}
6838 @itemx set record btrace pt buffer-size unlimited
6839 Set the requested ring buffer size for branch tracing in Intel
6840 Processor Trace format. Default is 16KB.
6842 If @var{size} is a positive number, then @value{GDBN} will try to
6843 allocate a buffer of at least @var{size} bytes for each new thread
6844 that uses the btrace recording method and the Intel Processor Trace
6845 format. The actually obtained buffer size may differ from the
6846 requested @var{size}. Use the @code{info record} command to see the
6847 actual buffer size for each thread.
6849 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6850 allocate a buffer of 4MB.
6852 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6853 also need longer to process the branch trace data before it can be used.
6855 @item show record btrace pt buffer-size @var{size}
6856 Show the current setting of the requested ring buffer size for branch
6857 tracing in Intel Processor Trace format.
6861 Show various statistics about the recording depending on the recording
6866 For the @code{full} recording method, it shows the state of process
6867 record and its in-memory execution log buffer, including:
6871 Whether in record mode or replay mode.
6873 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6875 Highest recorded instruction number.
6877 Current instruction about to be replayed (if in replay mode).
6879 Number of instructions contained in the execution log.
6881 Maximum number of instructions that may be contained in the execution log.
6885 For the @code{btrace} recording method, it shows:
6891 Number of instructions that have been recorded.
6893 Number of blocks of sequential control-flow formed by the recorded
6896 Whether in record mode or replay mode.
6899 For the @code{bts} recording format, it also shows:
6902 Size of the perf ring buffer.
6905 For the @code{pt} recording format, it also shows:
6908 Size of the perf ring buffer.
6912 @kindex record delete
6915 When record target runs in replay mode (``in the past''), delete the
6916 subsequent execution log and begin to record a new execution log starting
6917 from the current address. This means you will abandon the previously
6918 recorded ``future'' and begin recording a new ``future''.
6920 @kindex record instruction-history
6921 @kindex rec instruction-history
6922 @item record instruction-history
6923 Disassembles instructions from the recorded execution log. By
6924 default, ten instructions are disassembled. This can be changed using
6925 the @code{set record instruction-history-size} command. Instructions
6926 are printed in execution order.
6928 It can also print mixed source+disassembly if you specify the the
6929 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6930 as well as in symbolic form by specifying the @code{/r} modifier.
6932 The current position marker is printed for the instruction at the
6933 current program counter value. This instruction can appear multiple
6934 times in the trace and the current position marker will be printed
6935 every time. To omit the current position marker, specify the
6938 To better align the printed instructions when the trace contains
6939 instructions from more than one function, the function name may be
6940 omitted by specifying the @code{/f} modifier.
6942 Speculatively executed instructions are prefixed with @samp{?}. This
6943 feature is not available for all recording formats.
6945 There are several ways to specify what part of the execution log to
6949 @item record instruction-history @var{insn}
6950 Disassembles ten instructions starting from instruction number
6953 @item record instruction-history @var{insn}, +/-@var{n}
6954 Disassembles @var{n} instructions around instruction number
6955 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6956 @var{n} instructions after instruction number @var{insn}. If
6957 @var{n} is preceded with @code{-}, disassembles @var{n}
6958 instructions before instruction number @var{insn}.
6960 @item record instruction-history
6961 Disassembles ten more instructions after the last disassembly.
6963 @item record instruction-history -
6964 Disassembles ten more instructions before the last disassembly.
6966 @item record instruction-history @var{begin}, @var{end}
6967 Disassembles instructions beginning with instruction number
6968 @var{begin} until instruction number @var{end}. The instruction
6969 number @var{end} is included.
6972 This command may not be available for all recording methods.
6975 @item set record instruction-history-size @var{size}
6976 @itemx set record instruction-history-size unlimited
6977 Define how many instructions to disassemble in the @code{record
6978 instruction-history} command. The default value is 10.
6979 A @var{size} of @code{unlimited} means unlimited instructions.
6982 @item show record instruction-history-size
6983 Show how many instructions to disassemble in the @code{record
6984 instruction-history} command.
6986 @kindex record function-call-history
6987 @kindex rec function-call-history
6988 @item record function-call-history
6989 Prints the execution history at function granularity. It prints one
6990 line for each sequence of instructions that belong to the same
6991 function giving the name of that function, the source lines
6992 for this instruction sequence (if the @code{/l} modifier is
6993 specified), and the instructions numbers that form the sequence (if
6994 the @code{/i} modifier is specified). The function names are indented
6995 to reflect the call stack depth if the @code{/c} modifier is
6996 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7000 (@value{GDBP}) @b{list 1, 10}
7011 (@value{GDBP}) @b{record function-call-history /ilc}
7012 1 bar inst 1,4 at foo.c:6,8
7013 2 foo inst 5,10 at foo.c:2,3
7014 3 bar inst 11,13 at foo.c:9,10
7017 By default, ten lines are printed. This can be changed using the
7018 @code{set record function-call-history-size} command. Functions are
7019 printed in execution order. There are several ways to specify what
7023 @item record function-call-history @var{func}
7024 Prints ten functions starting from function number @var{func}.
7026 @item record function-call-history @var{func}, +/-@var{n}
7027 Prints @var{n} functions around function number @var{func}. If
7028 @var{n} is preceded with @code{+}, prints @var{n} functions after
7029 function number @var{func}. If @var{n} is preceded with @code{-},
7030 prints @var{n} functions before function number @var{func}.
7032 @item record function-call-history
7033 Prints ten more functions after the last ten-line print.
7035 @item record function-call-history -
7036 Prints ten more functions before the last ten-line print.
7038 @item record function-call-history @var{begin}, @var{end}
7039 Prints functions beginning with function number @var{begin} until
7040 function number @var{end}. The function number @var{end} is included.
7043 This command may not be available for all recording methods.
7045 @item set record function-call-history-size @var{size}
7046 @itemx set record function-call-history-size unlimited
7047 Define how many lines to print in the
7048 @code{record function-call-history} command. The default value is 10.
7049 A size of @code{unlimited} means unlimited lines.
7051 @item show record function-call-history-size
7052 Show how many lines to print in the
7053 @code{record function-call-history} command.
7058 @chapter Examining the Stack
7060 When your program has stopped, the first thing you need to know is where it
7061 stopped and how it got there.
7064 Each time your program performs a function call, information about the call
7066 That information includes the location of the call in your program,
7067 the arguments of the call,
7068 and the local variables of the function being called.
7069 The information is saved in a block of data called a @dfn{stack frame}.
7070 The stack frames are allocated in a region of memory called the @dfn{call
7073 When your program stops, the @value{GDBN} commands for examining the
7074 stack allow you to see all of this information.
7076 @cindex selected frame
7077 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7078 @value{GDBN} commands refer implicitly to the selected frame. In
7079 particular, whenever you ask @value{GDBN} for the value of a variable in
7080 your program, the value is found in the selected frame. There are
7081 special @value{GDBN} commands to select whichever frame you are
7082 interested in. @xref{Selection, ,Selecting a Frame}.
7084 When your program stops, @value{GDBN} automatically selects the
7085 currently executing frame and describes it briefly, similar to the
7086 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7089 * Frames:: Stack frames
7090 * Backtrace:: Backtraces
7091 * Selection:: Selecting a frame
7092 * Frame Info:: Information on a frame
7093 * Frame Filter Management:: Managing frame filters
7098 @section Stack Frames
7100 @cindex frame, definition
7102 The call stack is divided up into contiguous pieces called @dfn{stack
7103 frames}, or @dfn{frames} for short; each frame is the data associated
7104 with one call to one function. The frame contains the arguments given
7105 to the function, the function's local variables, and the address at
7106 which the function is executing.
7108 @cindex initial frame
7109 @cindex outermost frame
7110 @cindex innermost frame
7111 When your program is started, the stack has only one frame, that of the
7112 function @code{main}. This is called the @dfn{initial} frame or the
7113 @dfn{outermost} frame. Each time a function is called, a new frame is
7114 made. Each time a function returns, the frame for that function invocation
7115 is eliminated. If a function is recursive, there can be many frames for
7116 the same function. The frame for the function in which execution is
7117 actually occurring is called the @dfn{innermost} frame. This is the most
7118 recently created of all the stack frames that still exist.
7120 @cindex frame pointer
7121 Inside your program, stack frames are identified by their addresses. A
7122 stack frame consists of many bytes, each of which has its own address; each
7123 kind of computer has a convention for choosing one byte whose
7124 address serves as the address of the frame. Usually this address is kept
7125 in a register called the @dfn{frame pointer register}
7126 (@pxref{Registers, $fp}) while execution is going on in that frame.
7128 @cindex frame number
7129 @value{GDBN} assigns numbers to all existing stack frames, starting with
7130 zero for the innermost frame, one for the frame that called it,
7131 and so on upward. These numbers do not really exist in your program;
7132 they are assigned by @value{GDBN} to give you a way of designating stack
7133 frames in @value{GDBN} commands.
7135 @c The -fomit-frame-pointer below perennially causes hbox overflow
7136 @c underflow problems.
7137 @cindex frameless execution
7138 Some compilers provide a way to compile functions so that they operate
7139 without stack frames. (For example, the @value{NGCC} option
7141 @samp{-fomit-frame-pointer}
7143 generates functions without a frame.)
7144 This is occasionally done with heavily used library functions to save
7145 the frame setup time. @value{GDBN} has limited facilities for dealing
7146 with these function invocations. If the innermost function invocation
7147 has no stack frame, @value{GDBN} nevertheless regards it as though
7148 it had a separate frame, which is numbered zero as usual, allowing
7149 correct tracing of the function call chain. However, @value{GDBN} has
7150 no provision for frameless functions elsewhere in the stack.
7156 @cindex call stack traces
7157 A backtrace is a summary of how your program got where it is. It shows one
7158 line per frame, for many frames, starting with the currently executing
7159 frame (frame zero), followed by its caller (frame one), and on up the
7162 @anchor{backtrace-command}
7165 @kindex bt @r{(@code{backtrace})}
7168 Print a backtrace of the entire stack: one line per frame for all
7169 frames in the stack.
7171 You can stop the backtrace at any time by typing the system interrupt
7172 character, normally @kbd{Ctrl-c}.
7174 @item backtrace @var{n}
7176 Similar, but print only the innermost @var{n} frames.
7178 @item backtrace -@var{n}
7180 Similar, but print only the outermost @var{n} frames.
7182 @item backtrace full
7184 @itemx bt full @var{n}
7185 @itemx bt full -@var{n}
7186 Print the values of the local variables also. As described above,
7187 @var{n} specifies the number of frames to print.
7189 @item backtrace no-filters
7190 @itemx bt no-filters
7191 @itemx bt no-filters @var{n}
7192 @itemx bt no-filters -@var{n}
7193 @itemx bt no-filters full
7194 @itemx bt no-filters full @var{n}
7195 @itemx bt no-filters full -@var{n}
7196 Do not run Python frame filters on this backtrace. @xref{Frame
7197 Filter API}, for more information. Additionally use @ref{disable
7198 frame-filter all} to turn off all frame filters. This is only
7199 relevant when @value{GDBN} has been configured with @code{Python}
7205 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7206 are additional aliases for @code{backtrace}.
7208 @cindex multiple threads, backtrace
7209 In a multi-threaded program, @value{GDBN} by default shows the
7210 backtrace only for the current thread. To display the backtrace for
7211 several or all of the threads, use the command @code{thread apply}
7212 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7213 apply all backtrace}, @value{GDBN} will display the backtrace for all
7214 the threads; this is handy when you debug a core dump of a
7215 multi-threaded program.
7217 Each line in the backtrace shows the frame number and the function name.
7218 The program counter value is also shown---unless you use @code{set
7219 print address off}. The backtrace also shows the source file name and
7220 line number, as well as the arguments to the function. The program
7221 counter value is omitted if it is at the beginning of the code for that
7224 Here is an example of a backtrace. It was made with the command
7225 @samp{bt 3}, so it shows the innermost three frames.
7229 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7231 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7232 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7234 (More stack frames follow...)
7239 The display for frame zero does not begin with a program counter
7240 value, indicating that your program has stopped at the beginning of the
7241 code for line @code{993} of @code{builtin.c}.
7244 The value of parameter @code{data} in frame 1 has been replaced by
7245 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7246 only if it is a scalar (integer, pointer, enumeration, etc). See command
7247 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7248 on how to configure the way function parameter values are printed.
7250 @cindex optimized out, in backtrace
7251 @cindex function call arguments, optimized out
7252 If your program was compiled with optimizations, some compilers will
7253 optimize away arguments passed to functions if those arguments are
7254 never used after the call. Such optimizations generate code that
7255 passes arguments through registers, but doesn't store those arguments
7256 in the stack frame. @value{GDBN} has no way of displaying such
7257 arguments in stack frames other than the innermost one. Here's what
7258 such a backtrace might look like:
7262 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7264 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7265 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7267 (More stack frames follow...)
7272 The values of arguments that were not saved in their stack frames are
7273 shown as @samp{<optimized out>}.
7275 If you need to display the values of such optimized-out arguments,
7276 either deduce that from other variables whose values depend on the one
7277 you are interested in, or recompile without optimizations.
7279 @cindex backtrace beyond @code{main} function
7280 @cindex program entry point
7281 @cindex startup code, and backtrace
7282 Most programs have a standard user entry point---a place where system
7283 libraries and startup code transition into user code. For C this is
7284 @code{main}@footnote{
7285 Note that embedded programs (the so-called ``free-standing''
7286 environment) are not required to have a @code{main} function as the
7287 entry point. They could even have multiple entry points.}.
7288 When @value{GDBN} finds the entry function in a backtrace
7289 it will terminate the backtrace, to avoid tracing into highly
7290 system-specific (and generally uninteresting) code.
7292 If you need to examine the startup code, or limit the number of levels
7293 in a backtrace, you can change this behavior:
7296 @item set backtrace past-main
7297 @itemx set backtrace past-main on
7298 @kindex set backtrace
7299 Backtraces will continue past the user entry point.
7301 @item set backtrace past-main off
7302 Backtraces will stop when they encounter the user entry point. This is the
7305 @item show backtrace past-main
7306 @kindex show backtrace
7307 Display the current user entry point backtrace policy.
7309 @item set backtrace past-entry
7310 @itemx set backtrace past-entry on
7311 Backtraces will continue past the internal entry point of an application.
7312 This entry point is encoded by the linker when the application is built,
7313 and is likely before the user entry point @code{main} (or equivalent) is called.
7315 @item set backtrace past-entry off
7316 Backtraces will stop when they encounter the internal entry point of an
7317 application. This is the default.
7319 @item show backtrace past-entry
7320 Display the current internal entry point backtrace policy.
7322 @item set backtrace limit @var{n}
7323 @itemx set backtrace limit 0
7324 @itemx set backtrace limit unlimited
7325 @cindex backtrace limit
7326 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7327 or zero means unlimited levels.
7329 @item show backtrace limit
7330 Display the current limit on backtrace levels.
7333 You can control how file names are displayed.
7336 @item set filename-display
7337 @itemx set filename-display relative
7338 @cindex filename-display
7339 Display file names relative to the compilation directory. This is the default.
7341 @item set filename-display basename
7342 Display only basename of a filename.
7344 @item set filename-display absolute
7345 Display an absolute filename.
7347 @item show filename-display
7348 Show the current way to display filenames.
7352 @section Selecting a Frame
7354 Most commands for examining the stack and other data in your program work on
7355 whichever stack frame is selected at the moment. Here are the commands for
7356 selecting a stack frame; all of them finish by printing a brief description
7357 of the stack frame just selected.
7360 @kindex frame@r{, selecting}
7361 @kindex f @r{(@code{frame})}
7364 Select frame number @var{n}. Recall that frame zero is the innermost
7365 (currently executing) frame, frame one is the frame that called the
7366 innermost one, and so on. The highest-numbered frame is the one for
7369 @item frame @var{stack-addr} [ @var{pc-addr} ]
7370 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7371 Select the frame at address @var{stack-addr}. This is useful mainly if the
7372 chaining of stack frames has been damaged by a bug, making it
7373 impossible for @value{GDBN} to assign numbers properly to all frames. In
7374 addition, this can be useful when your program has multiple stacks and
7375 switches between them. The optional @var{pc-addr} can also be given to
7376 specify the value of PC for the stack frame.
7380 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7381 numbers @var{n}, this advances toward the outermost frame, to higher
7382 frame numbers, to frames that have existed longer.
7385 @kindex do @r{(@code{down})}
7387 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7388 positive numbers @var{n}, this advances toward the innermost frame, to
7389 lower frame numbers, to frames that were created more recently.
7390 You may abbreviate @code{down} as @code{do}.
7393 All of these commands end by printing two lines of output describing the
7394 frame. The first line shows the frame number, the function name, the
7395 arguments, and the source file and line number of execution in that
7396 frame. The second line shows the text of that source line.
7404 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7406 10 read_input_file (argv[i]);
7410 After such a printout, the @code{list} command with no arguments
7411 prints ten lines centered on the point of execution in the frame.
7412 You can also edit the program at the point of execution with your favorite
7413 editing program by typing @code{edit}.
7414 @xref{List, ,Printing Source Lines},
7418 @kindex select-frame
7420 The @code{select-frame} command is a variant of @code{frame} that does
7421 not display the new frame after selecting it. This command is
7422 intended primarily for use in @value{GDBN} command scripts, where the
7423 output might be unnecessary and distracting.
7425 @kindex down-silently
7427 @item up-silently @var{n}
7428 @itemx down-silently @var{n}
7429 These two commands are variants of @code{up} and @code{down},
7430 respectively; they differ in that they do their work silently, without
7431 causing display of the new frame. They are intended primarily for use
7432 in @value{GDBN} command scripts, where the output might be unnecessary and
7437 @section Information About a Frame
7439 There are several other commands to print information about the selected
7445 When used without any argument, this command does not change which
7446 frame is selected, but prints a brief description of the currently
7447 selected stack frame. It can be abbreviated @code{f}. With an
7448 argument, this command is used to select a stack frame.
7449 @xref{Selection, ,Selecting a Frame}.
7452 @kindex info f @r{(@code{info frame})}
7455 This command prints a verbose description of the selected stack frame,
7460 the address of the frame
7462 the address of the next frame down (called by this frame)
7464 the address of the next frame up (caller of this frame)
7466 the language in which the source code corresponding to this frame is written
7468 the address of the frame's arguments
7470 the address of the frame's local variables
7472 the program counter saved in it (the address of execution in the caller frame)
7474 which registers were saved in the frame
7477 @noindent The verbose description is useful when
7478 something has gone wrong that has made the stack format fail to fit
7479 the usual conventions.
7481 @item info frame @var{addr}
7482 @itemx info f @var{addr}
7483 Print a verbose description of the frame at address @var{addr}, without
7484 selecting that frame. The selected frame remains unchanged by this
7485 command. This requires the same kind of address (more than one for some
7486 architectures) that you specify in the @code{frame} command.
7487 @xref{Selection, ,Selecting a Frame}.
7491 Print the arguments of the selected frame, each on a separate line.
7495 Print the local variables of the selected frame, each on a separate
7496 line. These are all variables (declared either static or automatic)
7497 accessible at the point of execution of the selected frame.
7501 @node Frame Filter Management
7502 @section Management of Frame Filters.
7503 @cindex managing frame filters
7505 Frame filters are Python based utilities to manage and decorate the
7506 output of frames. @xref{Frame Filter API}, for further information.
7508 Managing frame filters is performed by several commands available
7509 within @value{GDBN}, detailed here.
7512 @kindex info frame-filter
7513 @item info frame-filter
7514 Print a list of installed frame filters from all dictionaries, showing
7515 their name, priority and enabled status.
7517 @kindex disable frame-filter
7518 @anchor{disable frame-filter all}
7519 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7520 Disable a frame filter in the dictionary matching
7521 @var{filter-dictionary} and @var{filter-name}. The
7522 @var{filter-dictionary} may be @code{all}, @code{global},
7523 @code{progspace}, or the name of the object file where the frame filter
7524 dictionary resides. When @code{all} is specified, all frame filters
7525 across all dictionaries are disabled. The @var{filter-name} is the name
7526 of the frame filter and is used when @code{all} is not the option for
7527 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7528 may be enabled again later.
7530 @kindex enable frame-filter
7531 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7532 Enable a frame filter in the dictionary matching
7533 @var{filter-dictionary} and @var{filter-name}. The
7534 @var{filter-dictionary} may be @code{all}, @code{global},
7535 @code{progspace} or the name of the object file where the frame filter
7536 dictionary resides. When @code{all} is specified, all frame filters across
7537 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7538 filter and is used when @code{all} is not the option for
7539 @var{filter-dictionary}.
7544 (gdb) info frame-filter
7546 global frame-filters:
7547 Priority Enabled Name
7548 1000 No PrimaryFunctionFilter
7551 progspace /build/test frame-filters:
7552 Priority Enabled Name
7553 100 Yes ProgspaceFilter
7555 objfile /build/test frame-filters:
7556 Priority Enabled Name
7557 999 Yes BuildProgra Filter
7559 (gdb) disable frame-filter /build/test BuildProgramFilter
7560 (gdb) info frame-filter
7562 global frame-filters:
7563 Priority Enabled Name
7564 1000 No PrimaryFunctionFilter
7567 progspace /build/test frame-filters:
7568 Priority Enabled Name
7569 100 Yes ProgspaceFilter
7571 objfile /build/test frame-filters:
7572 Priority Enabled Name
7573 999 No BuildProgramFilter
7575 (gdb) enable frame-filter global PrimaryFunctionFilter
7576 (gdb) info frame-filter
7578 global frame-filters:
7579 Priority Enabled Name
7580 1000 Yes PrimaryFunctionFilter
7583 progspace /build/test frame-filters:
7584 Priority Enabled Name
7585 100 Yes ProgspaceFilter
7587 objfile /build/test frame-filters:
7588 Priority Enabled Name
7589 999 No BuildProgramFilter
7592 @kindex set frame-filter priority
7593 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7594 Set the @var{priority} of a frame filter in the dictionary matching
7595 @var{filter-dictionary}, and the frame filter name matching
7596 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7597 @code{progspace} or the name of the object file where the frame filter
7598 dictionary resides. The @var{priority} is an integer.
7600 @kindex show frame-filter priority
7601 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7602 Show the @var{priority} of a frame filter in the dictionary matching
7603 @var{filter-dictionary}, and the frame filter name matching
7604 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7605 @code{progspace} or the name of the object file where the frame filter
7611 (gdb) info frame-filter
7613 global frame-filters:
7614 Priority Enabled Name
7615 1000 Yes PrimaryFunctionFilter
7618 progspace /build/test frame-filters:
7619 Priority Enabled Name
7620 100 Yes ProgspaceFilter
7622 objfile /build/test frame-filters:
7623 Priority Enabled Name
7624 999 No BuildProgramFilter
7626 (gdb) set frame-filter priority global Reverse 50
7627 (gdb) info frame-filter
7629 global frame-filters:
7630 Priority Enabled Name
7631 1000 Yes PrimaryFunctionFilter
7634 progspace /build/test frame-filters:
7635 Priority Enabled Name
7636 100 Yes ProgspaceFilter
7638 objfile /build/test frame-filters:
7639 Priority Enabled Name
7640 999 No BuildProgramFilter
7645 @chapter Examining Source Files
7647 @value{GDBN} can print parts of your program's source, since the debugging
7648 information recorded in the program tells @value{GDBN} what source files were
7649 used to build it. When your program stops, @value{GDBN} spontaneously prints
7650 the line where it stopped. Likewise, when you select a stack frame
7651 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7652 execution in that frame has stopped. You can print other portions of
7653 source files by explicit command.
7655 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7656 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7657 @value{GDBN} under @sc{gnu} Emacs}.
7660 * List:: Printing source lines
7661 * Specify Location:: How to specify code locations
7662 * Edit:: Editing source files
7663 * Search:: Searching source files
7664 * Source Path:: Specifying source directories
7665 * Machine Code:: Source and machine code
7669 @section Printing Source Lines
7672 @kindex l @r{(@code{list})}
7673 To print lines from a source file, use the @code{list} command
7674 (abbreviated @code{l}). By default, ten lines are printed.
7675 There are several ways to specify what part of the file you want to
7676 print; see @ref{Specify Location}, for the full list.
7678 Here are the forms of the @code{list} command most commonly used:
7681 @item list @var{linenum}
7682 Print lines centered around line number @var{linenum} in the
7683 current source file.
7685 @item list @var{function}
7686 Print lines centered around the beginning of function
7690 Print more lines. If the last lines printed were printed with a
7691 @code{list} command, this prints lines following the last lines
7692 printed; however, if the last line printed was a solitary line printed
7693 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7694 Stack}), this prints lines centered around that line.
7697 Print lines just before the lines last printed.
7700 @cindex @code{list}, how many lines to display
7701 By default, @value{GDBN} prints ten source lines with any of these forms of
7702 the @code{list} command. You can change this using @code{set listsize}:
7705 @kindex set listsize
7706 @item set listsize @var{count}
7707 @itemx set listsize unlimited
7708 Make the @code{list} command display @var{count} source lines (unless
7709 the @code{list} argument explicitly specifies some other number).
7710 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7712 @kindex show listsize
7714 Display the number of lines that @code{list} prints.
7717 Repeating a @code{list} command with @key{RET} discards the argument,
7718 so it is equivalent to typing just @code{list}. This is more useful
7719 than listing the same lines again. An exception is made for an
7720 argument of @samp{-}; that argument is preserved in repetition so that
7721 each repetition moves up in the source file.
7723 In general, the @code{list} command expects you to supply zero, one or two
7724 @dfn{locations}. Locations specify source lines; there are several ways
7725 of writing them (@pxref{Specify Location}), but the effect is always
7726 to specify some source line.
7728 Here is a complete description of the possible arguments for @code{list}:
7731 @item list @var{location}
7732 Print lines centered around the line specified by @var{location}.
7734 @item list @var{first},@var{last}
7735 Print lines from @var{first} to @var{last}. Both arguments are
7736 locations. When a @code{list} command has two locations, and the
7737 source file of the second location is omitted, this refers to
7738 the same source file as the first location.
7740 @item list ,@var{last}
7741 Print lines ending with @var{last}.
7743 @item list @var{first},
7744 Print lines starting with @var{first}.
7747 Print lines just after the lines last printed.
7750 Print lines just before the lines last printed.
7753 As described in the preceding table.
7756 @node Specify Location
7757 @section Specifying a Location
7758 @cindex specifying location
7760 @cindex source location
7763 * Linespec Locations:: Linespec locations
7764 * Explicit Locations:: Explicit locations
7765 * Address Locations:: Address locations
7768 Several @value{GDBN} commands accept arguments that specify a location
7769 of your program's code. Since @value{GDBN} is a source-level
7770 debugger, a location usually specifies some line in the source code.
7771 Locations may be specified using three different formats:
7772 linespec locations, explicit locations, or address locations.
7774 @node Linespec Locations
7775 @subsection Linespec Locations
7776 @cindex linespec locations
7778 A @dfn{linespec} is a colon-separated list of source location parameters such
7779 as file name, function name, etc. Here are all the different ways of
7780 specifying a linespec:
7784 Specifies the line number @var{linenum} of the current source file.
7787 @itemx +@var{offset}
7788 Specifies the line @var{offset} lines before or after the @dfn{current
7789 line}. For the @code{list} command, the current line is the last one
7790 printed; for the breakpoint commands, this is the line at which
7791 execution stopped in the currently selected @dfn{stack frame}
7792 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7793 used as the second of the two linespecs in a @code{list} command,
7794 this specifies the line @var{offset} lines up or down from the first
7797 @item @var{filename}:@var{linenum}
7798 Specifies the line @var{linenum} in the source file @var{filename}.
7799 If @var{filename} is a relative file name, then it will match any
7800 source file name with the same trailing components. For example, if
7801 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7802 name of @file{/build/trunk/gcc/expr.c}, but not
7803 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7805 @item @var{function}
7806 Specifies the line that begins the body of the function @var{function}.
7807 For example, in C, this is the line with the open brace.
7809 @item @var{function}:@var{label}
7810 Specifies the line where @var{label} appears in @var{function}.
7812 @item @var{filename}:@var{function}
7813 Specifies the line that begins the body of the function @var{function}
7814 in the file @var{filename}. You only need the file name with a
7815 function name to avoid ambiguity when there are identically named
7816 functions in different source files.
7819 Specifies the line at which the label named @var{label} appears
7820 in the function corresponding to the currently selected stack frame.
7821 If there is no current selected stack frame (for instance, if the inferior
7822 is not running), then @value{GDBN} will not search for a label.
7824 @cindex breakpoint at static probe point
7825 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7826 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7827 applications to embed static probes. @xref{Static Probe Points}, for more
7828 information on finding and using static probes. This form of linespec
7829 specifies the location of such a static probe.
7831 If @var{objfile} is given, only probes coming from that shared library
7832 or executable matching @var{objfile} as a regular expression are considered.
7833 If @var{provider} is given, then only probes from that provider are considered.
7834 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7835 each one of those probes.
7838 @node Explicit Locations
7839 @subsection Explicit Locations
7840 @cindex explicit locations
7842 @dfn{Explicit locations} allow the user to directly specify the source
7843 location's parameters using option-value pairs.
7845 Explicit locations are useful when several functions, labels, or
7846 file names have the same name (base name for files) in the program's
7847 sources. In these cases, explicit locations point to the source
7848 line you meant more accurately and unambiguously. Also, using
7849 explicit locations might be faster in large programs.
7851 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7852 defined in the file named @file{foo} or the label @code{bar} in a function
7853 named @code{foo}. @value{GDBN} must search either the file system or
7854 the symbol table to know.
7856 The list of valid explicit location options is summarized in the
7860 @item -source @var{filename}
7861 The value specifies the source file name. To differentiate between
7862 files with the same base name, prepend as many directories as is necessary
7863 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7864 @value{GDBN} will use the first file it finds with the given base
7865 name. This option requires the use of either @code{-function} or @code{-line}.
7867 @item -function @var{function}
7868 The value specifies the name of a function. Operations
7869 on function locations unmodified by other options (such as @code{-label}
7870 or @code{-line}) refer to the line that begins the body of the function.
7871 In C, for example, this is the line with the open brace.
7873 @item -label @var{label}
7874 The value specifies the name of a label. When the function
7875 name is not specified, the label is searched in the function of the currently
7876 selected stack frame.
7878 @item -line @var{number}
7879 The value specifies a line offset for the location. The offset may either
7880 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7881 the command. When specified without any other options, the line offset is
7882 relative to the current line.
7885 Explicit location options may be abbreviated by omitting any non-unique
7886 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7888 @node Address Locations
7889 @subsection Address Locations
7890 @cindex address locations
7892 @dfn{Address locations} indicate a specific program address. They have
7893 the generalized form *@var{address}.
7895 For line-oriented commands, such as @code{list} and @code{edit}, this
7896 specifies a source line that contains @var{address}. For @code{break} and
7897 other breakpoint-oriented commands, this can be used to set breakpoints in
7898 parts of your program which do not have debugging information or
7901 Here @var{address} may be any expression valid in the current working
7902 language (@pxref{Languages, working language}) that specifies a code
7903 address. In addition, as a convenience, @value{GDBN} extends the
7904 semantics of expressions used in locations to cover several situations
7905 that frequently occur during debugging. Here are the various forms
7909 @item @var{expression}
7910 Any expression valid in the current working language.
7912 @item @var{funcaddr}
7913 An address of a function or procedure derived from its name. In C,
7914 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7915 simply the function's name @var{function} (and actually a special case
7916 of a valid expression). In Pascal and Modula-2, this is
7917 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7918 (although the Pascal form also works).
7920 This form specifies the address of the function's first instruction,
7921 before the stack frame and arguments have been set up.
7923 @item '@var{filename}':@var{funcaddr}
7924 Like @var{funcaddr} above, but also specifies the name of the source
7925 file explicitly. This is useful if the name of the function does not
7926 specify the function unambiguously, e.g., if there are several
7927 functions with identical names in different source files.
7931 @section Editing Source Files
7932 @cindex editing source files
7935 @kindex e @r{(@code{edit})}
7936 To edit the lines in a source file, use the @code{edit} command.
7937 The editing program of your choice
7938 is invoked with the current line set to
7939 the active line in the program.
7940 Alternatively, there are several ways to specify what part of the file you
7941 want to print if you want to see other parts of the program:
7944 @item edit @var{location}
7945 Edit the source file specified by @code{location}. Editing starts at
7946 that @var{location}, e.g., at the specified source line of the
7947 specified file. @xref{Specify Location}, for all the possible forms
7948 of the @var{location} argument; here are the forms of the @code{edit}
7949 command most commonly used:
7952 @item edit @var{number}
7953 Edit the current source file with @var{number} as the active line number.
7955 @item edit @var{function}
7956 Edit the file containing @var{function} at the beginning of its definition.
7961 @subsection Choosing your Editor
7962 You can customize @value{GDBN} to use any editor you want
7964 The only restriction is that your editor (say @code{ex}), recognizes the
7965 following command-line syntax:
7967 ex +@var{number} file
7969 The optional numeric value +@var{number} specifies the number of the line in
7970 the file where to start editing.}.
7971 By default, it is @file{@value{EDITOR}}, but you can change this
7972 by setting the environment variable @code{EDITOR} before using
7973 @value{GDBN}. For example, to configure @value{GDBN} to use the
7974 @code{vi} editor, you could use these commands with the @code{sh} shell:
7980 or in the @code{csh} shell,
7982 setenv EDITOR /usr/bin/vi
7987 @section Searching Source Files
7988 @cindex searching source files
7990 There are two commands for searching through the current source file for a
7995 @kindex forward-search
7996 @kindex fo @r{(@code{forward-search})}
7997 @item forward-search @var{regexp}
7998 @itemx search @var{regexp}
7999 The command @samp{forward-search @var{regexp}} checks each line,
8000 starting with the one following the last line listed, for a match for
8001 @var{regexp}. It lists the line that is found. You can use the
8002 synonym @samp{search @var{regexp}} or abbreviate the command name as
8005 @kindex reverse-search
8006 @item reverse-search @var{regexp}
8007 The command @samp{reverse-search @var{regexp}} checks each line, starting
8008 with the one before the last line listed and going backward, for a match
8009 for @var{regexp}. It lists the line that is found. You can abbreviate
8010 this command as @code{rev}.
8014 @section Specifying Source Directories
8017 @cindex directories for source files
8018 Executable programs sometimes do not record the directories of the source
8019 files from which they were compiled, just the names. Even when they do,
8020 the directories could be moved between the compilation and your debugging
8021 session. @value{GDBN} has a list of directories to search for source files;
8022 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8023 it tries all the directories in the list, in the order they are present
8024 in the list, until it finds a file with the desired name.
8026 For example, suppose an executable references the file
8027 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8028 @file{/mnt/cross}. The file is first looked up literally; if this
8029 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8030 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8031 message is printed. @value{GDBN} does not look up the parts of the
8032 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8033 Likewise, the subdirectories of the source path are not searched: if
8034 the source path is @file{/mnt/cross}, and the binary refers to
8035 @file{foo.c}, @value{GDBN} would not find it under
8036 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8038 Plain file names, relative file names with leading directories, file
8039 names containing dots, etc.@: are all treated as described above; for
8040 instance, if the source path is @file{/mnt/cross}, and the source file
8041 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8042 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8043 that---@file{/mnt/cross/foo.c}.
8045 Note that the executable search path is @emph{not} used to locate the
8048 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8049 any information it has cached about where source files are found and where
8050 each line is in the file.
8054 When you start @value{GDBN}, its source path includes only @samp{cdir}
8055 and @samp{cwd}, in that order.
8056 To add other directories, use the @code{directory} command.
8058 The search path is used to find both program source files and @value{GDBN}
8059 script files (read using the @samp{-command} option and @samp{source} command).
8061 In addition to the source path, @value{GDBN} provides a set of commands
8062 that manage a list of source path substitution rules. A @dfn{substitution
8063 rule} specifies how to rewrite source directories stored in the program's
8064 debug information in case the sources were moved to a different
8065 directory between compilation and debugging. A rule is made of
8066 two strings, the first specifying what needs to be rewritten in
8067 the path, and the second specifying how it should be rewritten.
8068 In @ref{set substitute-path}, we name these two parts @var{from} and
8069 @var{to} respectively. @value{GDBN} does a simple string replacement
8070 of @var{from} with @var{to} at the start of the directory part of the
8071 source file name, and uses that result instead of the original file
8072 name to look up the sources.
8074 Using the previous example, suppose the @file{foo-1.0} tree has been
8075 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8076 @value{GDBN} to replace @file{/usr/src} in all source path names with
8077 @file{/mnt/cross}. The first lookup will then be
8078 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8079 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8080 substitution rule, use the @code{set substitute-path} command
8081 (@pxref{set substitute-path}).
8083 To avoid unexpected substitution results, a rule is applied only if the
8084 @var{from} part of the directory name ends at a directory separator.
8085 For instance, a rule substituting @file{/usr/source} into
8086 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8087 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8088 is applied only at the beginning of the directory name, this rule will
8089 not be applied to @file{/root/usr/source/baz.c} either.
8091 In many cases, you can achieve the same result using the @code{directory}
8092 command. However, @code{set substitute-path} can be more efficient in
8093 the case where the sources are organized in a complex tree with multiple
8094 subdirectories. With the @code{directory} command, you need to add each
8095 subdirectory of your project. If you moved the entire tree while
8096 preserving its internal organization, then @code{set substitute-path}
8097 allows you to direct the debugger to all the sources with one single
8100 @code{set substitute-path} is also more than just a shortcut command.
8101 The source path is only used if the file at the original location no
8102 longer exists. On the other hand, @code{set substitute-path} modifies
8103 the debugger behavior to look at the rewritten location instead. So, if
8104 for any reason a source file that is not relevant to your executable is
8105 located at the original location, a substitution rule is the only
8106 method available to point @value{GDBN} at the new location.
8108 @cindex @samp{--with-relocated-sources}
8109 @cindex default source path substitution
8110 You can configure a default source path substitution rule by
8111 configuring @value{GDBN} with the
8112 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8113 should be the name of a directory under @value{GDBN}'s configured
8114 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8115 directory names in debug information under @var{dir} will be adjusted
8116 automatically if the installed @value{GDBN} is moved to a new
8117 location. This is useful if @value{GDBN}, libraries or executables
8118 with debug information and corresponding source code are being moved
8122 @item directory @var{dirname} @dots{}
8123 @item dir @var{dirname} @dots{}
8124 Add directory @var{dirname} to the front of the source path. Several
8125 directory names may be given to this command, separated by @samp{:}
8126 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8127 part of absolute file names) or
8128 whitespace. You may specify a directory that is already in the source
8129 path; this moves it forward, so @value{GDBN} searches it sooner.
8133 @vindex $cdir@r{, convenience variable}
8134 @vindex $cwd@r{, convenience variable}
8135 @cindex compilation directory
8136 @cindex current directory
8137 @cindex working directory
8138 @cindex directory, current
8139 @cindex directory, compilation
8140 You can use the string @samp{$cdir} to refer to the compilation
8141 directory (if one is recorded), and @samp{$cwd} to refer to the current
8142 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8143 tracks the current working directory as it changes during your @value{GDBN}
8144 session, while the latter is immediately expanded to the current
8145 directory at the time you add an entry to the source path.
8148 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8150 @c RET-repeat for @code{directory} is explicitly disabled, but since
8151 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8153 @item set directories @var{path-list}
8154 @kindex set directories
8155 Set the source path to @var{path-list}.
8156 @samp{$cdir:$cwd} are added if missing.
8158 @item show directories
8159 @kindex show directories
8160 Print the source path: show which directories it contains.
8162 @anchor{set substitute-path}
8163 @item set substitute-path @var{from} @var{to}
8164 @kindex set substitute-path
8165 Define a source path substitution rule, and add it at the end of the
8166 current list of existing substitution rules. If a rule with the same
8167 @var{from} was already defined, then the old rule is also deleted.
8169 For example, if the file @file{/foo/bar/baz.c} was moved to
8170 @file{/mnt/cross/baz.c}, then the command
8173 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8177 will tell @value{GDBN} to replace @samp{/foo/bar} with
8178 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8179 @file{baz.c} even though it was moved.
8181 In the case when more than one substitution rule have been defined,
8182 the rules are evaluated one by one in the order where they have been
8183 defined. The first one matching, if any, is selected to perform
8186 For instance, if we had entered the following commands:
8189 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8190 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8194 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8195 @file{/mnt/include/defs.h} by using the first rule. However, it would
8196 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8197 @file{/mnt/src/lib/foo.c}.
8200 @item unset substitute-path [path]
8201 @kindex unset substitute-path
8202 If a path is specified, search the current list of substitution rules
8203 for a rule that would rewrite that path. Delete that rule if found.
8204 A warning is emitted by the debugger if no rule could be found.
8206 If no path is specified, then all substitution rules are deleted.
8208 @item show substitute-path [path]
8209 @kindex show substitute-path
8210 If a path is specified, then print the source path substitution rule
8211 which would rewrite that path, if any.
8213 If no path is specified, then print all existing source path substitution
8218 If your source path is cluttered with directories that are no longer of
8219 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8220 versions of source. You can correct the situation as follows:
8224 Use @code{directory} with no argument to reset the source path to its default value.
8227 Use @code{directory} with suitable arguments to reinstall the
8228 directories you want in the source path. You can add all the
8229 directories in one command.
8233 @section Source and Machine Code
8234 @cindex source line and its code address
8236 You can use the command @code{info line} to map source lines to program
8237 addresses (and vice versa), and the command @code{disassemble} to display
8238 a range of addresses as machine instructions. You can use the command
8239 @code{set disassemble-next-line} to set whether to disassemble next
8240 source line when execution stops. When run under @sc{gnu} Emacs
8241 mode, the @code{info line} command causes the arrow to point to the
8242 line specified. Also, @code{info line} prints addresses in symbolic form as
8247 @item info line @var{location}
8248 Print the starting and ending addresses of the compiled code for
8249 source line @var{location}. You can specify source lines in any of
8250 the ways documented in @ref{Specify Location}.
8253 For example, we can use @code{info line} to discover the location of
8254 the object code for the first line of function
8255 @code{m4_changequote}:
8257 @c FIXME: I think this example should also show the addresses in
8258 @c symbolic form, as they usually would be displayed.
8260 (@value{GDBP}) info line m4_changequote
8261 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8265 @cindex code address and its source line
8266 We can also inquire (using @code{*@var{addr}} as the form for
8267 @var{location}) what source line covers a particular address:
8269 (@value{GDBP}) info line *0x63ff
8270 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8273 @cindex @code{$_} and @code{info line}
8274 @cindex @code{x} command, default address
8275 @kindex x@r{(examine), and} info line
8276 After @code{info line}, the default address for the @code{x} command
8277 is changed to the starting address of the line, so that @samp{x/i} is
8278 sufficient to begin examining the machine code (@pxref{Memory,
8279 ,Examining Memory}). Also, this address is saved as the value of the
8280 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8285 @cindex assembly instructions
8286 @cindex instructions, assembly
8287 @cindex machine instructions
8288 @cindex listing machine instructions
8290 @itemx disassemble /m
8291 @itemx disassemble /s
8292 @itemx disassemble /r
8293 This specialized command dumps a range of memory as machine
8294 instructions. It can also print mixed source+disassembly by specifying
8295 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8296 as well as in symbolic form by specifying the @code{/r} modifier.
8297 The default memory range is the function surrounding the
8298 program counter of the selected frame. A single argument to this
8299 command is a program counter value; @value{GDBN} dumps the function
8300 surrounding this value. When two arguments are given, they should
8301 be separated by a comma, possibly surrounded by whitespace. The
8302 arguments specify a range of addresses to dump, in one of two forms:
8305 @item @var{start},@var{end}
8306 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8307 @item @var{start},+@var{length}
8308 the addresses from @var{start} (inclusive) to
8309 @code{@var{start}+@var{length}} (exclusive).
8313 When 2 arguments are specified, the name of the function is also
8314 printed (since there could be several functions in the given range).
8316 The argument(s) can be any expression yielding a numeric value, such as
8317 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8319 If the range of memory being disassembled contains current program counter,
8320 the instruction at that location is shown with a @code{=>} marker.
8323 The following example shows the disassembly of a range of addresses of
8324 HP PA-RISC 2.0 code:
8327 (@value{GDBP}) disas 0x32c4, 0x32e4
8328 Dump of assembler code from 0x32c4 to 0x32e4:
8329 0x32c4 <main+204>: addil 0,dp
8330 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8331 0x32cc <main+212>: ldil 0x3000,r31
8332 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8333 0x32d4 <main+220>: ldo 0(r31),rp
8334 0x32d8 <main+224>: addil -0x800,dp
8335 0x32dc <main+228>: ldo 0x588(r1),r26
8336 0x32e0 <main+232>: ldil 0x3000,r31
8337 End of assembler dump.
8340 Here is an example showing mixed source+assembly for Intel x86
8341 with @code{/m} or @code{/s}, when the program is stopped just after
8342 function prologue in a non-optimized function with no inline code.
8345 (@value{GDBP}) disas /m main
8346 Dump of assembler code for function main:
8348 0x08048330 <+0>: push %ebp
8349 0x08048331 <+1>: mov %esp,%ebp
8350 0x08048333 <+3>: sub $0x8,%esp
8351 0x08048336 <+6>: and $0xfffffff0,%esp
8352 0x08048339 <+9>: sub $0x10,%esp
8354 6 printf ("Hello.\n");
8355 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8356 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8360 0x08048348 <+24>: mov $0x0,%eax
8361 0x0804834d <+29>: leave
8362 0x0804834e <+30>: ret
8364 End of assembler dump.
8367 The @code{/m} option is deprecated as its output is not useful when
8368 there is either inlined code or re-ordered code.
8369 The @code{/s} option is the preferred choice.
8370 Here is an example for AMD x86-64 showing the difference between
8371 @code{/m} output and @code{/s} output.
8372 This example has one inline function defined in a header file,
8373 and the code is compiled with @samp{-O2} optimization.
8374 Note how the @code{/m} output is missing the disassembly of
8375 several instructions that are present in the @code{/s} output.
8405 (@value{GDBP}) disas /m main
8406 Dump of assembler code for function main:
8410 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8411 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8415 0x000000000040041d <+29>: xor %eax,%eax
8416 0x000000000040041f <+31>: retq
8417 0x0000000000400420 <+32>: add %eax,%eax
8418 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8420 End of assembler dump.
8421 (@value{GDBP}) disas /s main
8422 Dump of assembler code for function main:
8426 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8430 0x0000000000400406 <+6>: test %eax,%eax
8431 0x0000000000400408 <+8>: js 0x400420 <main+32>
8436 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8437 0x000000000040040d <+13>: test %eax,%eax
8438 0x000000000040040f <+15>: mov $0x1,%eax
8439 0x0000000000400414 <+20>: cmovne %edx,%eax
8443 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8447 0x000000000040041d <+29>: xor %eax,%eax
8448 0x000000000040041f <+31>: retq
8452 0x0000000000400420 <+32>: add %eax,%eax
8453 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8454 End of assembler dump.
8457 Here is another example showing raw instructions in hex for AMD x86-64,
8460 (gdb) disas /r 0x400281,+10
8461 Dump of assembler code from 0x400281 to 0x40028b:
8462 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8463 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8464 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8465 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8466 End of assembler dump.
8469 Addresses cannot be specified as a location (@pxref{Specify Location}).
8470 So, for example, if you want to disassemble function @code{bar}
8471 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8472 and not @samp{disassemble foo.c:bar}.
8474 Some architectures have more than one commonly-used set of instruction
8475 mnemonics or other syntax.
8477 For programs that were dynamically linked and use shared libraries,
8478 instructions that call functions or branch to locations in the shared
8479 libraries might show a seemingly bogus location---it's actually a
8480 location of the relocation table. On some architectures, @value{GDBN}
8481 might be able to resolve these to actual function names.
8484 @kindex set disassembly-flavor
8485 @cindex Intel disassembly flavor
8486 @cindex AT&T disassembly flavor
8487 @item set disassembly-flavor @var{instruction-set}
8488 Select the instruction set to use when disassembling the
8489 program via the @code{disassemble} or @code{x/i} commands.
8491 Currently this command is only defined for the Intel x86 family. You
8492 can set @var{instruction-set} to either @code{intel} or @code{att}.
8493 The default is @code{att}, the AT&T flavor used by default by Unix
8494 assemblers for x86-based targets.
8496 @kindex show disassembly-flavor
8497 @item show disassembly-flavor
8498 Show the current setting of the disassembly flavor.
8502 @kindex set disassemble-next-line
8503 @kindex show disassemble-next-line
8504 @item set disassemble-next-line
8505 @itemx show disassemble-next-line
8506 Control whether or not @value{GDBN} will disassemble the next source
8507 line or instruction when execution stops. If ON, @value{GDBN} will
8508 display disassembly of the next source line when execution of the
8509 program being debugged stops. This is @emph{in addition} to
8510 displaying the source line itself, which @value{GDBN} always does if
8511 possible. If the next source line cannot be displayed for some reason
8512 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8513 info in the debug info), @value{GDBN} will display disassembly of the
8514 next @emph{instruction} instead of showing the next source line. If
8515 AUTO, @value{GDBN} will display disassembly of next instruction only
8516 if the source line cannot be displayed. This setting causes
8517 @value{GDBN} to display some feedback when you step through a function
8518 with no line info or whose source file is unavailable. The default is
8519 OFF, which means never display the disassembly of the next line or
8525 @chapter Examining Data
8527 @cindex printing data
8528 @cindex examining data
8531 The usual way to examine data in your program is with the @code{print}
8532 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8533 evaluates and prints the value of an expression of the language your
8534 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8535 Different Languages}). It may also print the expression using a
8536 Python-based pretty-printer (@pxref{Pretty Printing}).
8539 @item print @var{expr}
8540 @itemx print /@var{f} @var{expr}
8541 @var{expr} is an expression (in the source language). By default the
8542 value of @var{expr} is printed in a format appropriate to its data type;
8543 you can choose a different format by specifying @samp{/@var{f}}, where
8544 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8548 @itemx print /@var{f}
8549 @cindex reprint the last value
8550 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8551 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8552 conveniently inspect the same value in an alternative format.
8555 A more low-level way of examining data is with the @code{x} command.
8556 It examines data in memory at a specified address and prints it in a
8557 specified format. @xref{Memory, ,Examining Memory}.
8559 If you are interested in information about types, or about how the
8560 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8561 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8564 @cindex exploring hierarchical data structures
8566 Another way of examining values of expressions and type information is
8567 through the Python extension command @code{explore} (available only if
8568 the @value{GDBN} build is configured with @code{--with-python}). It
8569 offers an interactive way to start at the highest level (or, the most
8570 abstract level) of the data type of an expression (or, the data type
8571 itself) and explore all the way down to leaf scalar values/fields
8572 embedded in the higher level data types.
8575 @item explore @var{arg}
8576 @var{arg} is either an expression (in the source language), or a type
8577 visible in the current context of the program being debugged.
8580 The working of the @code{explore} command can be illustrated with an
8581 example. If a data type @code{struct ComplexStruct} is defined in your
8591 struct ComplexStruct
8593 struct SimpleStruct *ss_p;
8599 followed by variable declarations as
8602 struct SimpleStruct ss = @{ 10, 1.11 @};
8603 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8607 then, the value of the variable @code{cs} can be explored using the
8608 @code{explore} command as follows.
8612 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8613 the following fields:
8615 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8616 arr = <Enter 1 to explore this field of type `int [10]'>
8618 Enter the field number of choice:
8622 Since the fields of @code{cs} are not scalar values, you are being
8623 prompted to chose the field you want to explore. Let's say you choose
8624 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8625 pointer, you will be asked if it is pointing to a single value. From
8626 the declaration of @code{cs} above, it is indeed pointing to a single
8627 value, hence you enter @code{y}. If you enter @code{n}, then you will
8628 be asked if it were pointing to an array of values, in which case this
8629 field will be explored as if it were an array.
8632 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8633 Continue exploring it as a pointer to a single value [y/n]: y
8634 The value of `*(cs.ss_p)' is a struct/class of type `struct
8635 SimpleStruct' with the following fields:
8637 i = 10 .. (Value of type `int')
8638 d = 1.1100000000000001 .. (Value of type `double')
8640 Press enter to return to parent value:
8644 If the field @code{arr} of @code{cs} was chosen for exploration by
8645 entering @code{1} earlier, then since it is as array, you will be
8646 prompted to enter the index of the element in the array that you want
8650 `cs.arr' is an array of `int'.
8651 Enter the index of the element you want to explore in `cs.arr': 5
8653 `(cs.arr)[5]' is a scalar value of type `int'.
8657 Press enter to return to parent value:
8660 In general, at any stage of exploration, you can go deeper towards the
8661 leaf values by responding to the prompts appropriately, or hit the
8662 return key to return to the enclosing data structure (the @i{higher}
8663 level data structure).
8665 Similar to exploring values, you can use the @code{explore} command to
8666 explore types. Instead of specifying a value (which is typically a
8667 variable name or an expression valid in the current context of the
8668 program being debugged), you specify a type name. If you consider the
8669 same example as above, your can explore the type
8670 @code{struct ComplexStruct} by passing the argument
8671 @code{struct ComplexStruct} to the @code{explore} command.
8674 (gdb) explore struct ComplexStruct
8678 By responding to the prompts appropriately in the subsequent interactive
8679 session, you can explore the type @code{struct ComplexStruct} in a
8680 manner similar to how the value @code{cs} was explored in the above
8683 The @code{explore} command also has two sub-commands,
8684 @code{explore value} and @code{explore type}. The former sub-command is
8685 a way to explicitly specify that value exploration of the argument is
8686 being invoked, while the latter is a way to explicitly specify that type
8687 exploration of the argument is being invoked.
8690 @item explore value @var{expr}
8691 @cindex explore value
8692 This sub-command of @code{explore} explores the value of the
8693 expression @var{expr} (if @var{expr} is an expression valid in the
8694 current context of the program being debugged). The behavior of this
8695 command is identical to that of the behavior of the @code{explore}
8696 command being passed the argument @var{expr}.
8698 @item explore type @var{arg}
8699 @cindex explore type
8700 This sub-command of @code{explore} explores the type of @var{arg} (if
8701 @var{arg} is a type visible in the current context of program being
8702 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8703 is an expression valid in the current context of the program being
8704 debugged). If @var{arg} is a type, then the behavior of this command is
8705 identical to that of the @code{explore} command being passed the
8706 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8707 this command will be identical to that of the @code{explore} command
8708 being passed the type of @var{arg} as the argument.
8712 * Expressions:: Expressions
8713 * Ambiguous Expressions:: Ambiguous Expressions
8714 * Variables:: Program variables
8715 * Arrays:: Artificial arrays
8716 * Output Formats:: Output formats
8717 * Memory:: Examining memory
8718 * Auto Display:: Automatic display
8719 * Print Settings:: Print settings
8720 * Pretty Printing:: Python pretty printing
8721 * Value History:: Value history
8722 * Convenience Vars:: Convenience variables
8723 * Convenience Funs:: Convenience functions
8724 * Registers:: Registers
8725 * Floating Point Hardware:: Floating point hardware
8726 * Vector Unit:: Vector Unit
8727 * OS Information:: Auxiliary data provided by operating system
8728 * Memory Region Attributes:: Memory region attributes
8729 * Dump/Restore Files:: Copy between memory and a file
8730 * Core File Generation:: Cause a program dump its core
8731 * Character Sets:: Debugging programs that use a different
8732 character set than GDB does
8733 * Caching Target Data:: Data caching for targets
8734 * Searching Memory:: Searching memory for a sequence of bytes
8735 * Value Sizes:: Managing memory allocated for values
8739 @section Expressions
8742 @code{print} and many other @value{GDBN} commands accept an expression and
8743 compute its value. Any kind of constant, variable or operator defined
8744 by the programming language you are using is valid in an expression in
8745 @value{GDBN}. This includes conditional expressions, function calls,
8746 casts, and string constants. It also includes preprocessor macros, if
8747 you compiled your program to include this information; see
8750 @cindex arrays in expressions
8751 @value{GDBN} supports array constants in expressions input by
8752 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8753 you can use the command @code{print @{1, 2, 3@}} to create an array
8754 of three integers. If you pass an array to a function or assign it
8755 to a program variable, @value{GDBN} copies the array to memory that
8756 is @code{malloc}ed in the target program.
8758 Because C is so widespread, most of the expressions shown in examples in
8759 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8760 Languages}, for information on how to use expressions in other
8763 In this section, we discuss operators that you can use in @value{GDBN}
8764 expressions regardless of your programming language.
8766 @cindex casts, in expressions
8767 Casts are supported in all languages, not just in C, because it is so
8768 useful to cast a number into a pointer in order to examine a structure
8769 at that address in memory.
8770 @c FIXME: casts supported---Mod2 true?
8772 @value{GDBN} supports these operators, in addition to those common
8773 to programming languages:
8777 @samp{@@} is a binary operator for treating parts of memory as arrays.
8778 @xref{Arrays, ,Artificial Arrays}, for more information.
8781 @samp{::} allows you to specify a variable in terms of the file or
8782 function where it is defined. @xref{Variables, ,Program Variables}.
8784 @cindex @{@var{type}@}
8785 @cindex type casting memory
8786 @cindex memory, viewing as typed object
8787 @cindex casts, to view memory
8788 @item @{@var{type}@} @var{addr}
8789 Refers to an object of type @var{type} stored at address @var{addr} in
8790 memory. The address @var{addr} may be any expression whose value is
8791 an integer or pointer (but parentheses are required around binary
8792 operators, just as in a cast). This construct is allowed regardless
8793 of what kind of data is normally supposed to reside at @var{addr}.
8796 @node Ambiguous Expressions
8797 @section Ambiguous Expressions
8798 @cindex ambiguous expressions
8800 Expressions can sometimes contain some ambiguous elements. For instance,
8801 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8802 a single function name to be defined several times, for application in
8803 different contexts. This is called @dfn{overloading}. Another example
8804 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8805 templates and is typically instantiated several times, resulting in
8806 the same function name being defined in different contexts.
8808 In some cases and depending on the language, it is possible to adjust
8809 the expression to remove the ambiguity. For instance in C@t{++}, you
8810 can specify the signature of the function you want to break on, as in
8811 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8812 qualified name of your function often makes the expression unambiguous
8815 When an ambiguity that needs to be resolved is detected, the debugger
8816 has the capability to display a menu of numbered choices for each
8817 possibility, and then waits for the selection with the prompt @samp{>}.
8818 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8819 aborts the current command. If the command in which the expression was
8820 used allows more than one choice to be selected, the next option in the
8821 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8824 For example, the following session excerpt shows an attempt to set a
8825 breakpoint at the overloaded symbol @code{String::after}.
8826 We choose three particular definitions of that function name:
8828 @c FIXME! This is likely to change to show arg type lists, at least
8831 (@value{GDBP}) b String::after
8834 [2] file:String.cc; line number:867
8835 [3] file:String.cc; line number:860
8836 [4] file:String.cc; line number:875
8837 [5] file:String.cc; line number:853
8838 [6] file:String.cc; line number:846
8839 [7] file:String.cc; line number:735
8841 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8842 Breakpoint 2 at 0xb344: file String.cc, line 875.
8843 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8844 Multiple breakpoints were set.
8845 Use the "delete" command to delete unwanted
8852 @kindex set multiple-symbols
8853 @item set multiple-symbols @var{mode}
8854 @cindex multiple-symbols menu
8856 This option allows you to adjust the debugger behavior when an expression
8859 By default, @var{mode} is set to @code{all}. If the command with which
8860 the expression is used allows more than one choice, then @value{GDBN}
8861 automatically selects all possible choices. For instance, inserting
8862 a breakpoint on a function using an ambiguous name results in a breakpoint
8863 inserted on each possible match. However, if a unique choice must be made,
8864 then @value{GDBN} uses the menu to help you disambiguate the expression.
8865 For instance, printing the address of an overloaded function will result
8866 in the use of the menu.
8868 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8869 when an ambiguity is detected.
8871 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8872 an error due to the ambiguity and the command is aborted.
8874 @kindex show multiple-symbols
8875 @item show multiple-symbols
8876 Show the current value of the @code{multiple-symbols} setting.
8880 @section Program Variables
8882 The most common kind of expression to use is the name of a variable
8885 Variables in expressions are understood in the selected stack frame
8886 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8890 global (or file-static)
8897 visible according to the scope rules of the
8898 programming language from the point of execution in that frame
8901 @noindent This means that in the function
8916 you can examine and use the variable @code{a} whenever your program is
8917 executing within the function @code{foo}, but you can only use or
8918 examine the variable @code{b} while your program is executing inside
8919 the block where @code{b} is declared.
8921 @cindex variable name conflict
8922 There is an exception: you can refer to a variable or function whose
8923 scope is a single source file even if the current execution point is not
8924 in this file. But it is possible to have more than one such variable or
8925 function with the same name (in different source files). If that
8926 happens, referring to that name has unpredictable effects. If you wish,
8927 you can specify a static variable in a particular function or file by
8928 using the colon-colon (@code{::}) notation:
8930 @cindex colon-colon, context for variables/functions
8932 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8933 @cindex @code{::}, context for variables/functions
8936 @var{file}::@var{variable}
8937 @var{function}::@var{variable}
8941 Here @var{file} or @var{function} is the name of the context for the
8942 static @var{variable}. In the case of file names, you can use quotes to
8943 make sure @value{GDBN} parses the file name as a single word---for example,
8944 to print a global value of @code{x} defined in @file{f2.c}:
8947 (@value{GDBP}) p 'f2.c'::x
8950 The @code{::} notation is normally used for referring to
8951 static variables, since you typically disambiguate uses of local variables
8952 in functions by selecting the appropriate frame and using the
8953 simple name of the variable. However, you may also use this notation
8954 to refer to local variables in frames enclosing the selected frame:
8963 process (a); /* Stop here */
8974 For example, if there is a breakpoint at the commented line,
8975 here is what you might see
8976 when the program stops after executing the call @code{bar(0)}:
8981 (@value{GDBP}) p bar::a
8984 #2 0x080483d0 in foo (a=5) at foobar.c:12
8987 (@value{GDBP}) p bar::a
8991 @cindex C@t{++} scope resolution
8992 These uses of @samp{::} are very rarely in conflict with the very
8993 similar use of the same notation in C@t{++}. When they are in
8994 conflict, the C@t{++} meaning takes precedence; however, this can be
8995 overridden by quoting the file or function name with single quotes.
8997 For example, suppose the program is stopped in a method of a class
8998 that has a field named @code{includefile}, and there is also an
8999 include file named @file{includefile} that defines a variable,
9003 (@value{GDBP}) p includefile
9005 (@value{GDBP}) p includefile::some_global
9006 A syntax error in expression, near `'.
9007 (@value{GDBP}) p 'includefile'::some_global
9011 @cindex wrong values
9012 @cindex variable values, wrong
9013 @cindex function entry/exit, wrong values of variables
9014 @cindex optimized code, wrong values of variables
9016 @emph{Warning:} Occasionally, a local variable may appear to have the
9017 wrong value at certain points in a function---just after entry to a new
9018 scope, and just before exit.
9020 You may see this problem when you are stepping by machine instructions.
9021 This is because, on most machines, it takes more than one instruction to
9022 set up a stack frame (including local variable definitions); if you are
9023 stepping by machine instructions, variables may appear to have the wrong
9024 values until the stack frame is completely built. On exit, it usually
9025 also takes more than one machine instruction to destroy a stack frame;
9026 after you begin stepping through that group of instructions, local
9027 variable definitions may be gone.
9029 This may also happen when the compiler does significant optimizations.
9030 To be sure of always seeing accurate values, turn off all optimization
9033 @cindex ``No symbol "foo" in current context''
9034 Another possible effect of compiler optimizations is to optimize
9035 unused variables out of existence, or assign variables to registers (as
9036 opposed to memory addresses). Depending on the support for such cases
9037 offered by the debug info format used by the compiler, @value{GDBN}
9038 might not be able to display values for such local variables. If that
9039 happens, @value{GDBN} will print a message like this:
9042 No symbol "foo" in current context.
9045 To solve such problems, either recompile without optimizations, or use a
9046 different debug info format, if the compiler supports several such
9047 formats. @xref{Compilation}, for more information on choosing compiler
9048 options. @xref{C, ,C and C@t{++}}, for more information about debug
9049 info formats that are best suited to C@t{++} programs.
9051 If you ask to print an object whose contents are unknown to
9052 @value{GDBN}, e.g., because its data type is not completely specified
9053 by the debug information, @value{GDBN} will say @samp{<incomplete
9054 type>}. @xref{Symbols, incomplete type}, for more about this.
9056 If you append @kbd{@@entry} string to a function parameter name you get its
9057 value at the time the function got called. If the value is not available an
9058 error message is printed. Entry values are available only with some compilers.
9059 Entry values are normally also printed at the function parameter list according
9060 to @ref{set print entry-values}.
9063 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9069 (gdb) print i@@entry
9073 Strings are identified as arrays of @code{char} values without specified
9074 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9075 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9076 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9077 defines literal string type @code{"char"} as @code{char} without a sign.
9082 signed char var1[] = "A";
9085 You get during debugging
9090 $2 = @{65 'A', 0 '\0'@}
9094 @section Artificial Arrays
9096 @cindex artificial array
9098 @kindex @@@r{, referencing memory as an array}
9099 It is often useful to print out several successive objects of the
9100 same type in memory; a section of an array, or an array of
9101 dynamically determined size for which only a pointer exists in the
9104 You can do this by referring to a contiguous span of memory as an
9105 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9106 operand of @samp{@@} should be the first element of the desired array
9107 and be an individual object. The right operand should be the desired length
9108 of the array. The result is an array value whose elements are all of
9109 the type of the left argument. The first element is actually the left
9110 argument; the second element comes from bytes of memory immediately
9111 following those that hold the first element, and so on. Here is an
9112 example. If a program says
9115 int *array = (int *) malloc (len * sizeof (int));
9119 you can print the contents of @code{array} with
9125 The left operand of @samp{@@} must reside in memory. Array values made
9126 with @samp{@@} in this way behave just like other arrays in terms of
9127 subscripting, and are coerced to pointers when used in expressions.
9128 Artificial arrays most often appear in expressions via the value history
9129 (@pxref{Value History, ,Value History}), after printing one out.
9131 Another way to create an artificial array is to use a cast.
9132 This re-interprets a value as if it were an array.
9133 The value need not be in memory:
9135 (@value{GDBP}) p/x (short[2])0x12345678
9136 $1 = @{0x1234, 0x5678@}
9139 As a convenience, if you leave the array length out (as in
9140 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9141 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9143 (@value{GDBP}) p/x (short[])0x12345678
9144 $2 = @{0x1234, 0x5678@}
9147 Sometimes the artificial array mechanism is not quite enough; in
9148 moderately complex data structures, the elements of interest may not
9149 actually be adjacent---for example, if you are interested in the values
9150 of pointers in an array. One useful work-around in this situation is
9151 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9152 Variables}) as a counter in an expression that prints the first
9153 interesting value, and then repeat that expression via @key{RET}. For
9154 instance, suppose you have an array @code{dtab} of pointers to
9155 structures, and you are interested in the values of a field @code{fv}
9156 in each structure. Here is an example of what you might type:
9166 @node Output Formats
9167 @section Output Formats
9169 @cindex formatted output
9170 @cindex output formats
9171 By default, @value{GDBN} prints a value according to its data type. Sometimes
9172 this is not what you want. For example, you might want to print a number
9173 in hex, or a pointer in decimal. Or you might want to view data in memory
9174 at a certain address as a character string or as an instruction. To do
9175 these things, specify an @dfn{output format} when you print a value.
9177 The simplest use of output formats is to say how to print a value
9178 already computed. This is done by starting the arguments of the
9179 @code{print} command with a slash and a format letter. The format
9180 letters supported are:
9184 Regard the bits of the value as an integer, and print the integer in
9188 Print as integer in signed decimal.
9191 Print as integer in unsigned decimal.
9194 Print as integer in octal.
9197 Print as integer in binary. The letter @samp{t} stands for ``two''.
9198 @footnote{@samp{b} cannot be used because these format letters are also
9199 used with the @code{x} command, where @samp{b} stands for ``byte'';
9200 see @ref{Memory,,Examining Memory}.}
9203 @cindex unknown address, locating
9204 @cindex locate address
9205 Print as an address, both absolute in hexadecimal and as an offset from
9206 the nearest preceding symbol. You can use this format used to discover
9207 where (in what function) an unknown address is located:
9210 (@value{GDBP}) p/a 0x54320
9211 $3 = 0x54320 <_initialize_vx+396>
9215 The command @code{info symbol 0x54320} yields similar results.
9216 @xref{Symbols, info symbol}.
9219 Regard as an integer and print it as a character constant. This
9220 prints both the numerical value and its character representation. The
9221 character representation is replaced with the octal escape @samp{\nnn}
9222 for characters outside the 7-bit @sc{ascii} range.
9224 Without this format, @value{GDBN} displays @code{char},
9225 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9226 constants. Single-byte members of vectors are displayed as integer
9230 Regard the bits of the value as a floating point number and print
9231 using typical floating point syntax.
9234 @cindex printing strings
9235 @cindex printing byte arrays
9236 Regard as a string, if possible. With this format, pointers to single-byte
9237 data are displayed as null-terminated strings and arrays of single-byte data
9238 are displayed as fixed-length strings. Other values are displayed in their
9241 Without this format, @value{GDBN} displays pointers to and arrays of
9242 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9243 strings. Single-byte members of a vector are displayed as an integer
9247 Like @samp{x} formatting, the value is treated as an integer and
9248 printed as hexadecimal, but leading zeros are printed to pad the value
9249 to the size of the integer type.
9252 @cindex raw printing
9253 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9254 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9255 Printing}). This typically results in a higher-level display of the
9256 value's contents. The @samp{r} format bypasses any Python
9257 pretty-printer which might exist.
9260 For example, to print the program counter in hex (@pxref{Registers}), type
9267 Note that no space is required before the slash; this is because command
9268 names in @value{GDBN} cannot contain a slash.
9270 To reprint the last value in the value history with a different format,
9271 you can use the @code{print} command with just a format and no
9272 expression. For example, @samp{p/x} reprints the last value in hex.
9275 @section Examining Memory
9277 You can use the command @code{x} (for ``examine'') to examine memory in
9278 any of several formats, independently of your program's data types.
9280 @cindex examining memory
9282 @kindex x @r{(examine memory)}
9283 @item x/@var{nfu} @var{addr}
9286 Use the @code{x} command to examine memory.
9289 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9290 much memory to display and how to format it; @var{addr} is an
9291 expression giving the address where you want to start displaying memory.
9292 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9293 Several commands set convenient defaults for @var{addr}.
9296 @item @var{n}, the repeat count
9297 The repeat count is a decimal integer; the default is 1. It specifies
9298 how much memory (counting by units @var{u}) to display.
9299 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9302 @item @var{f}, the display format
9303 The display format is one of the formats used by @code{print}
9304 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9305 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9306 The default is @samp{x} (hexadecimal) initially. The default changes
9307 each time you use either @code{x} or @code{print}.
9309 @item @var{u}, the unit size
9310 The unit size is any of
9316 Halfwords (two bytes).
9318 Words (four bytes). This is the initial default.
9320 Giant words (eight bytes).
9323 Each time you specify a unit size with @code{x}, that size becomes the
9324 default unit the next time you use @code{x}. For the @samp{i} format,
9325 the unit size is ignored and is normally not written. For the @samp{s} format,
9326 the unit size defaults to @samp{b}, unless it is explicitly given.
9327 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9328 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9329 Note that the results depend on the programming language of the
9330 current compilation unit. If the language is C, the @samp{s}
9331 modifier will use the UTF-16 encoding while @samp{w} will use
9332 UTF-32. The encoding is set by the programming language and cannot
9335 @item @var{addr}, starting display address
9336 @var{addr} is the address where you want @value{GDBN} to begin displaying
9337 memory. The expression need not have a pointer value (though it may);
9338 it is always interpreted as an integer address of a byte of memory.
9339 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9340 @var{addr} is usually just after the last address examined---but several
9341 other commands also set the default address: @code{info breakpoints} (to
9342 the address of the last breakpoint listed), @code{info line} (to the
9343 starting address of a line), and @code{print} (if you use it to display
9344 a value from memory).
9347 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9348 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9349 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9350 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9351 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9353 Since the letters indicating unit sizes are all distinct from the
9354 letters specifying output formats, you do not have to remember whether
9355 unit size or format comes first; either order works. The output
9356 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9357 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9359 Even though the unit size @var{u} is ignored for the formats @samp{s}
9360 and @samp{i}, you might still want to use a count @var{n}; for example,
9361 @samp{3i} specifies that you want to see three machine instructions,
9362 including any operands. For convenience, especially when used with
9363 the @code{display} command, the @samp{i} format also prints branch delay
9364 slot instructions, if any, beyond the count specified, which immediately
9365 follow the last instruction that is within the count. The command
9366 @code{disassemble} gives an alternative way of inspecting machine
9367 instructions; see @ref{Machine Code,,Source and Machine Code}.
9369 All the defaults for the arguments to @code{x} are designed to make it
9370 easy to continue scanning memory with minimal specifications each time
9371 you use @code{x}. For example, after you have inspected three machine
9372 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9373 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9374 the repeat count @var{n} is used again; the other arguments default as
9375 for successive uses of @code{x}.
9377 When examining machine instructions, the instruction at current program
9378 counter is shown with a @code{=>} marker. For example:
9381 (@value{GDBP}) x/5i $pc-6
9382 0x804837f <main+11>: mov %esp,%ebp
9383 0x8048381 <main+13>: push %ecx
9384 0x8048382 <main+14>: sub $0x4,%esp
9385 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9386 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9389 @cindex @code{$_}, @code{$__}, and value history
9390 The addresses and contents printed by the @code{x} command are not saved
9391 in the value history because there is often too much of them and they
9392 would get in the way. Instead, @value{GDBN} makes these values available for
9393 subsequent use in expressions as values of the convenience variables
9394 @code{$_} and @code{$__}. After an @code{x} command, the last address
9395 examined is available for use in expressions in the convenience variable
9396 @code{$_}. The contents of that address, as examined, are available in
9397 the convenience variable @code{$__}.
9399 If the @code{x} command has a repeat count, the address and contents saved
9400 are from the last memory unit printed; this is not the same as the last
9401 address printed if several units were printed on the last line of output.
9403 @anchor{addressable memory unit}
9404 @cindex addressable memory unit
9405 Most targets have an addressable memory unit size of 8 bits. This means
9406 that to each memory address are associated 8 bits of data. Some
9407 targets, however, have other addressable memory unit sizes.
9408 Within @value{GDBN} and this document, the term
9409 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9410 when explicitly referring to a chunk of data of that size. The word
9411 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9412 the addressable memory unit size of the target. For most systems,
9413 addressable memory unit is a synonym of byte.
9415 @cindex remote memory comparison
9416 @cindex target memory comparison
9417 @cindex verify remote memory image
9418 @cindex verify target memory image
9419 When you are debugging a program running on a remote target machine
9420 (@pxref{Remote Debugging}), you may wish to verify the program's image
9421 in the remote machine's memory against the executable file you
9422 downloaded to the target. Or, on any target, you may want to check
9423 whether the program has corrupted its own read-only sections. The
9424 @code{compare-sections} command is provided for such situations.
9427 @kindex compare-sections
9428 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9429 Compare the data of a loadable section @var{section-name} in the
9430 executable file of the program being debugged with the same section in
9431 the target machine's memory, and report any mismatches. With no
9432 arguments, compares all loadable sections. With an argument of
9433 @code{-r}, compares all loadable read-only sections.
9435 Note: for remote targets, this command can be accelerated if the
9436 target supports computing the CRC checksum of a block of memory
9437 (@pxref{qCRC packet}).
9441 @section Automatic Display
9442 @cindex automatic display
9443 @cindex display of expressions
9445 If you find that you want to print the value of an expression frequently
9446 (to see how it changes), you might want to add it to the @dfn{automatic
9447 display list} so that @value{GDBN} prints its value each time your program stops.
9448 Each expression added to the list is given a number to identify it;
9449 to remove an expression from the list, you specify that number.
9450 The automatic display looks like this:
9454 3: bar[5] = (struct hack *) 0x3804
9458 This display shows item numbers, expressions and their current values. As with
9459 displays you request manually using @code{x} or @code{print}, you can
9460 specify the output format you prefer; in fact, @code{display} decides
9461 whether to use @code{print} or @code{x} depending your format
9462 specification---it uses @code{x} if you specify either the @samp{i}
9463 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9467 @item display @var{expr}
9468 Add the expression @var{expr} to the list of expressions to display
9469 each time your program stops. @xref{Expressions, ,Expressions}.
9471 @code{display} does not repeat if you press @key{RET} again after using it.
9473 @item display/@var{fmt} @var{expr}
9474 For @var{fmt} specifying only a display format and not a size or
9475 count, add the expression @var{expr} to the auto-display list but
9476 arrange to display it each time in the specified format @var{fmt}.
9477 @xref{Output Formats,,Output Formats}.
9479 @item display/@var{fmt} @var{addr}
9480 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9481 number of units, add the expression @var{addr} as a memory address to
9482 be examined each time your program stops. Examining means in effect
9483 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9486 For example, @samp{display/i $pc} can be helpful, to see the machine
9487 instruction about to be executed each time execution stops (@samp{$pc}
9488 is a common name for the program counter; @pxref{Registers, ,Registers}).
9491 @kindex delete display
9493 @item undisplay @var{dnums}@dots{}
9494 @itemx delete display @var{dnums}@dots{}
9495 Remove items from the list of expressions to display. Specify the
9496 numbers of the displays that you want affected with the command
9497 argument @var{dnums}. It can be a single display number, one of the
9498 numbers shown in the first field of the @samp{info display} display;
9499 or it could be a range of display numbers, as in @code{2-4}.
9501 @code{undisplay} does not repeat if you press @key{RET} after using it.
9502 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9504 @kindex disable display
9505 @item disable display @var{dnums}@dots{}
9506 Disable the display of item numbers @var{dnums}. A disabled display
9507 item is not printed automatically, but is not forgotten. It may be
9508 enabled again later. Specify the numbers of the displays that you
9509 want affected with the command argument @var{dnums}. It can be a
9510 single display number, one of the numbers shown in the first field of
9511 the @samp{info display} display; or it could be a range of display
9512 numbers, as in @code{2-4}.
9514 @kindex enable display
9515 @item enable display @var{dnums}@dots{}
9516 Enable display of item numbers @var{dnums}. It becomes effective once
9517 again in auto display of its expression, until you specify otherwise.
9518 Specify the numbers of the displays that you want affected with the
9519 command argument @var{dnums}. It can be a single display number, one
9520 of the numbers shown in the first field of the @samp{info display}
9521 display; or it could be a range of display numbers, as in @code{2-4}.
9524 Display the current values of the expressions on the list, just as is
9525 done when your program stops.
9527 @kindex info display
9529 Print the list of expressions previously set up to display
9530 automatically, each one with its item number, but without showing the
9531 values. This includes disabled expressions, which are marked as such.
9532 It also includes expressions which would not be displayed right now
9533 because they refer to automatic variables not currently available.
9536 @cindex display disabled out of scope
9537 If a display expression refers to local variables, then it does not make
9538 sense outside the lexical context for which it was set up. Such an
9539 expression is disabled when execution enters a context where one of its
9540 variables is not defined. For example, if you give the command
9541 @code{display last_char} while inside a function with an argument
9542 @code{last_char}, @value{GDBN} displays this argument while your program
9543 continues to stop inside that function. When it stops elsewhere---where
9544 there is no variable @code{last_char}---the display is disabled
9545 automatically. The next time your program stops where @code{last_char}
9546 is meaningful, you can enable the display expression once again.
9548 @node Print Settings
9549 @section Print Settings
9551 @cindex format options
9552 @cindex print settings
9553 @value{GDBN} provides the following ways to control how arrays, structures,
9554 and symbols are printed.
9557 These settings are useful for debugging programs in any language:
9561 @item set print address
9562 @itemx set print address on
9563 @cindex print/don't print memory addresses
9564 @value{GDBN} prints memory addresses showing the location of stack
9565 traces, structure values, pointer values, breakpoints, and so forth,
9566 even when it also displays the contents of those addresses. The default
9567 is @code{on}. For example, this is what a stack frame display looks like with
9568 @code{set print address on}:
9573 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9575 530 if (lquote != def_lquote)
9579 @item set print address off
9580 Do not print addresses when displaying their contents. For example,
9581 this is the same stack frame displayed with @code{set print address off}:
9585 (@value{GDBP}) set print addr off
9587 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9588 530 if (lquote != def_lquote)
9592 You can use @samp{set print address off} to eliminate all machine
9593 dependent displays from the @value{GDBN} interface. For example, with
9594 @code{print address off}, you should get the same text for backtraces on
9595 all machines---whether or not they involve pointer arguments.
9598 @item show print address
9599 Show whether or not addresses are to be printed.
9602 When @value{GDBN} prints a symbolic address, it normally prints the
9603 closest earlier symbol plus an offset. If that symbol does not uniquely
9604 identify the address (for example, it is a name whose scope is a single
9605 source file), you may need to clarify. One way to do this is with
9606 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9607 you can set @value{GDBN} to print the source file and line number when
9608 it prints a symbolic address:
9611 @item set print symbol-filename on
9612 @cindex source file and line of a symbol
9613 @cindex symbol, source file and line
9614 Tell @value{GDBN} to print the source file name and line number of a
9615 symbol in the symbolic form of an address.
9617 @item set print symbol-filename off
9618 Do not print source file name and line number of a symbol. This is the
9621 @item show print symbol-filename
9622 Show whether or not @value{GDBN} will print the source file name and
9623 line number of a symbol in the symbolic form of an address.
9626 Another situation where it is helpful to show symbol filenames and line
9627 numbers is when disassembling code; @value{GDBN} shows you the line
9628 number and source file that corresponds to each instruction.
9630 Also, you may wish to see the symbolic form only if the address being
9631 printed is reasonably close to the closest earlier symbol:
9634 @item set print max-symbolic-offset @var{max-offset}
9635 @itemx set print max-symbolic-offset unlimited
9636 @cindex maximum value for offset of closest symbol
9637 Tell @value{GDBN} to only display the symbolic form of an address if the
9638 offset between the closest earlier symbol and the address is less than
9639 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9640 to always print the symbolic form of an address if any symbol precedes
9641 it. Zero is equivalent to @code{unlimited}.
9643 @item show print max-symbolic-offset
9644 Ask how large the maximum offset is that @value{GDBN} prints in a
9648 @cindex wild pointer, interpreting
9649 @cindex pointer, finding referent
9650 If you have a pointer and you are not sure where it points, try
9651 @samp{set print symbol-filename on}. Then you can determine the name
9652 and source file location of the variable where it points, using
9653 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9654 For example, here @value{GDBN} shows that a variable @code{ptt} points
9655 at another variable @code{t}, defined in @file{hi2.c}:
9658 (@value{GDBP}) set print symbol-filename on
9659 (@value{GDBP}) p/a ptt
9660 $4 = 0xe008 <t in hi2.c>
9664 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9665 does not show the symbol name and filename of the referent, even with
9666 the appropriate @code{set print} options turned on.
9669 You can also enable @samp{/a}-like formatting all the time using
9670 @samp{set print symbol on}:
9673 @item set print symbol on
9674 Tell @value{GDBN} to print the symbol corresponding to an address, if
9677 @item set print symbol off
9678 Tell @value{GDBN} not to print the symbol corresponding to an
9679 address. In this mode, @value{GDBN} will still print the symbol
9680 corresponding to pointers to functions. This is the default.
9682 @item show print symbol
9683 Show whether @value{GDBN} will display the symbol corresponding to an
9687 Other settings control how different kinds of objects are printed:
9690 @item set print array
9691 @itemx set print array on
9692 @cindex pretty print arrays
9693 Pretty print arrays. This format is more convenient to read,
9694 but uses more space. The default is off.
9696 @item set print array off
9697 Return to compressed format for arrays.
9699 @item show print array
9700 Show whether compressed or pretty format is selected for displaying
9703 @cindex print array indexes
9704 @item set print array-indexes
9705 @itemx set print array-indexes on
9706 Print the index of each element when displaying arrays. May be more
9707 convenient to locate a given element in the array or quickly find the
9708 index of a given element in that printed array. The default is off.
9710 @item set print array-indexes off
9711 Stop printing element indexes when displaying arrays.
9713 @item show print array-indexes
9714 Show whether the index of each element is printed when displaying
9717 @item set print elements @var{number-of-elements}
9718 @itemx set print elements unlimited
9719 @cindex number of array elements to print
9720 @cindex limit on number of printed array elements
9721 Set a limit on how many elements of an array @value{GDBN} will print.
9722 If @value{GDBN} is printing a large array, it stops printing after it has
9723 printed the number of elements set by the @code{set print elements} command.
9724 This limit also applies to the display of strings.
9725 When @value{GDBN} starts, this limit is set to 200.
9726 Setting @var{number-of-elements} to @code{unlimited} or zero means
9727 that the number of elements to print is unlimited.
9729 @item show print elements
9730 Display the number of elements of a large array that @value{GDBN} will print.
9731 If the number is 0, then the printing is unlimited.
9733 @item set print frame-arguments @var{value}
9734 @kindex set print frame-arguments
9735 @cindex printing frame argument values
9736 @cindex print all frame argument values
9737 @cindex print frame argument values for scalars only
9738 @cindex do not print frame argument values
9739 This command allows to control how the values of arguments are printed
9740 when the debugger prints a frame (@pxref{Frames}). The possible
9745 The values of all arguments are printed.
9748 Print the value of an argument only if it is a scalar. The value of more
9749 complex arguments such as arrays, structures, unions, etc, is replaced
9750 by @code{@dots{}}. This is the default. Here is an example where
9751 only scalar arguments are shown:
9754 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9759 None of the argument values are printed. Instead, the value of each argument
9760 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9763 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9768 By default, only scalar arguments are printed. This command can be used
9769 to configure the debugger to print the value of all arguments, regardless
9770 of their type. However, it is often advantageous to not print the value
9771 of more complex parameters. For instance, it reduces the amount of
9772 information printed in each frame, making the backtrace more readable.
9773 Also, it improves performance when displaying Ada frames, because
9774 the computation of large arguments can sometimes be CPU-intensive,
9775 especially in large applications. Setting @code{print frame-arguments}
9776 to @code{scalars} (the default) or @code{none} avoids this computation,
9777 thus speeding up the display of each Ada frame.
9779 @item show print frame-arguments
9780 Show how the value of arguments should be displayed when printing a frame.
9782 @item set print raw frame-arguments on
9783 Print frame arguments in raw, non pretty-printed, form.
9785 @item set print raw frame-arguments off
9786 Print frame arguments in pretty-printed form, if there is a pretty-printer
9787 for the value (@pxref{Pretty Printing}),
9788 otherwise print the value in raw form.
9789 This is the default.
9791 @item show print raw frame-arguments
9792 Show whether to print frame arguments in raw form.
9794 @anchor{set print entry-values}
9795 @item set print entry-values @var{value}
9796 @kindex set print entry-values
9797 Set printing of frame argument values at function entry. In some cases
9798 @value{GDBN} can determine the value of function argument which was passed by
9799 the function caller, even if the value was modified inside the called function
9800 and therefore is different. With optimized code, the current value could be
9801 unavailable, but the entry value may still be known.
9803 The default value is @code{default} (see below for its description). Older
9804 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9805 this feature will behave in the @code{default} setting the same way as with the
9808 This functionality is currently supported only by DWARF 2 debugging format and
9809 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9810 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9813 The @var{value} parameter can be one of the following:
9817 Print only actual parameter values, never print values from function entry
9821 #0 different (val=6)
9822 #0 lost (val=<optimized out>)
9824 #0 invalid (val=<optimized out>)
9828 Print only parameter values from function entry point. The actual parameter
9829 values are never printed.
9831 #0 equal (val@@entry=5)
9832 #0 different (val@@entry=5)
9833 #0 lost (val@@entry=5)
9834 #0 born (val@@entry=<optimized out>)
9835 #0 invalid (val@@entry=<optimized out>)
9839 Print only parameter values from function entry point. If value from function
9840 entry point is not known while the actual value is known, print the actual
9841 value for such parameter.
9843 #0 equal (val@@entry=5)
9844 #0 different (val@@entry=5)
9845 #0 lost (val@@entry=5)
9847 #0 invalid (val@@entry=<optimized out>)
9851 Print actual parameter values. If actual parameter value is not known while
9852 value from function entry point is known, print the entry point value for such
9856 #0 different (val=6)
9857 #0 lost (val@@entry=5)
9859 #0 invalid (val=<optimized out>)
9863 Always print both the actual parameter value and its value from function entry
9864 point, even if values of one or both are not available due to compiler
9867 #0 equal (val=5, val@@entry=5)
9868 #0 different (val=6, val@@entry=5)
9869 #0 lost (val=<optimized out>, val@@entry=5)
9870 #0 born (val=10, val@@entry=<optimized out>)
9871 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9875 Print the actual parameter value if it is known and also its value from
9876 function entry point if it is known. If neither is known, print for the actual
9877 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9878 values are known and identical, print the shortened
9879 @code{param=param@@entry=VALUE} notation.
9881 #0 equal (val=val@@entry=5)
9882 #0 different (val=6, val@@entry=5)
9883 #0 lost (val@@entry=5)
9885 #0 invalid (val=<optimized out>)
9889 Always print the actual parameter value. Print also its value from function
9890 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9891 if both values are known and identical, print the shortened
9892 @code{param=param@@entry=VALUE} notation.
9894 #0 equal (val=val@@entry=5)
9895 #0 different (val=6, val@@entry=5)
9896 #0 lost (val=<optimized out>, val@@entry=5)
9898 #0 invalid (val=<optimized out>)
9902 For analysis messages on possible failures of frame argument values at function
9903 entry resolution see @ref{set debug entry-values}.
9905 @item show print entry-values
9906 Show the method being used for printing of frame argument values at function
9909 @item set print repeats @var{number-of-repeats}
9910 @itemx set print repeats unlimited
9911 @cindex repeated array elements
9912 Set the threshold for suppressing display of repeated array
9913 elements. When the number of consecutive identical elements of an
9914 array exceeds the threshold, @value{GDBN} prints the string
9915 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9916 identical repetitions, instead of displaying the identical elements
9917 themselves. Setting the threshold to @code{unlimited} or zero will
9918 cause all elements to be individually printed. The default threshold
9921 @item show print repeats
9922 Display the current threshold for printing repeated identical
9925 @item set print null-stop
9926 @cindex @sc{null} elements in arrays
9927 Cause @value{GDBN} to stop printing the characters of an array when the first
9928 @sc{null} is encountered. This is useful when large arrays actually
9929 contain only short strings.
9932 @item show print null-stop
9933 Show whether @value{GDBN} stops printing an array on the first
9934 @sc{null} character.
9936 @item set print pretty on
9937 @cindex print structures in indented form
9938 @cindex indentation in structure display
9939 Cause @value{GDBN} to print structures in an indented format with one member
9940 per line, like this:
9955 @item set print pretty off
9956 Cause @value{GDBN} to print structures in a compact format, like this:
9960 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9961 meat = 0x54 "Pork"@}
9966 This is the default format.
9968 @item show print pretty
9969 Show which format @value{GDBN} is using to print structures.
9971 @item set print sevenbit-strings on
9972 @cindex eight-bit characters in strings
9973 @cindex octal escapes in strings
9974 Print using only seven-bit characters; if this option is set,
9975 @value{GDBN} displays any eight-bit characters (in strings or
9976 character values) using the notation @code{\}@var{nnn}. This setting is
9977 best if you are working in English (@sc{ascii}) and you use the
9978 high-order bit of characters as a marker or ``meta'' bit.
9980 @item set print sevenbit-strings off
9981 Print full eight-bit characters. This allows the use of more
9982 international character sets, and is the default.
9984 @item show print sevenbit-strings
9985 Show whether or not @value{GDBN} is printing only seven-bit characters.
9987 @item set print union on
9988 @cindex unions in structures, printing
9989 Tell @value{GDBN} to print unions which are contained in structures
9990 and other unions. This is the default setting.
9992 @item set print union off
9993 Tell @value{GDBN} not to print unions which are contained in
9994 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9997 @item show print union
9998 Ask @value{GDBN} whether or not it will print unions which are contained in
9999 structures and other unions.
10001 For example, given the declarations
10004 typedef enum @{Tree, Bug@} Species;
10005 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10006 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10017 struct thing foo = @{Tree, @{Acorn@}@};
10021 with @code{set print union on} in effect @samp{p foo} would print
10024 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10028 and with @code{set print union off} in effect it would print
10031 $1 = @{it = Tree, form = @{...@}@}
10035 @code{set print union} affects programs written in C-like languages
10041 These settings are of interest when debugging C@t{++} programs:
10044 @cindex demangling C@t{++} names
10045 @item set print demangle
10046 @itemx set print demangle on
10047 Print C@t{++} names in their source form rather than in the encoded
10048 (``mangled'') form passed to the assembler and linker for type-safe
10049 linkage. The default is on.
10051 @item show print demangle
10052 Show whether C@t{++} names are printed in mangled or demangled form.
10054 @item set print asm-demangle
10055 @itemx set print asm-demangle on
10056 Print C@t{++} names in their source form rather than their mangled form, even
10057 in assembler code printouts such as instruction disassemblies.
10058 The default is off.
10060 @item show print asm-demangle
10061 Show whether C@t{++} names in assembly listings are printed in mangled
10064 @cindex C@t{++} symbol decoding style
10065 @cindex symbol decoding style, C@t{++}
10066 @kindex set demangle-style
10067 @item set demangle-style @var{style}
10068 Choose among several encoding schemes used by different compilers to
10069 represent C@t{++} names. The choices for @var{style} are currently:
10073 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10074 This is the default.
10077 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10080 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10083 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10086 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10087 @strong{Warning:} this setting alone is not sufficient to allow
10088 debugging @code{cfront}-generated executables. @value{GDBN} would
10089 require further enhancement to permit that.
10092 If you omit @var{style}, you will see a list of possible formats.
10094 @item show demangle-style
10095 Display the encoding style currently in use for decoding C@t{++} symbols.
10097 @item set print object
10098 @itemx set print object on
10099 @cindex derived type of an object, printing
10100 @cindex display derived types
10101 When displaying a pointer to an object, identify the @emph{actual}
10102 (derived) type of the object rather than the @emph{declared} type, using
10103 the virtual function table. Note that the virtual function table is
10104 required---this feature can only work for objects that have run-time
10105 type identification; a single virtual method in the object's declared
10106 type is sufficient. Note that this setting is also taken into account when
10107 working with variable objects via MI (@pxref{GDB/MI}).
10109 @item set print object off
10110 Display only the declared type of objects, without reference to the
10111 virtual function table. This is the default setting.
10113 @item show print object
10114 Show whether actual, or declared, object types are displayed.
10116 @item set print static-members
10117 @itemx set print static-members on
10118 @cindex static members of C@t{++} objects
10119 Print static members when displaying a C@t{++} object. The default is on.
10121 @item set print static-members off
10122 Do not print static members when displaying a C@t{++} object.
10124 @item show print static-members
10125 Show whether C@t{++} static members are printed or not.
10127 @item set print pascal_static-members
10128 @itemx set print pascal_static-members on
10129 @cindex static members of Pascal objects
10130 @cindex Pascal objects, static members display
10131 Print static members when displaying a Pascal object. The default is on.
10133 @item set print pascal_static-members off
10134 Do not print static members when displaying a Pascal object.
10136 @item show print pascal_static-members
10137 Show whether Pascal static members are printed or not.
10139 @c These don't work with HP ANSI C++ yet.
10140 @item set print vtbl
10141 @itemx set print vtbl on
10142 @cindex pretty print C@t{++} virtual function tables
10143 @cindex virtual functions (C@t{++}) display
10144 @cindex VTBL display
10145 Pretty print C@t{++} virtual function tables. The default is off.
10146 (The @code{vtbl} commands do not work on programs compiled with the HP
10147 ANSI C@t{++} compiler (@code{aCC}).)
10149 @item set print vtbl off
10150 Do not pretty print C@t{++} virtual function tables.
10152 @item show print vtbl
10153 Show whether C@t{++} virtual function tables are pretty printed, or not.
10156 @node Pretty Printing
10157 @section Pretty Printing
10159 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10160 Python code. It greatly simplifies the display of complex objects. This
10161 mechanism works for both MI and the CLI.
10164 * Pretty-Printer Introduction:: Introduction to pretty-printers
10165 * Pretty-Printer Example:: An example pretty-printer
10166 * Pretty-Printer Commands:: Pretty-printer commands
10169 @node Pretty-Printer Introduction
10170 @subsection Pretty-Printer Introduction
10172 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10173 registered for the value. If there is then @value{GDBN} invokes the
10174 pretty-printer to print the value. Otherwise the value is printed normally.
10176 Pretty-printers are normally named. This makes them easy to manage.
10177 The @samp{info pretty-printer} command will list all the installed
10178 pretty-printers with their names.
10179 If a pretty-printer can handle multiple data types, then its
10180 @dfn{subprinters} are the printers for the individual data types.
10181 Each such subprinter has its own name.
10182 The format of the name is @var{printer-name};@var{subprinter-name}.
10184 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10185 Typically they are automatically loaded and registered when the corresponding
10186 debug information is loaded, thus making them available without having to
10187 do anything special.
10189 There are three places where a pretty-printer can be registered.
10193 Pretty-printers registered globally are available when debugging
10197 Pretty-printers registered with a program space are available only
10198 when debugging that program.
10199 @xref{Progspaces In Python}, for more details on program spaces in Python.
10202 Pretty-printers registered with an objfile are loaded and unloaded
10203 with the corresponding objfile (e.g., shared library).
10204 @xref{Objfiles In Python}, for more details on objfiles in Python.
10207 @xref{Selecting Pretty-Printers}, for further information on how
10208 pretty-printers are selected,
10210 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10213 @node Pretty-Printer Example
10214 @subsection Pretty-Printer Example
10216 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10219 (@value{GDBP}) print s
10221 static npos = 4294967295,
10223 <std::allocator<char>> = @{
10224 <__gnu_cxx::new_allocator<char>> = @{
10225 <No data fields>@}, <No data fields>
10227 members of std::basic_string<char, std::char_traits<char>,
10228 std::allocator<char> >::_Alloc_hider:
10229 _M_p = 0x804a014 "abcd"
10234 With a pretty-printer for @code{std::string} only the contents are printed:
10237 (@value{GDBP}) print s
10241 @node Pretty-Printer Commands
10242 @subsection Pretty-Printer Commands
10243 @cindex pretty-printer commands
10246 @kindex info pretty-printer
10247 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10248 Print the list of installed pretty-printers.
10249 This includes disabled pretty-printers, which are marked as such.
10251 @var{object-regexp} is a regular expression matching the objects
10252 whose pretty-printers to list.
10253 Objects can be @code{global}, the program space's file
10254 (@pxref{Progspaces In Python}),
10255 and the object files within that program space (@pxref{Objfiles In Python}).
10256 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10257 looks up a printer from these three objects.
10259 @var{name-regexp} is a regular expression matching the name of the printers
10262 @kindex disable pretty-printer
10263 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10264 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10265 A disabled pretty-printer is not forgotten, it may be enabled again later.
10267 @kindex enable pretty-printer
10268 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10269 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10274 Suppose we have three pretty-printers installed: one from library1.so
10275 named @code{foo} that prints objects of type @code{foo}, and
10276 another from library2.so named @code{bar} that prints two types of objects,
10277 @code{bar1} and @code{bar2}.
10280 (gdb) info pretty-printer
10287 (gdb) info pretty-printer library2
10292 (gdb) disable pretty-printer library1
10294 2 of 3 printers enabled
10295 (gdb) info pretty-printer
10302 (gdb) disable pretty-printer library2 bar:bar1
10304 1 of 3 printers enabled
10305 (gdb) info pretty-printer library2
10312 (gdb) disable pretty-printer library2 bar
10314 0 of 3 printers enabled
10315 (gdb) info pretty-printer library2
10324 Note that for @code{bar} the entire printer can be disabled,
10325 as can each individual subprinter.
10327 @node Value History
10328 @section Value History
10330 @cindex value history
10331 @cindex history of values printed by @value{GDBN}
10332 Values printed by the @code{print} command are saved in the @value{GDBN}
10333 @dfn{value history}. This allows you to refer to them in other expressions.
10334 Values are kept until the symbol table is re-read or discarded
10335 (for example with the @code{file} or @code{symbol-file} commands).
10336 When the symbol table changes, the value history is discarded,
10337 since the values may contain pointers back to the types defined in the
10342 @cindex history number
10343 The values printed are given @dfn{history numbers} by which you can
10344 refer to them. These are successive integers starting with one.
10345 @code{print} shows you the history number assigned to a value by
10346 printing @samp{$@var{num} = } before the value; here @var{num} is the
10349 To refer to any previous value, use @samp{$} followed by the value's
10350 history number. The way @code{print} labels its output is designed to
10351 remind you of this. Just @code{$} refers to the most recent value in
10352 the history, and @code{$$} refers to the value before that.
10353 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10354 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10355 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10357 For example, suppose you have just printed a pointer to a structure and
10358 want to see the contents of the structure. It suffices to type
10364 If you have a chain of structures where the component @code{next} points
10365 to the next one, you can print the contents of the next one with this:
10372 You can print successive links in the chain by repeating this
10373 command---which you can do by just typing @key{RET}.
10375 Note that the history records values, not expressions. If the value of
10376 @code{x} is 4 and you type these commands:
10384 then the value recorded in the value history by the @code{print} command
10385 remains 4 even though the value of @code{x} has changed.
10388 @kindex show values
10390 Print the last ten values in the value history, with their item numbers.
10391 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10392 values} does not change the history.
10394 @item show values @var{n}
10395 Print ten history values centered on history item number @var{n}.
10397 @item show values +
10398 Print ten history values just after the values last printed. If no more
10399 values are available, @code{show values +} produces no display.
10402 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10403 same effect as @samp{show values +}.
10405 @node Convenience Vars
10406 @section Convenience Variables
10408 @cindex convenience variables
10409 @cindex user-defined variables
10410 @value{GDBN} provides @dfn{convenience variables} that you can use within
10411 @value{GDBN} to hold on to a value and refer to it later. These variables
10412 exist entirely within @value{GDBN}; they are not part of your program, and
10413 setting a convenience variable has no direct effect on further execution
10414 of your program. That is why you can use them freely.
10416 Convenience variables are prefixed with @samp{$}. Any name preceded by
10417 @samp{$} can be used for a convenience variable, unless it is one of
10418 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10419 (Value history references, in contrast, are @emph{numbers} preceded
10420 by @samp{$}. @xref{Value History, ,Value History}.)
10422 You can save a value in a convenience variable with an assignment
10423 expression, just as you would set a variable in your program.
10427 set $foo = *object_ptr
10431 would save in @code{$foo} the value contained in the object pointed to by
10434 Using a convenience variable for the first time creates it, but its
10435 value is @code{void} until you assign a new value. You can alter the
10436 value with another assignment at any time.
10438 Convenience variables have no fixed types. You can assign a convenience
10439 variable any type of value, including structures and arrays, even if
10440 that variable already has a value of a different type. The convenience
10441 variable, when used as an expression, has the type of its current value.
10444 @kindex show convenience
10445 @cindex show all user variables and functions
10446 @item show convenience
10447 Print a list of convenience variables used so far, and their values,
10448 as well as a list of the convenience functions.
10449 Abbreviated @code{show conv}.
10451 @kindex init-if-undefined
10452 @cindex convenience variables, initializing
10453 @item init-if-undefined $@var{variable} = @var{expression}
10454 Set a convenience variable if it has not already been set. This is useful
10455 for user-defined commands that keep some state. It is similar, in concept,
10456 to using local static variables with initializers in C (except that
10457 convenience variables are global). It can also be used to allow users to
10458 override default values used in a command script.
10460 If the variable is already defined then the expression is not evaluated so
10461 any side-effects do not occur.
10464 One of the ways to use a convenience variable is as a counter to be
10465 incremented or a pointer to be advanced. For example, to print
10466 a field from successive elements of an array of structures:
10470 print bar[$i++]->contents
10474 Repeat that command by typing @key{RET}.
10476 Some convenience variables are created automatically by @value{GDBN} and given
10477 values likely to be useful.
10480 @vindex $_@r{, convenience variable}
10482 The variable @code{$_} is automatically set by the @code{x} command to
10483 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10484 commands which provide a default address for @code{x} to examine also
10485 set @code{$_} to that address; these commands include @code{info line}
10486 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10487 except when set by the @code{x} command, in which case it is a pointer
10488 to the type of @code{$__}.
10490 @vindex $__@r{, convenience variable}
10492 The variable @code{$__} is automatically set by the @code{x} command
10493 to the value found in the last address examined. Its type is chosen
10494 to match the format in which the data was printed.
10497 @vindex $_exitcode@r{, convenience variable}
10498 When the program being debugged terminates normally, @value{GDBN}
10499 automatically sets this variable to the exit code of the program, and
10500 resets @code{$_exitsignal} to @code{void}.
10503 @vindex $_exitsignal@r{, convenience variable}
10504 When the program being debugged dies due to an uncaught signal,
10505 @value{GDBN} automatically sets this variable to that signal's number,
10506 and resets @code{$_exitcode} to @code{void}.
10508 To distinguish between whether the program being debugged has exited
10509 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10510 @code{$_exitsignal} is not @code{void}), the convenience function
10511 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10512 Functions}). For example, considering the following source code:
10515 #include <signal.h>
10518 main (int argc, char *argv[])
10525 A valid way of telling whether the program being debugged has exited
10526 or signalled would be:
10529 (@value{GDBP}) define has_exited_or_signalled
10530 Type commands for definition of ``has_exited_or_signalled''.
10531 End with a line saying just ``end''.
10532 >if $_isvoid ($_exitsignal)
10533 >echo The program has exited\n
10535 >echo The program has signalled\n
10541 Program terminated with signal SIGALRM, Alarm clock.
10542 The program no longer exists.
10543 (@value{GDBP}) has_exited_or_signalled
10544 The program has signalled
10547 As can be seen, @value{GDBN} correctly informs that the program being
10548 debugged has signalled, since it calls @code{raise} and raises a
10549 @code{SIGALRM} signal. If the program being debugged had not called
10550 @code{raise}, then @value{GDBN} would report a normal exit:
10553 (@value{GDBP}) has_exited_or_signalled
10554 The program has exited
10558 The variable @code{$_exception} is set to the exception object being
10559 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10562 @itemx $_probe_arg0@dots{}$_probe_arg11
10563 Arguments to a static probe. @xref{Static Probe Points}.
10566 @vindex $_sdata@r{, inspect, convenience variable}
10567 The variable @code{$_sdata} contains extra collected static tracepoint
10568 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10569 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10570 if extra static tracepoint data has not been collected.
10573 @vindex $_siginfo@r{, convenience variable}
10574 The variable @code{$_siginfo} contains extra signal information
10575 (@pxref{extra signal information}). Note that @code{$_siginfo}
10576 could be empty, if the application has not yet received any signals.
10577 For example, it will be empty before you execute the @code{run} command.
10580 @vindex $_tlb@r{, convenience variable}
10581 The variable @code{$_tlb} is automatically set when debugging
10582 applications running on MS-Windows in native mode or connected to
10583 gdbserver that supports the @code{qGetTIBAddr} request.
10584 @xref{General Query Packets}.
10585 This variable contains the address of the thread information block.
10588 The number of the current inferior. @xref{Inferiors and
10589 Programs, ,Debugging Multiple Inferiors and Programs}.
10592 The thread number of the current thread. @xref{thread numbers}.
10595 The global number of the current thread. @xref{global thread numbers}.
10599 @node Convenience Funs
10600 @section Convenience Functions
10602 @cindex convenience functions
10603 @value{GDBN} also supplies some @dfn{convenience functions}. These
10604 have a syntax similar to convenience variables. A convenience
10605 function can be used in an expression just like an ordinary function;
10606 however, a convenience function is implemented internally to
10609 These functions do not require @value{GDBN} to be configured with
10610 @code{Python} support, which means that they are always available.
10614 @item $_isvoid (@var{expr})
10615 @findex $_isvoid@r{, convenience function}
10616 Return one if the expression @var{expr} is @code{void}. Otherwise it
10619 A @code{void} expression is an expression where the type of the result
10620 is @code{void}. For example, you can examine a convenience variable
10621 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10625 (@value{GDBP}) print $_exitcode
10627 (@value{GDBP}) print $_isvoid ($_exitcode)
10630 Starting program: ./a.out
10631 [Inferior 1 (process 29572) exited normally]
10632 (@value{GDBP}) print $_exitcode
10634 (@value{GDBP}) print $_isvoid ($_exitcode)
10638 In the example above, we used @code{$_isvoid} to check whether
10639 @code{$_exitcode} is @code{void} before and after the execution of the
10640 program being debugged. Before the execution there is no exit code to
10641 be examined, therefore @code{$_exitcode} is @code{void}. After the
10642 execution the program being debugged returned zero, therefore
10643 @code{$_exitcode} is zero, which means that it is not @code{void}
10646 The @code{void} expression can also be a call of a function from the
10647 program being debugged. For example, given the following function:
10656 The result of calling it inside @value{GDBN} is @code{void}:
10659 (@value{GDBP}) print foo ()
10661 (@value{GDBP}) print $_isvoid (foo ())
10663 (@value{GDBP}) set $v = foo ()
10664 (@value{GDBP}) print $v
10666 (@value{GDBP}) print $_isvoid ($v)
10672 These functions require @value{GDBN} to be configured with
10673 @code{Python} support.
10677 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10678 @findex $_memeq@r{, convenience function}
10679 Returns one if the @var{length} bytes at the addresses given by
10680 @var{buf1} and @var{buf2} are equal.
10681 Otherwise it returns zero.
10683 @item $_regex(@var{str}, @var{regex})
10684 @findex $_regex@r{, convenience function}
10685 Returns one if the string @var{str} matches the regular expression
10686 @var{regex}. Otherwise it returns zero.
10687 The syntax of the regular expression is that specified by @code{Python}'s
10688 regular expression support.
10690 @item $_streq(@var{str1}, @var{str2})
10691 @findex $_streq@r{, convenience function}
10692 Returns one if the strings @var{str1} and @var{str2} are equal.
10693 Otherwise it returns zero.
10695 @item $_strlen(@var{str})
10696 @findex $_strlen@r{, convenience function}
10697 Returns the length of string @var{str}.
10699 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10700 @findex $_caller_is@r{, convenience function}
10701 Returns one if the calling function's name is equal to @var{name}.
10702 Otherwise it returns zero.
10704 If the optional argument @var{number_of_frames} is provided,
10705 it is the number of frames up in the stack to look.
10713 at testsuite/gdb.python/py-caller-is.c:21
10714 #1 0x00000000004005a0 in middle_func ()
10715 at testsuite/gdb.python/py-caller-is.c:27
10716 #2 0x00000000004005ab in top_func ()
10717 at testsuite/gdb.python/py-caller-is.c:33
10718 #3 0x00000000004005b6 in main ()
10719 at testsuite/gdb.python/py-caller-is.c:39
10720 (gdb) print $_caller_is ("middle_func")
10722 (gdb) print $_caller_is ("top_func", 2)
10726 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10727 @findex $_caller_matches@r{, convenience function}
10728 Returns one if the calling function's name matches the regular expression
10729 @var{regexp}. Otherwise it returns zero.
10731 If the optional argument @var{number_of_frames} is provided,
10732 it is the number of frames up in the stack to look.
10735 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10736 @findex $_any_caller_is@r{, convenience function}
10737 Returns one if any calling function's name is equal to @var{name}.
10738 Otherwise it returns zero.
10740 If the optional argument @var{number_of_frames} is provided,
10741 it is the number of frames up in the stack to look.
10744 This function differs from @code{$_caller_is} in that this function
10745 checks all stack frames from the immediate caller to the frame specified
10746 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10747 frame specified by @var{number_of_frames}.
10749 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10750 @findex $_any_caller_matches@r{, convenience function}
10751 Returns one if any calling function's name matches the regular expression
10752 @var{regexp}. Otherwise it returns zero.
10754 If the optional argument @var{number_of_frames} is provided,
10755 it is the number of frames up in the stack to look.
10758 This function differs from @code{$_caller_matches} in that this function
10759 checks all stack frames from the immediate caller to the frame specified
10760 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10761 frame specified by @var{number_of_frames}.
10763 @item $_as_string(@var{value})
10764 @findex $_as_string@r{, convenience function}
10765 Return the string representation of @var{value}.
10767 This function is useful to obtain the textual label (enumerator) of an
10768 enumeration value. For example, assuming the variable @var{node} is of
10769 an enumerated type:
10772 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10773 Visiting node of type NODE_INTEGER
10778 @value{GDBN} provides the ability to list and get help on
10779 convenience functions.
10782 @item help function
10783 @kindex help function
10784 @cindex show all convenience functions
10785 Print a list of all convenience functions.
10792 You can refer to machine register contents, in expressions, as variables
10793 with names starting with @samp{$}. The names of registers are different
10794 for each machine; use @code{info registers} to see the names used on
10798 @kindex info registers
10799 @item info registers
10800 Print the names and values of all registers except floating-point
10801 and vector registers (in the selected stack frame).
10803 @kindex info all-registers
10804 @cindex floating point registers
10805 @item info all-registers
10806 Print the names and values of all registers, including floating-point
10807 and vector registers (in the selected stack frame).
10809 @item info registers @var{regname} @dots{}
10810 Print the @dfn{relativized} value of each specified register @var{regname}.
10811 As discussed in detail below, register values are normally relative to
10812 the selected stack frame. The @var{regname} may be any register name valid on
10813 the machine you are using, with or without the initial @samp{$}.
10816 @anchor{standard registers}
10817 @cindex stack pointer register
10818 @cindex program counter register
10819 @cindex process status register
10820 @cindex frame pointer register
10821 @cindex standard registers
10822 @value{GDBN} has four ``standard'' register names that are available (in
10823 expressions) on most machines---whenever they do not conflict with an
10824 architecture's canonical mnemonics for registers. The register names
10825 @code{$pc} and @code{$sp} are used for the program counter register and
10826 the stack pointer. @code{$fp} is used for a register that contains a
10827 pointer to the current stack frame, and @code{$ps} is used for a
10828 register that contains the processor status. For example,
10829 you could print the program counter in hex with
10836 or print the instruction to be executed next with
10843 or add four to the stack pointer@footnote{This is a way of removing
10844 one word from the stack, on machines where stacks grow downward in
10845 memory (most machines, nowadays). This assumes that the innermost
10846 stack frame is selected; setting @code{$sp} is not allowed when other
10847 stack frames are selected. To pop entire frames off the stack,
10848 regardless of machine architecture, use @code{return};
10849 see @ref{Returning, ,Returning from a Function}.} with
10855 Whenever possible, these four standard register names are available on
10856 your machine even though the machine has different canonical mnemonics,
10857 so long as there is no conflict. The @code{info registers} command
10858 shows the canonical names. For example, on the SPARC, @code{info
10859 registers} displays the processor status register as @code{$psr} but you
10860 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10861 is an alias for the @sc{eflags} register.
10863 @value{GDBN} always considers the contents of an ordinary register as an
10864 integer when the register is examined in this way. Some machines have
10865 special registers which can hold nothing but floating point; these
10866 registers are considered to have floating point values. There is no way
10867 to refer to the contents of an ordinary register as floating point value
10868 (although you can @emph{print} it as a floating point value with
10869 @samp{print/f $@var{regname}}).
10871 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10872 means that the data format in which the register contents are saved by
10873 the operating system is not the same one that your program normally
10874 sees. For example, the registers of the 68881 floating point
10875 coprocessor are always saved in ``extended'' (raw) format, but all C
10876 programs expect to work with ``double'' (virtual) format. In such
10877 cases, @value{GDBN} normally works with the virtual format only (the format
10878 that makes sense for your program), but the @code{info registers} command
10879 prints the data in both formats.
10881 @cindex SSE registers (x86)
10882 @cindex MMX registers (x86)
10883 Some machines have special registers whose contents can be interpreted
10884 in several different ways. For example, modern x86-based machines
10885 have SSE and MMX registers that can hold several values packed
10886 together in several different formats. @value{GDBN} refers to such
10887 registers in @code{struct} notation:
10890 (@value{GDBP}) print $xmm1
10892 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10893 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10894 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10895 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10896 v4_int32 = @{0, 20657912, 11, 13@},
10897 v2_int64 = @{88725056443645952, 55834574859@},
10898 uint128 = 0x0000000d0000000b013b36f800000000
10903 To set values of such registers, you need to tell @value{GDBN} which
10904 view of the register you wish to change, as if you were assigning
10905 value to a @code{struct} member:
10908 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10911 Normally, register values are relative to the selected stack frame
10912 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10913 value that the register would contain if all stack frames farther in
10914 were exited and their saved registers restored. In order to see the
10915 true contents of hardware registers, you must select the innermost
10916 frame (with @samp{frame 0}).
10918 @cindex caller-saved registers
10919 @cindex call-clobbered registers
10920 @cindex volatile registers
10921 @cindex <not saved> values
10922 Usually ABIs reserve some registers as not needed to be saved by the
10923 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10924 registers). It may therefore not be possible for @value{GDBN} to know
10925 the value a register had before the call (in other words, in the outer
10926 frame), if the register value has since been changed by the callee.
10927 @value{GDBN} tries to deduce where the inner frame saved
10928 (``callee-saved'') registers, from the debug info, unwind info, or the
10929 machine code generated by your compiler. If some register is not
10930 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10931 its own knowledge of the ABI, or because the debug/unwind info
10932 explicitly says the register's value is undefined), @value{GDBN}
10933 displays @w{@samp{<not saved>}} as the register's value. With targets
10934 that @value{GDBN} has no knowledge of the register saving convention,
10935 if a register was not saved by the callee, then its value and location
10936 in the outer frame are assumed to be the same of the inner frame.
10937 This is usually harmless, because if the register is call-clobbered,
10938 the caller either does not care what is in the register after the
10939 call, or has code to restore the value that it does care about. Note,
10940 however, that if you change such a register in the outer frame, you
10941 may also be affecting the inner frame. Also, the more ``outer'' the
10942 frame is you're looking at, the more likely a call-clobbered
10943 register's value is to be wrong, in the sense that it doesn't actually
10944 represent the value the register had just before the call.
10946 @node Floating Point Hardware
10947 @section Floating Point Hardware
10948 @cindex floating point
10950 Depending on the configuration, @value{GDBN} may be able to give
10951 you more information about the status of the floating point hardware.
10956 Display hardware-dependent information about the floating
10957 point unit. The exact contents and layout vary depending on the
10958 floating point chip. Currently, @samp{info float} is supported on
10959 the ARM and x86 machines.
10963 @section Vector Unit
10964 @cindex vector unit
10966 Depending on the configuration, @value{GDBN} may be able to give you
10967 more information about the status of the vector unit.
10970 @kindex info vector
10972 Display information about the vector unit. The exact contents and
10973 layout vary depending on the hardware.
10976 @node OS Information
10977 @section Operating System Auxiliary Information
10978 @cindex OS information
10980 @value{GDBN} provides interfaces to useful OS facilities that can help
10981 you debug your program.
10983 @cindex auxiliary vector
10984 @cindex vector, auxiliary
10985 Some operating systems supply an @dfn{auxiliary vector} to programs at
10986 startup. This is akin to the arguments and environment that you
10987 specify for a program, but contains a system-dependent variety of
10988 binary values that tell system libraries important details about the
10989 hardware, operating system, and process. Each value's purpose is
10990 identified by an integer tag; the meanings are well-known but system-specific.
10991 Depending on the configuration and operating system facilities,
10992 @value{GDBN} may be able to show you this information. For remote
10993 targets, this functionality may further depend on the remote stub's
10994 support of the @samp{qXfer:auxv:read} packet, see
10995 @ref{qXfer auxiliary vector read}.
11000 Display the auxiliary vector of the inferior, which can be either a
11001 live process or a core dump file. @value{GDBN} prints each tag value
11002 numerically, and also shows names and text descriptions for recognized
11003 tags. Some values in the vector are numbers, some bit masks, and some
11004 pointers to strings or other data. @value{GDBN} displays each value in the
11005 most appropriate form for a recognized tag, and in hexadecimal for
11006 an unrecognized tag.
11009 On some targets, @value{GDBN} can access operating system-specific
11010 information and show it to you. The types of information available
11011 will differ depending on the type of operating system running on the
11012 target. The mechanism used to fetch the data is described in
11013 @ref{Operating System Information}. For remote targets, this
11014 functionality depends on the remote stub's support of the
11015 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11019 @item info os @var{infotype}
11021 Display OS information of the requested type.
11023 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11025 @anchor{linux info os infotypes}
11027 @kindex info os cpus
11029 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11030 the available fields from /proc/cpuinfo. For each supported architecture
11031 different fields are available. Two common entries are processor which gives
11032 CPU number and bogomips; a system constant that is calculated during
11033 kernel initialization.
11035 @kindex info os files
11037 Display the list of open file descriptors on the target. For each
11038 file descriptor, @value{GDBN} prints the identifier of the process
11039 owning the descriptor, the command of the owning process, the value
11040 of the descriptor, and the target of the descriptor.
11042 @kindex info os modules
11044 Display the list of all loaded kernel modules on the target. For each
11045 module, @value{GDBN} prints the module name, the size of the module in
11046 bytes, the number of times the module is used, the dependencies of the
11047 module, the status of the module, and the address of the loaded module
11050 @kindex info os msg
11052 Display the list of all System V message queues on the target. For each
11053 message queue, @value{GDBN} prints the message queue key, the message
11054 queue identifier, the access permissions, the current number of bytes
11055 on the queue, the current number of messages on the queue, the processes
11056 that last sent and received a message on the queue, the user and group
11057 of the owner and creator of the message queue, the times at which a
11058 message was last sent and received on the queue, and the time at which
11059 the message queue was last changed.
11061 @kindex info os processes
11063 Display the list of processes on the target. For each process,
11064 @value{GDBN} prints the process identifier, the name of the user, the
11065 command corresponding to the process, and the list of processor cores
11066 that the process is currently running on. (To understand what these
11067 properties mean, for this and the following info types, please consult
11068 the general @sc{gnu}/Linux documentation.)
11070 @kindex info os procgroups
11072 Display the list of process groups on the target. For each process,
11073 @value{GDBN} prints the identifier of the process group that it belongs
11074 to, the command corresponding to the process group leader, the process
11075 identifier, and the command line of the process. The list is sorted
11076 first by the process group identifier, then by the process identifier,
11077 so that processes belonging to the same process group are grouped together
11078 and the process group leader is listed first.
11080 @kindex info os semaphores
11082 Display the list of all System V semaphore sets on the target. For each
11083 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11084 set identifier, the access permissions, the number of semaphores in the
11085 set, the user and group of the owner and creator of the semaphore set,
11086 and the times at which the semaphore set was operated upon and changed.
11088 @kindex info os shm
11090 Display the list of all System V shared-memory regions on the target.
11091 For each shared-memory region, @value{GDBN} prints the region key,
11092 the shared-memory identifier, the access permissions, the size of the
11093 region, the process that created the region, the process that last
11094 attached to or detached from the region, the current number of live
11095 attaches to the region, and the times at which the region was last
11096 attached to, detach from, and changed.
11098 @kindex info os sockets
11100 Display the list of Internet-domain sockets on the target. For each
11101 socket, @value{GDBN} prints the address and port of the local and
11102 remote endpoints, the current state of the connection, the creator of
11103 the socket, the IP address family of the socket, and the type of the
11106 @kindex info os threads
11108 Display the list of threads running on the target. For each thread,
11109 @value{GDBN} prints the identifier of the process that the thread
11110 belongs to, the command of the process, the thread identifier, and the
11111 processor core that it is currently running on. The main thread of a
11112 process is not listed.
11116 If @var{infotype} is omitted, then list the possible values for
11117 @var{infotype} and the kind of OS information available for each
11118 @var{infotype}. If the target does not return a list of possible
11119 types, this command will report an error.
11122 @node Memory Region Attributes
11123 @section Memory Region Attributes
11124 @cindex memory region attributes
11126 @dfn{Memory region attributes} allow you to describe special handling
11127 required by regions of your target's memory. @value{GDBN} uses
11128 attributes to determine whether to allow certain types of memory
11129 accesses; whether to use specific width accesses; and whether to cache
11130 target memory. By default the description of memory regions is
11131 fetched from the target (if the current target supports this), but the
11132 user can override the fetched regions.
11134 Defined memory regions can be individually enabled and disabled. When a
11135 memory region is disabled, @value{GDBN} uses the default attributes when
11136 accessing memory in that region. Similarly, if no memory regions have
11137 been defined, @value{GDBN} uses the default attributes when accessing
11140 When a memory region is defined, it is given a number to identify it;
11141 to enable, disable, or remove a memory region, you specify that number.
11145 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11146 Define a memory region bounded by @var{lower} and @var{upper} with
11147 attributes @var{attributes}@dots{}, and add it to the list of regions
11148 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11149 case: it is treated as the target's maximum memory address.
11150 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11153 Discard any user changes to the memory regions and use target-supplied
11154 regions, if available, or no regions if the target does not support.
11157 @item delete mem @var{nums}@dots{}
11158 Remove memory regions @var{nums}@dots{} from the list of regions
11159 monitored by @value{GDBN}.
11161 @kindex disable mem
11162 @item disable mem @var{nums}@dots{}
11163 Disable monitoring of memory regions @var{nums}@dots{}.
11164 A disabled memory region is not forgotten.
11165 It may be enabled again later.
11168 @item enable mem @var{nums}@dots{}
11169 Enable monitoring of memory regions @var{nums}@dots{}.
11173 Print a table of all defined memory regions, with the following columns
11177 @item Memory Region Number
11178 @item Enabled or Disabled.
11179 Enabled memory regions are marked with @samp{y}.
11180 Disabled memory regions are marked with @samp{n}.
11183 The address defining the inclusive lower bound of the memory region.
11186 The address defining the exclusive upper bound of the memory region.
11189 The list of attributes set for this memory region.
11194 @subsection Attributes
11196 @subsubsection Memory Access Mode
11197 The access mode attributes set whether @value{GDBN} may make read or
11198 write accesses to a memory region.
11200 While these attributes prevent @value{GDBN} from performing invalid
11201 memory accesses, they do nothing to prevent the target system, I/O DMA,
11202 etc.@: from accessing memory.
11206 Memory is read only.
11208 Memory is write only.
11210 Memory is read/write. This is the default.
11213 @subsubsection Memory Access Size
11214 The access size attribute tells @value{GDBN} to use specific sized
11215 accesses in the memory region. Often memory mapped device registers
11216 require specific sized accesses. If no access size attribute is
11217 specified, @value{GDBN} may use accesses of any size.
11221 Use 8 bit memory accesses.
11223 Use 16 bit memory accesses.
11225 Use 32 bit memory accesses.
11227 Use 64 bit memory accesses.
11230 @c @subsubsection Hardware/Software Breakpoints
11231 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11232 @c will use hardware or software breakpoints for the internal breakpoints
11233 @c used by the step, next, finish, until, etc. commands.
11237 @c Always use hardware breakpoints
11238 @c @item swbreak (default)
11241 @subsubsection Data Cache
11242 The data cache attributes set whether @value{GDBN} will cache target
11243 memory. While this generally improves performance by reducing debug
11244 protocol overhead, it can lead to incorrect results because @value{GDBN}
11245 does not know about volatile variables or memory mapped device
11250 Enable @value{GDBN} to cache target memory.
11252 Disable @value{GDBN} from caching target memory. This is the default.
11255 @subsection Memory Access Checking
11256 @value{GDBN} can be instructed to refuse accesses to memory that is
11257 not explicitly described. This can be useful if accessing such
11258 regions has undesired effects for a specific target, or to provide
11259 better error checking. The following commands control this behaviour.
11262 @kindex set mem inaccessible-by-default
11263 @item set mem inaccessible-by-default [on|off]
11264 If @code{on} is specified, make @value{GDBN} treat memory not
11265 explicitly described by the memory ranges as non-existent and refuse accesses
11266 to such memory. The checks are only performed if there's at least one
11267 memory range defined. If @code{off} is specified, make @value{GDBN}
11268 treat the memory not explicitly described by the memory ranges as RAM.
11269 The default value is @code{on}.
11270 @kindex show mem inaccessible-by-default
11271 @item show mem inaccessible-by-default
11272 Show the current handling of accesses to unknown memory.
11276 @c @subsubsection Memory Write Verification
11277 @c The memory write verification attributes set whether @value{GDBN}
11278 @c will re-reads data after each write to verify the write was successful.
11282 @c @item noverify (default)
11285 @node Dump/Restore Files
11286 @section Copy Between Memory and a File
11287 @cindex dump/restore files
11288 @cindex append data to a file
11289 @cindex dump data to a file
11290 @cindex restore data from a file
11292 You can use the commands @code{dump}, @code{append}, and
11293 @code{restore} to copy data between target memory and a file. The
11294 @code{dump} and @code{append} commands write data to a file, and the
11295 @code{restore} command reads data from a file back into the inferior's
11296 memory. Files may be in binary, Motorola S-record, Intel hex,
11297 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11298 append to binary files, and cannot read from Verilog Hex files.
11303 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11304 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11305 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11306 or the value of @var{expr}, to @var{filename} in the given format.
11308 The @var{format} parameter may be any one of:
11315 Motorola S-record format.
11317 Tektronix Hex format.
11319 Verilog Hex format.
11322 @value{GDBN} uses the same definitions of these formats as the
11323 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11324 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11328 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11329 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11330 Append the contents of memory from @var{start_addr} to @var{end_addr},
11331 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11332 (@value{GDBN} can only append data to files in raw binary form.)
11335 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11336 Restore the contents of file @var{filename} into memory. The
11337 @code{restore} command can automatically recognize any known @sc{bfd}
11338 file format, except for raw binary. To restore a raw binary file you
11339 must specify the optional keyword @code{binary} after the filename.
11341 If @var{bias} is non-zero, its value will be added to the addresses
11342 contained in the file. Binary files always start at address zero, so
11343 they will be restored at address @var{bias}. Other bfd files have
11344 a built-in location; they will be restored at offset @var{bias}
11345 from that location.
11347 If @var{start} and/or @var{end} are non-zero, then only data between
11348 file offset @var{start} and file offset @var{end} will be restored.
11349 These offsets are relative to the addresses in the file, before
11350 the @var{bias} argument is applied.
11354 @node Core File Generation
11355 @section How to Produce a Core File from Your Program
11356 @cindex dump core from inferior
11358 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11359 image of a running process and its process status (register values
11360 etc.). Its primary use is post-mortem debugging of a program that
11361 crashed while it ran outside a debugger. A program that crashes
11362 automatically produces a core file, unless this feature is disabled by
11363 the user. @xref{Files}, for information on invoking @value{GDBN} in
11364 the post-mortem debugging mode.
11366 Occasionally, you may wish to produce a core file of the program you
11367 are debugging in order to preserve a snapshot of its state.
11368 @value{GDBN} has a special command for that.
11372 @kindex generate-core-file
11373 @item generate-core-file [@var{file}]
11374 @itemx gcore [@var{file}]
11375 Produce a core dump of the inferior process. The optional argument
11376 @var{file} specifies the file name where to put the core dump. If not
11377 specified, the file name defaults to @file{core.@var{pid}}, where
11378 @var{pid} is the inferior process ID.
11380 Note that this command is implemented only for some systems (as of
11381 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11383 On @sc{gnu}/Linux, this command can take into account the value of the
11384 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11385 dump (@pxref{set use-coredump-filter}).
11387 @kindex set use-coredump-filter
11388 @anchor{set use-coredump-filter}
11389 @item set use-coredump-filter on
11390 @itemx set use-coredump-filter off
11391 Enable or disable the use of the file
11392 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11393 files. This file is used by the Linux kernel to decide what types of
11394 memory mappings will be dumped or ignored when generating a core dump
11395 file. @var{pid} is the process ID of a currently running process.
11397 To make use of this feature, you have to write in the
11398 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11399 which is a bit mask representing the memory mapping types. If a bit
11400 is set in the bit mask, then the memory mappings of the corresponding
11401 types will be dumped; otherwise, they will be ignored. This
11402 configuration is inherited by child processes. For more information
11403 about the bits that can be set in the
11404 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11405 manpage of @code{core(5)}.
11407 By default, this option is @code{on}. If this option is turned
11408 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11409 and instead uses the same default value as the Linux kernel in order
11410 to decide which pages will be dumped in the core dump file. This
11411 value is currently @code{0x33}, which means that bits @code{0}
11412 (anonymous private mappings), @code{1} (anonymous shared mappings),
11413 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11414 This will cause these memory mappings to be dumped automatically.
11417 @node Character Sets
11418 @section Character Sets
11419 @cindex character sets
11421 @cindex translating between character sets
11422 @cindex host character set
11423 @cindex target character set
11425 If the program you are debugging uses a different character set to
11426 represent characters and strings than the one @value{GDBN} uses itself,
11427 @value{GDBN} can automatically translate between the character sets for
11428 you. The character set @value{GDBN} uses we call the @dfn{host
11429 character set}; the one the inferior program uses we call the
11430 @dfn{target character set}.
11432 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11433 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11434 remote protocol (@pxref{Remote Debugging}) to debug a program
11435 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11436 then the host character set is Latin-1, and the target character set is
11437 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11438 target-charset EBCDIC-US}, then @value{GDBN} translates between
11439 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11440 character and string literals in expressions.
11442 @value{GDBN} has no way to automatically recognize which character set
11443 the inferior program uses; you must tell it, using the @code{set
11444 target-charset} command, described below.
11446 Here are the commands for controlling @value{GDBN}'s character set
11450 @item set target-charset @var{charset}
11451 @kindex set target-charset
11452 Set the current target character set to @var{charset}. To display the
11453 list of supported target character sets, type
11454 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11456 @item set host-charset @var{charset}
11457 @kindex set host-charset
11458 Set the current host character set to @var{charset}.
11460 By default, @value{GDBN} uses a host character set appropriate to the
11461 system it is running on; you can override that default using the
11462 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11463 automatically determine the appropriate host character set. In this
11464 case, @value{GDBN} uses @samp{UTF-8}.
11466 @value{GDBN} can only use certain character sets as its host character
11467 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11468 @value{GDBN} will list the host character sets it supports.
11470 @item set charset @var{charset}
11471 @kindex set charset
11472 Set the current host and target character sets to @var{charset}. As
11473 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11474 @value{GDBN} will list the names of the character sets that can be used
11475 for both host and target.
11478 @kindex show charset
11479 Show the names of the current host and target character sets.
11481 @item show host-charset
11482 @kindex show host-charset
11483 Show the name of the current host character set.
11485 @item show target-charset
11486 @kindex show target-charset
11487 Show the name of the current target character set.
11489 @item set target-wide-charset @var{charset}
11490 @kindex set target-wide-charset
11491 Set the current target's wide character set to @var{charset}. This is
11492 the character set used by the target's @code{wchar_t} type. To
11493 display the list of supported wide character sets, type
11494 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11496 @item show target-wide-charset
11497 @kindex show target-wide-charset
11498 Show the name of the current target's wide character set.
11501 Here is an example of @value{GDBN}'s character set support in action.
11502 Assume that the following source code has been placed in the file
11503 @file{charset-test.c}:
11509 = @{72, 101, 108, 108, 111, 44, 32, 119,
11510 111, 114, 108, 100, 33, 10, 0@};
11511 char ibm1047_hello[]
11512 = @{200, 133, 147, 147, 150, 107, 64, 166,
11513 150, 153, 147, 132, 90, 37, 0@};
11517 printf ("Hello, world!\n");
11521 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11522 containing the string @samp{Hello, world!} followed by a newline,
11523 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11525 We compile the program, and invoke the debugger on it:
11528 $ gcc -g charset-test.c -o charset-test
11529 $ gdb -nw charset-test
11530 GNU gdb 2001-12-19-cvs
11531 Copyright 2001 Free Software Foundation, Inc.
11536 We can use the @code{show charset} command to see what character sets
11537 @value{GDBN} is currently using to interpret and display characters and
11541 (@value{GDBP}) show charset
11542 The current host and target character set is `ISO-8859-1'.
11546 For the sake of printing this manual, let's use @sc{ascii} as our
11547 initial character set:
11549 (@value{GDBP}) set charset ASCII
11550 (@value{GDBP}) show charset
11551 The current host and target character set is `ASCII'.
11555 Let's assume that @sc{ascii} is indeed the correct character set for our
11556 host system --- in other words, let's assume that if @value{GDBN} prints
11557 characters using the @sc{ascii} character set, our terminal will display
11558 them properly. Since our current target character set is also
11559 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11562 (@value{GDBP}) print ascii_hello
11563 $1 = 0x401698 "Hello, world!\n"
11564 (@value{GDBP}) print ascii_hello[0]
11569 @value{GDBN} uses the target character set for character and string
11570 literals you use in expressions:
11573 (@value{GDBP}) print '+'
11578 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11581 @value{GDBN} relies on the user to tell it which character set the
11582 target program uses. If we print @code{ibm1047_hello} while our target
11583 character set is still @sc{ascii}, we get jibberish:
11586 (@value{GDBP}) print ibm1047_hello
11587 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11588 (@value{GDBP}) print ibm1047_hello[0]
11593 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11594 @value{GDBN} tells us the character sets it supports:
11597 (@value{GDBP}) set target-charset
11598 ASCII EBCDIC-US IBM1047 ISO-8859-1
11599 (@value{GDBP}) set target-charset
11602 We can select @sc{ibm1047} as our target character set, and examine the
11603 program's strings again. Now the @sc{ascii} string is wrong, but
11604 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11605 target character set, @sc{ibm1047}, to the host character set,
11606 @sc{ascii}, and they display correctly:
11609 (@value{GDBP}) set target-charset IBM1047
11610 (@value{GDBP}) show charset
11611 The current host character set is `ASCII'.
11612 The current target character set is `IBM1047'.
11613 (@value{GDBP}) print ascii_hello
11614 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11615 (@value{GDBP}) print ascii_hello[0]
11617 (@value{GDBP}) print ibm1047_hello
11618 $8 = 0x4016a8 "Hello, world!\n"
11619 (@value{GDBP}) print ibm1047_hello[0]
11624 As above, @value{GDBN} uses the target character set for character and
11625 string literals you use in expressions:
11628 (@value{GDBP}) print '+'
11633 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11636 @node Caching Target Data
11637 @section Caching Data of Targets
11638 @cindex caching data of targets
11640 @value{GDBN} caches data exchanged between the debugger and a target.
11641 Each cache is associated with the address space of the inferior.
11642 @xref{Inferiors and Programs}, about inferior and address space.
11643 Such caching generally improves performance in remote debugging
11644 (@pxref{Remote Debugging}), because it reduces the overhead of the
11645 remote protocol by bundling memory reads and writes into large chunks.
11646 Unfortunately, simply caching everything would lead to incorrect results,
11647 since @value{GDBN} does not necessarily know anything about volatile
11648 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11649 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11651 Therefore, by default, @value{GDBN} only caches data
11652 known to be on the stack@footnote{In non-stop mode, it is moderately
11653 rare for a running thread to modify the stack of a stopped thread
11654 in a way that would interfere with a backtrace, and caching of
11655 stack reads provides a significant speed up of remote backtraces.} or
11656 in the code segment.
11657 Other regions of memory can be explicitly marked as
11658 cacheable; @pxref{Memory Region Attributes}.
11661 @kindex set remotecache
11662 @item set remotecache on
11663 @itemx set remotecache off
11664 This option no longer does anything; it exists for compatibility
11667 @kindex show remotecache
11668 @item show remotecache
11669 Show the current state of the obsolete remotecache flag.
11671 @kindex set stack-cache
11672 @item set stack-cache on
11673 @itemx set stack-cache off
11674 Enable or disable caching of stack accesses. When @code{on}, use
11675 caching. By default, this option is @code{on}.
11677 @kindex show stack-cache
11678 @item show stack-cache
11679 Show the current state of data caching for memory accesses.
11681 @kindex set code-cache
11682 @item set code-cache on
11683 @itemx set code-cache off
11684 Enable or disable caching of code segment accesses. When @code{on},
11685 use caching. By default, this option is @code{on}. This improves
11686 performance of disassembly in remote debugging.
11688 @kindex show code-cache
11689 @item show code-cache
11690 Show the current state of target memory cache for code segment
11693 @kindex info dcache
11694 @item info dcache @r{[}line@r{]}
11695 Print the information about the performance of data cache of the
11696 current inferior's address space. The information displayed
11697 includes the dcache width and depth, and for each cache line, its
11698 number, address, and how many times it was referenced. This
11699 command is useful for debugging the data cache operation.
11701 If a line number is specified, the contents of that line will be
11704 @item set dcache size @var{size}
11705 @cindex dcache size
11706 @kindex set dcache size
11707 Set maximum number of entries in dcache (dcache depth above).
11709 @item set dcache line-size @var{line-size}
11710 @cindex dcache line-size
11711 @kindex set dcache line-size
11712 Set number of bytes each dcache entry caches (dcache width above).
11713 Must be a power of 2.
11715 @item show dcache size
11716 @kindex show dcache size
11717 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11719 @item show dcache line-size
11720 @kindex show dcache line-size
11721 Show default size of dcache lines.
11725 @node Searching Memory
11726 @section Search Memory
11727 @cindex searching memory
11729 Memory can be searched for a particular sequence of bytes with the
11730 @code{find} command.
11734 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11735 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11736 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11737 etc. The search begins at address @var{start_addr} and continues for either
11738 @var{len} bytes or through to @var{end_addr} inclusive.
11741 @var{s} and @var{n} are optional parameters.
11742 They may be specified in either order, apart or together.
11745 @item @var{s}, search query size
11746 The size of each search query value.
11752 halfwords (two bytes)
11756 giant words (eight bytes)
11759 All values are interpreted in the current language.
11760 This means, for example, that if the current source language is C/C@t{++}
11761 then searching for the string ``hello'' includes the trailing '\0'.
11763 If the value size is not specified, it is taken from the
11764 value's type in the current language.
11765 This is useful when one wants to specify the search
11766 pattern as a mixture of types.
11767 Note that this means, for example, that in the case of C-like languages
11768 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11769 which is typically four bytes.
11771 @item @var{n}, maximum number of finds
11772 The maximum number of matches to print. The default is to print all finds.
11775 You can use strings as search values. Quote them with double-quotes
11777 The string value is copied into the search pattern byte by byte,
11778 regardless of the endianness of the target and the size specification.
11780 The address of each match found is printed as well as a count of the
11781 number of matches found.
11783 The address of the last value found is stored in convenience variable
11785 A count of the number of matches is stored in @samp{$numfound}.
11787 For example, if stopped at the @code{printf} in this function:
11793 static char hello[] = "hello-hello";
11794 static struct @{ char c; short s; int i; @}
11795 __attribute__ ((packed)) mixed
11796 = @{ 'c', 0x1234, 0x87654321 @};
11797 printf ("%s\n", hello);
11802 you get during debugging:
11805 (gdb) find &hello[0], +sizeof(hello), "hello"
11806 0x804956d <hello.1620+6>
11808 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11809 0x8049567 <hello.1620>
11810 0x804956d <hello.1620+6>
11812 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11813 0x8049567 <hello.1620>
11815 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11816 0x8049560 <mixed.1625>
11818 (gdb) print $numfound
11821 $2 = (void *) 0x8049560
11825 @section Value Sizes
11827 Whenever @value{GDBN} prints a value memory will be allocated within
11828 @value{GDBN} to hold the contents of the value. It is possible in
11829 some languages with dynamic typing systems, that an invalid program
11830 may indicate a value that is incorrectly large, this in turn may cause
11831 @value{GDBN} to try and allocate an overly large ammount of memory.
11834 @kindex set max-value-size
11835 @item set max-value-size @var{bytes}
11836 @itemx set max-value-size unlimited
11837 Set the maximum size of memory that @value{GDBN} will allocate for the
11838 contents of a value to @var{bytes}, trying to display a value that
11839 requires more memory than that will result in an error.
11841 Setting this variable does not effect values that have already been
11842 allocated within @value{GDBN}, only future allocations.
11844 There's a minimum size that @code{max-value-size} can be set to in
11845 order that @value{GDBN} can still operate correctly, this minimum is
11846 currently 16 bytes.
11848 The limit applies to the results of some subexpressions as well as to
11849 complete expressions. For example, an expression denoting a simple
11850 integer component, such as @code{x.y.z}, may fail if the size of
11851 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11852 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11853 @var{A} is an array variable with non-constant size, will generally
11854 succeed regardless of the bounds on @var{A}, as long as the component
11855 size is less than @var{bytes}.
11857 The default value of @code{max-value-size} is currently 64k.
11859 @kindex show max-value-size
11860 @item show max-value-size
11861 Show the maximum size of memory, in bytes, that @value{GDBN} will
11862 allocate for the contents of a value.
11865 @node Optimized Code
11866 @chapter Debugging Optimized Code
11867 @cindex optimized code, debugging
11868 @cindex debugging optimized code
11870 Almost all compilers support optimization. With optimization
11871 disabled, the compiler generates assembly code that corresponds
11872 directly to your source code, in a simplistic way. As the compiler
11873 applies more powerful optimizations, the generated assembly code
11874 diverges from your original source code. With help from debugging
11875 information generated by the compiler, @value{GDBN} can map from
11876 the running program back to constructs from your original source.
11878 @value{GDBN} is more accurate with optimization disabled. If you
11879 can recompile without optimization, it is easier to follow the
11880 progress of your program during debugging. But, there are many cases
11881 where you may need to debug an optimized version.
11883 When you debug a program compiled with @samp{-g -O}, remember that the
11884 optimizer has rearranged your code; the debugger shows you what is
11885 really there. Do not be too surprised when the execution path does not
11886 exactly match your source file! An extreme example: if you define a
11887 variable, but never use it, @value{GDBN} never sees that
11888 variable---because the compiler optimizes it out of existence.
11890 Some things do not work as well with @samp{-g -O} as with just
11891 @samp{-g}, particularly on machines with instruction scheduling. If in
11892 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11893 please report it to us as a bug (including a test case!).
11894 @xref{Variables}, for more information about debugging optimized code.
11897 * Inline Functions:: How @value{GDBN} presents inlining
11898 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11901 @node Inline Functions
11902 @section Inline Functions
11903 @cindex inline functions, debugging
11905 @dfn{Inlining} is an optimization that inserts a copy of the function
11906 body directly at each call site, instead of jumping to a shared
11907 routine. @value{GDBN} displays inlined functions just like
11908 non-inlined functions. They appear in backtraces. You can view their
11909 arguments and local variables, step into them with @code{step}, skip
11910 them with @code{next}, and escape from them with @code{finish}.
11911 You can check whether a function was inlined by using the
11912 @code{info frame} command.
11914 For @value{GDBN} to support inlined functions, the compiler must
11915 record information about inlining in the debug information ---
11916 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11917 other compilers do also. @value{GDBN} only supports inlined functions
11918 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11919 do not emit two required attributes (@samp{DW_AT_call_file} and
11920 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11921 function calls with earlier versions of @value{NGCC}. It instead
11922 displays the arguments and local variables of inlined functions as
11923 local variables in the caller.
11925 The body of an inlined function is directly included at its call site;
11926 unlike a non-inlined function, there are no instructions devoted to
11927 the call. @value{GDBN} still pretends that the call site and the
11928 start of the inlined function are different instructions. Stepping to
11929 the call site shows the call site, and then stepping again shows
11930 the first line of the inlined function, even though no additional
11931 instructions are executed.
11933 This makes source-level debugging much clearer; you can see both the
11934 context of the call and then the effect of the call. Only stepping by
11935 a single instruction using @code{stepi} or @code{nexti} does not do
11936 this; single instruction steps always show the inlined body.
11938 There are some ways that @value{GDBN} does not pretend that inlined
11939 function calls are the same as normal calls:
11943 Setting breakpoints at the call site of an inlined function may not
11944 work, because the call site does not contain any code. @value{GDBN}
11945 may incorrectly move the breakpoint to the next line of the enclosing
11946 function, after the call. This limitation will be removed in a future
11947 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11948 or inside the inlined function instead.
11951 @value{GDBN} cannot locate the return value of inlined calls after
11952 using the @code{finish} command. This is a limitation of compiler-generated
11953 debugging information; after @code{finish}, you can step to the next line
11954 and print a variable where your program stored the return value.
11958 @node Tail Call Frames
11959 @section Tail Call Frames
11960 @cindex tail call frames, debugging
11962 Function @code{B} can call function @code{C} in its very last statement. In
11963 unoptimized compilation the call of @code{C} is immediately followed by return
11964 instruction at the end of @code{B} code. Optimizing compiler may replace the
11965 call and return in function @code{B} into one jump to function @code{C}
11966 instead. Such use of a jump instruction is called @dfn{tail call}.
11968 During execution of function @code{C}, there will be no indication in the
11969 function call stack frames that it was tail-called from @code{B}. If function
11970 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11971 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11972 some cases @value{GDBN} can determine that @code{C} was tail-called from
11973 @code{B}, and it will then create fictitious call frame for that, with the
11974 return address set up as if @code{B} called @code{C} normally.
11976 This functionality is currently supported only by DWARF 2 debugging format and
11977 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11978 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11981 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11982 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11986 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11988 Stack level 1, frame at 0x7fffffffda30:
11989 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11990 tail call frame, caller of frame at 0x7fffffffda30
11991 source language c++.
11992 Arglist at unknown address.
11993 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11996 The detection of all the possible code path executions can find them ambiguous.
11997 There is no execution history stored (possible @ref{Reverse Execution} is never
11998 used for this purpose) and the last known caller could have reached the known
11999 callee by multiple different jump sequences. In such case @value{GDBN} still
12000 tries to show at least all the unambiguous top tail callers and all the
12001 unambiguous bottom tail calees, if any.
12004 @anchor{set debug entry-values}
12005 @item set debug entry-values
12006 @kindex set debug entry-values
12007 When set to on, enables printing of analysis messages for both frame argument
12008 values at function entry and tail calls. It will show all the possible valid
12009 tail calls code paths it has considered. It will also print the intersection
12010 of them with the final unambiguous (possibly partial or even empty) code path
12013 @item show debug entry-values
12014 @kindex show debug entry-values
12015 Show the current state of analysis messages printing for both frame argument
12016 values at function entry and tail calls.
12019 The analysis messages for tail calls can for example show why the virtual tail
12020 call frame for function @code{c} has not been recognized (due to the indirect
12021 reference by variable @code{x}):
12024 static void __attribute__((noinline, noclone)) c (void);
12025 void (*x) (void) = c;
12026 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12027 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12028 int main (void) @{ x (); return 0; @}
12030 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12031 DW_TAG_GNU_call_site 0x40039a in main
12033 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12036 #1 0x000000000040039a in main () at t.c:5
12039 Another possibility is an ambiguous virtual tail call frames resolution:
12043 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12044 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12045 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12046 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12047 static void __attribute__((noinline, noclone)) b (void)
12048 @{ if (i) c (); else e (); @}
12049 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12050 int main (void) @{ a (); return 0; @}
12052 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12053 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12054 tailcall: reduced: 0x4004d2(a) |
12057 #1 0x00000000004004d2 in a () at t.c:8
12058 #2 0x0000000000400395 in main () at t.c:9
12061 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12062 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12064 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12065 @ifset HAVE_MAKEINFO_CLICK
12066 @set ARROW @click{}
12067 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12068 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12070 @ifclear HAVE_MAKEINFO_CLICK
12072 @set CALLSEQ1B @value{CALLSEQ1A}
12073 @set CALLSEQ2B @value{CALLSEQ2A}
12076 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12077 The code can have possible execution paths @value{CALLSEQ1B} or
12078 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12080 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12081 has found. It then finds another possible calling sequcen - that one is
12082 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12083 printed as the @code{reduced:} calling sequence. That one could have many
12084 futher @code{compare:} and @code{reduced:} statements as long as there remain
12085 any non-ambiguous sequence entries.
12087 For the frame of function @code{b} in both cases there are different possible
12088 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12089 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12090 therefore this one is displayed to the user while the ambiguous frames are
12093 There can be also reasons why printing of frame argument values at function
12098 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12099 static void __attribute__((noinline, noclone)) a (int i);
12100 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12101 static void __attribute__((noinline, noclone)) a (int i)
12102 @{ if (i) b (i - 1); else c (0); @}
12103 int main (void) @{ a (5); return 0; @}
12106 #0 c (i=i@@entry=0) at t.c:2
12107 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12108 function "a" at 0x400420 can call itself via tail calls
12109 i=<optimized out>) at t.c:6
12110 #2 0x000000000040036e in main () at t.c:7
12113 @value{GDBN} cannot find out from the inferior state if and how many times did
12114 function @code{a} call itself (via function @code{b}) as these calls would be
12115 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12116 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12117 prints @code{<optimized out>} instead.
12120 @chapter C Preprocessor Macros
12122 Some languages, such as C and C@t{++}, provide a way to define and invoke
12123 ``preprocessor macros'' which expand into strings of tokens.
12124 @value{GDBN} can evaluate expressions containing macro invocations, show
12125 the result of macro expansion, and show a macro's definition, including
12126 where it was defined.
12128 You may need to compile your program specially to provide @value{GDBN}
12129 with information about preprocessor macros. Most compilers do not
12130 include macros in their debugging information, even when you compile
12131 with the @option{-g} flag. @xref{Compilation}.
12133 A program may define a macro at one point, remove that definition later,
12134 and then provide a different definition after that. Thus, at different
12135 points in the program, a macro may have different definitions, or have
12136 no definition at all. If there is a current stack frame, @value{GDBN}
12137 uses the macros in scope at that frame's source code line. Otherwise,
12138 @value{GDBN} uses the macros in scope at the current listing location;
12141 Whenever @value{GDBN} evaluates an expression, it always expands any
12142 macro invocations present in the expression. @value{GDBN} also provides
12143 the following commands for working with macros explicitly.
12147 @kindex macro expand
12148 @cindex macro expansion, showing the results of preprocessor
12149 @cindex preprocessor macro expansion, showing the results of
12150 @cindex expanding preprocessor macros
12151 @item macro expand @var{expression}
12152 @itemx macro exp @var{expression}
12153 Show the results of expanding all preprocessor macro invocations in
12154 @var{expression}. Since @value{GDBN} simply expands macros, but does
12155 not parse the result, @var{expression} need not be a valid expression;
12156 it can be any string of tokens.
12159 @item macro expand-once @var{expression}
12160 @itemx macro exp1 @var{expression}
12161 @cindex expand macro once
12162 @i{(This command is not yet implemented.)} Show the results of
12163 expanding those preprocessor macro invocations that appear explicitly in
12164 @var{expression}. Macro invocations appearing in that expansion are
12165 left unchanged. This command allows you to see the effect of a
12166 particular macro more clearly, without being confused by further
12167 expansions. Since @value{GDBN} simply expands macros, but does not
12168 parse the result, @var{expression} need not be a valid expression; it
12169 can be any string of tokens.
12172 @cindex macro definition, showing
12173 @cindex definition of a macro, showing
12174 @cindex macros, from debug info
12175 @item info macro [-a|-all] [--] @var{macro}
12176 Show the current definition or all definitions of the named @var{macro},
12177 and describe the source location or compiler command-line where that
12178 definition was established. The optional double dash is to signify the end of
12179 argument processing and the beginning of @var{macro} for non C-like macros where
12180 the macro may begin with a hyphen.
12182 @kindex info macros
12183 @item info macros @var{location}
12184 Show all macro definitions that are in effect at the location specified
12185 by @var{location}, and describe the source location or compiler
12186 command-line where those definitions were established.
12188 @kindex macro define
12189 @cindex user-defined macros
12190 @cindex defining macros interactively
12191 @cindex macros, user-defined
12192 @item macro define @var{macro} @var{replacement-list}
12193 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12194 Introduce a definition for a preprocessor macro named @var{macro},
12195 invocations of which are replaced by the tokens given in
12196 @var{replacement-list}. The first form of this command defines an
12197 ``object-like'' macro, which takes no arguments; the second form
12198 defines a ``function-like'' macro, which takes the arguments given in
12201 A definition introduced by this command is in scope in every
12202 expression evaluated in @value{GDBN}, until it is removed with the
12203 @code{macro undef} command, described below. The definition overrides
12204 all definitions for @var{macro} present in the program being debugged,
12205 as well as any previous user-supplied definition.
12207 @kindex macro undef
12208 @item macro undef @var{macro}
12209 Remove any user-supplied definition for the macro named @var{macro}.
12210 This command only affects definitions provided with the @code{macro
12211 define} command, described above; it cannot remove definitions present
12212 in the program being debugged.
12216 List all the macros defined using the @code{macro define} command.
12219 @cindex macros, example of debugging with
12220 Here is a transcript showing the above commands in action. First, we
12221 show our source files:
12226 #include "sample.h"
12229 #define ADD(x) (M + x)
12234 printf ("Hello, world!\n");
12236 printf ("We're so creative.\n");
12238 printf ("Goodbye, world!\n");
12245 Now, we compile the program using the @sc{gnu} C compiler,
12246 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12247 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12248 and @option{-gdwarf-4}; we recommend always choosing the most recent
12249 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12250 includes information about preprocessor macros in the debugging
12254 $ gcc -gdwarf-2 -g3 sample.c -o sample
12258 Now, we start @value{GDBN} on our sample program:
12262 GNU gdb 2002-05-06-cvs
12263 Copyright 2002 Free Software Foundation, Inc.
12264 GDB is free software, @dots{}
12268 We can expand macros and examine their definitions, even when the
12269 program is not running. @value{GDBN} uses the current listing position
12270 to decide which macro definitions are in scope:
12273 (@value{GDBP}) list main
12276 5 #define ADD(x) (M + x)
12281 10 printf ("Hello, world!\n");
12283 12 printf ("We're so creative.\n");
12284 (@value{GDBP}) info macro ADD
12285 Defined at /home/jimb/gdb/macros/play/sample.c:5
12286 #define ADD(x) (M + x)
12287 (@value{GDBP}) info macro Q
12288 Defined at /home/jimb/gdb/macros/play/sample.h:1
12289 included at /home/jimb/gdb/macros/play/sample.c:2
12291 (@value{GDBP}) macro expand ADD(1)
12292 expands to: (42 + 1)
12293 (@value{GDBP}) macro expand-once ADD(1)
12294 expands to: once (M + 1)
12298 In the example above, note that @code{macro expand-once} expands only
12299 the macro invocation explicit in the original text --- the invocation of
12300 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12301 which was introduced by @code{ADD}.
12303 Once the program is running, @value{GDBN} uses the macro definitions in
12304 force at the source line of the current stack frame:
12307 (@value{GDBP}) break main
12308 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12310 Starting program: /home/jimb/gdb/macros/play/sample
12312 Breakpoint 1, main () at sample.c:10
12313 10 printf ("Hello, world!\n");
12317 At line 10, the definition of the macro @code{N} at line 9 is in force:
12320 (@value{GDBP}) info macro N
12321 Defined at /home/jimb/gdb/macros/play/sample.c:9
12323 (@value{GDBP}) macro expand N Q M
12324 expands to: 28 < 42
12325 (@value{GDBP}) print N Q M
12330 As we step over directives that remove @code{N}'s definition, and then
12331 give it a new definition, @value{GDBN} finds the definition (or lack
12332 thereof) in force at each point:
12335 (@value{GDBP}) next
12337 12 printf ("We're so creative.\n");
12338 (@value{GDBP}) info macro N
12339 The symbol `N' has no definition as a C/C++ preprocessor macro
12340 at /home/jimb/gdb/macros/play/sample.c:12
12341 (@value{GDBP}) next
12343 14 printf ("Goodbye, world!\n");
12344 (@value{GDBP}) info macro N
12345 Defined at /home/jimb/gdb/macros/play/sample.c:13
12347 (@value{GDBP}) macro expand N Q M
12348 expands to: 1729 < 42
12349 (@value{GDBP}) print N Q M
12354 In addition to source files, macros can be defined on the compilation command
12355 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12356 such a way, @value{GDBN} displays the location of their definition as line zero
12357 of the source file submitted to the compiler.
12360 (@value{GDBP}) info macro __STDC__
12361 Defined at /home/jimb/gdb/macros/play/sample.c:0
12368 @chapter Tracepoints
12369 @c This chapter is based on the documentation written by Michael
12370 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12372 @cindex tracepoints
12373 In some applications, it is not feasible for the debugger to interrupt
12374 the program's execution long enough for the developer to learn
12375 anything helpful about its behavior. If the program's correctness
12376 depends on its real-time behavior, delays introduced by a debugger
12377 might cause the program to change its behavior drastically, or perhaps
12378 fail, even when the code itself is correct. It is useful to be able
12379 to observe the program's behavior without interrupting it.
12381 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12382 specify locations in the program, called @dfn{tracepoints}, and
12383 arbitrary expressions to evaluate when those tracepoints are reached.
12384 Later, using the @code{tfind} command, you can examine the values
12385 those expressions had when the program hit the tracepoints. The
12386 expressions may also denote objects in memory---structures or arrays,
12387 for example---whose values @value{GDBN} should record; while visiting
12388 a particular tracepoint, you may inspect those objects as if they were
12389 in memory at that moment. However, because @value{GDBN} records these
12390 values without interacting with you, it can do so quickly and
12391 unobtrusively, hopefully not disturbing the program's behavior.
12393 The tracepoint facility is currently available only for remote
12394 targets. @xref{Targets}. In addition, your remote target must know
12395 how to collect trace data. This functionality is implemented in the
12396 remote stub; however, none of the stubs distributed with @value{GDBN}
12397 support tracepoints as of this writing. The format of the remote
12398 packets used to implement tracepoints are described in @ref{Tracepoint
12401 It is also possible to get trace data from a file, in a manner reminiscent
12402 of corefiles; you specify the filename, and use @code{tfind} to search
12403 through the file. @xref{Trace Files}, for more details.
12405 This chapter describes the tracepoint commands and features.
12408 * Set Tracepoints::
12409 * Analyze Collected Data::
12410 * Tracepoint Variables::
12414 @node Set Tracepoints
12415 @section Commands to Set Tracepoints
12417 Before running such a @dfn{trace experiment}, an arbitrary number of
12418 tracepoints can be set. A tracepoint is actually a special type of
12419 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12420 standard breakpoint commands. For instance, as with breakpoints,
12421 tracepoint numbers are successive integers starting from one, and many
12422 of the commands associated with tracepoints take the tracepoint number
12423 as their argument, to identify which tracepoint to work on.
12425 For each tracepoint, you can specify, in advance, some arbitrary set
12426 of data that you want the target to collect in the trace buffer when
12427 it hits that tracepoint. The collected data can include registers,
12428 local variables, or global data. Later, you can use @value{GDBN}
12429 commands to examine the values these data had at the time the
12430 tracepoint was hit.
12432 Tracepoints do not support every breakpoint feature. Ignore counts on
12433 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12434 commands when they are hit. Tracepoints may not be thread-specific
12437 @cindex fast tracepoints
12438 Some targets may support @dfn{fast tracepoints}, which are inserted in
12439 a different way (such as with a jump instead of a trap), that is
12440 faster but possibly restricted in where they may be installed.
12442 @cindex static tracepoints
12443 @cindex markers, static tracepoints
12444 @cindex probing markers, static tracepoints
12445 Regular and fast tracepoints are dynamic tracing facilities, meaning
12446 that they can be used to insert tracepoints at (almost) any location
12447 in the target. Some targets may also support controlling @dfn{static
12448 tracepoints} from @value{GDBN}. With static tracing, a set of
12449 instrumentation points, also known as @dfn{markers}, are embedded in
12450 the target program, and can be activated or deactivated by name or
12451 address. These are usually placed at locations which facilitate
12452 investigating what the target is actually doing. @value{GDBN}'s
12453 support for static tracing includes being able to list instrumentation
12454 points, and attach them with @value{GDBN} defined high level
12455 tracepoints that expose the whole range of convenience of
12456 @value{GDBN}'s tracepoints support. Namely, support for collecting
12457 registers values and values of global or local (to the instrumentation
12458 point) variables; tracepoint conditions and trace state variables.
12459 The act of installing a @value{GDBN} static tracepoint on an
12460 instrumentation point, or marker, is referred to as @dfn{probing} a
12461 static tracepoint marker.
12463 @code{gdbserver} supports tracepoints on some target systems.
12464 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12466 This section describes commands to set tracepoints and associated
12467 conditions and actions.
12470 * Create and Delete Tracepoints::
12471 * Enable and Disable Tracepoints::
12472 * Tracepoint Passcounts::
12473 * Tracepoint Conditions::
12474 * Trace State Variables::
12475 * Tracepoint Actions::
12476 * Listing Tracepoints::
12477 * Listing Static Tracepoint Markers::
12478 * Starting and Stopping Trace Experiments::
12479 * Tracepoint Restrictions::
12482 @node Create and Delete Tracepoints
12483 @subsection Create and Delete Tracepoints
12486 @cindex set tracepoint
12488 @item trace @var{location}
12489 The @code{trace} command is very similar to the @code{break} command.
12490 Its argument @var{location} can be any valid location.
12491 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12492 which is a point in the target program where the debugger will briefly stop,
12493 collect some data, and then allow the program to continue. Setting a tracepoint
12494 or changing its actions takes effect immediately if the remote stub
12495 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12497 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12498 these changes don't take effect until the next @code{tstart}
12499 command, and once a trace experiment is running, further changes will
12500 not have any effect until the next trace experiment starts. In addition,
12501 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12502 address is not yet resolved. (This is similar to pending breakpoints.)
12503 Pending tracepoints are not downloaded to the target and not installed
12504 until they are resolved. The resolution of pending tracepoints requires
12505 @value{GDBN} support---when debugging with the remote target, and
12506 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12507 tracing}), pending tracepoints can not be resolved (and downloaded to
12508 the remote stub) while @value{GDBN} is disconnected.
12510 Here are some examples of using the @code{trace} command:
12513 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12515 (@value{GDBP}) @b{trace +2} // 2 lines forward
12517 (@value{GDBP}) @b{trace my_function} // first source line of function
12519 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12521 (@value{GDBP}) @b{trace *0x2117c4} // an address
12525 You can abbreviate @code{trace} as @code{tr}.
12527 @item trace @var{location} if @var{cond}
12528 Set a tracepoint with condition @var{cond}; evaluate the expression
12529 @var{cond} each time the tracepoint is reached, and collect data only
12530 if the value is nonzero---that is, if @var{cond} evaluates as true.
12531 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12532 information on tracepoint conditions.
12534 @item ftrace @var{location} [ if @var{cond} ]
12535 @cindex set fast tracepoint
12536 @cindex fast tracepoints, setting
12538 The @code{ftrace} command sets a fast tracepoint. For targets that
12539 support them, fast tracepoints will use a more efficient but possibly
12540 less general technique to trigger data collection, such as a jump
12541 instruction instead of a trap, or some sort of hardware support. It
12542 may not be possible to create a fast tracepoint at the desired
12543 location, in which case the command will exit with an explanatory
12546 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12549 On 32-bit x86-architecture systems, fast tracepoints normally need to
12550 be placed at an instruction that is 5 bytes or longer, but can be
12551 placed at 4-byte instructions if the low 64K of memory of the target
12552 program is available to install trampolines. Some Unix-type systems,
12553 such as @sc{gnu}/Linux, exclude low addresses from the program's
12554 address space; but for instance with the Linux kernel it is possible
12555 to let @value{GDBN} use this area by doing a @command{sysctl} command
12556 to set the @code{mmap_min_addr} kernel parameter, as in
12559 sudo sysctl -w vm.mmap_min_addr=32768
12563 which sets the low address to 32K, which leaves plenty of room for
12564 trampolines. The minimum address should be set to a page boundary.
12566 @item strace @var{location} [ if @var{cond} ]
12567 @cindex set static tracepoint
12568 @cindex static tracepoints, setting
12569 @cindex probe static tracepoint marker
12571 The @code{strace} command sets a static tracepoint. For targets that
12572 support it, setting a static tracepoint probes a static
12573 instrumentation point, or marker, found at @var{location}. It may not
12574 be possible to set a static tracepoint at the desired location, in
12575 which case the command will exit with an explanatory message.
12577 @value{GDBN} handles arguments to @code{strace} exactly as for
12578 @code{trace}, with the addition that the user can also specify
12579 @code{-m @var{marker}} as @var{location}. This probes the marker
12580 identified by the @var{marker} string identifier. This identifier
12581 depends on the static tracepoint backend library your program is
12582 using. You can find all the marker identifiers in the @samp{ID} field
12583 of the @code{info static-tracepoint-markers} command output.
12584 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12585 Markers}. For example, in the following small program using the UST
12591 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12596 the marker id is composed of joining the first two arguments to the
12597 @code{trace_mark} call with a slash, which translates to:
12600 (@value{GDBP}) info static-tracepoint-markers
12601 Cnt Enb ID Address What
12602 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12608 so you may probe the marker above with:
12611 (@value{GDBP}) strace -m ust/bar33
12614 Static tracepoints accept an extra collect action --- @code{collect
12615 $_sdata}. This collects arbitrary user data passed in the probe point
12616 call to the tracing library. In the UST example above, you'll see
12617 that the third argument to @code{trace_mark} is a printf-like format
12618 string. The user data is then the result of running that formating
12619 string against the following arguments. Note that @code{info
12620 static-tracepoint-markers} command output lists that format string in
12621 the @samp{Data:} field.
12623 You can inspect this data when analyzing the trace buffer, by printing
12624 the $_sdata variable like any other variable available to
12625 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12628 @cindex last tracepoint number
12629 @cindex recent tracepoint number
12630 @cindex tracepoint number
12631 The convenience variable @code{$tpnum} records the tracepoint number
12632 of the most recently set tracepoint.
12634 @kindex delete tracepoint
12635 @cindex tracepoint deletion
12636 @item delete tracepoint @r{[}@var{num}@r{]}
12637 Permanently delete one or more tracepoints. With no argument, the
12638 default is to delete all tracepoints. Note that the regular
12639 @code{delete} command can remove tracepoints also.
12644 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12646 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12650 You can abbreviate this command as @code{del tr}.
12653 @node Enable and Disable Tracepoints
12654 @subsection Enable and Disable Tracepoints
12656 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12659 @kindex disable tracepoint
12660 @item disable tracepoint @r{[}@var{num}@r{]}
12661 Disable tracepoint @var{num}, or all tracepoints if no argument
12662 @var{num} is given. A disabled tracepoint will have no effect during
12663 a trace experiment, but it is not forgotten. You can re-enable
12664 a disabled tracepoint using the @code{enable tracepoint} command.
12665 If the command is issued during a trace experiment and the debug target
12666 has support for disabling tracepoints during a trace experiment, then the
12667 change will be effective immediately. Otherwise, it will be applied to the
12668 next trace experiment.
12670 @kindex enable tracepoint
12671 @item enable tracepoint @r{[}@var{num}@r{]}
12672 Enable tracepoint @var{num}, or all tracepoints. If this command is
12673 issued during a trace experiment and the debug target supports enabling
12674 tracepoints during a trace experiment, then the enabled tracepoints will
12675 become effective immediately. Otherwise, they will become effective the
12676 next time a trace experiment is run.
12679 @node Tracepoint Passcounts
12680 @subsection Tracepoint Passcounts
12684 @cindex tracepoint pass count
12685 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12686 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12687 automatically stop a trace experiment. If a tracepoint's passcount is
12688 @var{n}, then the trace experiment will be automatically stopped on
12689 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12690 @var{num} is not specified, the @code{passcount} command sets the
12691 passcount of the most recently defined tracepoint. If no passcount is
12692 given, the trace experiment will run until stopped explicitly by the
12698 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12699 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12701 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12702 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12703 (@value{GDBP}) @b{trace foo}
12704 (@value{GDBP}) @b{pass 3}
12705 (@value{GDBP}) @b{trace bar}
12706 (@value{GDBP}) @b{pass 2}
12707 (@value{GDBP}) @b{trace baz}
12708 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12709 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12710 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12711 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12715 @node Tracepoint Conditions
12716 @subsection Tracepoint Conditions
12717 @cindex conditional tracepoints
12718 @cindex tracepoint conditions
12720 The simplest sort of tracepoint collects data every time your program
12721 reaches a specified place. You can also specify a @dfn{condition} for
12722 a tracepoint. A condition is just a Boolean expression in your
12723 programming language (@pxref{Expressions, ,Expressions}). A
12724 tracepoint with a condition evaluates the expression each time your
12725 program reaches it, and data collection happens only if the condition
12728 Tracepoint conditions can be specified when a tracepoint is set, by
12729 using @samp{if} in the arguments to the @code{trace} command.
12730 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12731 also be set or changed at any time with the @code{condition} command,
12732 just as with breakpoints.
12734 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12735 the conditional expression itself. Instead, @value{GDBN} encodes the
12736 expression into an agent expression (@pxref{Agent Expressions})
12737 suitable for execution on the target, independently of @value{GDBN}.
12738 Global variables become raw memory locations, locals become stack
12739 accesses, and so forth.
12741 For instance, suppose you have a function that is usually called
12742 frequently, but should not be called after an error has occurred. You
12743 could use the following tracepoint command to collect data about calls
12744 of that function that happen while the error code is propagating
12745 through the program; an unconditional tracepoint could end up
12746 collecting thousands of useless trace frames that you would have to
12750 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12753 @node Trace State Variables
12754 @subsection Trace State Variables
12755 @cindex trace state variables
12757 A @dfn{trace state variable} is a special type of variable that is
12758 created and managed by target-side code. The syntax is the same as
12759 that for GDB's convenience variables (a string prefixed with ``$''),
12760 but they are stored on the target. They must be created explicitly,
12761 using a @code{tvariable} command. They are always 64-bit signed
12764 Trace state variables are remembered by @value{GDBN}, and downloaded
12765 to the target along with tracepoint information when the trace
12766 experiment starts. There are no intrinsic limits on the number of
12767 trace state variables, beyond memory limitations of the target.
12769 @cindex convenience variables, and trace state variables
12770 Although trace state variables are managed by the target, you can use
12771 them in print commands and expressions as if they were convenience
12772 variables; @value{GDBN} will get the current value from the target
12773 while the trace experiment is running. Trace state variables share
12774 the same namespace as other ``$'' variables, which means that you
12775 cannot have trace state variables with names like @code{$23} or
12776 @code{$pc}, nor can you have a trace state variable and a convenience
12777 variable with the same name.
12781 @item tvariable $@var{name} [ = @var{expression} ]
12783 The @code{tvariable} command creates a new trace state variable named
12784 @code{$@var{name}}, and optionally gives it an initial value of
12785 @var{expression}. The @var{expression} is evaluated when this command is
12786 entered; the result will be converted to an integer if possible,
12787 otherwise @value{GDBN} will report an error. A subsequent
12788 @code{tvariable} command specifying the same name does not create a
12789 variable, but instead assigns the supplied initial value to the
12790 existing variable of that name, overwriting any previous initial
12791 value. The default initial value is 0.
12793 @item info tvariables
12794 @kindex info tvariables
12795 List all the trace state variables along with their initial values.
12796 Their current values may also be displayed, if the trace experiment is
12799 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12800 @kindex delete tvariable
12801 Delete the given trace state variables, or all of them if no arguments
12806 @node Tracepoint Actions
12807 @subsection Tracepoint Action Lists
12811 @cindex tracepoint actions
12812 @item actions @r{[}@var{num}@r{]}
12813 This command will prompt for a list of actions to be taken when the
12814 tracepoint is hit. If the tracepoint number @var{num} is not
12815 specified, this command sets the actions for the one that was most
12816 recently defined (so that you can define a tracepoint and then say
12817 @code{actions} without bothering about its number). You specify the
12818 actions themselves on the following lines, one action at a time, and
12819 terminate the actions list with a line containing just @code{end}. So
12820 far, the only defined actions are @code{collect}, @code{teval}, and
12821 @code{while-stepping}.
12823 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12824 Commands, ,Breakpoint Command Lists}), except that only the defined
12825 actions are allowed; any other @value{GDBN} command is rejected.
12827 @cindex remove actions from a tracepoint
12828 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12829 and follow it immediately with @samp{end}.
12832 (@value{GDBP}) @b{collect @var{data}} // collect some data
12834 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12836 (@value{GDBP}) @b{end} // signals the end of actions.
12839 In the following example, the action list begins with @code{collect}
12840 commands indicating the things to be collected when the tracepoint is
12841 hit. Then, in order to single-step and collect additional data
12842 following the tracepoint, a @code{while-stepping} command is used,
12843 followed by the list of things to be collected after each step in a
12844 sequence of single steps. The @code{while-stepping} command is
12845 terminated by its own separate @code{end} command. Lastly, the action
12846 list is terminated by an @code{end} command.
12849 (@value{GDBP}) @b{trace foo}
12850 (@value{GDBP}) @b{actions}
12851 Enter actions for tracepoint 1, one per line:
12854 > while-stepping 12
12855 > collect $pc, arr[i]
12860 @kindex collect @r{(tracepoints)}
12861 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12862 Collect values of the given expressions when the tracepoint is hit.
12863 This command accepts a comma-separated list of any valid expressions.
12864 In addition to global, static, or local variables, the following
12865 special arguments are supported:
12869 Collect all registers.
12872 Collect all function arguments.
12875 Collect all local variables.
12878 Collect the return address. This is helpful if you want to see more
12881 @emph{Note:} The return address location can not always be reliably
12882 determined up front, and the wrong address / registers may end up
12883 collected instead. On some architectures the reliability is higher
12884 for tracepoints at function entry, while on others it's the opposite.
12885 When this happens, backtracing will stop because the return address is
12886 found unavailable (unless another collect rule happened to match it).
12889 Collects the number of arguments from the static probe at which the
12890 tracepoint is located.
12891 @xref{Static Probe Points}.
12893 @item $_probe_arg@var{n}
12894 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12895 from the static probe at which the tracepoint is located.
12896 @xref{Static Probe Points}.
12899 @vindex $_sdata@r{, collect}
12900 Collect static tracepoint marker specific data. Only available for
12901 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12902 Lists}. On the UST static tracepoints library backend, an
12903 instrumentation point resembles a @code{printf} function call. The
12904 tracing library is able to collect user specified data formatted to a
12905 character string using the format provided by the programmer that
12906 instrumented the program. Other backends have similar mechanisms.
12907 Here's an example of a UST marker call:
12910 const char master_name[] = "$your_name";
12911 trace_mark(channel1, marker1, "hello %s", master_name)
12914 In this case, collecting @code{$_sdata} collects the string
12915 @samp{hello $yourname}. When analyzing the trace buffer, you can
12916 inspect @samp{$_sdata} like any other variable available to
12920 You can give several consecutive @code{collect} commands, each one
12921 with a single argument, or one @code{collect} command with several
12922 arguments separated by commas; the effect is the same.
12924 The optional @var{mods} changes the usual handling of the arguments.
12925 @code{s} requests that pointers to chars be handled as strings, in
12926 particular collecting the contents of the memory being pointed at, up
12927 to the first zero. The upper bound is by default the value of the
12928 @code{print elements} variable; if @code{s} is followed by a decimal
12929 number, that is the upper bound instead. So for instance
12930 @samp{collect/s25 mystr} collects as many as 25 characters at
12933 The command @code{info scope} (@pxref{Symbols, info scope}) is
12934 particularly useful for figuring out what data to collect.
12936 @kindex teval @r{(tracepoints)}
12937 @item teval @var{expr1}, @var{expr2}, @dots{}
12938 Evaluate the given expressions when the tracepoint is hit. This
12939 command accepts a comma-separated list of expressions. The results
12940 are discarded, so this is mainly useful for assigning values to trace
12941 state variables (@pxref{Trace State Variables}) without adding those
12942 values to the trace buffer, as would be the case if the @code{collect}
12945 @kindex while-stepping @r{(tracepoints)}
12946 @item while-stepping @var{n}
12947 Perform @var{n} single-step instruction traces after the tracepoint,
12948 collecting new data after each step. The @code{while-stepping}
12949 command is followed by the list of what to collect while stepping
12950 (followed by its own @code{end} command):
12953 > while-stepping 12
12954 > collect $regs, myglobal
12960 Note that @code{$pc} is not automatically collected by
12961 @code{while-stepping}; you need to explicitly collect that register if
12962 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12965 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12966 @kindex set default-collect
12967 @cindex default collection action
12968 This variable is a list of expressions to collect at each tracepoint
12969 hit. It is effectively an additional @code{collect} action prepended
12970 to every tracepoint action list. The expressions are parsed
12971 individually for each tracepoint, so for instance a variable named
12972 @code{xyz} may be interpreted as a global for one tracepoint, and a
12973 local for another, as appropriate to the tracepoint's location.
12975 @item show default-collect
12976 @kindex show default-collect
12977 Show the list of expressions that are collected by default at each
12982 @node Listing Tracepoints
12983 @subsection Listing Tracepoints
12986 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12987 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12988 @cindex information about tracepoints
12989 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12990 Display information about the tracepoint @var{num}. If you don't
12991 specify a tracepoint number, displays information about all the
12992 tracepoints defined so far. The format is similar to that used for
12993 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12994 command, simply restricting itself to tracepoints.
12996 A tracepoint's listing may include additional information specific to
13001 its passcount as given by the @code{passcount @var{n}} command
13004 the state about installed on target of each location
13008 (@value{GDBP}) @b{info trace}
13009 Num Type Disp Enb Address What
13010 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13012 collect globfoo, $regs
13017 2 tracepoint keep y <MULTIPLE>
13019 2.1 y 0x0804859c in func4 at change-loc.h:35
13020 installed on target
13021 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13022 installed on target
13023 2.3 y <PENDING> set_tracepoint
13024 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13025 not installed on target
13030 This command can be abbreviated @code{info tp}.
13033 @node Listing Static Tracepoint Markers
13034 @subsection Listing Static Tracepoint Markers
13037 @kindex info static-tracepoint-markers
13038 @cindex information about static tracepoint markers
13039 @item info static-tracepoint-markers
13040 Display information about all static tracepoint markers defined in the
13043 For each marker, the following columns are printed:
13047 An incrementing counter, output to help readability. This is not a
13050 The marker ID, as reported by the target.
13051 @item Enabled or Disabled
13052 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13053 that are not enabled.
13055 Where the marker is in your program, as a memory address.
13057 Where the marker is in the source for your program, as a file and line
13058 number. If the debug information included in the program does not
13059 allow @value{GDBN} to locate the source of the marker, this column
13060 will be left blank.
13064 In addition, the following information may be printed for each marker:
13068 User data passed to the tracing library by the marker call. In the
13069 UST backend, this is the format string passed as argument to the
13071 @item Static tracepoints probing the marker
13072 The list of static tracepoints attached to the marker.
13076 (@value{GDBP}) info static-tracepoint-markers
13077 Cnt ID Enb Address What
13078 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13079 Data: number1 %d number2 %d
13080 Probed by static tracepoints: #2
13081 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13087 @node Starting and Stopping Trace Experiments
13088 @subsection Starting and Stopping Trace Experiments
13091 @kindex tstart [ @var{notes} ]
13092 @cindex start a new trace experiment
13093 @cindex collected data discarded
13095 This command starts the trace experiment, and begins collecting data.
13096 It has the side effect of discarding all the data collected in the
13097 trace buffer during the previous trace experiment. If any arguments
13098 are supplied, they are taken as a note and stored with the trace
13099 experiment's state. The notes may be arbitrary text, and are
13100 especially useful with disconnected tracing in a multi-user context;
13101 the notes can explain what the trace is doing, supply user contact
13102 information, and so forth.
13104 @kindex tstop [ @var{notes} ]
13105 @cindex stop a running trace experiment
13107 This command stops the trace experiment. If any arguments are
13108 supplied, they are recorded with the experiment as a note. This is
13109 useful if you are stopping a trace started by someone else, for
13110 instance if the trace is interfering with the system's behavior and
13111 needs to be stopped quickly.
13113 @strong{Note}: a trace experiment and data collection may stop
13114 automatically if any tracepoint's passcount is reached
13115 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13118 @cindex status of trace data collection
13119 @cindex trace experiment, status of
13121 This command displays the status of the current trace data
13125 Here is an example of the commands we described so far:
13128 (@value{GDBP}) @b{trace gdb_c_test}
13129 (@value{GDBP}) @b{actions}
13130 Enter actions for tracepoint #1, one per line.
13131 > collect $regs,$locals,$args
13132 > while-stepping 11
13136 (@value{GDBP}) @b{tstart}
13137 [time passes @dots{}]
13138 (@value{GDBP}) @b{tstop}
13141 @anchor{disconnected tracing}
13142 @cindex disconnected tracing
13143 You can choose to continue running the trace experiment even if
13144 @value{GDBN} disconnects from the target, voluntarily or
13145 involuntarily. For commands such as @code{detach}, the debugger will
13146 ask what you want to do with the trace. But for unexpected
13147 terminations (@value{GDBN} crash, network outage), it would be
13148 unfortunate to lose hard-won trace data, so the variable
13149 @code{disconnected-tracing} lets you decide whether the trace should
13150 continue running without @value{GDBN}.
13153 @item set disconnected-tracing on
13154 @itemx set disconnected-tracing off
13155 @kindex set disconnected-tracing
13156 Choose whether a tracing run should continue to run if @value{GDBN}
13157 has disconnected from the target. Note that @code{detach} or
13158 @code{quit} will ask you directly what to do about a running trace no
13159 matter what this variable's setting, so the variable is mainly useful
13160 for handling unexpected situations, such as loss of the network.
13162 @item show disconnected-tracing
13163 @kindex show disconnected-tracing
13164 Show the current choice for disconnected tracing.
13168 When you reconnect to the target, the trace experiment may or may not
13169 still be running; it might have filled the trace buffer in the
13170 meantime, or stopped for one of the other reasons. If it is running,
13171 it will continue after reconnection.
13173 Upon reconnection, the target will upload information about the
13174 tracepoints in effect. @value{GDBN} will then compare that
13175 information to the set of tracepoints currently defined, and attempt
13176 to match them up, allowing for the possibility that the numbers may
13177 have changed due to creation and deletion in the meantime. If one of
13178 the target's tracepoints does not match any in @value{GDBN}, the
13179 debugger will create a new tracepoint, so that you have a number with
13180 which to specify that tracepoint. This matching-up process is
13181 necessarily heuristic, and it may result in useless tracepoints being
13182 created; you may simply delete them if they are of no use.
13184 @cindex circular trace buffer
13185 If your target agent supports a @dfn{circular trace buffer}, then you
13186 can run a trace experiment indefinitely without filling the trace
13187 buffer; when space runs out, the agent deletes already-collected trace
13188 frames, oldest first, until there is enough room to continue
13189 collecting. This is especially useful if your tracepoints are being
13190 hit too often, and your trace gets terminated prematurely because the
13191 buffer is full. To ask for a circular trace buffer, simply set
13192 @samp{circular-trace-buffer} to on. You can set this at any time,
13193 including during tracing; if the agent can do it, it will change
13194 buffer handling on the fly, otherwise it will not take effect until
13198 @item set circular-trace-buffer on
13199 @itemx set circular-trace-buffer off
13200 @kindex set circular-trace-buffer
13201 Choose whether a tracing run should use a linear or circular buffer
13202 for trace data. A linear buffer will not lose any trace data, but may
13203 fill up prematurely, while a circular buffer will discard old trace
13204 data, but it will have always room for the latest tracepoint hits.
13206 @item show circular-trace-buffer
13207 @kindex show circular-trace-buffer
13208 Show the current choice for the trace buffer. Note that this may not
13209 match the agent's current buffer handling, nor is it guaranteed to
13210 match the setting that might have been in effect during a past run,
13211 for instance if you are looking at frames from a trace file.
13216 @item set trace-buffer-size @var{n}
13217 @itemx set trace-buffer-size unlimited
13218 @kindex set trace-buffer-size
13219 Request that the target use a trace buffer of @var{n} bytes. Not all
13220 targets will honor the request; they may have a compiled-in size for
13221 the trace buffer, or some other limitation. Set to a value of
13222 @code{unlimited} or @code{-1} to let the target use whatever size it
13223 likes. This is also the default.
13225 @item show trace-buffer-size
13226 @kindex show trace-buffer-size
13227 Show the current requested size for the trace buffer. Note that this
13228 will only match the actual size if the target supports size-setting,
13229 and was able to handle the requested size. For instance, if the
13230 target can only change buffer size between runs, this variable will
13231 not reflect the change until the next run starts. Use @code{tstatus}
13232 to get a report of the actual buffer size.
13236 @item set trace-user @var{text}
13237 @kindex set trace-user
13239 @item show trace-user
13240 @kindex show trace-user
13242 @item set trace-notes @var{text}
13243 @kindex set trace-notes
13244 Set the trace run's notes.
13246 @item show trace-notes
13247 @kindex show trace-notes
13248 Show the trace run's notes.
13250 @item set trace-stop-notes @var{text}
13251 @kindex set trace-stop-notes
13252 Set the trace run's stop notes. The handling of the note is as for
13253 @code{tstop} arguments; the set command is convenient way to fix a
13254 stop note that is mistaken or incomplete.
13256 @item show trace-stop-notes
13257 @kindex show trace-stop-notes
13258 Show the trace run's stop notes.
13262 @node Tracepoint Restrictions
13263 @subsection Tracepoint Restrictions
13265 @cindex tracepoint restrictions
13266 There are a number of restrictions on the use of tracepoints. As
13267 described above, tracepoint data gathering occurs on the target
13268 without interaction from @value{GDBN}. Thus the full capabilities of
13269 the debugger are not available during data gathering, and then at data
13270 examination time, you will be limited by only having what was
13271 collected. The following items describe some common problems, but it
13272 is not exhaustive, and you may run into additional difficulties not
13278 Tracepoint expressions are intended to gather objects (lvalues). Thus
13279 the full flexibility of GDB's expression evaluator is not available.
13280 You cannot call functions, cast objects to aggregate types, access
13281 convenience variables or modify values (except by assignment to trace
13282 state variables). Some language features may implicitly call
13283 functions (for instance Objective-C fields with accessors), and therefore
13284 cannot be collected either.
13287 Collection of local variables, either individually or in bulk with
13288 @code{$locals} or @code{$args}, during @code{while-stepping} may
13289 behave erratically. The stepping action may enter a new scope (for
13290 instance by stepping into a function), or the location of the variable
13291 may change (for instance it is loaded into a register). The
13292 tracepoint data recorded uses the location information for the
13293 variables that is correct for the tracepoint location. When the
13294 tracepoint is created, it is not possible, in general, to determine
13295 where the steps of a @code{while-stepping} sequence will advance the
13296 program---particularly if a conditional branch is stepped.
13299 Collection of an incompletely-initialized or partially-destroyed object
13300 may result in something that @value{GDBN} cannot display, or displays
13301 in a misleading way.
13304 When @value{GDBN} displays a pointer to character it automatically
13305 dereferences the pointer to also display characters of the string
13306 being pointed to. However, collecting the pointer during tracing does
13307 not automatically collect the string. You need to explicitly
13308 dereference the pointer and provide size information if you want to
13309 collect not only the pointer, but the memory pointed to. For example,
13310 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13314 It is not possible to collect a complete stack backtrace at a
13315 tracepoint. Instead, you may collect the registers and a few hundred
13316 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13317 (adjust to use the name of the actual stack pointer register on your
13318 target architecture, and the amount of stack you wish to capture).
13319 Then the @code{backtrace} command will show a partial backtrace when
13320 using a trace frame. The number of stack frames that can be examined
13321 depends on the sizes of the frames in the collected stack. Note that
13322 if you ask for a block so large that it goes past the bottom of the
13323 stack, the target agent may report an error trying to read from an
13327 If you do not collect registers at a tracepoint, @value{GDBN} can
13328 infer that the value of @code{$pc} must be the same as the address of
13329 the tracepoint and use that when you are looking at a trace frame
13330 for that tracepoint. However, this cannot work if the tracepoint has
13331 multiple locations (for instance if it was set in a function that was
13332 inlined), or if it has a @code{while-stepping} loop. In those cases
13333 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13338 @node Analyze Collected Data
13339 @section Using the Collected Data
13341 After the tracepoint experiment ends, you use @value{GDBN} commands
13342 for examining the trace data. The basic idea is that each tracepoint
13343 collects a trace @dfn{snapshot} every time it is hit and another
13344 snapshot every time it single-steps. All these snapshots are
13345 consecutively numbered from zero and go into a buffer, and you can
13346 examine them later. The way you examine them is to @dfn{focus} on a
13347 specific trace snapshot. When the remote stub is focused on a trace
13348 snapshot, it will respond to all @value{GDBN} requests for memory and
13349 registers by reading from the buffer which belongs to that snapshot,
13350 rather than from @emph{real} memory or registers of the program being
13351 debugged. This means that @strong{all} @value{GDBN} commands
13352 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13353 behave as if we were currently debugging the program state as it was
13354 when the tracepoint occurred. Any requests for data that are not in
13355 the buffer will fail.
13358 * tfind:: How to select a trace snapshot
13359 * tdump:: How to display all data for a snapshot
13360 * save tracepoints:: How to save tracepoints for a future run
13364 @subsection @code{tfind @var{n}}
13367 @cindex select trace snapshot
13368 @cindex find trace snapshot
13369 The basic command for selecting a trace snapshot from the buffer is
13370 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13371 counting from zero. If no argument @var{n} is given, the next
13372 snapshot is selected.
13374 Here are the various forms of using the @code{tfind} command.
13378 Find the first snapshot in the buffer. This is a synonym for
13379 @code{tfind 0} (since 0 is the number of the first snapshot).
13382 Stop debugging trace snapshots, resume @emph{live} debugging.
13385 Same as @samp{tfind none}.
13388 No argument means find the next trace snapshot.
13391 Find the previous trace snapshot before the current one. This permits
13392 retracing earlier steps.
13394 @item tfind tracepoint @var{num}
13395 Find the next snapshot associated with tracepoint @var{num}. Search
13396 proceeds forward from the last examined trace snapshot. If no
13397 argument @var{num} is given, it means find the next snapshot collected
13398 for the same tracepoint as the current snapshot.
13400 @item tfind pc @var{addr}
13401 Find the next snapshot associated with the value @var{addr} of the
13402 program counter. Search proceeds forward from the last examined trace
13403 snapshot. If no argument @var{addr} is given, it means find the next
13404 snapshot with the same value of PC as the current snapshot.
13406 @item tfind outside @var{addr1}, @var{addr2}
13407 Find the next snapshot whose PC is outside the given range of
13408 addresses (exclusive).
13410 @item tfind range @var{addr1}, @var{addr2}
13411 Find the next snapshot whose PC is between @var{addr1} and
13412 @var{addr2} (inclusive).
13414 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13415 Find the next snapshot associated with the source line @var{n}. If
13416 the optional argument @var{file} is given, refer to line @var{n} in
13417 that source file. Search proceeds forward from the last examined
13418 trace snapshot. If no argument @var{n} is given, it means find the
13419 next line other than the one currently being examined; thus saying
13420 @code{tfind line} repeatedly can appear to have the same effect as
13421 stepping from line to line in a @emph{live} debugging session.
13424 The default arguments for the @code{tfind} commands are specifically
13425 designed to make it easy to scan through the trace buffer. For
13426 instance, @code{tfind} with no argument selects the next trace
13427 snapshot, and @code{tfind -} with no argument selects the previous
13428 trace snapshot. So, by giving one @code{tfind} command, and then
13429 simply hitting @key{RET} repeatedly you can examine all the trace
13430 snapshots in order. Or, by saying @code{tfind -} and then hitting
13431 @key{RET} repeatedly you can examine the snapshots in reverse order.
13432 The @code{tfind line} command with no argument selects the snapshot
13433 for the next source line executed. The @code{tfind pc} command with
13434 no argument selects the next snapshot with the same program counter
13435 (PC) as the current frame. The @code{tfind tracepoint} command with
13436 no argument selects the next trace snapshot collected by the same
13437 tracepoint as the current one.
13439 In addition to letting you scan through the trace buffer manually,
13440 these commands make it easy to construct @value{GDBN} scripts that
13441 scan through the trace buffer and print out whatever collected data
13442 you are interested in. Thus, if we want to examine the PC, FP, and SP
13443 registers from each trace frame in the buffer, we can say this:
13446 (@value{GDBP}) @b{tfind start}
13447 (@value{GDBP}) @b{while ($trace_frame != -1)}
13448 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13449 $trace_frame, $pc, $sp, $fp
13453 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13454 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13455 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13456 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13457 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13458 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13459 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13460 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13461 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13462 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13463 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13466 Or, if we want to examine the variable @code{X} at each source line in
13470 (@value{GDBP}) @b{tfind start}
13471 (@value{GDBP}) @b{while ($trace_frame != -1)}
13472 > printf "Frame %d, X == %d\n", $trace_frame, X
13482 @subsection @code{tdump}
13484 @cindex dump all data collected at tracepoint
13485 @cindex tracepoint data, display
13487 This command takes no arguments. It prints all the data collected at
13488 the current trace snapshot.
13491 (@value{GDBP}) @b{trace 444}
13492 (@value{GDBP}) @b{actions}
13493 Enter actions for tracepoint #2, one per line:
13494 > collect $regs, $locals, $args, gdb_long_test
13497 (@value{GDBP}) @b{tstart}
13499 (@value{GDBP}) @b{tfind line 444}
13500 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13502 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13504 (@value{GDBP}) @b{tdump}
13505 Data collected at tracepoint 2, trace frame 1:
13506 d0 0xc4aa0085 -995491707
13510 d4 0x71aea3d 119204413
13513 d7 0x380035 3670069
13514 a0 0x19e24a 1696330
13515 a1 0x3000668 50333288
13517 a3 0x322000 3284992
13518 a4 0x3000698 50333336
13519 a5 0x1ad3cc 1758156
13520 fp 0x30bf3c 0x30bf3c
13521 sp 0x30bf34 0x30bf34
13523 pc 0x20b2c8 0x20b2c8
13527 p = 0x20e5b4 "gdb-test"
13534 gdb_long_test = 17 '\021'
13539 @code{tdump} works by scanning the tracepoint's current collection
13540 actions and printing the value of each expression listed. So
13541 @code{tdump} can fail, if after a run, you change the tracepoint's
13542 actions to mention variables that were not collected during the run.
13544 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13545 uses the collected value of @code{$pc} to distinguish between trace
13546 frames that were collected at the tracepoint hit, and frames that were
13547 collected while stepping. This allows it to correctly choose whether
13548 to display the basic list of collections, or the collections from the
13549 body of the while-stepping loop. However, if @code{$pc} was not collected,
13550 then @code{tdump} will always attempt to dump using the basic collection
13551 list, and may fail if a while-stepping frame does not include all the
13552 same data that is collected at the tracepoint hit.
13553 @c This is getting pretty arcane, example would be good.
13555 @node save tracepoints
13556 @subsection @code{save tracepoints @var{filename}}
13557 @kindex save tracepoints
13558 @kindex save-tracepoints
13559 @cindex save tracepoints for future sessions
13561 This command saves all current tracepoint definitions together with
13562 their actions and passcounts, into a file @file{@var{filename}}
13563 suitable for use in a later debugging session. To read the saved
13564 tracepoint definitions, use the @code{source} command (@pxref{Command
13565 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13566 alias for @w{@code{save tracepoints}}
13568 @node Tracepoint Variables
13569 @section Convenience Variables for Tracepoints
13570 @cindex tracepoint variables
13571 @cindex convenience variables for tracepoints
13574 @vindex $trace_frame
13575 @item (int) $trace_frame
13576 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13577 snapshot is selected.
13579 @vindex $tracepoint
13580 @item (int) $tracepoint
13581 The tracepoint for the current trace snapshot.
13583 @vindex $trace_line
13584 @item (int) $trace_line
13585 The line number for the current trace snapshot.
13587 @vindex $trace_file
13588 @item (char []) $trace_file
13589 The source file for the current trace snapshot.
13591 @vindex $trace_func
13592 @item (char []) $trace_func
13593 The name of the function containing @code{$tracepoint}.
13596 Note: @code{$trace_file} is not suitable for use in @code{printf},
13597 use @code{output} instead.
13599 Here's a simple example of using these convenience variables for
13600 stepping through all the trace snapshots and printing some of their
13601 data. Note that these are not the same as trace state variables,
13602 which are managed by the target.
13605 (@value{GDBP}) @b{tfind start}
13607 (@value{GDBP}) @b{while $trace_frame != -1}
13608 > output $trace_file
13609 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13615 @section Using Trace Files
13616 @cindex trace files
13618 In some situations, the target running a trace experiment may no
13619 longer be available; perhaps it crashed, or the hardware was needed
13620 for a different activity. To handle these cases, you can arrange to
13621 dump the trace data into a file, and later use that file as a source
13622 of trace data, via the @code{target tfile} command.
13627 @item tsave [ -r ] @var{filename}
13628 @itemx tsave [-ctf] @var{dirname}
13629 Save the trace data to @var{filename}. By default, this command
13630 assumes that @var{filename} refers to the host filesystem, so if
13631 necessary @value{GDBN} will copy raw trace data up from the target and
13632 then save it. If the target supports it, you can also supply the
13633 optional argument @code{-r} (``remote'') to direct the target to save
13634 the data directly into @var{filename} in its own filesystem, which may be
13635 more efficient if the trace buffer is very large. (Note, however, that
13636 @code{target tfile} can only read from files accessible to the host.)
13637 By default, this command will save trace frame in tfile format.
13638 You can supply the optional argument @code{-ctf} to save date in CTF
13639 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13640 that can be shared by multiple debugging and tracing tools. Please go to
13641 @indicateurl{http://www.efficios.com/ctf} to get more information.
13643 @kindex target tfile
13647 @item target tfile @var{filename}
13648 @itemx target ctf @var{dirname}
13649 Use the file named @var{filename} or directory named @var{dirname} as
13650 a source of trace data. Commands that examine data work as they do with
13651 a live target, but it is not possible to run any new trace experiments.
13652 @code{tstatus} will report the state of the trace run at the moment
13653 the data was saved, as well as the current trace frame you are examining.
13654 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13658 (@value{GDBP}) target ctf ctf.ctf
13659 (@value{GDBP}) tfind
13660 Found trace frame 0, tracepoint 2
13661 39 ++a; /* set tracepoint 1 here */
13662 (@value{GDBP}) tdump
13663 Data collected at tracepoint 2, trace frame 0:
13667 c = @{"123", "456", "789", "123", "456", "789"@}
13668 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13676 @chapter Debugging Programs That Use Overlays
13679 If your program is too large to fit completely in your target system's
13680 memory, you can sometimes use @dfn{overlays} to work around this
13681 problem. @value{GDBN} provides some support for debugging programs that
13685 * How Overlays Work:: A general explanation of overlays.
13686 * Overlay Commands:: Managing overlays in @value{GDBN}.
13687 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13688 mapped by asking the inferior.
13689 * Overlay Sample Program:: A sample program using overlays.
13692 @node How Overlays Work
13693 @section How Overlays Work
13694 @cindex mapped overlays
13695 @cindex unmapped overlays
13696 @cindex load address, overlay's
13697 @cindex mapped address
13698 @cindex overlay area
13700 Suppose you have a computer whose instruction address space is only 64
13701 kilobytes long, but which has much more memory which can be accessed by
13702 other means: special instructions, segment registers, or memory
13703 management hardware, for example. Suppose further that you want to
13704 adapt a program which is larger than 64 kilobytes to run on this system.
13706 One solution is to identify modules of your program which are relatively
13707 independent, and need not call each other directly; call these modules
13708 @dfn{overlays}. Separate the overlays from the main program, and place
13709 their machine code in the larger memory. Place your main program in
13710 instruction memory, but leave at least enough space there to hold the
13711 largest overlay as well.
13713 Now, to call a function located in an overlay, you must first copy that
13714 overlay's machine code from the large memory into the space set aside
13715 for it in the instruction memory, and then jump to its entry point
13718 @c NB: In the below the mapped area's size is greater or equal to the
13719 @c size of all overlays. This is intentional to remind the developer
13720 @c that overlays don't necessarily need to be the same size.
13724 Data Instruction Larger
13725 Address Space Address Space Address Space
13726 +-----------+ +-----------+ +-----------+
13728 +-----------+ +-----------+ +-----------+<-- overlay 1
13729 | program | | main | .----| overlay 1 | load address
13730 | variables | | program | | +-----------+
13731 | and heap | | | | | |
13732 +-----------+ | | | +-----------+<-- overlay 2
13733 | | +-----------+ | | | load address
13734 +-----------+ | | | .-| overlay 2 |
13736 mapped --->+-----------+ | | +-----------+
13737 address | | | | | |
13738 | overlay | <-' | | |
13739 | area | <---' +-----------+<-- overlay 3
13740 | | <---. | | load address
13741 +-----------+ `--| overlay 3 |
13748 @anchor{A code overlay}A code overlay
13752 The diagram (@pxref{A code overlay}) shows a system with separate data
13753 and instruction address spaces. To map an overlay, the program copies
13754 its code from the larger address space to the instruction address space.
13755 Since the overlays shown here all use the same mapped address, only one
13756 may be mapped at a time. For a system with a single address space for
13757 data and instructions, the diagram would be similar, except that the
13758 program variables and heap would share an address space with the main
13759 program and the overlay area.
13761 An overlay loaded into instruction memory and ready for use is called a
13762 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13763 instruction memory. An overlay not present (or only partially present)
13764 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13765 is its address in the larger memory. The mapped address is also called
13766 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13767 called the @dfn{load memory address}, or @dfn{LMA}.
13769 Unfortunately, overlays are not a completely transparent way to adapt a
13770 program to limited instruction memory. They introduce a new set of
13771 global constraints you must keep in mind as you design your program:
13776 Before calling or returning to a function in an overlay, your program
13777 must make sure that overlay is actually mapped. Otherwise, the call or
13778 return will transfer control to the right address, but in the wrong
13779 overlay, and your program will probably crash.
13782 If the process of mapping an overlay is expensive on your system, you
13783 will need to choose your overlays carefully to minimize their effect on
13784 your program's performance.
13787 The executable file you load onto your system must contain each
13788 overlay's instructions, appearing at the overlay's load address, not its
13789 mapped address. However, each overlay's instructions must be relocated
13790 and its symbols defined as if the overlay were at its mapped address.
13791 You can use GNU linker scripts to specify different load and relocation
13792 addresses for pieces of your program; see @ref{Overlay Description,,,
13793 ld.info, Using ld: the GNU linker}.
13796 The procedure for loading executable files onto your system must be able
13797 to load their contents into the larger address space as well as the
13798 instruction and data spaces.
13802 The overlay system described above is rather simple, and could be
13803 improved in many ways:
13808 If your system has suitable bank switch registers or memory management
13809 hardware, you could use those facilities to make an overlay's load area
13810 contents simply appear at their mapped address in instruction space.
13811 This would probably be faster than copying the overlay to its mapped
13812 area in the usual way.
13815 If your overlays are small enough, you could set aside more than one
13816 overlay area, and have more than one overlay mapped at a time.
13819 You can use overlays to manage data, as well as instructions. In
13820 general, data overlays are even less transparent to your design than
13821 code overlays: whereas code overlays only require care when you call or
13822 return to functions, data overlays require care every time you access
13823 the data. Also, if you change the contents of a data overlay, you
13824 must copy its contents back out to its load address before you can copy a
13825 different data overlay into the same mapped area.
13830 @node Overlay Commands
13831 @section Overlay Commands
13833 To use @value{GDBN}'s overlay support, each overlay in your program must
13834 correspond to a separate section of the executable file. The section's
13835 virtual memory address and load memory address must be the overlay's
13836 mapped and load addresses. Identifying overlays with sections allows
13837 @value{GDBN} to determine the appropriate address of a function or
13838 variable, depending on whether the overlay is mapped or not.
13840 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13841 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13846 Disable @value{GDBN}'s overlay support. When overlay support is
13847 disabled, @value{GDBN} assumes that all functions and variables are
13848 always present at their mapped addresses. By default, @value{GDBN}'s
13849 overlay support is disabled.
13851 @item overlay manual
13852 @cindex manual overlay debugging
13853 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13854 relies on you to tell it which overlays are mapped, and which are not,
13855 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13856 commands described below.
13858 @item overlay map-overlay @var{overlay}
13859 @itemx overlay map @var{overlay}
13860 @cindex map an overlay
13861 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13862 be the name of the object file section containing the overlay. When an
13863 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13864 functions and variables at their mapped addresses. @value{GDBN} assumes
13865 that any other overlays whose mapped ranges overlap that of
13866 @var{overlay} are now unmapped.
13868 @item overlay unmap-overlay @var{overlay}
13869 @itemx overlay unmap @var{overlay}
13870 @cindex unmap an overlay
13871 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13872 must be the name of the object file section containing the overlay.
13873 When an overlay is unmapped, @value{GDBN} assumes it can find the
13874 overlay's functions and variables at their load addresses.
13877 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13878 consults a data structure the overlay manager maintains in the inferior
13879 to see which overlays are mapped. For details, see @ref{Automatic
13880 Overlay Debugging}.
13882 @item overlay load-target
13883 @itemx overlay load
13884 @cindex reloading the overlay table
13885 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13886 re-reads the table @value{GDBN} automatically each time the inferior
13887 stops, so this command should only be necessary if you have changed the
13888 overlay mapping yourself using @value{GDBN}. This command is only
13889 useful when using automatic overlay debugging.
13891 @item overlay list-overlays
13892 @itemx overlay list
13893 @cindex listing mapped overlays
13894 Display a list of the overlays currently mapped, along with their mapped
13895 addresses, load addresses, and sizes.
13899 Normally, when @value{GDBN} prints a code address, it includes the name
13900 of the function the address falls in:
13903 (@value{GDBP}) print main
13904 $3 = @{int ()@} 0x11a0 <main>
13907 When overlay debugging is enabled, @value{GDBN} recognizes code in
13908 unmapped overlays, and prints the names of unmapped functions with
13909 asterisks around them. For example, if @code{foo} is a function in an
13910 unmapped overlay, @value{GDBN} prints it this way:
13913 (@value{GDBP}) overlay list
13914 No sections are mapped.
13915 (@value{GDBP}) print foo
13916 $5 = @{int (int)@} 0x100000 <*foo*>
13919 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13923 (@value{GDBP}) overlay list
13924 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13925 mapped at 0x1016 - 0x104a
13926 (@value{GDBP}) print foo
13927 $6 = @{int (int)@} 0x1016 <foo>
13930 When overlay debugging is enabled, @value{GDBN} can find the correct
13931 address for functions and variables in an overlay, whether or not the
13932 overlay is mapped. This allows most @value{GDBN} commands, like
13933 @code{break} and @code{disassemble}, to work normally, even on unmapped
13934 code. However, @value{GDBN}'s breakpoint support has some limitations:
13938 @cindex breakpoints in overlays
13939 @cindex overlays, setting breakpoints in
13940 You can set breakpoints in functions in unmapped overlays, as long as
13941 @value{GDBN} can write to the overlay at its load address.
13943 @value{GDBN} can not set hardware or simulator-based breakpoints in
13944 unmapped overlays. However, if you set a breakpoint at the end of your
13945 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13946 you are using manual overlay management), @value{GDBN} will re-set its
13947 breakpoints properly.
13951 @node Automatic Overlay Debugging
13952 @section Automatic Overlay Debugging
13953 @cindex automatic overlay debugging
13955 @value{GDBN} can automatically track which overlays are mapped and which
13956 are not, given some simple co-operation from the overlay manager in the
13957 inferior. If you enable automatic overlay debugging with the
13958 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13959 looks in the inferior's memory for certain variables describing the
13960 current state of the overlays.
13962 Here are the variables your overlay manager must define to support
13963 @value{GDBN}'s automatic overlay debugging:
13967 @item @code{_ovly_table}:
13968 This variable must be an array of the following structures:
13973 /* The overlay's mapped address. */
13976 /* The size of the overlay, in bytes. */
13977 unsigned long size;
13979 /* The overlay's load address. */
13982 /* Non-zero if the overlay is currently mapped;
13984 unsigned long mapped;
13988 @item @code{_novlys}:
13989 This variable must be a four-byte signed integer, holding the total
13990 number of elements in @code{_ovly_table}.
13994 To decide whether a particular overlay is mapped or not, @value{GDBN}
13995 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13996 @code{lma} members equal the VMA and LMA of the overlay's section in the
13997 executable file. When @value{GDBN} finds a matching entry, it consults
13998 the entry's @code{mapped} member to determine whether the overlay is
14001 In addition, your overlay manager may define a function called
14002 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14003 will silently set a breakpoint there. If the overlay manager then
14004 calls this function whenever it has changed the overlay table, this
14005 will enable @value{GDBN} to accurately keep track of which overlays
14006 are in program memory, and update any breakpoints that may be set
14007 in overlays. This will allow breakpoints to work even if the
14008 overlays are kept in ROM or other non-writable memory while they
14009 are not being executed.
14011 @node Overlay Sample Program
14012 @section Overlay Sample Program
14013 @cindex overlay example program
14015 When linking a program which uses overlays, you must place the overlays
14016 at their load addresses, while relocating them to run at their mapped
14017 addresses. To do this, you must write a linker script (@pxref{Overlay
14018 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14019 since linker scripts are specific to a particular host system, target
14020 architecture, and target memory layout, this manual cannot provide
14021 portable sample code demonstrating @value{GDBN}'s overlay support.
14023 However, the @value{GDBN} source distribution does contain an overlaid
14024 program, with linker scripts for a few systems, as part of its test
14025 suite. The program consists of the following files from
14026 @file{gdb/testsuite/gdb.base}:
14030 The main program file.
14032 A simple overlay manager, used by @file{overlays.c}.
14037 Overlay modules, loaded and used by @file{overlays.c}.
14040 Linker scripts for linking the test program on the @code{d10v-elf}
14041 and @code{m32r-elf} targets.
14044 You can build the test program using the @code{d10v-elf} GCC
14045 cross-compiler like this:
14048 $ d10v-elf-gcc -g -c overlays.c
14049 $ d10v-elf-gcc -g -c ovlymgr.c
14050 $ d10v-elf-gcc -g -c foo.c
14051 $ d10v-elf-gcc -g -c bar.c
14052 $ d10v-elf-gcc -g -c baz.c
14053 $ d10v-elf-gcc -g -c grbx.c
14054 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14055 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14058 The build process is identical for any other architecture, except that
14059 you must substitute the appropriate compiler and linker script for the
14060 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14064 @chapter Using @value{GDBN} with Different Languages
14067 Although programming languages generally have common aspects, they are
14068 rarely expressed in the same manner. For instance, in ANSI C,
14069 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14070 Modula-2, it is accomplished by @code{p^}. Values can also be
14071 represented (and displayed) differently. Hex numbers in C appear as
14072 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14074 @cindex working language
14075 Language-specific information is built into @value{GDBN} for some languages,
14076 allowing you to express operations like the above in your program's
14077 native language, and allowing @value{GDBN} to output values in a manner
14078 consistent with the syntax of your program's native language. The
14079 language you use to build expressions is called the @dfn{working
14083 * Setting:: Switching between source languages
14084 * Show:: Displaying the language
14085 * Checks:: Type and range checks
14086 * Supported Languages:: Supported languages
14087 * Unsupported Languages:: Unsupported languages
14091 @section Switching Between Source Languages
14093 There are two ways to control the working language---either have @value{GDBN}
14094 set it automatically, or select it manually yourself. You can use the
14095 @code{set language} command for either purpose. On startup, @value{GDBN}
14096 defaults to setting the language automatically. The working language is
14097 used to determine how expressions you type are interpreted, how values
14100 In addition to the working language, every source file that
14101 @value{GDBN} knows about has its own working language. For some object
14102 file formats, the compiler might indicate which language a particular
14103 source file is in. However, most of the time @value{GDBN} infers the
14104 language from the name of the file. The language of a source file
14105 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14106 show each frame appropriately for its own language. There is no way to
14107 set the language of a source file from within @value{GDBN}, but you can
14108 set the language associated with a filename extension. @xref{Show, ,
14109 Displaying the Language}.
14111 This is most commonly a problem when you use a program, such
14112 as @code{cfront} or @code{f2c}, that generates C but is written in
14113 another language. In that case, make the
14114 program use @code{#line} directives in its C output; that way
14115 @value{GDBN} will know the correct language of the source code of the original
14116 program, and will display that source code, not the generated C code.
14119 * Filenames:: Filename extensions and languages.
14120 * Manually:: Setting the working language manually
14121 * Automatically:: Having @value{GDBN} infer the source language
14125 @subsection List of Filename Extensions and Languages
14127 If a source file name ends in one of the following extensions, then
14128 @value{GDBN} infers that its language is the one indicated.
14146 C@t{++} source file
14152 Objective-C source file
14156 Fortran source file
14159 Modula-2 source file
14163 Assembler source file. This actually behaves almost like C, but
14164 @value{GDBN} does not skip over function prologues when stepping.
14167 In addition, you may set the language associated with a filename
14168 extension. @xref{Show, , Displaying the Language}.
14171 @subsection Setting the Working Language
14173 If you allow @value{GDBN} to set the language automatically,
14174 expressions are interpreted the same way in your debugging session and
14177 @kindex set language
14178 If you wish, you may set the language manually. To do this, issue the
14179 command @samp{set language @var{lang}}, where @var{lang} is the name of
14180 a language, such as
14181 @code{c} or @code{modula-2}.
14182 For a list of the supported languages, type @samp{set language}.
14184 Setting the language manually prevents @value{GDBN} from updating the working
14185 language automatically. This can lead to confusion if you try
14186 to debug a program when the working language is not the same as the
14187 source language, when an expression is acceptable to both
14188 languages---but means different things. For instance, if the current
14189 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14197 might not have the effect you intended. In C, this means to add
14198 @code{b} and @code{c} and place the result in @code{a}. The result
14199 printed would be the value of @code{a}. In Modula-2, this means to compare
14200 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14202 @node Automatically
14203 @subsection Having @value{GDBN} Infer the Source Language
14205 To have @value{GDBN} set the working language automatically, use
14206 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14207 then infers the working language. That is, when your program stops in a
14208 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14209 working language to the language recorded for the function in that
14210 frame. If the language for a frame is unknown (that is, if the function
14211 or block corresponding to the frame was defined in a source file that
14212 does not have a recognized extension), the current working language is
14213 not changed, and @value{GDBN} issues a warning.
14215 This may not seem necessary for most programs, which are written
14216 entirely in one source language. However, program modules and libraries
14217 written in one source language can be used by a main program written in
14218 a different source language. Using @samp{set language auto} in this
14219 case frees you from having to set the working language manually.
14222 @section Displaying the Language
14224 The following commands help you find out which language is the
14225 working language, and also what language source files were written in.
14228 @item show language
14229 @anchor{show language}
14230 @kindex show language
14231 Display the current working language. This is the
14232 language you can use with commands such as @code{print} to
14233 build and compute expressions that may involve variables in your program.
14236 @kindex info frame@r{, show the source language}
14237 Display the source language for this frame. This language becomes the
14238 working language if you use an identifier from this frame.
14239 @xref{Frame Info, ,Information about a Frame}, to identify the other
14240 information listed here.
14243 @kindex info source@r{, show the source language}
14244 Display the source language of this source file.
14245 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14246 information listed here.
14249 In unusual circumstances, you may have source files with extensions
14250 not in the standard list. You can then set the extension associated
14251 with a language explicitly:
14254 @item set extension-language @var{ext} @var{language}
14255 @kindex set extension-language
14256 Tell @value{GDBN} that source files with extension @var{ext} are to be
14257 assumed as written in the source language @var{language}.
14259 @item info extensions
14260 @kindex info extensions
14261 List all the filename extensions and the associated languages.
14265 @section Type and Range Checking
14267 Some languages are designed to guard you against making seemingly common
14268 errors through a series of compile- and run-time checks. These include
14269 checking the type of arguments to functions and operators and making
14270 sure mathematical overflows are caught at run time. Checks such as
14271 these help to ensure a program's correctness once it has been compiled
14272 by eliminating type mismatches and providing active checks for range
14273 errors when your program is running.
14275 By default @value{GDBN} checks for these errors according to the
14276 rules of the current source language. Although @value{GDBN} does not check
14277 the statements in your program, it can check expressions entered directly
14278 into @value{GDBN} for evaluation via the @code{print} command, for example.
14281 * Type Checking:: An overview of type checking
14282 * Range Checking:: An overview of range checking
14285 @cindex type checking
14286 @cindex checks, type
14287 @node Type Checking
14288 @subsection An Overview of Type Checking
14290 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14291 arguments to operators and functions have to be of the correct type,
14292 otherwise an error occurs. These checks prevent type mismatch
14293 errors from ever causing any run-time problems. For example,
14296 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14298 (@value{GDBP}) print obj.my_method (0)
14301 (@value{GDBP}) print obj.my_method (0x1234)
14302 Cannot resolve method klass::my_method to any overloaded instance
14305 The second example fails because in C@t{++} the integer constant
14306 @samp{0x1234} is not type-compatible with the pointer parameter type.
14308 For the expressions you use in @value{GDBN} commands, you can tell
14309 @value{GDBN} to not enforce strict type checking or
14310 to treat any mismatches as errors and abandon the expression;
14311 When type checking is disabled, @value{GDBN} successfully evaluates
14312 expressions like the second example above.
14314 Even if type checking is off, there may be other reasons
14315 related to type that prevent @value{GDBN} from evaluating an expression.
14316 For instance, @value{GDBN} does not know how to add an @code{int} and
14317 a @code{struct foo}. These particular type errors have nothing to do
14318 with the language in use and usually arise from expressions which make
14319 little sense to evaluate anyway.
14321 @value{GDBN} provides some additional commands for controlling type checking:
14323 @kindex set check type
14324 @kindex show check type
14326 @item set check type on
14327 @itemx set check type off
14328 Set strict type checking on or off. If any type mismatches occur in
14329 evaluating an expression while type checking is on, @value{GDBN} prints a
14330 message and aborts evaluation of the expression.
14332 @item show check type
14333 Show the current setting of type checking and whether @value{GDBN}
14334 is enforcing strict type checking rules.
14337 @cindex range checking
14338 @cindex checks, range
14339 @node Range Checking
14340 @subsection An Overview of Range Checking
14342 In some languages (such as Modula-2), it is an error to exceed the
14343 bounds of a type; this is enforced with run-time checks. Such range
14344 checking is meant to ensure program correctness by making sure
14345 computations do not overflow, or indices on an array element access do
14346 not exceed the bounds of the array.
14348 For expressions you use in @value{GDBN} commands, you can tell
14349 @value{GDBN} to treat range errors in one of three ways: ignore them,
14350 always treat them as errors and abandon the expression, or issue
14351 warnings but evaluate the expression anyway.
14353 A range error can result from numerical overflow, from exceeding an
14354 array index bound, or when you type a constant that is not a member
14355 of any type. Some languages, however, do not treat overflows as an
14356 error. In many implementations of C, mathematical overflow causes the
14357 result to ``wrap around'' to lower values---for example, if @var{m} is
14358 the largest integer value, and @var{s} is the smallest, then
14361 @var{m} + 1 @result{} @var{s}
14364 This, too, is specific to individual languages, and in some cases
14365 specific to individual compilers or machines. @xref{Supported Languages, ,
14366 Supported Languages}, for further details on specific languages.
14368 @value{GDBN} provides some additional commands for controlling the range checker:
14370 @kindex set check range
14371 @kindex show check range
14373 @item set check range auto
14374 Set range checking on or off based on the current working language.
14375 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14378 @item set check range on
14379 @itemx set check range off
14380 Set range checking on or off, overriding the default setting for the
14381 current working language. A warning is issued if the setting does not
14382 match the language default. If a range error occurs and range checking is on,
14383 then a message is printed and evaluation of the expression is aborted.
14385 @item set check range warn
14386 Output messages when the @value{GDBN} range checker detects a range error,
14387 but attempt to evaluate the expression anyway. Evaluating the
14388 expression may still be impossible for other reasons, such as accessing
14389 memory that the process does not own (a typical example from many Unix
14393 Show the current setting of the range checker, and whether or not it is
14394 being set automatically by @value{GDBN}.
14397 @node Supported Languages
14398 @section Supported Languages
14400 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14401 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14402 @c This is false ...
14403 Some @value{GDBN} features may be used in expressions regardless of the
14404 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14405 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14406 ,Expressions}) can be used with the constructs of any supported
14409 The following sections detail to what degree each source language is
14410 supported by @value{GDBN}. These sections are not meant to be language
14411 tutorials or references, but serve only as a reference guide to what the
14412 @value{GDBN} expression parser accepts, and what input and output
14413 formats should look like for different languages. There are many good
14414 books written on each of these languages; please look to these for a
14415 language reference or tutorial.
14418 * C:: C and C@t{++}
14421 * Objective-C:: Objective-C
14422 * OpenCL C:: OpenCL C
14423 * Fortran:: Fortran
14425 * Modula-2:: Modula-2
14430 @subsection C and C@t{++}
14432 @cindex C and C@t{++}
14433 @cindex expressions in C or C@t{++}
14435 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14436 to both languages. Whenever this is the case, we discuss those languages
14440 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14441 @cindex @sc{gnu} C@t{++}
14442 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14443 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14444 effectively, you must compile your C@t{++} programs with a supported
14445 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14446 compiler (@code{aCC}).
14449 * C Operators:: C and C@t{++} operators
14450 * C Constants:: C and C@t{++} constants
14451 * C Plus Plus Expressions:: C@t{++} expressions
14452 * C Defaults:: Default settings for C and C@t{++}
14453 * C Checks:: C and C@t{++} type and range checks
14454 * Debugging C:: @value{GDBN} and C
14455 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14456 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14460 @subsubsection C and C@t{++} Operators
14462 @cindex C and C@t{++} operators
14464 Operators must be defined on values of specific types. For instance,
14465 @code{+} is defined on numbers, but not on structures. Operators are
14466 often defined on groups of types.
14468 For the purposes of C and C@t{++}, the following definitions hold:
14473 @emph{Integral types} include @code{int} with any of its storage-class
14474 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14477 @emph{Floating-point types} include @code{float}, @code{double}, and
14478 @code{long double} (if supported by the target platform).
14481 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14484 @emph{Scalar types} include all of the above.
14489 The following operators are supported. They are listed here
14490 in order of increasing precedence:
14494 The comma or sequencing operator. Expressions in a comma-separated list
14495 are evaluated from left to right, with the result of the entire
14496 expression being the last expression evaluated.
14499 Assignment. The value of an assignment expression is the value
14500 assigned. Defined on scalar types.
14503 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14504 and translated to @w{@code{@var{a} = @var{a op b}}}.
14505 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14506 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14507 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14510 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14511 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14512 should be of an integral type.
14515 Logical @sc{or}. Defined on integral types.
14518 Logical @sc{and}. Defined on integral types.
14521 Bitwise @sc{or}. Defined on integral types.
14524 Bitwise exclusive-@sc{or}. Defined on integral types.
14527 Bitwise @sc{and}. Defined on integral types.
14530 Equality and inequality. Defined on scalar types. The value of these
14531 expressions is 0 for false and non-zero for true.
14533 @item <@r{, }>@r{, }<=@r{, }>=
14534 Less than, greater than, less than or equal, greater than or equal.
14535 Defined on scalar types. The value of these expressions is 0 for false
14536 and non-zero for true.
14539 left shift, and right shift. Defined on integral types.
14542 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14545 Addition and subtraction. Defined on integral types, floating-point types and
14548 @item *@r{, }/@r{, }%
14549 Multiplication, division, and modulus. Multiplication and division are
14550 defined on integral and floating-point types. Modulus is defined on
14554 Increment and decrement. When appearing before a variable, the
14555 operation is performed before the variable is used in an expression;
14556 when appearing after it, the variable's value is used before the
14557 operation takes place.
14560 Pointer dereferencing. Defined on pointer types. Same precedence as
14564 Address operator. Defined on variables. Same precedence as @code{++}.
14566 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14567 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14568 to examine the address
14569 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14573 Negative. Defined on integral and floating-point types. Same
14574 precedence as @code{++}.
14577 Logical negation. Defined on integral types. Same precedence as
14581 Bitwise complement operator. Defined on integral types. Same precedence as
14586 Structure member, and pointer-to-structure member. For convenience,
14587 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14588 pointer based on the stored type information.
14589 Defined on @code{struct} and @code{union} data.
14592 Dereferences of pointers to members.
14595 Array indexing. @code{@var{a}[@var{i}]} is defined as
14596 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14599 Function parameter list. Same precedence as @code{->}.
14602 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14603 and @code{class} types.
14606 Doubled colons also represent the @value{GDBN} scope operator
14607 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14611 If an operator is redefined in the user code, @value{GDBN} usually
14612 attempts to invoke the redefined version instead of using the operator's
14613 predefined meaning.
14616 @subsubsection C and C@t{++} Constants
14618 @cindex C and C@t{++} constants
14620 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14625 Integer constants are a sequence of digits. Octal constants are
14626 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14627 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14628 @samp{l}, specifying that the constant should be treated as a
14632 Floating point constants are a sequence of digits, followed by a decimal
14633 point, followed by a sequence of digits, and optionally followed by an
14634 exponent. An exponent is of the form:
14635 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14636 sequence of digits. The @samp{+} is optional for positive exponents.
14637 A floating-point constant may also end with a letter @samp{f} or
14638 @samp{F}, specifying that the constant should be treated as being of
14639 the @code{float} (as opposed to the default @code{double}) type; or with
14640 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14644 Enumerated constants consist of enumerated identifiers, or their
14645 integral equivalents.
14648 Character constants are a single character surrounded by single quotes
14649 (@code{'}), or a number---the ordinal value of the corresponding character
14650 (usually its @sc{ascii} value). Within quotes, the single character may
14651 be represented by a letter or by @dfn{escape sequences}, which are of
14652 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14653 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14654 @samp{@var{x}} is a predefined special character---for example,
14655 @samp{\n} for newline.
14657 Wide character constants can be written by prefixing a character
14658 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14659 form of @samp{x}. The target wide character set is used when
14660 computing the value of this constant (@pxref{Character Sets}).
14663 String constants are a sequence of character constants surrounded by
14664 double quotes (@code{"}). Any valid character constant (as described
14665 above) may appear. Double quotes within the string must be preceded by
14666 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14669 Wide string constants can be written by prefixing a string constant
14670 with @samp{L}, as in C. The target wide character set is used when
14671 computing the value of this constant (@pxref{Character Sets}).
14674 Pointer constants are an integral value. You can also write pointers
14675 to constants using the C operator @samp{&}.
14678 Array constants are comma-separated lists surrounded by braces @samp{@{}
14679 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14680 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14681 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14684 @node C Plus Plus Expressions
14685 @subsubsection C@t{++} Expressions
14687 @cindex expressions in C@t{++}
14688 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14690 @cindex debugging C@t{++} programs
14691 @cindex C@t{++} compilers
14692 @cindex debug formats and C@t{++}
14693 @cindex @value{NGCC} and C@t{++}
14695 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14696 the proper compiler and the proper debug format. Currently,
14697 @value{GDBN} works best when debugging C@t{++} code that is compiled
14698 with the most recent version of @value{NGCC} possible. The DWARF
14699 debugging format is preferred; @value{NGCC} defaults to this on most
14700 popular platforms. Other compilers and/or debug formats are likely to
14701 work badly or not at all when using @value{GDBN} to debug C@t{++}
14702 code. @xref{Compilation}.
14707 @cindex member functions
14709 Member function calls are allowed; you can use expressions like
14712 count = aml->GetOriginal(x, y)
14715 @vindex this@r{, inside C@t{++} member functions}
14716 @cindex namespace in C@t{++}
14718 While a member function is active (in the selected stack frame), your
14719 expressions have the same namespace available as the member function;
14720 that is, @value{GDBN} allows implicit references to the class instance
14721 pointer @code{this} following the same rules as C@t{++}. @code{using}
14722 declarations in the current scope are also respected by @value{GDBN}.
14724 @cindex call overloaded functions
14725 @cindex overloaded functions, calling
14726 @cindex type conversions in C@t{++}
14728 You can call overloaded functions; @value{GDBN} resolves the function
14729 call to the right definition, with some restrictions. @value{GDBN} does not
14730 perform overload resolution involving user-defined type conversions,
14731 calls to constructors, or instantiations of templates that do not exist
14732 in the program. It also cannot handle ellipsis argument lists or
14735 It does perform integral conversions and promotions, floating-point
14736 promotions, arithmetic conversions, pointer conversions, conversions of
14737 class objects to base classes, and standard conversions such as those of
14738 functions or arrays to pointers; it requires an exact match on the
14739 number of function arguments.
14741 Overload resolution is always performed, unless you have specified
14742 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14743 ,@value{GDBN} Features for C@t{++}}.
14745 You must specify @code{set overload-resolution off} in order to use an
14746 explicit function signature to call an overloaded function, as in
14748 p 'foo(char,int)'('x', 13)
14751 The @value{GDBN} command-completion facility can simplify this;
14752 see @ref{Completion, ,Command Completion}.
14754 @cindex reference declarations
14756 @value{GDBN} understands variables declared as C@t{++} references; you can use
14757 them in expressions just as you do in C@t{++} source---they are automatically
14760 In the parameter list shown when @value{GDBN} displays a frame, the values of
14761 reference variables are not displayed (unlike other variables); this
14762 avoids clutter, since references are often used for large structures.
14763 The @emph{address} of a reference variable is always shown, unless
14764 you have specified @samp{set print address off}.
14767 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14768 expressions can use it just as expressions in your program do. Since
14769 one scope may be defined in another, you can use @code{::} repeatedly if
14770 necessary, for example in an expression like
14771 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14772 resolving name scope by reference to source files, in both C and C@t{++}
14773 debugging (@pxref{Variables, ,Program Variables}).
14776 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14781 @subsubsection C and C@t{++} Defaults
14783 @cindex C and C@t{++} defaults
14785 If you allow @value{GDBN} to set range checking automatically, it
14786 defaults to @code{off} whenever the working language changes to
14787 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14788 selects the working language.
14790 If you allow @value{GDBN} to set the language automatically, it
14791 recognizes source files whose names end with @file{.c}, @file{.C}, or
14792 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14793 these files, it sets the working language to C or C@t{++}.
14794 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14795 for further details.
14798 @subsubsection C and C@t{++} Type and Range Checks
14800 @cindex C and C@t{++} checks
14802 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14803 checking is used. However, if you turn type checking off, @value{GDBN}
14804 will allow certain non-standard conversions, such as promoting integer
14805 constants to pointers.
14807 Range checking, if turned on, is done on mathematical operations. Array
14808 indices are not checked, since they are often used to index a pointer
14809 that is not itself an array.
14812 @subsubsection @value{GDBN} and C
14814 The @code{set print union} and @code{show print union} commands apply to
14815 the @code{union} type. When set to @samp{on}, any @code{union} that is
14816 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14817 appears as @samp{@{...@}}.
14819 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14820 with pointers and a memory allocation function. @xref{Expressions,
14823 @node Debugging C Plus Plus
14824 @subsubsection @value{GDBN} Features for C@t{++}
14826 @cindex commands for C@t{++}
14828 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14829 designed specifically for use with C@t{++}. Here is a summary:
14832 @cindex break in overloaded functions
14833 @item @r{breakpoint menus}
14834 When you want a breakpoint in a function whose name is overloaded,
14835 @value{GDBN} has the capability to display a menu of possible breakpoint
14836 locations to help you specify which function definition you want.
14837 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14839 @cindex overloading in C@t{++}
14840 @item rbreak @var{regex}
14841 Setting breakpoints using regular expressions is helpful for setting
14842 breakpoints on overloaded functions that are not members of any special
14844 @xref{Set Breaks, ,Setting Breakpoints}.
14846 @cindex C@t{++} exception handling
14848 @itemx catch rethrow
14850 Debug C@t{++} exception handling using these commands. @xref{Set
14851 Catchpoints, , Setting Catchpoints}.
14853 @cindex inheritance
14854 @item ptype @var{typename}
14855 Print inheritance relationships as well as other information for type
14857 @xref{Symbols, ,Examining the Symbol Table}.
14859 @item info vtbl @var{expression}.
14860 The @code{info vtbl} command can be used to display the virtual
14861 method tables of the object computed by @var{expression}. This shows
14862 one entry per virtual table; there may be multiple virtual tables when
14863 multiple inheritance is in use.
14865 @cindex C@t{++} demangling
14866 @item demangle @var{name}
14867 Demangle @var{name}.
14868 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14870 @cindex C@t{++} symbol display
14871 @item set print demangle
14872 @itemx show print demangle
14873 @itemx set print asm-demangle
14874 @itemx show print asm-demangle
14875 Control whether C@t{++} symbols display in their source form, both when
14876 displaying code as C@t{++} source and when displaying disassemblies.
14877 @xref{Print Settings, ,Print Settings}.
14879 @item set print object
14880 @itemx show print object
14881 Choose whether to print derived (actual) or declared types of objects.
14882 @xref{Print Settings, ,Print Settings}.
14884 @item set print vtbl
14885 @itemx show print vtbl
14886 Control the format for printing virtual function tables.
14887 @xref{Print Settings, ,Print Settings}.
14888 (The @code{vtbl} commands do not work on programs compiled with the HP
14889 ANSI C@t{++} compiler (@code{aCC}).)
14891 @kindex set overload-resolution
14892 @cindex overloaded functions, overload resolution
14893 @item set overload-resolution on
14894 Enable overload resolution for C@t{++} expression evaluation. The default
14895 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14896 and searches for a function whose signature matches the argument types,
14897 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14898 Expressions, ,C@t{++} Expressions}, for details).
14899 If it cannot find a match, it emits a message.
14901 @item set overload-resolution off
14902 Disable overload resolution for C@t{++} expression evaluation. For
14903 overloaded functions that are not class member functions, @value{GDBN}
14904 chooses the first function of the specified name that it finds in the
14905 symbol table, whether or not its arguments are of the correct type. For
14906 overloaded functions that are class member functions, @value{GDBN}
14907 searches for a function whose signature @emph{exactly} matches the
14910 @kindex show overload-resolution
14911 @item show overload-resolution
14912 Show the current setting of overload resolution.
14914 @item @r{Overloaded symbol names}
14915 You can specify a particular definition of an overloaded symbol, using
14916 the same notation that is used to declare such symbols in C@t{++}: type
14917 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14918 also use the @value{GDBN} command-line word completion facilities to list the
14919 available choices, or to finish the type list for you.
14920 @xref{Completion,, Command Completion}, for details on how to do this.
14923 @node Decimal Floating Point
14924 @subsubsection Decimal Floating Point format
14925 @cindex decimal floating point format
14927 @value{GDBN} can examine, set and perform computations with numbers in
14928 decimal floating point format, which in the C language correspond to the
14929 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14930 specified by the extension to support decimal floating-point arithmetic.
14932 There are two encodings in use, depending on the architecture: BID (Binary
14933 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14934 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14937 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14938 to manipulate decimal floating point numbers, it is not possible to convert
14939 (using a cast, for example) integers wider than 32-bit to decimal float.
14941 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14942 point computations, error checking in decimal float operations ignores
14943 underflow, overflow and divide by zero exceptions.
14945 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14946 to inspect @code{_Decimal128} values stored in floating point registers.
14947 See @ref{PowerPC,,PowerPC} for more details.
14953 @value{GDBN} can be used to debug programs written in D and compiled with
14954 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14955 specific feature --- dynamic arrays.
14960 @cindex Go (programming language)
14961 @value{GDBN} can be used to debug programs written in Go and compiled with
14962 @file{gccgo} or @file{6g} compilers.
14964 Here is a summary of the Go-specific features and restrictions:
14967 @cindex current Go package
14968 @item The current Go package
14969 The name of the current package does not need to be specified when
14970 specifying global variables and functions.
14972 For example, given the program:
14976 var myglob = "Shall we?"
14982 When stopped inside @code{main} either of these work:
14986 (gdb) p main.myglob
14989 @cindex builtin Go types
14990 @item Builtin Go types
14991 The @code{string} type is recognized by @value{GDBN} and is printed
14994 @cindex builtin Go functions
14995 @item Builtin Go functions
14996 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14997 function and handles it internally.
14999 @cindex restrictions on Go expressions
15000 @item Restrictions on Go expressions
15001 All Go operators are supported except @code{&^}.
15002 The Go @code{_} ``blank identifier'' is not supported.
15003 Automatic dereferencing of pointers is not supported.
15007 @subsection Objective-C
15009 @cindex Objective-C
15010 This section provides information about some commands and command
15011 options that are useful for debugging Objective-C code. See also
15012 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15013 few more commands specific to Objective-C support.
15016 * Method Names in Commands::
15017 * The Print Command with Objective-C::
15020 @node Method Names in Commands
15021 @subsubsection Method Names in Commands
15023 The following commands have been extended to accept Objective-C method
15024 names as line specifications:
15026 @kindex clear@r{, and Objective-C}
15027 @kindex break@r{, and Objective-C}
15028 @kindex info line@r{, and Objective-C}
15029 @kindex jump@r{, and Objective-C}
15030 @kindex list@r{, and Objective-C}
15034 @item @code{info line}
15039 A fully qualified Objective-C method name is specified as
15042 -[@var{Class} @var{methodName}]
15045 where the minus sign is used to indicate an instance method and a
15046 plus sign (not shown) is used to indicate a class method. The class
15047 name @var{Class} and method name @var{methodName} are enclosed in
15048 brackets, similar to the way messages are specified in Objective-C
15049 source code. For example, to set a breakpoint at the @code{create}
15050 instance method of class @code{Fruit} in the program currently being
15054 break -[Fruit create]
15057 To list ten program lines around the @code{initialize} class method,
15061 list +[NSText initialize]
15064 In the current version of @value{GDBN}, the plus or minus sign is
15065 required. In future versions of @value{GDBN}, the plus or minus
15066 sign will be optional, but you can use it to narrow the search. It
15067 is also possible to specify just a method name:
15073 You must specify the complete method name, including any colons. If
15074 your program's source files contain more than one @code{create} method,
15075 you'll be presented with a numbered list of classes that implement that
15076 method. Indicate your choice by number, or type @samp{0} to exit if
15079 As another example, to clear a breakpoint established at the
15080 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15083 clear -[NSWindow makeKeyAndOrderFront:]
15086 @node The Print Command with Objective-C
15087 @subsubsection The Print Command With Objective-C
15088 @cindex Objective-C, print objects
15089 @kindex print-object
15090 @kindex po @r{(@code{print-object})}
15092 The print command has also been extended to accept methods. For example:
15095 print -[@var{object} hash]
15098 @cindex print an Objective-C object description
15099 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15101 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15102 and print the result. Also, an additional command has been added,
15103 @code{print-object} or @code{po} for short, which is meant to print
15104 the description of an object. However, this command may only work
15105 with certain Objective-C libraries that have a particular hook
15106 function, @code{_NSPrintForDebugger}, defined.
15109 @subsection OpenCL C
15112 This section provides information about @value{GDBN}s OpenCL C support.
15115 * OpenCL C Datatypes::
15116 * OpenCL C Expressions::
15117 * OpenCL C Operators::
15120 @node OpenCL C Datatypes
15121 @subsubsection OpenCL C Datatypes
15123 @cindex OpenCL C Datatypes
15124 @value{GDBN} supports the builtin scalar and vector datatypes specified
15125 by OpenCL 1.1. In addition the half- and double-precision floating point
15126 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15127 extensions are also known to @value{GDBN}.
15129 @node OpenCL C Expressions
15130 @subsubsection OpenCL C Expressions
15132 @cindex OpenCL C Expressions
15133 @value{GDBN} supports accesses to vector components including the access as
15134 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15135 supported by @value{GDBN} can be used as well.
15137 @node OpenCL C Operators
15138 @subsubsection OpenCL C Operators
15140 @cindex OpenCL C Operators
15141 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15145 @subsection Fortran
15146 @cindex Fortran-specific support in @value{GDBN}
15148 @value{GDBN} can be used to debug programs written in Fortran, but it
15149 currently supports only the features of Fortran 77 language.
15151 @cindex trailing underscore, in Fortran symbols
15152 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15153 among them) append an underscore to the names of variables and
15154 functions. When you debug programs compiled by those compilers, you
15155 will need to refer to variables and functions with a trailing
15159 * Fortran Operators:: Fortran operators and expressions
15160 * Fortran Defaults:: Default settings for Fortran
15161 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15164 @node Fortran Operators
15165 @subsubsection Fortran Operators and Expressions
15167 @cindex Fortran operators and expressions
15169 Operators must be defined on values of specific types. For instance,
15170 @code{+} is defined on numbers, but not on characters or other non-
15171 arithmetic types. Operators are often defined on groups of types.
15175 The exponentiation operator. It raises the first operand to the power
15179 The range operator. Normally used in the form of array(low:high) to
15180 represent a section of array.
15183 The access component operator. Normally used to access elements in derived
15184 types. Also suitable for unions. As unions aren't part of regular Fortran,
15185 this can only happen when accessing a register that uses a gdbarch-defined
15189 @node Fortran Defaults
15190 @subsubsection Fortran Defaults
15192 @cindex Fortran Defaults
15194 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15195 default uses case-insensitive matches for Fortran symbols. You can
15196 change that with the @samp{set case-insensitive} command, see
15197 @ref{Symbols}, for the details.
15199 @node Special Fortran Commands
15200 @subsubsection Special Fortran Commands
15202 @cindex Special Fortran commands
15204 @value{GDBN} has some commands to support Fortran-specific features,
15205 such as displaying common blocks.
15208 @cindex @code{COMMON} blocks, Fortran
15209 @kindex info common
15210 @item info common @r{[}@var{common-name}@r{]}
15211 This command prints the values contained in the Fortran @code{COMMON}
15212 block whose name is @var{common-name}. With no argument, the names of
15213 all @code{COMMON} blocks visible at the current program location are
15220 @cindex Pascal support in @value{GDBN}, limitations
15221 Debugging Pascal programs which use sets, subranges, file variables, or
15222 nested functions does not currently work. @value{GDBN} does not support
15223 entering expressions, printing values, or similar features using Pascal
15226 The Pascal-specific command @code{set print pascal_static-members}
15227 controls whether static members of Pascal objects are displayed.
15228 @xref{Print Settings, pascal_static-members}.
15231 @subsection Modula-2
15233 @cindex Modula-2, @value{GDBN} support
15235 The extensions made to @value{GDBN} to support Modula-2 only support
15236 output from the @sc{gnu} Modula-2 compiler (which is currently being
15237 developed). Other Modula-2 compilers are not currently supported, and
15238 attempting to debug executables produced by them is most likely
15239 to give an error as @value{GDBN} reads in the executable's symbol
15242 @cindex expressions in Modula-2
15244 * M2 Operators:: Built-in operators
15245 * Built-In Func/Proc:: Built-in functions and procedures
15246 * M2 Constants:: Modula-2 constants
15247 * M2 Types:: Modula-2 types
15248 * M2 Defaults:: Default settings for Modula-2
15249 * Deviations:: Deviations from standard Modula-2
15250 * M2 Checks:: Modula-2 type and range checks
15251 * M2 Scope:: The scope operators @code{::} and @code{.}
15252 * GDB/M2:: @value{GDBN} and Modula-2
15256 @subsubsection Operators
15257 @cindex Modula-2 operators
15259 Operators must be defined on values of specific types. For instance,
15260 @code{+} is defined on numbers, but not on structures. Operators are
15261 often defined on groups of types. For the purposes of Modula-2, the
15262 following definitions hold:
15267 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15271 @emph{Character types} consist of @code{CHAR} and its subranges.
15274 @emph{Floating-point types} consist of @code{REAL}.
15277 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15281 @emph{Scalar types} consist of all of the above.
15284 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15287 @emph{Boolean types} consist of @code{BOOLEAN}.
15291 The following operators are supported, and appear in order of
15292 increasing precedence:
15296 Function argument or array index separator.
15299 Assignment. The value of @var{var} @code{:=} @var{value} is
15303 Less than, greater than on integral, floating-point, or enumerated
15307 Less than or equal to, greater than or equal to
15308 on integral, floating-point and enumerated types, or set inclusion on
15309 set types. Same precedence as @code{<}.
15311 @item =@r{, }<>@r{, }#
15312 Equality and two ways of expressing inequality, valid on scalar types.
15313 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15314 available for inequality, since @code{#} conflicts with the script
15318 Set membership. Defined on set types and the types of their members.
15319 Same precedence as @code{<}.
15322 Boolean disjunction. Defined on boolean types.
15325 Boolean conjunction. Defined on boolean types.
15328 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15331 Addition and subtraction on integral and floating-point types, or union
15332 and difference on set types.
15335 Multiplication on integral and floating-point types, or set intersection
15339 Division on floating-point types, or symmetric set difference on set
15340 types. Same precedence as @code{*}.
15343 Integer division and remainder. Defined on integral types. Same
15344 precedence as @code{*}.
15347 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15350 Pointer dereferencing. Defined on pointer types.
15353 Boolean negation. Defined on boolean types. Same precedence as
15357 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15358 precedence as @code{^}.
15361 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15364 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15368 @value{GDBN} and Modula-2 scope operators.
15372 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15373 treats the use of the operator @code{IN}, or the use of operators
15374 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15375 @code{<=}, and @code{>=} on sets as an error.
15379 @node Built-In Func/Proc
15380 @subsubsection Built-in Functions and Procedures
15381 @cindex Modula-2 built-ins
15383 Modula-2 also makes available several built-in procedures and functions.
15384 In describing these, the following metavariables are used:
15389 represents an @code{ARRAY} variable.
15392 represents a @code{CHAR} constant or variable.
15395 represents a variable or constant of integral type.
15398 represents an identifier that belongs to a set. Generally used in the
15399 same function with the metavariable @var{s}. The type of @var{s} should
15400 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15403 represents a variable or constant of integral or floating-point type.
15406 represents a variable or constant of floating-point type.
15412 represents a variable.
15415 represents a variable or constant of one of many types. See the
15416 explanation of the function for details.
15419 All Modula-2 built-in procedures also return a result, described below.
15423 Returns the absolute value of @var{n}.
15426 If @var{c} is a lower case letter, it returns its upper case
15427 equivalent, otherwise it returns its argument.
15430 Returns the character whose ordinal value is @var{i}.
15433 Decrements the value in the variable @var{v} by one. Returns the new value.
15435 @item DEC(@var{v},@var{i})
15436 Decrements the value in the variable @var{v} by @var{i}. Returns the
15439 @item EXCL(@var{m},@var{s})
15440 Removes the element @var{m} from the set @var{s}. Returns the new
15443 @item FLOAT(@var{i})
15444 Returns the floating point equivalent of the integer @var{i}.
15446 @item HIGH(@var{a})
15447 Returns the index of the last member of @var{a}.
15450 Increments the value in the variable @var{v} by one. Returns the new value.
15452 @item INC(@var{v},@var{i})
15453 Increments the value in the variable @var{v} by @var{i}. Returns the
15456 @item INCL(@var{m},@var{s})
15457 Adds the element @var{m} to the set @var{s} if it is not already
15458 there. Returns the new set.
15461 Returns the maximum value of the type @var{t}.
15464 Returns the minimum value of the type @var{t}.
15467 Returns boolean TRUE if @var{i} is an odd number.
15470 Returns the ordinal value of its argument. For example, the ordinal
15471 value of a character is its @sc{ascii} value (on machines supporting
15472 the @sc{ascii} character set). The argument @var{x} must be of an
15473 ordered type, which include integral, character and enumerated types.
15475 @item SIZE(@var{x})
15476 Returns the size of its argument. The argument @var{x} can be a
15477 variable or a type.
15479 @item TRUNC(@var{r})
15480 Returns the integral part of @var{r}.
15482 @item TSIZE(@var{x})
15483 Returns the size of its argument. The argument @var{x} can be a
15484 variable or a type.
15486 @item VAL(@var{t},@var{i})
15487 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15491 @emph{Warning:} Sets and their operations are not yet supported, so
15492 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15496 @cindex Modula-2 constants
15498 @subsubsection Constants
15500 @value{GDBN} allows you to express the constants of Modula-2 in the following
15506 Integer constants are simply a sequence of digits. When used in an
15507 expression, a constant is interpreted to be type-compatible with the
15508 rest of the expression. Hexadecimal integers are specified by a
15509 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15512 Floating point constants appear as a sequence of digits, followed by a
15513 decimal point and another sequence of digits. An optional exponent can
15514 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15515 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15516 digits of the floating point constant must be valid decimal (base 10)
15520 Character constants consist of a single character enclosed by a pair of
15521 like quotes, either single (@code{'}) or double (@code{"}). They may
15522 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15523 followed by a @samp{C}.
15526 String constants consist of a sequence of characters enclosed by a
15527 pair of like quotes, either single (@code{'}) or double (@code{"}).
15528 Escape sequences in the style of C are also allowed. @xref{C
15529 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15533 Enumerated constants consist of an enumerated identifier.
15536 Boolean constants consist of the identifiers @code{TRUE} and
15540 Pointer constants consist of integral values only.
15543 Set constants are not yet supported.
15547 @subsubsection Modula-2 Types
15548 @cindex Modula-2 types
15550 Currently @value{GDBN} can print the following data types in Modula-2
15551 syntax: array types, record types, set types, pointer types, procedure
15552 types, enumerated types, subrange types and base types. You can also
15553 print the contents of variables declared using these type.
15554 This section gives a number of simple source code examples together with
15555 sample @value{GDBN} sessions.
15557 The first example contains the following section of code:
15566 and you can request @value{GDBN} to interrogate the type and value of
15567 @code{r} and @code{s}.
15570 (@value{GDBP}) print s
15572 (@value{GDBP}) ptype s
15574 (@value{GDBP}) print r
15576 (@value{GDBP}) ptype r
15581 Likewise if your source code declares @code{s} as:
15585 s: SET ['A'..'Z'] ;
15589 then you may query the type of @code{s} by:
15592 (@value{GDBP}) ptype s
15593 type = SET ['A'..'Z']
15597 Note that at present you cannot interactively manipulate set
15598 expressions using the debugger.
15600 The following example shows how you might declare an array in Modula-2
15601 and how you can interact with @value{GDBN} to print its type and contents:
15605 s: ARRAY [-10..10] OF CHAR ;
15609 (@value{GDBP}) ptype s
15610 ARRAY [-10..10] OF CHAR
15613 Note that the array handling is not yet complete and although the type
15614 is printed correctly, expression handling still assumes that all
15615 arrays have a lower bound of zero and not @code{-10} as in the example
15618 Here are some more type related Modula-2 examples:
15622 colour = (blue, red, yellow, green) ;
15623 t = [blue..yellow] ;
15631 The @value{GDBN} interaction shows how you can query the data type
15632 and value of a variable.
15635 (@value{GDBP}) print s
15637 (@value{GDBP}) ptype t
15638 type = [blue..yellow]
15642 In this example a Modula-2 array is declared and its contents
15643 displayed. Observe that the contents are written in the same way as
15644 their @code{C} counterparts.
15648 s: ARRAY [1..5] OF CARDINAL ;
15654 (@value{GDBP}) print s
15655 $1 = @{1, 0, 0, 0, 0@}
15656 (@value{GDBP}) ptype s
15657 type = ARRAY [1..5] OF CARDINAL
15660 The Modula-2 language interface to @value{GDBN} also understands
15661 pointer types as shown in this example:
15665 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15672 and you can request that @value{GDBN} describes the type of @code{s}.
15675 (@value{GDBP}) ptype s
15676 type = POINTER TO ARRAY [1..5] OF CARDINAL
15679 @value{GDBN} handles compound types as we can see in this example.
15680 Here we combine array types, record types, pointer types and subrange
15691 myarray = ARRAY myrange OF CARDINAL ;
15692 myrange = [-2..2] ;
15694 s: POINTER TO ARRAY myrange OF foo ;
15698 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15702 (@value{GDBP}) ptype s
15703 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15706 f3 : ARRAY [-2..2] OF CARDINAL;
15711 @subsubsection Modula-2 Defaults
15712 @cindex Modula-2 defaults
15714 If type and range checking are set automatically by @value{GDBN}, they
15715 both default to @code{on} whenever the working language changes to
15716 Modula-2. This happens regardless of whether you or @value{GDBN}
15717 selected the working language.
15719 If you allow @value{GDBN} to set the language automatically, then entering
15720 code compiled from a file whose name ends with @file{.mod} sets the
15721 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15722 Infer the Source Language}, for further details.
15725 @subsubsection Deviations from Standard Modula-2
15726 @cindex Modula-2, deviations from
15728 A few changes have been made to make Modula-2 programs easier to debug.
15729 This is done primarily via loosening its type strictness:
15733 Unlike in standard Modula-2, pointer constants can be formed by
15734 integers. This allows you to modify pointer variables during
15735 debugging. (In standard Modula-2, the actual address contained in a
15736 pointer variable is hidden from you; it can only be modified
15737 through direct assignment to another pointer variable or expression that
15738 returned a pointer.)
15741 C escape sequences can be used in strings and characters to represent
15742 non-printable characters. @value{GDBN} prints out strings with these
15743 escape sequences embedded. Single non-printable characters are
15744 printed using the @samp{CHR(@var{nnn})} format.
15747 The assignment operator (@code{:=}) returns the value of its right-hand
15751 All built-in procedures both modify @emph{and} return their argument.
15755 @subsubsection Modula-2 Type and Range Checks
15756 @cindex Modula-2 checks
15759 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15762 @c FIXME remove warning when type/range checks added
15764 @value{GDBN} considers two Modula-2 variables type equivalent if:
15768 They are of types that have been declared equivalent via a @code{TYPE
15769 @var{t1} = @var{t2}} statement
15772 They have been declared on the same line. (Note: This is true of the
15773 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15776 As long as type checking is enabled, any attempt to combine variables
15777 whose types are not equivalent is an error.
15779 Range checking is done on all mathematical operations, assignment, array
15780 index bounds, and all built-in functions and procedures.
15783 @subsubsection The Scope Operators @code{::} and @code{.}
15785 @cindex @code{.}, Modula-2 scope operator
15786 @cindex colon, doubled as scope operator
15788 @vindex colon-colon@r{, in Modula-2}
15789 @c Info cannot handle :: but TeX can.
15792 @vindex ::@r{, in Modula-2}
15795 There are a few subtle differences between the Modula-2 scope operator
15796 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15801 @var{module} . @var{id}
15802 @var{scope} :: @var{id}
15806 where @var{scope} is the name of a module or a procedure,
15807 @var{module} the name of a module, and @var{id} is any declared
15808 identifier within your program, except another module.
15810 Using the @code{::} operator makes @value{GDBN} search the scope
15811 specified by @var{scope} for the identifier @var{id}. If it is not
15812 found in the specified scope, then @value{GDBN} searches all scopes
15813 enclosing the one specified by @var{scope}.
15815 Using the @code{.} operator makes @value{GDBN} search the current scope for
15816 the identifier specified by @var{id} that was imported from the
15817 definition module specified by @var{module}. With this operator, it is
15818 an error if the identifier @var{id} was not imported from definition
15819 module @var{module}, or if @var{id} is not an identifier in
15823 @subsubsection @value{GDBN} and Modula-2
15825 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15826 Five subcommands of @code{set print} and @code{show print} apply
15827 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15828 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15829 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15830 analogue in Modula-2.
15832 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15833 with any language, is not useful with Modula-2. Its
15834 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15835 created in Modula-2 as they can in C or C@t{++}. However, because an
15836 address can be specified by an integral constant, the construct
15837 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15839 @cindex @code{#} in Modula-2
15840 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15841 interpreted as the beginning of a comment. Use @code{<>} instead.
15847 The extensions made to @value{GDBN} for Ada only support
15848 output from the @sc{gnu} Ada (GNAT) compiler.
15849 Other Ada compilers are not currently supported, and
15850 attempting to debug executables produced by them is most likely
15854 @cindex expressions in Ada
15856 * Ada Mode Intro:: General remarks on the Ada syntax
15857 and semantics supported by Ada mode
15859 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15860 * Additions to Ada:: Extensions of the Ada expression syntax.
15861 * Overloading support for Ada:: Support for expressions involving overloaded
15863 * Stopping Before Main Program:: Debugging the program during elaboration.
15864 * Ada Exceptions:: Ada Exceptions
15865 * Ada Tasks:: Listing and setting breakpoints in tasks.
15866 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15867 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15869 * Ada Glitches:: Known peculiarities of Ada mode.
15872 @node Ada Mode Intro
15873 @subsubsection Introduction
15874 @cindex Ada mode, general
15876 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15877 syntax, with some extensions.
15878 The philosophy behind the design of this subset is
15882 That @value{GDBN} should provide basic literals and access to operations for
15883 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15884 leaving more sophisticated computations to subprograms written into the
15885 program (which therefore may be called from @value{GDBN}).
15888 That type safety and strict adherence to Ada language restrictions
15889 are not particularly important to the @value{GDBN} user.
15892 That brevity is important to the @value{GDBN} user.
15895 Thus, for brevity, the debugger acts as if all names declared in
15896 user-written packages are directly visible, even if they are not visible
15897 according to Ada rules, thus making it unnecessary to fully qualify most
15898 names with their packages, regardless of context. Where this causes
15899 ambiguity, @value{GDBN} asks the user's intent.
15901 The debugger will start in Ada mode if it detects an Ada main program.
15902 As for other languages, it will enter Ada mode when stopped in a program that
15903 was translated from an Ada source file.
15905 While in Ada mode, you may use `@t{--}' for comments. This is useful
15906 mostly for documenting command files. The standard @value{GDBN} comment
15907 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15908 middle (to allow based literals).
15910 @node Omissions from Ada
15911 @subsubsection Omissions from Ada
15912 @cindex Ada, omissions from
15914 Here are the notable omissions from the subset:
15918 Only a subset of the attributes are supported:
15922 @t{'First}, @t{'Last}, and @t{'Length}
15923 on array objects (not on types and subtypes).
15926 @t{'Min} and @t{'Max}.
15929 @t{'Pos} and @t{'Val}.
15935 @t{'Range} on array objects (not subtypes), but only as the right
15936 operand of the membership (@code{in}) operator.
15939 @t{'Access}, @t{'Unchecked_Access}, and
15940 @t{'Unrestricted_Access} (a GNAT extension).
15948 @code{Characters.Latin_1} are not available and
15949 concatenation is not implemented. Thus, escape characters in strings are
15950 not currently available.
15953 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15954 equality of representations. They will generally work correctly
15955 for strings and arrays whose elements have integer or enumeration types.
15956 They may not work correctly for arrays whose element
15957 types have user-defined equality, for arrays of real values
15958 (in particular, IEEE-conformant floating point, because of negative
15959 zeroes and NaNs), and for arrays whose elements contain unused bits with
15960 indeterminate values.
15963 The other component-by-component array operations (@code{and}, @code{or},
15964 @code{xor}, @code{not}, and relational tests other than equality)
15965 are not implemented.
15968 @cindex array aggregates (Ada)
15969 @cindex record aggregates (Ada)
15970 @cindex aggregates (Ada)
15971 There is limited support for array and record aggregates. They are
15972 permitted only on the right sides of assignments, as in these examples:
15975 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15976 (@value{GDBP}) set An_Array := (1, others => 0)
15977 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15978 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15979 (@value{GDBP}) set A_Record := (1, "Peter", True);
15980 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15984 discriminant's value by assigning an aggregate has an
15985 undefined effect if that discriminant is used within the record.
15986 However, you can first modify discriminants by directly assigning to
15987 them (which normally would not be allowed in Ada), and then performing an
15988 aggregate assignment. For example, given a variable @code{A_Rec}
15989 declared to have a type such as:
15992 type Rec (Len : Small_Integer := 0) is record
15994 Vals : IntArray (1 .. Len);
15998 you can assign a value with a different size of @code{Vals} with two
16002 (@value{GDBP}) set A_Rec.Len := 4
16003 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16006 As this example also illustrates, @value{GDBN} is very loose about the usual
16007 rules concerning aggregates. You may leave out some of the
16008 components of an array or record aggregate (such as the @code{Len}
16009 component in the assignment to @code{A_Rec} above); they will retain their
16010 original values upon assignment. You may freely use dynamic values as
16011 indices in component associations. You may even use overlapping or
16012 redundant component associations, although which component values are
16013 assigned in such cases is not defined.
16016 Calls to dispatching subprograms are not implemented.
16019 The overloading algorithm is much more limited (i.e., less selective)
16020 than that of real Ada. It makes only limited use of the context in
16021 which a subexpression appears to resolve its meaning, and it is much
16022 looser in its rules for allowing type matches. As a result, some
16023 function calls will be ambiguous, and the user will be asked to choose
16024 the proper resolution.
16027 The @code{new} operator is not implemented.
16030 Entry calls are not implemented.
16033 Aside from printing, arithmetic operations on the native VAX floating-point
16034 formats are not supported.
16037 It is not possible to slice a packed array.
16040 The names @code{True} and @code{False}, when not part of a qualified name,
16041 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16043 Should your program
16044 redefine these names in a package or procedure (at best a dubious practice),
16045 you will have to use fully qualified names to access their new definitions.
16048 @node Additions to Ada
16049 @subsubsection Additions to Ada
16050 @cindex Ada, deviations from
16052 As it does for other languages, @value{GDBN} makes certain generic
16053 extensions to Ada (@pxref{Expressions}):
16057 If the expression @var{E} is a variable residing in memory (typically
16058 a local variable or array element) and @var{N} is a positive integer,
16059 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16060 @var{N}-1 adjacent variables following it in memory as an array. In
16061 Ada, this operator is generally not necessary, since its prime use is
16062 in displaying parts of an array, and slicing will usually do this in
16063 Ada. However, there are occasional uses when debugging programs in
16064 which certain debugging information has been optimized away.
16067 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16068 appears in function or file @var{B}.'' When @var{B} is a file name,
16069 you must typically surround it in single quotes.
16072 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16073 @var{type} that appears at address @var{addr}.''
16076 A name starting with @samp{$} is a convenience variable
16077 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16080 In addition, @value{GDBN} provides a few other shortcuts and outright
16081 additions specific to Ada:
16085 The assignment statement is allowed as an expression, returning
16086 its right-hand operand as its value. Thus, you may enter
16089 (@value{GDBP}) set x := y + 3
16090 (@value{GDBP}) print A(tmp := y + 1)
16094 The semicolon is allowed as an ``operator,'' returning as its value
16095 the value of its right-hand operand.
16096 This allows, for example,
16097 complex conditional breaks:
16100 (@value{GDBP}) break f
16101 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16105 Rather than use catenation and symbolic character names to introduce special
16106 characters into strings, one may instead use a special bracket notation,
16107 which is also used to print strings. A sequence of characters of the form
16108 @samp{["@var{XX}"]} within a string or character literal denotes the
16109 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16110 sequence of characters @samp{["""]} also denotes a single quotation mark
16111 in strings. For example,
16113 "One line.["0a"]Next line.["0a"]"
16116 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16120 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16121 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16125 (@value{GDBP}) print 'max(x, y)
16129 When printing arrays, @value{GDBN} uses positional notation when the
16130 array has a lower bound of 1, and uses a modified named notation otherwise.
16131 For example, a one-dimensional array of three integers with a lower bound
16132 of 3 might print as
16139 That is, in contrast to valid Ada, only the first component has a @code{=>}
16143 You may abbreviate attributes in expressions with any unique,
16144 multi-character subsequence of
16145 their names (an exact match gets preference).
16146 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16147 in place of @t{a'length}.
16150 @cindex quoting Ada internal identifiers
16151 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16152 to lower case. The GNAT compiler uses upper-case characters for
16153 some of its internal identifiers, which are normally of no interest to users.
16154 For the rare occasions when you actually have to look at them,
16155 enclose them in angle brackets to avoid the lower-case mapping.
16158 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16162 Printing an object of class-wide type or dereferencing an
16163 access-to-class-wide value will display all the components of the object's
16164 specific type (as indicated by its run-time tag). Likewise, component
16165 selection on such a value will operate on the specific type of the
16170 @node Overloading support for Ada
16171 @subsubsection Overloading support for Ada
16172 @cindex overloading, Ada
16174 The debugger supports limited overloading. Given a subprogram call in which
16175 the function symbol has multiple definitions, it will use the number of
16176 actual parameters and some information about their types to attempt to narrow
16177 the set of definitions. It also makes very limited use of context, preferring
16178 procedures to functions in the context of the @code{call} command, and
16179 functions to procedures elsewhere.
16181 If, after narrowing, the set of matching definitions still contains more than
16182 one definition, @value{GDBN} will display a menu to query which one it should
16186 (@value{GDBP}) print f(1)
16187 Multiple matches for f
16189 [1] foo.f (integer) return boolean at foo.adb:23
16190 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16194 In this case, just select one menu entry either to cancel expression evaluation
16195 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16196 instance (type the corresponding number and press @key{RET}).
16198 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16203 @kindex set ada print-signatures
16204 @item set ada print-signatures
16205 Control whether parameter types and return types are displayed in overloads
16206 selection menus. It is @code{on} by default.
16207 @xref{Overloading support for Ada}.
16209 @kindex show ada print-signatures
16210 @item show ada print-signatures
16211 Show the current setting for displaying parameter types and return types in
16212 overloads selection menu.
16213 @xref{Overloading support for Ada}.
16217 @node Stopping Before Main Program
16218 @subsubsection Stopping at the Very Beginning
16220 @cindex breakpointing Ada elaboration code
16221 It is sometimes necessary to debug the program during elaboration, and
16222 before reaching the main procedure.
16223 As defined in the Ada Reference
16224 Manual, the elaboration code is invoked from a procedure called
16225 @code{adainit}. To run your program up to the beginning of
16226 elaboration, simply use the following two commands:
16227 @code{tbreak adainit} and @code{run}.
16229 @node Ada Exceptions
16230 @subsubsection Ada Exceptions
16232 A command is provided to list all Ada exceptions:
16235 @kindex info exceptions
16236 @item info exceptions
16237 @itemx info exceptions @var{regexp}
16238 The @code{info exceptions} command allows you to list all Ada exceptions
16239 defined within the program being debugged, as well as their addresses.
16240 With a regular expression, @var{regexp}, as argument, only those exceptions
16241 whose names match @var{regexp} are listed.
16244 Below is a small example, showing how the command can be used, first
16245 without argument, and next with a regular expression passed as an
16249 (@value{GDBP}) info exceptions
16250 All defined Ada exceptions:
16251 constraint_error: 0x613da0
16252 program_error: 0x613d20
16253 storage_error: 0x613ce0
16254 tasking_error: 0x613ca0
16255 const.aint_global_e: 0x613b00
16256 (@value{GDBP}) info exceptions const.aint
16257 All Ada exceptions matching regular expression "const.aint":
16258 constraint_error: 0x613da0
16259 const.aint_global_e: 0x613b00
16262 It is also possible to ask @value{GDBN} to stop your program's execution
16263 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16266 @subsubsection Extensions for Ada Tasks
16267 @cindex Ada, tasking
16269 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16270 @value{GDBN} provides the following task-related commands:
16275 This command shows a list of current Ada tasks, as in the following example:
16282 (@value{GDBP}) info tasks
16283 ID TID P-ID Pri State Name
16284 1 8088000 0 15 Child Activation Wait main_task
16285 2 80a4000 1 15 Accept Statement b
16286 3 809a800 1 15 Child Activation Wait a
16287 * 4 80ae800 3 15 Runnable c
16292 In this listing, the asterisk before the last task indicates it to be the
16293 task currently being inspected.
16297 Represents @value{GDBN}'s internal task number.
16303 The parent's task ID (@value{GDBN}'s internal task number).
16306 The base priority of the task.
16309 Current state of the task.
16313 The task has been created but has not been activated. It cannot be
16317 The task is not blocked for any reason known to Ada. (It may be waiting
16318 for a mutex, though.) It is conceptually "executing" in normal mode.
16321 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16322 that were waiting on terminate alternatives have been awakened and have
16323 terminated themselves.
16325 @item Child Activation Wait
16326 The task is waiting for created tasks to complete activation.
16328 @item Accept Statement
16329 The task is waiting on an accept or selective wait statement.
16331 @item Waiting on entry call
16332 The task is waiting on an entry call.
16334 @item Async Select Wait
16335 The task is waiting to start the abortable part of an asynchronous
16339 The task is waiting on a select statement with only a delay
16342 @item Child Termination Wait
16343 The task is sleeping having completed a master within itself, and is
16344 waiting for the tasks dependent on that master to become terminated or
16345 waiting on a terminate Phase.
16347 @item Wait Child in Term Alt
16348 The task is sleeping waiting for tasks on terminate alternatives to
16349 finish terminating.
16351 @item Accepting RV with @var{taskno}
16352 The task is accepting a rendez-vous with the task @var{taskno}.
16356 Name of the task in the program.
16360 @kindex info task @var{taskno}
16361 @item info task @var{taskno}
16362 This command shows detailled informations on the specified task, as in
16363 the following example:
16368 (@value{GDBP}) info tasks
16369 ID TID P-ID Pri State Name
16370 1 8077880 0 15 Child Activation Wait main_task
16371 * 2 807c468 1 15 Runnable task_1
16372 (@value{GDBP}) info task 2
16373 Ada Task: 0x807c468
16376 Parent: 1 (main_task)
16382 @kindex task@r{ (Ada)}
16383 @cindex current Ada task ID
16384 This command prints the ID of the current task.
16390 (@value{GDBP}) info tasks
16391 ID TID P-ID Pri State Name
16392 1 8077870 0 15 Child Activation Wait main_task
16393 * 2 807c458 1 15 Runnable t
16394 (@value{GDBP}) task
16395 [Current task is 2]
16398 @item task @var{taskno}
16399 @cindex Ada task switching
16400 This command is like the @code{thread @var{thread-id}}
16401 command (@pxref{Threads}). It switches the context of debugging
16402 from the current task to the given task.
16408 (@value{GDBP}) info tasks
16409 ID TID P-ID Pri State Name
16410 1 8077870 0 15 Child Activation Wait main_task
16411 * 2 807c458 1 15 Runnable t
16412 (@value{GDBP}) task 1
16413 [Switching to task 1]
16414 #0 0x8067726 in pthread_cond_wait ()
16416 #0 0x8067726 in pthread_cond_wait ()
16417 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16418 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16419 #3 0x806153e in system.tasking.stages.activate_tasks ()
16420 #4 0x804aacc in un () at un.adb:5
16423 @item break @var{location} task @var{taskno}
16424 @itemx break @var{location} task @var{taskno} if @dots{}
16425 @cindex breakpoints and tasks, in Ada
16426 @cindex task breakpoints, in Ada
16427 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16428 These commands are like the @code{break @dots{} thread @dots{}}
16429 command (@pxref{Thread Stops}). The
16430 @var{location} argument specifies source lines, as described
16431 in @ref{Specify Location}.
16433 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16434 to specify that you only want @value{GDBN} to stop the program when a
16435 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16436 numeric task identifiers assigned by @value{GDBN}, shown in the first
16437 column of the @samp{info tasks} display.
16439 If you do not specify @samp{task @var{taskno}} when you set a
16440 breakpoint, the breakpoint applies to @emph{all} tasks of your
16443 You can use the @code{task} qualifier on conditional breakpoints as
16444 well; in this case, place @samp{task @var{taskno}} before the
16445 breakpoint condition (before the @code{if}).
16453 (@value{GDBP}) info tasks
16454 ID TID P-ID Pri State Name
16455 1 140022020 0 15 Child Activation Wait main_task
16456 2 140045060 1 15 Accept/Select Wait t2
16457 3 140044840 1 15 Runnable t1
16458 * 4 140056040 1 15 Runnable t3
16459 (@value{GDBP}) b 15 task 2
16460 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16461 (@value{GDBP}) cont
16466 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16468 (@value{GDBP}) info tasks
16469 ID TID P-ID Pri State Name
16470 1 140022020 0 15 Child Activation Wait main_task
16471 * 2 140045060 1 15 Runnable t2
16472 3 140044840 1 15 Runnable t1
16473 4 140056040 1 15 Delay Sleep t3
16477 @node Ada Tasks and Core Files
16478 @subsubsection Tasking Support when Debugging Core Files
16479 @cindex Ada tasking and core file debugging
16481 When inspecting a core file, as opposed to debugging a live program,
16482 tasking support may be limited or even unavailable, depending on
16483 the platform being used.
16484 For instance, on x86-linux, the list of tasks is available, but task
16485 switching is not supported.
16487 On certain platforms, the debugger needs to perform some
16488 memory writes in order to provide Ada tasking support. When inspecting
16489 a core file, this means that the core file must be opened with read-write
16490 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16491 Under these circumstances, you should make a backup copy of the core
16492 file before inspecting it with @value{GDBN}.
16494 @node Ravenscar Profile
16495 @subsubsection Tasking Support when using the Ravenscar Profile
16496 @cindex Ravenscar Profile
16498 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16499 specifically designed for systems with safety-critical real-time
16503 @kindex set ravenscar task-switching on
16504 @cindex task switching with program using Ravenscar Profile
16505 @item set ravenscar task-switching on
16506 Allows task switching when debugging a program that uses the Ravenscar
16507 Profile. This is the default.
16509 @kindex set ravenscar task-switching off
16510 @item set ravenscar task-switching off
16511 Turn off task switching when debugging a program that uses the Ravenscar
16512 Profile. This is mostly intended to disable the code that adds support
16513 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16514 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16515 To be effective, this command should be run before the program is started.
16517 @kindex show ravenscar task-switching
16518 @item show ravenscar task-switching
16519 Show whether it is possible to switch from task to task in a program
16520 using the Ravenscar Profile.
16525 @subsubsection Known Peculiarities of Ada Mode
16526 @cindex Ada, problems
16528 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16529 we know of several problems with and limitations of Ada mode in
16531 some of which will be fixed with planned future releases of the debugger
16532 and the GNU Ada compiler.
16536 Static constants that the compiler chooses not to materialize as objects in
16537 storage are invisible to the debugger.
16540 Named parameter associations in function argument lists are ignored (the
16541 argument lists are treated as positional).
16544 Many useful library packages are currently invisible to the debugger.
16547 Fixed-point arithmetic, conversions, input, and output is carried out using
16548 floating-point arithmetic, and may give results that only approximate those on
16552 The GNAT compiler never generates the prefix @code{Standard} for any of
16553 the standard symbols defined by the Ada language. @value{GDBN} knows about
16554 this: it will strip the prefix from names when you use it, and will never
16555 look for a name you have so qualified among local symbols, nor match against
16556 symbols in other packages or subprograms. If you have
16557 defined entities anywhere in your program other than parameters and
16558 local variables whose simple names match names in @code{Standard},
16559 GNAT's lack of qualification here can cause confusion. When this happens,
16560 you can usually resolve the confusion
16561 by qualifying the problematic names with package
16562 @code{Standard} explicitly.
16565 Older versions of the compiler sometimes generate erroneous debugging
16566 information, resulting in the debugger incorrectly printing the value
16567 of affected entities. In some cases, the debugger is able to work
16568 around an issue automatically. In other cases, the debugger is able
16569 to work around the issue, but the work-around has to be specifically
16572 @kindex set ada trust-PAD-over-XVS
16573 @kindex show ada trust-PAD-over-XVS
16576 @item set ada trust-PAD-over-XVS on
16577 Configure GDB to strictly follow the GNAT encoding when computing the
16578 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16579 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16580 a complete description of the encoding used by the GNAT compiler).
16581 This is the default.
16583 @item set ada trust-PAD-over-XVS off
16584 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16585 sometimes prints the wrong value for certain entities, changing @code{ada
16586 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16587 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16588 @code{off}, but this incurs a slight performance penalty, so it is
16589 recommended to leave this setting to @code{on} unless necessary.
16593 @cindex GNAT descriptive types
16594 @cindex GNAT encoding
16595 Internally, the debugger also relies on the compiler following a number
16596 of conventions known as the @samp{GNAT Encoding}, all documented in
16597 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16598 how the debugging information should be generated for certain types.
16599 In particular, this convention makes use of @dfn{descriptive types},
16600 which are artificial types generated purely to help the debugger.
16602 These encodings were defined at a time when the debugging information
16603 format used was not powerful enough to describe some of the more complex
16604 types available in Ada. Since DWARF allows us to express nearly all
16605 Ada features, the long-term goal is to slowly replace these descriptive
16606 types by their pure DWARF equivalent. To facilitate that transition,
16607 a new maintenance option is available to force the debugger to ignore
16608 those descriptive types. It allows the user to quickly evaluate how
16609 well @value{GDBN} works without them.
16613 @kindex maint ada set ignore-descriptive-types
16614 @item maintenance ada set ignore-descriptive-types [on|off]
16615 Control whether the debugger should ignore descriptive types.
16616 The default is not to ignore descriptives types (@code{off}).
16618 @kindex maint ada show ignore-descriptive-types
16619 @item maintenance ada show ignore-descriptive-types
16620 Show if descriptive types are ignored by @value{GDBN}.
16624 @node Unsupported Languages
16625 @section Unsupported Languages
16627 @cindex unsupported languages
16628 @cindex minimal language
16629 In addition to the other fully-supported programming languages,
16630 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16631 It does not represent a real programming language, but provides a set
16632 of capabilities close to what the C or assembly languages provide.
16633 This should allow most simple operations to be performed while debugging
16634 an application that uses a language currently not supported by @value{GDBN}.
16636 If the language is set to @code{auto}, @value{GDBN} will automatically
16637 select this language if the current frame corresponds to an unsupported
16641 @chapter Examining the Symbol Table
16643 The commands described in this chapter allow you to inquire about the
16644 symbols (names of variables, functions and types) defined in your
16645 program. This information is inherent in the text of your program and
16646 does not change as your program executes. @value{GDBN} finds it in your
16647 program's symbol table, in the file indicated when you started @value{GDBN}
16648 (@pxref{File Options, ,Choosing Files}), or by one of the
16649 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16651 @cindex symbol names
16652 @cindex names of symbols
16653 @cindex quoting names
16654 Occasionally, you may need to refer to symbols that contain unusual
16655 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16656 most frequent case is in referring to static variables in other
16657 source files (@pxref{Variables,,Program Variables}). File names
16658 are recorded in object files as debugging symbols, but @value{GDBN} would
16659 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16660 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16661 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16668 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16671 @cindex case-insensitive symbol names
16672 @cindex case sensitivity in symbol names
16673 @kindex set case-sensitive
16674 @item set case-sensitive on
16675 @itemx set case-sensitive off
16676 @itemx set case-sensitive auto
16677 Normally, when @value{GDBN} looks up symbols, it matches their names
16678 with case sensitivity determined by the current source language.
16679 Occasionally, you may wish to control that. The command @code{set
16680 case-sensitive} lets you do that by specifying @code{on} for
16681 case-sensitive matches or @code{off} for case-insensitive ones. If
16682 you specify @code{auto}, case sensitivity is reset to the default
16683 suitable for the source language. The default is case-sensitive
16684 matches for all languages except for Fortran, for which the default is
16685 case-insensitive matches.
16687 @kindex show case-sensitive
16688 @item show case-sensitive
16689 This command shows the current setting of case sensitivity for symbols
16692 @kindex set print type methods
16693 @item set print type methods
16694 @itemx set print type methods on
16695 @itemx set print type methods off
16696 Normally, when @value{GDBN} prints a class, it displays any methods
16697 declared in that class. You can control this behavior either by
16698 passing the appropriate flag to @code{ptype}, or using @command{set
16699 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16700 display the methods; this is the default. Specifying @code{off} will
16701 cause @value{GDBN} to omit the methods.
16703 @kindex show print type methods
16704 @item show print type methods
16705 This command shows the current setting of method display when printing
16708 @kindex set print type typedefs
16709 @item set print type typedefs
16710 @itemx set print type typedefs on
16711 @itemx set print type typedefs off
16713 Normally, when @value{GDBN} prints a class, it displays any typedefs
16714 defined in that class. You can control this behavior either by
16715 passing the appropriate flag to @code{ptype}, or using @command{set
16716 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16717 display the typedef definitions; this is the default. Specifying
16718 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16719 Note that this controls whether the typedef definition itself is
16720 printed, not whether typedef names are substituted when printing other
16723 @kindex show print type typedefs
16724 @item show print type typedefs
16725 This command shows the current setting of typedef display when
16728 @kindex info address
16729 @cindex address of a symbol
16730 @item info address @var{symbol}
16731 Describe where the data for @var{symbol} is stored. For a register
16732 variable, this says which register it is kept in. For a non-register
16733 local variable, this prints the stack-frame offset at which the variable
16736 Note the contrast with @samp{print &@var{symbol}}, which does not work
16737 at all for a register variable, and for a stack local variable prints
16738 the exact address of the current instantiation of the variable.
16740 @kindex info symbol
16741 @cindex symbol from address
16742 @cindex closest symbol and offset for an address
16743 @item info symbol @var{addr}
16744 Print the name of a symbol which is stored at the address @var{addr}.
16745 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16746 nearest symbol and an offset from it:
16749 (@value{GDBP}) info symbol 0x54320
16750 _initialize_vx + 396 in section .text
16754 This is the opposite of the @code{info address} command. You can use
16755 it to find out the name of a variable or a function given its address.
16757 For dynamically linked executables, the name of executable or shared
16758 library containing the symbol is also printed:
16761 (@value{GDBP}) info symbol 0x400225
16762 _start + 5 in section .text of /tmp/a.out
16763 (@value{GDBP}) info symbol 0x2aaaac2811cf
16764 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16769 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16770 Demangle @var{name}.
16771 If @var{language} is provided it is the name of the language to demangle
16772 @var{name} in. Otherwise @var{name} is demangled in the current language.
16774 The @samp{--} option specifies the end of options,
16775 and is useful when @var{name} begins with a dash.
16777 The parameter @code{demangle-style} specifies how to interpret the kind
16778 of mangling used. @xref{Print Settings}.
16781 @item whatis[/@var{flags}] [@var{arg}]
16782 Print the data type of @var{arg}, which can be either an expression
16783 or a name of a data type. With no argument, print the data type of
16784 @code{$}, the last value in the value history.
16786 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16787 is not actually evaluated, and any side-effecting operations (such as
16788 assignments or function calls) inside it do not take place.
16790 If @var{arg} is a variable or an expression, @code{whatis} prints its
16791 literal type as it is used in the source code. If the type was
16792 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16793 the data type underlying the @code{typedef}. If the type of the
16794 variable or the expression is a compound data type, such as
16795 @code{struct} or @code{class}, @code{whatis} never prints their
16796 fields or methods. It just prints the @code{struct}/@code{class}
16797 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16798 such a compound data type, use @code{ptype}.
16800 If @var{arg} is a type name that was defined using @code{typedef},
16801 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16802 Unrolling means that @code{whatis} will show the underlying type used
16803 in the @code{typedef} declaration of @var{arg}. However, if that
16804 underlying type is also a @code{typedef}, @code{whatis} will not
16807 For C code, the type names may also have the form @samp{class
16808 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16809 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16811 @var{flags} can be used to modify how the type is displayed.
16812 Available flags are:
16816 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16817 parameters and typedefs defined in a class when printing the class'
16818 members. The @code{/r} flag disables this.
16821 Do not print methods defined in the class.
16824 Print methods defined in the class. This is the default, but the flag
16825 exists in case you change the default with @command{set print type methods}.
16828 Do not print typedefs defined in the class. Note that this controls
16829 whether the typedef definition itself is printed, not whether typedef
16830 names are substituted when printing other types.
16833 Print typedefs defined in the class. This is the default, but the flag
16834 exists in case you change the default with @command{set print type typedefs}.
16838 @item ptype[/@var{flags}] [@var{arg}]
16839 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16840 detailed description of the type, instead of just the name of the type.
16841 @xref{Expressions, ,Expressions}.
16843 Contrary to @code{whatis}, @code{ptype} always unrolls any
16844 @code{typedef}s in its argument declaration, whether the argument is
16845 a variable, expression, or a data type. This means that @code{ptype}
16846 of a variable or an expression will not print literally its type as
16847 present in the source code---use @code{whatis} for that. @code{typedef}s at
16848 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16849 fields, methods and inner @code{class typedef}s of @code{struct}s,
16850 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16852 For example, for this variable declaration:
16855 typedef double real_t;
16856 struct complex @{ real_t real; double imag; @};
16857 typedef struct complex complex_t;
16859 real_t *real_pointer_var;
16863 the two commands give this output:
16867 (@value{GDBP}) whatis var
16869 (@value{GDBP}) ptype var
16870 type = struct complex @{
16874 (@value{GDBP}) whatis complex_t
16875 type = struct complex
16876 (@value{GDBP}) whatis struct complex
16877 type = struct complex
16878 (@value{GDBP}) ptype struct complex
16879 type = struct complex @{
16883 (@value{GDBP}) whatis real_pointer_var
16885 (@value{GDBP}) ptype real_pointer_var
16891 As with @code{whatis}, using @code{ptype} without an argument refers to
16892 the type of @code{$}, the last value in the value history.
16894 @cindex incomplete type
16895 Sometimes, programs use opaque data types or incomplete specifications
16896 of complex data structure. If the debug information included in the
16897 program does not allow @value{GDBN} to display a full declaration of
16898 the data type, it will say @samp{<incomplete type>}. For example,
16899 given these declarations:
16903 struct foo *fooptr;
16907 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16910 (@value{GDBP}) ptype foo
16911 $1 = <incomplete type>
16915 ``Incomplete type'' is C terminology for data types that are not
16916 completely specified.
16919 @item info types @var{regexp}
16921 Print a brief description of all types whose names match the regular
16922 expression @var{regexp} (or all types in your program, if you supply
16923 no argument). Each complete typename is matched as though it were a
16924 complete line; thus, @samp{i type value} gives information on all
16925 types in your program whose names include the string @code{value}, but
16926 @samp{i type ^value$} gives information only on types whose complete
16927 name is @code{value}.
16929 This command differs from @code{ptype} in two ways: first, like
16930 @code{whatis}, it does not print a detailed description; second, it
16931 lists all source files where a type is defined.
16933 @kindex info type-printers
16934 @item info type-printers
16935 Versions of @value{GDBN} that ship with Python scripting enabled may
16936 have ``type printers'' available. When using @command{ptype} or
16937 @command{whatis}, these printers are consulted when the name of a type
16938 is needed. @xref{Type Printing API}, for more information on writing
16941 @code{info type-printers} displays all the available type printers.
16943 @kindex enable type-printer
16944 @kindex disable type-printer
16945 @item enable type-printer @var{name}@dots{}
16946 @item disable type-printer @var{name}@dots{}
16947 These commands can be used to enable or disable type printers.
16950 @cindex local variables
16951 @item info scope @var{location}
16952 List all the variables local to a particular scope. This command
16953 accepts a @var{location} argument---a function name, a source line, or
16954 an address preceded by a @samp{*}, and prints all the variables local
16955 to the scope defined by that location. (@xref{Specify Location}, for
16956 details about supported forms of @var{location}.) For example:
16959 (@value{GDBP}) @b{info scope command_line_handler}
16960 Scope for command_line_handler:
16961 Symbol rl is an argument at stack/frame offset 8, length 4.
16962 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16963 Symbol linelength is in static storage at address 0x150a1c, length 4.
16964 Symbol p is a local variable in register $esi, length 4.
16965 Symbol p1 is a local variable in register $ebx, length 4.
16966 Symbol nline is a local variable in register $edx, length 4.
16967 Symbol repeat is a local variable at frame offset -8, length 4.
16971 This command is especially useful for determining what data to collect
16972 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16975 @kindex info source
16977 Show information about the current source file---that is, the source file for
16978 the function containing the current point of execution:
16981 the name of the source file, and the directory containing it,
16983 the directory it was compiled in,
16985 its length, in lines,
16987 which programming language it is written in,
16989 if the debug information provides it, the program that compiled the file
16990 (which may include, e.g., the compiler version and command line arguments),
16992 whether the executable includes debugging information for that file, and
16993 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16995 whether the debugging information includes information about
16996 preprocessor macros.
17000 @kindex info sources
17002 Print the names of all source files in your program for which there is
17003 debugging information, organized into two lists: files whose symbols
17004 have already been read, and files whose symbols will be read when needed.
17006 @kindex info functions
17007 @item info functions
17008 Print the names and data types of all defined functions.
17010 @item info functions @var{regexp}
17011 Print the names and data types of all defined functions
17012 whose names contain a match for regular expression @var{regexp}.
17013 Thus, @samp{info fun step} finds all functions whose names
17014 include @code{step}; @samp{info fun ^step} finds those whose names
17015 start with @code{step}. If a function name contains characters
17016 that conflict with the regular expression language (e.g.@:
17017 @samp{operator*()}), they may be quoted with a backslash.
17019 @kindex info variables
17020 @item info variables
17021 Print the names and data types of all variables that are defined
17022 outside of functions (i.e.@: excluding local variables).
17024 @item info variables @var{regexp}
17025 Print the names and data types of all variables (except for local
17026 variables) whose names contain a match for regular expression
17029 @kindex info classes
17030 @cindex Objective-C, classes and selectors
17032 @itemx info classes @var{regexp}
17033 Display all Objective-C classes in your program, or
17034 (with the @var{regexp} argument) all those matching a particular regular
17037 @kindex info selectors
17038 @item info selectors
17039 @itemx info selectors @var{regexp}
17040 Display all Objective-C selectors in your program, or
17041 (with the @var{regexp} argument) all those matching a particular regular
17045 This was never implemented.
17046 @kindex info methods
17048 @itemx info methods @var{regexp}
17049 The @code{info methods} command permits the user to examine all defined
17050 methods within C@t{++} program, or (with the @var{regexp} argument) a
17051 specific set of methods found in the various C@t{++} classes. Many
17052 C@t{++} classes provide a large number of methods. Thus, the output
17053 from the @code{ptype} command can be overwhelming and hard to use. The
17054 @code{info-methods} command filters the methods, printing only those
17055 which match the regular-expression @var{regexp}.
17058 @cindex opaque data types
17059 @kindex set opaque-type-resolution
17060 @item set opaque-type-resolution on
17061 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17062 declared as a pointer to a @code{struct}, @code{class}, or
17063 @code{union}---for example, @code{struct MyType *}---that is used in one
17064 source file although the full declaration of @code{struct MyType} is in
17065 another source file. The default is on.
17067 A change in the setting of this subcommand will not take effect until
17068 the next time symbols for a file are loaded.
17070 @item set opaque-type-resolution off
17071 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17072 is printed as follows:
17074 @{<no data fields>@}
17077 @kindex show opaque-type-resolution
17078 @item show opaque-type-resolution
17079 Show whether opaque types are resolved or not.
17081 @kindex set print symbol-loading
17082 @cindex print messages when symbols are loaded
17083 @item set print symbol-loading
17084 @itemx set print symbol-loading full
17085 @itemx set print symbol-loading brief
17086 @itemx set print symbol-loading off
17087 The @code{set print symbol-loading} command allows you to control the
17088 printing of messages when @value{GDBN} loads symbol information.
17089 By default a message is printed for the executable and one for each
17090 shared library, and normally this is what you want. However, when
17091 debugging apps with large numbers of shared libraries these messages
17093 When set to @code{brief} a message is printed for each executable,
17094 and when @value{GDBN} loads a collection of shared libraries at once
17095 it will only print one message regardless of the number of shared
17096 libraries. When set to @code{off} no messages are printed.
17098 @kindex show print symbol-loading
17099 @item show print symbol-loading
17100 Show whether messages will be printed when a @value{GDBN} command
17101 entered from the keyboard causes symbol information to be loaded.
17103 @kindex maint print symbols
17104 @cindex symbol dump
17105 @kindex maint print psymbols
17106 @cindex partial symbol dump
17107 @kindex maint print msymbols
17108 @cindex minimal symbol dump
17109 @item maint print symbols @var{filename}
17110 @itemx maint print psymbols @var{filename}
17111 @itemx maint print msymbols @var{filename}
17112 Write a dump of debugging symbol data into the file @var{filename}.
17113 These commands are used to debug the @value{GDBN} symbol-reading code. Only
17114 symbols with debugging data are included. If you use @samp{maint print
17115 symbols}, @value{GDBN} includes all the symbols for which it has already
17116 collected full details: that is, @var{filename} reflects symbols for
17117 only those files whose symbols @value{GDBN} has read. You can use the
17118 command @code{info sources} to find out which files these are. If you
17119 use @samp{maint print psymbols} instead, the dump shows information about
17120 symbols that @value{GDBN} only knows partially---that is, symbols defined in
17121 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
17122 @samp{maint print msymbols} dumps just the minimal symbol information
17123 required for each object file from which @value{GDBN} has read some symbols.
17124 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17125 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17127 @kindex maint info symtabs
17128 @kindex maint info psymtabs
17129 @cindex listing @value{GDBN}'s internal symbol tables
17130 @cindex symbol tables, listing @value{GDBN}'s internal
17131 @cindex full symbol tables, listing @value{GDBN}'s internal
17132 @cindex partial symbol tables, listing @value{GDBN}'s internal
17133 @item maint info symtabs @r{[} @var{regexp} @r{]}
17134 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17136 List the @code{struct symtab} or @code{struct partial_symtab}
17137 structures whose names match @var{regexp}. If @var{regexp} is not
17138 given, list them all. The output includes expressions which you can
17139 copy into a @value{GDBN} debugging this one to examine a particular
17140 structure in more detail. For example:
17143 (@value{GDBP}) maint info psymtabs dwarf2read
17144 @{ objfile /home/gnu/build/gdb/gdb
17145 ((struct objfile *) 0x82e69d0)
17146 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17147 ((struct partial_symtab *) 0x8474b10)
17150 text addresses 0x814d3c8 -- 0x8158074
17151 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17152 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17153 dependencies (none)
17156 (@value{GDBP}) maint info symtabs
17160 We see that there is one partial symbol table whose filename contains
17161 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17162 and we see that @value{GDBN} has not read in any symtabs yet at all.
17163 If we set a breakpoint on a function, that will cause @value{GDBN} to
17164 read the symtab for the compilation unit containing that function:
17167 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17168 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17170 (@value{GDBP}) maint info symtabs
17171 @{ objfile /home/gnu/build/gdb/gdb
17172 ((struct objfile *) 0x82e69d0)
17173 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17174 ((struct symtab *) 0x86c1f38)
17177 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17178 linetable ((struct linetable *) 0x8370fa0)
17179 debugformat DWARF 2
17185 @kindex maint info line-table
17186 @cindex listing @value{GDBN}'s internal line tables
17187 @cindex line tables, listing @value{GDBN}'s internal
17188 @item maint info line-table @r{[} @var{regexp} @r{]}
17190 List the @code{struct linetable} from all @code{struct symtab}
17191 instances whose name matches @var{regexp}. If @var{regexp} is not
17192 given, list the @code{struct linetable} from all @code{struct symtab}.
17194 @kindex maint set symbol-cache-size
17195 @cindex symbol cache size
17196 @item maint set symbol-cache-size @var{size}
17197 Set the size of the symbol cache to @var{size}.
17198 The default size is intended to be good enough for debugging
17199 most applications. This option exists to allow for experimenting
17200 with different sizes.
17202 @kindex maint show symbol-cache-size
17203 @item maint show symbol-cache-size
17204 Show the size of the symbol cache.
17206 @kindex maint print symbol-cache
17207 @cindex symbol cache, printing its contents
17208 @item maint print symbol-cache
17209 Print the contents of the symbol cache.
17210 This is useful when debugging symbol cache issues.
17212 @kindex maint print symbol-cache-statistics
17213 @cindex symbol cache, printing usage statistics
17214 @item maint print symbol-cache-statistics
17215 Print symbol cache usage statistics.
17216 This helps determine how well the cache is being utilized.
17218 @kindex maint flush-symbol-cache
17219 @cindex symbol cache, flushing
17220 @item maint flush-symbol-cache
17221 Flush the contents of the symbol cache, all entries are removed.
17222 This command is useful when debugging the symbol cache.
17223 It is also useful when collecting performance data.
17228 @chapter Altering Execution
17230 Once you think you have found an error in your program, you might want to
17231 find out for certain whether correcting the apparent error would lead to
17232 correct results in the rest of the run. You can find the answer by
17233 experiment, using the @value{GDBN} features for altering execution of the
17236 For example, you can store new values into variables or memory
17237 locations, give your program a signal, restart it at a different
17238 address, or even return prematurely from a function.
17241 * Assignment:: Assignment to variables
17242 * Jumping:: Continuing at a different address
17243 * Signaling:: Giving your program a signal
17244 * Returning:: Returning from a function
17245 * Calling:: Calling your program's functions
17246 * Patching:: Patching your program
17247 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17251 @section Assignment to Variables
17254 @cindex setting variables
17255 To alter the value of a variable, evaluate an assignment expression.
17256 @xref{Expressions, ,Expressions}. For example,
17263 stores the value 4 into the variable @code{x}, and then prints the
17264 value of the assignment expression (which is 4).
17265 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17266 information on operators in supported languages.
17268 @kindex set variable
17269 @cindex variables, setting
17270 If you are not interested in seeing the value of the assignment, use the
17271 @code{set} command instead of the @code{print} command. @code{set} is
17272 really the same as @code{print} except that the expression's value is
17273 not printed and is not put in the value history (@pxref{Value History,
17274 ,Value History}). The expression is evaluated only for its effects.
17276 If the beginning of the argument string of the @code{set} command
17277 appears identical to a @code{set} subcommand, use the @code{set
17278 variable} command instead of just @code{set}. This command is identical
17279 to @code{set} except for its lack of subcommands. For example, if your
17280 program has a variable @code{width}, you get an error if you try to set
17281 a new value with just @samp{set width=13}, because @value{GDBN} has the
17282 command @code{set width}:
17285 (@value{GDBP}) whatis width
17287 (@value{GDBP}) p width
17289 (@value{GDBP}) set width=47
17290 Invalid syntax in expression.
17294 The invalid expression, of course, is @samp{=47}. In
17295 order to actually set the program's variable @code{width}, use
17298 (@value{GDBP}) set var width=47
17301 Because the @code{set} command has many subcommands that can conflict
17302 with the names of program variables, it is a good idea to use the
17303 @code{set variable} command instead of just @code{set}. For example, if
17304 your program has a variable @code{g}, you run into problems if you try
17305 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17306 the command @code{set gnutarget}, abbreviated @code{set g}:
17310 (@value{GDBP}) whatis g
17314 (@value{GDBP}) set g=4
17318 The program being debugged has been started already.
17319 Start it from the beginning? (y or n) y
17320 Starting program: /home/smith/cc_progs/a.out
17321 "/home/smith/cc_progs/a.out": can't open to read symbols:
17322 Invalid bfd target.
17323 (@value{GDBP}) show g
17324 The current BFD target is "=4".
17329 The program variable @code{g} did not change, and you silently set the
17330 @code{gnutarget} to an invalid value. In order to set the variable
17334 (@value{GDBP}) set var g=4
17337 @value{GDBN} allows more implicit conversions in assignments than C; you can
17338 freely store an integer value into a pointer variable or vice versa,
17339 and you can convert any structure to any other structure that is the
17340 same length or shorter.
17341 @comment FIXME: how do structs align/pad in these conversions?
17342 @comment /doc@cygnus.com 18dec1990
17344 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17345 construct to generate a value of specified type at a specified address
17346 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17347 to memory location @code{0x83040} as an integer (which implies a certain size
17348 and representation in memory), and
17351 set @{int@}0x83040 = 4
17355 stores the value 4 into that memory location.
17358 @section Continuing at a Different Address
17360 Ordinarily, when you continue your program, you do so at the place where
17361 it stopped, with the @code{continue} command. You can instead continue at
17362 an address of your own choosing, with the following commands:
17366 @kindex j @r{(@code{jump})}
17367 @item jump @var{location}
17368 @itemx j @var{location}
17369 Resume execution at @var{location}. Execution stops again immediately
17370 if there is a breakpoint there. @xref{Specify Location}, for a description
17371 of the different forms of @var{location}. It is common
17372 practice to use the @code{tbreak} command in conjunction with
17373 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17375 The @code{jump} command does not change the current stack frame, or
17376 the stack pointer, or the contents of any memory location or any
17377 register other than the program counter. If @var{location} is in
17378 a different function from the one currently executing, the results may
17379 be bizarre if the two functions expect different patterns of arguments or
17380 of local variables. For this reason, the @code{jump} command requests
17381 confirmation if the specified line is not in the function currently
17382 executing. However, even bizarre results are predictable if you are
17383 well acquainted with the machine-language code of your program.
17386 On many systems, you can get much the same effect as the @code{jump}
17387 command by storing a new value into the register @code{$pc}. The
17388 difference is that this does not start your program running; it only
17389 changes the address of where it @emph{will} run when you continue. For
17397 makes the next @code{continue} command or stepping command execute at
17398 address @code{0x485}, rather than at the address where your program stopped.
17399 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17401 The most common occasion to use the @code{jump} command is to back
17402 up---perhaps with more breakpoints set---over a portion of a program
17403 that has already executed, in order to examine its execution in more
17408 @section Giving your Program a Signal
17409 @cindex deliver a signal to a program
17413 @item signal @var{signal}
17414 Resume execution where your program is stopped, but immediately give it the
17415 signal @var{signal}. The @var{signal} can be the name or the number of a
17416 signal. For example, on many systems @code{signal 2} and @code{signal
17417 SIGINT} are both ways of sending an interrupt signal.
17419 Alternatively, if @var{signal} is zero, continue execution without
17420 giving a signal. This is useful when your program stopped on account of
17421 a signal and would ordinarily see the signal when resumed with the
17422 @code{continue} command; @samp{signal 0} causes it to resume without a
17425 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17426 delivered to the currently selected thread, not the thread that last
17427 reported a stop. This includes the situation where a thread was
17428 stopped due to a signal. So if you want to continue execution
17429 suppressing the signal that stopped a thread, you should select that
17430 same thread before issuing the @samp{signal 0} command. If you issue
17431 the @samp{signal 0} command with another thread as the selected one,
17432 @value{GDBN} detects that and asks for confirmation.
17434 Invoking the @code{signal} command is not the same as invoking the
17435 @code{kill} utility from the shell. Sending a signal with @code{kill}
17436 causes @value{GDBN} to decide what to do with the signal depending on
17437 the signal handling tables (@pxref{Signals}). The @code{signal} command
17438 passes the signal directly to your program.
17440 @code{signal} does not repeat when you press @key{RET} a second time
17441 after executing the command.
17443 @kindex queue-signal
17444 @item queue-signal @var{signal}
17445 Queue @var{signal} to be delivered immediately to the current thread
17446 when execution of the thread resumes. The @var{signal} can be the name or
17447 the number of a signal. For example, on many systems @code{signal 2} and
17448 @code{signal SIGINT} are both ways of sending an interrupt signal.
17449 The handling of the signal must be set to pass the signal to the program,
17450 otherwise @value{GDBN} will report an error.
17451 You can control the handling of signals from @value{GDBN} with the
17452 @code{handle} command (@pxref{Signals}).
17454 Alternatively, if @var{signal} is zero, any currently queued signal
17455 for the current thread is discarded and when execution resumes no signal
17456 will be delivered. This is useful when your program stopped on account
17457 of a signal and would ordinarily see the signal when resumed with the
17458 @code{continue} command.
17460 This command differs from the @code{signal} command in that the signal
17461 is just queued, execution is not resumed. And @code{queue-signal} cannot
17462 be used to pass a signal whose handling state has been set to @code{nopass}
17467 @xref{stepping into signal handlers}, for information on how stepping
17468 commands behave when the thread has a signal queued.
17471 @section Returning from a Function
17474 @cindex returning from a function
17477 @itemx return @var{expression}
17478 You can cancel execution of a function call with the @code{return}
17479 command. If you give an
17480 @var{expression} argument, its value is used as the function's return
17484 When you use @code{return}, @value{GDBN} discards the selected stack frame
17485 (and all frames within it). You can think of this as making the
17486 discarded frame return prematurely. If you wish to specify a value to
17487 be returned, give that value as the argument to @code{return}.
17489 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17490 Frame}), and any other frames inside of it, leaving its caller as the
17491 innermost remaining frame. That frame becomes selected. The
17492 specified value is stored in the registers used for returning values
17495 The @code{return} command does not resume execution; it leaves the
17496 program stopped in the state that would exist if the function had just
17497 returned. In contrast, the @code{finish} command (@pxref{Continuing
17498 and Stepping, ,Continuing and Stepping}) resumes execution until the
17499 selected stack frame returns naturally.
17501 @value{GDBN} needs to know how the @var{expression} argument should be set for
17502 the inferior. The concrete registers assignment depends on the OS ABI and the
17503 type being returned by the selected stack frame. For example it is common for
17504 OS ABI to return floating point values in FPU registers while integer values in
17505 CPU registers. Still some ABIs return even floating point values in CPU
17506 registers. Larger integer widths (such as @code{long long int}) also have
17507 specific placement rules. @value{GDBN} already knows the OS ABI from its
17508 current target so it needs to find out also the type being returned to make the
17509 assignment into the right register(s).
17511 Normally, the selected stack frame has debug info. @value{GDBN} will always
17512 use the debug info instead of the implicit type of @var{expression} when the
17513 debug info is available. For example, if you type @kbd{return -1}, and the
17514 function in the current stack frame is declared to return a @code{long long
17515 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17516 into a @code{long long int}:
17519 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17521 (@value{GDBP}) return -1
17522 Make func return now? (y or n) y
17523 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17524 43 printf ("result=%lld\n", func ());
17528 However, if the selected stack frame does not have a debug info, e.g., if the
17529 function was compiled without debug info, @value{GDBN} has to find out the type
17530 to return from user. Specifying a different type by mistake may set the value
17531 in different inferior registers than the caller code expects. For example,
17532 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17533 of a @code{long long int} result for a debug info less function (on 32-bit
17534 architectures). Therefore the user is required to specify the return type by
17535 an appropriate cast explicitly:
17538 Breakpoint 2, 0x0040050b in func ()
17539 (@value{GDBP}) return -1
17540 Return value type not available for selected stack frame.
17541 Please use an explicit cast of the value to return.
17542 (@value{GDBP}) return (long long int) -1
17543 Make selected stack frame return now? (y or n) y
17544 #0 0x00400526 in main ()
17549 @section Calling Program Functions
17552 @cindex calling functions
17553 @cindex inferior functions, calling
17554 @item print @var{expr}
17555 Evaluate the expression @var{expr} and display the resulting value.
17556 The expression may include calls to functions in the program being
17560 @item call @var{expr}
17561 Evaluate the expression @var{expr} without displaying @code{void}
17564 You can use this variant of the @code{print} command if you want to
17565 execute a function from your program that does not return anything
17566 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17567 with @code{void} returned values that @value{GDBN} will otherwise
17568 print. If the result is not void, it is printed and saved in the
17572 It is possible for the function you call via the @code{print} or
17573 @code{call} command to generate a signal (e.g., if there's a bug in
17574 the function, or if you passed it incorrect arguments). What happens
17575 in that case is controlled by the @code{set unwindonsignal} command.
17577 Similarly, with a C@t{++} program it is possible for the function you
17578 call via the @code{print} or @code{call} command to generate an
17579 exception that is not handled due to the constraints of the dummy
17580 frame. In this case, any exception that is raised in the frame, but has
17581 an out-of-frame exception handler will not be found. GDB builds a
17582 dummy-frame for the inferior function call, and the unwinder cannot
17583 seek for exception handlers outside of this dummy-frame. What happens
17584 in that case is controlled by the
17585 @code{set unwind-on-terminating-exception} command.
17588 @item set unwindonsignal
17589 @kindex set unwindonsignal
17590 @cindex unwind stack in called functions
17591 @cindex call dummy stack unwinding
17592 Set unwinding of the stack if a signal is received while in a function
17593 that @value{GDBN} called in the program being debugged. If set to on,
17594 @value{GDBN} unwinds the stack it created for the call and restores
17595 the context to what it was before the call. If set to off (the
17596 default), @value{GDBN} stops in the frame where the signal was
17599 @item show unwindonsignal
17600 @kindex show unwindonsignal
17601 Show the current setting of stack unwinding in the functions called by
17604 @item set unwind-on-terminating-exception
17605 @kindex set unwind-on-terminating-exception
17606 @cindex unwind stack in called functions with unhandled exceptions
17607 @cindex call dummy stack unwinding on unhandled exception.
17608 Set unwinding of the stack if a C@t{++} exception is raised, but left
17609 unhandled while in a function that @value{GDBN} called in the program being
17610 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17611 it created for the call and restores the context to what it was before
17612 the call. If set to off, @value{GDBN} the exception is delivered to
17613 the default C@t{++} exception handler and the inferior terminated.
17615 @item show unwind-on-terminating-exception
17616 @kindex show unwind-on-terminating-exception
17617 Show the current setting of stack unwinding in the functions called by
17622 @cindex weak alias functions
17623 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17624 for another function. In such case, @value{GDBN} might not pick up
17625 the type information, including the types of the function arguments,
17626 which causes @value{GDBN} to call the inferior function incorrectly.
17627 As a result, the called function will function erroneously and may
17628 even crash. A solution to that is to use the name of the aliased
17632 @section Patching Programs
17634 @cindex patching binaries
17635 @cindex writing into executables
17636 @cindex writing into corefiles
17638 By default, @value{GDBN} opens the file containing your program's
17639 executable code (or the corefile) read-only. This prevents accidental
17640 alterations to machine code; but it also prevents you from intentionally
17641 patching your program's binary.
17643 If you'd like to be able to patch the binary, you can specify that
17644 explicitly with the @code{set write} command. For example, you might
17645 want to turn on internal debugging flags, or even to make emergency
17651 @itemx set write off
17652 If you specify @samp{set write on}, @value{GDBN} opens executable and
17653 core files for both reading and writing; if you specify @kbd{set write
17654 off} (the default), @value{GDBN} opens them read-only.
17656 If you have already loaded a file, you must load it again (using the
17657 @code{exec-file} or @code{core-file} command) after changing @code{set
17658 write}, for your new setting to take effect.
17662 Display whether executable files and core files are opened for writing
17663 as well as reading.
17666 @node Compiling and Injecting Code
17667 @section Compiling and injecting code in @value{GDBN}
17668 @cindex injecting code
17669 @cindex writing into executables
17670 @cindex compiling code
17672 @value{GDBN} supports on-demand compilation and code injection into
17673 programs running under @value{GDBN}. GCC 5.0 or higher built with
17674 @file{libcc1.so} must be installed for this functionality to be enabled.
17675 This functionality is implemented with the following commands.
17678 @kindex compile code
17679 @item compile code @var{source-code}
17680 @itemx compile code -raw @var{--} @var{source-code}
17681 Compile @var{source-code} with the compiler language found as the current
17682 language in @value{GDBN} (@pxref{Languages}). If compilation and
17683 injection is not supported with the current language specified in
17684 @value{GDBN}, or the compiler does not support this feature, an error
17685 message will be printed. If @var{source-code} compiles and links
17686 successfully, @value{GDBN} will load the object-code emitted,
17687 and execute it within the context of the currently selected inferior.
17688 It is important to note that the compiled code is executed immediately.
17689 After execution, the compiled code is removed from @value{GDBN} and any
17690 new types or variables you have defined will be deleted.
17692 The command allows you to specify @var{source-code} in two ways.
17693 The simplest method is to provide a single line of code to the command.
17697 compile code printf ("hello world\n");
17700 If you specify options on the command line as well as source code, they
17701 may conflict. The @samp{--} delimiter can be used to separate options
17702 from actual source code. E.g.:
17705 compile code -r -- printf ("hello world\n");
17708 Alternatively you can enter source code as multiple lines of text. To
17709 enter this mode, invoke the @samp{compile code} command without any text
17710 following the command. This will start the multiple-line editor and
17711 allow you to type as many lines of source code as required. When you
17712 have completed typing, enter @samp{end} on its own line to exit the
17717 >printf ("hello\n");
17718 >printf ("world\n");
17722 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17723 provided @var{source-code} in a callable scope. In this case, you must
17724 specify the entry point of the code by defining a function named
17725 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17726 inferior. Using @samp{-raw} option may be needed for example when
17727 @var{source-code} requires @samp{#include} lines which may conflict with
17728 inferior symbols otherwise.
17730 @kindex compile file
17731 @item compile file @var{filename}
17732 @itemx compile file -raw @var{filename}
17733 Like @code{compile code}, but take the source code from @var{filename}.
17736 compile file /home/user/example.c
17741 @item compile print @var{expr}
17742 @itemx compile print /@var{f} @var{expr}
17743 Compile and execute @var{expr} with the compiler language found as the
17744 current language in @value{GDBN} (@pxref{Languages}). By default the
17745 value of @var{expr} is printed in a format appropriate to its data type;
17746 you can choose a different format by specifying @samp{/@var{f}}, where
17747 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17750 @item compile print
17751 @itemx compile print /@var{f}
17752 @cindex reprint the last value
17753 Alternatively you can enter the expression (source code producing it) as
17754 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17755 command without any text following the command. This will start the
17756 multiple-line editor.
17760 The process of compiling and injecting the code can be inspected using:
17763 @anchor{set debug compile}
17764 @item set debug compile
17765 @cindex compile command debugging info
17766 Turns on or off display of @value{GDBN} process of compiling and
17767 injecting the code. The default is off.
17769 @item show debug compile
17770 Displays the current state of displaying @value{GDBN} process of
17771 compiling and injecting the code.
17774 @subsection Compilation options for the @code{compile} command
17776 @value{GDBN} needs to specify the right compilation options for the code
17777 to be injected, in part to make its ABI compatible with the inferior
17778 and in part to make the injected code compatible with @value{GDBN}'s
17782 The options used, in increasing precedence:
17785 @item target architecture and OS options (@code{gdbarch})
17786 These options depend on target processor type and target operating
17787 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17788 (@code{-m64}) compilation option.
17790 @item compilation options recorded in the target
17791 @value{NGCC} (since version 4.7) stores the options used for compilation
17792 into @code{DW_AT_producer} part of DWARF debugging information according
17793 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17794 explicitly specify @code{-g} during inferior compilation otherwise
17795 @value{NGCC} produces no DWARF. This feature is only relevant for
17796 platforms where @code{-g} produces DWARF by default, otherwise one may
17797 try to enforce DWARF by using @code{-gdwarf-4}.
17799 @item compilation options set by @code{set compile-args}
17803 You can override compilation options using the following command:
17806 @item set compile-args
17807 @cindex compile command options override
17808 Set compilation options used for compiling and injecting code with the
17809 @code{compile} commands. These options override any conflicting ones
17810 from the target architecture and/or options stored during inferior
17813 @item show compile-args
17814 Displays the current state of compilation options override.
17815 This does not show all the options actually used during compilation,
17816 use @ref{set debug compile} for that.
17819 @subsection Caveats when using the @code{compile} command
17821 There are a few caveats to keep in mind when using the @code{compile}
17822 command. As the caveats are different per language, the table below
17823 highlights specific issues on a per language basis.
17826 @item C code examples and caveats
17827 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17828 attempt to compile the source code with a @samp{C} compiler. The source
17829 code provided to the @code{compile} command will have much the same
17830 access to variables and types as it normally would if it were part of
17831 the program currently being debugged in @value{GDBN}.
17833 Below is a sample program that forms the basis of the examples that
17834 follow. This program has been compiled and loaded into @value{GDBN},
17835 much like any other normal debugging session.
17838 void function1 (void)
17841 printf ("function 1\n");
17844 void function2 (void)
17859 For the purposes of the examples in this section, the program above has
17860 been compiled, loaded into @value{GDBN}, stopped at the function
17861 @code{main}, and @value{GDBN} is awaiting input from the user.
17863 To access variables and types for any program in @value{GDBN}, the
17864 program must be compiled and packaged with debug information. The
17865 @code{compile} command is not an exception to this rule. Without debug
17866 information, you can still use the @code{compile} command, but you will
17867 be very limited in what variables and types you can access.
17869 So with that in mind, the example above has been compiled with debug
17870 information enabled. The @code{compile} command will have access to
17871 all variables and types (except those that may have been optimized
17872 out). Currently, as @value{GDBN} has stopped the program in the
17873 @code{main} function, the @code{compile} command would have access to
17874 the variable @code{k}. You could invoke the @code{compile} command
17875 and type some source code to set the value of @code{k}. You can also
17876 read it, or do anything with that variable you would normally do in
17877 @code{C}. Be aware that changes to inferior variables in the
17878 @code{compile} command are persistent. In the following example:
17881 compile code k = 3;
17885 the variable @code{k} is now 3. It will retain that value until
17886 something else in the example program changes it, or another
17887 @code{compile} command changes it.
17889 Normal scope and access rules apply to source code compiled and
17890 injected by the @code{compile} command. In the example, the variables
17891 @code{j} and @code{k} are not accessible yet, because the program is
17892 currently stopped in the @code{main} function, where these variables
17893 are not in scope. Therefore, the following command
17896 compile code j = 3;
17900 will result in a compilation error message.
17902 Once the program is continued, execution will bring these variables in
17903 scope, and they will become accessible; then the code you specify via
17904 the @code{compile} command will be able to access them.
17906 You can create variables and types with the @code{compile} command as
17907 part of your source code. Variables and types that are created as part
17908 of the @code{compile} command are not visible to the rest of the program for
17909 the duration of its run. This example is valid:
17912 compile code int ff = 5; printf ("ff is %d\n", ff);
17915 However, if you were to type the following into @value{GDBN} after that
17916 command has completed:
17919 compile code printf ("ff is %d\n'', ff);
17923 a compiler error would be raised as the variable @code{ff} no longer
17924 exists. Object code generated and injected by the @code{compile}
17925 command is removed when its execution ends. Caution is advised
17926 when assigning to program variables values of variables created by the
17927 code submitted to the @code{compile} command. This example is valid:
17930 compile code int ff = 5; k = ff;
17933 The value of the variable @code{ff} is assigned to @code{k}. The variable
17934 @code{k} does not require the existence of @code{ff} to maintain the value
17935 it has been assigned. However, pointers require particular care in
17936 assignment. If the source code compiled with the @code{compile} command
17937 changed the address of a pointer in the example program, perhaps to a
17938 variable created in the @code{compile} command, that pointer would point
17939 to an invalid location when the command exits. The following example
17940 would likely cause issues with your debugged program:
17943 compile code int ff = 5; p = &ff;
17946 In this example, @code{p} would point to @code{ff} when the
17947 @code{compile} command is executing the source code provided to it.
17948 However, as variables in the (example) program persist with their
17949 assigned values, the variable @code{p} would point to an invalid
17950 location when the command exists. A general rule should be followed
17951 in that you should either assign @code{NULL} to any assigned pointers,
17952 or restore a valid location to the pointer before the command exits.
17954 Similar caution must be exercised with any structs, unions, and typedefs
17955 defined in @code{compile} command. Types defined in the @code{compile}
17956 command will no longer be available in the next @code{compile} command.
17957 Therefore, if you cast a variable to a type defined in the
17958 @code{compile} command, care must be taken to ensure that any future
17959 need to resolve the type can be achieved.
17962 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17963 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17964 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17965 Compilation failed.
17966 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17970 Variables that have been optimized away by the compiler are not
17971 accessible to the code submitted to the @code{compile} command.
17972 Access to those variables will generate a compiler error which @value{GDBN}
17973 will print to the console.
17976 @subsection Compiler search for the @code{compile} command
17978 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17979 may not be obvious for remote targets of different architecture than where
17980 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17981 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17982 command @code{set environment}). @xref{Environment}. @code{PATH} on
17983 @value{GDBN} host is searched for @value{NGCC} binary matching the
17984 target architecture and operating system.
17986 Specifically @code{PATH} is searched for binaries matching regular expression
17987 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17988 debugged. @var{arch} is processor name --- multiarch is supported, so for
17989 example both @code{i386} and @code{x86_64} targets look for pattern
17990 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17991 for pattern @code{s390x?}. @var{os} is currently supported only for
17992 pattern @code{linux(-gnu)?}.
17995 @chapter @value{GDBN} Files
17997 @value{GDBN} needs to know the file name of the program to be debugged,
17998 both in order to read its symbol table and in order to start your
17999 program. To debug a core dump of a previous run, you must also tell
18000 @value{GDBN} the name of the core dump file.
18003 * Files:: Commands to specify files
18004 * File Caching:: Information about @value{GDBN}'s file caching
18005 * Separate Debug Files:: Debugging information in separate files
18006 * MiniDebugInfo:: Debugging information in a special section
18007 * Index Files:: Index files speed up GDB
18008 * Symbol Errors:: Errors reading symbol files
18009 * Data Files:: GDB data files
18013 @section Commands to Specify Files
18015 @cindex symbol table
18016 @cindex core dump file
18018 You may want to specify executable and core dump file names. The usual
18019 way to do this is at start-up time, using the arguments to
18020 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18021 Out of @value{GDBN}}).
18023 Occasionally it is necessary to change to a different file during a
18024 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18025 specify a file you want to use. Or you are debugging a remote target
18026 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18027 Program}). In these situations the @value{GDBN} commands to specify
18028 new files are useful.
18031 @cindex executable file
18033 @item file @var{filename}
18034 Use @var{filename} as the program to be debugged. It is read for its
18035 symbols and for the contents of pure memory. It is also the program
18036 executed when you use the @code{run} command. If you do not specify a
18037 directory and the file is not found in the @value{GDBN} working directory,
18038 @value{GDBN} uses the environment variable @code{PATH} as a list of
18039 directories to search, just as the shell does when looking for a program
18040 to run. You can change the value of this variable, for both @value{GDBN}
18041 and your program, using the @code{path} command.
18043 @cindex unlinked object files
18044 @cindex patching object files
18045 You can load unlinked object @file{.o} files into @value{GDBN} using
18046 the @code{file} command. You will not be able to ``run'' an object
18047 file, but you can disassemble functions and inspect variables. Also,
18048 if the underlying BFD functionality supports it, you could use
18049 @kbd{gdb -write} to patch object files using this technique. Note
18050 that @value{GDBN} can neither interpret nor modify relocations in this
18051 case, so branches and some initialized variables will appear to go to
18052 the wrong place. But this feature is still handy from time to time.
18055 @code{file} with no argument makes @value{GDBN} discard any information it
18056 has on both executable file and the symbol table.
18059 @item exec-file @r{[} @var{filename} @r{]}
18060 Specify that the program to be run (but not the symbol table) is found
18061 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18062 if necessary to locate your program. Omitting @var{filename} means to
18063 discard information on the executable file.
18065 @kindex symbol-file
18066 @item symbol-file @r{[} @var{filename} @r{]}
18067 Read symbol table information from file @var{filename}. @code{PATH} is
18068 searched when necessary. Use the @code{file} command to get both symbol
18069 table and program to run from the same file.
18071 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18072 program's symbol table.
18074 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18075 some breakpoints and auto-display expressions. This is because they may
18076 contain pointers to the internal data recording symbols and data types,
18077 which are part of the old symbol table data being discarded inside
18080 @code{symbol-file} does not repeat if you press @key{RET} again after
18083 When @value{GDBN} is configured for a particular environment, it
18084 understands debugging information in whatever format is the standard
18085 generated for that environment; you may use either a @sc{gnu} compiler, or
18086 other compilers that adhere to the local conventions.
18087 Best results are usually obtained from @sc{gnu} compilers; for example,
18088 using @code{@value{NGCC}} you can generate debugging information for
18091 For most kinds of object files, with the exception of old SVR3 systems
18092 using COFF, the @code{symbol-file} command does not normally read the
18093 symbol table in full right away. Instead, it scans the symbol table
18094 quickly to find which source files and which symbols are present. The
18095 details are read later, one source file at a time, as they are needed.
18097 The purpose of this two-stage reading strategy is to make @value{GDBN}
18098 start up faster. For the most part, it is invisible except for
18099 occasional pauses while the symbol table details for a particular source
18100 file are being read. (The @code{set verbose} command can turn these
18101 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18102 Warnings and Messages}.)
18104 We have not implemented the two-stage strategy for COFF yet. When the
18105 symbol table is stored in COFF format, @code{symbol-file} reads the
18106 symbol table data in full right away. Note that ``stabs-in-COFF''
18107 still does the two-stage strategy, since the debug info is actually
18111 @cindex reading symbols immediately
18112 @cindex symbols, reading immediately
18113 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18114 @itemx file @r{[} -readnow @r{]} @var{filename}
18115 You can override the @value{GDBN} two-stage strategy for reading symbol
18116 tables by using the @samp{-readnow} option with any of the commands that
18117 load symbol table information, if you want to be sure @value{GDBN} has the
18118 entire symbol table available.
18120 @c FIXME: for now no mention of directories, since this seems to be in
18121 @c flux. 13mar1992 status is that in theory GDB would look either in
18122 @c current dir or in same dir as myprog; but issues like competing
18123 @c GDB's, or clutter in system dirs, mean that in practice right now
18124 @c only current dir is used. FFish says maybe a special GDB hierarchy
18125 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18129 @item core-file @r{[}@var{filename}@r{]}
18131 Specify the whereabouts of a core dump file to be used as the ``contents
18132 of memory''. Traditionally, core files contain only some parts of the
18133 address space of the process that generated them; @value{GDBN} can access the
18134 executable file itself for other parts.
18136 @code{core-file} with no argument specifies that no core file is
18139 Note that the core file is ignored when your program is actually running
18140 under @value{GDBN}. So, if you have been running your program and you
18141 wish to debug a core file instead, you must kill the subprocess in which
18142 the program is running. To do this, use the @code{kill} command
18143 (@pxref{Kill Process, ,Killing the Child Process}).
18145 @kindex add-symbol-file
18146 @cindex dynamic linking
18147 @item add-symbol-file @var{filename} @var{address}
18148 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18149 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18150 The @code{add-symbol-file} command reads additional symbol table
18151 information from the file @var{filename}. You would use this command
18152 when @var{filename} has been dynamically loaded (by some other means)
18153 into the program that is running. The @var{address} should give the memory
18154 address at which the file has been loaded; @value{GDBN} cannot figure
18155 this out for itself. You can additionally specify an arbitrary number
18156 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18157 section name and base address for that section. You can specify any
18158 @var{address} as an expression.
18160 The symbol table of the file @var{filename} is added to the symbol table
18161 originally read with the @code{symbol-file} command. You can use the
18162 @code{add-symbol-file} command any number of times; the new symbol data
18163 thus read is kept in addition to the old.
18165 Changes can be reverted using the command @code{remove-symbol-file}.
18167 @cindex relocatable object files, reading symbols from
18168 @cindex object files, relocatable, reading symbols from
18169 @cindex reading symbols from relocatable object files
18170 @cindex symbols, reading from relocatable object files
18171 @cindex @file{.o} files, reading symbols from
18172 Although @var{filename} is typically a shared library file, an
18173 executable file, or some other object file which has been fully
18174 relocated for loading into a process, you can also load symbolic
18175 information from relocatable @file{.o} files, as long as:
18179 the file's symbolic information refers only to linker symbols defined in
18180 that file, not to symbols defined by other object files,
18182 every section the file's symbolic information refers to has actually
18183 been loaded into the inferior, as it appears in the file, and
18185 you can determine the address at which every section was loaded, and
18186 provide these to the @code{add-symbol-file} command.
18190 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18191 relocatable files into an already running program; such systems
18192 typically make the requirements above easy to meet. However, it's
18193 important to recognize that many native systems use complex link
18194 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18195 assembly, for example) that make the requirements difficult to meet. In
18196 general, one cannot assume that using @code{add-symbol-file} to read a
18197 relocatable object file's symbolic information will have the same effect
18198 as linking the relocatable object file into the program in the normal
18201 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18203 @kindex remove-symbol-file
18204 @item remove-symbol-file @var{filename}
18205 @item remove-symbol-file -a @var{address}
18206 Remove a symbol file added via the @code{add-symbol-file} command. The
18207 file to remove can be identified by its @var{filename} or by an @var{address}
18208 that lies within the boundaries of this symbol file in memory. Example:
18211 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18212 add symbol table from file "/home/user/gdb/mylib.so" at
18213 .text_addr = 0x7ffff7ff9480
18215 Reading symbols from /home/user/gdb/mylib.so...done.
18216 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18217 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18222 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18224 @kindex add-symbol-file-from-memory
18225 @cindex @code{syscall DSO}
18226 @cindex load symbols from memory
18227 @item add-symbol-file-from-memory @var{address}
18228 Load symbols from the given @var{address} in a dynamically loaded
18229 object file whose image is mapped directly into the inferior's memory.
18230 For example, the Linux kernel maps a @code{syscall DSO} into each
18231 process's address space; this DSO provides kernel-specific code for
18232 some system calls. The argument can be any expression whose
18233 evaluation yields the address of the file's shared object file header.
18234 For this command to work, you must have used @code{symbol-file} or
18235 @code{exec-file} commands in advance.
18238 @item section @var{section} @var{addr}
18239 The @code{section} command changes the base address of the named
18240 @var{section} of the exec file to @var{addr}. This can be used if the
18241 exec file does not contain section addresses, (such as in the
18242 @code{a.out} format), or when the addresses specified in the file
18243 itself are wrong. Each section must be changed separately. The
18244 @code{info files} command, described below, lists all the sections and
18248 @kindex info target
18251 @code{info files} and @code{info target} are synonymous; both print the
18252 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18253 including the names of the executable and core dump files currently in
18254 use by @value{GDBN}, and the files from which symbols were loaded. The
18255 command @code{help target} lists all possible targets rather than
18258 @kindex maint info sections
18259 @item maint info sections
18260 Another command that can give you extra information about program sections
18261 is @code{maint info sections}. In addition to the section information
18262 displayed by @code{info files}, this command displays the flags and file
18263 offset of each section in the executable and core dump files. In addition,
18264 @code{maint info sections} provides the following command options (which
18265 may be arbitrarily combined):
18269 Display sections for all loaded object files, including shared libraries.
18270 @item @var{sections}
18271 Display info only for named @var{sections}.
18272 @item @var{section-flags}
18273 Display info only for sections for which @var{section-flags} are true.
18274 The section flags that @value{GDBN} currently knows about are:
18277 Section will have space allocated in the process when loaded.
18278 Set for all sections except those containing debug information.
18280 Section will be loaded from the file into the child process memory.
18281 Set for pre-initialized code and data, clear for @code{.bss} sections.
18283 Section needs to be relocated before loading.
18285 Section cannot be modified by the child process.
18287 Section contains executable code only.
18289 Section contains data only (no executable code).
18291 Section will reside in ROM.
18293 Section contains data for constructor/destructor lists.
18295 Section is not empty.
18297 An instruction to the linker to not output the section.
18298 @item COFF_SHARED_LIBRARY
18299 A notification to the linker that the section contains
18300 COFF shared library information.
18302 Section contains common symbols.
18305 @kindex set trust-readonly-sections
18306 @cindex read-only sections
18307 @item set trust-readonly-sections on
18308 Tell @value{GDBN} that readonly sections in your object file
18309 really are read-only (i.e.@: that their contents will not change).
18310 In that case, @value{GDBN} can fetch values from these sections
18311 out of the object file, rather than from the target program.
18312 For some targets (notably embedded ones), this can be a significant
18313 enhancement to debugging performance.
18315 The default is off.
18317 @item set trust-readonly-sections off
18318 Tell @value{GDBN} not to trust readonly sections. This means that
18319 the contents of the section might change while the program is running,
18320 and must therefore be fetched from the target when needed.
18322 @item show trust-readonly-sections
18323 Show the current setting of trusting readonly sections.
18326 All file-specifying commands allow both absolute and relative file names
18327 as arguments. @value{GDBN} always converts the file name to an absolute file
18328 name and remembers it that way.
18330 @cindex shared libraries
18331 @anchor{Shared Libraries}
18332 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18333 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18334 DSBT (TIC6X) shared libraries.
18336 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18337 shared libraries. @xref{Expat}.
18339 @value{GDBN} automatically loads symbol definitions from shared libraries
18340 when you use the @code{run} command, or when you examine a core file.
18341 (Before you issue the @code{run} command, @value{GDBN} does not understand
18342 references to a function in a shared library, however---unless you are
18343 debugging a core file).
18345 @c FIXME: some @value{GDBN} release may permit some refs to undef
18346 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18347 @c FIXME...lib; check this from time to time when updating manual
18349 There are times, however, when you may wish to not automatically load
18350 symbol definitions from shared libraries, such as when they are
18351 particularly large or there are many of them.
18353 To control the automatic loading of shared library symbols, use the
18357 @kindex set auto-solib-add
18358 @item set auto-solib-add @var{mode}
18359 If @var{mode} is @code{on}, symbols from all shared object libraries
18360 will be loaded automatically when the inferior begins execution, you
18361 attach to an independently started inferior, or when the dynamic linker
18362 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18363 is @code{off}, symbols must be loaded manually, using the
18364 @code{sharedlibrary} command. The default value is @code{on}.
18366 @cindex memory used for symbol tables
18367 If your program uses lots of shared libraries with debug info that
18368 takes large amounts of memory, you can decrease the @value{GDBN}
18369 memory footprint by preventing it from automatically loading the
18370 symbols from shared libraries. To that end, type @kbd{set
18371 auto-solib-add off} before running the inferior, then load each
18372 library whose debug symbols you do need with @kbd{sharedlibrary
18373 @var{regexp}}, where @var{regexp} is a regular expression that matches
18374 the libraries whose symbols you want to be loaded.
18376 @kindex show auto-solib-add
18377 @item show auto-solib-add
18378 Display the current autoloading mode.
18381 @cindex load shared library
18382 To explicitly load shared library symbols, use the @code{sharedlibrary}
18386 @kindex info sharedlibrary
18388 @item info share @var{regex}
18389 @itemx info sharedlibrary @var{regex}
18390 Print the names of the shared libraries which are currently loaded
18391 that match @var{regex}. If @var{regex} is omitted then print
18392 all shared libraries that are loaded.
18395 @item info dll @var{regex}
18396 This is an alias of @code{info sharedlibrary}.
18398 @kindex sharedlibrary
18400 @item sharedlibrary @var{regex}
18401 @itemx share @var{regex}
18402 Load shared object library symbols for files matching a
18403 Unix regular expression.
18404 As with files loaded automatically, it only loads shared libraries
18405 required by your program for a core file or after typing @code{run}. If
18406 @var{regex} is omitted all shared libraries required by your program are
18409 @item nosharedlibrary
18410 @kindex nosharedlibrary
18411 @cindex unload symbols from shared libraries
18412 Unload all shared object library symbols. This discards all symbols
18413 that have been loaded from all shared libraries. Symbols from shared
18414 libraries that were loaded by explicit user requests are not
18418 Sometimes you may wish that @value{GDBN} stops and gives you control
18419 when any of shared library events happen. The best way to do this is
18420 to use @code{catch load} and @code{catch unload} (@pxref{Set
18423 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18424 command for this. This command exists for historical reasons. It is
18425 less useful than setting a catchpoint, because it does not allow for
18426 conditions or commands as a catchpoint does.
18429 @item set stop-on-solib-events
18430 @kindex set stop-on-solib-events
18431 This command controls whether @value{GDBN} should give you control
18432 when the dynamic linker notifies it about some shared library event.
18433 The most common event of interest is loading or unloading of a new
18436 @item show stop-on-solib-events
18437 @kindex show stop-on-solib-events
18438 Show whether @value{GDBN} stops and gives you control when shared
18439 library events happen.
18442 Shared libraries are also supported in many cross or remote debugging
18443 configurations. @value{GDBN} needs to have access to the target's libraries;
18444 this can be accomplished either by providing copies of the libraries
18445 on the host system, or by asking @value{GDBN} to automatically retrieve the
18446 libraries from the target. If copies of the target libraries are
18447 provided, they need to be the same as the target libraries, although the
18448 copies on the target can be stripped as long as the copies on the host are
18451 @cindex where to look for shared libraries
18452 For remote debugging, you need to tell @value{GDBN} where the target
18453 libraries are, so that it can load the correct copies---otherwise, it
18454 may try to load the host's libraries. @value{GDBN} has two variables
18455 to specify the search directories for target libraries.
18458 @cindex prefix for executable and shared library file names
18459 @cindex system root, alternate
18460 @kindex set solib-absolute-prefix
18461 @kindex set sysroot
18462 @item set sysroot @var{path}
18463 Use @var{path} as the system root for the program being debugged. Any
18464 absolute shared library paths will be prefixed with @var{path}; many
18465 runtime loaders store the absolute paths to the shared library in the
18466 target program's memory. When starting processes remotely, and when
18467 attaching to already-running processes (local or remote), their
18468 executable filenames will be prefixed with @var{path} if reported to
18469 @value{GDBN} as absolute by the operating system. If you use
18470 @code{set sysroot} to find executables and shared libraries, they need
18471 to be laid out in the same way that they are on the target, with
18472 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18475 If @var{path} starts with the sequence @file{target:} and the target
18476 system is remote then @value{GDBN} will retrieve the target binaries
18477 from the remote system. This is only supported when using a remote
18478 target that supports the @code{remote get} command (@pxref{File
18479 Transfer,,Sending files to a remote system}). The part of @var{path}
18480 following the initial @file{target:} (if present) is used as system
18481 root prefix on the remote file system. If @var{path} starts with the
18482 sequence @file{remote:} this is converted to the sequence
18483 @file{target:} by @code{set sysroot}@footnote{Historically the
18484 functionality to retrieve binaries from the remote system was
18485 provided by prefixing @var{path} with @file{remote:}}. If you want
18486 to specify a local system root using a directory that happens to be
18487 named @file{target:} or @file{remote:}, you need to use some
18488 equivalent variant of the name like @file{./target:}.
18490 For targets with an MS-DOS based filesystem, such as MS-Windows and
18491 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18492 absolute file name with @var{path}. But first, on Unix hosts,
18493 @value{GDBN} converts all backslash directory separators into forward
18494 slashes, because the backslash is not a directory separator on Unix:
18497 c:\foo\bar.dll @result{} c:/foo/bar.dll
18500 Then, @value{GDBN} attempts prefixing the target file name with
18501 @var{path}, and looks for the resulting file name in the host file
18505 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18508 If that does not find the binary, @value{GDBN} tries removing
18509 the @samp{:} character from the drive spec, both for convenience, and,
18510 for the case of the host file system not supporting file names with
18514 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18517 This makes it possible to have a system root that mirrors a target
18518 with more than one drive. E.g., you may want to setup your local
18519 copies of the target system shared libraries like so (note @samp{c} vs
18523 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18524 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18525 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18529 and point the system root at @file{/path/to/sysroot}, so that
18530 @value{GDBN} can find the correct copies of both
18531 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18533 If that still does not find the binary, @value{GDBN} tries
18534 removing the whole drive spec from the target file name:
18537 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18540 This last lookup makes it possible to not care about the drive name,
18541 if you don't want or need to.
18543 The @code{set solib-absolute-prefix} command is an alias for @code{set
18546 @cindex default system root
18547 @cindex @samp{--with-sysroot}
18548 You can set the default system root by using the configure-time
18549 @samp{--with-sysroot} option. If the system root is inside
18550 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18551 @samp{--exec-prefix}), then the default system root will be updated
18552 automatically if the installed @value{GDBN} is moved to a new
18555 @kindex show sysroot
18557 Display the current executable and shared library prefix.
18559 @kindex set solib-search-path
18560 @item set solib-search-path @var{path}
18561 If this variable is set, @var{path} is a colon-separated list of
18562 directories to search for shared libraries. @samp{solib-search-path}
18563 is used after @samp{sysroot} fails to locate the library, or if the
18564 path to the library is relative instead of absolute. If you want to
18565 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18566 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18567 finding your host's libraries. @samp{sysroot} is preferred; setting
18568 it to a nonexistent directory may interfere with automatic loading
18569 of shared library symbols.
18571 @kindex show solib-search-path
18572 @item show solib-search-path
18573 Display the current shared library search path.
18575 @cindex DOS file-name semantics of file names.
18576 @kindex set target-file-system-kind (unix|dos-based|auto)
18577 @kindex show target-file-system-kind
18578 @item set target-file-system-kind @var{kind}
18579 Set assumed file system kind for target reported file names.
18581 Shared library file names as reported by the target system may not
18582 make sense as is on the system @value{GDBN} is running on. For
18583 example, when remote debugging a target that has MS-DOS based file
18584 system semantics, from a Unix host, the target may be reporting to
18585 @value{GDBN} a list of loaded shared libraries with file names such as
18586 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18587 drive letters, so the @samp{c:\} prefix is not normally understood as
18588 indicating an absolute file name, and neither is the backslash
18589 normally considered a directory separator character. In that case,
18590 the native file system would interpret this whole absolute file name
18591 as a relative file name with no directory components. This would make
18592 it impossible to point @value{GDBN} at a copy of the remote target's
18593 shared libraries on the host using @code{set sysroot}, and impractical
18594 with @code{set solib-search-path}. Setting
18595 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18596 to interpret such file names similarly to how the target would, and to
18597 map them to file names valid on @value{GDBN}'s native file system
18598 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18599 to one of the supported file system kinds. In that case, @value{GDBN}
18600 tries to determine the appropriate file system variant based on the
18601 current target's operating system (@pxref{ABI, ,Configuring the
18602 Current ABI}). The supported file system settings are:
18606 Instruct @value{GDBN} to assume the target file system is of Unix
18607 kind. Only file names starting the forward slash (@samp{/}) character
18608 are considered absolute, and the directory separator character is also
18612 Instruct @value{GDBN} to assume the target file system is DOS based.
18613 File names starting with either a forward slash, or a drive letter
18614 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18615 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18616 considered directory separators.
18619 Instruct @value{GDBN} to use the file system kind associated with the
18620 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18621 This is the default.
18625 @cindex file name canonicalization
18626 @cindex base name differences
18627 When processing file names provided by the user, @value{GDBN}
18628 frequently needs to compare them to the file names recorded in the
18629 program's debug info. Normally, @value{GDBN} compares just the
18630 @dfn{base names} of the files as strings, which is reasonably fast
18631 even for very large programs. (The base name of a file is the last
18632 portion of its name, after stripping all the leading directories.)
18633 This shortcut in comparison is based upon the assumption that files
18634 cannot have more than one base name. This is usually true, but
18635 references to files that use symlinks or similar filesystem
18636 facilities violate that assumption. If your program records files
18637 using such facilities, or if you provide file names to @value{GDBN}
18638 using symlinks etc., you can set @code{basenames-may-differ} to
18639 @code{true} to instruct @value{GDBN} to completely canonicalize each
18640 pair of file names it needs to compare. This will make file-name
18641 comparisons accurate, but at a price of a significant slowdown.
18644 @item set basenames-may-differ
18645 @kindex set basenames-may-differ
18646 Set whether a source file may have multiple base names.
18648 @item show basenames-may-differ
18649 @kindex show basenames-may-differ
18650 Show whether a source file may have multiple base names.
18654 @section File Caching
18655 @cindex caching of opened files
18656 @cindex caching of bfd objects
18658 To speed up file loading, and reduce memory usage, @value{GDBN} will
18659 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18660 BFD, bfd, The Binary File Descriptor Library}. The following commands
18661 allow visibility and control of the caching behavior.
18664 @kindex maint info bfds
18665 @item maint info bfds
18666 This prints information about each @code{bfd} object that is known to
18669 @kindex maint set bfd-sharing
18670 @kindex maint show bfd-sharing
18671 @kindex bfd caching
18672 @item maint set bfd-sharing
18673 @item maint show bfd-sharing
18674 Control whether @code{bfd} objects can be shared. When sharing is
18675 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18676 than reopening the same file. Turning sharing off does not cause
18677 already shared @code{bfd} objects to be unshared, but all future files
18678 that are opened will create a new @code{bfd} object. Similarly,
18679 re-enabling sharing does not cause multiple existing @code{bfd}
18680 objects to be collapsed into a single shared @code{bfd} object.
18682 @kindex set debug bfd-cache @var{level}
18683 @kindex bfd caching
18684 @item set debug bfd-cache @var{level}
18685 Turns on debugging of the bfd cache, setting the level to @var{level}.
18687 @kindex show debug bfd-cache
18688 @kindex bfd caching
18689 @item show debug bfd-cache
18690 Show the current debugging level of the bfd cache.
18693 @node Separate Debug Files
18694 @section Debugging Information in Separate Files
18695 @cindex separate debugging information files
18696 @cindex debugging information in separate files
18697 @cindex @file{.debug} subdirectories
18698 @cindex debugging information directory, global
18699 @cindex global debugging information directories
18700 @cindex build ID, and separate debugging files
18701 @cindex @file{.build-id} directory
18703 @value{GDBN} allows you to put a program's debugging information in a
18704 file separate from the executable itself, in a way that allows
18705 @value{GDBN} to find and load the debugging information automatically.
18706 Since debugging information can be very large---sometimes larger
18707 than the executable code itself---some systems distribute debugging
18708 information for their executables in separate files, which users can
18709 install only when they need to debug a problem.
18711 @value{GDBN} supports two ways of specifying the separate debug info
18716 The executable contains a @dfn{debug link} that specifies the name of
18717 the separate debug info file. The separate debug file's name is
18718 usually @file{@var{executable}.debug}, where @var{executable} is the
18719 name of the corresponding executable file without leading directories
18720 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18721 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18722 checksum for the debug file, which @value{GDBN} uses to validate that
18723 the executable and the debug file came from the same build.
18726 The executable contains a @dfn{build ID}, a unique bit string that is
18727 also present in the corresponding debug info file. (This is supported
18728 only on some operating systems, when using the ELF or PE file formats
18729 for binary files and the @sc{gnu} Binutils.) For more details about
18730 this feature, see the description of the @option{--build-id}
18731 command-line option in @ref{Options, , Command Line Options, ld.info,
18732 The GNU Linker}. The debug info file's name is not specified
18733 explicitly by the build ID, but can be computed from the build ID, see
18737 Depending on the way the debug info file is specified, @value{GDBN}
18738 uses two different methods of looking for the debug file:
18742 For the ``debug link'' method, @value{GDBN} looks up the named file in
18743 the directory of the executable file, then in a subdirectory of that
18744 directory named @file{.debug}, and finally under each one of the global debug
18745 directories, in a subdirectory whose name is identical to the leading
18746 directories of the executable's absolute file name.
18749 For the ``build ID'' method, @value{GDBN} looks in the
18750 @file{.build-id} subdirectory of each one of the global debug directories for
18751 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18752 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18753 are the rest of the bit string. (Real build ID strings are 32 or more
18754 hex characters, not 10.)
18757 So, for example, suppose you ask @value{GDBN} to debug
18758 @file{/usr/bin/ls}, which has a debug link that specifies the
18759 file @file{ls.debug}, and a build ID whose value in hex is
18760 @code{abcdef1234}. If the list of the global debug directories includes
18761 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18762 debug information files, in the indicated order:
18766 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18768 @file{/usr/bin/ls.debug}
18770 @file{/usr/bin/.debug/ls.debug}
18772 @file{/usr/lib/debug/usr/bin/ls.debug}.
18775 @anchor{debug-file-directory}
18776 Global debugging info directories default to what is set by @value{GDBN}
18777 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18778 you can also set the global debugging info directories, and view the list
18779 @value{GDBN} is currently using.
18783 @kindex set debug-file-directory
18784 @item set debug-file-directory @var{directories}
18785 Set the directories which @value{GDBN} searches for separate debugging
18786 information files to @var{directory}. Multiple path components can be set
18787 concatenating them by a path separator.
18789 @kindex show debug-file-directory
18790 @item show debug-file-directory
18791 Show the directories @value{GDBN} searches for separate debugging
18796 @cindex @code{.gnu_debuglink} sections
18797 @cindex debug link sections
18798 A debug link is a special section of the executable file named
18799 @code{.gnu_debuglink}. The section must contain:
18803 A filename, with any leading directory components removed, followed by
18806 zero to three bytes of padding, as needed to reach the next four-byte
18807 boundary within the section, and
18809 a four-byte CRC checksum, stored in the same endianness used for the
18810 executable file itself. The checksum is computed on the debugging
18811 information file's full contents by the function given below, passing
18812 zero as the @var{crc} argument.
18815 Any executable file format can carry a debug link, as long as it can
18816 contain a section named @code{.gnu_debuglink} with the contents
18819 @cindex @code{.note.gnu.build-id} sections
18820 @cindex build ID sections
18821 The build ID is a special section in the executable file (and in other
18822 ELF binary files that @value{GDBN} may consider). This section is
18823 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18824 It contains unique identification for the built files---the ID remains
18825 the same across multiple builds of the same build tree. The default
18826 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18827 content for the build ID string. The same section with an identical
18828 value is present in the original built binary with symbols, in its
18829 stripped variant, and in the separate debugging information file.
18831 The debugging information file itself should be an ordinary
18832 executable, containing a full set of linker symbols, sections, and
18833 debugging information. The sections of the debugging information file
18834 should have the same names, addresses, and sizes as the original file,
18835 but they need not contain any data---much like a @code{.bss} section
18836 in an ordinary executable.
18838 The @sc{gnu} binary utilities (Binutils) package includes the
18839 @samp{objcopy} utility that can produce
18840 the separated executable / debugging information file pairs using the
18841 following commands:
18844 @kbd{objcopy --only-keep-debug foo foo.debug}
18849 These commands remove the debugging
18850 information from the executable file @file{foo} and place it in the file
18851 @file{foo.debug}. You can use the first, second or both methods to link the
18856 The debug link method needs the following additional command to also leave
18857 behind a debug link in @file{foo}:
18860 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18863 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18864 a version of the @code{strip} command such that the command @kbd{strip foo -f
18865 foo.debug} has the same functionality as the two @code{objcopy} commands and
18866 the @code{ln -s} command above, together.
18869 Build ID gets embedded into the main executable using @code{ld --build-id} or
18870 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18871 compatibility fixes for debug files separation are present in @sc{gnu} binary
18872 utilities (Binutils) package since version 2.18.
18877 @cindex CRC algorithm definition
18878 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18879 IEEE 802.3 using the polynomial:
18881 @c TexInfo requires naked braces for multi-digit exponents for Tex
18882 @c output, but this causes HTML output to barf. HTML has to be set using
18883 @c raw commands. So we end up having to specify this equation in 2
18888 <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>
18889 + <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
18895 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18896 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18900 The function is computed byte at a time, taking the least
18901 significant bit of each byte first. The initial pattern
18902 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18903 the final result is inverted to ensure trailing zeros also affect the
18906 @emph{Note:} This is the same CRC polynomial as used in handling the
18907 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18908 However in the case of the Remote Serial Protocol, the CRC is computed
18909 @emph{most} significant bit first, and the result is not inverted, so
18910 trailing zeros have no effect on the CRC value.
18912 To complete the description, we show below the code of the function
18913 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18914 initially supplied @code{crc} argument means that an initial call to
18915 this function passing in zero will start computing the CRC using
18918 @kindex gnu_debuglink_crc32
18921 gnu_debuglink_crc32 (unsigned long crc,
18922 unsigned char *buf, size_t len)
18924 static const unsigned long crc32_table[256] =
18926 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18927 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18928 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18929 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18930 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18931 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18932 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18933 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18934 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18935 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18936 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18937 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18938 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18939 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18940 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18941 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18942 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18943 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18944 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18945 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18946 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18947 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18948 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18949 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18950 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18951 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18952 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18953 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18954 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18955 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18956 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18957 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18958 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18959 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18960 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18961 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18962 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18963 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18964 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18965 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18966 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18967 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18968 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18969 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18970 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18971 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18972 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18973 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18974 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18975 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18976 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18979 unsigned char *end;
18981 crc = ~crc & 0xffffffff;
18982 for (end = buf + len; buf < end; ++buf)
18983 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18984 return ~crc & 0xffffffff;
18989 This computation does not apply to the ``build ID'' method.
18991 @node MiniDebugInfo
18992 @section Debugging information in a special section
18993 @cindex separate debug sections
18994 @cindex @samp{.gnu_debugdata} section
18996 Some systems ship pre-built executables and libraries that have a
18997 special @samp{.gnu_debugdata} section. This feature is called
18998 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18999 is used to supply extra symbols for backtraces.
19001 The intent of this section is to provide extra minimal debugging
19002 information for use in simple backtraces. It is not intended to be a
19003 replacement for full separate debugging information (@pxref{Separate
19004 Debug Files}). The example below shows the intended use; however,
19005 @value{GDBN} does not currently put restrictions on what sort of
19006 debugging information might be included in the section.
19008 @value{GDBN} has support for this extension. If the section exists,
19009 then it is used provided that no other source of debugging information
19010 can be found, and that @value{GDBN} was configured with LZMA support.
19012 This section can be easily created using @command{objcopy} and other
19013 standard utilities:
19016 # Extract the dynamic symbols from the main binary, there is no need
19017 # to also have these in the normal symbol table.
19018 nm -D @var{binary} --format=posix --defined-only \
19019 | awk '@{ print $1 @}' | sort > dynsyms
19021 # Extract all the text (i.e. function) symbols from the debuginfo.
19022 # (Note that we actually also accept "D" symbols, for the benefit
19023 # of platforms like PowerPC64 that use function descriptors.)
19024 nm @var{binary} --format=posix --defined-only \
19025 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19028 # Keep all the function symbols not already in the dynamic symbol
19030 comm -13 dynsyms funcsyms > keep_symbols
19032 # Separate full debug info into debug binary.
19033 objcopy --only-keep-debug @var{binary} debug
19035 # Copy the full debuginfo, keeping only a minimal set of symbols and
19036 # removing some unnecessary sections.
19037 objcopy -S --remove-section .gdb_index --remove-section .comment \
19038 --keep-symbols=keep_symbols debug mini_debuginfo
19040 # Drop the full debug info from the original binary.
19041 strip --strip-all -R .comment @var{binary}
19043 # Inject the compressed data into the .gnu_debugdata section of the
19046 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19050 @section Index Files Speed Up @value{GDBN}
19051 @cindex index files
19052 @cindex @samp{.gdb_index} section
19054 When @value{GDBN} finds a symbol file, it scans the symbols in the
19055 file in order to construct an internal symbol table. This lets most
19056 @value{GDBN} operations work quickly---at the cost of a delay early
19057 on. For large programs, this delay can be quite lengthy, so
19058 @value{GDBN} provides a way to build an index, which speeds up
19061 The index is stored as a section in the symbol file. @value{GDBN} can
19062 write the index to a file, then you can put it into the symbol file
19063 using @command{objcopy}.
19065 To create an index file, use the @code{save gdb-index} command:
19068 @item save gdb-index @var{directory}
19069 @kindex save gdb-index
19070 Create an index file for each symbol file currently known by
19071 @value{GDBN}. Each file is named after its corresponding symbol file,
19072 with @samp{.gdb-index} appended, and is written into the given
19076 Once you have created an index file you can merge it into your symbol
19077 file, here named @file{symfile}, using @command{objcopy}:
19080 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19081 --set-section-flags .gdb_index=readonly symfile symfile
19084 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19085 sections that have been deprecated. Usually they are deprecated because
19086 they are missing a new feature or have performance issues.
19087 To tell @value{GDBN} to use a deprecated index section anyway
19088 specify @code{set use-deprecated-index-sections on}.
19089 The default is @code{off}.
19090 This can speed up startup, but may result in some functionality being lost.
19091 @xref{Index Section Format}.
19093 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19094 must be done before gdb reads the file. The following will not work:
19097 $ gdb -ex "set use-deprecated-index-sections on" <program>
19100 Instead you must do, for example,
19103 $ gdb -iex "set use-deprecated-index-sections on" <program>
19106 There are currently some limitation on indices. They only work when
19107 for DWARF debugging information, not stabs. And, they do not
19108 currently work for programs using Ada.
19110 @node Symbol Errors
19111 @section Errors Reading Symbol Files
19113 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19114 such as symbol types it does not recognize, or known bugs in compiler
19115 output. By default, @value{GDBN} does not notify you of such problems, since
19116 they are relatively common and primarily of interest to people
19117 debugging compilers. If you are interested in seeing information
19118 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19119 only one message about each such type of problem, no matter how many
19120 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19121 to see how many times the problems occur, with the @code{set
19122 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19125 The messages currently printed, and their meanings, include:
19128 @item inner block not inside outer block in @var{symbol}
19130 The symbol information shows where symbol scopes begin and end
19131 (such as at the start of a function or a block of statements). This
19132 error indicates that an inner scope block is not fully contained
19133 in its outer scope blocks.
19135 @value{GDBN} circumvents the problem by treating the inner block as if it had
19136 the same scope as the outer block. In the error message, @var{symbol}
19137 may be shown as ``@code{(don't know)}'' if the outer block is not a
19140 @item block at @var{address} out of order
19142 The symbol information for symbol scope blocks should occur in
19143 order of increasing addresses. This error indicates that it does not
19146 @value{GDBN} does not circumvent this problem, and has trouble
19147 locating symbols in the source file whose symbols it is reading. (You
19148 can often determine what source file is affected by specifying
19149 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19152 @item bad block start address patched
19154 The symbol information for a symbol scope block has a start address
19155 smaller than the address of the preceding source line. This is known
19156 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19158 @value{GDBN} circumvents the problem by treating the symbol scope block as
19159 starting on the previous source line.
19161 @item bad string table offset in symbol @var{n}
19164 Symbol number @var{n} contains a pointer into the string table which is
19165 larger than the size of the string table.
19167 @value{GDBN} circumvents the problem by considering the symbol to have the
19168 name @code{foo}, which may cause other problems if many symbols end up
19171 @item unknown symbol type @code{0x@var{nn}}
19173 The symbol information contains new data types that @value{GDBN} does
19174 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19175 uncomprehended information, in hexadecimal.
19177 @value{GDBN} circumvents the error by ignoring this symbol information.
19178 This usually allows you to debug your program, though certain symbols
19179 are not accessible. If you encounter such a problem and feel like
19180 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19181 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19182 and examine @code{*bufp} to see the symbol.
19184 @item stub type has NULL name
19186 @value{GDBN} could not find the full definition for a struct or class.
19188 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19189 The symbol information for a C@t{++} member function is missing some
19190 information that recent versions of the compiler should have output for
19193 @item info mismatch between compiler and debugger
19195 @value{GDBN} could not parse a type specification output by the compiler.
19200 @section GDB Data Files
19202 @cindex prefix for data files
19203 @value{GDBN} will sometimes read an auxiliary data file. These files
19204 are kept in a directory known as the @dfn{data directory}.
19206 You can set the data directory's name, and view the name @value{GDBN}
19207 is currently using.
19210 @kindex set data-directory
19211 @item set data-directory @var{directory}
19212 Set the directory which @value{GDBN} searches for auxiliary data files
19213 to @var{directory}.
19215 @kindex show data-directory
19216 @item show data-directory
19217 Show the directory @value{GDBN} searches for auxiliary data files.
19220 @cindex default data directory
19221 @cindex @samp{--with-gdb-datadir}
19222 You can set the default data directory by using the configure-time
19223 @samp{--with-gdb-datadir} option. If the data directory is inside
19224 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19225 @samp{--exec-prefix}), then the default data directory will be updated
19226 automatically if the installed @value{GDBN} is moved to a new
19229 The data directory may also be specified with the
19230 @code{--data-directory} command line option.
19231 @xref{Mode Options}.
19234 @chapter Specifying a Debugging Target
19236 @cindex debugging target
19237 A @dfn{target} is the execution environment occupied by your program.
19239 Often, @value{GDBN} runs in the same host environment as your program;
19240 in that case, the debugging target is specified as a side effect when
19241 you use the @code{file} or @code{core} commands. When you need more
19242 flexibility---for example, running @value{GDBN} on a physically separate
19243 host, or controlling a standalone system over a serial port or a
19244 realtime system over a TCP/IP connection---you can use the @code{target}
19245 command to specify one of the target types configured for @value{GDBN}
19246 (@pxref{Target Commands, ,Commands for Managing Targets}).
19248 @cindex target architecture
19249 It is possible to build @value{GDBN} for several different @dfn{target
19250 architectures}. When @value{GDBN} is built like that, you can choose
19251 one of the available architectures with the @kbd{set architecture}
19255 @kindex set architecture
19256 @kindex show architecture
19257 @item set architecture @var{arch}
19258 This command sets the current target architecture to @var{arch}. The
19259 value of @var{arch} can be @code{"auto"}, in addition to one of the
19260 supported architectures.
19262 @item show architecture
19263 Show the current target architecture.
19265 @item set processor
19267 @kindex set processor
19268 @kindex show processor
19269 These are alias commands for, respectively, @code{set architecture}
19270 and @code{show architecture}.
19274 * Active Targets:: Active targets
19275 * Target Commands:: Commands for managing targets
19276 * Byte Order:: Choosing target byte order
19279 @node Active Targets
19280 @section Active Targets
19282 @cindex stacking targets
19283 @cindex active targets
19284 @cindex multiple targets
19286 There are multiple classes of targets such as: processes, executable files or
19287 recording sessions. Core files belong to the process class, making core file
19288 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19289 on multiple active targets, one in each class. This allows you to (for
19290 example) start a process and inspect its activity, while still having access to
19291 the executable file after the process finishes. Or if you start process
19292 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19293 presented a virtual layer of the recording target, while the process target
19294 remains stopped at the chronologically last point of the process execution.
19296 Use the @code{core-file} and @code{exec-file} commands to select a new core
19297 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19298 specify as a target a process that is already running, use the @code{attach}
19299 command (@pxref{Attach, ,Debugging an Already-running Process}).
19301 @node Target Commands
19302 @section Commands for Managing Targets
19305 @item target @var{type} @var{parameters}
19306 Connects the @value{GDBN} host environment to a target machine or
19307 process. A target is typically a protocol for talking to debugging
19308 facilities. You use the argument @var{type} to specify the type or
19309 protocol of the target machine.
19311 Further @var{parameters} are interpreted by the target protocol, but
19312 typically include things like device names or host names to connect
19313 with, process numbers, and baud rates.
19315 The @code{target} command does not repeat if you press @key{RET} again
19316 after executing the command.
19318 @kindex help target
19320 Displays the names of all targets available. To display targets
19321 currently selected, use either @code{info target} or @code{info files}
19322 (@pxref{Files, ,Commands to Specify Files}).
19324 @item help target @var{name}
19325 Describe a particular target, including any parameters necessary to
19328 @kindex set gnutarget
19329 @item set gnutarget @var{args}
19330 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19331 knows whether it is reading an @dfn{executable},
19332 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19333 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19334 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19337 @emph{Warning:} To specify a file format with @code{set gnutarget},
19338 you must know the actual BFD name.
19342 @xref{Files, , Commands to Specify Files}.
19344 @kindex show gnutarget
19345 @item show gnutarget
19346 Use the @code{show gnutarget} command to display what file format
19347 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19348 @value{GDBN} will determine the file format for each file automatically,
19349 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19352 @cindex common targets
19353 Here are some common targets (available, or not, depending on the GDB
19358 @item target exec @var{program}
19359 @cindex executable file target
19360 An executable file. @samp{target exec @var{program}} is the same as
19361 @samp{exec-file @var{program}}.
19363 @item target core @var{filename}
19364 @cindex core dump file target
19365 A core dump file. @samp{target core @var{filename}} is the same as
19366 @samp{core-file @var{filename}}.
19368 @item target remote @var{medium}
19369 @cindex remote target
19370 A remote system connected to @value{GDBN} via a serial line or network
19371 connection. This command tells @value{GDBN} to use its own remote
19372 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19374 For example, if you have a board connected to @file{/dev/ttya} on the
19375 machine running @value{GDBN}, you could say:
19378 target remote /dev/ttya
19381 @code{target remote} supports the @code{load} command. This is only
19382 useful if you have some other way of getting the stub to the target
19383 system, and you can put it somewhere in memory where it won't get
19384 clobbered by the download.
19386 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19387 @cindex built-in simulator target
19388 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19396 works; however, you cannot assume that a specific memory map, device
19397 drivers, or even basic I/O is available, although some simulators do
19398 provide these. For info about any processor-specific simulator details,
19399 see the appropriate section in @ref{Embedded Processors, ,Embedded
19402 @item target native
19403 @cindex native target
19404 Setup for local/native process debugging. Useful to make the
19405 @code{run} command spawn native processes (likewise @code{attach},
19406 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19407 (@pxref{set auto-connect-native-target}).
19411 Different targets are available on different configurations of @value{GDBN};
19412 your configuration may have more or fewer targets.
19414 Many remote targets require you to download the executable's code once
19415 you've successfully established a connection. You may wish to control
19416 various aspects of this process.
19421 @kindex set hash@r{, for remote monitors}
19422 @cindex hash mark while downloading
19423 This command controls whether a hash mark @samp{#} is displayed while
19424 downloading a file to the remote monitor. If on, a hash mark is
19425 displayed after each S-record is successfully downloaded to the
19429 @kindex show hash@r{, for remote monitors}
19430 Show the current status of displaying the hash mark.
19432 @item set debug monitor
19433 @kindex set debug monitor
19434 @cindex display remote monitor communications
19435 Enable or disable display of communications messages between
19436 @value{GDBN} and the remote monitor.
19438 @item show debug monitor
19439 @kindex show debug monitor
19440 Show the current status of displaying communications between
19441 @value{GDBN} and the remote monitor.
19446 @kindex load @var{filename}
19447 @item load @var{filename}
19449 Depending on what remote debugging facilities are configured into
19450 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19451 is meant to make @var{filename} (an executable) available for debugging
19452 on the remote system---by downloading, or dynamic linking, for example.
19453 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19454 the @code{add-symbol-file} command.
19456 If your @value{GDBN} does not have a @code{load} command, attempting to
19457 execute it gets the error message ``@code{You can't do that when your
19458 target is @dots{}}''
19460 The file is loaded at whatever address is specified in the executable.
19461 For some object file formats, you can specify the load address when you
19462 link the program; for other formats, like a.out, the object file format
19463 specifies a fixed address.
19464 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19466 Depending on the remote side capabilities, @value{GDBN} may be able to
19467 load programs into flash memory.
19469 @code{load} does not repeat if you press @key{RET} again after using it.
19473 @section Choosing Target Byte Order
19475 @cindex choosing target byte order
19476 @cindex target byte order
19478 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19479 offer the ability to run either big-endian or little-endian byte
19480 orders. Usually the executable or symbol will include a bit to
19481 designate the endian-ness, and you will not need to worry about
19482 which to use. However, you may still find it useful to adjust
19483 @value{GDBN}'s idea of processor endian-ness manually.
19487 @item set endian big
19488 Instruct @value{GDBN} to assume the target is big-endian.
19490 @item set endian little
19491 Instruct @value{GDBN} to assume the target is little-endian.
19493 @item set endian auto
19494 Instruct @value{GDBN} to use the byte order associated with the
19498 Display @value{GDBN}'s current idea of the target byte order.
19502 Note that these commands merely adjust interpretation of symbolic
19503 data on the host, and that they have absolutely no effect on the
19507 @node Remote Debugging
19508 @chapter Debugging Remote Programs
19509 @cindex remote debugging
19511 If you are trying to debug a program running on a machine that cannot run
19512 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19513 For example, you might use remote debugging on an operating system kernel,
19514 or on a small system which does not have a general purpose operating system
19515 powerful enough to run a full-featured debugger.
19517 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19518 to make this work with particular debugging targets. In addition,
19519 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19520 but not specific to any particular target system) which you can use if you
19521 write the remote stubs---the code that runs on the remote system to
19522 communicate with @value{GDBN}.
19524 Other remote targets may be available in your
19525 configuration of @value{GDBN}; use @code{help target} to list them.
19528 * Connecting:: Connecting to a remote target
19529 * File Transfer:: Sending files to a remote system
19530 * Server:: Using the gdbserver program
19531 * Remote Configuration:: Remote configuration
19532 * Remote Stub:: Implementing a remote stub
19536 @section Connecting to a Remote Target
19537 @cindex remote debugging, connecting
19538 @cindex @code{gdbserver}, connecting
19539 @cindex remote debugging, types of connections
19540 @cindex @code{gdbserver}, types of connections
19541 @cindex @code{gdbserver}, @code{target remote} mode
19542 @cindex @code{gdbserver}, @code{target extended-remote} mode
19544 This section describes how to connect to a remote target, including the
19545 types of connections and their differences, how to set up executable and
19546 symbol files on the host and target, and the commands used for
19547 connecting to and disconnecting from the remote target.
19549 @subsection Types of Remote Connections
19551 @value{GDBN} supports two types of remote connections, @code{target remote}
19552 mode and @code{target extended-remote} mode. Note that many remote targets
19553 support only @code{target remote} mode. There are several major
19554 differences between the two types of connections, enumerated here:
19558 @cindex remote debugging, detach and program exit
19559 @item Result of detach or program exit
19560 @strong{With target remote mode:} When the debugged program exits or you
19561 detach from it, @value{GDBN} disconnects from the target. When using
19562 @code{gdbserver}, @code{gdbserver} will exit.
19564 @strong{With target extended-remote mode:} When the debugged program exits or
19565 you detach from it, @value{GDBN} remains connected to the target, even
19566 though no program is running. You can rerun the program, attach to a
19567 running program, or use @code{monitor} commands specific to the target.
19569 When using @code{gdbserver} in this case, it does not exit unless it was
19570 invoked using the @option{--once} option. If the @option{--once} option
19571 was not used, you can ask @code{gdbserver} to exit using the
19572 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19574 @item Specifying the program to debug
19575 For both connection types you use the @code{file} command to specify the
19576 program on the host system. If you are using @code{gdbserver} there are
19577 some differences in how to specify the location of the program on the
19580 @strong{With target remote mode:} You must either specify the program to debug
19581 on the @code{gdbserver} command line or use the @option{--attach} option
19582 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19584 @cindex @option{--multi}, @code{gdbserver} option
19585 @strong{With target extended-remote mode:} You may specify the program to debug
19586 on the @code{gdbserver} command line, or you can load the program or attach
19587 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19589 @anchor{--multi Option in Types of Remote Connnections}
19590 You can start @code{gdbserver} without supplying an initial command to run
19591 or process ID to attach. To do this, use the @option{--multi} command line
19592 option. Then you can connect using @code{target extended-remote} and start
19593 the program you want to debug (see below for details on using the
19594 @code{run} command in this scenario). Note that the conditions under which
19595 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19596 (@code{target remote} or @code{target extended-remote}). The
19597 @option{--multi} option to @code{gdbserver} has no influence on that.
19599 @item The @code{run} command
19600 @strong{With target remote mode:} The @code{run} command is not
19601 supported. Once a connection has been established, you can use all
19602 the usual @value{GDBN} commands to examine and change data. The
19603 remote program is already running, so you can use commands like
19604 @kbd{step} and @kbd{continue}.
19606 @strong{With target extended-remote mode:} The @code{run} command is
19607 supported. The @code{run} command uses the value set by
19608 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19609 the program to run. Command line arguments are supported, except for
19610 wildcard expansion and I/O redirection (@pxref{Arguments}).
19612 If you specify the program to debug on the command line, then the
19613 @code{run} command is not required to start execution, and you can
19614 resume using commands like @kbd{step} and @kbd{continue} as with
19615 @code{target remote} mode.
19617 @anchor{Attaching in Types of Remote Connections}
19619 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19620 not supported. To attach to a running program using @code{gdbserver}, you
19621 must use the @option{--attach} option (@pxref{Running gdbserver}).
19623 @strong{With target extended-remote mode:} To attach to a running program,
19624 you may use the @code{attach} command after the connection has been
19625 established. If you are using @code{gdbserver}, you may also invoke
19626 @code{gdbserver} using the @option{--attach} option
19627 (@pxref{Running gdbserver}).
19631 @anchor{Host and target files}
19632 @subsection Host and Target Files
19633 @cindex remote debugging, symbol files
19634 @cindex symbol files, remote debugging
19636 @value{GDBN}, running on the host, needs access to symbol and debugging
19637 information for your program running on the target. This requires
19638 access to an unstripped copy of your program, and possibly any associated
19639 symbol files. Note that this section applies equally to both @code{target
19640 remote} mode and @code{target extended-remote} mode.
19642 Some remote targets (@pxref{qXfer executable filename read}, and
19643 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19644 the same connection used to communicate with @value{GDBN}. With such a
19645 target, if the remote program is unstripped, the only command you need is
19646 @code{target remote} (or @code{target extended-remote}).
19648 If the remote program is stripped, or the target does not support remote
19649 program file access, start up @value{GDBN} using the name of the local
19650 unstripped copy of your program as the first argument, or use the
19651 @code{file} command. Use @code{set sysroot} to specify the location (on
19652 the host) of target libraries (unless your @value{GDBN} was compiled with
19653 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19654 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19657 The symbol file and target libraries must exactly match the executable
19658 and libraries on the target, with one exception: the files on the host
19659 system should not be stripped, even if the files on the target system
19660 are. Mismatched or missing files will lead to confusing results
19661 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19662 files may also prevent @code{gdbserver} from debugging multi-threaded
19665 @subsection Remote Connection Commands
19666 @cindex remote connection commands
19667 @value{GDBN} can communicate with the target over a serial line, or
19668 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19669 each case, @value{GDBN} uses the same protocol for debugging your
19670 program; only the medium carrying the debugging packets varies. The
19671 @code{target remote} and @code{target extended-remote} commands
19672 establish a connection to the target. Both commands accept the same
19673 arguments, which indicate the medium to use:
19677 @item target remote @var{serial-device}
19678 @itemx target extended-remote @var{serial-device}
19679 @cindex serial line, @code{target remote}
19680 Use @var{serial-device} to communicate with the target. For example,
19681 to use a serial line connected to the device named @file{/dev/ttyb}:
19684 target remote /dev/ttyb
19687 If you're using a serial line, you may want to give @value{GDBN} the
19688 @samp{--baud} option, or use the @code{set serial baud} command
19689 (@pxref{Remote Configuration, set serial baud}) before the
19690 @code{target} command.
19692 @item target remote @code{@var{host}:@var{port}}
19693 @itemx target remote @code{tcp:@var{host}:@var{port}}
19694 @itemx target extended-remote @code{@var{host}:@var{port}}
19695 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19696 @cindex @acronym{TCP} port, @code{target remote}
19697 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19698 The @var{host} may be either a host name or a numeric @acronym{IP}
19699 address; @var{port} must be a decimal number. The @var{host} could be
19700 the target machine itself, if it is directly connected to the net, or
19701 it might be a terminal server which in turn has a serial line to the
19704 For example, to connect to port 2828 on a terminal server named
19708 target remote manyfarms:2828
19711 If your remote target is actually running on the same machine as your
19712 debugger session (e.g.@: a simulator for your target running on the
19713 same host), you can omit the hostname. For example, to connect to
19714 port 1234 on your local machine:
19717 target remote :1234
19721 Note that the colon is still required here.
19723 @item target remote @code{udp:@var{host}:@var{port}}
19724 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19725 @cindex @acronym{UDP} port, @code{target remote}
19726 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19727 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19730 target remote udp:manyfarms:2828
19733 When using a @acronym{UDP} connection for remote debugging, you should
19734 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19735 can silently drop packets on busy or unreliable networks, which will
19736 cause havoc with your debugging session.
19738 @item target remote | @var{command}
19739 @itemx target extended-remote | @var{command}
19740 @cindex pipe, @code{target remote} to
19741 Run @var{command} in the background and communicate with it using a
19742 pipe. The @var{command} is a shell command, to be parsed and expanded
19743 by the system's command shell, @code{/bin/sh}; it should expect remote
19744 protocol packets on its standard input, and send replies on its
19745 standard output. You could use this to run a stand-alone simulator
19746 that speaks the remote debugging protocol, to make net connections
19747 using programs like @code{ssh}, or for other similar tricks.
19749 If @var{command} closes its standard output (perhaps by exiting),
19750 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19751 program has already exited, this will have no effect.)
19755 @cindex interrupting remote programs
19756 @cindex remote programs, interrupting
19757 Whenever @value{GDBN} is waiting for the remote program, if you type the
19758 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19759 program. This may or may not succeed, depending in part on the hardware
19760 and the serial drivers the remote system uses. If you type the
19761 interrupt character once again, @value{GDBN} displays this prompt:
19764 Interrupted while waiting for the program.
19765 Give up (and stop debugging it)? (y or n)
19768 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19769 the remote debugging session. (If you decide you want to try again later,
19770 you can use @kbd{target remote} again to connect once more.) If you type
19771 @kbd{n}, @value{GDBN} goes back to waiting.
19773 In @code{target extended-remote} mode, typing @kbd{n} will leave
19774 @value{GDBN} connected to the target.
19777 @kindex detach (remote)
19779 When you have finished debugging the remote program, you can use the
19780 @code{detach} command to release it from @value{GDBN} control.
19781 Detaching from the target normally resumes its execution, but the results
19782 will depend on your particular remote stub. After the @code{detach}
19783 command in @code{target remote} mode, @value{GDBN} is free to connect to
19784 another target. In @code{target extended-remote} mode, @value{GDBN} is
19785 still connected to the target.
19789 The @code{disconnect} command closes the connection to the target, and
19790 the target is generally not resumed. It will wait for @value{GDBN}
19791 (this instance or another one) to connect and continue debugging. After
19792 the @code{disconnect} command, @value{GDBN} is again free to connect to
19795 @cindex send command to remote monitor
19796 @cindex extend @value{GDBN} for remote targets
19797 @cindex add new commands for external monitor
19799 @item monitor @var{cmd}
19800 This command allows you to send arbitrary commands directly to the
19801 remote monitor. Since @value{GDBN} doesn't care about the commands it
19802 sends like this, this command is the way to extend @value{GDBN}---you
19803 can add new commands that only the external monitor will understand
19807 @node File Transfer
19808 @section Sending files to a remote system
19809 @cindex remote target, file transfer
19810 @cindex file transfer
19811 @cindex sending files to remote systems
19813 Some remote targets offer the ability to transfer files over the same
19814 connection used to communicate with @value{GDBN}. This is convenient
19815 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19816 running @code{gdbserver} over a network interface. For other targets,
19817 e.g.@: embedded devices with only a single serial port, this may be
19818 the only way to upload or download files.
19820 Not all remote targets support these commands.
19824 @item remote put @var{hostfile} @var{targetfile}
19825 Copy file @var{hostfile} from the host system (the machine running
19826 @value{GDBN}) to @var{targetfile} on the target system.
19829 @item remote get @var{targetfile} @var{hostfile}
19830 Copy file @var{targetfile} from the target system to @var{hostfile}
19831 on the host system.
19833 @kindex remote delete
19834 @item remote delete @var{targetfile}
19835 Delete @var{targetfile} from the target system.
19840 @section Using the @code{gdbserver} Program
19843 @cindex remote connection without stubs
19844 @code{gdbserver} is a control program for Unix-like systems, which
19845 allows you to connect your program with a remote @value{GDBN} via
19846 @code{target remote} or @code{target extended-remote}---but without
19847 linking in the usual debugging stub.
19849 @code{gdbserver} is not a complete replacement for the debugging stubs,
19850 because it requires essentially the same operating-system facilities
19851 that @value{GDBN} itself does. In fact, a system that can run
19852 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19853 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19854 because it is a much smaller program than @value{GDBN} itself. It is
19855 also easier to port than all of @value{GDBN}, so you may be able to get
19856 started more quickly on a new system by using @code{gdbserver}.
19857 Finally, if you develop code for real-time systems, you may find that
19858 the tradeoffs involved in real-time operation make it more convenient to
19859 do as much development work as possible on another system, for example
19860 by cross-compiling. You can use @code{gdbserver} to make a similar
19861 choice for debugging.
19863 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19864 or a TCP connection, using the standard @value{GDBN} remote serial
19868 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19869 Do not run @code{gdbserver} connected to any public network; a
19870 @value{GDBN} connection to @code{gdbserver} provides access to the
19871 target system with the same privileges as the user running
19875 @anchor{Running gdbserver}
19876 @subsection Running @code{gdbserver}
19877 @cindex arguments, to @code{gdbserver}
19878 @cindex @code{gdbserver}, command-line arguments
19880 Run @code{gdbserver} on the target system. You need a copy of the
19881 program you want to debug, including any libraries it requires.
19882 @code{gdbserver} does not need your program's symbol table, so you can
19883 strip the program if necessary to save space. @value{GDBN} on the host
19884 system does all the symbol handling.
19886 To use the server, you must tell it how to communicate with @value{GDBN};
19887 the name of your program; and the arguments for your program. The usual
19891 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19894 @var{comm} is either a device name (to use a serial line), or a TCP
19895 hostname and portnumber, or @code{-} or @code{stdio} to use
19896 stdin/stdout of @code{gdbserver}.
19897 For example, to debug Emacs with the argument
19898 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19902 target> gdbserver /dev/com1 emacs foo.txt
19905 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19908 To use a TCP connection instead of a serial line:
19911 target> gdbserver host:2345 emacs foo.txt
19914 The only difference from the previous example is the first argument,
19915 specifying that you are communicating with the host @value{GDBN} via
19916 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19917 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19918 (Currently, the @samp{host} part is ignored.) You can choose any number
19919 you want for the port number as long as it does not conflict with any
19920 TCP ports already in use on the target system (for example, @code{23} is
19921 reserved for @code{telnet}).@footnote{If you choose a port number that
19922 conflicts with another service, @code{gdbserver} prints an error message
19923 and exits.} You must use the same port number with the host @value{GDBN}
19924 @code{target remote} command.
19926 The @code{stdio} connection is useful when starting @code{gdbserver}
19930 (gdb) target remote | ssh -T hostname gdbserver - hello
19933 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19934 and we don't want escape-character handling. Ssh does this by default when
19935 a command is provided, the flag is provided to make it explicit.
19936 You could elide it if you want to.
19938 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19939 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19940 display through a pipe connected to gdbserver.
19941 Both @code{stdout} and @code{stderr} use the same pipe.
19943 @anchor{Attaching to a program}
19944 @subsubsection Attaching to a Running Program
19945 @cindex attach to a program, @code{gdbserver}
19946 @cindex @option{--attach}, @code{gdbserver} option
19948 On some targets, @code{gdbserver} can also attach to running programs.
19949 This is accomplished via the @code{--attach} argument. The syntax is:
19952 target> gdbserver --attach @var{comm} @var{pid}
19955 @var{pid} is the process ID of a currently running process. It isn't
19956 necessary to point @code{gdbserver} at a binary for the running process.
19958 In @code{target extended-remote} mode, you can also attach using the
19959 @value{GDBN} attach command
19960 (@pxref{Attaching in Types of Remote Connections}).
19963 You can debug processes by name instead of process ID if your target has the
19964 @code{pidof} utility:
19967 target> gdbserver --attach @var{comm} `pidof @var{program}`
19970 In case more than one copy of @var{program} is running, or @var{program}
19971 has multiple threads, most versions of @code{pidof} support the
19972 @code{-s} option to only return the first process ID.
19974 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19976 This section applies only when @code{gdbserver} is run to listen on a TCP
19979 @code{gdbserver} normally terminates after all of its debugged processes have
19980 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19981 extended-remote}, @code{gdbserver} stays running even with no processes left.
19982 @value{GDBN} normally terminates the spawned debugged process on its exit,
19983 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19984 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19985 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19986 stays running even in the @kbd{target remote} mode.
19988 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19989 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19990 completeness, at most one @value{GDBN} can be connected at a time.
19992 @cindex @option{--once}, @code{gdbserver} option
19993 By default, @code{gdbserver} keeps the listening TCP port open, so that
19994 subsequent connections are possible. However, if you start @code{gdbserver}
19995 with the @option{--once} option, it will stop listening for any further
19996 connection attempts after connecting to the first @value{GDBN} session. This
19997 means no further connections to @code{gdbserver} will be possible after the
19998 first one. It also means @code{gdbserver} will terminate after the first
19999 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20000 connections and even in the @kbd{target extended-remote} mode. The
20001 @option{--once} option allows reusing the same port number for connecting to
20002 multiple instances of @code{gdbserver} running on the same host, since each
20003 instance closes its port after the first connection.
20005 @anchor{Other Command-Line Arguments for gdbserver}
20006 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20008 You can use the @option{--multi} option to start @code{gdbserver} without
20009 specifying a program to debug or a process to attach to. Then you can
20010 attach in @code{target extended-remote} mode and run or attach to a
20011 program. For more information,
20012 @pxref{--multi Option in Types of Remote Connnections}.
20014 @cindex @option{--debug}, @code{gdbserver} option
20015 The @option{--debug} option tells @code{gdbserver} to display extra
20016 status information about the debugging process.
20017 @cindex @option{--remote-debug}, @code{gdbserver} option
20018 The @option{--remote-debug} option tells @code{gdbserver} to display
20019 remote protocol debug output. These options are intended for
20020 @code{gdbserver} development and for bug reports to the developers.
20022 @cindex @option{--debug-format}, @code{gdbserver} option
20023 The @option{--debug-format=option1[,option2,...]} option tells
20024 @code{gdbserver} to include additional information in each output.
20025 Possible options are:
20029 Turn off all extra information in debugging output.
20031 Turn on all extra information in debugging output.
20033 Include a timestamp in each line of debugging output.
20036 Options are processed in order. Thus, for example, if @option{none}
20037 appears last then no additional information is added to debugging output.
20039 @cindex @option{--wrapper}, @code{gdbserver} option
20040 The @option{--wrapper} option specifies a wrapper to launch programs
20041 for debugging. The option should be followed by the name of the
20042 wrapper, then any command-line arguments to pass to the wrapper, then
20043 @kbd{--} indicating the end of the wrapper arguments.
20045 @code{gdbserver} runs the specified wrapper program with a combined
20046 command line including the wrapper arguments, then the name of the
20047 program to debug, then any arguments to the program. The wrapper
20048 runs until it executes your program, and then @value{GDBN} gains control.
20050 You can use any program that eventually calls @code{execve} with
20051 its arguments as a wrapper. Several standard Unix utilities do
20052 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20053 with @code{exec "$@@"} will also work.
20055 For example, you can use @code{env} to pass an environment variable to
20056 the debugged program, without setting the variable in @code{gdbserver}'s
20060 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20063 @subsection Connecting to @code{gdbserver}
20065 The basic procedure for connecting to the remote target is:
20069 Run @value{GDBN} on the host system.
20072 Make sure you have the necessary symbol files
20073 (@pxref{Host and target files}).
20074 Load symbols for your application using the @code{file} command before you
20075 connect. Use @code{set sysroot} to locate target libraries (unless your
20076 @value{GDBN} was compiled with the correct sysroot using
20077 @code{--with-sysroot}).
20080 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20081 For TCP connections, you must start up @code{gdbserver} prior to using
20082 the @code{target} command. Otherwise you may get an error whose
20083 text depends on the host system, but which usually looks something like
20084 @samp{Connection refused}. Don't use the @code{load}
20085 command in @value{GDBN} when using @code{target remote} mode, since the
20086 program is already on the target.
20090 @anchor{Monitor Commands for gdbserver}
20091 @subsection Monitor Commands for @code{gdbserver}
20092 @cindex monitor commands, for @code{gdbserver}
20094 During a @value{GDBN} session using @code{gdbserver}, you can use the
20095 @code{monitor} command to send special requests to @code{gdbserver}.
20096 Here are the available commands.
20100 List the available monitor commands.
20102 @item monitor set debug 0
20103 @itemx monitor set debug 1
20104 Disable or enable general debugging messages.
20106 @item monitor set remote-debug 0
20107 @itemx monitor set remote-debug 1
20108 Disable or enable specific debugging messages associated with the remote
20109 protocol (@pxref{Remote Protocol}).
20111 @item monitor set debug-format option1@r{[},option2,...@r{]}
20112 Specify additional text to add to debugging messages.
20113 Possible options are:
20117 Turn off all extra information in debugging output.
20119 Turn on all extra information in debugging output.
20121 Include a timestamp in each line of debugging output.
20124 Options are processed in order. Thus, for example, if @option{none}
20125 appears last then no additional information is added to debugging output.
20127 @item monitor set libthread-db-search-path [PATH]
20128 @cindex gdbserver, search path for @code{libthread_db}
20129 When this command is issued, @var{path} is a colon-separated list of
20130 directories to search for @code{libthread_db} (@pxref{Threads,,set
20131 libthread-db-search-path}). If you omit @var{path},
20132 @samp{libthread-db-search-path} will be reset to its default value.
20134 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20135 not supported in @code{gdbserver}.
20138 Tell gdbserver to exit immediately. This command should be followed by
20139 @code{disconnect} to close the debugging session. @code{gdbserver} will
20140 detach from any attached processes and kill any processes it created.
20141 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20142 of a multi-process mode debug session.
20146 @subsection Tracepoints support in @code{gdbserver}
20147 @cindex tracepoints support in @code{gdbserver}
20149 On some targets, @code{gdbserver} supports tracepoints, fast
20150 tracepoints and static tracepoints.
20152 For fast or static tracepoints to work, a special library called the
20153 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20154 This library is built and distributed as an integral part of
20155 @code{gdbserver}. In addition, support for static tracepoints
20156 requires building the in-process agent library with static tracepoints
20157 support. At present, the UST (LTTng Userspace Tracer,
20158 @url{http://lttng.org/ust}) tracing engine is supported. This support
20159 is automatically available if UST development headers are found in the
20160 standard include path when @code{gdbserver} is built, or if
20161 @code{gdbserver} was explicitly configured using @option{--with-ust}
20162 to point at such headers. You can explicitly disable the support
20163 using @option{--with-ust=no}.
20165 There are several ways to load the in-process agent in your program:
20168 @item Specifying it as dependency at link time
20170 You can link your program dynamically with the in-process agent
20171 library. On most systems, this is accomplished by adding
20172 @code{-linproctrace} to the link command.
20174 @item Using the system's preloading mechanisms
20176 You can force loading the in-process agent at startup time by using
20177 your system's support for preloading shared libraries. Many Unixes
20178 support the concept of preloading user defined libraries. In most
20179 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20180 in the environment. See also the description of @code{gdbserver}'s
20181 @option{--wrapper} command line option.
20183 @item Using @value{GDBN} to force loading the agent at run time
20185 On some systems, you can force the inferior to load a shared library,
20186 by calling a dynamic loader function in the inferior that takes care
20187 of dynamically looking up and loading a shared library. On most Unix
20188 systems, the function is @code{dlopen}. You'll use the @code{call}
20189 command for that. For example:
20192 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20195 Note that on most Unix systems, for the @code{dlopen} function to be
20196 available, the program needs to be linked with @code{-ldl}.
20199 On systems that have a userspace dynamic loader, like most Unix
20200 systems, when you connect to @code{gdbserver} using @code{target
20201 remote}, you'll find that the program is stopped at the dynamic
20202 loader's entry point, and no shared library has been loaded in the
20203 program's address space yet, including the in-process agent. In that
20204 case, before being able to use any of the fast or static tracepoints
20205 features, you need to let the loader run and load the shared
20206 libraries. The simplest way to do that is to run the program to the
20207 main procedure. E.g., if debugging a C or C@t{++} program, start
20208 @code{gdbserver} like so:
20211 $ gdbserver :9999 myprogram
20214 Start GDB and connect to @code{gdbserver} like so, and run to main:
20218 (@value{GDBP}) target remote myhost:9999
20219 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20220 (@value{GDBP}) b main
20221 (@value{GDBP}) continue
20224 The in-process tracing agent library should now be loaded into the
20225 process; you can confirm it with the @code{info sharedlibrary}
20226 command, which will list @file{libinproctrace.so} as loaded in the
20227 process. You are now ready to install fast tracepoints, list static
20228 tracepoint markers, probe static tracepoints markers, and start
20231 @node Remote Configuration
20232 @section Remote Configuration
20235 @kindex show remote
20236 This section documents the configuration options available when
20237 debugging remote programs. For the options related to the File I/O
20238 extensions of the remote protocol, see @ref{system,
20239 system-call-allowed}.
20242 @item set remoteaddresssize @var{bits}
20243 @cindex address size for remote targets
20244 @cindex bits in remote address
20245 Set the maximum size of address in a memory packet to the specified
20246 number of bits. @value{GDBN} will mask off the address bits above
20247 that number, when it passes addresses to the remote target. The
20248 default value is the number of bits in the target's address.
20250 @item show remoteaddresssize
20251 Show the current value of remote address size in bits.
20253 @item set serial baud @var{n}
20254 @cindex baud rate for remote targets
20255 Set the baud rate for the remote serial I/O to @var{n} baud. The
20256 value is used to set the speed of the serial port used for debugging
20259 @item show serial baud
20260 Show the current speed of the remote connection.
20262 @item set serial parity @var{parity}
20263 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20264 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20266 @item show serial parity
20267 Show the current parity of the serial port.
20269 @item set remotebreak
20270 @cindex interrupt remote programs
20271 @cindex BREAK signal instead of Ctrl-C
20272 @anchor{set remotebreak}
20273 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20274 when you type @kbd{Ctrl-c} to interrupt the program running
20275 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20276 character instead. The default is off, since most remote systems
20277 expect to see @samp{Ctrl-C} as the interrupt signal.
20279 @item show remotebreak
20280 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20281 interrupt the remote program.
20283 @item set remoteflow on
20284 @itemx set remoteflow off
20285 @kindex set remoteflow
20286 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20287 on the serial port used to communicate to the remote target.
20289 @item show remoteflow
20290 @kindex show remoteflow
20291 Show the current setting of hardware flow control.
20293 @item set remotelogbase @var{base}
20294 Set the base (a.k.a.@: radix) of logging serial protocol
20295 communications to @var{base}. Supported values of @var{base} are:
20296 @code{ascii}, @code{octal}, and @code{hex}. The default is
20299 @item show remotelogbase
20300 Show the current setting of the radix for logging remote serial
20303 @item set remotelogfile @var{file}
20304 @cindex record serial communications on file
20305 Record remote serial communications on the named @var{file}. The
20306 default is not to record at all.
20308 @item show remotelogfile.
20309 Show the current setting of the file name on which to record the
20310 serial communications.
20312 @item set remotetimeout @var{num}
20313 @cindex timeout for serial communications
20314 @cindex remote timeout
20315 Set the timeout limit to wait for the remote target to respond to
20316 @var{num} seconds. The default is 2 seconds.
20318 @item show remotetimeout
20319 Show the current number of seconds to wait for the remote target
20322 @cindex limit hardware breakpoints and watchpoints
20323 @cindex remote target, limit break- and watchpoints
20324 @anchor{set remote hardware-watchpoint-limit}
20325 @anchor{set remote hardware-breakpoint-limit}
20326 @item set remote hardware-watchpoint-limit @var{limit}
20327 @itemx set remote hardware-breakpoint-limit @var{limit}
20328 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20329 watchpoints. A limit of -1, the default, is treated as unlimited.
20331 @cindex limit hardware watchpoints length
20332 @cindex remote target, limit watchpoints length
20333 @anchor{set remote hardware-watchpoint-length-limit}
20334 @item set remote hardware-watchpoint-length-limit @var{limit}
20335 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20336 a remote hardware watchpoint. A limit of -1, the default, is treated
20339 @item show remote hardware-watchpoint-length-limit
20340 Show the current limit (in bytes) of the maximum length of
20341 a remote hardware watchpoint.
20343 @item set remote exec-file @var{filename}
20344 @itemx show remote exec-file
20345 @anchor{set remote exec-file}
20346 @cindex executable file, for remote target
20347 Select the file used for @code{run} with @code{target
20348 extended-remote}. This should be set to a filename valid on the
20349 target system. If it is not set, the target will use a default
20350 filename (e.g.@: the last program run).
20352 @item set remote interrupt-sequence
20353 @cindex interrupt remote programs
20354 @cindex select Ctrl-C, BREAK or BREAK-g
20355 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20356 @samp{BREAK-g} as the
20357 sequence to the remote target in order to interrupt the execution.
20358 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20359 is high level of serial line for some certain time.
20360 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20361 It is @code{BREAK} signal followed by character @code{g}.
20363 @item show interrupt-sequence
20364 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20365 is sent by @value{GDBN} to interrupt the remote program.
20366 @code{BREAK-g} is BREAK signal followed by @code{g} and
20367 also known as Magic SysRq g.
20369 @item set remote interrupt-on-connect
20370 @cindex send interrupt-sequence on start
20371 Specify whether interrupt-sequence is sent to remote target when
20372 @value{GDBN} connects to it. This is mostly needed when you debug
20373 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20374 which is known as Magic SysRq g in order to connect @value{GDBN}.
20376 @item show interrupt-on-connect
20377 Show whether interrupt-sequence is sent
20378 to remote target when @value{GDBN} connects to it.
20382 @item set tcp auto-retry on
20383 @cindex auto-retry, for remote TCP target
20384 Enable auto-retry for remote TCP connections. This is useful if the remote
20385 debugging agent is launched in parallel with @value{GDBN}; there is a race
20386 condition because the agent may not become ready to accept the connection
20387 before @value{GDBN} attempts to connect. When auto-retry is
20388 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20389 to establish the connection using the timeout specified by
20390 @code{set tcp connect-timeout}.
20392 @item set tcp auto-retry off
20393 Do not auto-retry failed TCP connections.
20395 @item show tcp auto-retry
20396 Show the current auto-retry setting.
20398 @item set tcp connect-timeout @var{seconds}
20399 @itemx set tcp connect-timeout unlimited
20400 @cindex connection timeout, for remote TCP target
20401 @cindex timeout, for remote target connection
20402 Set the timeout for establishing a TCP connection to the remote target to
20403 @var{seconds}. The timeout affects both polling to retry failed connections
20404 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20405 that are merely slow to complete, and represents an approximate cumulative
20406 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20407 @value{GDBN} will keep attempting to establish a connection forever,
20408 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20410 @item show tcp connect-timeout
20411 Show the current connection timeout setting.
20414 @cindex remote packets, enabling and disabling
20415 The @value{GDBN} remote protocol autodetects the packets supported by
20416 your debugging stub. If you need to override the autodetection, you
20417 can use these commands to enable or disable individual packets. Each
20418 packet can be set to @samp{on} (the remote target supports this
20419 packet), @samp{off} (the remote target does not support this packet),
20420 or @samp{auto} (detect remote target support for this packet). They
20421 all default to @samp{auto}. For more information about each packet,
20422 see @ref{Remote Protocol}.
20424 During normal use, you should not have to use any of these commands.
20425 If you do, that may be a bug in your remote debugging stub, or a bug
20426 in @value{GDBN}. You may want to report the problem to the
20427 @value{GDBN} developers.
20429 For each packet @var{name}, the command to enable or disable the
20430 packet is @code{set remote @var{name}-packet}. The available settings
20433 @multitable @columnfractions 0.28 0.32 0.25
20436 @tab Related Features
20438 @item @code{fetch-register}
20440 @tab @code{info registers}
20442 @item @code{set-register}
20446 @item @code{binary-download}
20448 @tab @code{load}, @code{set}
20450 @item @code{read-aux-vector}
20451 @tab @code{qXfer:auxv:read}
20452 @tab @code{info auxv}
20454 @item @code{symbol-lookup}
20455 @tab @code{qSymbol}
20456 @tab Detecting multiple threads
20458 @item @code{attach}
20459 @tab @code{vAttach}
20462 @item @code{verbose-resume}
20464 @tab Stepping or resuming multiple threads
20470 @item @code{software-breakpoint}
20474 @item @code{hardware-breakpoint}
20478 @item @code{write-watchpoint}
20482 @item @code{read-watchpoint}
20486 @item @code{access-watchpoint}
20490 @item @code{pid-to-exec-file}
20491 @tab @code{qXfer:exec-file:read}
20492 @tab @code{attach}, @code{run}
20494 @item @code{target-features}
20495 @tab @code{qXfer:features:read}
20496 @tab @code{set architecture}
20498 @item @code{library-info}
20499 @tab @code{qXfer:libraries:read}
20500 @tab @code{info sharedlibrary}
20502 @item @code{memory-map}
20503 @tab @code{qXfer:memory-map:read}
20504 @tab @code{info mem}
20506 @item @code{read-sdata-object}
20507 @tab @code{qXfer:sdata:read}
20508 @tab @code{print $_sdata}
20510 @item @code{read-spu-object}
20511 @tab @code{qXfer:spu:read}
20512 @tab @code{info spu}
20514 @item @code{write-spu-object}
20515 @tab @code{qXfer:spu:write}
20516 @tab @code{info spu}
20518 @item @code{read-siginfo-object}
20519 @tab @code{qXfer:siginfo:read}
20520 @tab @code{print $_siginfo}
20522 @item @code{write-siginfo-object}
20523 @tab @code{qXfer:siginfo:write}
20524 @tab @code{set $_siginfo}
20526 @item @code{threads}
20527 @tab @code{qXfer:threads:read}
20528 @tab @code{info threads}
20530 @item @code{get-thread-local-@*storage-address}
20531 @tab @code{qGetTLSAddr}
20532 @tab Displaying @code{__thread} variables
20534 @item @code{get-thread-information-block-address}
20535 @tab @code{qGetTIBAddr}
20536 @tab Display MS-Windows Thread Information Block.
20538 @item @code{search-memory}
20539 @tab @code{qSearch:memory}
20542 @item @code{supported-packets}
20543 @tab @code{qSupported}
20544 @tab Remote communications parameters
20546 @item @code{catch-syscalls}
20547 @tab @code{QCatchSyscalls}
20548 @tab @code{catch syscall}
20550 @item @code{pass-signals}
20551 @tab @code{QPassSignals}
20552 @tab @code{handle @var{signal}}
20554 @item @code{program-signals}
20555 @tab @code{QProgramSignals}
20556 @tab @code{handle @var{signal}}
20558 @item @code{hostio-close-packet}
20559 @tab @code{vFile:close}
20560 @tab @code{remote get}, @code{remote put}
20562 @item @code{hostio-open-packet}
20563 @tab @code{vFile:open}
20564 @tab @code{remote get}, @code{remote put}
20566 @item @code{hostio-pread-packet}
20567 @tab @code{vFile:pread}
20568 @tab @code{remote get}, @code{remote put}
20570 @item @code{hostio-pwrite-packet}
20571 @tab @code{vFile:pwrite}
20572 @tab @code{remote get}, @code{remote put}
20574 @item @code{hostio-unlink-packet}
20575 @tab @code{vFile:unlink}
20576 @tab @code{remote delete}
20578 @item @code{hostio-readlink-packet}
20579 @tab @code{vFile:readlink}
20582 @item @code{hostio-fstat-packet}
20583 @tab @code{vFile:fstat}
20586 @item @code{hostio-setfs-packet}
20587 @tab @code{vFile:setfs}
20590 @item @code{noack-packet}
20591 @tab @code{QStartNoAckMode}
20592 @tab Packet acknowledgment
20594 @item @code{osdata}
20595 @tab @code{qXfer:osdata:read}
20596 @tab @code{info os}
20598 @item @code{query-attached}
20599 @tab @code{qAttached}
20600 @tab Querying remote process attach state.
20602 @item @code{trace-buffer-size}
20603 @tab @code{QTBuffer:size}
20604 @tab @code{set trace-buffer-size}
20606 @item @code{trace-status}
20607 @tab @code{qTStatus}
20608 @tab @code{tstatus}
20610 @item @code{traceframe-info}
20611 @tab @code{qXfer:traceframe-info:read}
20612 @tab Traceframe info
20614 @item @code{install-in-trace}
20615 @tab @code{InstallInTrace}
20616 @tab Install tracepoint in tracing
20618 @item @code{disable-randomization}
20619 @tab @code{QDisableRandomization}
20620 @tab @code{set disable-randomization}
20622 @item @code{conditional-breakpoints-packet}
20623 @tab @code{Z0 and Z1}
20624 @tab @code{Support for target-side breakpoint condition evaluation}
20626 @item @code{multiprocess-extensions}
20627 @tab @code{multiprocess extensions}
20628 @tab Debug multiple processes and remote process PID awareness
20630 @item @code{swbreak-feature}
20631 @tab @code{swbreak stop reason}
20634 @item @code{hwbreak-feature}
20635 @tab @code{hwbreak stop reason}
20638 @item @code{fork-event-feature}
20639 @tab @code{fork stop reason}
20642 @item @code{vfork-event-feature}
20643 @tab @code{vfork stop reason}
20646 @item @code{exec-event-feature}
20647 @tab @code{exec stop reason}
20650 @item @code{thread-events}
20651 @tab @code{QThreadEvents}
20652 @tab Tracking thread lifetime.
20654 @item @code{no-resumed-stop-reply}
20655 @tab @code{no resumed thread left stop reply}
20656 @tab Tracking thread lifetime.
20661 @section Implementing a Remote Stub
20663 @cindex debugging stub, example
20664 @cindex remote stub, example
20665 @cindex stub example, remote debugging
20666 The stub files provided with @value{GDBN} implement the target side of the
20667 communication protocol, and the @value{GDBN} side is implemented in the
20668 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20669 these subroutines to communicate, and ignore the details. (If you're
20670 implementing your own stub file, you can still ignore the details: start
20671 with one of the existing stub files. @file{sparc-stub.c} is the best
20672 organized, and therefore the easiest to read.)
20674 @cindex remote serial debugging, overview
20675 To debug a program running on another machine (the debugging
20676 @dfn{target} machine), you must first arrange for all the usual
20677 prerequisites for the program to run by itself. For example, for a C
20682 A startup routine to set up the C runtime environment; these usually
20683 have a name like @file{crt0}. The startup routine may be supplied by
20684 your hardware supplier, or you may have to write your own.
20687 A C subroutine library to support your program's
20688 subroutine calls, notably managing input and output.
20691 A way of getting your program to the other machine---for example, a
20692 download program. These are often supplied by the hardware
20693 manufacturer, but you may have to write your own from hardware
20697 The next step is to arrange for your program to use a serial port to
20698 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20699 machine). In general terms, the scheme looks like this:
20703 @value{GDBN} already understands how to use this protocol; when everything
20704 else is set up, you can simply use the @samp{target remote} command
20705 (@pxref{Targets,,Specifying a Debugging Target}).
20707 @item On the target,
20708 you must link with your program a few special-purpose subroutines that
20709 implement the @value{GDBN} remote serial protocol. The file containing these
20710 subroutines is called a @dfn{debugging stub}.
20712 On certain remote targets, you can use an auxiliary program
20713 @code{gdbserver} instead of linking a stub into your program.
20714 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20717 The debugging stub is specific to the architecture of the remote
20718 machine; for example, use @file{sparc-stub.c} to debug programs on
20721 @cindex remote serial stub list
20722 These working remote stubs are distributed with @value{GDBN}:
20727 @cindex @file{i386-stub.c}
20730 For Intel 386 and compatible architectures.
20733 @cindex @file{m68k-stub.c}
20734 @cindex Motorola 680x0
20736 For Motorola 680x0 architectures.
20739 @cindex @file{sh-stub.c}
20742 For Renesas SH architectures.
20745 @cindex @file{sparc-stub.c}
20747 For @sc{sparc} architectures.
20749 @item sparcl-stub.c
20750 @cindex @file{sparcl-stub.c}
20753 For Fujitsu @sc{sparclite} architectures.
20757 The @file{README} file in the @value{GDBN} distribution may list other
20758 recently added stubs.
20761 * Stub Contents:: What the stub can do for you
20762 * Bootstrapping:: What you must do for the stub
20763 * Debug Session:: Putting it all together
20766 @node Stub Contents
20767 @subsection What the Stub Can Do for You
20769 @cindex remote serial stub
20770 The debugging stub for your architecture supplies these three
20774 @item set_debug_traps
20775 @findex set_debug_traps
20776 @cindex remote serial stub, initialization
20777 This routine arranges for @code{handle_exception} to run when your
20778 program stops. You must call this subroutine explicitly in your
20779 program's startup code.
20781 @item handle_exception
20782 @findex handle_exception
20783 @cindex remote serial stub, main routine
20784 This is the central workhorse, but your program never calls it
20785 explicitly---the setup code arranges for @code{handle_exception} to
20786 run when a trap is triggered.
20788 @code{handle_exception} takes control when your program stops during
20789 execution (for example, on a breakpoint), and mediates communications
20790 with @value{GDBN} on the host machine. This is where the communications
20791 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20792 representative on the target machine. It begins by sending summary
20793 information on the state of your program, then continues to execute,
20794 retrieving and transmitting any information @value{GDBN} needs, until you
20795 execute a @value{GDBN} command that makes your program resume; at that point,
20796 @code{handle_exception} returns control to your own code on the target
20800 @cindex @code{breakpoint} subroutine, remote
20801 Use this auxiliary subroutine to make your program contain a
20802 breakpoint. Depending on the particular situation, this may be the only
20803 way for @value{GDBN} to get control. For instance, if your target
20804 machine has some sort of interrupt button, you won't need to call this;
20805 pressing the interrupt button transfers control to
20806 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20807 simply receiving characters on the serial port may also trigger a trap;
20808 again, in that situation, you don't need to call @code{breakpoint} from
20809 your own program---simply running @samp{target remote} from the host
20810 @value{GDBN} session gets control.
20812 Call @code{breakpoint} if none of these is true, or if you simply want
20813 to make certain your program stops at a predetermined point for the
20814 start of your debugging session.
20817 @node Bootstrapping
20818 @subsection What You Must Do for the Stub
20820 @cindex remote stub, support routines
20821 The debugging stubs that come with @value{GDBN} are set up for a particular
20822 chip architecture, but they have no information about the rest of your
20823 debugging target machine.
20825 First of all you need to tell the stub how to communicate with the
20829 @item int getDebugChar()
20830 @findex getDebugChar
20831 Write this subroutine to read a single character from the serial port.
20832 It may be identical to @code{getchar} for your target system; a
20833 different name is used to allow you to distinguish the two if you wish.
20835 @item void putDebugChar(int)
20836 @findex putDebugChar
20837 Write this subroutine to write a single character to the serial port.
20838 It may be identical to @code{putchar} for your target system; a
20839 different name is used to allow you to distinguish the two if you wish.
20842 @cindex control C, and remote debugging
20843 @cindex interrupting remote targets
20844 If you want @value{GDBN} to be able to stop your program while it is
20845 running, you need to use an interrupt-driven serial driver, and arrange
20846 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20847 character). That is the character which @value{GDBN} uses to tell the
20848 remote system to stop.
20850 Getting the debugging target to return the proper status to @value{GDBN}
20851 probably requires changes to the standard stub; one quick and dirty way
20852 is to just execute a breakpoint instruction (the ``dirty'' part is that
20853 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20855 Other routines you need to supply are:
20858 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20859 @findex exceptionHandler
20860 Write this function to install @var{exception_address} in the exception
20861 handling tables. You need to do this because the stub does not have any
20862 way of knowing what the exception handling tables on your target system
20863 are like (for example, the processor's table might be in @sc{rom},
20864 containing entries which point to a table in @sc{ram}).
20865 The @var{exception_number} specifies the exception which should be changed;
20866 its meaning is architecture-dependent (for example, different numbers
20867 might represent divide by zero, misaligned access, etc). When this
20868 exception occurs, control should be transferred directly to
20869 @var{exception_address}, and the processor state (stack, registers,
20870 and so on) should be just as it is when a processor exception occurs. So if
20871 you want to use a jump instruction to reach @var{exception_address}, it
20872 should be a simple jump, not a jump to subroutine.
20874 For the 386, @var{exception_address} should be installed as an interrupt
20875 gate so that interrupts are masked while the handler runs. The gate
20876 should be at privilege level 0 (the most privileged level). The
20877 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20878 help from @code{exceptionHandler}.
20880 @item void flush_i_cache()
20881 @findex flush_i_cache
20882 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20883 instruction cache, if any, on your target machine. If there is no
20884 instruction cache, this subroutine may be a no-op.
20886 On target machines that have instruction caches, @value{GDBN} requires this
20887 function to make certain that the state of your program is stable.
20891 You must also make sure this library routine is available:
20894 @item void *memset(void *, int, int)
20896 This is the standard library function @code{memset} that sets an area of
20897 memory to a known value. If you have one of the free versions of
20898 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20899 either obtain it from your hardware manufacturer, or write your own.
20902 If you do not use the GNU C compiler, you may need other standard
20903 library subroutines as well; this varies from one stub to another,
20904 but in general the stubs are likely to use any of the common library
20905 subroutines which @code{@value{NGCC}} generates as inline code.
20908 @node Debug Session
20909 @subsection Putting it All Together
20911 @cindex remote serial debugging summary
20912 In summary, when your program is ready to debug, you must follow these
20917 Make sure you have defined the supporting low-level routines
20918 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20920 @code{getDebugChar}, @code{putDebugChar},
20921 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20925 Insert these lines in your program's startup code, before the main
20926 procedure is called:
20933 On some machines, when a breakpoint trap is raised, the hardware
20934 automatically makes the PC point to the instruction after the
20935 breakpoint. If your machine doesn't do that, you may need to adjust
20936 @code{handle_exception} to arrange for it to return to the instruction
20937 after the breakpoint on this first invocation, so that your program
20938 doesn't keep hitting the initial breakpoint instead of making
20942 For the 680x0 stub only, you need to provide a variable called
20943 @code{exceptionHook}. Normally you just use:
20946 void (*exceptionHook)() = 0;
20950 but if before calling @code{set_debug_traps}, you set it to point to a
20951 function in your program, that function is called when
20952 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20953 error). The function indicated by @code{exceptionHook} is called with
20954 one parameter: an @code{int} which is the exception number.
20957 Compile and link together: your program, the @value{GDBN} debugging stub for
20958 your target architecture, and the supporting subroutines.
20961 Make sure you have a serial connection between your target machine and
20962 the @value{GDBN} host, and identify the serial port on the host.
20965 @c The "remote" target now provides a `load' command, so we should
20966 @c document that. FIXME.
20967 Download your program to your target machine (or get it there by
20968 whatever means the manufacturer provides), and start it.
20971 Start @value{GDBN} on the host, and connect to the target
20972 (@pxref{Connecting,,Connecting to a Remote Target}).
20976 @node Configurations
20977 @chapter Configuration-Specific Information
20979 While nearly all @value{GDBN} commands are available for all native and
20980 cross versions of the debugger, there are some exceptions. This chapter
20981 describes things that are only available in certain configurations.
20983 There are three major categories of configurations: native
20984 configurations, where the host and target are the same, embedded
20985 operating system configurations, which are usually the same for several
20986 different processor architectures, and bare embedded processors, which
20987 are quite different from each other.
20992 * Embedded Processors::
20999 This section describes details specific to particular native
21003 * BSD libkvm Interface:: Debugging BSD kernel memory images
21004 * SVR4 Process Information:: SVR4 process information
21005 * DJGPP Native:: Features specific to the DJGPP port
21006 * Cygwin Native:: Features specific to the Cygwin port
21007 * Hurd Native:: Features specific to @sc{gnu} Hurd
21008 * Darwin:: Features specific to Darwin
21011 @node BSD libkvm Interface
21012 @subsection BSD libkvm Interface
21015 @cindex kernel memory image
21016 @cindex kernel crash dump
21018 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21019 interface that provides a uniform interface for accessing kernel virtual
21020 memory images, including live systems and crash dumps. @value{GDBN}
21021 uses this interface to allow you to debug live kernels and kernel crash
21022 dumps on many native BSD configurations. This is implemented as a
21023 special @code{kvm} debugging target. For debugging a live system, load
21024 the currently running kernel into @value{GDBN} and connect to the
21028 (@value{GDBP}) @b{target kvm}
21031 For debugging crash dumps, provide the file name of the crash dump as an
21035 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21038 Once connected to the @code{kvm} target, the following commands are
21044 Set current context from the @dfn{Process Control Block} (PCB) address.
21047 Set current context from proc address. This command isn't available on
21048 modern FreeBSD systems.
21051 @node SVR4 Process Information
21052 @subsection SVR4 Process Information
21054 @cindex examine process image
21055 @cindex process info via @file{/proc}
21057 Many versions of SVR4 and compatible systems provide a facility called
21058 @samp{/proc} that can be used to examine the image of a running
21059 process using file-system subroutines.
21061 If @value{GDBN} is configured for an operating system with this
21062 facility, the command @code{info proc} is available to report
21063 information about the process running your program, or about any
21064 process running on your system. This includes, as of this writing,
21065 @sc{gnu}/Linux and Solaris, for example.
21067 This command may also work on core files that were created on a system
21068 that has the @samp{/proc} facility.
21074 @itemx info proc @var{process-id}
21075 Summarize available information about any running process. If a
21076 process ID is specified by @var{process-id}, display information about
21077 that process; otherwise display information about the program being
21078 debugged. The summary includes the debugged process ID, the command
21079 line used to invoke it, its current working directory, and its
21080 executable file's absolute file name.
21082 On some systems, @var{process-id} can be of the form
21083 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21084 within a process. If the optional @var{pid} part is missing, it means
21085 a thread from the process being debugged (the leading @samp{/} still
21086 needs to be present, or else @value{GDBN} will interpret the number as
21087 a process ID rather than a thread ID).
21089 @item info proc cmdline
21090 @cindex info proc cmdline
21091 Show the original command line of the process. This command is
21092 specific to @sc{gnu}/Linux.
21094 @item info proc cwd
21095 @cindex info proc cwd
21096 Show the current working directory of the process. This command is
21097 specific to @sc{gnu}/Linux.
21099 @item info proc exe
21100 @cindex info proc exe
21101 Show the name of executable of the process. This command is specific
21104 @item info proc mappings
21105 @cindex memory address space mappings
21106 Report the memory address space ranges accessible in the program, with
21107 information on whether the process has read, write, or execute access
21108 rights to each range. On @sc{gnu}/Linux systems, each memory range
21109 includes the object file which is mapped to that range, instead of the
21110 memory access rights to that range.
21112 @item info proc stat
21113 @itemx info proc status
21114 @cindex process detailed status information
21115 These subcommands are specific to @sc{gnu}/Linux systems. They show
21116 the process-related information, including the user ID and group ID;
21117 how many threads are there in the process; its virtual memory usage;
21118 the signals that are pending, blocked, and ignored; its TTY; its
21119 consumption of system and user time; its stack size; its @samp{nice}
21120 value; etc. For more information, see the @samp{proc} man page
21121 (type @kbd{man 5 proc} from your shell prompt).
21123 @item info proc all
21124 Show all the information about the process described under all of the
21125 above @code{info proc} subcommands.
21128 @comment These sub-options of 'info proc' were not included when
21129 @comment procfs.c was re-written. Keep their descriptions around
21130 @comment against the day when someone finds the time to put them back in.
21131 @kindex info proc times
21132 @item info proc times
21133 Starting time, user CPU time, and system CPU time for your program and
21136 @kindex info proc id
21138 Report on the process IDs related to your program: its own process ID,
21139 the ID of its parent, the process group ID, and the session ID.
21142 @item set procfs-trace
21143 @kindex set procfs-trace
21144 @cindex @code{procfs} API calls
21145 This command enables and disables tracing of @code{procfs} API calls.
21147 @item show procfs-trace
21148 @kindex show procfs-trace
21149 Show the current state of @code{procfs} API call tracing.
21151 @item set procfs-file @var{file}
21152 @kindex set procfs-file
21153 Tell @value{GDBN} to write @code{procfs} API trace to the named
21154 @var{file}. @value{GDBN} appends the trace info to the previous
21155 contents of the file. The default is to display the trace on the
21158 @item show procfs-file
21159 @kindex show procfs-file
21160 Show the file to which @code{procfs} API trace is written.
21162 @item proc-trace-entry
21163 @itemx proc-trace-exit
21164 @itemx proc-untrace-entry
21165 @itemx proc-untrace-exit
21166 @kindex proc-trace-entry
21167 @kindex proc-trace-exit
21168 @kindex proc-untrace-entry
21169 @kindex proc-untrace-exit
21170 These commands enable and disable tracing of entries into and exits
21171 from the @code{syscall} interface.
21174 @kindex info pidlist
21175 @cindex process list, QNX Neutrino
21176 For QNX Neutrino only, this command displays the list of all the
21177 processes and all the threads within each process.
21180 @kindex info meminfo
21181 @cindex mapinfo list, QNX Neutrino
21182 For QNX Neutrino only, this command displays the list of all mapinfos.
21186 @subsection Features for Debugging @sc{djgpp} Programs
21187 @cindex @sc{djgpp} debugging
21188 @cindex native @sc{djgpp} debugging
21189 @cindex MS-DOS-specific commands
21192 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21193 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21194 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21195 top of real-mode DOS systems and their emulations.
21197 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21198 defines a few commands specific to the @sc{djgpp} port. This
21199 subsection describes those commands.
21204 This is a prefix of @sc{djgpp}-specific commands which print
21205 information about the target system and important OS structures.
21208 @cindex MS-DOS system info
21209 @cindex free memory information (MS-DOS)
21210 @item info dos sysinfo
21211 This command displays assorted information about the underlying
21212 platform: the CPU type and features, the OS version and flavor, the
21213 DPMI version, and the available conventional and DPMI memory.
21218 @cindex segment descriptor tables
21219 @cindex descriptor tables display
21221 @itemx info dos ldt
21222 @itemx info dos idt
21223 These 3 commands display entries from, respectively, Global, Local,
21224 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21225 tables are data structures which store a descriptor for each segment
21226 that is currently in use. The segment's selector is an index into a
21227 descriptor table; the table entry for that index holds the
21228 descriptor's base address and limit, and its attributes and access
21231 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21232 segment (used for both data and the stack), and a DOS segment (which
21233 allows access to DOS/BIOS data structures and absolute addresses in
21234 conventional memory). However, the DPMI host will usually define
21235 additional segments in order to support the DPMI environment.
21237 @cindex garbled pointers
21238 These commands allow to display entries from the descriptor tables.
21239 Without an argument, all entries from the specified table are
21240 displayed. An argument, which should be an integer expression, means
21241 display a single entry whose index is given by the argument. For
21242 example, here's a convenient way to display information about the
21243 debugged program's data segment:
21246 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21247 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21251 This comes in handy when you want to see whether a pointer is outside
21252 the data segment's limit (i.e.@: @dfn{garbled}).
21254 @cindex page tables display (MS-DOS)
21256 @itemx info dos pte
21257 These two commands display entries from, respectively, the Page
21258 Directory and the Page Tables. Page Directories and Page Tables are
21259 data structures which control how virtual memory addresses are mapped
21260 into physical addresses. A Page Table includes an entry for every
21261 page of memory that is mapped into the program's address space; there
21262 may be several Page Tables, each one holding up to 4096 entries. A
21263 Page Directory has up to 4096 entries, one each for every Page Table
21264 that is currently in use.
21266 Without an argument, @kbd{info dos pde} displays the entire Page
21267 Directory, and @kbd{info dos pte} displays all the entries in all of
21268 the Page Tables. An argument, an integer expression, given to the
21269 @kbd{info dos pde} command means display only that entry from the Page
21270 Directory table. An argument given to the @kbd{info dos pte} command
21271 means display entries from a single Page Table, the one pointed to by
21272 the specified entry in the Page Directory.
21274 @cindex direct memory access (DMA) on MS-DOS
21275 These commands are useful when your program uses @dfn{DMA} (Direct
21276 Memory Access), which needs physical addresses to program the DMA
21279 These commands are supported only with some DPMI servers.
21281 @cindex physical address from linear address
21282 @item info dos address-pte @var{addr}
21283 This command displays the Page Table entry for a specified linear
21284 address. The argument @var{addr} is a linear address which should
21285 already have the appropriate segment's base address added to it,
21286 because this command accepts addresses which may belong to @emph{any}
21287 segment. For example, here's how to display the Page Table entry for
21288 the page where a variable @code{i} is stored:
21291 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21292 @exdent @code{Page Table entry for address 0x11a00d30:}
21293 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21297 This says that @code{i} is stored at offset @code{0xd30} from the page
21298 whose physical base address is @code{0x02698000}, and shows all the
21299 attributes of that page.
21301 Note that you must cast the addresses of variables to a @code{char *},
21302 since otherwise the value of @code{__djgpp_base_address}, the base
21303 address of all variables and functions in a @sc{djgpp} program, will
21304 be added using the rules of C pointer arithmetics: if @code{i} is
21305 declared an @code{int}, @value{GDBN} will add 4 times the value of
21306 @code{__djgpp_base_address} to the address of @code{i}.
21308 Here's another example, it displays the Page Table entry for the
21312 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21313 @exdent @code{Page Table entry for address 0x29110:}
21314 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21318 (The @code{+ 3} offset is because the transfer buffer's address is the
21319 3rd member of the @code{_go32_info_block} structure.) The output
21320 clearly shows that this DPMI server maps the addresses in conventional
21321 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21322 linear (@code{0x29110}) addresses are identical.
21324 This command is supported only with some DPMI servers.
21327 @cindex DOS serial data link, remote debugging
21328 In addition to native debugging, the DJGPP port supports remote
21329 debugging via a serial data link. The following commands are specific
21330 to remote serial debugging in the DJGPP port of @value{GDBN}.
21333 @kindex set com1base
21334 @kindex set com1irq
21335 @kindex set com2base
21336 @kindex set com2irq
21337 @kindex set com3base
21338 @kindex set com3irq
21339 @kindex set com4base
21340 @kindex set com4irq
21341 @item set com1base @var{addr}
21342 This command sets the base I/O port address of the @file{COM1} serial
21345 @item set com1irq @var{irq}
21346 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21347 for the @file{COM1} serial port.
21349 There are similar commands @samp{set com2base}, @samp{set com3irq},
21350 etc.@: for setting the port address and the @code{IRQ} lines for the
21353 @kindex show com1base
21354 @kindex show com1irq
21355 @kindex show com2base
21356 @kindex show com2irq
21357 @kindex show com3base
21358 @kindex show com3irq
21359 @kindex show com4base
21360 @kindex show com4irq
21361 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21362 display the current settings of the base address and the @code{IRQ}
21363 lines used by the COM ports.
21366 @kindex info serial
21367 @cindex DOS serial port status
21368 This command prints the status of the 4 DOS serial ports. For each
21369 port, it prints whether it's active or not, its I/O base address and
21370 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21371 counts of various errors encountered so far.
21375 @node Cygwin Native
21376 @subsection Features for Debugging MS Windows PE Executables
21377 @cindex MS Windows debugging
21378 @cindex native Cygwin debugging
21379 @cindex Cygwin-specific commands
21381 @value{GDBN} supports native debugging of MS Windows programs, including
21382 DLLs with and without symbolic debugging information.
21384 @cindex Ctrl-BREAK, MS-Windows
21385 @cindex interrupt debuggee on MS-Windows
21386 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21387 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21388 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21389 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21390 sequence, which can be used to interrupt the debuggee even if it
21393 There are various additional Cygwin-specific commands, described in
21394 this section. Working with DLLs that have no debugging symbols is
21395 described in @ref{Non-debug DLL Symbols}.
21400 This is a prefix of MS Windows-specific commands which print
21401 information about the target system and important OS structures.
21403 @item info w32 selector
21404 This command displays information returned by
21405 the Win32 API @code{GetThreadSelectorEntry} function.
21406 It takes an optional argument that is evaluated to
21407 a long value to give the information about this given selector.
21408 Without argument, this command displays information
21409 about the six segment registers.
21411 @item info w32 thread-information-block
21412 This command displays thread specific information stored in the
21413 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21414 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21416 @kindex set cygwin-exceptions
21417 @cindex debugging the Cygwin DLL
21418 @cindex Cygwin DLL, debugging
21419 @item set cygwin-exceptions @var{mode}
21420 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21421 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21422 @value{GDBN} will delay recognition of exceptions, and may ignore some
21423 exceptions which seem to be caused by internal Cygwin DLL
21424 ``bookkeeping''. This option is meant primarily for debugging the
21425 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21426 @value{GDBN} users with false @code{SIGSEGV} signals.
21428 @kindex show cygwin-exceptions
21429 @item show cygwin-exceptions
21430 Displays whether @value{GDBN} will break on exceptions that happen
21431 inside the Cygwin DLL itself.
21433 @kindex set new-console
21434 @item set new-console @var{mode}
21435 If @var{mode} is @code{on} the debuggee will
21436 be started in a new console on next start.
21437 If @var{mode} is @code{off}, the debuggee will
21438 be started in the same console as the debugger.
21440 @kindex show new-console
21441 @item show new-console
21442 Displays whether a new console is used
21443 when the debuggee is started.
21445 @kindex set new-group
21446 @item set new-group @var{mode}
21447 This boolean value controls whether the debuggee should
21448 start a new group or stay in the same group as the debugger.
21449 This affects the way the Windows OS handles
21452 @kindex show new-group
21453 @item show new-group
21454 Displays current value of new-group boolean.
21456 @kindex set debugevents
21457 @item set debugevents
21458 This boolean value adds debug output concerning kernel events related
21459 to the debuggee seen by the debugger. This includes events that
21460 signal thread and process creation and exit, DLL loading and
21461 unloading, console interrupts, and debugging messages produced by the
21462 Windows @code{OutputDebugString} API call.
21464 @kindex set debugexec
21465 @item set debugexec
21466 This boolean value adds debug output concerning execute events
21467 (such as resume thread) seen by the debugger.
21469 @kindex set debugexceptions
21470 @item set debugexceptions
21471 This boolean value adds debug output concerning exceptions in the
21472 debuggee seen by the debugger.
21474 @kindex set debugmemory
21475 @item set debugmemory
21476 This boolean value adds debug output concerning debuggee memory reads
21477 and writes by the debugger.
21481 This boolean values specifies whether the debuggee is called
21482 via a shell or directly (default value is on).
21486 Displays if the debuggee will be started with a shell.
21491 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21494 @node Non-debug DLL Symbols
21495 @subsubsection Support for DLLs without Debugging Symbols
21496 @cindex DLLs with no debugging symbols
21497 @cindex Minimal symbols and DLLs
21499 Very often on windows, some of the DLLs that your program relies on do
21500 not include symbolic debugging information (for example,
21501 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21502 symbols in a DLL, it relies on the minimal amount of symbolic
21503 information contained in the DLL's export table. This section
21504 describes working with such symbols, known internally to @value{GDBN} as
21505 ``minimal symbols''.
21507 Note that before the debugged program has started execution, no DLLs
21508 will have been loaded. The easiest way around this problem is simply to
21509 start the program --- either by setting a breakpoint or letting the
21510 program run once to completion.
21512 @subsubsection DLL Name Prefixes
21514 In keeping with the naming conventions used by the Microsoft debugging
21515 tools, DLL export symbols are made available with a prefix based on the
21516 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21517 also entered into the symbol table, so @code{CreateFileA} is often
21518 sufficient. In some cases there will be name clashes within a program
21519 (particularly if the executable itself includes full debugging symbols)
21520 necessitating the use of the fully qualified name when referring to the
21521 contents of the DLL. Use single-quotes around the name to avoid the
21522 exclamation mark (``!'') being interpreted as a language operator.
21524 Note that the internal name of the DLL may be all upper-case, even
21525 though the file name of the DLL is lower-case, or vice-versa. Since
21526 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21527 some confusion. If in doubt, try the @code{info functions} and
21528 @code{info variables} commands or even @code{maint print msymbols}
21529 (@pxref{Symbols}). Here's an example:
21532 (@value{GDBP}) info function CreateFileA
21533 All functions matching regular expression "CreateFileA":
21535 Non-debugging symbols:
21536 0x77e885f4 CreateFileA
21537 0x77e885f4 KERNEL32!CreateFileA
21541 (@value{GDBP}) info function !
21542 All functions matching regular expression "!":
21544 Non-debugging symbols:
21545 0x6100114c cygwin1!__assert
21546 0x61004034 cygwin1!_dll_crt0@@0
21547 0x61004240 cygwin1!dll_crt0(per_process *)
21551 @subsubsection Working with Minimal Symbols
21553 Symbols extracted from a DLL's export table do not contain very much
21554 type information. All that @value{GDBN} can do is guess whether a symbol
21555 refers to a function or variable depending on the linker section that
21556 contains the symbol. Also note that the actual contents of the memory
21557 contained in a DLL are not available unless the program is running. This
21558 means that you cannot examine the contents of a variable or disassemble
21559 a function within a DLL without a running program.
21561 Variables are generally treated as pointers and dereferenced
21562 automatically. For this reason, it is often necessary to prefix a
21563 variable name with the address-of operator (``&'') and provide explicit
21564 type information in the command. Here's an example of the type of
21568 (@value{GDBP}) print 'cygwin1!__argv'
21573 (@value{GDBP}) x 'cygwin1!__argv'
21574 0x10021610: "\230y\""
21577 And two possible solutions:
21580 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21581 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21585 (@value{GDBP}) x/2x &'cygwin1!__argv'
21586 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21587 (@value{GDBP}) x/x 0x10021608
21588 0x10021608: 0x0022fd98
21589 (@value{GDBP}) x/s 0x0022fd98
21590 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21593 Setting a break point within a DLL is possible even before the program
21594 starts execution. However, under these circumstances, @value{GDBN} can't
21595 examine the initial instructions of the function in order to skip the
21596 function's frame set-up code. You can work around this by using ``*&''
21597 to set the breakpoint at a raw memory address:
21600 (@value{GDBP}) break *&'python22!PyOS_Readline'
21601 Breakpoint 1 at 0x1e04eff0
21604 The author of these extensions is not entirely convinced that setting a
21605 break point within a shared DLL like @file{kernel32.dll} is completely
21609 @subsection Commands Specific to @sc{gnu} Hurd Systems
21610 @cindex @sc{gnu} Hurd debugging
21612 This subsection describes @value{GDBN} commands specific to the
21613 @sc{gnu} Hurd native debugging.
21618 @kindex set signals@r{, Hurd command}
21619 @kindex set sigs@r{, Hurd command}
21620 This command toggles the state of inferior signal interception by
21621 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21622 affected by this command. @code{sigs} is a shorthand alias for
21627 @kindex show signals@r{, Hurd command}
21628 @kindex show sigs@r{, Hurd command}
21629 Show the current state of intercepting inferior's signals.
21631 @item set signal-thread
21632 @itemx set sigthread
21633 @kindex set signal-thread
21634 @kindex set sigthread
21635 This command tells @value{GDBN} which thread is the @code{libc} signal
21636 thread. That thread is run when a signal is delivered to a running
21637 process. @code{set sigthread} is the shorthand alias of @code{set
21640 @item show signal-thread
21641 @itemx show sigthread
21642 @kindex show signal-thread
21643 @kindex show sigthread
21644 These two commands show which thread will run when the inferior is
21645 delivered a signal.
21648 @kindex set stopped@r{, Hurd command}
21649 This commands tells @value{GDBN} that the inferior process is stopped,
21650 as with the @code{SIGSTOP} signal. The stopped process can be
21651 continued by delivering a signal to it.
21654 @kindex show stopped@r{, Hurd command}
21655 This command shows whether @value{GDBN} thinks the debuggee is
21658 @item set exceptions
21659 @kindex set exceptions@r{, Hurd command}
21660 Use this command to turn off trapping of exceptions in the inferior.
21661 When exception trapping is off, neither breakpoints nor
21662 single-stepping will work. To restore the default, set exception
21665 @item show exceptions
21666 @kindex show exceptions@r{, Hurd command}
21667 Show the current state of trapping exceptions in the inferior.
21669 @item set task pause
21670 @kindex set task@r{, Hurd commands}
21671 @cindex task attributes (@sc{gnu} Hurd)
21672 @cindex pause current task (@sc{gnu} Hurd)
21673 This command toggles task suspension when @value{GDBN} has control.
21674 Setting it to on takes effect immediately, and the task is suspended
21675 whenever @value{GDBN} gets control. Setting it to off will take
21676 effect the next time the inferior is continued. If this option is set
21677 to off, you can use @code{set thread default pause on} or @code{set
21678 thread pause on} (see below) to pause individual threads.
21680 @item show task pause
21681 @kindex show task@r{, Hurd commands}
21682 Show the current state of task suspension.
21684 @item set task detach-suspend-count
21685 @cindex task suspend count
21686 @cindex detach from task, @sc{gnu} Hurd
21687 This command sets the suspend count the task will be left with when
21688 @value{GDBN} detaches from it.
21690 @item show task detach-suspend-count
21691 Show the suspend count the task will be left with when detaching.
21693 @item set task exception-port
21694 @itemx set task excp
21695 @cindex task exception port, @sc{gnu} Hurd
21696 This command sets the task exception port to which @value{GDBN} will
21697 forward exceptions. The argument should be the value of the @dfn{send
21698 rights} of the task. @code{set task excp} is a shorthand alias.
21700 @item set noninvasive
21701 @cindex noninvasive task options
21702 This command switches @value{GDBN} to a mode that is the least
21703 invasive as far as interfering with the inferior is concerned. This
21704 is the same as using @code{set task pause}, @code{set exceptions}, and
21705 @code{set signals} to values opposite to the defaults.
21707 @item info send-rights
21708 @itemx info receive-rights
21709 @itemx info port-rights
21710 @itemx info port-sets
21711 @itemx info dead-names
21714 @cindex send rights, @sc{gnu} Hurd
21715 @cindex receive rights, @sc{gnu} Hurd
21716 @cindex port rights, @sc{gnu} Hurd
21717 @cindex port sets, @sc{gnu} Hurd
21718 @cindex dead names, @sc{gnu} Hurd
21719 These commands display information about, respectively, send rights,
21720 receive rights, port rights, port sets, and dead names of a task.
21721 There are also shorthand aliases: @code{info ports} for @code{info
21722 port-rights} and @code{info psets} for @code{info port-sets}.
21724 @item set thread pause
21725 @kindex set thread@r{, Hurd command}
21726 @cindex thread properties, @sc{gnu} Hurd
21727 @cindex pause current thread (@sc{gnu} Hurd)
21728 This command toggles current thread suspension when @value{GDBN} has
21729 control. Setting it to on takes effect immediately, and the current
21730 thread is suspended whenever @value{GDBN} gets control. Setting it to
21731 off will take effect the next time the inferior is continued.
21732 Normally, this command has no effect, since when @value{GDBN} has
21733 control, the whole task is suspended. However, if you used @code{set
21734 task pause off} (see above), this command comes in handy to suspend
21735 only the current thread.
21737 @item show thread pause
21738 @kindex show thread@r{, Hurd command}
21739 This command shows the state of current thread suspension.
21741 @item set thread run
21742 This command sets whether the current thread is allowed to run.
21744 @item show thread run
21745 Show whether the current thread is allowed to run.
21747 @item set thread detach-suspend-count
21748 @cindex thread suspend count, @sc{gnu} Hurd
21749 @cindex detach from thread, @sc{gnu} Hurd
21750 This command sets the suspend count @value{GDBN} will leave on a
21751 thread when detaching. This number is relative to the suspend count
21752 found by @value{GDBN} when it notices the thread; use @code{set thread
21753 takeover-suspend-count} to force it to an absolute value.
21755 @item show thread detach-suspend-count
21756 Show the suspend count @value{GDBN} will leave on the thread when
21759 @item set thread exception-port
21760 @itemx set thread excp
21761 Set the thread exception port to which to forward exceptions. This
21762 overrides the port set by @code{set task exception-port} (see above).
21763 @code{set thread excp} is the shorthand alias.
21765 @item set thread takeover-suspend-count
21766 Normally, @value{GDBN}'s thread suspend counts are relative to the
21767 value @value{GDBN} finds when it notices each thread. This command
21768 changes the suspend counts to be absolute instead.
21770 @item set thread default
21771 @itemx show thread default
21772 @cindex thread default settings, @sc{gnu} Hurd
21773 Each of the above @code{set thread} commands has a @code{set thread
21774 default} counterpart (e.g., @code{set thread default pause}, @code{set
21775 thread default exception-port}, etc.). The @code{thread default}
21776 variety of commands sets the default thread properties for all
21777 threads; you can then change the properties of individual threads with
21778 the non-default commands.
21785 @value{GDBN} provides the following commands specific to the Darwin target:
21788 @item set debug darwin @var{num}
21789 @kindex set debug darwin
21790 When set to a non zero value, enables debugging messages specific to
21791 the Darwin support. Higher values produce more verbose output.
21793 @item show debug darwin
21794 @kindex show debug darwin
21795 Show the current state of Darwin messages.
21797 @item set debug mach-o @var{num}
21798 @kindex set debug mach-o
21799 When set to a non zero value, enables debugging messages while
21800 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21801 file format used on Darwin for object and executable files.) Higher
21802 values produce more verbose output. This is a command to diagnose
21803 problems internal to @value{GDBN} and should not be needed in normal
21806 @item show debug mach-o
21807 @kindex show debug mach-o
21808 Show the current state of Mach-O file messages.
21810 @item set mach-exceptions on
21811 @itemx set mach-exceptions off
21812 @kindex set mach-exceptions
21813 On Darwin, faults are first reported as a Mach exception and are then
21814 mapped to a Posix signal. Use this command to turn on trapping of
21815 Mach exceptions in the inferior. This might be sometimes useful to
21816 better understand the cause of a fault. The default is off.
21818 @item show mach-exceptions
21819 @kindex show mach-exceptions
21820 Show the current state of exceptions trapping.
21825 @section Embedded Operating Systems
21827 This section describes configurations involving the debugging of
21828 embedded operating systems that are available for several different
21831 @value{GDBN} includes the ability to debug programs running on
21832 various real-time operating systems.
21834 @node Embedded Processors
21835 @section Embedded Processors
21837 This section goes into details specific to particular embedded
21840 @cindex send command to simulator
21841 Whenever a specific embedded processor has a simulator, @value{GDBN}
21842 allows to send an arbitrary command to the simulator.
21845 @item sim @var{command}
21846 @kindex sim@r{, a command}
21847 Send an arbitrary @var{command} string to the simulator. Consult the
21848 documentation for the specific simulator in use for information about
21849 acceptable commands.
21855 * M68K:: Motorola M68K
21856 * MicroBlaze:: Xilinx MicroBlaze
21857 * MIPS Embedded:: MIPS Embedded
21858 * PowerPC Embedded:: PowerPC Embedded
21861 * Super-H:: Renesas Super-H
21867 @value{GDBN} provides the following ARM-specific commands:
21870 @item set arm disassembler
21872 This commands selects from a list of disassembly styles. The
21873 @code{"std"} style is the standard style.
21875 @item show arm disassembler
21877 Show the current disassembly style.
21879 @item set arm apcs32
21880 @cindex ARM 32-bit mode
21881 This command toggles ARM operation mode between 32-bit and 26-bit.
21883 @item show arm apcs32
21884 Display the current usage of the ARM 32-bit mode.
21886 @item set arm fpu @var{fputype}
21887 This command sets the ARM floating-point unit (FPU) type. The
21888 argument @var{fputype} can be one of these:
21892 Determine the FPU type by querying the OS ABI.
21894 Software FPU, with mixed-endian doubles on little-endian ARM
21897 GCC-compiled FPA co-processor.
21899 Software FPU with pure-endian doubles.
21905 Show the current type of the FPU.
21908 This command forces @value{GDBN} to use the specified ABI.
21911 Show the currently used ABI.
21913 @item set arm fallback-mode (arm|thumb|auto)
21914 @value{GDBN} uses the symbol table, when available, to determine
21915 whether instructions are ARM or Thumb. This command controls
21916 @value{GDBN}'s default behavior when the symbol table is not
21917 available. The default is @samp{auto}, which causes @value{GDBN} to
21918 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21921 @item show arm fallback-mode
21922 Show the current fallback instruction mode.
21924 @item set arm force-mode (arm|thumb|auto)
21925 This command overrides use of the symbol table to determine whether
21926 instructions are ARM or Thumb. The default is @samp{auto}, which
21927 causes @value{GDBN} to use the symbol table and then the setting
21928 of @samp{set arm fallback-mode}.
21930 @item show arm force-mode
21931 Show the current forced instruction mode.
21933 @item set debug arm
21934 Toggle whether to display ARM-specific debugging messages from the ARM
21935 target support subsystem.
21937 @item show debug arm
21938 Show whether ARM-specific debugging messages are enabled.
21942 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21943 The @value{GDBN} ARM simulator accepts the following optional arguments.
21946 @item --swi-support=@var{type}
21947 Tell the simulator which SWI interfaces to support. The argument
21948 @var{type} may be a comma separated list of the following values.
21949 The default value is @code{all}.
21964 The Motorola m68k configuration includes ColdFire support.
21967 @subsection MicroBlaze
21968 @cindex Xilinx MicroBlaze
21969 @cindex XMD, Xilinx Microprocessor Debugger
21971 The MicroBlaze is a soft-core processor supported on various Xilinx
21972 FPGAs, such as Spartan or Virtex series. Boards with these processors
21973 usually have JTAG ports which connect to a host system running the Xilinx
21974 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21975 This host system is used to download the configuration bitstream to
21976 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21977 communicates with the target board using the JTAG interface and
21978 presents a @code{gdbserver} interface to the board. By default
21979 @code{xmd} uses port @code{1234}. (While it is possible to change
21980 this default port, it requires the use of undocumented @code{xmd}
21981 commands. Contact Xilinx support if you need to do this.)
21983 Use these GDB commands to connect to the MicroBlaze target processor.
21986 @item target remote :1234
21987 Use this command to connect to the target if you are running @value{GDBN}
21988 on the same system as @code{xmd}.
21990 @item target remote @var{xmd-host}:1234
21991 Use this command to connect to the target if it is connected to @code{xmd}
21992 running on a different system named @var{xmd-host}.
21995 Use this command to download a program to the MicroBlaze target.
21997 @item set debug microblaze @var{n}
21998 Enable MicroBlaze-specific debugging messages if non-zero.
22000 @item show debug microblaze @var{n}
22001 Show MicroBlaze-specific debugging level.
22004 @node MIPS Embedded
22005 @subsection @acronym{MIPS} Embedded
22008 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22011 @item set mipsfpu double
22012 @itemx set mipsfpu single
22013 @itemx set mipsfpu none
22014 @itemx set mipsfpu auto
22015 @itemx show mipsfpu
22016 @kindex set mipsfpu
22017 @kindex show mipsfpu
22018 @cindex @acronym{MIPS} remote floating point
22019 @cindex floating point, @acronym{MIPS} remote
22020 If your target board does not support the @acronym{MIPS} floating point
22021 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22022 need this, you may wish to put the command in your @value{GDBN} init
22023 file). This tells @value{GDBN} how to find the return value of
22024 functions which return floating point values. It also allows
22025 @value{GDBN} to avoid saving the floating point registers when calling
22026 functions on the board. If you are using a floating point coprocessor
22027 with only single precision floating point support, as on the @sc{r4650}
22028 processor, use the command @samp{set mipsfpu single}. The default
22029 double precision floating point coprocessor may be selected using
22030 @samp{set mipsfpu double}.
22032 In previous versions the only choices were double precision or no
22033 floating point, so @samp{set mipsfpu on} will select double precision
22034 and @samp{set mipsfpu off} will select no floating point.
22036 As usual, you can inquire about the @code{mipsfpu} variable with
22037 @samp{show mipsfpu}.
22040 @node PowerPC Embedded
22041 @subsection PowerPC Embedded
22043 @cindex DVC register
22044 @value{GDBN} supports using the DVC (Data Value Compare) register to
22045 implement in hardware simple hardware watchpoint conditions of the form:
22048 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22049 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22052 The DVC register will be automatically used when @value{GDBN} detects
22053 such pattern in a condition expression, and the created watchpoint uses one
22054 debug register (either the @code{exact-watchpoints} option is on and the
22055 variable is scalar, or the variable has a length of one byte). This feature
22056 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22059 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22060 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22061 in which case watchpoints using only one debug register are created when
22062 watching variables of scalar types.
22064 You can create an artificial array to watch an arbitrary memory
22065 region using one of the following commands (@pxref{Expressions}):
22068 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22069 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22072 PowerPC embedded processors support masked watchpoints. See the discussion
22073 about the @code{mask} argument in @ref{Set Watchpoints}.
22075 @cindex ranged breakpoint
22076 PowerPC embedded processors support hardware accelerated
22077 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22078 the inferior whenever it executes an instruction at any address within
22079 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22080 use the @code{break-range} command.
22082 @value{GDBN} provides the following PowerPC-specific commands:
22085 @kindex break-range
22086 @item break-range @var{start-location}, @var{end-location}
22087 Set a breakpoint for an address range given by
22088 @var{start-location} and @var{end-location}, which can specify a function name,
22089 a line number, an offset of lines from the current line or from the start
22090 location, or an address of an instruction (see @ref{Specify Location},
22091 for a list of all the possible ways to specify a @var{location}.)
22092 The breakpoint will stop execution of the inferior whenever it
22093 executes an instruction at any address within the specified range,
22094 (including @var{start-location} and @var{end-location}.)
22096 @kindex set powerpc
22097 @item set powerpc soft-float
22098 @itemx show powerpc soft-float
22099 Force @value{GDBN} to use (or not use) a software floating point calling
22100 convention. By default, @value{GDBN} selects the calling convention based
22101 on the selected architecture and the provided executable file.
22103 @item set powerpc vector-abi
22104 @itemx show powerpc vector-abi
22105 Force @value{GDBN} to use the specified calling convention for vector
22106 arguments and return values. The valid options are @samp{auto};
22107 @samp{generic}, to avoid vector registers even if they are present;
22108 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22109 registers. By default, @value{GDBN} selects the calling convention
22110 based on the selected architecture and the provided executable file.
22112 @item set powerpc exact-watchpoints
22113 @itemx show powerpc exact-watchpoints
22114 Allow @value{GDBN} to use only one debug register when watching a variable
22115 of scalar type, thus assuming that the variable is accessed through the
22116 address of its first byte.
22121 @subsection Atmel AVR
22124 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22125 following AVR-specific commands:
22128 @item info io_registers
22129 @kindex info io_registers@r{, AVR}
22130 @cindex I/O registers (Atmel AVR)
22131 This command displays information about the AVR I/O registers. For
22132 each register, @value{GDBN} prints its number and value.
22139 When configured for debugging CRIS, @value{GDBN} provides the
22140 following CRIS-specific commands:
22143 @item set cris-version @var{ver}
22144 @cindex CRIS version
22145 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22146 The CRIS version affects register names and sizes. This command is useful in
22147 case autodetection of the CRIS version fails.
22149 @item show cris-version
22150 Show the current CRIS version.
22152 @item set cris-dwarf2-cfi
22153 @cindex DWARF-2 CFI and CRIS
22154 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22155 Change to @samp{off} when using @code{gcc-cris} whose version is below
22158 @item show cris-dwarf2-cfi
22159 Show the current state of using DWARF-2 CFI.
22161 @item set cris-mode @var{mode}
22163 Set the current CRIS mode to @var{mode}. It should only be changed when
22164 debugging in guru mode, in which case it should be set to
22165 @samp{guru} (the default is @samp{normal}).
22167 @item show cris-mode
22168 Show the current CRIS mode.
22172 @subsection Renesas Super-H
22175 For the Renesas Super-H processor, @value{GDBN} provides these
22179 @item set sh calling-convention @var{convention}
22180 @kindex set sh calling-convention
22181 Set the calling-convention used when calling functions from @value{GDBN}.
22182 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22183 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22184 convention. If the DWARF-2 information of the called function specifies
22185 that the function follows the Renesas calling convention, the function
22186 is called using the Renesas calling convention. If the calling convention
22187 is set to @samp{renesas}, the Renesas calling convention is always used,
22188 regardless of the DWARF-2 information. This can be used to override the
22189 default of @samp{gcc} if debug information is missing, or the compiler
22190 does not emit the DWARF-2 calling convention entry for a function.
22192 @item show sh calling-convention
22193 @kindex show sh calling-convention
22194 Show the current calling convention setting.
22199 @node Architectures
22200 @section Architectures
22202 This section describes characteristics of architectures that affect
22203 all uses of @value{GDBN} with the architecture, both native and cross.
22210 * HPPA:: HP PA architecture
22211 * SPU:: Cell Broadband Engine SPU architecture
22217 @subsection AArch64
22218 @cindex AArch64 support
22220 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22221 following special commands:
22224 @item set debug aarch64
22225 @kindex set debug aarch64
22226 This command determines whether AArch64 architecture-specific debugging
22227 messages are to be displayed.
22229 @item show debug aarch64
22230 Show whether AArch64 debugging messages are displayed.
22235 @subsection x86 Architecture-specific Issues
22238 @item set struct-convention @var{mode}
22239 @kindex set struct-convention
22240 @cindex struct return convention
22241 @cindex struct/union returned in registers
22242 Set the convention used by the inferior to return @code{struct}s and
22243 @code{union}s from functions to @var{mode}. Possible values of
22244 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22245 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22246 are returned on the stack, while @code{"reg"} means that a
22247 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22248 be returned in a register.
22250 @item show struct-convention
22251 @kindex show struct-convention
22252 Show the current setting of the convention to return @code{struct}s
22257 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22258 @cindex Intel Memory Protection Extensions (MPX).
22260 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22261 @footnote{The register named with capital letters represent the architecture
22262 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22263 which are the lower bound and upper bound. Bounds are effective addresses or
22264 memory locations. The upper bounds are architecturally represented in 1's
22265 complement form. A bound having lower bound = 0, and upper bound = 0
22266 (1's complement of all bits set) will allow access to the entire address space.
22268 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22269 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22270 display the upper bound performing the complement of one operation on the
22271 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22272 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22273 can also be noted that the upper bounds are inclusive.
22275 As an example, assume that the register BND0 holds bounds for a pointer having
22276 access allowed for the range between 0x32 and 0x71. The values present on
22277 bnd0raw and bnd registers are presented as follows:
22280 bnd0raw = @{0x32, 0xffffffff8e@}
22281 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22284 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22285 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22286 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22287 Python, the display includes the memory size, in bits, accessible to
22290 Bounds can also be stored in bounds tables, which are stored in
22291 application memory. These tables store bounds for pointers by specifying
22292 the bounds pointer's value along with its bounds. Evaluating and changing
22293 bounds located in bound tables is therefore interesting while investigating
22294 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22297 @item show mpx bound @var{pointer}
22298 @kindex show mpx bound
22299 Display bounds of the given @var{pointer}.
22301 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22302 @kindex set mpx bound
22303 Set the bounds of a pointer in the bound table.
22304 This command takes three parameters: @var{pointer} is the pointers
22305 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22306 for lower and upper bounds respectively.
22312 See the following section.
22315 @subsection @acronym{MIPS}
22317 @cindex stack on Alpha
22318 @cindex stack on @acronym{MIPS}
22319 @cindex Alpha stack
22320 @cindex @acronym{MIPS} stack
22321 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22322 sometimes requires @value{GDBN} to search backward in the object code to
22323 find the beginning of a function.
22325 @cindex response time, @acronym{MIPS} debugging
22326 To improve response time (especially for embedded applications, where
22327 @value{GDBN} may be restricted to a slow serial line for this search)
22328 you may want to limit the size of this search, using one of these
22332 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22333 @item set heuristic-fence-post @var{limit}
22334 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22335 search for the beginning of a function. A value of @var{0} (the
22336 default) means there is no limit. However, except for @var{0}, the
22337 larger the limit the more bytes @code{heuristic-fence-post} must search
22338 and therefore the longer it takes to run. You should only need to use
22339 this command when debugging a stripped executable.
22341 @item show heuristic-fence-post
22342 Display the current limit.
22346 These commands are available @emph{only} when @value{GDBN} is configured
22347 for debugging programs on Alpha or @acronym{MIPS} processors.
22349 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22353 @item set mips abi @var{arg}
22354 @kindex set mips abi
22355 @cindex set ABI for @acronym{MIPS}
22356 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22357 values of @var{arg} are:
22361 The default ABI associated with the current binary (this is the
22371 @item show mips abi
22372 @kindex show mips abi
22373 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22375 @item set mips compression @var{arg}
22376 @kindex set mips compression
22377 @cindex code compression, @acronym{MIPS}
22378 Tell @value{GDBN} which @acronym{MIPS} compressed
22379 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22380 inferior. @value{GDBN} uses this for code disassembly and other
22381 internal interpretation purposes. This setting is only referred to
22382 when no executable has been associated with the debugging session or
22383 the executable does not provide information about the encoding it uses.
22384 Otherwise this setting is automatically updated from information
22385 provided by the executable.
22387 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22388 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22389 executables containing @acronym{MIPS16} code frequently are not
22390 identified as such.
22392 This setting is ``sticky''; that is, it retains its value across
22393 debugging sessions until reset either explicitly with this command or
22394 implicitly from an executable.
22396 The compiler and/or assembler typically add symbol table annotations to
22397 identify functions compiled for the @acronym{MIPS16} or
22398 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22399 are present, @value{GDBN} uses them in preference to the global
22400 compressed @acronym{ISA} encoding setting.
22402 @item show mips compression
22403 @kindex show mips compression
22404 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22405 @value{GDBN} to debug the inferior.
22408 @itemx show mipsfpu
22409 @xref{MIPS Embedded, set mipsfpu}.
22411 @item set mips mask-address @var{arg}
22412 @kindex set mips mask-address
22413 @cindex @acronym{MIPS} addresses, masking
22414 This command determines whether the most-significant 32 bits of 64-bit
22415 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22416 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22417 setting, which lets @value{GDBN} determine the correct value.
22419 @item show mips mask-address
22420 @kindex show mips mask-address
22421 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22424 @item set remote-mips64-transfers-32bit-regs
22425 @kindex set remote-mips64-transfers-32bit-regs
22426 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22427 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22428 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22429 and 64 bits for other registers, set this option to @samp{on}.
22431 @item show remote-mips64-transfers-32bit-regs
22432 @kindex show remote-mips64-transfers-32bit-regs
22433 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22435 @item set debug mips
22436 @kindex set debug mips
22437 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22438 target code in @value{GDBN}.
22440 @item show debug mips
22441 @kindex show debug mips
22442 Show the current setting of @acronym{MIPS} debugging messages.
22448 @cindex HPPA support
22450 When @value{GDBN} is debugging the HP PA architecture, it provides the
22451 following special commands:
22454 @item set debug hppa
22455 @kindex set debug hppa
22456 This command determines whether HPPA architecture-specific debugging
22457 messages are to be displayed.
22459 @item show debug hppa
22460 Show whether HPPA debugging messages are displayed.
22462 @item maint print unwind @var{address}
22463 @kindex maint print unwind@r{, HPPA}
22464 This command displays the contents of the unwind table entry at the
22465 given @var{address}.
22471 @subsection Cell Broadband Engine SPU architecture
22472 @cindex Cell Broadband Engine
22475 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22476 it provides the following special commands:
22479 @item info spu event
22481 Display SPU event facility status. Shows current event mask
22482 and pending event status.
22484 @item info spu signal
22485 Display SPU signal notification facility status. Shows pending
22486 signal-control word and signal notification mode of both signal
22487 notification channels.
22489 @item info spu mailbox
22490 Display SPU mailbox facility status. Shows all pending entries,
22491 in order of processing, in each of the SPU Write Outbound,
22492 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22495 Display MFC DMA status. Shows all pending commands in the MFC
22496 DMA queue. For each entry, opcode, tag, class IDs, effective
22497 and local store addresses and transfer size are shown.
22499 @item info spu proxydma
22500 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22501 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22502 and local store addresses and transfer size are shown.
22506 When @value{GDBN} is debugging a combined PowerPC/SPU application
22507 on the Cell Broadband Engine, it provides in addition the following
22511 @item set spu stop-on-load @var{arg}
22513 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22514 will give control to the user when a new SPE thread enters its @code{main}
22515 function. The default is @code{off}.
22517 @item show spu stop-on-load
22519 Show whether to stop for new SPE threads.
22521 @item set spu auto-flush-cache @var{arg}
22522 Set whether to automatically flush the software-managed cache. When set to
22523 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22524 cache to be flushed whenever SPE execution stops. This provides a consistent
22525 view of PowerPC memory that is accessed via the cache. If an application
22526 does not use the software-managed cache, this option has no effect.
22528 @item show spu auto-flush-cache
22529 Show whether to automatically flush the software-managed cache.
22534 @subsection PowerPC
22535 @cindex PowerPC architecture
22537 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22538 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22539 numbers stored in the floating point registers. These values must be stored
22540 in two consecutive registers, always starting at an even register like
22541 @code{f0} or @code{f2}.
22543 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22544 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22545 @code{f2} and @code{f3} for @code{$dl1} and so on.
22547 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22548 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22551 @subsection Nios II
22552 @cindex Nios II architecture
22554 When @value{GDBN} is debugging the Nios II architecture,
22555 it provides the following special commands:
22559 @item set debug nios2
22560 @kindex set debug nios2
22561 This command turns on and off debugging messages for the Nios II
22562 target code in @value{GDBN}.
22564 @item show debug nios2
22565 @kindex show debug nios2
22566 Show the current setting of Nios II debugging messages.
22569 @node Controlling GDB
22570 @chapter Controlling @value{GDBN}
22572 You can alter the way @value{GDBN} interacts with you by using the
22573 @code{set} command. For commands controlling how @value{GDBN} displays
22574 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22579 * Editing:: Command editing
22580 * Command History:: Command history
22581 * Screen Size:: Screen size
22582 * Numbers:: Numbers
22583 * ABI:: Configuring the current ABI
22584 * Auto-loading:: Automatically loading associated files
22585 * Messages/Warnings:: Optional warnings and messages
22586 * Debugging Output:: Optional messages about internal happenings
22587 * Other Misc Settings:: Other Miscellaneous Settings
22595 @value{GDBN} indicates its readiness to read a command by printing a string
22596 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22597 can change the prompt string with the @code{set prompt} command. For
22598 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22599 the prompt in one of the @value{GDBN} sessions so that you can always tell
22600 which one you are talking to.
22602 @emph{Note:} @code{set prompt} does not add a space for you after the
22603 prompt you set. This allows you to set a prompt which ends in a space
22604 or a prompt that does not.
22608 @item set prompt @var{newprompt}
22609 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22611 @kindex show prompt
22613 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22616 Versions of @value{GDBN} that ship with Python scripting enabled have
22617 prompt extensions. The commands for interacting with these extensions
22621 @kindex set extended-prompt
22622 @item set extended-prompt @var{prompt}
22623 Set an extended prompt that allows for substitutions.
22624 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22625 substitution. Any escape sequences specified as part of the prompt
22626 string are replaced with the corresponding strings each time the prompt
22632 set extended-prompt Current working directory: \w (gdb)
22635 Note that when an extended-prompt is set, it takes control of the
22636 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22638 @kindex show extended-prompt
22639 @item show extended-prompt
22640 Prints the extended prompt. Any escape sequences specified as part of
22641 the prompt string with @code{set extended-prompt}, are replaced with the
22642 corresponding strings each time the prompt is displayed.
22646 @section Command Editing
22648 @cindex command line editing
22650 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22651 @sc{gnu} library provides consistent behavior for programs which provide a
22652 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22653 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22654 substitution, and a storage and recall of command history across
22655 debugging sessions.
22657 You may control the behavior of command line editing in @value{GDBN} with the
22658 command @code{set}.
22661 @kindex set editing
22664 @itemx set editing on
22665 Enable command line editing (enabled by default).
22667 @item set editing off
22668 Disable command line editing.
22670 @kindex show editing
22672 Show whether command line editing is enabled.
22675 @ifset SYSTEM_READLINE
22676 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22678 @ifclear SYSTEM_READLINE
22679 @xref{Command Line Editing},
22681 for more details about the Readline
22682 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22683 encouraged to read that chapter.
22685 @node Command History
22686 @section Command History
22687 @cindex command history
22689 @value{GDBN} can keep track of the commands you type during your
22690 debugging sessions, so that you can be certain of precisely what
22691 happened. Use these commands to manage the @value{GDBN} command
22694 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22695 package, to provide the history facility.
22696 @ifset SYSTEM_READLINE
22697 @xref{Using History Interactively, , , history, GNU History Library},
22699 @ifclear SYSTEM_READLINE
22700 @xref{Using History Interactively},
22702 for the detailed description of the History library.
22704 To issue a command to @value{GDBN} without affecting certain aspects of
22705 the state which is seen by users, prefix it with @samp{server }
22706 (@pxref{Server Prefix}). This
22707 means that this command will not affect the command history, nor will it
22708 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22709 pressed on a line by itself.
22711 @cindex @code{server}, command prefix
22712 The server prefix does not affect the recording of values into the value
22713 history; to print a value without recording it into the value history,
22714 use the @code{output} command instead of the @code{print} command.
22716 Here is the description of @value{GDBN} commands related to command
22720 @cindex history substitution
22721 @cindex history file
22722 @kindex set history filename
22723 @cindex @env{GDBHISTFILE}, environment variable
22724 @item set history filename @var{fname}
22725 Set the name of the @value{GDBN} command history file to @var{fname}.
22726 This is the file where @value{GDBN} reads an initial command history
22727 list, and where it writes the command history from this session when it
22728 exits. You can access this list through history expansion or through
22729 the history command editing characters listed below. This file defaults
22730 to the value of the environment variable @code{GDBHISTFILE}, or to
22731 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22734 @cindex save command history
22735 @kindex set history save
22736 @item set history save
22737 @itemx set history save on
22738 Record command history in a file, whose name may be specified with the
22739 @code{set history filename} command. By default, this option is disabled.
22741 @item set history save off
22742 Stop recording command history in a file.
22744 @cindex history size
22745 @kindex set history size
22746 @cindex @env{GDBHISTSIZE}, environment variable
22747 @item set history size @var{size}
22748 @itemx set history size unlimited
22749 Set the number of commands which @value{GDBN} keeps in its history list.
22750 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22751 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22752 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22753 either a negative number or the empty string, then the number of commands
22754 @value{GDBN} keeps in the history list is unlimited.
22756 @cindex remove duplicate history
22757 @kindex set history remove-duplicates
22758 @item set history remove-duplicates @var{count}
22759 @itemx set history remove-duplicates unlimited
22760 Control the removal of duplicate history entries in the command history list.
22761 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22762 history entries and remove the first entry that is a duplicate of the current
22763 entry being added to the command history list. If @var{count} is
22764 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22765 removal of duplicate history entries is disabled.
22767 Only history entries added during the current session are considered for
22768 removal. This option is set to 0 by default.
22772 History expansion assigns special meaning to the character @kbd{!}.
22773 @ifset SYSTEM_READLINE
22774 @xref{Event Designators, , , history, GNU History Library},
22776 @ifclear SYSTEM_READLINE
22777 @xref{Event Designators},
22781 @cindex history expansion, turn on/off
22782 Since @kbd{!} is also the logical not operator in C, history expansion
22783 is off by default. If you decide to enable history expansion with the
22784 @code{set history expansion on} command, you may sometimes need to
22785 follow @kbd{!} (when it is used as logical not, in an expression) with
22786 a space or a tab to prevent it from being expanded. The readline
22787 history facilities do not attempt substitution on the strings
22788 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22790 The commands to control history expansion are:
22793 @item set history expansion on
22794 @itemx set history expansion
22795 @kindex set history expansion
22796 Enable history expansion. History expansion is off by default.
22798 @item set history expansion off
22799 Disable history expansion.
22802 @kindex show history
22804 @itemx show history filename
22805 @itemx show history save
22806 @itemx show history size
22807 @itemx show history expansion
22808 These commands display the state of the @value{GDBN} history parameters.
22809 @code{show history} by itself displays all four states.
22814 @kindex show commands
22815 @cindex show last commands
22816 @cindex display command history
22817 @item show commands
22818 Display the last ten commands in the command history.
22820 @item show commands @var{n}
22821 Print ten commands centered on command number @var{n}.
22823 @item show commands +
22824 Print ten commands just after the commands last printed.
22828 @section Screen Size
22829 @cindex size of screen
22830 @cindex screen size
22833 @cindex pauses in output
22835 Certain commands to @value{GDBN} may produce large amounts of
22836 information output to the screen. To help you read all of it,
22837 @value{GDBN} pauses and asks you for input at the end of each page of
22838 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22839 to discard the remaining output. Also, the screen width setting
22840 determines when to wrap lines of output. Depending on what is being
22841 printed, @value{GDBN} tries to break the line at a readable place,
22842 rather than simply letting it overflow onto the following line.
22844 Normally @value{GDBN} knows the size of the screen from the terminal
22845 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22846 together with the value of the @code{TERM} environment variable and the
22847 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22848 you can override it with the @code{set height} and @code{set
22855 @kindex show height
22856 @item set height @var{lpp}
22857 @itemx set height unlimited
22859 @itemx set width @var{cpl}
22860 @itemx set width unlimited
22862 These @code{set} commands specify a screen height of @var{lpp} lines and
22863 a screen width of @var{cpl} characters. The associated @code{show}
22864 commands display the current settings.
22866 If you specify a height of either @code{unlimited} or zero lines,
22867 @value{GDBN} does not pause during output no matter how long the
22868 output is. This is useful if output is to a file or to an editor
22871 Likewise, you can specify @samp{set width unlimited} or @samp{set
22872 width 0} to prevent @value{GDBN} from wrapping its output.
22874 @item set pagination on
22875 @itemx set pagination off
22876 @kindex set pagination
22877 Turn the output pagination on or off; the default is on. Turning
22878 pagination off is the alternative to @code{set height unlimited}. Note that
22879 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22880 Options, -batch}) also automatically disables pagination.
22882 @item show pagination
22883 @kindex show pagination
22884 Show the current pagination mode.
22889 @cindex number representation
22890 @cindex entering numbers
22892 You can always enter numbers in octal, decimal, or hexadecimal in
22893 @value{GDBN} by the usual conventions: octal numbers begin with
22894 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22895 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22896 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22897 10; likewise, the default display for numbers---when no particular
22898 format is specified---is base 10. You can change the default base for
22899 both input and output with the commands described below.
22902 @kindex set input-radix
22903 @item set input-radix @var{base}
22904 Set the default base for numeric input. Supported choices
22905 for @var{base} are decimal 8, 10, or 16. The base must itself be
22906 specified either unambiguously or using the current input radix; for
22910 set input-radix 012
22911 set input-radix 10.
22912 set input-radix 0xa
22916 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22917 leaves the input radix unchanged, no matter what it was, since
22918 @samp{10}, being without any leading or trailing signs of its base, is
22919 interpreted in the current radix. Thus, if the current radix is 16,
22920 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22923 @kindex set output-radix
22924 @item set output-radix @var{base}
22925 Set the default base for numeric display. Supported choices
22926 for @var{base} are decimal 8, 10, or 16. The base must itself be
22927 specified either unambiguously or using the current input radix.
22929 @kindex show input-radix
22930 @item show input-radix
22931 Display the current default base for numeric input.
22933 @kindex show output-radix
22934 @item show output-radix
22935 Display the current default base for numeric display.
22937 @item set radix @r{[}@var{base}@r{]}
22941 These commands set and show the default base for both input and output
22942 of numbers. @code{set radix} sets the radix of input and output to
22943 the same base; without an argument, it resets the radix back to its
22944 default value of 10.
22949 @section Configuring the Current ABI
22951 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22952 application automatically. However, sometimes you need to override its
22953 conclusions. Use these commands to manage @value{GDBN}'s view of the
22959 @cindex Newlib OS ABI and its influence on the longjmp handling
22961 One @value{GDBN} configuration can debug binaries for multiple operating
22962 system targets, either via remote debugging or native emulation.
22963 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22964 but you can override its conclusion using the @code{set osabi} command.
22965 One example where this is useful is in debugging of binaries which use
22966 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22967 not have the same identifying marks that the standard C library for your
22970 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22971 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22972 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22973 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22977 Show the OS ABI currently in use.
22980 With no argument, show the list of registered available OS ABI's.
22982 @item set osabi @var{abi}
22983 Set the current OS ABI to @var{abi}.
22986 @cindex float promotion
22988 Generally, the way that an argument of type @code{float} is passed to a
22989 function depends on whether the function is prototyped. For a prototyped
22990 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22991 according to the architecture's convention for @code{float}. For unprototyped
22992 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22993 @code{double} and then passed.
22995 Unfortunately, some forms of debug information do not reliably indicate whether
22996 a function is prototyped. If @value{GDBN} calls a function that is not marked
22997 as prototyped, it consults @kbd{set coerce-float-to-double}.
23000 @kindex set coerce-float-to-double
23001 @item set coerce-float-to-double
23002 @itemx set coerce-float-to-double on
23003 Arguments of type @code{float} will be promoted to @code{double} when passed
23004 to an unprototyped function. This is the default setting.
23006 @item set coerce-float-to-double off
23007 Arguments of type @code{float} will be passed directly to unprototyped
23010 @kindex show coerce-float-to-double
23011 @item show coerce-float-to-double
23012 Show the current setting of promoting @code{float} to @code{double}.
23016 @kindex show cp-abi
23017 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23018 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23019 used to build your application. @value{GDBN} only fully supports
23020 programs with a single C@t{++} ABI; if your program contains code using
23021 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23022 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23023 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23024 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23025 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23026 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23031 Show the C@t{++} ABI currently in use.
23034 With no argument, show the list of supported C@t{++} ABI's.
23036 @item set cp-abi @var{abi}
23037 @itemx set cp-abi auto
23038 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23042 @section Automatically loading associated files
23043 @cindex auto-loading
23045 @value{GDBN} sometimes reads files with commands and settings automatically,
23046 without being explicitly told so by the user. We call this feature
23047 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23048 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23049 results or introduce security risks (e.g., if the file comes from untrusted
23053 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23054 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23056 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23057 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23060 There are various kinds of files @value{GDBN} can automatically load.
23061 In addition to these files, @value{GDBN} supports auto-loading code written
23062 in various extension languages. @xref{Auto-loading extensions}.
23064 Note that loading of these associated files (including the local @file{.gdbinit}
23065 file) requires accordingly configured @code{auto-load safe-path}
23066 (@pxref{Auto-loading safe path}).
23068 For these reasons, @value{GDBN} includes commands and options to let you
23069 control when to auto-load files and which files should be auto-loaded.
23072 @anchor{set auto-load off}
23073 @kindex set auto-load off
23074 @item set auto-load off
23075 Globally disable loading of all auto-loaded files.
23076 You may want to use this command with the @samp{-iex} option
23077 (@pxref{Option -init-eval-command}) such as:
23079 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23082 Be aware that system init file (@pxref{System-wide configuration})
23083 and init files from your home directory (@pxref{Home Directory Init File})
23084 still get read (as they come from generally trusted directories).
23085 To prevent @value{GDBN} from auto-loading even those init files, use the
23086 @option{-nx} option (@pxref{Mode Options}), in addition to
23087 @code{set auto-load no}.
23089 @anchor{show auto-load}
23090 @kindex show auto-load
23091 @item show auto-load
23092 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23096 (gdb) show auto-load
23097 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23098 libthread-db: Auto-loading of inferior specific libthread_db is on.
23099 local-gdbinit: Auto-loading of .gdbinit script from current directory
23101 python-scripts: Auto-loading of Python scripts is on.
23102 safe-path: List of directories from which it is safe to auto-load files
23103 is $debugdir:$datadir/auto-load.
23104 scripts-directory: List of directories from which to load auto-loaded scripts
23105 is $debugdir:$datadir/auto-load.
23108 @anchor{info auto-load}
23109 @kindex info auto-load
23110 @item info auto-load
23111 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23115 (gdb) info auto-load
23118 Yes /home/user/gdb/gdb-gdb.gdb
23119 libthread-db: No auto-loaded libthread-db.
23120 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23124 Yes /home/user/gdb/gdb-gdb.py
23128 These are @value{GDBN} control commands for the auto-loading:
23130 @multitable @columnfractions .5 .5
23131 @item @xref{set auto-load off}.
23132 @tab Disable auto-loading globally.
23133 @item @xref{show auto-load}.
23134 @tab Show setting of all kinds of files.
23135 @item @xref{info auto-load}.
23136 @tab Show state of all kinds of files.
23137 @item @xref{set auto-load gdb-scripts}.
23138 @tab Control for @value{GDBN} command scripts.
23139 @item @xref{show auto-load gdb-scripts}.
23140 @tab Show setting of @value{GDBN} command scripts.
23141 @item @xref{info auto-load gdb-scripts}.
23142 @tab Show state of @value{GDBN} command scripts.
23143 @item @xref{set auto-load python-scripts}.
23144 @tab Control for @value{GDBN} Python scripts.
23145 @item @xref{show auto-load python-scripts}.
23146 @tab Show setting of @value{GDBN} Python scripts.
23147 @item @xref{info auto-load python-scripts}.
23148 @tab Show state of @value{GDBN} Python scripts.
23149 @item @xref{set auto-load guile-scripts}.
23150 @tab Control for @value{GDBN} Guile scripts.
23151 @item @xref{show auto-load guile-scripts}.
23152 @tab Show setting of @value{GDBN} Guile scripts.
23153 @item @xref{info auto-load guile-scripts}.
23154 @tab Show state of @value{GDBN} Guile scripts.
23155 @item @xref{set auto-load scripts-directory}.
23156 @tab Control for @value{GDBN} auto-loaded scripts location.
23157 @item @xref{show auto-load scripts-directory}.
23158 @tab Show @value{GDBN} auto-loaded scripts location.
23159 @item @xref{add-auto-load-scripts-directory}.
23160 @tab Add directory for auto-loaded scripts location list.
23161 @item @xref{set auto-load local-gdbinit}.
23162 @tab Control for init file in the current directory.
23163 @item @xref{show auto-load local-gdbinit}.
23164 @tab Show setting of init file in the current directory.
23165 @item @xref{info auto-load local-gdbinit}.
23166 @tab Show state of init file in the current directory.
23167 @item @xref{set auto-load libthread-db}.
23168 @tab Control for thread debugging library.
23169 @item @xref{show auto-load libthread-db}.
23170 @tab Show setting of thread debugging library.
23171 @item @xref{info auto-load libthread-db}.
23172 @tab Show state of thread debugging library.
23173 @item @xref{set auto-load safe-path}.
23174 @tab Control directories trusted for automatic loading.
23175 @item @xref{show auto-load safe-path}.
23176 @tab Show directories trusted for automatic loading.
23177 @item @xref{add-auto-load-safe-path}.
23178 @tab Add directory trusted for automatic loading.
23181 @node Init File in the Current Directory
23182 @subsection Automatically loading init file in the current directory
23183 @cindex auto-loading init file in the current directory
23185 By default, @value{GDBN} reads and executes the canned sequences of commands
23186 from init file (if any) in the current working directory,
23187 see @ref{Init File in the Current Directory during Startup}.
23189 Note that loading of this local @file{.gdbinit} file also requires accordingly
23190 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23193 @anchor{set auto-load local-gdbinit}
23194 @kindex set auto-load local-gdbinit
23195 @item set auto-load local-gdbinit [on|off]
23196 Enable or disable the auto-loading of canned sequences of commands
23197 (@pxref{Sequences}) found in init file in the current directory.
23199 @anchor{show auto-load local-gdbinit}
23200 @kindex show auto-load local-gdbinit
23201 @item show auto-load local-gdbinit
23202 Show whether auto-loading of canned sequences of commands from init file in the
23203 current directory is enabled or disabled.
23205 @anchor{info auto-load local-gdbinit}
23206 @kindex info auto-load local-gdbinit
23207 @item info auto-load local-gdbinit
23208 Print whether canned sequences of commands from init file in the
23209 current directory have been auto-loaded.
23212 @node libthread_db.so.1 file
23213 @subsection Automatically loading thread debugging library
23214 @cindex auto-loading libthread_db.so.1
23216 This feature is currently present only on @sc{gnu}/Linux native hosts.
23218 @value{GDBN} reads in some cases thread debugging library from places specific
23219 to the inferior (@pxref{set libthread-db-search-path}).
23221 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23222 without checking this @samp{set auto-load libthread-db} switch as system
23223 libraries have to be trusted in general. In all other cases of
23224 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23225 auto-load libthread-db} is enabled before trying to open such thread debugging
23228 Note that loading of this debugging library also requires accordingly configured
23229 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23232 @anchor{set auto-load libthread-db}
23233 @kindex set auto-load libthread-db
23234 @item set auto-load libthread-db [on|off]
23235 Enable or disable the auto-loading of inferior specific thread debugging library.
23237 @anchor{show auto-load libthread-db}
23238 @kindex show auto-load libthread-db
23239 @item show auto-load libthread-db
23240 Show whether auto-loading of inferior specific thread debugging library is
23241 enabled or disabled.
23243 @anchor{info auto-load libthread-db}
23244 @kindex info auto-load libthread-db
23245 @item info auto-load libthread-db
23246 Print the list of all loaded inferior specific thread debugging libraries and
23247 for each such library print list of inferior @var{pid}s using it.
23250 @node Auto-loading safe path
23251 @subsection Security restriction for auto-loading
23252 @cindex auto-loading safe-path
23254 As the files of inferior can come from untrusted source (such as submitted by
23255 an application user) @value{GDBN} does not always load any files automatically.
23256 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23257 directories trusted for loading files not explicitly requested by user.
23258 Each directory can also be a shell wildcard pattern.
23260 If the path is not set properly you will see a warning and the file will not
23265 Reading symbols from /home/user/gdb/gdb...done.
23266 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23267 declined by your `auto-load safe-path' set
23268 to "$debugdir:$datadir/auto-load".
23269 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23270 declined by your `auto-load safe-path' set
23271 to "$debugdir:$datadir/auto-load".
23275 To instruct @value{GDBN} to go ahead and use the init files anyway,
23276 invoke @value{GDBN} like this:
23279 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23282 The list of trusted directories is controlled by the following commands:
23285 @anchor{set auto-load safe-path}
23286 @kindex set auto-load safe-path
23287 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23288 Set the list of directories (and their subdirectories) trusted for automatic
23289 loading and execution of scripts. You can also enter a specific trusted file.
23290 Each directory can also be a shell wildcard pattern; wildcards do not match
23291 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23292 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23293 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23294 its default value as specified during @value{GDBN} compilation.
23296 The list of directories uses path separator (@samp{:} on GNU and Unix
23297 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23298 to the @env{PATH} environment variable.
23300 @anchor{show auto-load safe-path}
23301 @kindex show auto-load safe-path
23302 @item show auto-load safe-path
23303 Show the list of directories trusted for automatic loading and execution of
23306 @anchor{add-auto-load-safe-path}
23307 @kindex add-auto-load-safe-path
23308 @item add-auto-load-safe-path
23309 Add an entry (or list of entries) to the list of directories trusted for
23310 automatic loading and execution of scripts. Multiple entries may be delimited
23311 by the host platform path separator in use.
23314 This variable defaults to what @code{--with-auto-load-dir} has been configured
23315 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23316 substitution applies the same as for @ref{set auto-load scripts-directory}.
23317 The default @code{set auto-load safe-path} value can be also overriden by
23318 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23320 Setting this variable to @file{/} disables this security protection,
23321 corresponding @value{GDBN} configuration option is
23322 @option{--without-auto-load-safe-path}.
23323 This variable is supposed to be set to the system directories writable by the
23324 system superuser only. Users can add their source directories in init files in
23325 their home directories (@pxref{Home Directory Init File}). See also deprecated
23326 init file in the current directory
23327 (@pxref{Init File in the Current Directory during Startup}).
23329 To force @value{GDBN} to load the files it declined to load in the previous
23330 example, you could use one of the following ways:
23333 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23334 Specify this trusted directory (or a file) as additional component of the list.
23335 You have to specify also any existing directories displayed by
23336 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23338 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23339 Specify this directory as in the previous case but just for a single
23340 @value{GDBN} session.
23342 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23343 Disable auto-loading safety for a single @value{GDBN} session.
23344 This assumes all the files you debug during this @value{GDBN} session will come
23345 from trusted sources.
23347 @item @kbd{./configure --without-auto-load-safe-path}
23348 During compilation of @value{GDBN} you may disable any auto-loading safety.
23349 This assumes all the files you will ever debug with this @value{GDBN} come from
23353 On the other hand you can also explicitly forbid automatic files loading which
23354 also suppresses any such warning messages:
23357 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23358 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23360 @item @file{~/.gdbinit}: @samp{set auto-load no}
23361 Disable auto-loading globally for the user
23362 (@pxref{Home Directory Init File}). While it is improbable, you could also
23363 use system init file instead (@pxref{System-wide configuration}).
23366 This setting applies to the file names as entered by user. If no entry matches
23367 @value{GDBN} tries as a last resort to also resolve all the file names into
23368 their canonical form (typically resolving symbolic links) and compare the
23369 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23370 own before starting the comparison so a canonical form of directories is
23371 recommended to be entered.
23373 @node Auto-loading verbose mode
23374 @subsection Displaying files tried for auto-load
23375 @cindex auto-loading verbose mode
23377 For better visibility of all the file locations where you can place scripts to
23378 be auto-loaded with inferior --- or to protect yourself against accidental
23379 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23380 all the files attempted to be loaded. Both existing and non-existing files may
23383 For example the list of directories from which it is safe to auto-load files
23384 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23385 may not be too obvious while setting it up.
23388 (gdb) set debug auto-load on
23389 (gdb) file ~/src/t/true
23390 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23391 for objfile "/tmp/true".
23392 auto-load: Updating directories of "/usr:/opt".
23393 auto-load: Using directory "/usr".
23394 auto-load: Using directory "/opt".
23395 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23396 by your `auto-load safe-path' set to "/usr:/opt".
23400 @anchor{set debug auto-load}
23401 @kindex set debug auto-load
23402 @item set debug auto-load [on|off]
23403 Set whether to print the filenames attempted to be auto-loaded.
23405 @anchor{show debug auto-load}
23406 @kindex show debug auto-load
23407 @item show debug auto-load
23408 Show whether printing of the filenames attempted to be auto-loaded is turned
23412 @node Messages/Warnings
23413 @section Optional Warnings and Messages
23415 @cindex verbose operation
23416 @cindex optional warnings
23417 By default, @value{GDBN} is silent about its inner workings. If you are
23418 running on a slow machine, you may want to use the @code{set verbose}
23419 command. This makes @value{GDBN} tell you when it does a lengthy
23420 internal operation, so you will not think it has crashed.
23422 Currently, the messages controlled by @code{set verbose} are those
23423 which announce that the symbol table for a source file is being read;
23424 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23427 @kindex set verbose
23428 @item set verbose on
23429 Enables @value{GDBN} output of certain informational messages.
23431 @item set verbose off
23432 Disables @value{GDBN} output of certain informational messages.
23434 @kindex show verbose
23436 Displays whether @code{set verbose} is on or off.
23439 By default, if @value{GDBN} encounters bugs in the symbol table of an
23440 object file, it is silent; but if you are debugging a compiler, you may
23441 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23446 @kindex set complaints
23447 @item set complaints @var{limit}
23448 Permits @value{GDBN} to output @var{limit} complaints about each type of
23449 unusual symbols before becoming silent about the problem. Set
23450 @var{limit} to zero to suppress all complaints; set it to a large number
23451 to prevent complaints from being suppressed.
23453 @kindex show complaints
23454 @item show complaints
23455 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23459 @anchor{confirmation requests}
23460 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23461 lot of stupid questions to confirm certain commands. For example, if
23462 you try to run a program which is already running:
23466 The program being debugged has been started already.
23467 Start it from the beginning? (y or n)
23470 If you are willing to unflinchingly face the consequences of your own
23471 commands, you can disable this ``feature'':
23475 @kindex set confirm
23477 @cindex confirmation
23478 @cindex stupid questions
23479 @item set confirm off
23480 Disables confirmation requests. Note that running @value{GDBN} with
23481 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23482 automatically disables confirmation requests.
23484 @item set confirm on
23485 Enables confirmation requests (the default).
23487 @kindex show confirm
23489 Displays state of confirmation requests.
23493 @cindex command tracing
23494 If you need to debug user-defined commands or sourced files you may find it
23495 useful to enable @dfn{command tracing}. In this mode each command will be
23496 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23497 quantity denoting the call depth of each command.
23500 @kindex set trace-commands
23501 @cindex command scripts, debugging
23502 @item set trace-commands on
23503 Enable command tracing.
23504 @item set trace-commands off
23505 Disable command tracing.
23506 @item show trace-commands
23507 Display the current state of command tracing.
23510 @node Debugging Output
23511 @section Optional Messages about Internal Happenings
23512 @cindex optional debugging messages
23514 @value{GDBN} has commands that enable optional debugging messages from
23515 various @value{GDBN} subsystems; normally these commands are of
23516 interest to @value{GDBN} maintainers, or when reporting a bug. This
23517 section documents those commands.
23520 @kindex set exec-done-display
23521 @item set exec-done-display
23522 Turns on or off the notification of asynchronous commands'
23523 completion. When on, @value{GDBN} will print a message when an
23524 asynchronous command finishes its execution. The default is off.
23525 @kindex show exec-done-display
23526 @item show exec-done-display
23527 Displays the current setting of asynchronous command completion
23530 @cindex ARM AArch64
23531 @item set debug aarch64
23532 Turns on or off display of debugging messages related to ARM AArch64.
23533 The default is off.
23535 @item show debug aarch64
23536 Displays the current state of displaying debugging messages related to
23538 @cindex gdbarch debugging info
23539 @cindex architecture debugging info
23540 @item set debug arch
23541 Turns on or off display of gdbarch debugging info. The default is off
23542 @item show debug arch
23543 Displays the current state of displaying gdbarch debugging info.
23544 @item set debug aix-solib
23545 @cindex AIX shared library debugging
23546 Control display of debugging messages from the AIX shared library
23547 support module. The default is off.
23548 @item show debug aix-thread
23549 Show the current state of displaying AIX shared library debugging messages.
23550 @item set debug aix-thread
23551 @cindex AIX threads
23552 Display debugging messages about inner workings of the AIX thread
23554 @item show debug aix-thread
23555 Show the current state of AIX thread debugging info display.
23556 @item set debug check-physname
23558 Check the results of the ``physname'' computation. When reading DWARF
23559 debugging information for C@t{++}, @value{GDBN} attempts to compute
23560 each entity's name. @value{GDBN} can do this computation in two
23561 different ways, depending on exactly what information is present.
23562 When enabled, this setting causes @value{GDBN} to compute the names
23563 both ways and display any discrepancies.
23564 @item show debug check-physname
23565 Show the current state of ``physname'' checking.
23566 @item set debug coff-pe-read
23567 @cindex COFF/PE exported symbols
23568 Control display of debugging messages related to reading of COFF/PE
23569 exported symbols. The default is off.
23570 @item show debug coff-pe-read
23571 Displays the current state of displaying debugging messages related to
23572 reading of COFF/PE exported symbols.
23573 @item set debug dwarf-die
23575 Dump DWARF DIEs after they are read in.
23576 The value is the number of nesting levels to print.
23577 A value of zero turns off the display.
23578 @item show debug dwarf-die
23579 Show the current state of DWARF DIE debugging.
23580 @item set debug dwarf-line
23581 @cindex DWARF Line Tables
23582 Turns on or off display of debugging messages related to reading
23583 DWARF line tables. The default is 0 (off).
23584 A value of 1 provides basic information.
23585 A value greater than 1 provides more verbose information.
23586 @item show debug dwarf-line
23587 Show the current state of DWARF line table debugging.
23588 @item set debug dwarf-read
23589 @cindex DWARF Reading
23590 Turns on or off display of debugging messages related to reading
23591 DWARF debug info. The default is 0 (off).
23592 A value of 1 provides basic information.
23593 A value greater than 1 provides more verbose information.
23594 @item show debug dwarf-read
23595 Show the current state of DWARF reader debugging.
23596 @item set debug displaced
23597 @cindex displaced stepping debugging info
23598 Turns on or off display of @value{GDBN} debugging info for the
23599 displaced stepping support. The default is off.
23600 @item show debug displaced
23601 Displays the current state of displaying @value{GDBN} debugging info
23602 related to displaced stepping.
23603 @item set debug event
23604 @cindex event debugging info
23605 Turns on or off display of @value{GDBN} event debugging info. The
23607 @item show debug event
23608 Displays the current state of displaying @value{GDBN} event debugging
23610 @item set debug expression
23611 @cindex expression debugging info
23612 Turns on or off display of debugging info about @value{GDBN}
23613 expression parsing. The default is off.
23614 @item show debug expression
23615 Displays the current state of displaying debugging info about
23616 @value{GDBN} expression parsing.
23617 @item set debug fbsd-lwp
23618 @cindex FreeBSD LWP debug messages
23619 Turns on or off debugging messages from the FreeBSD LWP debug support.
23620 @item show debug fbsd-lwp
23621 Show the current state of FreeBSD LWP debugging messages.
23622 @item set debug frame
23623 @cindex frame debugging info
23624 Turns on or off display of @value{GDBN} frame debugging info. The
23626 @item show debug frame
23627 Displays the current state of displaying @value{GDBN} frame debugging
23629 @item set debug gnu-nat
23630 @cindex @sc{gnu}/Hurd debug messages
23631 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23632 @item show debug gnu-nat
23633 Show the current state of @sc{gnu}/Hurd debugging messages.
23634 @item set debug infrun
23635 @cindex inferior debugging info
23636 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23637 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23638 for implementing operations such as single-stepping the inferior.
23639 @item show debug infrun
23640 Displays the current state of @value{GDBN} inferior debugging.
23641 @item set debug jit
23642 @cindex just-in-time compilation, debugging messages
23643 Turn on or off debugging messages from JIT debug support.
23644 @item show debug jit
23645 Displays the current state of @value{GDBN} JIT debugging.
23646 @item set debug lin-lwp
23647 @cindex @sc{gnu}/Linux LWP debug messages
23648 @cindex Linux lightweight processes
23649 Turn on or off debugging messages from the Linux LWP debug support.
23650 @item show debug lin-lwp
23651 Show the current state of Linux LWP debugging messages.
23652 @item set debug linux-namespaces
23653 @cindex @sc{gnu}/Linux namespaces debug messages
23654 Turn on or off debugging messages from the Linux namespaces debug support.
23655 @item show debug linux-namespaces
23656 Show the current state of Linux namespaces debugging messages.
23657 @item set debug mach-o
23658 @cindex Mach-O symbols processing
23659 Control display of debugging messages related to Mach-O symbols
23660 processing. The default is off.
23661 @item show debug mach-o
23662 Displays the current state of displaying debugging messages related to
23663 reading of COFF/PE exported symbols.
23664 @item set debug notification
23665 @cindex remote async notification debugging info
23666 Turn on or off debugging messages about remote async notification.
23667 The default is off.
23668 @item show debug notification
23669 Displays the current state of remote async notification debugging messages.
23670 @item set debug observer
23671 @cindex observer debugging info
23672 Turns on or off display of @value{GDBN} observer debugging. This
23673 includes info such as the notification of observable events.
23674 @item show debug observer
23675 Displays the current state of observer debugging.
23676 @item set debug overload
23677 @cindex C@t{++} overload debugging info
23678 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23679 info. This includes info such as ranking of functions, etc. The default
23681 @item show debug overload
23682 Displays the current state of displaying @value{GDBN} C@t{++} overload
23684 @cindex expression parser, debugging info
23685 @cindex debug expression parser
23686 @item set debug parser
23687 Turns on or off the display of expression parser debugging output.
23688 Internally, this sets the @code{yydebug} variable in the expression
23689 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23690 details. The default is off.
23691 @item show debug parser
23692 Show the current state of expression parser debugging.
23693 @cindex packets, reporting on stdout
23694 @cindex serial connections, debugging
23695 @cindex debug remote protocol
23696 @cindex remote protocol debugging
23697 @cindex display remote packets
23698 @item set debug remote
23699 Turns on or off display of reports on all packets sent back and forth across
23700 the serial line to the remote machine. The info is printed on the
23701 @value{GDBN} standard output stream. The default is off.
23702 @item show debug remote
23703 Displays the state of display of remote packets.
23704 @item set debug serial
23705 Turns on or off display of @value{GDBN} serial debugging info. The
23707 @item show debug serial
23708 Displays the current state of displaying @value{GDBN} serial debugging
23710 @item set debug solib-frv
23711 @cindex FR-V shared-library debugging
23712 Turn on or off debugging messages for FR-V shared-library code.
23713 @item show debug solib-frv
23714 Display the current state of FR-V shared-library code debugging
23716 @item set debug symbol-lookup
23717 @cindex symbol lookup
23718 Turns on or off display of debugging messages related to symbol lookup.
23719 The default is 0 (off).
23720 A value of 1 provides basic information.
23721 A value greater than 1 provides more verbose information.
23722 @item show debug symbol-lookup
23723 Show the current state of symbol lookup debugging messages.
23724 @item set debug symfile
23725 @cindex symbol file functions
23726 Turns on or off display of debugging messages related to symbol file functions.
23727 The default is off. @xref{Files}.
23728 @item show debug symfile
23729 Show the current state of symbol file debugging messages.
23730 @item set debug symtab-create
23731 @cindex symbol table creation
23732 Turns on or off display of debugging messages related to symbol table creation.
23733 The default is 0 (off).
23734 A value of 1 provides basic information.
23735 A value greater than 1 provides more verbose information.
23736 @item show debug symtab-create
23737 Show the current state of symbol table creation debugging.
23738 @item set debug target
23739 @cindex target debugging info
23740 Turns on or off display of @value{GDBN} target debugging info. This info
23741 includes what is going on at the target level of GDB, as it happens. The
23742 default is 0. Set it to 1 to track events, and to 2 to also track the
23743 value of large memory transfers.
23744 @item show debug target
23745 Displays the current state of displaying @value{GDBN} target debugging
23747 @item set debug timestamp
23748 @cindex timestampping debugging info
23749 Turns on or off display of timestamps with @value{GDBN} debugging info.
23750 When enabled, seconds and microseconds are displayed before each debugging
23752 @item show debug timestamp
23753 Displays the current state of displaying timestamps with @value{GDBN}
23755 @item set debug varobj
23756 @cindex variable object debugging info
23757 Turns on or off display of @value{GDBN} variable object debugging
23758 info. The default is off.
23759 @item show debug varobj
23760 Displays the current state of displaying @value{GDBN} variable object
23762 @item set debug xml
23763 @cindex XML parser debugging
23764 Turn on or off debugging messages for built-in XML parsers.
23765 @item show debug xml
23766 Displays the current state of XML debugging messages.
23769 @node Other Misc Settings
23770 @section Other Miscellaneous Settings
23771 @cindex miscellaneous settings
23774 @kindex set interactive-mode
23775 @item set interactive-mode
23776 If @code{on}, forces @value{GDBN} to assume that GDB was started
23777 in a terminal. In practice, this means that @value{GDBN} should wait
23778 for the user to answer queries generated by commands entered at
23779 the command prompt. If @code{off}, forces @value{GDBN} to operate
23780 in the opposite mode, and it uses the default answers to all queries.
23781 If @code{auto} (the default), @value{GDBN} tries to determine whether
23782 its standard input is a terminal, and works in interactive-mode if it
23783 is, non-interactively otherwise.
23785 In the vast majority of cases, the debugger should be able to guess
23786 correctly which mode should be used. But this setting can be useful
23787 in certain specific cases, such as running a MinGW @value{GDBN}
23788 inside a cygwin window.
23790 @kindex show interactive-mode
23791 @item show interactive-mode
23792 Displays whether the debugger is operating in interactive mode or not.
23795 @node Extending GDB
23796 @chapter Extending @value{GDBN}
23797 @cindex extending GDB
23799 @value{GDBN} provides several mechanisms for extension.
23800 @value{GDBN} also provides the ability to automatically load
23801 extensions when it reads a file for debugging. This allows the
23802 user to automatically customize @value{GDBN} for the program
23806 * Sequences:: Canned Sequences of @value{GDBN} Commands
23807 * Python:: Extending @value{GDBN} using Python
23808 * Guile:: Extending @value{GDBN} using Guile
23809 * Auto-loading extensions:: Automatically loading extensions
23810 * Multiple Extension Languages:: Working with multiple extension languages
23811 * Aliases:: Creating new spellings of existing commands
23814 To facilitate the use of extension languages, @value{GDBN} is capable
23815 of evaluating the contents of a file. When doing so, @value{GDBN}
23816 can recognize which extension language is being used by looking at
23817 the filename extension. Files with an unrecognized filename extension
23818 are always treated as a @value{GDBN} Command Files.
23819 @xref{Command Files,, Command files}.
23821 You can control how @value{GDBN} evaluates these files with the following
23825 @kindex set script-extension
23826 @kindex show script-extension
23827 @item set script-extension off
23828 All scripts are always evaluated as @value{GDBN} Command Files.
23830 @item set script-extension soft
23831 The debugger determines the scripting language based on filename
23832 extension. If this scripting language is supported, @value{GDBN}
23833 evaluates the script using that language. Otherwise, it evaluates
23834 the file as a @value{GDBN} Command File.
23836 @item set script-extension strict
23837 The debugger determines the scripting language based on filename
23838 extension, and evaluates the script using that language. If the
23839 language is not supported, then the evaluation fails.
23841 @item show script-extension
23842 Display the current value of the @code{script-extension} option.
23847 @section Canned Sequences of Commands
23849 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23850 Command Lists}), @value{GDBN} provides two ways to store sequences of
23851 commands for execution as a unit: user-defined commands and command
23855 * Define:: How to define your own commands
23856 * Hooks:: Hooks for user-defined commands
23857 * Command Files:: How to write scripts of commands to be stored in a file
23858 * Output:: Commands for controlled output
23859 * Auto-loading sequences:: Controlling auto-loaded command files
23863 @subsection User-defined Commands
23865 @cindex user-defined command
23866 @cindex arguments, to user-defined commands
23867 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23868 which you assign a new name as a command. This is done with the
23869 @code{define} command. User commands may accept up to 10 arguments
23870 separated by whitespace. Arguments are accessed within the user command
23871 via @code{$arg0@dots{}$arg9}. A trivial example:
23875 print $arg0 + $arg1 + $arg2
23880 To execute the command use:
23887 This defines the command @code{adder}, which prints the sum of
23888 its three arguments. Note the arguments are text substitutions, so they may
23889 reference variables, use complex expressions, or even perform inferior
23892 @cindex argument count in user-defined commands
23893 @cindex how many arguments (user-defined commands)
23894 In addition, @code{$argc} may be used to find out how many arguments have
23895 been passed. This expands to a number in the range 0@dots{}10.
23900 print $arg0 + $arg1
23903 print $arg0 + $arg1 + $arg2
23911 @item define @var{commandname}
23912 Define a command named @var{commandname}. If there is already a command
23913 by that name, you are asked to confirm that you want to redefine it.
23914 The argument @var{commandname} may be a bare command name consisting of letters,
23915 numbers, dashes, and underscores. It may also start with any predefined
23916 prefix command. For example, @samp{define target my-target} creates
23917 a user-defined @samp{target my-target} command.
23919 The definition of the command is made up of other @value{GDBN} command lines,
23920 which are given following the @code{define} command. The end of these
23921 commands is marked by a line containing @code{end}.
23924 @kindex end@r{ (user-defined commands)}
23925 @item document @var{commandname}
23926 Document the user-defined command @var{commandname}, so that it can be
23927 accessed by @code{help}. The command @var{commandname} must already be
23928 defined. This command reads lines of documentation just as @code{define}
23929 reads the lines of the command definition, ending with @code{end}.
23930 After the @code{document} command is finished, @code{help} on command
23931 @var{commandname} displays the documentation you have written.
23933 You may use the @code{document} command again to change the
23934 documentation of a command. Redefining the command with @code{define}
23935 does not change the documentation.
23937 @kindex dont-repeat
23938 @cindex don't repeat command
23940 Used inside a user-defined command, this tells @value{GDBN} that this
23941 command should not be repeated when the user hits @key{RET}
23942 (@pxref{Command Syntax, repeat last command}).
23944 @kindex help user-defined
23945 @item help user-defined
23946 List all user-defined commands and all python commands defined in class
23947 COMAND_USER. The first line of the documentation or docstring is
23952 @itemx show user @var{commandname}
23953 Display the @value{GDBN} commands used to define @var{commandname} (but
23954 not its documentation). If no @var{commandname} is given, display the
23955 definitions for all user-defined commands.
23956 This does not work for user-defined python commands.
23958 @cindex infinite recursion in user-defined commands
23959 @kindex show max-user-call-depth
23960 @kindex set max-user-call-depth
23961 @item show max-user-call-depth
23962 @itemx set max-user-call-depth
23963 The value of @code{max-user-call-depth} controls how many recursion
23964 levels are allowed in user-defined commands before @value{GDBN} suspects an
23965 infinite recursion and aborts the command.
23966 This does not apply to user-defined python commands.
23969 In addition to the above commands, user-defined commands frequently
23970 use control flow commands, described in @ref{Command Files}.
23972 When user-defined commands are executed, the
23973 commands of the definition are not printed. An error in any command
23974 stops execution of the user-defined command.
23976 If used interactively, commands that would ask for confirmation proceed
23977 without asking when used inside a user-defined command. Many @value{GDBN}
23978 commands that normally print messages to say what they are doing omit the
23979 messages when used in a user-defined command.
23982 @subsection User-defined Command Hooks
23983 @cindex command hooks
23984 @cindex hooks, for commands
23985 @cindex hooks, pre-command
23988 You may define @dfn{hooks}, which are a special kind of user-defined
23989 command. Whenever you run the command @samp{foo}, if the user-defined
23990 command @samp{hook-foo} exists, it is executed (with no arguments)
23991 before that command.
23993 @cindex hooks, post-command
23995 A hook may also be defined which is run after the command you executed.
23996 Whenever you run the command @samp{foo}, if the user-defined command
23997 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23998 that command. Post-execution hooks may exist simultaneously with
23999 pre-execution hooks, for the same command.
24001 It is valid for a hook to call the command which it hooks. If this
24002 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24004 @c It would be nice if hookpost could be passed a parameter indicating
24005 @c if the command it hooks executed properly or not. FIXME!
24007 @kindex stop@r{, a pseudo-command}
24008 In addition, a pseudo-command, @samp{stop} exists. Defining
24009 (@samp{hook-stop}) makes the associated commands execute every time
24010 execution stops in your program: before breakpoint commands are run,
24011 displays are printed, or the stack frame is printed.
24013 For example, to ignore @code{SIGALRM} signals while
24014 single-stepping, but treat them normally during normal execution,
24019 handle SIGALRM nopass
24023 handle SIGALRM pass
24026 define hook-continue
24027 handle SIGALRM pass
24031 As a further example, to hook at the beginning and end of the @code{echo}
24032 command, and to add extra text to the beginning and end of the message,
24040 define hookpost-echo
24044 (@value{GDBP}) echo Hello World
24045 <<<---Hello World--->>>
24050 You can define a hook for any single-word command in @value{GDBN}, but
24051 not for command aliases; you should define a hook for the basic command
24052 name, e.g.@: @code{backtrace} rather than @code{bt}.
24053 @c FIXME! So how does Joe User discover whether a command is an alias
24055 You can hook a multi-word command by adding @code{hook-} or
24056 @code{hookpost-} to the last word of the command, e.g.@:
24057 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24059 If an error occurs during the execution of your hook, execution of
24060 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24061 (before the command that you actually typed had a chance to run).
24063 If you try to define a hook which does not match any known command, you
24064 get a warning from the @code{define} command.
24066 @node Command Files
24067 @subsection Command Files
24069 @cindex command files
24070 @cindex scripting commands
24071 A command file for @value{GDBN} is a text file made of lines that are
24072 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24073 also be included. An empty line in a command file does nothing; it
24074 does not mean to repeat the last command, as it would from the
24077 You can request the execution of a command file with the @code{source}
24078 command. Note that the @code{source} command is also used to evaluate
24079 scripts that are not Command Files. The exact behavior can be configured
24080 using the @code{script-extension} setting.
24081 @xref{Extending GDB,, Extending GDB}.
24085 @cindex execute commands from a file
24086 @item source [-s] [-v] @var{filename}
24087 Execute the command file @var{filename}.
24090 The lines in a command file are generally executed sequentially,
24091 unless the order of execution is changed by one of the
24092 @emph{flow-control commands} described below. The commands are not
24093 printed as they are executed. An error in any command terminates
24094 execution of the command file and control is returned to the console.
24096 @value{GDBN} first searches for @var{filename} in the current directory.
24097 If the file is not found there, and @var{filename} does not specify a
24098 directory, then @value{GDBN} also looks for the file on the source search path
24099 (specified with the @samp{directory} command);
24100 except that @file{$cdir} is not searched because the compilation directory
24101 is not relevant to scripts.
24103 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24104 on the search path even if @var{filename} specifies a directory.
24105 The search is done by appending @var{filename} to each element of the
24106 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24107 and the search path contains @file{/home/user} then @value{GDBN} will
24108 look for the script @file{/home/user/mylib/myscript}.
24109 The search is also done if @var{filename} is an absolute path.
24110 For example, if @var{filename} is @file{/tmp/myscript} and
24111 the search path contains @file{/home/user} then @value{GDBN} will
24112 look for the script @file{/home/user/tmp/myscript}.
24113 For DOS-like systems, if @var{filename} contains a drive specification,
24114 it is stripped before concatenation. For example, if @var{filename} is
24115 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24116 will look for the script @file{c:/tmp/myscript}.
24118 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24119 each command as it is executed. The option must be given before
24120 @var{filename}, and is interpreted as part of the filename anywhere else.
24122 Commands that would ask for confirmation if used interactively proceed
24123 without asking when used in a command file. Many @value{GDBN} commands that
24124 normally print messages to say what they are doing omit the messages
24125 when called from command files.
24127 @value{GDBN} also accepts command input from standard input. In this
24128 mode, normal output goes to standard output and error output goes to
24129 standard error. Errors in a command file supplied on standard input do
24130 not terminate execution of the command file---execution continues with
24134 gdb < cmds > log 2>&1
24137 (The syntax above will vary depending on the shell used.) This example
24138 will execute commands from the file @file{cmds}. All output and errors
24139 would be directed to @file{log}.
24141 Since commands stored on command files tend to be more general than
24142 commands typed interactively, they frequently need to deal with
24143 complicated situations, such as different or unexpected values of
24144 variables and symbols, changes in how the program being debugged is
24145 built, etc. @value{GDBN} provides a set of flow-control commands to
24146 deal with these complexities. Using these commands, you can write
24147 complex scripts that loop over data structures, execute commands
24148 conditionally, etc.
24155 This command allows to include in your script conditionally executed
24156 commands. The @code{if} command takes a single argument, which is an
24157 expression to evaluate. It is followed by a series of commands that
24158 are executed only if the expression is true (its value is nonzero).
24159 There can then optionally be an @code{else} line, followed by a series
24160 of commands that are only executed if the expression was false. The
24161 end of the list is marked by a line containing @code{end}.
24165 This command allows to write loops. Its syntax is similar to
24166 @code{if}: the command takes a single argument, which is an expression
24167 to evaluate, and must be followed by the commands to execute, one per
24168 line, terminated by an @code{end}. These commands are called the
24169 @dfn{body} of the loop. The commands in the body of @code{while} are
24170 executed repeatedly as long as the expression evaluates to true.
24174 This command exits the @code{while} loop in whose body it is included.
24175 Execution of the script continues after that @code{while}s @code{end}
24178 @kindex loop_continue
24179 @item loop_continue
24180 This command skips the execution of the rest of the body of commands
24181 in the @code{while} loop in whose body it is included. Execution
24182 branches to the beginning of the @code{while} loop, where it evaluates
24183 the controlling expression.
24185 @kindex end@r{ (if/else/while commands)}
24187 Terminate the block of commands that are the body of @code{if},
24188 @code{else}, or @code{while} flow-control commands.
24193 @subsection Commands for Controlled Output
24195 During the execution of a command file or a user-defined command, normal
24196 @value{GDBN} output is suppressed; the only output that appears is what is
24197 explicitly printed by the commands in the definition. This section
24198 describes three commands useful for generating exactly the output you
24203 @item echo @var{text}
24204 @c I do not consider backslash-space a standard C escape sequence
24205 @c because it is not in ANSI.
24206 Print @var{text}. Nonprinting characters can be included in
24207 @var{text} using C escape sequences, such as @samp{\n} to print a
24208 newline. @strong{No newline is printed unless you specify one.}
24209 In addition to the standard C escape sequences, a backslash followed
24210 by a space stands for a space. This is useful for displaying a
24211 string with spaces at the beginning or the end, since leading and
24212 trailing spaces are otherwise trimmed from all arguments.
24213 To print @samp{@w{ }and foo =@w{ }}, use the command
24214 @samp{echo \@w{ }and foo = \@w{ }}.
24216 A backslash at the end of @var{text} can be used, as in C, to continue
24217 the command onto subsequent lines. For example,
24220 echo This is some text\n\
24221 which is continued\n\
24222 onto several lines.\n
24225 produces the same output as
24228 echo This is some text\n
24229 echo which is continued\n
24230 echo onto several lines.\n
24234 @item output @var{expression}
24235 Print the value of @var{expression} and nothing but that value: no
24236 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24237 value history either. @xref{Expressions, ,Expressions}, for more information
24240 @item output/@var{fmt} @var{expression}
24241 Print the value of @var{expression} in format @var{fmt}. You can use
24242 the same formats as for @code{print}. @xref{Output Formats,,Output
24243 Formats}, for more information.
24246 @item printf @var{template}, @var{expressions}@dots{}
24247 Print the values of one or more @var{expressions} under the control of
24248 the string @var{template}. To print several values, make
24249 @var{expressions} be a comma-separated list of individual expressions,
24250 which may be either numbers or pointers. Their values are printed as
24251 specified by @var{template}, exactly as a C program would do by
24252 executing the code below:
24255 printf (@var{template}, @var{expressions}@dots{});
24258 As in @code{C} @code{printf}, ordinary characters in @var{template}
24259 are printed verbatim, while @dfn{conversion specification} introduced
24260 by the @samp{%} character cause subsequent @var{expressions} to be
24261 evaluated, their values converted and formatted according to type and
24262 style information encoded in the conversion specifications, and then
24265 For example, you can print two values in hex like this:
24268 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24271 @code{printf} supports all the standard @code{C} conversion
24272 specifications, including the flags and modifiers between the @samp{%}
24273 character and the conversion letter, with the following exceptions:
24277 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24280 The modifier @samp{*} is not supported for specifying precision or
24284 The @samp{'} flag (for separation of digits into groups according to
24285 @code{LC_NUMERIC'}) is not supported.
24288 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24292 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24295 The conversion letters @samp{a} and @samp{A} are not supported.
24299 Note that the @samp{ll} type modifier is supported only if the
24300 underlying @code{C} implementation used to build @value{GDBN} supports
24301 the @code{long long int} type, and the @samp{L} type modifier is
24302 supported only if @code{long double} type is available.
24304 As in @code{C}, @code{printf} supports simple backslash-escape
24305 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24306 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24307 single character. Octal and hexadecimal escape sequences are not
24310 Additionally, @code{printf} supports conversion specifications for DFP
24311 (@dfn{Decimal Floating Point}) types using the following length modifiers
24312 together with a floating point specifier.
24317 @samp{H} for printing @code{Decimal32} types.
24320 @samp{D} for printing @code{Decimal64} types.
24323 @samp{DD} for printing @code{Decimal128} types.
24326 If the underlying @code{C} implementation used to build @value{GDBN} has
24327 support for the three length modifiers for DFP types, other modifiers
24328 such as width and precision will also be available for @value{GDBN} to use.
24330 In case there is no such @code{C} support, no additional modifiers will be
24331 available and the value will be printed in the standard way.
24333 Here's an example of printing DFP types using the above conversion letters:
24335 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24339 @item eval @var{template}, @var{expressions}@dots{}
24340 Convert the values of one or more @var{expressions} under the control of
24341 the string @var{template} to a command line, and call it.
24345 @node Auto-loading sequences
24346 @subsection Controlling auto-loading native @value{GDBN} scripts
24347 @cindex native script auto-loading
24349 When a new object file is read (for example, due to the @code{file}
24350 command, or because the inferior has loaded a shared library),
24351 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24352 @xref{Auto-loading extensions}.
24354 Auto-loading can be enabled or disabled,
24355 and the list of auto-loaded scripts can be printed.
24358 @anchor{set auto-load gdb-scripts}
24359 @kindex set auto-load gdb-scripts
24360 @item set auto-load gdb-scripts [on|off]
24361 Enable or disable the auto-loading of canned sequences of commands scripts.
24363 @anchor{show auto-load gdb-scripts}
24364 @kindex show auto-load gdb-scripts
24365 @item show auto-load gdb-scripts
24366 Show whether auto-loading of canned sequences of commands scripts is enabled or
24369 @anchor{info auto-load gdb-scripts}
24370 @kindex info auto-load gdb-scripts
24371 @cindex print list of auto-loaded canned sequences of commands scripts
24372 @item info auto-load gdb-scripts [@var{regexp}]
24373 Print the list of all canned sequences of commands scripts that @value{GDBN}
24377 If @var{regexp} is supplied only canned sequences of commands scripts with
24378 matching names are printed.
24380 @c Python docs live in a separate file.
24381 @include python.texi
24383 @c Guile docs live in a separate file.
24384 @include guile.texi
24386 @node Auto-loading extensions
24387 @section Auto-loading extensions
24388 @cindex auto-loading extensions
24390 @value{GDBN} provides two mechanisms for automatically loading extensions
24391 when a new object file is read (for example, due to the @code{file}
24392 command, or because the inferior has loaded a shared library):
24393 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24394 section of modern file formats like ELF.
24397 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24398 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24399 * Which flavor to choose?::
24402 The auto-loading feature is useful for supplying application-specific
24403 debugging commands and features.
24405 Auto-loading can be enabled or disabled,
24406 and the list of auto-loaded scripts can be printed.
24407 See the @samp{auto-loading} section of each extension language
24408 for more information.
24409 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24410 For Python files see @ref{Python Auto-loading}.
24412 Note that loading of this script file also requires accordingly configured
24413 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24415 @node objfile-gdbdotext file
24416 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24417 @cindex @file{@var{objfile}-gdb.gdb}
24418 @cindex @file{@var{objfile}-gdb.py}
24419 @cindex @file{@var{objfile}-gdb.scm}
24421 When a new object file is read, @value{GDBN} looks for a file named
24422 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24423 where @var{objfile} is the object file's name and
24424 where @var{ext} is the file extension for the extension language:
24427 @item @file{@var{objfile}-gdb.gdb}
24428 GDB's own command language
24429 @item @file{@var{objfile}-gdb.py}
24431 @item @file{@var{objfile}-gdb.scm}
24435 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24436 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24437 components, and appending the @file{-gdb.@var{ext}} suffix.
24438 If this file exists and is readable, @value{GDBN} will evaluate it as a
24439 script in the specified extension language.
24441 If this file does not exist, then @value{GDBN} will look for
24442 @var{script-name} file in all of the directories as specified below.
24444 Note that loading of these files requires an accordingly configured
24445 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24447 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24448 scripts normally according to its @file{.exe} filename. But if no scripts are
24449 found @value{GDBN} also tries script filenames matching the object file without
24450 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24451 is attempted on any platform. This makes the script filenames compatible
24452 between Unix and MS-Windows hosts.
24455 @anchor{set auto-load scripts-directory}
24456 @kindex set auto-load scripts-directory
24457 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24458 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24459 may be delimited by the host platform path separator in use
24460 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24462 Each entry here needs to be covered also by the security setting
24463 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24465 @anchor{with-auto-load-dir}
24466 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24467 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24468 configuration option @option{--with-auto-load-dir}.
24470 Any reference to @file{$debugdir} will get replaced by
24471 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24472 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24473 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24474 @file{$datadir} must be placed as a directory component --- either alone or
24475 delimited by @file{/} or @file{\} directory separators, depending on the host
24478 The list of directories uses path separator (@samp{:} on GNU and Unix
24479 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24480 to the @env{PATH} environment variable.
24482 @anchor{show auto-load scripts-directory}
24483 @kindex show auto-load scripts-directory
24484 @item show auto-load scripts-directory
24485 Show @value{GDBN} auto-loaded scripts location.
24487 @anchor{add-auto-load-scripts-directory}
24488 @kindex add-auto-load-scripts-directory
24489 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24490 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24491 Multiple entries may be delimited by the host platform path separator in use.
24494 @value{GDBN} does not track which files it has already auto-loaded this way.
24495 @value{GDBN} will load the associated script every time the corresponding
24496 @var{objfile} is opened.
24497 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24498 is evaluated more than once.
24500 @node dotdebug_gdb_scripts section
24501 @subsection The @code{.debug_gdb_scripts} section
24502 @cindex @code{.debug_gdb_scripts} section
24504 For systems using file formats like ELF and COFF,
24505 when @value{GDBN} loads a new object file
24506 it will look for a special section named @code{.debug_gdb_scripts}.
24507 If this section exists, its contents is a list of null-terminated entries
24508 specifying scripts to load. Each entry begins with a non-null prefix byte that
24509 specifies the kind of entry, typically the extension language and whether the
24510 script is in a file or inlined in @code{.debug_gdb_scripts}.
24512 The following entries are supported:
24515 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24516 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24517 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24518 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24521 @subsubsection Script File Entries
24523 If the entry specifies a file, @value{GDBN} will look for the file first
24524 in the current directory and then along the source search path
24525 (@pxref{Source Path, ,Specifying Source Directories}),
24526 except that @file{$cdir} is not searched, since the compilation
24527 directory is not relevant to scripts.
24529 File entries can be placed in section @code{.debug_gdb_scripts} with,
24530 for example, this GCC macro for Python scripts.
24533 /* Note: The "MS" section flags are to remove duplicates. */
24534 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24536 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24537 .byte 1 /* Python */\n\
24538 .asciz \"" script_name "\"\n\
24544 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24545 Then one can reference the macro in a header or source file like this:
24548 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24551 The script name may include directories if desired.
24553 Note that loading of this script file also requires accordingly configured
24554 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24556 If the macro invocation is put in a header, any application or library
24557 using this header will get a reference to the specified script,
24558 and with the use of @code{"MS"} attributes on the section, the linker
24559 will remove duplicates.
24561 @subsubsection Script Text Entries
24563 Script text entries allow to put the executable script in the entry
24564 itself instead of loading it from a file.
24565 The first line of the entry, everything after the prefix byte and up to
24566 the first newline (@code{0xa}) character, is the script name, and must not
24567 contain any kind of space character, e.g., spaces or tabs.
24568 The rest of the entry, up to the trailing null byte, is the script to
24569 execute in the specified language. The name needs to be unique among
24570 all script names, as @value{GDBN} executes each script only once based
24573 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24577 #include "symcat.h"
24578 #include "gdb/section-scripts.h"
24580 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24581 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24582 ".ascii \"gdb.inlined-script\\n\"\n"
24583 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24584 ".ascii \" def __init__ (self):\\n\"\n"
24585 ".ascii \" super (test_cmd, self).__init__ ("
24586 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24587 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24588 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24589 ".ascii \"test_cmd ()\\n\"\n"
24595 Loading of inlined scripts requires a properly configured
24596 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24597 The path to specify in @code{auto-load safe-path} is the path of the file
24598 containing the @code{.debug_gdb_scripts} section.
24600 @node Which flavor to choose?
24601 @subsection Which flavor to choose?
24603 Given the multiple ways of auto-loading extensions, it might not always
24604 be clear which one to choose. This section provides some guidance.
24607 Benefits of the @file{-gdb.@var{ext}} way:
24611 Can be used with file formats that don't support multiple sections.
24614 Ease of finding scripts for public libraries.
24616 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24617 in the source search path.
24618 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24619 isn't a source directory in which to find the script.
24622 Doesn't require source code additions.
24626 Benefits of the @code{.debug_gdb_scripts} way:
24630 Works with static linking.
24632 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24633 trigger their loading. When an application is statically linked the only
24634 objfile available is the executable, and it is cumbersome to attach all the
24635 scripts from all the input libraries to the executable's
24636 @file{-gdb.@var{ext}} script.
24639 Works with classes that are entirely inlined.
24641 Some classes can be entirely inlined, and thus there may not be an associated
24642 shared library to attach a @file{-gdb.@var{ext}} script to.
24645 Scripts needn't be copied out of the source tree.
24647 In some circumstances, apps can be built out of large collections of internal
24648 libraries, and the build infrastructure necessary to install the
24649 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24650 cumbersome. It may be easier to specify the scripts in the
24651 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24652 top of the source tree to the source search path.
24655 @node Multiple Extension Languages
24656 @section Multiple Extension Languages
24658 The Guile and Python extension languages do not share any state,
24659 and generally do not interfere with each other.
24660 There are some things to be aware of, however.
24662 @subsection Python comes first
24664 Python was @value{GDBN}'s first extension language, and to avoid breaking
24665 existing behaviour Python comes first. This is generally solved by the
24666 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24667 extension languages, and when it makes a call to an extension language,
24668 (say to pretty-print a value), it tries each in turn until an extension
24669 language indicates it has performed the request (e.g., has returned the
24670 pretty-printed form of a value).
24671 This extends to errors while performing such requests: If an error happens
24672 while, for example, trying to pretty-print an object then the error is
24673 reported and any following extension languages are not tried.
24676 @section Creating new spellings of existing commands
24677 @cindex aliases for commands
24679 It is often useful to define alternate spellings of existing commands.
24680 For example, if a new @value{GDBN} command defined in Python has
24681 a long name to type, it is handy to have an abbreviated version of it
24682 that involves less typing.
24684 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24685 of the @samp{step} command even though it is otherwise an ambiguous
24686 abbreviation of other commands like @samp{set} and @samp{show}.
24688 Aliases are also used to provide shortened or more common versions
24689 of multi-word commands. For example, @value{GDBN} provides the
24690 @samp{tty} alias of the @samp{set inferior-tty} command.
24692 You can define a new alias with the @samp{alias} command.
24697 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24701 @var{ALIAS} specifies the name of the new alias.
24702 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24705 @var{COMMAND} specifies the name of an existing command
24706 that is being aliased.
24708 The @samp{-a} option specifies that the new alias is an abbreviation
24709 of the command. Abbreviations are not shown in command
24710 lists displayed by the @samp{help} command.
24712 The @samp{--} option specifies the end of options,
24713 and is useful when @var{ALIAS} begins with a dash.
24715 Here is a simple example showing how to make an abbreviation
24716 of a command so that there is less to type.
24717 Suppose you were tired of typing @samp{disas}, the current
24718 shortest unambiguous abbreviation of the @samp{disassemble} command
24719 and you wanted an even shorter version named @samp{di}.
24720 The following will accomplish this.
24723 (gdb) alias -a di = disas
24726 Note that aliases are different from user-defined commands.
24727 With a user-defined command, you also need to write documentation
24728 for it with the @samp{document} command.
24729 An alias automatically picks up the documentation of the existing command.
24731 Here is an example where we make @samp{elms} an abbreviation of
24732 @samp{elements} in the @samp{set print elements} command.
24733 This is to show that you can make an abbreviation of any part
24737 (gdb) alias -a set print elms = set print elements
24738 (gdb) alias -a show print elms = show print elements
24739 (gdb) set p elms 20
24741 Limit on string chars or array elements to print is 200.
24744 Note that if you are defining an alias of a @samp{set} command,
24745 and you want to have an alias for the corresponding @samp{show}
24746 command, then you need to define the latter separately.
24748 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24749 @var{ALIAS}, just as they are normally.
24752 (gdb) alias -a set pr elms = set p ele
24755 Finally, here is an example showing the creation of a one word
24756 alias for a more complex command.
24757 This creates alias @samp{spe} of the command @samp{set print elements}.
24760 (gdb) alias spe = set print elements
24765 @chapter Command Interpreters
24766 @cindex command interpreters
24768 @value{GDBN} supports multiple command interpreters, and some command
24769 infrastructure to allow users or user interface writers to switch
24770 between interpreters or run commands in other interpreters.
24772 @value{GDBN} currently supports two command interpreters, the console
24773 interpreter (sometimes called the command-line interpreter or @sc{cli})
24774 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24775 describes both of these interfaces in great detail.
24777 By default, @value{GDBN} will start with the console interpreter.
24778 However, the user may choose to start @value{GDBN} with another
24779 interpreter by specifying the @option{-i} or @option{--interpreter}
24780 startup options. Defined interpreters include:
24784 @cindex console interpreter
24785 The traditional console or command-line interpreter. This is the most often
24786 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24787 @value{GDBN} will use this interpreter.
24790 @cindex mi interpreter
24791 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24792 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24793 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24797 @cindex mi2 interpreter
24798 The current @sc{gdb/mi} interface.
24801 @cindex mi1 interpreter
24802 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24806 @cindex invoke another interpreter
24807 The interpreter being used by @value{GDBN} may not be dynamically
24808 switched at runtime. Although possible, this could lead to a very
24809 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24810 enters the command "interpreter-set console" in a console view,
24811 @value{GDBN} would switch to using the console interpreter, rendering
24812 the IDE inoperable!
24814 @kindex interpreter-exec
24815 Although you may only choose a single interpreter at startup, you may execute
24816 commands in any interpreter from the current interpreter using the appropriate
24817 command. If you are running the console interpreter, simply use the
24818 @code{interpreter-exec} command:
24821 interpreter-exec mi "-data-list-register-names"
24824 @sc{gdb/mi} has a similar command, although it is only available in versions of
24825 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24828 @chapter @value{GDBN} Text User Interface
24830 @cindex Text User Interface
24833 * TUI Overview:: TUI overview
24834 * TUI Keys:: TUI key bindings
24835 * TUI Single Key Mode:: TUI single key mode
24836 * TUI Commands:: TUI-specific commands
24837 * TUI Configuration:: TUI configuration variables
24840 The @value{GDBN} Text User Interface (TUI) is a terminal
24841 interface which uses the @code{curses} library to show the source
24842 file, the assembly output, the program registers and @value{GDBN}
24843 commands in separate text windows. The TUI mode is supported only
24844 on platforms where a suitable version of the @code{curses} library
24847 The TUI mode is enabled by default when you invoke @value{GDBN} as
24848 @samp{@value{GDBP} -tui}.
24849 You can also switch in and out of TUI mode while @value{GDBN} runs by
24850 using various TUI commands and key bindings, such as @command{tui
24851 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24852 @ref{TUI Keys, ,TUI Key Bindings}.
24855 @section TUI Overview
24857 In TUI mode, @value{GDBN} can display several text windows:
24861 This window is the @value{GDBN} command window with the @value{GDBN}
24862 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24863 managed using readline.
24866 The source window shows the source file of the program. The current
24867 line and active breakpoints are displayed in this window.
24870 The assembly window shows the disassembly output of the program.
24873 This window shows the processor registers. Registers are highlighted
24874 when their values change.
24877 The source and assembly windows show the current program position
24878 by highlighting the current line and marking it with a @samp{>} marker.
24879 Breakpoints are indicated with two markers. The first marker
24880 indicates the breakpoint type:
24884 Breakpoint which was hit at least once.
24887 Breakpoint which was never hit.
24890 Hardware breakpoint which was hit at least once.
24893 Hardware breakpoint which was never hit.
24896 The second marker indicates whether the breakpoint is enabled or not:
24900 Breakpoint is enabled.
24903 Breakpoint is disabled.
24906 The source, assembly and register windows are updated when the current
24907 thread changes, when the frame changes, or when the program counter
24910 These windows are not all visible at the same time. The command
24911 window is always visible. The others can be arranged in several
24922 source and assembly,
24925 source and registers, or
24928 assembly and registers.
24931 A status line above the command window shows the following information:
24935 Indicates the current @value{GDBN} target.
24936 (@pxref{Targets, ,Specifying a Debugging Target}).
24939 Gives the current process or thread number.
24940 When no process is being debugged, this field is set to @code{No process}.
24943 Gives the current function name for the selected frame.
24944 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24945 When there is no symbol corresponding to the current program counter,
24946 the string @code{??} is displayed.
24949 Indicates the current line number for the selected frame.
24950 When the current line number is not known, the string @code{??} is displayed.
24953 Indicates the current program counter address.
24957 @section TUI Key Bindings
24958 @cindex TUI key bindings
24960 The TUI installs several key bindings in the readline keymaps
24961 @ifset SYSTEM_READLINE
24962 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24964 @ifclear SYSTEM_READLINE
24965 (@pxref{Command Line Editing}).
24967 The following key bindings are installed for both TUI mode and the
24968 @value{GDBN} standard mode.
24977 Enter or leave the TUI mode. When leaving the TUI mode,
24978 the curses window management stops and @value{GDBN} operates using
24979 its standard mode, writing on the terminal directly. When reentering
24980 the TUI mode, control is given back to the curses windows.
24981 The screen is then refreshed.
24985 Use a TUI layout with only one window. The layout will
24986 either be @samp{source} or @samp{assembly}. When the TUI mode
24987 is not active, it will switch to the TUI mode.
24989 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24993 Use a TUI layout with at least two windows. When the current
24994 layout already has two windows, the next layout with two windows is used.
24995 When a new layout is chosen, one window will always be common to the
24996 previous layout and the new one.
24998 Think of it as the Emacs @kbd{C-x 2} binding.
25002 Change the active window. The TUI associates several key bindings
25003 (like scrolling and arrow keys) with the active window. This command
25004 gives the focus to the next TUI window.
25006 Think of it as the Emacs @kbd{C-x o} binding.
25010 Switch in and out of the TUI SingleKey mode that binds single
25011 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25014 The following key bindings only work in the TUI mode:
25019 Scroll the active window one page up.
25023 Scroll the active window one page down.
25027 Scroll the active window one line up.
25031 Scroll the active window one line down.
25035 Scroll the active window one column left.
25039 Scroll the active window one column right.
25043 Refresh the screen.
25046 Because the arrow keys scroll the active window in the TUI mode, they
25047 are not available for their normal use by readline unless the command
25048 window has the focus. When another window is active, you must use
25049 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25050 and @kbd{C-f} to control the command window.
25052 @node TUI Single Key Mode
25053 @section TUI Single Key Mode
25054 @cindex TUI single key mode
25056 The TUI also provides a @dfn{SingleKey} mode, which binds several
25057 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25058 switch into this mode, where the following key bindings are used:
25061 @kindex c @r{(SingleKey TUI key)}
25065 @kindex d @r{(SingleKey TUI key)}
25069 @kindex f @r{(SingleKey TUI key)}
25073 @kindex n @r{(SingleKey TUI key)}
25077 @kindex q @r{(SingleKey TUI key)}
25079 exit the SingleKey mode.
25081 @kindex r @r{(SingleKey TUI key)}
25085 @kindex s @r{(SingleKey TUI key)}
25089 @kindex u @r{(SingleKey TUI key)}
25093 @kindex v @r{(SingleKey TUI key)}
25097 @kindex w @r{(SingleKey TUI key)}
25102 Other keys temporarily switch to the @value{GDBN} command prompt.
25103 The key that was pressed is inserted in the editing buffer so that
25104 it is possible to type most @value{GDBN} commands without interaction
25105 with the TUI SingleKey mode. Once the command is entered the TUI
25106 SingleKey mode is restored. The only way to permanently leave
25107 this mode is by typing @kbd{q} or @kbd{C-x s}.
25111 @section TUI-specific Commands
25112 @cindex TUI commands
25114 The TUI has specific commands to control the text windows.
25115 These commands are always available, even when @value{GDBN} is not in
25116 the TUI mode. When @value{GDBN} is in the standard mode, most
25117 of these commands will automatically switch to the TUI mode.
25119 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25120 terminal, or @value{GDBN} has been started with the machine interface
25121 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25122 these commands will fail with an error, because it would not be
25123 possible or desirable to enable curses window management.
25128 Activate TUI mode. The last active TUI window layout will be used if
25129 TUI mode has prevsiouly been used in the current debugging session,
25130 otherwise a default layout is used.
25133 @kindex tui disable
25134 Disable TUI mode, returning to the console interpreter.
25138 List and give the size of all displayed windows.
25140 @item layout @var{name}
25142 Changes which TUI windows are displayed. In each layout the command
25143 window is always displayed, the @var{name} parameter controls which
25144 additional windows are displayed, and can be any of the following:
25148 Display the next layout.
25151 Display the previous layout.
25154 Display the source and command windows.
25157 Display the assembly and command windows.
25160 Display the source, assembly, and command windows.
25163 When in @code{src} layout display the register, source, and command
25164 windows. When in @code{asm} or @code{split} layout display the
25165 register, assembler, and command windows.
25168 @item focus @var{name}
25170 Changes which TUI window is currently active for scrolling. The
25171 @var{name} parameter can be any of the following:
25175 Make the next window active for scrolling.
25178 Make the previous window active for scrolling.
25181 Make the source window active for scrolling.
25184 Make the assembly window active for scrolling.
25187 Make the register window active for scrolling.
25190 Make the command window active for scrolling.
25195 Refresh the screen. This is similar to typing @kbd{C-L}.
25197 @item tui reg @var{group}
25199 Changes the register group displayed in the tui register window to
25200 @var{group}. If the register window is not currently displayed this
25201 command will cause the register window to be displayed. The list of
25202 register groups, as well as their order is target specific. The
25203 following groups are available on most targets:
25206 Repeatedly selecting this group will cause the display to cycle
25207 through all of the available register groups.
25210 Repeatedly selecting this group will cause the display to cycle
25211 through all of the available register groups in the reverse order to
25215 Display the general registers.
25217 Display the floating point registers.
25219 Display the system registers.
25221 Display the vector registers.
25223 Display all registers.
25228 Update the source window and the current execution point.
25230 @item winheight @var{name} +@var{count}
25231 @itemx winheight @var{name} -@var{count}
25233 Change the height of the window @var{name} by @var{count}
25234 lines. Positive counts increase the height, while negative counts
25235 decrease it. The @var{name} parameter can be one of @code{src} (the
25236 source window), @code{cmd} (the command window), @code{asm} (the
25237 disassembly window), or @code{regs} (the register display window).
25239 @item tabset @var{nchars}
25241 Set the width of tab stops to be @var{nchars} characters. This
25242 setting affects the display of TAB characters in the source and
25246 @node TUI Configuration
25247 @section TUI Configuration Variables
25248 @cindex TUI configuration variables
25250 Several configuration variables control the appearance of TUI windows.
25253 @item set tui border-kind @var{kind}
25254 @kindex set tui border-kind
25255 Select the border appearance for the source, assembly and register windows.
25256 The possible values are the following:
25259 Use a space character to draw the border.
25262 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25265 Use the Alternate Character Set to draw the border. The border is
25266 drawn using character line graphics if the terminal supports them.
25269 @item set tui border-mode @var{mode}
25270 @kindex set tui border-mode
25271 @itemx set tui active-border-mode @var{mode}
25272 @kindex set tui active-border-mode
25273 Select the display attributes for the borders of the inactive windows
25274 or the active window. The @var{mode} can be one of the following:
25277 Use normal attributes to display the border.
25283 Use reverse video mode.
25286 Use half bright mode.
25288 @item half-standout
25289 Use half bright and standout mode.
25292 Use extra bright or bold mode.
25294 @item bold-standout
25295 Use extra bright or bold and standout mode.
25300 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25303 @cindex @sc{gnu} Emacs
25304 A special interface allows you to use @sc{gnu} Emacs to view (and
25305 edit) the source files for the program you are debugging with
25308 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25309 executable file you want to debug as an argument. This command starts
25310 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25311 created Emacs buffer.
25312 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25314 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25319 All ``terminal'' input and output goes through an Emacs buffer, called
25322 This applies both to @value{GDBN} commands and their output, and to the input
25323 and output done by the program you are debugging.
25325 This is useful because it means that you can copy the text of previous
25326 commands and input them again; you can even use parts of the output
25329 All the facilities of Emacs' Shell mode are available for interacting
25330 with your program. In particular, you can send signals the usual
25331 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25335 @value{GDBN} displays source code through Emacs.
25337 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25338 source file for that frame and puts an arrow (@samp{=>}) at the
25339 left margin of the current line. Emacs uses a separate buffer for
25340 source display, and splits the screen to show both your @value{GDBN} session
25343 Explicit @value{GDBN} @code{list} or search commands still produce output as
25344 usual, but you probably have no reason to use them from Emacs.
25347 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25348 a graphical mode, enabled by default, which provides further buffers
25349 that can control the execution and describe the state of your program.
25350 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25352 If you specify an absolute file name when prompted for the @kbd{M-x
25353 gdb} argument, then Emacs sets your current working directory to where
25354 your program resides. If you only specify the file name, then Emacs
25355 sets your current working directory to the directory associated
25356 with the previous buffer. In this case, @value{GDBN} may find your
25357 program by searching your environment's @code{PATH} variable, but on
25358 some operating systems it might not find the source. So, although the
25359 @value{GDBN} input and output session proceeds normally, the auxiliary
25360 buffer does not display the current source and line of execution.
25362 The initial working directory of @value{GDBN} is printed on the top
25363 line of the GUD buffer and this serves as a default for the commands
25364 that specify files for @value{GDBN} to operate on. @xref{Files,
25365 ,Commands to Specify Files}.
25367 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25368 need to call @value{GDBN} by a different name (for example, if you
25369 keep several configurations around, with different names) you can
25370 customize the Emacs variable @code{gud-gdb-command-name} to run the
25373 In the GUD buffer, you can use these special Emacs commands in
25374 addition to the standard Shell mode commands:
25378 Describe the features of Emacs' GUD Mode.
25381 Execute to another source line, like the @value{GDBN} @code{step} command; also
25382 update the display window to show the current file and location.
25385 Execute to next source line in this function, skipping all function
25386 calls, like the @value{GDBN} @code{next} command. Then update the display window
25387 to show the current file and location.
25390 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25391 display window accordingly.
25394 Execute until exit from the selected stack frame, like the @value{GDBN}
25395 @code{finish} command.
25398 Continue execution of your program, like the @value{GDBN} @code{continue}
25402 Go up the number of frames indicated by the numeric argument
25403 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25404 like the @value{GDBN} @code{up} command.
25407 Go down the number of frames indicated by the numeric argument, like the
25408 @value{GDBN} @code{down} command.
25411 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25412 tells @value{GDBN} to set a breakpoint on the source line point is on.
25414 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25415 separate frame which shows a backtrace when the GUD buffer is current.
25416 Move point to any frame in the stack and type @key{RET} to make it
25417 become the current frame and display the associated source in the
25418 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25419 selected frame become the current one. In graphical mode, the
25420 speedbar displays watch expressions.
25422 If you accidentally delete the source-display buffer, an easy way to get
25423 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25424 request a frame display; when you run under Emacs, this recreates
25425 the source buffer if necessary to show you the context of the current
25428 The source files displayed in Emacs are in ordinary Emacs buffers
25429 which are visiting the source files in the usual way. You can edit
25430 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25431 communicates with Emacs in terms of line numbers. If you add or
25432 delete lines from the text, the line numbers that @value{GDBN} knows cease
25433 to correspond properly with the code.
25435 A more detailed description of Emacs' interaction with @value{GDBN} is
25436 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25440 @chapter The @sc{gdb/mi} Interface
25442 @unnumberedsec Function and Purpose
25444 @cindex @sc{gdb/mi}, its purpose
25445 @sc{gdb/mi} is a line based machine oriented text interface to
25446 @value{GDBN} and is activated by specifying using the
25447 @option{--interpreter} command line option (@pxref{Mode Options}). It
25448 is specifically intended to support the development of systems which
25449 use the debugger as just one small component of a larger system.
25451 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25452 in the form of a reference manual.
25454 Note that @sc{gdb/mi} is still under construction, so some of the
25455 features described below are incomplete and subject to change
25456 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25458 @unnumberedsec Notation and Terminology
25460 @cindex notational conventions, for @sc{gdb/mi}
25461 This chapter uses the following notation:
25465 @code{|} separates two alternatives.
25468 @code{[ @var{something} ]} indicates that @var{something} is optional:
25469 it may or may not be given.
25472 @code{( @var{group} )*} means that @var{group} inside the parentheses
25473 may repeat zero or more times.
25476 @code{( @var{group} )+} means that @var{group} inside the parentheses
25477 may repeat one or more times.
25480 @code{"@var{string}"} means a literal @var{string}.
25484 @heading Dependencies
25488 * GDB/MI General Design::
25489 * GDB/MI Command Syntax::
25490 * GDB/MI Compatibility with CLI::
25491 * GDB/MI Development and Front Ends::
25492 * GDB/MI Output Records::
25493 * GDB/MI Simple Examples::
25494 * GDB/MI Command Description Format::
25495 * GDB/MI Breakpoint Commands::
25496 * GDB/MI Catchpoint Commands::
25497 * GDB/MI Program Context::
25498 * GDB/MI Thread Commands::
25499 * GDB/MI Ada Tasking Commands::
25500 * GDB/MI Program Execution::
25501 * GDB/MI Stack Manipulation::
25502 * GDB/MI Variable Objects::
25503 * GDB/MI Data Manipulation::
25504 * GDB/MI Tracepoint Commands::
25505 * GDB/MI Symbol Query::
25506 * GDB/MI File Commands::
25508 * GDB/MI Kod Commands::
25509 * GDB/MI Memory Overlay Commands::
25510 * GDB/MI Signal Handling Commands::
25512 * GDB/MI Target Manipulation::
25513 * GDB/MI File Transfer Commands::
25514 * GDB/MI Ada Exceptions Commands::
25515 * GDB/MI Support Commands::
25516 * GDB/MI Miscellaneous Commands::
25519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25520 @node GDB/MI General Design
25521 @section @sc{gdb/mi} General Design
25522 @cindex GDB/MI General Design
25524 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25525 parts---commands sent to @value{GDBN}, responses to those commands
25526 and notifications. Each command results in exactly one response,
25527 indicating either successful completion of the command, or an error.
25528 For the commands that do not resume the target, the response contains the
25529 requested information. For the commands that resume the target, the
25530 response only indicates whether the target was successfully resumed.
25531 Notifications is the mechanism for reporting changes in the state of the
25532 target, or in @value{GDBN} state, that cannot conveniently be associated with
25533 a command and reported as part of that command response.
25535 The important examples of notifications are:
25539 Exec notifications. These are used to report changes in
25540 target state---when a target is resumed, or stopped. It would not
25541 be feasible to include this information in response of resuming
25542 commands, because one resume commands can result in multiple events in
25543 different threads. Also, quite some time may pass before any event
25544 happens in the target, while a frontend needs to know whether the resuming
25545 command itself was successfully executed.
25548 Console output, and status notifications. Console output
25549 notifications are used to report output of CLI commands, as well as
25550 diagnostics for other commands. Status notifications are used to
25551 report the progress of a long-running operation. Naturally, including
25552 this information in command response would mean no output is produced
25553 until the command is finished, which is undesirable.
25556 General notifications. Commands may have various side effects on
25557 the @value{GDBN} or target state beyond their official purpose. For example,
25558 a command may change the selected thread. Although such changes can
25559 be included in command response, using notification allows for more
25560 orthogonal frontend design.
25564 There's no guarantee that whenever an MI command reports an error,
25565 @value{GDBN} or the target are in any specific state, and especially,
25566 the state is not reverted to the state before the MI command was
25567 processed. Therefore, whenever an MI command results in an error,
25568 we recommend that the frontend refreshes all the information shown in
25569 the user interface.
25573 * Context management::
25574 * Asynchronous and non-stop modes::
25578 @node Context management
25579 @subsection Context management
25581 @subsubsection Threads and Frames
25583 In most cases when @value{GDBN} accesses the target, this access is
25584 done in context of a specific thread and frame (@pxref{Frames}).
25585 Often, even when accessing global data, the target requires that a thread
25586 be specified. The CLI interface maintains the selected thread and frame,
25587 and supplies them to target on each command. This is convenient,
25588 because a command line user would not want to specify that information
25589 explicitly on each command, and because user interacts with
25590 @value{GDBN} via a single terminal, so no confusion is possible as
25591 to what thread and frame are the current ones.
25593 In the case of MI, the concept of selected thread and frame is less
25594 useful. First, a frontend can easily remember this information
25595 itself. Second, a graphical frontend can have more than one window,
25596 each one used for debugging a different thread, and the frontend might
25597 want to access additional threads for internal purposes. This
25598 increases the risk that by relying on implicitly selected thread, the
25599 frontend may be operating on a wrong one. Therefore, each MI command
25600 should explicitly specify which thread and frame to operate on. To
25601 make it possible, each MI command accepts the @samp{--thread} and
25602 @samp{--frame} options, the value to each is @value{GDBN} global
25603 identifier for thread and frame to operate on.
25605 Usually, each top-level window in a frontend allows the user to select
25606 a thread and a frame, and remembers the user selection for further
25607 operations. However, in some cases @value{GDBN} may suggest that the
25608 current thread be changed. For example, when stopping on a breakpoint
25609 it is reasonable to switch to the thread where breakpoint is hit. For
25610 another example, if the user issues the CLI @samp{thread} command via
25611 the frontend, it is desirable to change the frontend's selected thread to the
25612 one specified by user. @value{GDBN} communicates the suggestion to
25613 change current thread using the @samp{=thread-selected} notification.
25614 No such notification is available for the selected frame at the moment.
25616 Note that historically, MI shares the selected thread with CLI, so
25617 frontends used the @code{-thread-select} to execute commands in the
25618 right context. However, getting this to work right is cumbersome. The
25619 simplest way is for frontend to emit @code{-thread-select} command
25620 before every command. This doubles the number of commands that need
25621 to be sent. The alternative approach is to suppress @code{-thread-select}
25622 if the selected thread in @value{GDBN} is supposed to be identical to the
25623 thread the frontend wants to operate on. However, getting this
25624 optimization right can be tricky. In particular, if the frontend
25625 sends several commands to @value{GDBN}, and one of the commands changes the
25626 selected thread, then the behaviour of subsequent commands will
25627 change. So, a frontend should either wait for response from such
25628 problematic commands, or explicitly add @code{-thread-select} for
25629 all subsequent commands. No frontend is known to do this exactly
25630 right, so it is suggested to just always pass the @samp{--thread} and
25631 @samp{--frame} options.
25633 @subsubsection Language
25635 The execution of several commands depends on which language is selected.
25636 By default, the current language (@pxref{show language}) is used.
25637 But for commands known to be language-sensitive, it is recommended
25638 to use the @samp{--language} option. This option takes one argument,
25639 which is the name of the language to use while executing the command.
25643 -data-evaluate-expression --language c "sizeof (void*)"
25648 The valid language names are the same names accepted by the
25649 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25650 @samp{local} or @samp{unknown}.
25652 @node Asynchronous and non-stop modes
25653 @subsection Asynchronous command execution and non-stop mode
25655 On some targets, @value{GDBN} is capable of processing MI commands
25656 even while the target is running. This is called @dfn{asynchronous
25657 command execution} (@pxref{Background Execution}). The frontend may
25658 specify a preferrence for asynchronous execution using the
25659 @code{-gdb-set mi-async 1} command, which should be emitted before
25660 either running the executable or attaching to the target. After the
25661 frontend has started the executable or attached to the target, it can
25662 find if asynchronous execution is enabled using the
25663 @code{-list-target-features} command.
25666 @item -gdb-set mi-async on
25667 @item -gdb-set mi-async off
25668 Set whether MI is in asynchronous mode.
25670 When @code{off}, which is the default, MI execution commands (e.g.,
25671 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25672 for the program to stop before processing further commands.
25674 When @code{on}, MI execution commands are background execution
25675 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25676 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25677 MI commands even while the target is running.
25679 @item -gdb-show mi-async
25680 Show whether MI asynchronous mode is enabled.
25683 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25684 @code{target-async} instead of @code{mi-async}, and it had the effect
25685 of both putting MI in asynchronous mode and making CLI background
25686 commands possible. CLI background commands are now always possible
25687 ``out of the box'' if the target supports them. The old spelling is
25688 kept as a deprecated alias for backwards compatibility.
25690 Even if @value{GDBN} can accept a command while target is running,
25691 many commands that access the target do not work when the target is
25692 running. Therefore, asynchronous command execution is most useful
25693 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25694 it is possible to examine the state of one thread, while other threads
25697 When a given thread is running, MI commands that try to access the
25698 target in the context of that thread may not work, or may work only on
25699 some targets. In particular, commands that try to operate on thread's
25700 stack will not work, on any target. Commands that read memory, or
25701 modify breakpoints, may work or not work, depending on the target. Note
25702 that even commands that operate on global state, such as @code{print},
25703 @code{set}, and breakpoint commands, still access the target in the
25704 context of a specific thread, so frontend should try to find a
25705 stopped thread and perform the operation on that thread (using the
25706 @samp{--thread} option).
25708 Which commands will work in the context of a running thread is
25709 highly target dependent. However, the two commands
25710 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25711 to find the state of a thread, will always work.
25713 @node Thread groups
25714 @subsection Thread groups
25715 @value{GDBN} may be used to debug several processes at the same time.
25716 On some platfroms, @value{GDBN} may support debugging of several
25717 hardware systems, each one having several cores with several different
25718 processes running on each core. This section describes the MI
25719 mechanism to support such debugging scenarios.
25721 The key observation is that regardless of the structure of the
25722 target, MI can have a global list of threads, because most commands that
25723 accept the @samp{--thread} option do not need to know what process that
25724 thread belongs to. Therefore, it is not necessary to introduce
25725 neither additional @samp{--process} option, nor an notion of the
25726 current process in the MI interface. The only strictly new feature
25727 that is required is the ability to find how the threads are grouped
25730 To allow the user to discover such grouping, and to support arbitrary
25731 hierarchy of machines/cores/processes, MI introduces the concept of a
25732 @dfn{thread group}. Thread group is a collection of threads and other
25733 thread groups. A thread group always has a string identifier, a type,
25734 and may have additional attributes specific to the type. A new
25735 command, @code{-list-thread-groups}, returns the list of top-level
25736 thread groups, which correspond to processes that @value{GDBN} is
25737 debugging at the moment. By passing an identifier of a thread group
25738 to the @code{-list-thread-groups} command, it is possible to obtain
25739 the members of specific thread group.
25741 To allow the user to easily discover processes, and other objects, he
25742 wishes to debug, a concept of @dfn{available thread group} is
25743 introduced. Available thread group is an thread group that
25744 @value{GDBN} is not debugging, but that can be attached to, using the
25745 @code{-target-attach} command. The list of available top-level thread
25746 groups can be obtained using @samp{-list-thread-groups --available}.
25747 In general, the content of a thread group may be only retrieved only
25748 after attaching to that thread group.
25750 Thread groups are related to inferiors (@pxref{Inferiors and
25751 Programs}). Each inferior corresponds to a thread group of a special
25752 type @samp{process}, and some additional operations are permitted on
25753 such thread groups.
25755 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25756 @node GDB/MI Command Syntax
25757 @section @sc{gdb/mi} Command Syntax
25760 * GDB/MI Input Syntax::
25761 * GDB/MI Output Syntax::
25764 @node GDB/MI Input Syntax
25765 @subsection @sc{gdb/mi} Input Syntax
25767 @cindex input syntax for @sc{gdb/mi}
25768 @cindex @sc{gdb/mi}, input syntax
25770 @item @var{command} @expansion{}
25771 @code{@var{cli-command} | @var{mi-command}}
25773 @item @var{cli-command} @expansion{}
25774 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25775 @var{cli-command} is any existing @value{GDBN} CLI command.
25777 @item @var{mi-command} @expansion{}
25778 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25779 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25781 @item @var{token} @expansion{}
25782 "any sequence of digits"
25784 @item @var{option} @expansion{}
25785 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25787 @item @var{parameter} @expansion{}
25788 @code{@var{non-blank-sequence} | @var{c-string}}
25790 @item @var{operation} @expansion{}
25791 @emph{any of the operations described in this chapter}
25793 @item @var{non-blank-sequence} @expansion{}
25794 @emph{anything, provided it doesn't contain special characters such as
25795 "-", @var{nl}, """ and of course " "}
25797 @item @var{c-string} @expansion{}
25798 @code{""" @var{seven-bit-iso-c-string-content} """}
25800 @item @var{nl} @expansion{}
25809 The CLI commands are still handled by the @sc{mi} interpreter; their
25810 output is described below.
25813 The @code{@var{token}}, when present, is passed back when the command
25817 Some @sc{mi} commands accept optional arguments as part of the parameter
25818 list. Each option is identified by a leading @samp{-} (dash) and may be
25819 followed by an optional argument parameter. Options occur first in the
25820 parameter list and can be delimited from normal parameters using
25821 @samp{--} (this is useful when some parameters begin with a dash).
25828 We want easy access to the existing CLI syntax (for debugging).
25831 We want it to be easy to spot a @sc{mi} operation.
25834 @node GDB/MI Output Syntax
25835 @subsection @sc{gdb/mi} Output Syntax
25837 @cindex output syntax of @sc{gdb/mi}
25838 @cindex @sc{gdb/mi}, output syntax
25839 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25840 followed, optionally, by a single result record. This result record
25841 is for the most recent command. The sequence of output records is
25842 terminated by @samp{(gdb)}.
25844 If an input command was prefixed with a @code{@var{token}} then the
25845 corresponding output for that command will also be prefixed by that same
25849 @item @var{output} @expansion{}
25850 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25852 @item @var{result-record} @expansion{}
25853 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25855 @item @var{out-of-band-record} @expansion{}
25856 @code{@var{async-record} | @var{stream-record}}
25858 @item @var{async-record} @expansion{}
25859 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25861 @item @var{exec-async-output} @expansion{}
25862 @code{[ @var{token} ] "*" @var{async-output nl}}
25864 @item @var{status-async-output} @expansion{}
25865 @code{[ @var{token} ] "+" @var{async-output nl}}
25867 @item @var{notify-async-output} @expansion{}
25868 @code{[ @var{token} ] "=" @var{async-output nl}}
25870 @item @var{async-output} @expansion{}
25871 @code{@var{async-class} ( "," @var{result} )*}
25873 @item @var{result-class} @expansion{}
25874 @code{"done" | "running" | "connected" | "error" | "exit"}
25876 @item @var{async-class} @expansion{}
25877 @code{"stopped" | @var{others}} (where @var{others} will be added
25878 depending on the needs---this is still in development).
25880 @item @var{result} @expansion{}
25881 @code{ @var{variable} "=" @var{value}}
25883 @item @var{variable} @expansion{}
25884 @code{ @var{string} }
25886 @item @var{value} @expansion{}
25887 @code{ @var{const} | @var{tuple} | @var{list} }
25889 @item @var{const} @expansion{}
25890 @code{@var{c-string}}
25892 @item @var{tuple} @expansion{}
25893 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25895 @item @var{list} @expansion{}
25896 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25897 @var{result} ( "," @var{result} )* "]" }
25899 @item @var{stream-record} @expansion{}
25900 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25902 @item @var{console-stream-output} @expansion{}
25903 @code{"~" @var{c-string nl}}
25905 @item @var{target-stream-output} @expansion{}
25906 @code{"@@" @var{c-string nl}}
25908 @item @var{log-stream-output} @expansion{}
25909 @code{"&" @var{c-string nl}}
25911 @item @var{nl} @expansion{}
25914 @item @var{token} @expansion{}
25915 @emph{any sequence of digits}.
25923 All output sequences end in a single line containing a period.
25926 The @code{@var{token}} is from the corresponding request. Note that
25927 for all async output, while the token is allowed by the grammar and
25928 may be output by future versions of @value{GDBN} for select async
25929 output messages, it is generally omitted. Frontends should treat
25930 all async output as reporting general changes in the state of the
25931 target and there should be no need to associate async output to any
25935 @cindex status output in @sc{gdb/mi}
25936 @var{status-async-output} contains on-going status information about the
25937 progress of a slow operation. It can be discarded. All status output is
25938 prefixed by @samp{+}.
25941 @cindex async output in @sc{gdb/mi}
25942 @var{exec-async-output} contains asynchronous state change on the target
25943 (stopped, started, disappeared). All async output is prefixed by
25947 @cindex notify output in @sc{gdb/mi}
25948 @var{notify-async-output} contains supplementary information that the
25949 client should handle (e.g., a new breakpoint information). All notify
25950 output is prefixed by @samp{=}.
25953 @cindex console output in @sc{gdb/mi}
25954 @var{console-stream-output} is output that should be displayed as is in the
25955 console. It is the textual response to a CLI command. All the console
25956 output is prefixed by @samp{~}.
25959 @cindex target output in @sc{gdb/mi}
25960 @var{target-stream-output} is the output produced by the target program.
25961 All the target output is prefixed by @samp{@@}.
25964 @cindex log output in @sc{gdb/mi}
25965 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25966 instance messages that should be displayed as part of an error log. All
25967 the log output is prefixed by @samp{&}.
25970 @cindex list output in @sc{gdb/mi}
25971 New @sc{gdb/mi} commands should only output @var{lists} containing
25977 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25978 details about the various output records.
25980 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25981 @node GDB/MI Compatibility with CLI
25982 @section @sc{gdb/mi} Compatibility with CLI
25984 @cindex compatibility, @sc{gdb/mi} and CLI
25985 @cindex @sc{gdb/mi}, compatibility with CLI
25987 For the developers convenience CLI commands can be entered directly,
25988 but there may be some unexpected behaviour. For example, commands
25989 that query the user will behave as if the user replied yes, breakpoint
25990 command lists are not executed and some CLI commands, such as
25991 @code{if}, @code{when} and @code{define}, prompt for further input with
25992 @samp{>}, which is not valid MI output.
25994 This feature may be removed at some stage in the future and it is
25995 recommended that front ends use the @code{-interpreter-exec} command
25996 (@pxref{-interpreter-exec}).
25998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25999 @node GDB/MI Development and Front Ends
26000 @section @sc{gdb/mi} Development and Front Ends
26001 @cindex @sc{gdb/mi} development
26003 The application which takes the MI output and presents the state of the
26004 program being debugged to the user is called a @dfn{front end}.
26006 Although @sc{gdb/mi} is still incomplete, it is currently being used
26007 by a variety of front ends to @value{GDBN}. This makes it difficult
26008 to introduce new functionality without breaking existing usage. This
26009 section tries to minimize the problems by describing how the protocol
26012 Some changes in MI need not break a carefully designed front end, and
26013 for these the MI version will remain unchanged. The following is a
26014 list of changes that may occur within one level, so front ends should
26015 parse MI output in a way that can handle them:
26019 New MI commands may be added.
26022 New fields may be added to the output of any MI command.
26025 The range of values for fields with specified values, e.g.,
26026 @code{in_scope} (@pxref{-var-update}) may be extended.
26028 @c The format of field's content e.g type prefix, may change so parse it
26029 @c at your own risk. Yes, in general?
26031 @c The order of fields may change? Shouldn't really matter but it might
26032 @c resolve inconsistencies.
26035 If the changes are likely to break front ends, the MI version level
26036 will be increased by one. This will allow the front end to parse the
26037 output according to the MI version. Apart from mi0, new versions of
26038 @value{GDBN} will not support old versions of MI and it will be the
26039 responsibility of the front end to work with the new one.
26041 @c Starting with mi3, add a new command -mi-version that prints the MI
26044 The best way to avoid unexpected changes in MI that might break your front
26045 end is to make your project known to @value{GDBN} developers and
26046 follow development on @email{gdb@@sourceware.org} and
26047 @email{gdb-patches@@sourceware.org}.
26048 @cindex mailing lists
26050 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26051 @node GDB/MI Output Records
26052 @section @sc{gdb/mi} Output Records
26055 * GDB/MI Result Records::
26056 * GDB/MI Stream Records::
26057 * GDB/MI Async Records::
26058 * GDB/MI Breakpoint Information::
26059 * GDB/MI Frame Information::
26060 * GDB/MI Thread Information::
26061 * GDB/MI Ada Exception Information::
26064 @node GDB/MI Result Records
26065 @subsection @sc{gdb/mi} Result Records
26067 @cindex result records in @sc{gdb/mi}
26068 @cindex @sc{gdb/mi}, result records
26069 In addition to a number of out-of-band notifications, the response to a
26070 @sc{gdb/mi} command includes one of the following result indications:
26074 @item "^done" [ "," @var{results} ]
26075 The synchronous operation was successful, @code{@var{results}} are the return
26080 This result record is equivalent to @samp{^done}. Historically, it
26081 was output instead of @samp{^done} if the command has resumed the
26082 target. This behaviour is maintained for backward compatibility, but
26083 all frontends should treat @samp{^done} and @samp{^running}
26084 identically and rely on the @samp{*running} output record to determine
26085 which threads are resumed.
26089 @value{GDBN} has connected to a remote target.
26091 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26093 The operation failed. The @code{msg=@var{c-string}} variable contains
26094 the corresponding error message.
26096 If present, the @code{code=@var{c-string}} variable provides an error
26097 code on which consumers can rely on to detect the corresponding
26098 error condition. At present, only one error code is defined:
26101 @item "undefined-command"
26102 Indicates that the command causing the error does not exist.
26107 @value{GDBN} has terminated.
26111 @node GDB/MI Stream Records
26112 @subsection @sc{gdb/mi} Stream Records
26114 @cindex @sc{gdb/mi}, stream records
26115 @cindex stream records in @sc{gdb/mi}
26116 @value{GDBN} internally maintains a number of output streams: the console, the
26117 target, and the log. The output intended for each of these streams is
26118 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26120 Each stream record begins with a unique @dfn{prefix character} which
26121 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26122 Syntax}). In addition to the prefix, each stream record contains a
26123 @code{@var{string-output}}. This is either raw text (with an implicit new
26124 line) or a quoted C string (which does not contain an implicit newline).
26127 @item "~" @var{string-output}
26128 The console output stream contains text that should be displayed in the
26129 CLI console window. It contains the textual responses to CLI commands.
26131 @item "@@" @var{string-output}
26132 The target output stream contains any textual output from the running
26133 target. This is only present when GDB's event loop is truly
26134 asynchronous, which is currently only the case for remote targets.
26136 @item "&" @var{string-output}
26137 The log stream contains debugging messages being produced by @value{GDBN}'s
26141 @node GDB/MI Async Records
26142 @subsection @sc{gdb/mi} Async Records
26144 @cindex async records in @sc{gdb/mi}
26145 @cindex @sc{gdb/mi}, async records
26146 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26147 additional changes that have occurred. Those changes can either be a
26148 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26149 target activity (e.g., target stopped).
26151 The following is the list of possible async records:
26155 @item *running,thread-id="@var{thread}"
26156 The target is now running. The @var{thread} field can be the global
26157 thread ID of the the thread that is now running, and it can be
26158 @samp{all} if all threads are running. The frontend should assume
26159 that no interaction with a running thread is possible after this
26160 notification is produced. The frontend should not assume that this
26161 notification is output only once for any command. @value{GDBN} may
26162 emit this notification several times, either for different threads,
26163 because it cannot resume all threads together, or even for a single
26164 thread, if the thread must be stepped though some code before letting
26167 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26168 The target has stopped. The @var{reason} field can have one of the
26172 @item breakpoint-hit
26173 A breakpoint was reached.
26174 @item watchpoint-trigger
26175 A watchpoint was triggered.
26176 @item read-watchpoint-trigger
26177 A read watchpoint was triggered.
26178 @item access-watchpoint-trigger
26179 An access watchpoint was triggered.
26180 @item function-finished
26181 An -exec-finish or similar CLI command was accomplished.
26182 @item location-reached
26183 An -exec-until or similar CLI command was accomplished.
26184 @item watchpoint-scope
26185 A watchpoint has gone out of scope.
26186 @item end-stepping-range
26187 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26188 similar CLI command was accomplished.
26189 @item exited-signalled
26190 The inferior exited because of a signal.
26192 The inferior exited.
26193 @item exited-normally
26194 The inferior exited normally.
26195 @item signal-received
26196 A signal was received by the inferior.
26198 The inferior has stopped due to a library being loaded or unloaded.
26199 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26200 set or when a @code{catch load} or @code{catch unload} catchpoint is
26201 in use (@pxref{Set Catchpoints}).
26203 The inferior has forked. This is reported when @code{catch fork}
26204 (@pxref{Set Catchpoints}) has been used.
26206 The inferior has vforked. This is reported in when @code{catch vfork}
26207 (@pxref{Set Catchpoints}) has been used.
26208 @item syscall-entry
26209 The inferior entered a system call. This is reported when @code{catch
26210 syscall} (@pxref{Set Catchpoints}) has been used.
26211 @item syscall-return
26212 The inferior returned from a system call. This is reported when
26213 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26215 The inferior called @code{exec}. This is reported when @code{catch exec}
26216 (@pxref{Set Catchpoints}) has been used.
26219 The @var{id} field identifies the global thread ID of the thread
26220 that directly caused the stop -- for example by hitting a breakpoint.
26221 Depending on whether all-stop
26222 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26223 stop all threads, or only the thread that directly triggered the stop.
26224 If all threads are stopped, the @var{stopped} field will have the
26225 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26226 field will be a list of thread identifiers. Presently, this list will
26227 always include a single thread, but frontend should be prepared to see
26228 several threads in the list. The @var{core} field reports the
26229 processor core on which the stop event has happened. This field may be absent
26230 if such information is not available.
26232 @item =thread-group-added,id="@var{id}"
26233 @itemx =thread-group-removed,id="@var{id}"
26234 A thread group was either added or removed. The @var{id} field
26235 contains the @value{GDBN} identifier of the thread group. When a thread
26236 group is added, it generally might not be associated with a running
26237 process. When a thread group is removed, its id becomes invalid and
26238 cannot be used in any way.
26240 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26241 A thread group became associated with a running program,
26242 either because the program was just started or the thread group
26243 was attached to a program. The @var{id} field contains the
26244 @value{GDBN} identifier of the thread group. The @var{pid} field
26245 contains process identifier, specific to the operating system.
26247 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26248 A thread group is no longer associated with a running program,
26249 either because the program has exited, or because it was detached
26250 from. The @var{id} field contains the @value{GDBN} identifier of the
26251 thread group. The @var{code} field is the exit code of the inferior; it exists
26252 only when the inferior exited with some code.
26254 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26255 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26256 A thread either was created, or has exited. The @var{id} field
26257 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26258 field identifies the thread group this thread belongs to.
26260 @item =thread-selected,id="@var{id}"
26261 Informs that the selected thread was changed as result of the last
26262 command. This notification is not emitted as result of @code{-thread-select}
26263 command but is emitted whenever an MI command that is not documented
26264 to change the selected thread actually changes it. In particular,
26265 invoking, directly or indirectly (via user-defined command), the CLI
26266 @code{thread} command, will generate this notification.
26268 We suggest that in response to this notification, front ends
26269 highlight the selected thread and cause subsequent commands to apply to
26272 @item =library-loaded,...
26273 Reports that a new library file was loaded by the program. This
26274 notification has 4 fields---@var{id}, @var{target-name},
26275 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26276 opaque identifier of the library. For remote debugging case,
26277 @var{target-name} and @var{host-name} fields give the name of the
26278 library file on the target, and on the host respectively. For native
26279 debugging, both those fields have the same value. The
26280 @var{symbols-loaded} field is emitted only for backward compatibility
26281 and should not be relied on to convey any useful information. The
26282 @var{thread-group} field, if present, specifies the id of the thread
26283 group in whose context the library was loaded. If the field is
26284 absent, it means the library was loaded in the context of all present
26287 @item =library-unloaded,...
26288 Reports that a library was unloaded by the program. This notification
26289 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26290 the same meaning as for the @code{=library-loaded} notification.
26291 The @var{thread-group} field, if present, specifies the id of the
26292 thread group in whose context the library was unloaded. If the field is
26293 absent, it means the library was unloaded in the context of all present
26296 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26297 @itemx =traceframe-changed,end
26298 Reports that the trace frame was changed and its new number is
26299 @var{tfnum}. The number of the tracepoint associated with this trace
26300 frame is @var{tpnum}.
26302 @item =tsv-created,name=@var{name},initial=@var{initial}
26303 Reports that the new trace state variable @var{name} is created with
26304 initial value @var{initial}.
26306 @item =tsv-deleted,name=@var{name}
26307 @itemx =tsv-deleted
26308 Reports that the trace state variable @var{name} is deleted or all
26309 trace state variables are deleted.
26311 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26312 Reports that the trace state variable @var{name} is modified with
26313 the initial value @var{initial}. The current value @var{current} of
26314 trace state variable is optional and is reported if the current
26315 value of trace state variable is known.
26317 @item =breakpoint-created,bkpt=@{...@}
26318 @itemx =breakpoint-modified,bkpt=@{...@}
26319 @itemx =breakpoint-deleted,id=@var{number}
26320 Reports that a breakpoint was created, modified, or deleted,
26321 respectively. Only user-visible breakpoints are reported to the MI
26324 The @var{bkpt} argument is of the same form as returned by the various
26325 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26326 @var{number} is the ordinal number of the breakpoint.
26328 Note that if a breakpoint is emitted in the result record of a
26329 command, then it will not also be emitted in an async record.
26331 @item =record-started,thread-group="@var{id}"
26332 @itemx =record-stopped,thread-group="@var{id}"
26333 Execution log recording was either started or stopped on an
26334 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26335 group corresponding to the affected inferior.
26337 @item =cmd-param-changed,param=@var{param},value=@var{value}
26338 Reports that a parameter of the command @code{set @var{param}} is
26339 changed to @var{value}. In the multi-word @code{set} command,
26340 the @var{param} is the whole parameter list to @code{set} command.
26341 For example, In command @code{set check type on}, @var{param}
26342 is @code{check type} and @var{value} is @code{on}.
26344 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26345 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26346 written in an inferior. The @var{id} is the identifier of the
26347 thread group corresponding to the affected inferior. The optional
26348 @code{type="code"} part is reported if the memory written to holds
26352 @node GDB/MI Breakpoint Information
26353 @subsection @sc{gdb/mi} Breakpoint Information
26355 When @value{GDBN} reports information about a breakpoint, a
26356 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26361 The breakpoint number. For a breakpoint that represents one location
26362 of a multi-location breakpoint, this will be a dotted pair, like
26366 The type of the breakpoint. For ordinary breakpoints this will be
26367 @samp{breakpoint}, but many values are possible.
26370 If the type of the breakpoint is @samp{catchpoint}, then this
26371 indicates the exact type of catchpoint.
26374 This is the breakpoint disposition---either @samp{del}, meaning that
26375 the breakpoint will be deleted at the next stop, or @samp{keep},
26376 meaning that the breakpoint will not be deleted.
26379 This indicates whether the breakpoint is enabled, in which case the
26380 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26381 Note that this is not the same as the field @code{enable}.
26384 The address of the breakpoint. This may be a hexidecimal number,
26385 giving the address; or the string @samp{<PENDING>}, for a pending
26386 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26387 multiple locations. This field will not be present if no address can
26388 be determined. For example, a watchpoint does not have an address.
26391 If known, the function in which the breakpoint appears.
26392 If not known, this field is not present.
26395 The name of the source file which contains this function, if known.
26396 If not known, this field is not present.
26399 The full file name of the source file which contains this function, if
26400 known. If not known, this field is not present.
26403 The line number at which this breakpoint appears, if known.
26404 If not known, this field is not present.
26407 If the source file is not known, this field may be provided. If
26408 provided, this holds the address of the breakpoint, possibly followed
26412 If this breakpoint is pending, this field is present and holds the
26413 text used to set the breakpoint, as entered by the user.
26416 Where this breakpoint's condition is evaluated, either @samp{host} or
26420 If this is a thread-specific breakpoint, then this identifies the
26421 thread in which the breakpoint can trigger.
26424 If this breakpoint is restricted to a particular Ada task, then this
26425 field will hold the task identifier.
26428 If the breakpoint is conditional, this is the condition expression.
26431 The ignore count of the breakpoint.
26434 The enable count of the breakpoint.
26436 @item traceframe-usage
26439 @item static-tracepoint-marker-string-id
26440 For a static tracepoint, the name of the static tracepoint marker.
26443 For a masked watchpoint, this is the mask.
26446 A tracepoint's pass count.
26448 @item original-location
26449 The location of the breakpoint as originally specified by the user.
26450 This field is optional.
26453 The number of times the breakpoint has been hit.
26456 This field is only given for tracepoints. This is either @samp{y},
26457 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26461 Some extra data, the exact contents of which are type-dependent.
26465 For example, here is what the output of @code{-break-insert}
26466 (@pxref{GDB/MI Breakpoint Commands}) might be:
26469 -> -break-insert main
26470 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26471 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26472 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26477 @node GDB/MI Frame Information
26478 @subsection @sc{gdb/mi} Frame Information
26480 Response from many MI commands includes an information about stack
26481 frame. This information is a tuple that may have the following
26486 The level of the stack frame. The innermost frame has the level of
26487 zero. This field is always present.
26490 The name of the function corresponding to the frame. This field may
26491 be absent if @value{GDBN} is unable to determine the function name.
26494 The code address for the frame. This field is always present.
26497 The name of the source files that correspond to the frame's code
26498 address. This field may be absent.
26501 The source line corresponding to the frames' code address. This field
26505 The name of the binary file (either executable or shared library) the
26506 corresponds to the frame's code address. This field may be absent.
26510 @node GDB/MI Thread Information
26511 @subsection @sc{gdb/mi} Thread Information
26513 Whenever @value{GDBN} has to report an information about a thread, it
26514 uses a tuple with the following fields:
26518 The global numeric id assigned to the thread by @value{GDBN}. This field is
26522 Target-specific string identifying the thread. This field is always present.
26525 Additional information about the thread provided by the target.
26526 It is supposed to be human-readable and not interpreted by the
26527 frontend. This field is optional.
26530 Either @samp{stopped} or @samp{running}, depending on whether the
26531 thread is presently running. This field is always present.
26534 The value of this field is an integer number of the processor core the
26535 thread was last seen on. This field is optional.
26538 @node GDB/MI Ada Exception Information
26539 @subsection @sc{gdb/mi} Ada Exception Information
26541 Whenever a @code{*stopped} record is emitted because the program
26542 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26543 @value{GDBN} provides the name of the exception that was raised via
26544 the @code{exception-name} field.
26546 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26547 @node GDB/MI Simple Examples
26548 @section Simple Examples of @sc{gdb/mi} Interaction
26549 @cindex @sc{gdb/mi}, simple examples
26551 This subsection presents several simple examples of interaction using
26552 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26553 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26554 the output received from @sc{gdb/mi}.
26556 Note the line breaks shown in the examples are here only for
26557 readability, they don't appear in the real output.
26559 @subheading Setting a Breakpoint
26561 Setting a breakpoint generates synchronous output which contains detailed
26562 information of the breakpoint.
26565 -> -break-insert main
26566 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26567 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26568 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26573 @subheading Program Execution
26575 Program execution generates asynchronous records and MI gives the
26576 reason that execution stopped.
26582 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26583 frame=@{addr="0x08048564",func="main",
26584 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26585 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26590 <- *stopped,reason="exited-normally"
26594 @subheading Quitting @value{GDBN}
26596 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26604 Please note that @samp{^exit} is printed immediately, but it might
26605 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26606 performs necessary cleanups, including killing programs being debugged
26607 or disconnecting from debug hardware, so the frontend should wait till
26608 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26609 fails to exit in reasonable time.
26611 @subheading A Bad Command
26613 Here's what happens if you pass a non-existent command:
26617 <- ^error,msg="Undefined MI command: rubbish"
26622 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26623 @node GDB/MI Command Description Format
26624 @section @sc{gdb/mi} Command Description Format
26626 The remaining sections describe blocks of commands. Each block of
26627 commands is laid out in a fashion similar to this section.
26629 @subheading Motivation
26631 The motivation for this collection of commands.
26633 @subheading Introduction
26635 A brief introduction to this collection of commands as a whole.
26637 @subheading Commands
26639 For each command in the block, the following is described:
26641 @subsubheading Synopsis
26644 -command @var{args}@dots{}
26647 @subsubheading Result
26649 @subsubheading @value{GDBN} Command
26651 The corresponding @value{GDBN} CLI command(s), if any.
26653 @subsubheading Example
26655 Example(s) formatted for readability. Some of the described commands have
26656 not been implemented yet and these are labeled N.A.@: (not available).
26659 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26660 @node GDB/MI Breakpoint Commands
26661 @section @sc{gdb/mi} Breakpoint Commands
26663 @cindex breakpoint commands for @sc{gdb/mi}
26664 @cindex @sc{gdb/mi}, breakpoint commands
26665 This section documents @sc{gdb/mi} commands for manipulating
26668 @subheading The @code{-break-after} Command
26669 @findex -break-after
26671 @subsubheading Synopsis
26674 -break-after @var{number} @var{count}
26677 The breakpoint number @var{number} is not in effect until it has been
26678 hit @var{count} times. To see how this is reflected in the output of
26679 the @samp{-break-list} command, see the description of the
26680 @samp{-break-list} command below.
26682 @subsubheading @value{GDBN} Command
26684 The corresponding @value{GDBN} command is @samp{ignore}.
26686 @subsubheading Example
26691 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26692 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26693 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26701 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26702 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26703 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26704 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26705 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26706 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26707 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26708 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26709 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26710 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26715 @subheading The @code{-break-catch} Command
26716 @findex -break-catch
26719 @subheading The @code{-break-commands} Command
26720 @findex -break-commands
26722 @subsubheading Synopsis
26725 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26728 Specifies the CLI commands that should be executed when breakpoint
26729 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26730 are the commands. If no command is specified, any previously-set
26731 commands are cleared. @xref{Break Commands}. Typical use of this
26732 functionality is tracing a program, that is, printing of values of
26733 some variables whenever breakpoint is hit and then continuing.
26735 @subsubheading @value{GDBN} Command
26737 The corresponding @value{GDBN} command is @samp{commands}.
26739 @subsubheading Example
26744 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26745 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26746 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26749 -break-commands 1 "print v" "continue"
26754 @subheading The @code{-break-condition} Command
26755 @findex -break-condition
26757 @subsubheading Synopsis
26760 -break-condition @var{number} @var{expr}
26763 Breakpoint @var{number} will stop the program only if the condition in
26764 @var{expr} is true. The condition becomes part of the
26765 @samp{-break-list} output (see the description of the @samp{-break-list}
26768 @subsubheading @value{GDBN} Command
26770 The corresponding @value{GDBN} command is @samp{condition}.
26772 @subsubheading Example
26776 -break-condition 1 1
26780 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26781 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26782 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26783 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26784 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26785 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26786 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26787 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26788 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26789 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26793 @subheading The @code{-break-delete} Command
26794 @findex -break-delete
26796 @subsubheading Synopsis
26799 -break-delete ( @var{breakpoint} )+
26802 Delete the breakpoint(s) whose number(s) are specified in the argument
26803 list. This is obviously reflected in the breakpoint list.
26805 @subsubheading @value{GDBN} Command
26807 The corresponding @value{GDBN} command is @samp{delete}.
26809 @subsubheading Example
26817 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26818 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26819 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26820 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26821 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26822 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26823 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26828 @subheading The @code{-break-disable} Command
26829 @findex -break-disable
26831 @subsubheading Synopsis
26834 -break-disable ( @var{breakpoint} )+
26837 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26838 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26840 @subsubheading @value{GDBN} Command
26842 The corresponding @value{GDBN} command is @samp{disable}.
26844 @subsubheading Example
26852 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26853 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26854 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26855 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26856 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26857 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26858 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26859 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26860 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26861 line="5",thread-groups=["i1"],times="0"@}]@}
26865 @subheading The @code{-break-enable} Command
26866 @findex -break-enable
26868 @subsubheading Synopsis
26871 -break-enable ( @var{breakpoint} )+
26874 Enable (previously disabled) @var{breakpoint}(s).
26876 @subsubheading @value{GDBN} Command
26878 The corresponding @value{GDBN} command is @samp{enable}.
26880 @subsubheading Example
26888 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26889 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26890 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26891 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26892 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26893 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26894 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26895 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26896 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26897 line="5",thread-groups=["i1"],times="0"@}]@}
26901 @subheading The @code{-break-info} Command
26902 @findex -break-info
26904 @subsubheading Synopsis
26907 -break-info @var{breakpoint}
26911 Get information about a single breakpoint.
26913 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26914 Information}, for details on the format of each breakpoint in the
26917 @subsubheading @value{GDBN} Command
26919 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26921 @subsubheading Example
26924 @subheading The @code{-break-insert} Command
26925 @findex -break-insert
26926 @anchor{-break-insert}
26928 @subsubheading Synopsis
26931 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26932 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26933 [ -p @var{thread-id} ] [ @var{location} ]
26937 If specified, @var{location}, can be one of:
26940 @item linespec location
26941 A linespec location. @xref{Linespec Locations}.
26943 @item explicit location
26944 An explicit location. @sc{gdb/mi} explicit locations are
26945 analogous to the CLI's explicit locations using the option names
26946 listed below. @xref{Explicit Locations}.
26949 @item --source @var{filename}
26950 The source file name of the location. This option requires the use
26951 of either @samp{--function} or @samp{--line}.
26953 @item --function @var{function}
26954 The name of a function or method.
26956 @item --label @var{label}
26957 The name of a label.
26959 @item --line @var{lineoffset}
26960 An absolute or relative line offset from the start of the location.
26963 @item address location
26964 An address location, *@var{address}. @xref{Address Locations}.
26968 The possible optional parameters of this command are:
26972 Insert a temporary breakpoint.
26974 Insert a hardware breakpoint.
26976 If @var{location} cannot be parsed (for example if it
26977 refers to unknown files or functions), create a pending
26978 breakpoint. Without this flag, @value{GDBN} will report
26979 an error, and won't create a breakpoint, if @var{location}
26982 Create a disabled breakpoint.
26984 Create a tracepoint. @xref{Tracepoints}. When this parameter
26985 is used together with @samp{-h}, a fast tracepoint is created.
26986 @item -c @var{condition}
26987 Make the breakpoint conditional on @var{condition}.
26988 @item -i @var{ignore-count}
26989 Initialize the @var{ignore-count}.
26990 @item -p @var{thread-id}
26991 Restrict the breakpoint to the thread with the specified global
26995 @subsubheading Result
26997 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26998 resulting breakpoint.
27000 Note: this format is open to change.
27001 @c An out-of-band breakpoint instead of part of the result?
27003 @subsubheading @value{GDBN} Command
27005 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27006 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27008 @subsubheading Example
27013 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27014 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27017 -break-insert -t foo
27018 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27019 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27023 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27024 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27025 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27026 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27027 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27028 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27029 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27030 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27031 addr="0x0001072c", func="main",file="recursive2.c",
27032 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27034 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27035 addr="0x00010774",func="foo",file="recursive2.c",
27036 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27039 @c -break-insert -r foo.*
27040 @c ~int foo(int, int);
27041 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27042 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27047 @subheading The @code{-dprintf-insert} Command
27048 @findex -dprintf-insert
27050 @subsubheading Synopsis
27053 -dprintf-insert [ -t ] [ -f ] [ -d ]
27054 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27055 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27060 If supplied, @var{location} may be specified the same way as for
27061 the @code{-break-insert} command. @xref{-break-insert}.
27063 The possible optional parameters of this command are:
27067 Insert a temporary breakpoint.
27069 If @var{location} cannot be parsed (for example, if it
27070 refers to unknown files or functions), create a pending
27071 breakpoint. Without this flag, @value{GDBN} will report
27072 an error, and won't create a breakpoint, if @var{location}
27075 Create a disabled breakpoint.
27076 @item -c @var{condition}
27077 Make the breakpoint conditional on @var{condition}.
27078 @item -i @var{ignore-count}
27079 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27080 to @var{ignore-count}.
27081 @item -p @var{thread-id}
27082 Restrict the breakpoint to the thread with the specified global
27086 @subsubheading Result
27088 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27089 resulting breakpoint.
27091 @c An out-of-band breakpoint instead of part of the result?
27093 @subsubheading @value{GDBN} Command
27095 The corresponding @value{GDBN} command is @samp{dprintf}.
27097 @subsubheading Example
27101 4-dprintf-insert foo "At foo entry\n"
27102 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27103 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27104 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27105 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27106 original-location="foo"@}
27108 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27109 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27110 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27111 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27112 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27113 original-location="mi-dprintf.c:26"@}
27117 @subheading The @code{-break-list} Command
27118 @findex -break-list
27120 @subsubheading Synopsis
27126 Displays the list of inserted breakpoints, showing the following fields:
27130 number of the breakpoint
27132 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27134 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27137 is the breakpoint enabled or no: @samp{y} or @samp{n}
27139 memory location at which the breakpoint is set
27141 logical location of the breakpoint, expressed by function name, file
27143 @item Thread-groups
27144 list of thread groups to which this breakpoint applies
27146 number of times the breakpoint has been hit
27149 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27150 @code{body} field is an empty list.
27152 @subsubheading @value{GDBN} Command
27154 The corresponding @value{GDBN} command is @samp{info break}.
27156 @subsubheading Example
27161 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27169 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27171 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27172 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27173 line="13",thread-groups=["i1"],times="0"@}]@}
27177 Here's an example of the result when there are no breakpoints:
27182 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27183 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27184 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27185 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27186 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27187 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27188 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27193 @subheading The @code{-break-passcount} Command
27194 @findex -break-passcount
27196 @subsubheading Synopsis
27199 -break-passcount @var{tracepoint-number} @var{passcount}
27202 Set the passcount for tracepoint @var{tracepoint-number} to
27203 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27204 is not a tracepoint, error is emitted. This corresponds to CLI
27205 command @samp{passcount}.
27207 @subheading The @code{-break-watch} Command
27208 @findex -break-watch
27210 @subsubheading Synopsis
27213 -break-watch [ -a | -r ]
27216 Create a watchpoint. With the @samp{-a} option it will create an
27217 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27218 read from or on a write to the memory location. With the @samp{-r}
27219 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27220 trigger only when the memory location is accessed for reading. Without
27221 either of the options, the watchpoint created is a regular watchpoint,
27222 i.e., it will trigger when the memory location is accessed for writing.
27223 @xref{Set Watchpoints, , Setting Watchpoints}.
27225 Note that @samp{-break-list} will report a single list of watchpoints and
27226 breakpoints inserted.
27228 @subsubheading @value{GDBN} Command
27230 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27233 @subsubheading Example
27235 Setting a watchpoint on a variable in the @code{main} function:
27240 ^done,wpt=@{number="2",exp="x"@}
27245 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27246 value=@{old="-268439212",new="55"@},
27247 frame=@{func="main",args=[],file="recursive2.c",
27248 fullname="/home/foo/bar/recursive2.c",line="5"@}
27252 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27253 the program execution twice: first for the variable changing value, then
27254 for the watchpoint going out of scope.
27259 ^done,wpt=@{number="5",exp="C"@}
27264 *stopped,reason="watchpoint-trigger",
27265 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27266 frame=@{func="callee4",args=[],
27267 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27268 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27273 *stopped,reason="watchpoint-scope",wpnum="5",
27274 frame=@{func="callee3",args=[@{name="strarg",
27275 value="0x11940 \"A string argument.\""@}],
27276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27277 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27281 Listing breakpoints and watchpoints, at different points in the program
27282 execution. Note that once the watchpoint goes out of scope, it is
27288 ^done,wpt=@{number="2",exp="C"@}
27291 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27292 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27293 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27294 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27295 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27296 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27297 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27298 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27299 addr="0x00010734",func="callee4",
27300 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27301 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27303 bkpt=@{number="2",type="watchpoint",disp="keep",
27304 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27309 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27310 value=@{old="-276895068",new="3"@},
27311 frame=@{func="callee4",args=[],
27312 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27313 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27316 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27317 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27318 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27319 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27320 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27321 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27322 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27323 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27324 addr="0x00010734",func="callee4",
27325 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27326 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27328 bkpt=@{number="2",type="watchpoint",disp="keep",
27329 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27333 ^done,reason="watchpoint-scope",wpnum="2",
27334 frame=@{func="callee3",args=[@{name="strarg",
27335 value="0x11940 \"A string argument.\""@}],
27336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27337 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27340 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27341 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27342 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27343 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27344 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27345 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27346 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27347 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27348 addr="0x00010734",func="callee4",
27349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27350 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27351 thread-groups=["i1"],times="1"@}]@}
27356 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27357 @node GDB/MI Catchpoint Commands
27358 @section @sc{gdb/mi} Catchpoint Commands
27360 This section documents @sc{gdb/mi} commands for manipulating
27364 * Shared Library GDB/MI Catchpoint Commands::
27365 * Ada Exception GDB/MI Catchpoint Commands::
27368 @node Shared Library GDB/MI Catchpoint Commands
27369 @subsection Shared Library @sc{gdb/mi} Catchpoints
27371 @subheading The @code{-catch-load} Command
27372 @findex -catch-load
27374 @subsubheading Synopsis
27377 -catch-load [ -t ] [ -d ] @var{regexp}
27380 Add a catchpoint for library load events. If the @samp{-t} option is used,
27381 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27382 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27383 in a disabled state. The @samp{regexp} argument is a regular
27384 expression used to match the name of the loaded library.
27387 @subsubheading @value{GDBN} Command
27389 The corresponding @value{GDBN} command is @samp{catch load}.
27391 @subsubheading Example
27394 -catch-load -t foo.so
27395 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27396 what="load of library matching foo.so",catch-type="load",times="0"@}
27401 @subheading The @code{-catch-unload} Command
27402 @findex -catch-unload
27404 @subsubheading Synopsis
27407 -catch-unload [ -t ] [ -d ] @var{regexp}
27410 Add a catchpoint for library unload events. If the @samp{-t} option is
27411 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27412 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27413 created in a disabled state. The @samp{regexp} argument is a regular
27414 expression used to match the name of the unloaded library.
27416 @subsubheading @value{GDBN} Command
27418 The corresponding @value{GDBN} command is @samp{catch unload}.
27420 @subsubheading Example
27423 -catch-unload -d bar.so
27424 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27425 what="load of library matching bar.so",catch-type="unload",times="0"@}
27429 @node Ada Exception GDB/MI Catchpoint Commands
27430 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27432 The following @sc{gdb/mi} commands can be used to create catchpoints
27433 that stop the execution when Ada exceptions are being raised.
27435 @subheading The @code{-catch-assert} Command
27436 @findex -catch-assert
27438 @subsubheading Synopsis
27441 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27444 Add a catchpoint for failed Ada assertions.
27446 The possible optional parameters for this command are:
27449 @item -c @var{condition}
27450 Make the catchpoint conditional on @var{condition}.
27452 Create a disabled catchpoint.
27454 Create a temporary catchpoint.
27457 @subsubheading @value{GDBN} Command
27459 The corresponding @value{GDBN} command is @samp{catch assert}.
27461 @subsubheading Example
27465 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27466 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27467 thread-groups=["i1"],times="0",
27468 original-location="__gnat_debug_raise_assert_failure"@}
27472 @subheading The @code{-catch-exception} Command
27473 @findex -catch-exception
27475 @subsubheading Synopsis
27478 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27482 Add a catchpoint stopping when Ada exceptions are raised.
27483 By default, the command stops the program when any Ada exception
27484 gets raised. But it is also possible, by using some of the
27485 optional parameters described below, to create more selective
27488 The possible optional parameters for this command are:
27491 @item -c @var{condition}
27492 Make the catchpoint conditional on @var{condition}.
27494 Create a disabled catchpoint.
27495 @item -e @var{exception-name}
27496 Only stop when @var{exception-name} is raised. This option cannot
27497 be used combined with @samp{-u}.
27499 Create a temporary catchpoint.
27501 Stop only when an unhandled exception gets raised. This option
27502 cannot be used combined with @samp{-e}.
27505 @subsubheading @value{GDBN} Command
27507 The corresponding @value{GDBN} commands are @samp{catch exception}
27508 and @samp{catch exception unhandled}.
27510 @subsubheading Example
27513 -catch-exception -e Program_Error
27514 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27515 enabled="y",addr="0x0000000000404874",
27516 what="`Program_Error' Ada exception", thread-groups=["i1"],
27517 times="0",original-location="__gnat_debug_raise_exception"@}
27521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27522 @node GDB/MI Program Context
27523 @section @sc{gdb/mi} Program Context
27525 @subheading The @code{-exec-arguments} Command
27526 @findex -exec-arguments
27529 @subsubheading Synopsis
27532 -exec-arguments @var{args}
27535 Set the inferior program arguments, to be used in the next
27538 @subsubheading @value{GDBN} Command
27540 The corresponding @value{GDBN} command is @samp{set args}.
27542 @subsubheading Example
27546 -exec-arguments -v word
27553 @subheading The @code{-exec-show-arguments} Command
27554 @findex -exec-show-arguments
27556 @subsubheading Synopsis
27559 -exec-show-arguments
27562 Print the arguments of the program.
27564 @subsubheading @value{GDBN} Command
27566 The corresponding @value{GDBN} command is @samp{show args}.
27568 @subsubheading Example
27573 @subheading The @code{-environment-cd} Command
27574 @findex -environment-cd
27576 @subsubheading Synopsis
27579 -environment-cd @var{pathdir}
27582 Set @value{GDBN}'s working directory.
27584 @subsubheading @value{GDBN} Command
27586 The corresponding @value{GDBN} command is @samp{cd}.
27588 @subsubheading Example
27592 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27598 @subheading The @code{-environment-directory} Command
27599 @findex -environment-directory
27601 @subsubheading Synopsis
27604 -environment-directory [ -r ] [ @var{pathdir} ]+
27607 Add directories @var{pathdir} to beginning of search path for source files.
27608 If the @samp{-r} option is used, the search path is reset to the default
27609 search path. If directories @var{pathdir} are supplied in addition to the
27610 @samp{-r} option, the search path is first reset and then addition
27612 Multiple directories may be specified, separated by blanks. Specifying
27613 multiple directories in a single command
27614 results in the directories added to the beginning of the
27615 search path in the same order they were presented in the command.
27616 If blanks are needed as
27617 part of a directory name, double-quotes should be used around
27618 the name. In the command output, the path will show up separated
27619 by the system directory-separator character. The directory-separator
27620 character must not be used
27621 in any directory name.
27622 If no directories are specified, the current search path is displayed.
27624 @subsubheading @value{GDBN} Command
27626 The corresponding @value{GDBN} command is @samp{dir}.
27628 @subsubheading Example
27632 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27633 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27635 -environment-directory ""
27636 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27638 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27639 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27641 -environment-directory -r
27642 ^done,source-path="$cdir:$cwd"
27647 @subheading The @code{-environment-path} Command
27648 @findex -environment-path
27650 @subsubheading Synopsis
27653 -environment-path [ -r ] [ @var{pathdir} ]+
27656 Add directories @var{pathdir} to beginning of search path for object files.
27657 If the @samp{-r} option is used, the search path is reset to the original
27658 search path that existed at gdb start-up. If directories @var{pathdir} are
27659 supplied in addition to the
27660 @samp{-r} option, the search path is first reset and then addition
27662 Multiple directories may be specified, separated by blanks. Specifying
27663 multiple directories in a single command
27664 results in the directories added to the beginning of the
27665 search path in the same order they were presented in the command.
27666 If blanks are needed as
27667 part of a directory name, double-quotes should be used around
27668 the name. In the command output, the path will show up separated
27669 by the system directory-separator character. The directory-separator
27670 character must not be used
27671 in any directory name.
27672 If no directories are specified, the current path is displayed.
27675 @subsubheading @value{GDBN} Command
27677 The corresponding @value{GDBN} command is @samp{path}.
27679 @subsubheading Example
27684 ^done,path="/usr/bin"
27686 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27687 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27689 -environment-path -r /usr/local/bin
27690 ^done,path="/usr/local/bin:/usr/bin"
27695 @subheading The @code{-environment-pwd} Command
27696 @findex -environment-pwd
27698 @subsubheading Synopsis
27704 Show the current working directory.
27706 @subsubheading @value{GDBN} Command
27708 The corresponding @value{GDBN} command is @samp{pwd}.
27710 @subsubheading Example
27715 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27720 @node GDB/MI Thread Commands
27721 @section @sc{gdb/mi} Thread Commands
27724 @subheading The @code{-thread-info} Command
27725 @findex -thread-info
27727 @subsubheading Synopsis
27730 -thread-info [ @var{thread-id} ]
27733 Reports information about either a specific thread, if the
27734 @var{thread-id} parameter is present, or about all threads.
27735 @var{thread-id} is the thread's global thread ID. When printing
27736 information about all threads, also reports the global ID of the
27739 @subsubheading @value{GDBN} Command
27741 The @samp{info thread} command prints the same information
27744 @subsubheading Result
27746 The result is a list of threads. The following attributes are
27747 defined for a given thread:
27751 This field exists only for the current thread. It has the value @samp{*}.
27754 The global identifier that @value{GDBN} uses to refer to the thread.
27757 The identifier that the target uses to refer to the thread.
27760 Extra information about the thread, in a target-specific format. This
27764 The name of the thread. If the user specified a name using the
27765 @code{thread name} command, then this name is given. Otherwise, if
27766 @value{GDBN} can extract the thread name from the target, then that
27767 name is given. If @value{GDBN} cannot find the thread name, then this
27771 The stack frame currently executing in the thread.
27774 The thread's state. The @samp{state} field may have the following
27779 The thread is stopped. Frame information is available for stopped
27783 The thread is running. There's no frame information for running
27789 If @value{GDBN} can find the CPU core on which this thread is running,
27790 then this field is the core identifier. This field is optional.
27794 @subsubheading Example
27799 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27800 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27801 args=[]@},state="running"@},
27802 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27803 frame=@{level="0",addr="0x0804891f",func="foo",
27804 args=[@{name="i",value="10"@}],
27805 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27806 state="running"@}],
27807 current-thread-id="1"
27811 @subheading The @code{-thread-list-ids} Command
27812 @findex -thread-list-ids
27814 @subsubheading Synopsis
27820 Produces a list of the currently known global @value{GDBN} thread ids.
27821 At the end of the list it also prints the total number of such
27824 This command is retained for historical reasons, the
27825 @code{-thread-info} command should be used instead.
27827 @subsubheading @value{GDBN} Command
27829 Part of @samp{info threads} supplies the same information.
27831 @subsubheading Example
27836 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27837 current-thread-id="1",number-of-threads="3"
27842 @subheading The @code{-thread-select} Command
27843 @findex -thread-select
27845 @subsubheading Synopsis
27848 -thread-select @var{thread-id}
27851 Make thread with global thread number @var{thread-id} the current
27852 thread. It prints the number of the new current thread, and the
27853 topmost frame for that thread.
27855 This command is deprecated in favor of explicitly using the
27856 @samp{--thread} option to each command.
27858 @subsubheading @value{GDBN} Command
27860 The corresponding @value{GDBN} command is @samp{thread}.
27862 @subsubheading Example
27869 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27870 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27874 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27875 number-of-threads="3"
27878 ^done,new-thread-id="3",
27879 frame=@{level="0",func="vprintf",
27880 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27881 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27886 @node GDB/MI Ada Tasking Commands
27887 @section @sc{gdb/mi} Ada Tasking Commands
27889 @subheading The @code{-ada-task-info} Command
27890 @findex -ada-task-info
27892 @subsubheading Synopsis
27895 -ada-task-info [ @var{task-id} ]
27898 Reports information about either a specific Ada task, if the
27899 @var{task-id} parameter is present, or about all Ada tasks.
27901 @subsubheading @value{GDBN} Command
27903 The @samp{info tasks} command prints the same information
27904 about all Ada tasks (@pxref{Ada Tasks}).
27906 @subsubheading Result
27908 The result is a table of Ada tasks. The following columns are
27909 defined for each Ada task:
27913 This field exists only for the current thread. It has the value @samp{*}.
27916 The identifier that @value{GDBN} uses to refer to the Ada task.
27919 The identifier that the target uses to refer to the Ada task.
27922 The global thread identifier of the thread corresponding to the Ada
27925 This field should always exist, as Ada tasks are always implemented
27926 on top of a thread. But if @value{GDBN} cannot find this corresponding
27927 thread for any reason, the field is omitted.
27930 This field exists only when the task was created by another task.
27931 In this case, it provides the ID of the parent task.
27934 The base priority of the task.
27937 The current state of the task. For a detailed description of the
27938 possible states, see @ref{Ada Tasks}.
27941 The name of the task.
27945 @subsubheading Example
27949 ^done,tasks=@{nr_rows="3",nr_cols="8",
27950 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27951 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27952 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27953 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27954 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27955 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27956 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27957 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27958 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27959 state="Child Termination Wait",name="main_task"@}]@}
27963 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27964 @node GDB/MI Program Execution
27965 @section @sc{gdb/mi} Program Execution
27967 These are the asynchronous commands which generate the out-of-band
27968 record @samp{*stopped}. Currently @value{GDBN} only really executes
27969 asynchronously with remote targets and this interaction is mimicked in
27972 @subheading The @code{-exec-continue} Command
27973 @findex -exec-continue
27975 @subsubheading Synopsis
27978 -exec-continue [--reverse] [--all|--thread-group N]
27981 Resumes the execution of the inferior program, which will continue
27982 to execute until it reaches a debugger stop event. If the
27983 @samp{--reverse} option is specified, execution resumes in reverse until
27984 it reaches a stop event. Stop events may include
27987 breakpoints or watchpoints
27989 signals or exceptions
27991 the end of the process (or its beginning under @samp{--reverse})
27993 the end or beginning of a replay log if one is being used.
27995 In all-stop mode (@pxref{All-Stop
27996 Mode}), may resume only one thread, or all threads, depending on the
27997 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27998 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27999 ignored in all-stop mode. If the @samp{--thread-group} options is
28000 specified, then all threads in that thread group are resumed.
28002 @subsubheading @value{GDBN} Command
28004 The corresponding @value{GDBN} corresponding is @samp{continue}.
28006 @subsubheading Example
28013 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28014 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28020 @subheading The @code{-exec-finish} Command
28021 @findex -exec-finish
28023 @subsubheading Synopsis
28026 -exec-finish [--reverse]
28029 Resumes the execution of the inferior program until the current
28030 function is exited. Displays the results returned by the function.
28031 If the @samp{--reverse} option is specified, resumes the reverse
28032 execution of the inferior program until the point where current
28033 function was called.
28035 @subsubheading @value{GDBN} Command
28037 The corresponding @value{GDBN} command is @samp{finish}.
28039 @subsubheading Example
28041 Function returning @code{void}.
28048 *stopped,reason="function-finished",frame=@{func="main",args=[],
28049 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28053 Function returning other than @code{void}. The name of the internal
28054 @value{GDBN} variable storing the result is printed, together with the
28061 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28062 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28063 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28064 gdb-result-var="$1",return-value="0"
28069 @subheading The @code{-exec-interrupt} Command
28070 @findex -exec-interrupt
28072 @subsubheading Synopsis
28075 -exec-interrupt [--all|--thread-group N]
28078 Interrupts the background execution of the target. Note how the token
28079 associated with the stop message is the one for the execution command
28080 that has been interrupted. The token for the interrupt itself only
28081 appears in the @samp{^done} output. If the user is trying to
28082 interrupt a non-running program, an error message will be printed.
28084 Note that when asynchronous execution is enabled, this command is
28085 asynchronous just like other execution commands. That is, first the
28086 @samp{^done} response will be printed, and the target stop will be
28087 reported after that using the @samp{*stopped} notification.
28089 In non-stop mode, only the context thread is interrupted by default.
28090 All threads (in all inferiors) will be interrupted if the
28091 @samp{--all} option is specified. If the @samp{--thread-group}
28092 option is specified, all threads in that group will be interrupted.
28094 @subsubheading @value{GDBN} Command
28096 The corresponding @value{GDBN} command is @samp{interrupt}.
28098 @subsubheading Example
28109 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28110 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28111 fullname="/home/foo/bar/try.c",line="13"@}
28116 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28120 @subheading The @code{-exec-jump} Command
28123 @subsubheading Synopsis
28126 -exec-jump @var{location}
28129 Resumes execution of the inferior program at the location specified by
28130 parameter. @xref{Specify Location}, for a description of the
28131 different forms of @var{location}.
28133 @subsubheading @value{GDBN} Command
28135 The corresponding @value{GDBN} command is @samp{jump}.
28137 @subsubheading Example
28140 -exec-jump foo.c:10
28141 *running,thread-id="all"
28146 @subheading The @code{-exec-next} Command
28149 @subsubheading Synopsis
28152 -exec-next [--reverse]
28155 Resumes execution of the inferior program, stopping when the beginning
28156 of the next source line is reached.
28158 If the @samp{--reverse} option is specified, resumes reverse execution
28159 of the inferior program, stopping at the beginning of the previous
28160 source line. If you issue this command on the first line of a
28161 function, it will take you back to the caller of that function, to the
28162 source line where the function was called.
28165 @subsubheading @value{GDBN} Command
28167 The corresponding @value{GDBN} command is @samp{next}.
28169 @subsubheading Example
28175 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28180 @subheading The @code{-exec-next-instruction} Command
28181 @findex -exec-next-instruction
28183 @subsubheading Synopsis
28186 -exec-next-instruction [--reverse]
28189 Executes one machine instruction. If the instruction is a function
28190 call, continues until the function returns. If the program stops at an
28191 instruction in the middle of a source line, the address will be
28194 If the @samp{--reverse} option is specified, resumes reverse execution
28195 of the inferior program, stopping at the previous instruction. If the
28196 previously executed instruction was a return from another function,
28197 it will continue to execute in reverse until the call to that function
28198 (from the current stack frame) is reached.
28200 @subsubheading @value{GDBN} Command
28202 The corresponding @value{GDBN} command is @samp{nexti}.
28204 @subsubheading Example
28208 -exec-next-instruction
28212 *stopped,reason="end-stepping-range",
28213 addr="0x000100d4",line="5",file="hello.c"
28218 @subheading The @code{-exec-return} Command
28219 @findex -exec-return
28221 @subsubheading Synopsis
28227 Makes current function return immediately. Doesn't execute the inferior.
28228 Displays the new current frame.
28230 @subsubheading @value{GDBN} Command
28232 The corresponding @value{GDBN} command is @samp{return}.
28234 @subsubheading Example
28238 200-break-insert callee4
28239 200^done,bkpt=@{number="1",addr="0x00010734",
28240 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28245 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28246 frame=@{func="callee4",args=[],
28247 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28248 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28254 111^done,frame=@{level="0",func="callee3",
28255 args=[@{name="strarg",
28256 value="0x11940 \"A string argument.\""@}],
28257 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28258 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28263 @subheading The @code{-exec-run} Command
28266 @subsubheading Synopsis
28269 -exec-run [ --all | --thread-group N ] [ --start ]
28272 Starts execution of the inferior from the beginning. The inferior
28273 executes until either a breakpoint is encountered or the program
28274 exits. In the latter case the output will include an exit code, if
28275 the program has exited exceptionally.
28277 When neither the @samp{--all} nor the @samp{--thread-group} option
28278 is specified, the current inferior is started. If the
28279 @samp{--thread-group} option is specified, it should refer to a thread
28280 group of type @samp{process}, and that thread group will be started.
28281 If the @samp{--all} option is specified, then all inferiors will be started.
28283 Using the @samp{--start} option instructs the debugger to stop
28284 the execution at the start of the inferior's main subprogram,
28285 following the same behavior as the @code{start} command
28286 (@pxref{Starting}).
28288 @subsubheading @value{GDBN} Command
28290 The corresponding @value{GDBN} command is @samp{run}.
28292 @subsubheading Examples
28297 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28302 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28303 frame=@{func="main",args=[],file="recursive2.c",
28304 fullname="/home/foo/bar/recursive2.c",line="4"@}
28309 Program exited normally:
28317 *stopped,reason="exited-normally"
28322 Program exited exceptionally:
28330 *stopped,reason="exited",exit-code="01"
28334 Another way the program can terminate is if it receives a signal such as
28335 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28339 *stopped,reason="exited-signalled",signal-name="SIGINT",
28340 signal-meaning="Interrupt"
28344 @c @subheading -exec-signal
28347 @subheading The @code{-exec-step} Command
28350 @subsubheading Synopsis
28353 -exec-step [--reverse]
28356 Resumes execution of the inferior program, stopping when the beginning
28357 of the next source line is reached, if the next source line is not a
28358 function call. If it is, stop at the first instruction of the called
28359 function. If the @samp{--reverse} option is specified, resumes reverse
28360 execution of the inferior program, stopping at the beginning of the
28361 previously executed source line.
28363 @subsubheading @value{GDBN} Command
28365 The corresponding @value{GDBN} command is @samp{step}.
28367 @subsubheading Example
28369 Stepping into a function:
28375 *stopped,reason="end-stepping-range",
28376 frame=@{func="foo",args=[@{name="a",value="10"@},
28377 @{name="b",value="0"@}],file="recursive2.c",
28378 fullname="/home/foo/bar/recursive2.c",line="11"@}
28388 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28393 @subheading The @code{-exec-step-instruction} Command
28394 @findex -exec-step-instruction
28396 @subsubheading Synopsis
28399 -exec-step-instruction [--reverse]
28402 Resumes the inferior which executes one machine instruction. If the
28403 @samp{--reverse} option is specified, resumes reverse execution of the
28404 inferior program, stopping at the previously executed instruction.
28405 The output, once @value{GDBN} has stopped, will vary depending on
28406 whether we have stopped in the middle of a source line or not. In the
28407 former case, the address at which the program stopped will be printed
28410 @subsubheading @value{GDBN} Command
28412 The corresponding @value{GDBN} command is @samp{stepi}.
28414 @subsubheading Example
28418 -exec-step-instruction
28422 *stopped,reason="end-stepping-range",
28423 frame=@{func="foo",args=[],file="try.c",
28424 fullname="/home/foo/bar/try.c",line="10"@}
28426 -exec-step-instruction
28430 *stopped,reason="end-stepping-range",
28431 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28432 fullname="/home/foo/bar/try.c",line="10"@}
28437 @subheading The @code{-exec-until} Command
28438 @findex -exec-until
28440 @subsubheading Synopsis
28443 -exec-until [ @var{location} ]
28446 Executes the inferior until the @var{location} specified in the
28447 argument is reached. If there is no argument, the inferior executes
28448 until a source line greater than the current one is reached. The
28449 reason for stopping in this case will be @samp{location-reached}.
28451 @subsubheading @value{GDBN} Command
28453 The corresponding @value{GDBN} command is @samp{until}.
28455 @subsubheading Example
28459 -exec-until recursive2.c:6
28463 *stopped,reason="location-reached",frame=@{func="main",args=[],
28464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28469 @subheading -file-clear
28470 Is this going away????
28473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28474 @node GDB/MI Stack Manipulation
28475 @section @sc{gdb/mi} Stack Manipulation Commands
28477 @subheading The @code{-enable-frame-filters} Command
28478 @findex -enable-frame-filters
28481 -enable-frame-filters
28484 @value{GDBN} allows Python-based frame filters to affect the output of
28485 the MI commands relating to stack traces. As there is no way to
28486 implement this in a fully backward-compatible way, a front end must
28487 request that this functionality be enabled.
28489 Once enabled, this feature cannot be disabled.
28491 Note that if Python support has not been compiled into @value{GDBN},
28492 this command will still succeed (and do nothing).
28494 @subheading The @code{-stack-info-frame} Command
28495 @findex -stack-info-frame
28497 @subsubheading Synopsis
28503 Get info on the selected frame.
28505 @subsubheading @value{GDBN} Command
28507 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28508 (without arguments).
28510 @subsubheading Example
28515 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28521 @subheading The @code{-stack-info-depth} Command
28522 @findex -stack-info-depth
28524 @subsubheading Synopsis
28527 -stack-info-depth [ @var{max-depth} ]
28530 Return the depth of the stack. If the integer argument @var{max-depth}
28531 is specified, do not count beyond @var{max-depth} frames.
28533 @subsubheading @value{GDBN} Command
28535 There's no equivalent @value{GDBN} command.
28537 @subsubheading Example
28539 For a stack with frame levels 0 through 11:
28546 -stack-info-depth 4
28549 -stack-info-depth 12
28552 -stack-info-depth 11
28555 -stack-info-depth 13
28560 @anchor{-stack-list-arguments}
28561 @subheading The @code{-stack-list-arguments} Command
28562 @findex -stack-list-arguments
28564 @subsubheading Synopsis
28567 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28568 [ @var{low-frame} @var{high-frame} ]
28571 Display a list of the arguments for the frames between @var{low-frame}
28572 and @var{high-frame} (inclusive). If @var{low-frame} and
28573 @var{high-frame} are not provided, list the arguments for the whole
28574 call stack. If the two arguments are equal, show the single frame
28575 at the corresponding level. It is an error if @var{low-frame} is
28576 larger than the actual number of frames. On the other hand,
28577 @var{high-frame} may be larger than the actual number of frames, in
28578 which case only existing frames will be returned.
28580 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28581 the variables; if it is 1 or @code{--all-values}, print also their
28582 values; and if it is 2 or @code{--simple-values}, print the name,
28583 type and value for simple data types, and the name and type for arrays,
28584 structures and unions. If the option @code{--no-frame-filters} is
28585 supplied, then Python frame filters will not be executed.
28587 If the @code{--skip-unavailable} option is specified, arguments that
28588 are not available are not listed. Partially available arguments
28589 are still displayed, however.
28591 Use of this command to obtain arguments in a single frame is
28592 deprecated in favor of the @samp{-stack-list-variables} command.
28594 @subsubheading @value{GDBN} Command
28596 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28597 @samp{gdb_get_args} command which partially overlaps with the
28598 functionality of @samp{-stack-list-arguments}.
28600 @subsubheading Example
28607 frame=@{level="0",addr="0x00010734",func="callee4",
28608 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28609 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28610 frame=@{level="1",addr="0x0001076c",func="callee3",
28611 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28612 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28613 frame=@{level="2",addr="0x0001078c",func="callee2",
28614 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28615 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28616 frame=@{level="3",addr="0x000107b4",func="callee1",
28617 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28618 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28619 frame=@{level="4",addr="0x000107e0",func="main",
28620 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28621 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28623 -stack-list-arguments 0
28626 frame=@{level="0",args=[]@},
28627 frame=@{level="1",args=[name="strarg"]@},
28628 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28629 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28630 frame=@{level="4",args=[]@}]
28632 -stack-list-arguments 1
28635 frame=@{level="0",args=[]@},
28637 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28638 frame=@{level="2",args=[
28639 @{name="intarg",value="2"@},
28640 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28641 @{frame=@{level="3",args=[
28642 @{name="intarg",value="2"@},
28643 @{name="strarg",value="0x11940 \"A string argument.\""@},
28644 @{name="fltarg",value="3.5"@}]@},
28645 frame=@{level="4",args=[]@}]
28647 -stack-list-arguments 0 2 2
28648 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28650 -stack-list-arguments 1 2 2
28651 ^done,stack-args=[frame=@{level="2",
28652 args=[@{name="intarg",value="2"@},
28653 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28657 @c @subheading -stack-list-exception-handlers
28660 @anchor{-stack-list-frames}
28661 @subheading The @code{-stack-list-frames} Command
28662 @findex -stack-list-frames
28664 @subsubheading Synopsis
28667 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28670 List the frames currently on the stack. For each frame it displays the
28675 The frame number, 0 being the topmost frame, i.e., the innermost function.
28677 The @code{$pc} value for that frame.
28681 File name of the source file where the function lives.
28682 @item @var{fullname}
28683 The full file name of the source file where the function lives.
28685 Line number corresponding to the @code{$pc}.
28687 The shared library where this function is defined. This is only given
28688 if the frame's function is not known.
28691 If invoked without arguments, this command prints a backtrace for the
28692 whole stack. If given two integer arguments, it shows the frames whose
28693 levels are between the two arguments (inclusive). If the two arguments
28694 are equal, it shows the single frame at the corresponding level. It is
28695 an error if @var{low-frame} is larger than the actual number of
28696 frames. On the other hand, @var{high-frame} may be larger than the
28697 actual number of frames, in which case only existing frames will be
28698 returned. If the option @code{--no-frame-filters} is supplied, then
28699 Python frame filters will not be executed.
28701 @subsubheading @value{GDBN} Command
28703 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28705 @subsubheading Example
28707 Full stack backtrace:
28713 [frame=@{level="0",addr="0x0001076c",func="foo",
28714 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28715 frame=@{level="1",addr="0x000107a4",func="foo",
28716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28717 frame=@{level="2",addr="0x000107a4",func="foo",
28718 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28719 frame=@{level="3",addr="0x000107a4",func="foo",
28720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28721 frame=@{level="4",addr="0x000107a4",func="foo",
28722 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28723 frame=@{level="5",addr="0x000107a4",func="foo",
28724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28725 frame=@{level="6",addr="0x000107a4",func="foo",
28726 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28727 frame=@{level="7",addr="0x000107a4",func="foo",
28728 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28729 frame=@{level="8",addr="0x000107a4",func="foo",
28730 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28731 frame=@{level="9",addr="0x000107a4",func="foo",
28732 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28733 frame=@{level="10",addr="0x000107a4",func="foo",
28734 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28735 frame=@{level="11",addr="0x00010738",func="main",
28736 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28740 Show frames between @var{low_frame} and @var{high_frame}:
28744 -stack-list-frames 3 5
28746 [frame=@{level="3",addr="0x000107a4",func="foo",
28747 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28748 frame=@{level="4",addr="0x000107a4",func="foo",
28749 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28750 frame=@{level="5",addr="0x000107a4",func="foo",
28751 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28755 Show a single frame:
28759 -stack-list-frames 3 3
28761 [frame=@{level="3",addr="0x000107a4",func="foo",
28762 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28767 @subheading The @code{-stack-list-locals} Command
28768 @findex -stack-list-locals
28769 @anchor{-stack-list-locals}
28771 @subsubheading Synopsis
28774 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28777 Display the local variable names for the selected frame. If
28778 @var{print-values} is 0 or @code{--no-values}, print only the names of
28779 the variables; if it is 1 or @code{--all-values}, print also their
28780 values; and if it is 2 or @code{--simple-values}, print the name,
28781 type and value for simple data types, and the name and type for arrays,
28782 structures and unions. In this last case, a frontend can immediately
28783 display the value of simple data types and create variable objects for
28784 other data types when the user wishes to explore their values in
28785 more detail. If the option @code{--no-frame-filters} is supplied, then
28786 Python frame filters will not be executed.
28788 If the @code{--skip-unavailable} option is specified, local variables
28789 that are not available are not listed. Partially available local
28790 variables are still displayed, however.
28792 This command is deprecated in favor of the
28793 @samp{-stack-list-variables} command.
28795 @subsubheading @value{GDBN} Command
28797 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28799 @subsubheading Example
28803 -stack-list-locals 0
28804 ^done,locals=[name="A",name="B",name="C"]
28806 -stack-list-locals --all-values
28807 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28808 @{name="C",value="@{1, 2, 3@}"@}]
28809 -stack-list-locals --simple-values
28810 ^done,locals=[@{name="A",type="int",value="1"@},
28811 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28815 @anchor{-stack-list-variables}
28816 @subheading The @code{-stack-list-variables} Command
28817 @findex -stack-list-variables
28819 @subsubheading Synopsis
28822 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28825 Display the names of local variables and function arguments for the selected frame. If
28826 @var{print-values} is 0 or @code{--no-values}, print only the names of
28827 the variables; if it is 1 or @code{--all-values}, print also their
28828 values; and if it is 2 or @code{--simple-values}, print the name,
28829 type and value for simple data types, and the name and type for arrays,
28830 structures and unions. If the option @code{--no-frame-filters} is
28831 supplied, then Python frame filters will not be executed.
28833 If the @code{--skip-unavailable} option is specified, local variables
28834 and arguments that are not available are not listed. Partially
28835 available arguments and local variables are still displayed, however.
28837 @subsubheading Example
28841 -stack-list-variables --thread 1 --frame 0 --all-values
28842 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28847 @subheading The @code{-stack-select-frame} Command
28848 @findex -stack-select-frame
28850 @subsubheading Synopsis
28853 -stack-select-frame @var{framenum}
28856 Change the selected frame. Select a different frame @var{framenum} on
28859 This command in deprecated in favor of passing the @samp{--frame}
28860 option to every command.
28862 @subsubheading @value{GDBN} Command
28864 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28865 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28867 @subsubheading Example
28871 -stack-select-frame 2
28876 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28877 @node GDB/MI Variable Objects
28878 @section @sc{gdb/mi} Variable Objects
28882 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28884 For the implementation of a variable debugger window (locals, watched
28885 expressions, etc.), we are proposing the adaptation of the existing code
28886 used by @code{Insight}.
28888 The two main reasons for that are:
28892 It has been proven in practice (it is already on its second generation).
28895 It will shorten development time (needless to say how important it is
28899 The original interface was designed to be used by Tcl code, so it was
28900 slightly changed so it could be used through @sc{gdb/mi}. This section
28901 describes the @sc{gdb/mi} operations that will be available and gives some
28902 hints about their use.
28904 @emph{Note}: In addition to the set of operations described here, we
28905 expect the @sc{gui} implementation of a variable window to require, at
28906 least, the following operations:
28909 @item @code{-gdb-show} @code{output-radix}
28910 @item @code{-stack-list-arguments}
28911 @item @code{-stack-list-locals}
28912 @item @code{-stack-select-frame}
28917 @subheading Introduction to Variable Objects
28919 @cindex variable objects in @sc{gdb/mi}
28921 Variable objects are "object-oriented" MI interface for examining and
28922 changing values of expressions. Unlike some other MI interfaces that
28923 work with expressions, variable objects are specifically designed for
28924 simple and efficient presentation in the frontend. A variable object
28925 is identified by string name. When a variable object is created, the
28926 frontend specifies the expression for that variable object. The
28927 expression can be a simple variable, or it can be an arbitrary complex
28928 expression, and can even involve CPU registers. After creating a
28929 variable object, the frontend can invoke other variable object
28930 operations---for example to obtain or change the value of a variable
28931 object, or to change display format.
28933 Variable objects have hierarchical tree structure. Any variable object
28934 that corresponds to a composite type, such as structure in C, has
28935 a number of child variable objects, for example corresponding to each
28936 element of a structure. A child variable object can itself have
28937 children, recursively. Recursion ends when we reach
28938 leaf variable objects, which always have built-in types. Child variable
28939 objects are created only by explicit request, so if a frontend
28940 is not interested in the children of a particular variable object, no
28941 child will be created.
28943 For a leaf variable object it is possible to obtain its value as a
28944 string, or set the value from a string. String value can be also
28945 obtained for a non-leaf variable object, but it's generally a string
28946 that only indicates the type of the object, and does not list its
28947 contents. Assignment to a non-leaf variable object is not allowed.
28949 A frontend does not need to read the values of all variable objects each time
28950 the program stops. Instead, MI provides an update command that lists all
28951 variable objects whose values has changed since the last update
28952 operation. This considerably reduces the amount of data that must
28953 be transferred to the frontend. As noted above, children variable
28954 objects are created on demand, and only leaf variable objects have a
28955 real value. As result, gdb will read target memory only for leaf
28956 variables that frontend has created.
28958 The automatic update is not always desirable. For example, a frontend
28959 might want to keep a value of some expression for future reference,
28960 and never update it. For another example, fetching memory is
28961 relatively slow for embedded targets, so a frontend might want
28962 to disable automatic update for the variables that are either not
28963 visible on the screen, or ``closed''. This is possible using so
28964 called ``frozen variable objects''. Such variable objects are never
28965 implicitly updated.
28967 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28968 fixed variable object, the expression is parsed when the variable
28969 object is created, including associating identifiers to specific
28970 variables. The meaning of expression never changes. For a floating
28971 variable object the values of variables whose names appear in the
28972 expressions are re-evaluated every time in the context of the current
28973 frame. Consider this example:
28978 struct work_state state;
28985 If a fixed variable object for the @code{state} variable is created in
28986 this function, and we enter the recursive call, the variable
28987 object will report the value of @code{state} in the top-level
28988 @code{do_work} invocation. On the other hand, a floating variable
28989 object will report the value of @code{state} in the current frame.
28991 If an expression specified when creating a fixed variable object
28992 refers to a local variable, the variable object becomes bound to the
28993 thread and frame in which the variable object is created. When such
28994 variable object is updated, @value{GDBN} makes sure that the
28995 thread/frame combination the variable object is bound to still exists,
28996 and re-evaluates the variable object in context of that thread/frame.
28998 The following is the complete set of @sc{gdb/mi} operations defined to
28999 access this functionality:
29001 @multitable @columnfractions .4 .6
29002 @item @strong{Operation}
29003 @tab @strong{Description}
29005 @item @code{-enable-pretty-printing}
29006 @tab enable Python-based pretty-printing
29007 @item @code{-var-create}
29008 @tab create a variable object
29009 @item @code{-var-delete}
29010 @tab delete the variable object and/or its children
29011 @item @code{-var-set-format}
29012 @tab set the display format of this variable
29013 @item @code{-var-show-format}
29014 @tab show the display format of this variable
29015 @item @code{-var-info-num-children}
29016 @tab tells how many children this object has
29017 @item @code{-var-list-children}
29018 @tab return a list of the object's children
29019 @item @code{-var-info-type}
29020 @tab show the type of this variable object
29021 @item @code{-var-info-expression}
29022 @tab print parent-relative expression that this variable object represents
29023 @item @code{-var-info-path-expression}
29024 @tab print full expression that this variable object represents
29025 @item @code{-var-show-attributes}
29026 @tab is this variable editable? does it exist here?
29027 @item @code{-var-evaluate-expression}
29028 @tab get the value of this variable
29029 @item @code{-var-assign}
29030 @tab set the value of this variable
29031 @item @code{-var-update}
29032 @tab update the variable and its children
29033 @item @code{-var-set-frozen}
29034 @tab set frozeness attribute
29035 @item @code{-var-set-update-range}
29036 @tab set range of children to display on update
29039 In the next subsection we describe each operation in detail and suggest
29040 how it can be used.
29042 @subheading Description And Use of Operations on Variable Objects
29044 @subheading The @code{-enable-pretty-printing} Command
29045 @findex -enable-pretty-printing
29048 -enable-pretty-printing
29051 @value{GDBN} allows Python-based visualizers to affect the output of the
29052 MI variable object commands. However, because there was no way to
29053 implement this in a fully backward-compatible way, a front end must
29054 request that this functionality be enabled.
29056 Once enabled, this feature cannot be disabled.
29058 Note that if Python support has not been compiled into @value{GDBN},
29059 this command will still succeed (and do nothing).
29061 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29062 may work differently in future versions of @value{GDBN}.
29064 @subheading The @code{-var-create} Command
29065 @findex -var-create
29067 @subsubheading Synopsis
29070 -var-create @{@var{name} | "-"@}
29071 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29074 This operation creates a variable object, which allows the monitoring of
29075 a variable, the result of an expression, a memory cell or a CPU
29078 The @var{name} parameter is the string by which the object can be
29079 referenced. It must be unique. If @samp{-} is specified, the varobj
29080 system will generate a string ``varNNNNNN'' automatically. It will be
29081 unique provided that one does not specify @var{name} of that format.
29082 The command fails if a duplicate name is found.
29084 The frame under which the expression should be evaluated can be
29085 specified by @var{frame-addr}. A @samp{*} indicates that the current
29086 frame should be used. A @samp{@@} indicates that a floating variable
29087 object must be created.
29089 @var{expression} is any expression valid on the current language set (must not
29090 begin with a @samp{*}), or one of the following:
29094 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29097 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29100 @samp{$@var{regname}} --- a CPU register name
29103 @cindex dynamic varobj
29104 A varobj's contents may be provided by a Python-based pretty-printer. In this
29105 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29106 have slightly different semantics in some cases. If the
29107 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29108 will never create a dynamic varobj. This ensures backward
29109 compatibility for existing clients.
29111 @subsubheading Result
29113 This operation returns attributes of the newly-created varobj. These
29118 The name of the varobj.
29121 The number of children of the varobj. This number is not necessarily
29122 reliable for a dynamic varobj. Instead, you must examine the
29123 @samp{has_more} attribute.
29126 The varobj's scalar value. For a varobj whose type is some sort of
29127 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29128 will not be interesting.
29131 The varobj's type. This is a string representation of the type, as
29132 would be printed by the @value{GDBN} CLI. If @samp{print object}
29133 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29134 @emph{actual} (derived) type of the object is shown rather than the
29135 @emph{declared} one.
29138 If a variable object is bound to a specific thread, then this is the
29139 thread's global identifier.
29142 For a dynamic varobj, this indicates whether there appear to be any
29143 children available. For a non-dynamic varobj, this will be 0.
29146 This attribute will be present and have the value @samp{1} if the
29147 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29148 then this attribute will not be present.
29151 A dynamic varobj can supply a display hint to the front end. The
29152 value comes directly from the Python pretty-printer object's
29153 @code{display_hint} method. @xref{Pretty Printing API}.
29156 Typical output will look like this:
29159 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29160 has_more="@var{has_more}"
29164 @subheading The @code{-var-delete} Command
29165 @findex -var-delete
29167 @subsubheading Synopsis
29170 -var-delete [ -c ] @var{name}
29173 Deletes a previously created variable object and all of its children.
29174 With the @samp{-c} option, just deletes the children.
29176 Returns an error if the object @var{name} is not found.
29179 @subheading The @code{-var-set-format} Command
29180 @findex -var-set-format
29182 @subsubheading Synopsis
29185 -var-set-format @var{name} @var{format-spec}
29188 Sets the output format for the value of the object @var{name} to be
29191 @anchor{-var-set-format}
29192 The syntax for the @var{format-spec} is as follows:
29195 @var{format-spec} @expansion{}
29196 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29199 The natural format is the default format choosen automatically
29200 based on the variable type (like decimal for an @code{int}, hex
29201 for pointers, etc.).
29203 The zero-hexadecimal format has a representation similar to hexadecimal
29204 but with padding zeroes to the left of the value. For example, a 32-bit
29205 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29206 zero-hexadecimal format.
29208 For a variable with children, the format is set only on the
29209 variable itself, and the children are not affected.
29211 @subheading The @code{-var-show-format} Command
29212 @findex -var-show-format
29214 @subsubheading Synopsis
29217 -var-show-format @var{name}
29220 Returns the format used to display the value of the object @var{name}.
29223 @var{format} @expansion{}
29228 @subheading The @code{-var-info-num-children} Command
29229 @findex -var-info-num-children
29231 @subsubheading Synopsis
29234 -var-info-num-children @var{name}
29237 Returns the number of children of a variable object @var{name}:
29243 Note that this number is not completely reliable for a dynamic varobj.
29244 It will return the current number of children, but more children may
29248 @subheading The @code{-var-list-children} Command
29249 @findex -var-list-children
29251 @subsubheading Synopsis
29254 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29256 @anchor{-var-list-children}
29258 Return a list of the children of the specified variable object and
29259 create variable objects for them, if they do not already exist. With
29260 a single argument or if @var{print-values} has a value of 0 or
29261 @code{--no-values}, print only the names of the variables; if
29262 @var{print-values} is 1 or @code{--all-values}, also print their
29263 values; and if it is 2 or @code{--simple-values} print the name and
29264 value for simple data types and just the name for arrays, structures
29267 @var{from} and @var{to}, if specified, indicate the range of children
29268 to report. If @var{from} or @var{to} is less than zero, the range is
29269 reset and all children will be reported. Otherwise, children starting
29270 at @var{from} (zero-based) and up to and excluding @var{to} will be
29273 If a child range is requested, it will only affect the current call to
29274 @code{-var-list-children}, but not future calls to @code{-var-update}.
29275 For this, you must instead use @code{-var-set-update-range}. The
29276 intent of this approach is to enable a front end to implement any
29277 update approach it likes; for example, scrolling a view may cause the
29278 front end to request more children with @code{-var-list-children}, and
29279 then the front end could call @code{-var-set-update-range} with a
29280 different range to ensure that future updates are restricted to just
29283 For each child the following results are returned:
29288 Name of the variable object created for this child.
29291 The expression to be shown to the user by the front end to designate this child.
29292 For example this may be the name of a structure member.
29294 For a dynamic varobj, this value cannot be used to form an
29295 expression. There is no way to do this at all with a dynamic varobj.
29297 For C/C@t{++} structures there are several pseudo children returned to
29298 designate access qualifiers. For these pseudo children @var{exp} is
29299 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29300 type and value are not present.
29302 A dynamic varobj will not report the access qualifying
29303 pseudo-children, regardless of the language. This information is not
29304 available at all with a dynamic varobj.
29307 Number of children this child has. For a dynamic varobj, this will be
29311 The type of the child. If @samp{print object}
29312 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29313 @emph{actual} (derived) type of the object is shown rather than the
29314 @emph{declared} one.
29317 If values were requested, this is the value.
29320 If this variable object is associated with a thread, this is the
29321 thread's global thread id. Otherwise this result is not present.
29324 If the variable object is frozen, this variable will be present with a value of 1.
29327 A dynamic varobj can supply a display hint to the front end. The
29328 value comes directly from the Python pretty-printer object's
29329 @code{display_hint} method. @xref{Pretty Printing API}.
29332 This attribute will be present and have the value @samp{1} if the
29333 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29334 then this attribute will not be present.
29338 The result may have its own attributes:
29342 A dynamic varobj can supply a display hint to the front end. The
29343 value comes directly from the Python pretty-printer object's
29344 @code{display_hint} method. @xref{Pretty Printing API}.
29347 This is an integer attribute which is nonzero if there are children
29348 remaining after the end of the selected range.
29351 @subsubheading Example
29355 -var-list-children n
29356 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29357 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29359 -var-list-children --all-values n
29360 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29361 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29365 @subheading The @code{-var-info-type} Command
29366 @findex -var-info-type
29368 @subsubheading Synopsis
29371 -var-info-type @var{name}
29374 Returns the type of the specified variable @var{name}. The type is
29375 returned as a string in the same format as it is output by the
29379 type=@var{typename}
29383 @subheading The @code{-var-info-expression} Command
29384 @findex -var-info-expression
29386 @subsubheading Synopsis
29389 -var-info-expression @var{name}
29392 Returns a string that is suitable for presenting this
29393 variable object in user interface. The string is generally
29394 not valid expression in the current language, and cannot be evaluated.
29396 For example, if @code{a} is an array, and variable object
29397 @code{A} was created for @code{a}, then we'll get this output:
29400 (gdb) -var-info-expression A.1
29401 ^done,lang="C",exp="1"
29405 Here, the value of @code{lang} is the language name, which can be
29406 found in @ref{Supported Languages}.
29408 Note that the output of the @code{-var-list-children} command also
29409 includes those expressions, so the @code{-var-info-expression} command
29412 @subheading The @code{-var-info-path-expression} Command
29413 @findex -var-info-path-expression
29415 @subsubheading Synopsis
29418 -var-info-path-expression @var{name}
29421 Returns an expression that can be evaluated in the current
29422 context and will yield the same value that a variable object has.
29423 Compare this with the @code{-var-info-expression} command, which
29424 result can be used only for UI presentation. Typical use of
29425 the @code{-var-info-path-expression} command is creating a
29426 watchpoint from a variable object.
29428 This command is currently not valid for children of a dynamic varobj,
29429 and will give an error when invoked on one.
29431 For example, suppose @code{C} is a C@t{++} class, derived from class
29432 @code{Base}, and that the @code{Base} class has a member called
29433 @code{m_size}. Assume a variable @code{c} is has the type of
29434 @code{C} and a variable object @code{C} was created for variable
29435 @code{c}. Then, we'll get this output:
29437 (gdb) -var-info-path-expression C.Base.public.m_size
29438 ^done,path_expr=((Base)c).m_size)
29441 @subheading The @code{-var-show-attributes} Command
29442 @findex -var-show-attributes
29444 @subsubheading Synopsis
29447 -var-show-attributes @var{name}
29450 List attributes of the specified variable object @var{name}:
29453 status=@var{attr} [ ( ,@var{attr} )* ]
29457 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29459 @subheading The @code{-var-evaluate-expression} Command
29460 @findex -var-evaluate-expression
29462 @subsubheading Synopsis
29465 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29468 Evaluates the expression that is represented by the specified variable
29469 object and returns its value as a string. The format of the string
29470 can be specified with the @samp{-f} option. The possible values of
29471 this option are the same as for @code{-var-set-format}
29472 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29473 the current display format will be used. The current display format
29474 can be changed using the @code{-var-set-format} command.
29480 Note that one must invoke @code{-var-list-children} for a variable
29481 before the value of a child variable can be evaluated.
29483 @subheading The @code{-var-assign} Command
29484 @findex -var-assign
29486 @subsubheading Synopsis
29489 -var-assign @var{name} @var{expression}
29492 Assigns the value of @var{expression} to the variable object specified
29493 by @var{name}. The object must be @samp{editable}. If the variable's
29494 value is altered by the assign, the variable will show up in any
29495 subsequent @code{-var-update} list.
29497 @subsubheading Example
29505 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29509 @subheading The @code{-var-update} Command
29510 @findex -var-update
29512 @subsubheading Synopsis
29515 -var-update [@var{print-values}] @{@var{name} | "*"@}
29518 Reevaluate the expressions corresponding to the variable object
29519 @var{name} and all its direct and indirect children, and return the
29520 list of variable objects whose values have changed; @var{name} must
29521 be a root variable object. Here, ``changed'' means that the result of
29522 @code{-var-evaluate-expression} before and after the
29523 @code{-var-update} is different. If @samp{*} is used as the variable
29524 object names, all existing variable objects are updated, except
29525 for frozen ones (@pxref{-var-set-frozen}). The option
29526 @var{print-values} determines whether both names and values, or just
29527 names are printed. The possible values of this option are the same
29528 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29529 recommended to use the @samp{--all-values} option, to reduce the
29530 number of MI commands needed on each program stop.
29532 With the @samp{*} parameter, if a variable object is bound to a
29533 currently running thread, it will not be updated, without any
29536 If @code{-var-set-update-range} was previously used on a varobj, then
29537 only the selected range of children will be reported.
29539 @code{-var-update} reports all the changed varobjs in a tuple named
29542 Each item in the change list is itself a tuple holding:
29546 The name of the varobj.
29549 If values were requested for this update, then this field will be
29550 present and will hold the value of the varobj.
29553 @anchor{-var-update}
29554 This field is a string which may take one of three values:
29558 The variable object's current value is valid.
29561 The variable object does not currently hold a valid value but it may
29562 hold one in the future if its associated expression comes back into
29566 The variable object no longer holds a valid value.
29567 This can occur when the executable file being debugged has changed,
29568 either through recompilation or by using the @value{GDBN} @code{file}
29569 command. The front end should normally choose to delete these variable
29573 In the future new values may be added to this list so the front should
29574 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29577 This is only present if the varobj is still valid. If the type
29578 changed, then this will be the string @samp{true}; otherwise it will
29581 When a varobj's type changes, its children are also likely to have
29582 become incorrect. Therefore, the varobj's children are automatically
29583 deleted when this attribute is @samp{true}. Also, the varobj's update
29584 range, when set using the @code{-var-set-update-range} command, is
29588 If the varobj's type changed, then this field will be present and will
29591 @item new_num_children
29592 For a dynamic varobj, if the number of children changed, or if the
29593 type changed, this will be the new number of children.
29595 The @samp{numchild} field in other varobj responses is generally not
29596 valid for a dynamic varobj -- it will show the number of children that
29597 @value{GDBN} knows about, but because dynamic varobjs lazily
29598 instantiate their children, this will not reflect the number of
29599 children which may be available.
29601 The @samp{new_num_children} attribute only reports changes to the
29602 number of children known by @value{GDBN}. This is the only way to
29603 detect whether an update has removed children (which necessarily can
29604 only happen at the end of the update range).
29607 The display hint, if any.
29610 This is an integer value, which will be 1 if there are more children
29611 available outside the varobj's update range.
29614 This attribute will be present and have the value @samp{1} if the
29615 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29616 then this attribute will not be present.
29619 If new children were added to a dynamic varobj within the selected
29620 update range (as set by @code{-var-set-update-range}), then they will
29621 be listed in this attribute.
29624 @subsubheading Example
29631 -var-update --all-values var1
29632 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29633 type_changed="false"@}]
29637 @subheading The @code{-var-set-frozen} Command
29638 @findex -var-set-frozen
29639 @anchor{-var-set-frozen}
29641 @subsubheading Synopsis
29644 -var-set-frozen @var{name} @var{flag}
29647 Set the frozenness flag on the variable object @var{name}. The
29648 @var{flag} parameter should be either @samp{1} to make the variable
29649 frozen or @samp{0} to make it unfrozen. If a variable object is
29650 frozen, then neither itself, nor any of its children, are
29651 implicitly updated by @code{-var-update} of
29652 a parent variable or by @code{-var-update *}. Only
29653 @code{-var-update} of the variable itself will update its value and
29654 values of its children. After a variable object is unfrozen, it is
29655 implicitly updated by all subsequent @code{-var-update} operations.
29656 Unfreezing a variable does not update it, only subsequent
29657 @code{-var-update} does.
29659 @subsubheading Example
29663 -var-set-frozen V 1
29668 @subheading The @code{-var-set-update-range} command
29669 @findex -var-set-update-range
29670 @anchor{-var-set-update-range}
29672 @subsubheading Synopsis
29675 -var-set-update-range @var{name} @var{from} @var{to}
29678 Set the range of children to be returned by future invocations of
29679 @code{-var-update}.
29681 @var{from} and @var{to} indicate the range of children to report. If
29682 @var{from} or @var{to} is less than zero, the range is reset and all
29683 children will be reported. Otherwise, children starting at @var{from}
29684 (zero-based) and up to and excluding @var{to} will be reported.
29686 @subsubheading Example
29690 -var-set-update-range V 1 2
29694 @subheading The @code{-var-set-visualizer} command
29695 @findex -var-set-visualizer
29696 @anchor{-var-set-visualizer}
29698 @subsubheading Synopsis
29701 -var-set-visualizer @var{name} @var{visualizer}
29704 Set a visualizer for the variable object @var{name}.
29706 @var{visualizer} is the visualizer to use. The special value
29707 @samp{None} means to disable any visualizer in use.
29709 If not @samp{None}, @var{visualizer} must be a Python expression.
29710 This expression must evaluate to a callable object which accepts a
29711 single argument. @value{GDBN} will call this object with the value of
29712 the varobj @var{name} as an argument (this is done so that the same
29713 Python pretty-printing code can be used for both the CLI and MI).
29714 When called, this object must return an object which conforms to the
29715 pretty-printing interface (@pxref{Pretty Printing API}).
29717 The pre-defined function @code{gdb.default_visualizer} may be used to
29718 select a visualizer by following the built-in process
29719 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29720 a varobj is created, and so ordinarily is not needed.
29722 This feature is only available if Python support is enabled. The MI
29723 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29724 can be used to check this.
29726 @subsubheading Example
29728 Resetting the visualizer:
29732 -var-set-visualizer V None
29736 Reselecting the default (type-based) visualizer:
29740 -var-set-visualizer V gdb.default_visualizer
29744 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29745 can be used to instantiate this class for a varobj:
29749 -var-set-visualizer V "lambda val: SomeClass()"
29753 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29754 @node GDB/MI Data Manipulation
29755 @section @sc{gdb/mi} Data Manipulation
29757 @cindex data manipulation, in @sc{gdb/mi}
29758 @cindex @sc{gdb/mi}, data manipulation
29759 This section describes the @sc{gdb/mi} commands that manipulate data:
29760 examine memory and registers, evaluate expressions, etc.
29762 For details about what an addressable memory unit is,
29763 @pxref{addressable memory unit}.
29765 @c REMOVED FROM THE INTERFACE.
29766 @c @subheading -data-assign
29767 @c Change the value of a program variable. Plenty of side effects.
29768 @c @subsubheading GDB Command
29770 @c @subsubheading Example
29773 @subheading The @code{-data-disassemble} Command
29774 @findex -data-disassemble
29776 @subsubheading Synopsis
29780 [ -s @var{start-addr} -e @var{end-addr} ]
29781 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29789 @item @var{start-addr}
29790 is the beginning address (or @code{$pc})
29791 @item @var{end-addr}
29793 @item @var{filename}
29794 is the name of the file to disassemble
29795 @item @var{linenum}
29796 is the line number to disassemble around
29798 is the number of disassembly lines to be produced. If it is -1,
29799 the whole function will be disassembled, in case no @var{end-addr} is
29800 specified. If @var{end-addr} is specified as a non-zero value, and
29801 @var{lines} is lower than the number of disassembly lines between
29802 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29803 displayed; if @var{lines} is higher than the number of lines between
29804 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29809 @item 0 disassembly only
29810 @item 1 mixed source and disassembly (deprecated)
29811 @item 2 disassembly with raw opcodes
29812 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29813 @item 4 mixed source and disassembly
29814 @item 5 mixed source and disassembly with raw opcodes
29817 Modes 1 and 3 are deprecated. The output is ``source centric''
29818 which hasn't proved useful in practice.
29819 @xref{Machine Code}, for a discussion of the difference between
29820 @code{/m} and @code{/s} output of the @code{disassemble} command.
29823 @subsubheading Result
29825 The result of the @code{-data-disassemble} command will be a list named
29826 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29827 used with the @code{-data-disassemble} command.
29829 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29834 The address at which this instruction was disassembled.
29837 The name of the function this instruction is within.
29840 The decimal offset in bytes from the start of @samp{func-name}.
29843 The text disassembly for this @samp{address}.
29846 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29847 bytes for the @samp{inst} field.
29851 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29852 @samp{src_and_asm_line}, each of which has the following fields:
29856 The line number within @samp{file}.
29859 The file name from the compilation unit. This might be an absolute
29860 file name or a relative file name depending on the compile command
29864 Absolute file name of @samp{file}. It is converted to a canonical form
29865 using the source file search path
29866 (@pxref{Source Path, ,Specifying Source Directories})
29867 and after resolving all the symbolic links.
29869 If the source file is not found this field will contain the path as
29870 present in the debug information.
29872 @item line_asm_insn
29873 This is a list of tuples containing the disassembly for @samp{line} in
29874 @samp{file}. The fields of each tuple are the same as for
29875 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29876 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29881 Note that whatever included in the @samp{inst} field, is not
29882 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29885 @subsubheading @value{GDBN} Command
29887 The corresponding @value{GDBN} command is @samp{disassemble}.
29889 @subsubheading Example
29891 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29895 -data-disassemble -s $pc -e "$pc + 20" -- 0
29898 @{address="0x000107c0",func-name="main",offset="4",
29899 inst="mov 2, %o0"@},
29900 @{address="0x000107c4",func-name="main",offset="8",
29901 inst="sethi %hi(0x11800), %o2"@},
29902 @{address="0x000107c8",func-name="main",offset="12",
29903 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29904 @{address="0x000107cc",func-name="main",offset="16",
29905 inst="sethi %hi(0x11800), %o2"@},
29906 @{address="0x000107d0",func-name="main",offset="20",
29907 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29911 Disassemble the whole @code{main} function. Line 32 is part of
29915 -data-disassemble -f basics.c -l 32 -- 0
29917 @{address="0x000107bc",func-name="main",offset="0",
29918 inst="save %sp, -112, %sp"@},
29919 @{address="0x000107c0",func-name="main",offset="4",
29920 inst="mov 2, %o0"@},
29921 @{address="0x000107c4",func-name="main",offset="8",
29922 inst="sethi %hi(0x11800), %o2"@},
29924 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29925 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29929 Disassemble 3 instructions from the start of @code{main}:
29933 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29935 @{address="0x000107bc",func-name="main",offset="0",
29936 inst="save %sp, -112, %sp"@},
29937 @{address="0x000107c0",func-name="main",offset="4",
29938 inst="mov 2, %o0"@},
29939 @{address="0x000107c4",func-name="main",offset="8",
29940 inst="sethi %hi(0x11800), %o2"@}]
29944 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29948 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29950 src_and_asm_line=@{line="31",
29951 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29952 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29953 line_asm_insn=[@{address="0x000107bc",
29954 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29955 src_and_asm_line=@{line="32",
29956 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29957 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29958 line_asm_insn=[@{address="0x000107c0",
29959 func-name="main",offset="4",inst="mov 2, %o0"@},
29960 @{address="0x000107c4",func-name="main",offset="8",
29961 inst="sethi %hi(0x11800), %o2"@}]@}]
29966 @subheading The @code{-data-evaluate-expression} Command
29967 @findex -data-evaluate-expression
29969 @subsubheading Synopsis
29972 -data-evaluate-expression @var{expr}
29975 Evaluate @var{expr} as an expression. The expression could contain an
29976 inferior function call. The function call will execute synchronously.
29977 If the expression contains spaces, it must be enclosed in double quotes.
29979 @subsubheading @value{GDBN} Command
29981 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29982 @samp{call}. In @code{gdbtk} only, there's a corresponding
29983 @samp{gdb_eval} command.
29985 @subsubheading Example
29987 In the following example, the numbers that precede the commands are the
29988 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29989 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29993 211-data-evaluate-expression A
29996 311-data-evaluate-expression &A
29997 311^done,value="0xefffeb7c"
29999 411-data-evaluate-expression A+3
30002 511-data-evaluate-expression "A + 3"
30008 @subheading The @code{-data-list-changed-registers} Command
30009 @findex -data-list-changed-registers
30011 @subsubheading Synopsis
30014 -data-list-changed-registers
30017 Display a list of the registers that have changed.
30019 @subsubheading @value{GDBN} Command
30021 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30022 has the corresponding command @samp{gdb_changed_register_list}.
30024 @subsubheading Example
30026 On a PPC MBX board:
30034 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30035 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30038 -data-list-changed-registers
30039 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30040 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30041 "24","25","26","27","28","30","31","64","65","66","67","69"]
30046 @subheading The @code{-data-list-register-names} Command
30047 @findex -data-list-register-names
30049 @subsubheading Synopsis
30052 -data-list-register-names [ ( @var{regno} )+ ]
30055 Show a list of register names for the current target. If no arguments
30056 are given, it shows a list of the names of all the registers. If
30057 integer numbers are given as arguments, it will print a list of the
30058 names of the registers corresponding to the arguments. To ensure
30059 consistency between a register name and its number, the output list may
30060 include empty register names.
30062 @subsubheading @value{GDBN} Command
30064 @value{GDBN} does not have a command which corresponds to
30065 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30066 corresponding command @samp{gdb_regnames}.
30068 @subsubheading Example
30070 For the PPC MBX board:
30073 -data-list-register-names
30074 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30075 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30076 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30077 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30078 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30079 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30080 "", "pc","ps","cr","lr","ctr","xer"]
30082 -data-list-register-names 1 2 3
30083 ^done,register-names=["r1","r2","r3"]
30087 @subheading The @code{-data-list-register-values} Command
30088 @findex -data-list-register-values
30090 @subsubheading Synopsis
30093 -data-list-register-values
30094 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30097 Display the registers' contents. The format according to which the
30098 registers' contents are to be returned is given by @var{fmt}, followed
30099 by an optional list of numbers specifying the registers to display. A
30100 missing list of numbers indicates that the contents of all the
30101 registers must be returned. The @code{--skip-unavailable} option
30102 indicates that only the available registers are to be returned.
30104 Allowed formats for @var{fmt} are:
30121 @subsubheading @value{GDBN} Command
30123 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30124 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30126 @subsubheading Example
30128 For a PPC MBX board (note: line breaks are for readability only, they
30129 don't appear in the actual output):
30133 -data-list-register-values r 64 65
30134 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30135 @{number="65",value="0x00029002"@}]
30137 -data-list-register-values x
30138 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30139 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30140 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30141 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30142 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30143 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30144 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30145 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30146 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30147 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30148 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30149 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30150 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30151 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30152 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30153 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30154 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30155 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30156 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30157 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30158 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30159 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30160 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30161 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30162 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30163 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30164 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30165 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30166 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30167 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30168 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30169 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30170 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30171 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30172 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30173 @{number="69",value="0x20002b03"@}]
30178 @subheading The @code{-data-read-memory} Command
30179 @findex -data-read-memory
30181 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30183 @subsubheading Synopsis
30186 -data-read-memory [ -o @var{byte-offset} ]
30187 @var{address} @var{word-format} @var{word-size}
30188 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30195 @item @var{address}
30196 An expression specifying the address of the first memory word to be
30197 read. Complex expressions containing embedded white space should be
30198 quoted using the C convention.
30200 @item @var{word-format}
30201 The format to be used to print the memory words. The notation is the
30202 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30205 @item @var{word-size}
30206 The size of each memory word in bytes.
30208 @item @var{nr-rows}
30209 The number of rows in the output table.
30211 @item @var{nr-cols}
30212 The number of columns in the output table.
30215 If present, indicates that each row should include an @sc{ascii} dump. The
30216 value of @var{aschar} is used as a padding character when a byte is not a
30217 member of the printable @sc{ascii} character set (printable @sc{ascii}
30218 characters are those whose code is between 32 and 126, inclusively).
30220 @item @var{byte-offset}
30221 An offset to add to the @var{address} before fetching memory.
30224 This command displays memory contents as a table of @var{nr-rows} by
30225 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30226 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30227 (returned as @samp{total-bytes}). Should less than the requested number
30228 of bytes be returned by the target, the missing words are identified
30229 using @samp{N/A}. The number of bytes read from the target is returned
30230 in @samp{nr-bytes} and the starting address used to read memory in
30233 The address of the next/previous row or page is available in
30234 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30237 @subsubheading @value{GDBN} Command
30239 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30240 @samp{gdb_get_mem} memory read command.
30242 @subsubheading Example
30244 Read six bytes of memory starting at @code{bytes+6} but then offset by
30245 @code{-6} bytes. Format as three rows of two columns. One byte per
30246 word. Display each word in hex.
30250 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30251 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30252 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30253 prev-page="0x0000138a",memory=[
30254 @{addr="0x00001390",data=["0x00","0x01"]@},
30255 @{addr="0x00001392",data=["0x02","0x03"]@},
30256 @{addr="0x00001394",data=["0x04","0x05"]@}]
30260 Read two bytes of memory starting at address @code{shorts + 64} and
30261 display as a single word formatted in decimal.
30265 5-data-read-memory shorts+64 d 2 1 1
30266 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30267 next-row="0x00001512",prev-row="0x0000150e",
30268 next-page="0x00001512",prev-page="0x0000150e",memory=[
30269 @{addr="0x00001510",data=["128"]@}]
30273 Read thirty two bytes of memory starting at @code{bytes+16} and format
30274 as eight rows of four columns. Include a string encoding with @samp{x}
30275 used as the non-printable character.
30279 4-data-read-memory bytes+16 x 1 8 4 x
30280 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30281 next-row="0x000013c0",prev-row="0x0000139c",
30282 next-page="0x000013c0",prev-page="0x00001380",memory=[
30283 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30284 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30285 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30286 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30287 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30288 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30289 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30290 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30294 @subheading The @code{-data-read-memory-bytes} Command
30295 @findex -data-read-memory-bytes
30297 @subsubheading Synopsis
30300 -data-read-memory-bytes [ -o @var{offset} ]
30301 @var{address} @var{count}
30308 @item @var{address}
30309 An expression specifying the address of the first addressable memory unit
30310 to be read. Complex expressions containing embedded white space should be
30311 quoted using the C convention.
30314 The number of addressable memory units to read. This should be an integer
30318 The offset relative to @var{address} at which to start reading. This
30319 should be an integer literal. This option is provided so that a frontend
30320 is not required to first evaluate address and then perform address
30321 arithmetics itself.
30325 This command attempts to read all accessible memory regions in the
30326 specified range. First, all regions marked as unreadable in the memory
30327 map (if one is defined) will be skipped. @xref{Memory Region
30328 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30329 regions. For each one, if reading full region results in an errors,
30330 @value{GDBN} will try to read a subset of the region.
30332 In general, every single memory unit in the region may be readable or not,
30333 and the only way to read every readable unit is to try a read at
30334 every address, which is not practical. Therefore, @value{GDBN} will
30335 attempt to read all accessible memory units at either beginning or the end
30336 of the region, using a binary division scheme. This heuristic works
30337 well for reading accross a memory map boundary. Note that if a region
30338 has a readable range that is neither at the beginning or the end,
30339 @value{GDBN} will not read it.
30341 The result record (@pxref{GDB/MI Result Records}) that is output of
30342 the command includes a field named @samp{memory} whose content is a
30343 list of tuples. Each tuple represent a successfully read memory block
30344 and has the following fields:
30348 The start address of the memory block, as hexadecimal literal.
30351 The end address of the memory block, as hexadecimal literal.
30354 The offset of the memory block, as hexadecimal literal, relative to
30355 the start address passed to @code{-data-read-memory-bytes}.
30358 The contents of the memory block, in hex.
30364 @subsubheading @value{GDBN} Command
30366 The corresponding @value{GDBN} command is @samp{x}.
30368 @subsubheading Example
30372 -data-read-memory-bytes &a 10
30373 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30375 contents="01000000020000000300"@}]
30380 @subheading The @code{-data-write-memory-bytes} Command
30381 @findex -data-write-memory-bytes
30383 @subsubheading Synopsis
30386 -data-write-memory-bytes @var{address} @var{contents}
30387 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30394 @item @var{address}
30395 An expression specifying the address of the first addressable memory unit
30396 to be written. Complex expressions containing embedded white space should
30397 be quoted using the C convention.
30399 @item @var{contents}
30400 The hex-encoded data to write. It is an error if @var{contents} does
30401 not represent an integral number of addressable memory units.
30404 Optional argument indicating the number of addressable memory units to be
30405 written. If @var{count} is greater than @var{contents}' length,
30406 @value{GDBN} will repeatedly write @var{contents} until it fills
30407 @var{count} memory units.
30411 @subsubheading @value{GDBN} Command
30413 There's no corresponding @value{GDBN} command.
30415 @subsubheading Example
30419 -data-write-memory-bytes &a "aabbccdd"
30426 -data-write-memory-bytes &a "aabbccdd" 16e
30431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30432 @node GDB/MI Tracepoint Commands
30433 @section @sc{gdb/mi} Tracepoint Commands
30435 The commands defined in this section implement MI support for
30436 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30438 @subheading The @code{-trace-find} Command
30439 @findex -trace-find
30441 @subsubheading Synopsis
30444 -trace-find @var{mode} [@var{parameters}@dots{}]
30447 Find a trace frame using criteria defined by @var{mode} and
30448 @var{parameters}. The following table lists permissible
30449 modes and their parameters. For details of operation, see @ref{tfind}.
30454 No parameters are required. Stops examining trace frames.
30457 An integer is required as parameter. Selects tracepoint frame with
30460 @item tracepoint-number
30461 An integer is required as parameter. Finds next
30462 trace frame that corresponds to tracepoint with the specified number.
30465 An address is required as parameter. Finds
30466 next trace frame that corresponds to any tracepoint at the specified
30469 @item pc-inside-range
30470 Two addresses are required as parameters. Finds next trace
30471 frame that corresponds to a tracepoint at an address inside the
30472 specified range. Both bounds are considered to be inside the range.
30474 @item pc-outside-range
30475 Two addresses are required as parameters. Finds
30476 next trace frame that corresponds to a tracepoint at an address outside
30477 the specified range. Both bounds are considered to be inside the range.
30480 Line specification is required as parameter. @xref{Specify Location}.
30481 Finds next trace frame that corresponds to a tracepoint at
30482 the specified location.
30486 If @samp{none} was passed as @var{mode}, the response does not
30487 have fields. Otherwise, the response may have the following fields:
30491 This field has either @samp{0} or @samp{1} as the value, depending
30492 on whether a matching tracepoint was found.
30495 The index of the found traceframe. This field is present iff
30496 the @samp{found} field has value of @samp{1}.
30499 The index of the found tracepoint. This field is present iff
30500 the @samp{found} field has value of @samp{1}.
30503 The information about the frame corresponding to the found trace
30504 frame. This field is present only if a trace frame was found.
30505 @xref{GDB/MI Frame Information}, for description of this field.
30509 @subsubheading @value{GDBN} Command
30511 The corresponding @value{GDBN} command is @samp{tfind}.
30513 @subheading -trace-define-variable
30514 @findex -trace-define-variable
30516 @subsubheading Synopsis
30519 -trace-define-variable @var{name} [ @var{value} ]
30522 Create trace variable @var{name} if it does not exist. If
30523 @var{value} is specified, sets the initial value of the specified
30524 trace variable to that value. Note that the @var{name} should start
30525 with the @samp{$} character.
30527 @subsubheading @value{GDBN} Command
30529 The corresponding @value{GDBN} command is @samp{tvariable}.
30531 @subheading The @code{-trace-frame-collected} Command
30532 @findex -trace-frame-collected
30534 @subsubheading Synopsis
30537 -trace-frame-collected
30538 [--var-print-values @var{var_pval}]
30539 [--comp-print-values @var{comp_pval}]
30540 [--registers-format @var{regformat}]
30541 [--memory-contents]
30544 This command returns the set of collected objects, register names,
30545 trace state variable names, memory ranges and computed expressions
30546 that have been collected at a particular trace frame. The optional
30547 parameters to the command affect the output format in different ways.
30548 See the output description table below for more details.
30550 The reported names can be used in the normal manner to create
30551 varobjs and inspect the objects themselves. The items returned by
30552 this command are categorized so that it is clear which is a variable,
30553 which is a register, which is a trace state variable, which is a
30554 memory range and which is a computed expression.
30556 For instance, if the actions were
30558 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30559 collect *(int*)0xaf02bef0@@40
30563 the object collected in its entirety would be @code{myVar}. The
30564 object @code{myArray} would be partially collected, because only the
30565 element at index @code{myIndex} would be collected. The remaining
30566 objects would be computed expressions.
30568 An example output would be:
30572 -trace-frame-collected
30574 explicit-variables=[@{name="myVar",value="1"@}],
30575 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30576 @{name="myObj.field",value="0"@},
30577 @{name="myPtr->field",value="1"@},
30578 @{name="myCount + 2",value="3"@},
30579 @{name="$tvar1 + 1",value="43970027"@}],
30580 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30581 @{number="1",value="0x0"@},
30582 @{number="2",value="0x4"@},
30584 @{number="125",value="0x0"@}],
30585 tvars=[@{name="$tvar1",current="43970026"@}],
30586 memory=[@{address="0x0000000000602264",length="4"@},
30587 @{address="0x0000000000615bc0",length="4"@}]
30594 @item explicit-variables
30595 The set of objects that have been collected in their entirety (as
30596 opposed to collecting just a few elements of an array or a few struct
30597 members). For each object, its name and value are printed.
30598 The @code{--var-print-values} option affects how or whether the value
30599 field is output. If @var{var_pval} is 0, then print only the names;
30600 if it is 1, print also their values; and if it is 2, print the name,
30601 type and value for simple data types, and the name and type for
30602 arrays, structures and unions.
30604 @item computed-expressions
30605 The set of computed expressions that have been collected at the
30606 current trace frame. The @code{--comp-print-values} option affects
30607 this set like the @code{--var-print-values} option affects the
30608 @code{explicit-variables} set. See above.
30611 The registers that have been collected at the current trace frame.
30612 For each register collected, the name and current value are returned.
30613 The value is formatted according to the @code{--registers-format}
30614 option. See the @command{-data-list-register-values} command for a
30615 list of the allowed formats. The default is @samp{x}.
30618 The trace state variables that have been collected at the current
30619 trace frame. For each trace state variable collected, the name and
30620 current value are returned.
30623 The set of memory ranges that have been collected at the current trace
30624 frame. Its content is a list of tuples. Each tuple represents a
30625 collected memory range and has the following fields:
30629 The start address of the memory range, as hexadecimal literal.
30632 The length of the memory range, as decimal literal.
30635 The contents of the memory block, in hex. This field is only present
30636 if the @code{--memory-contents} option is specified.
30642 @subsubheading @value{GDBN} Command
30644 There is no corresponding @value{GDBN} command.
30646 @subsubheading Example
30648 @subheading -trace-list-variables
30649 @findex -trace-list-variables
30651 @subsubheading Synopsis
30654 -trace-list-variables
30657 Return a table of all defined trace variables. Each element of the
30658 table has the following fields:
30662 The name of the trace variable. This field is always present.
30665 The initial value. This is a 64-bit signed integer. This
30666 field is always present.
30669 The value the trace variable has at the moment. This is a 64-bit
30670 signed integer. This field is absent iff current value is
30671 not defined, for example if the trace was never run, or is
30676 @subsubheading @value{GDBN} Command
30678 The corresponding @value{GDBN} command is @samp{tvariables}.
30680 @subsubheading Example
30684 -trace-list-variables
30685 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30686 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30687 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30688 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30689 body=[variable=@{name="$trace_timestamp",initial="0"@}
30690 variable=@{name="$foo",initial="10",current="15"@}]@}
30694 @subheading -trace-save
30695 @findex -trace-save
30697 @subsubheading Synopsis
30700 -trace-save [-r ] @var{filename}
30703 Saves the collected trace data to @var{filename}. Without the
30704 @samp{-r} option, the data is downloaded from the target and saved
30705 in a local file. With the @samp{-r} option the target is asked
30706 to perform the save.
30708 @subsubheading @value{GDBN} Command
30710 The corresponding @value{GDBN} command is @samp{tsave}.
30713 @subheading -trace-start
30714 @findex -trace-start
30716 @subsubheading Synopsis
30722 Starts a tracing experiments. The result of this command does not
30725 @subsubheading @value{GDBN} Command
30727 The corresponding @value{GDBN} command is @samp{tstart}.
30729 @subheading -trace-status
30730 @findex -trace-status
30732 @subsubheading Synopsis
30738 Obtains the status of a tracing experiment. The result may include
30739 the following fields:
30744 May have a value of either @samp{0}, when no tracing operations are
30745 supported, @samp{1}, when all tracing operations are supported, or
30746 @samp{file} when examining trace file. In the latter case, examining
30747 of trace frame is possible but new tracing experiement cannot be
30748 started. This field is always present.
30751 May have a value of either @samp{0} or @samp{1} depending on whether
30752 tracing experiement is in progress on target. This field is present
30753 if @samp{supported} field is not @samp{0}.
30756 Report the reason why the tracing was stopped last time. This field
30757 may be absent iff tracing was never stopped on target yet. The
30758 value of @samp{request} means the tracing was stopped as result of
30759 the @code{-trace-stop} command. The value of @samp{overflow} means
30760 the tracing buffer is full. The value of @samp{disconnection} means
30761 tracing was automatically stopped when @value{GDBN} has disconnected.
30762 The value of @samp{passcount} means tracing was stopped when a
30763 tracepoint was passed a maximal number of times for that tracepoint.
30764 This field is present if @samp{supported} field is not @samp{0}.
30766 @item stopping-tracepoint
30767 The number of tracepoint whose passcount as exceeded. This field is
30768 present iff the @samp{stop-reason} field has the value of
30772 @itemx frames-created
30773 The @samp{frames} field is a count of the total number of trace frames
30774 in the trace buffer, while @samp{frames-created} is the total created
30775 during the run, including ones that were discarded, such as when a
30776 circular trace buffer filled up. Both fields are optional.
30780 These fields tell the current size of the tracing buffer and the
30781 remaining space. These fields are optional.
30784 The value of the circular trace buffer flag. @code{1} means that the
30785 trace buffer is circular and old trace frames will be discarded if
30786 necessary to make room, @code{0} means that the trace buffer is linear
30790 The value of the disconnected tracing flag. @code{1} means that
30791 tracing will continue after @value{GDBN} disconnects, @code{0} means
30792 that the trace run will stop.
30795 The filename of the trace file being examined. This field is
30796 optional, and only present when examining a trace file.
30800 @subsubheading @value{GDBN} Command
30802 The corresponding @value{GDBN} command is @samp{tstatus}.
30804 @subheading -trace-stop
30805 @findex -trace-stop
30807 @subsubheading Synopsis
30813 Stops a tracing experiment. The result of this command has the same
30814 fields as @code{-trace-status}, except that the @samp{supported} and
30815 @samp{running} fields are not output.
30817 @subsubheading @value{GDBN} Command
30819 The corresponding @value{GDBN} command is @samp{tstop}.
30822 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30823 @node GDB/MI Symbol Query
30824 @section @sc{gdb/mi} Symbol Query Commands
30828 @subheading The @code{-symbol-info-address} Command
30829 @findex -symbol-info-address
30831 @subsubheading Synopsis
30834 -symbol-info-address @var{symbol}
30837 Describe where @var{symbol} is stored.
30839 @subsubheading @value{GDBN} Command
30841 The corresponding @value{GDBN} command is @samp{info address}.
30843 @subsubheading Example
30847 @subheading The @code{-symbol-info-file} Command
30848 @findex -symbol-info-file
30850 @subsubheading Synopsis
30856 Show the file for the symbol.
30858 @subsubheading @value{GDBN} Command
30860 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30861 @samp{gdb_find_file}.
30863 @subsubheading Example
30867 @subheading The @code{-symbol-info-function} Command
30868 @findex -symbol-info-function
30870 @subsubheading Synopsis
30873 -symbol-info-function
30876 Show which function the symbol lives in.
30878 @subsubheading @value{GDBN} Command
30880 @samp{gdb_get_function} in @code{gdbtk}.
30882 @subsubheading Example
30886 @subheading The @code{-symbol-info-line} Command
30887 @findex -symbol-info-line
30889 @subsubheading Synopsis
30895 Show the core addresses of the code for a source line.
30897 @subsubheading @value{GDBN} Command
30899 The corresponding @value{GDBN} command is @samp{info line}.
30900 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30902 @subsubheading Example
30906 @subheading The @code{-symbol-info-symbol} Command
30907 @findex -symbol-info-symbol
30909 @subsubheading Synopsis
30912 -symbol-info-symbol @var{addr}
30915 Describe what symbol is at location @var{addr}.
30917 @subsubheading @value{GDBN} Command
30919 The corresponding @value{GDBN} command is @samp{info symbol}.
30921 @subsubheading Example
30925 @subheading The @code{-symbol-list-functions} Command
30926 @findex -symbol-list-functions
30928 @subsubheading Synopsis
30931 -symbol-list-functions
30934 List the functions in the executable.
30936 @subsubheading @value{GDBN} Command
30938 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30939 @samp{gdb_search} in @code{gdbtk}.
30941 @subsubheading Example
30946 @subheading The @code{-symbol-list-lines} Command
30947 @findex -symbol-list-lines
30949 @subsubheading Synopsis
30952 -symbol-list-lines @var{filename}
30955 Print the list of lines that contain code and their associated program
30956 addresses for the given source filename. The entries are sorted in
30957 ascending PC order.
30959 @subsubheading @value{GDBN} Command
30961 There is no corresponding @value{GDBN} command.
30963 @subsubheading Example
30966 -symbol-list-lines basics.c
30967 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30973 @subheading The @code{-symbol-list-types} Command
30974 @findex -symbol-list-types
30976 @subsubheading Synopsis
30982 List all the type names.
30984 @subsubheading @value{GDBN} Command
30986 The corresponding commands are @samp{info types} in @value{GDBN},
30987 @samp{gdb_search} in @code{gdbtk}.
30989 @subsubheading Example
30993 @subheading The @code{-symbol-list-variables} Command
30994 @findex -symbol-list-variables
30996 @subsubheading Synopsis
30999 -symbol-list-variables
31002 List all the global and static variable names.
31004 @subsubheading @value{GDBN} Command
31006 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31008 @subsubheading Example
31012 @subheading The @code{-symbol-locate} Command
31013 @findex -symbol-locate
31015 @subsubheading Synopsis
31021 @subsubheading @value{GDBN} Command
31023 @samp{gdb_loc} in @code{gdbtk}.
31025 @subsubheading Example
31029 @subheading The @code{-symbol-type} Command
31030 @findex -symbol-type
31032 @subsubheading Synopsis
31035 -symbol-type @var{variable}
31038 Show type of @var{variable}.
31040 @subsubheading @value{GDBN} Command
31042 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31043 @samp{gdb_obj_variable}.
31045 @subsubheading Example
31050 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31051 @node GDB/MI File Commands
31052 @section @sc{gdb/mi} File Commands
31054 This section describes the GDB/MI commands to specify executable file names
31055 and to read in and obtain symbol table information.
31057 @subheading The @code{-file-exec-and-symbols} Command
31058 @findex -file-exec-and-symbols
31060 @subsubheading Synopsis
31063 -file-exec-and-symbols @var{file}
31066 Specify the executable file to be debugged. This file is the one from
31067 which the symbol table is also read. If no file is specified, the
31068 command clears the executable and symbol information. If breakpoints
31069 are set when using this command with no arguments, @value{GDBN} will produce
31070 error messages. Otherwise, no output is produced, except a completion
31073 @subsubheading @value{GDBN} Command
31075 The corresponding @value{GDBN} command is @samp{file}.
31077 @subsubheading Example
31081 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31087 @subheading The @code{-file-exec-file} Command
31088 @findex -file-exec-file
31090 @subsubheading Synopsis
31093 -file-exec-file @var{file}
31096 Specify the executable file to be debugged. Unlike
31097 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31098 from this file. If used without argument, @value{GDBN} clears the information
31099 about the executable file. No output is produced, except a completion
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{exec-file}.
31106 @subsubheading Example
31110 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31117 @subheading The @code{-file-list-exec-sections} Command
31118 @findex -file-list-exec-sections
31120 @subsubheading Synopsis
31123 -file-list-exec-sections
31126 List the sections of the current executable file.
31128 @subsubheading @value{GDBN} Command
31130 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31131 information as this command. @code{gdbtk} has a corresponding command
31132 @samp{gdb_load_info}.
31134 @subsubheading Example
31139 @subheading The @code{-file-list-exec-source-file} Command
31140 @findex -file-list-exec-source-file
31142 @subsubheading Synopsis
31145 -file-list-exec-source-file
31148 List the line number, the current source file, and the absolute path
31149 to the current source file for the current executable. The macro
31150 information field has a value of @samp{1} or @samp{0} depending on
31151 whether or not the file includes preprocessor macro information.
31153 @subsubheading @value{GDBN} Command
31155 The @value{GDBN} equivalent is @samp{info source}
31157 @subsubheading Example
31161 123-file-list-exec-source-file
31162 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31167 @subheading The @code{-file-list-exec-source-files} Command
31168 @findex -file-list-exec-source-files
31170 @subsubheading Synopsis
31173 -file-list-exec-source-files
31176 List the source files for the current executable.
31178 It will always output both the filename and fullname (absolute file
31179 name) of a source file.
31181 @subsubheading @value{GDBN} Command
31183 The @value{GDBN} equivalent is @samp{info sources}.
31184 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31186 @subsubheading Example
31189 -file-list-exec-source-files
31191 @{file=foo.c,fullname=/home/foo.c@},
31192 @{file=/home/bar.c,fullname=/home/bar.c@},
31193 @{file=gdb_could_not_find_fullpath.c@}]
31198 @subheading The @code{-file-list-shared-libraries} Command
31199 @findex -file-list-shared-libraries
31201 @subsubheading Synopsis
31204 -file-list-shared-libraries
31207 List the shared libraries in the program.
31209 @subsubheading @value{GDBN} Command
31211 The corresponding @value{GDBN} command is @samp{info shared}.
31213 @subsubheading Example
31217 @subheading The @code{-file-list-symbol-files} Command
31218 @findex -file-list-symbol-files
31220 @subsubheading Synopsis
31223 -file-list-symbol-files
31228 @subsubheading @value{GDBN} Command
31230 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31232 @subsubheading Example
31237 @subheading The @code{-file-symbol-file} Command
31238 @findex -file-symbol-file
31240 @subsubheading Synopsis
31243 -file-symbol-file @var{file}
31246 Read symbol table info from the specified @var{file} argument. When
31247 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31248 produced, except for a completion notification.
31250 @subsubheading @value{GDBN} Command
31252 The corresponding @value{GDBN} command is @samp{symbol-file}.
31254 @subsubheading Example
31258 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31264 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31265 @node GDB/MI Memory Overlay Commands
31266 @section @sc{gdb/mi} Memory Overlay Commands
31268 The memory overlay commands are not implemented.
31270 @c @subheading -overlay-auto
31272 @c @subheading -overlay-list-mapping-state
31274 @c @subheading -overlay-list-overlays
31276 @c @subheading -overlay-map
31278 @c @subheading -overlay-off
31280 @c @subheading -overlay-on
31282 @c @subheading -overlay-unmap
31284 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31285 @node GDB/MI Signal Handling Commands
31286 @section @sc{gdb/mi} Signal Handling Commands
31288 Signal handling commands are not implemented.
31290 @c @subheading -signal-handle
31292 @c @subheading -signal-list-handle-actions
31294 @c @subheading -signal-list-signal-types
31298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31299 @node GDB/MI Target Manipulation
31300 @section @sc{gdb/mi} Target Manipulation Commands
31303 @subheading The @code{-target-attach} Command
31304 @findex -target-attach
31306 @subsubheading Synopsis
31309 -target-attach @var{pid} | @var{gid} | @var{file}
31312 Attach to a process @var{pid} or a file @var{file} outside of
31313 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31314 group, the id previously returned by
31315 @samp{-list-thread-groups --available} must be used.
31317 @subsubheading @value{GDBN} Command
31319 The corresponding @value{GDBN} command is @samp{attach}.
31321 @subsubheading Example
31325 =thread-created,id="1"
31326 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31332 @subheading The @code{-target-compare-sections} Command
31333 @findex -target-compare-sections
31335 @subsubheading Synopsis
31338 -target-compare-sections [ @var{section} ]
31341 Compare data of section @var{section} on target to the exec file.
31342 Without the argument, all sections are compared.
31344 @subsubheading @value{GDBN} Command
31346 The @value{GDBN} equivalent is @samp{compare-sections}.
31348 @subsubheading Example
31353 @subheading The @code{-target-detach} Command
31354 @findex -target-detach
31356 @subsubheading Synopsis
31359 -target-detach [ @var{pid} | @var{gid} ]
31362 Detach from the remote target which normally resumes its execution.
31363 If either @var{pid} or @var{gid} is specified, detaches from either
31364 the specified process, or specified thread group. There's no output.
31366 @subsubheading @value{GDBN} Command
31368 The corresponding @value{GDBN} command is @samp{detach}.
31370 @subsubheading Example
31380 @subheading The @code{-target-disconnect} Command
31381 @findex -target-disconnect
31383 @subsubheading Synopsis
31389 Disconnect from the remote target. There's no output and the target is
31390 generally not resumed.
31392 @subsubheading @value{GDBN} Command
31394 The corresponding @value{GDBN} command is @samp{disconnect}.
31396 @subsubheading Example
31406 @subheading The @code{-target-download} Command
31407 @findex -target-download
31409 @subsubheading Synopsis
31415 Loads the executable onto the remote target.
31416 It prints out an update message every half second, which includes the fields:
31420 The name of the section.
31422 The size of what has been sent so far for that section.
31424 The size of the section.
31426 The total size of what was sent so far (the current and the previous sections).
31428 The size of the overall executable to download.
31432 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31433 @sc{gdb/mi} Output Syntax}).
31435 In addition, it prints the name and size of the sections, as they are
31436 downloaded. These messages include the following fields:
31440 The name of the section.
31442 The size of the section.
31444 The size of the overall executable to download.
31448 At the end, a summary is printed.
31450 @subsubheading @value{GDBN} Command
31452 The corresponding @value{GDBN} command is @samp{load}.
31454 @subsubheading Example
31456 Note: each status message appears on a single line. Here the messages
31457 have been broken down so that they can fit onto a page.
31462 +download,@{section=".text",section-size="6668",total-size="9880"@}
31463 +download,@{section=".text",section-sent="512",section-size="6668",
31464 total-sent="512",total-size="9880"@}
31465 +download,@{section=".text",section-sent="1024",section-size="6668",
31466 total-sent="1024",total-size="9880"@}
31467 +download,@{section=".text",section-sent="1536",section-size="6668",
31468 total-sent="1536",total-size="9880"@}
31469 +download,@{section=".text",section-sent="2048",section-size="6668",
31470 total-sent="2048",total-size="9880"@}
31471 +download,@{section=".text",section-sent="2560",section-size="6668",
31472 total-sent="2560",total-size="9880"@}
31473 +download,@{section=".text",section-sent="3072",section-size="6668",
31474 total-sent="3072",total-size="9880"@}
31475 +download,@{section=".text",section-sent="3584",section-size="6668",
31476 total-sent="3584",total-size="9880"@}
31477 +download,@{section=".text",section-sent="4096",section-size="6668",
31478 total-sent="4096",total-size="9880"@}
31479 +download,@{section=".text",section-sent="4608",section-size="6668",
31480 total-sent="4608",total-size="9880"@}
31481 +download,@{section=".text",section-sent="5120",section-size="6668",
31482 total-sent="5120",total-size="9880"@}
31483 +download,@{section=".text",section-sent="5632",section-size="6668",
31484 total-sent="5632",total-size="9880"@}
31485 +download,@{section=".text",section-sent="6144",section-size="6668",
31486 total-sent="6144",total-size="9880"@}
31487 +download,@{section=".text",section-sent="6656",section-size="6668",
31488 total-sent="6656",total-size="9880"@}
31489 +download,@{section=".init",section-size="28",total-size="9880"@}
31490 +download,@{section=".fini",section-size="28",total-size="9880"@}
31491 +download,@{section=".data",section-size="3156",total-size="9880"@}
31492 +download,@{section=".data",section-sent="512",section-size="3156",
31493 total-sent="7236",total-size="9880"@}
31494 +download,@{section=".data",section-sent="1024",section-size="3156",
31495 total-sent="7748",total-size="9880"@}
31496 +download,@{section=".data",section-sent="1536",section-size="3156",
31497 total-sent="8260",total-size="9880"@}
31498 +download,@{section=".data",section-sent="2048",section-size="3156",
31499 total-sent="8772",total-size="9880"@}
31500 +download,@{section=".data",section-sent="2560",section-size="3156",
31501 total-sent="9284",total-size="9880"@}
31502 +download,@{section=".data",section-sent="3072",section-size="3156",
31503 total-sent="9796",total-size="9880"@}
31504 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31511 @subheading The @code{-target-exec-status} Command
31512 @findex -target-exec-status
31514 @subsubheading Synopsis
31517 -target-exec-status
31520 Provide information on the state of the target (whether it is running or
31521 not, for instance).
31523 @subsubheading @value{GDBN} Command
31525 There's no equivalent @value{GDBN} command.
31527 @subsubheading Example
31531 @subheading The @code{-target-list-available-targets} Command
31532 @findex -target-list-available-targets
31534 @subsubheading Synopsis
31537 -target-list-available-targets
31540 List the possible targets to connect to.
31542 @subsubheading @value{GDBN} Command
31544 The corresponding @value{GDBN} command is @samp{help target}.
31546 @subsubheading Example
31550 @subheading The @code{-target-list-current-targets} Command
31551 @findex -target-list-current-targets
31553 @subsubheading Synopsis
31556 -target-list-current-targets
31559 Describe the current target.
31561 @subsubheading @value{GDBN} Command
31563 The corresponding information is printed by @samp{info file} (among
31566 @subsubheading Example
31570 @subheading The @code{-target-list-parameters} Command
31571 @findex -target-list-parameters
31573 @subsubheading Synopsis
31576 -target-list-parameters
31582 @subsubheading @value{GDBN} Command
31586 @subsubheading Example
31590 @subheading The @code{-target-select} Command
31591 @findex -target-select
31593 @subsubheading Synopsis
31596 -target-select @var{type} @var{parameters @dots{}}
31599 Connect @value{GDBN} to the remote target. This command takes two args:
31603 The type of target, for instance @samp{remote}, etc.
31604 @item @var{parameters}
31605 Device names, host names and the like. @xref{Target Commands, ,
31606 Commands for Managing Targets}, for more details.
31609 The output is a connection notification, followed by the address at
31610 which the target program is, in the following form:
31613 ^connected,addr="@var{address}",func="@var{function name}",
31614 args=[@var{arg list}]
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{target}.
31621 @subsubheading Example
31625 -target-select remote /dev/ttya
31626 ^connected,addr="0xfe00a300",func="??",args=[]
31630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31631 @node GDB/MI File Transfer Commands
31632 @section @sc{gdb/mi} File Transfer Commands
31635 @subheading The @code{-target-file-put} Command
31636 @findex -target-file-put
31638 @subsubheading Synopsis
31641 -target-file-put @var{hostfile} @var{targetfile}
31644 Copy file @var{hostfile} from the host system (the machine running
31645 @value{GDBN}) to @var{targetfile} on the target system.
31647 @subsubheading @value{GDBN} Command
31649 The corresponding @value{GDBN} command is @samp{remote put}.
31651 @subsubheading Example
31655 -target-file-put localfile remotefile
31661 @subheading The @code{-target-file-get} Command
31662 @findex -target-file-get
31664 @subsubheading Synopsis
31667 -target-file-get @var{targetfile} @var{hostfile}
31670 Copy file @var{targetfile} from the target system to @var{hostfile}
31671 on the host system.
31673 @subsubheading @value{GDBN} Command
31675 The corresponding @value{GDBN} command is @samp{remote get}.
31677 @subsubheading Example
31681 -target-file-get remotefile localfile
31687 @subheading The @code{-target-file-delete} Command
31688 @findex -target-file-delete
31690 @subsubheading Synopsis
31693 -target-file-delete @var{targetfile}
31696 Delete @var{targetfile} from the target system.
31698 @subsubheading @value{GDBN} Command
31700 The corresponding @value{GDBN} command is @samp{remote delete}.
31702 @subsubheading Example
31706 -target-file-delete remotefile
31712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31713 @node GDB/MI Ada Exceptions Commands
31714 @section Ada Exceptions @sc{gdb/mi} Commands
31716 @subheading The @code{-info-ada-exceptions} Command
31717 @findex -info-ada-exceptions
31719 @subsubheading Synopsis
31722 -info-ada-exceptions [ @var{regexp}]
31725 List all Ada exceptions defined within the program being debugged.
31726 With a regular expression @var{regexp}, only those exceptions whose
31727 names match @var{regexp} are listed.
31729 @subsubheading @value{GDBN} Command
31731 The corresponding @value{GDBN} command is @samp{info exceptions}.
31733 @subsubheading Result
31735 The result is a table of Ada exceptions. The following columns are
31736 defined for each exception:
31740 The name of the exception.
31743 The address of the exception.
31747 @subsubheading Example
31750 -info-ada-exceptions aint
31751 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31752 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31753 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31754 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31755 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31758 @subheading Catching Ada Exceptions
31760 The commands describing how to ask @value{GDBN} to stop when a program
31761 raises an exception are described at @ref{Ada Exception GDB/MI
31762 Catchpoint Commands}.
31765 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31766 @node GDB/MI Support Commands
31767 @section @sc{gdb/mi} Support Commands
31769 Since new commands and features get regularly added to @sc{gdb/mi},
31770 some commands are available to help front-ends query the debugger
31771 about support for these capabilities. Similarly, it is also possible
31772 to query @value{GDBN} about target support of certain features.
31774 @subheading The @code{-info-gdb-mi-command} Command
31775 @cindex @code{-info-gdb-mi-command}
31776 @findex -info-gdb-mi-command
31778 @subsubheading Synopsis
31781 -info-gdb-mi-command @var{cmd_name}
31784 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31786 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31787 is technically not part of the command name (@pxref{GDB/MI Input
31788 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31789 for ease of use, this command also accepts the form with the leading
31792 @subsubheading @value{GDBN} Command
31794 There is no corresponding @value{GDBN} command.
31796 @subsubheading Result
31798 The result is a tuple. There is currently only one field:
31802 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31803 @code{"false"} otherwise.
31807 @subsubheading Example
31809 Here is an example where the @sc{gdb/mi} command does not exist:
31812 -info-gdb-mi-command unsupported-command
31813 ^done,command=@{exists="false"@}
31817 And here is an example where the @sc{gdb/mi} command is known
31821 -info-gdb-mi-command symbol-list-lines
31822 ^done,command=@{exists="true"@}
31825 @subheading The @code{-list-features} Command
31826 @findex -list-features
31827 @cindex supported @sc{gdb/mi} features, list
31829 Returns a list of particular features of the MI protocol that
31830 this version of gdb implements. A feature can be a command,
31831 or a new field in an output of some command, or even an
31832 important bugfix. While a frontend can sometimes detect presence
31833 of a feature at runtime, it is easier to perform detection at debugger
31836 The command returns a list of strings, with each string naming an
31837 available feature. Each returned string is just a name, it does not
31838 have any internal structure. The list of possible feature names
31844 (gdb) -list-features
31845 ^done,result=["feature1","feature2"]
31848 The current list of features is:
31851 @item frozen-varobjs
31852 Indicates support for the @code{-var-set-frozen} command, as well
31853 as possible presense of the @code{frozen} field in the output
31854 of @code{-varobj-create}.
31855 @item pending-breakpoints
31856 Indicates support for the @option{-f} option to the @code{-break-insert}
31859 Indicates Python scripting support, Python-based
31860 pretty-printing commands, and possible presence of the
31861 @samp{display_hint} field in the output of @code{-var-list-children}
31863 Indicates support for the @code{-thread-info} command.
31864 @item data-read-memory-bytes
31865 Indicates support for the @code{-data-read-memory-bytes} and the
31866 @code{-data-write-memory-bytes} commands.
31867 @item breakpoint-notifications
31868 Indicates that changes to breakpoints and breakpoints created via the
31869 CLI will be announced via async records.
31870 @item ada-task-info
31871 Indicates support for the @code{-ada-task-info} command.
31872 @item language-option
31873 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31874 option (@pxref{Context management}).
31875 @item info-gdb-mi-command
31876 Indicates support for the @code{-info-gdb-mi-command} command.
31877 @item undefined-command-error-code
31878 Indicates support for the "undefined-command" error code in error result
31879 records, produced when trying to execute an undefined @sc{gdb/mi} command
31880 (@pxref{GDB/MI Result Records}).
31881 @item exec-run-start-option
31882 Indicates that the @code{-exec-run} command supports the @option{--start}
31883 option (@pxref{GDB/MI Program Execution}).
31886 @subheading The @code{-list-target-features} Command
31887 @findex -list-target-features
31889 Returns a list of particular features that are supported by the
31890 target. Those features affect the permitted MI commands, but
31891 unlike the features reported by the @code{-list-features} command, the
31892 features depend on which target GDB is using at the moment. Whenever
31893 a target can change, due to commands such as @code{-target-select},
31894 @code{-target-attach} or @code{-exec-run}, the list of target features
31895 may change, and the frontend should obtain it again.
31899 (gdb) -list-target-features
31900 ^done,result=["async"]
31903 The current list of features is:
31907 Indicates that the target is capable of asynchronous command
31908 execution, which means that @value{GDBN} will accept further commands
31909 while the target is running.
31912 Indicates that the target is capable of reverse execution.
31913 @xref{Reverse Execution}, for more information.
31917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31918 @node GDB/MI Miscellaneous Commands
31919 @section Miscellaneous @sc{gdb/mi} Commands
31921 @c @subheading -gdb-complete
31923 @subheading The @code{-gdb-exit} Command
31926 @subsubheading Synopsis
31932 Exit @value{GDBN} immediately.
31934 @subsubheading @value{GDBN} Command
31936 Approximately corresponds to @samp{quit}.
31938 @subsubheading Example
31948 @subheading The @code{-exec-abort} Command
31949 @findex -exec-abort
31951 @subsubheading Synopsis
31957 Kill the inferior running program.
31959 @subsubheading @value{GDBN} Command
31961 The corresponding @value{GDBN} command is @samp{kill}.
31963 @subsubheading Example
31968 @subheading The @code{-gdb-set} Command
31971 @subsubheading Synopsis
31977 Set an internal @value{GDBN} variable.
31978 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31980 @subsubheading @value{GDBN} Command
31982 The corresponding @value{GDBN} command is @samp{set}.
31984 @subsubheading Example
31994 @subheading The @code{-gdb-show} Command
31997 @subsubheading Synopsis
32003 Show the current value of a @value{GDBN} variable.
32005 @subsubheading @value{GDBN} Command
32007 The corresponding @value{GDBN} command is @samp{show}.
32009 @subsubheading Example
32018 @c @subheading -gdb-source
32021 @subheading The @code{-gdb-version} Command
32022 @findex -gdb-version
32024 @subsubheading Synopsis
32030 Show version information for @value{GDBN}. Used mostly in testing.
32032 @subsubheading @value{GDBN} Command
32034 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32035 default shows this information when you start an interactive session.
32037 @subsubheading Example
32039 @c This example modifies the actual output from GDB to avoid overfull
32045 ~Copyright 2000 Free Software Foundation, Inc.
32046 ~GDB is free software, covered by the GNU General Public License, and
32047 ~you are welcome to change it and/or distribute copies of it under
32048 ~ certain conditions.
32049 ~Type "show copying" to see the conditions.
32050 ~There is absolutely no warranty for GDB. Type "show warranty" for
32052 ~This GDB was configured as
32053 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32058 @subheading The @code{-list-thread-groups} Command
32059 @findex -list-thread-groups
32061 @subheading Synopsis
32064 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32067 Lists thread groups (@pxref{Thread groups}). When a single thread
32068 group is passed as the argument, lists the children of that group.
32069 When several thread group are passed, lists information about those
32070 thread groups. Without any parameters, lists information about all
32071 top-level thread groups.
32073 Normally, thread groups that are being debugged are reported.
32074 With the @samp{--available} option, @value{GDBN} reports thread groups
32075 available on the target.
32077 The output of this command may have either a @samp{threads} result or
32078 a @samp{groups} result. The @samp{thread} result has a list of tuples
32079 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32080 Information}). The @samp{groups} result has a list of tuples as value,
32081 each tuple describing a thread group. If top-level groups are
32082 requested (that is, no parameter is passed), or when several groups
32083 are passed, the output always has a @samp{groups} result. The format
32084 of the @samp{group} result is described below.
32086 To reduce the number of roundtrips it's possible to list thread groups
32087 together with their children, by passing the @samp{--recurse} option
32088 and the recursion depth. Presently, only recursion depth of 1 is
32089 permitted. If this option is present, then every reported thread group
32090 will also include its children, either as @samp{group} or
32091 @samp{threads} field.
32093 In general, any combination of option and parameters is permitted, with
32094 the following caveats:
32098 When a single thread group is passed, the output will typically
32099 be the @samp{threads} result. Because threads may not contain
32100 anything, the @samp{recurse} option will be ignored.
32103 When the @samp{--available} option is passed, limited information may
32104 be available. In particular, the list of threads of a process might
32105 be inaccessible. Further, specifying specific thread groups might
32106 not give any performance advantage over listing all thread groups.
32107 The frontend should assume that @samp{-list-thread-groups --available}
32108 is always an expensive operation and cache the results.
32112 The @samp{groups} result is a list of tuples, where each tuple may
32113 have the following fields:
32117 Identifier of the thread group. This field is always present.
32118 The identifier is an opaque string; frontends should not try to
32119 convert it to an integer, even though it might look like one.
32122 The type of the thread group. At present, only @samp{process} is a
32126 The target-specific process identifier. This field is only present
32127 for thread groups of type @samp{process} and only if the process exists.
32130 The exit code of this group's last exited thread, formatted in octal.
32131 This field is only present for thread groups of type @samp{process} and
32132 only if the process is not running.
32135 The number of children this thread group has. This field may be
32136 absent for an available thread group.
32139 This field has a list of tuples as value, each tuple describing a
32140 thread. It may be present if the @samp{--recurse} option is
32141 specified, and it's actually possible to obtain the threads.
32144 This field is a list of integers, each identifying a core that one
32145 thread of the group is running on. This field may be absent if
32146 such information is not available.
32149 The name of the executable file that corresponds to this thread group.
32150 The field is only present for thread groups of type @samp{process},
32151 and only if there is a corresponding executable file.
32155 @subheading Example
32159 -list-thread-groups
32160 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32161 -list-thread-groups 17
32162 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32163 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32164 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32165 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32166 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32167 -list-thread-groups --available
32168 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32169 -list-thread-groups --available --recurse 1
32170 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32171 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32172 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32173 -list-thread-groups --available --recurse 1 17 18
32174 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32175 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32176 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32179 @subheading The @code{-info-os} Command
32182 @subsubheading Synopsis
32185 -info-os [ @var{type} ]
32188 If no argument is supplied, the command returns a table of available
32189 operating-system-specific information types. If one of these types is
32190 supplied as an argument @var{type}, then the command returns a table
32191 of data of that type.
32193 The types of information available depend on the target operating
32196 @subsubheading @value{GDBN} Command
32198 The corresponding @value{GDBN} command is @samp{info os}.
32200 @subsubheading Example
32202 When run on a @sc{gnu}/Linux system, the output will look something
32208 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32209 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32210 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32211 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32212 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32214 item=@{col0="files",col1="Listing of all file descriptors",
32215 col2="File descriptors"@},
32216 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32217 col2="Kernel modules"@},
32218 item=@{col0="msg",col1="Listing of all message queues",
32219 col2="Message queues"@},
32220 item=@{col0="processes",col1="Listing of all processes",
32221 col2="Processes"@},
32222 item=@{col0="procgroups",col1="Listing of all process groups",
32223 col2="Process groups"@},
32224 item=@{col0="semaphores",col1="Listing of all semaphores",
32225 col2="Semaphores"@},
32226 item=@{col0="shm",col1="Listing of all shared-memory regions",
32227 col2="Shared-memory regions"@},
32228 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32230 item=@{col0="threads",col1="Listing of all threads",
32234 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32235 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32236 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32237 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32238 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32239 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32240 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32241 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32243 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32244 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32248 (Note that the MI output here includes a @code{"Title"} column that
32249 does not appear in command-line @code{info os}; this column is useful
32250 for MI clients that want to enumerate the types of data, such as in a
32251 popup menu, but is needless clutter on the command line, and
32252 @code{info os} omits it.)
32254 @subheading The @code{-add-inferior} Command
32255 @findex -add-inferior
32257 @subheading Synopsis
32263 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32264 inferior is not associated with any executable. Such association may
32265 be established with the @samp{-file-exec-and-symbols} command
32266 (@pxref{GDB/MI File Commands}). The command response has a single
32267 field, @samp{inferior}, whose value is the identifier of the
32268 thread group corresponding to the new inferior.
32270 @subheading Example
32275 ^done,inferior="i3"
32278 @subheading The @code{-interpreter-exec} Command
32279 @findex -interpreter-exec
32281 @subheading Synopsis
32284 -interpreter-exec @var{interpreter} @var{command}
32286 @anchor{-interpreter-exec}
32288 Execute the specified @var{command} in the given @var{interpreter}.
32290 @subheading @value{GDBN} Command
32292 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32294 @subheading Example
32298 -interpreter-exec console "break main"
32299 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32300 &"During symbol reading, bad structure-type format.\n"
32301 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32306 @subheading The @code{-inferior-tty-set} Command
32307 @findex -inferior-tty-set
32309 @subheading Synopsis
32312 -inferior-tty-set /dev/pts/1
32315 Set terminal for future runs of the program being debugged.
32317 @subheading @value{GDBN} Command
32319 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32321 @subheading Example
32325 -inferior-tty-set /dev/pts/1
32330 @subheading The @code{-inferior-tty-show} Command
32331 @findex -inferior-tty-show
32333 @subheading Synopsis
32339 Show terminal for future runs of program being debugged.
32341 @subheading @value{GDBN} Command
32343 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32345 @subheading Example
32349 -inferior-tty-set /dev/pts/1
32353 ^done,inferior_tty_terminal="/dev/pts/1"
32357 @subheading The @code{-enable-timings} Command
32358 @findex -enable-timings
32360 @subheading Synopsis
32363 -enable-timings [yes | no]
32366 Toggle the printing of the wallclock, user and system times for an MI
32367 command as a field in its output. This command is to help frontend
32368 developers optimize the performance of their code. No argument is
32369 equivalent to @samp{yes}.
32371 @subheading @value{GDBN} Command
32375 @subheading Example
32383 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32384 addr="0x080484ed",func="main",file="myprog.c",
32385 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32387 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32395 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32396 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32397 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32398 fullname="/home/nickrob/myprog.c",line="73"@}
32403 @chapter @value{GDBN} Annotations
32405 This chapter describes annotations in @value{GDBN}. Annotations were
32406 designed to interface @value{GDBN} to graphical user interfaces or other
32407 similar programs which want to interact with @value{GDBN} at a
32408 relatively high level.
32410 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32414 This is Edition @value{EDITION}, @value{DATE}.
32418 * Annotations Overview:: What annotations are; the general syntax.
32419 * Server Prefix:: Issuing a command without affecting user state.
32420 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32421 * Errors:: Annotations for error messages.
32422 * Invalidation:: Some annotations describe things now invalid.
32423 * Annotations for Running::
32424 Whether the program is running, how it stopped, etc.
32425 * Source Annotations:: Annotations describing source code.
32428 @node Annotations Overview
32429 @section What is an Annotation?
32430 @cindex annotations
32432 Annotations start with a newline character, two @samp{control-z}
32433 characters, and the name of the annotation. If there is no additional
32434 information associated with this annotation, the name of the annotation
32435 is followed immediately by a newline. If there is additional
32436 information, the name of the annotation is followed by a space, the
32437 additional information, and a newline. The additional information
32438 cannot contain newline characters.
32440 Any output not beginning with a newline and two @samp{control-z}
32441 characters denotes literal output from @value{GDBN}. Currently there is
32442 no need for @value{GDBN} to output a newline followed by two
32443 @samp{control-z} characters, but if there was such a need, the
32444 annotations could be extended with an @samp{escape} annotation which
32445 means those three characters as output.
32447 The annotation @var{level}, which is specified using the
32448 @option{--annotate} command line option (@pxref{Mode Options}), controls
32449 how much information @value{GDBN} prints together with its prompt,
32450 values of expressions, source lines, and other types of output. Level 0
32451 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32452 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32453 for programs that control @value{GDBN}, and level 2 annotations have
32454 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32455 Interface, annotate, GDB's Obsolete Annotations}).
32458 @kindex set annotate
32459 @item set annotate @var{level}
32460 The @value{GDBN} command @code{set annotate} sets the level of
32461 annotations to the specified @var{level}.
32463 @item show annotate
32464 @kindex show annotate
32465 Show the current annotation level.
32468 This chapter describes level 3 annotations.
32470 A simple example of starting up @value{GDBN} with annotations is:
32473 $ @kbd{gdb --annotate=3}
32475 Copyright 2003 Free Software Foundation, Inc.
32476 GDB is free software, covered by the GNU General Public License,
32477 and you are welcome to change it and/or distribute copies of it
32478 under certain conditions.
32479 Type "show copying" to see the conditions.
32480 There is absolutely no warranty for GDB. Type "show warranty"
32482 This GDB was configured as "i386-pc-linux-gnu"
32493 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32494 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32495 denotes a @samp{control-z} character) are annotations; the rest is
32496 output from @value{GDBN}.
32498 @node Server Prefix
32499 @section The Server Prefix
32500 @cindex server prefix
32502 If you prefix a command with @samp{server } then it will not affect
32503 the command history, nor will it affect @value{GDBN}'s notion of which
32504 command to repeat if @key{RET} is pressed on a line by itself. This
32505 means that commands can be run behind a user's back by a front-end in
32506 a transparent manner.
32508 The @code{server } prefix does not affect the recording of values into
32509 the value history; to print a value without recording it into the
32510 value history, use the @code{output} command instead of the
32511 @code{print} command.
32513 Using this prefix also disables confirmation requests
32514 (@pxref{confirmation requests}).
32517 @section Annotation for @value{GDBN} Input
32519 @cindex annotations for prompts
32520 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32521 to know when to send output, when the output from a given command is
32524 Different kinds of input each have a different @dfn{input type}. Each
32525 input type has three annotations: a @code{pre-} annotation, which
32526 denotes the beginning of any prompt which is being output, a plain
32527 annotation, which denotes the end of the prompt, and then a @code{post-}
32528 annotation which denotes the end of any echo which may (or may not) be
32529 associated with the input. For example, the @code{prompt} input type
32530 features the following annotations:
32538 The input types are
32541 @findex pre-prompt annotation
32542 @findex prompt annotation
32543 @findex post-prompt annotation
32545 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32547 @findex pre-commands annotation
32548 @findex commands annotation
32549 @findex post-commands annotation
32551 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32552 command. The annotations are repeated for each command which is input.
32554 @findex pre-overload-choice annotation
32555 @findex overload-choice annotation
32556 @findex post-overload-choice annotation
32557 @item overload-choice
32558 When @value{GDBN} wants the user to select between various overloaded functions.
32560 @findex pre-query annotation
32561 @findex query annotation
32562 @findex post-query annotation
32564 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32566 @findex pre-prompt-for-continue annotation
32567 @findex prompt-for-continue annotation
32568 @findex post-prompt-for-continue annotation
32569 @item prompt-for-continue
32570 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32571 expect this to work well; instead use @code{set height 0} to disable
32572 prompting. This is because the counting of lines is buggy in the
32573 presence of annotations.
32578 @cindex annotations for errors, warnings and interrupts
32580 @findex quit annotation
32585 This annotation occurs right before @value{GDBN} responds to an interrupt.
32587 @findex error annotation
32592 This annotation occurs right before @value{GDBN} responds to an error.
32594 Quit and error annotations indicate that any annotations which @value{GDBN} was
32595 in the middle of may end abruptly. For example, if a
32596 @code{value-history-begin} annotation is followed by a @code{error}, one
32597 cannot expect to receive the matching @code{value-history-end}. One
32598 cannot expect not to receive it either, however; an error annotation
32599 does not necessarily mean that @value{GDBN} is immediately returning all the way
32602 @findex error-begin annotation
32603 A quit or error annotation may be preceded by
32609 Any output between that and the quit or error annotation is the error
32612 Warning messages are not yet annotated.
32613 @c If we want to change that, need to fix warning(), type_error(),
32614 @c range_error(), and possibly other places.
32617 @section Invalidation Notices
32619 @cindex annotations for invalidation messages
32620 The following annotations say that certain pieces of state may have
32624 @findex frames-invalid annotation
32625 @item ^Z^Zframes-invalid
32627 The frames (for example, output from the @code{backtrace} command) may
32630 @findex breakpoints-invalid annotation
32631 @item ^Z^Zbreakpoints-invalid
32633 The breakpoints may have changed. For example, the user just added or
32634 deleted a breakpoint.
32637 @node Annotations for Running
32638 @section Running the Program
32639 @cindex annotations for running programs
32641 @findex starting annotation
32642 @findex stopping annotation
32643 When the program starts executing due to a @value{GDBN} command such as
32644 @code{step} or @code{continue},
32650 is output. When the program stops,
32656 is output. Before the @code{stopped} annotation, a variety of
32657 annotations describe how the program stopped.
32660 @findex exited annotation
32661 @item ^Z^Zexited @var{exit-status}
32662 The program exited, and @var{exit-status} is the exit status (zero for
32663 successful exit, otherwise nonzero).
32665 @findex signalled annotation
32666 @findex signal-name annotation
32667 @findex signal-name-end annotation
32668 @findex signal-string annotation
32669 @findex signal-string-end annotation
32670 @item ^Z^Zsignalled
32671 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32672 annotation continues:
32678 ^Z^Zsignal-name-end
32682 ^Z^Zsignal-string-end
32687 where @var{name} is the name of the signal, such as @code{SIGILL} or
32688 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32689 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32690 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32691 user's benefit and have no particular format.
32693 @findex signal annotation
32695 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32696 just saying that the program received the signal, not that it was
32697 terminated with it.
32699 @findex breakpoint annotation
32700 @item ^Z^Zbreakpoint @var{number}
32701 The program hit breakpoint number @var{number}.
32703 @findex watchpoint annotation
32704 @item ^Z^Zwatchpoint @var{number}
32705 The program hit watchpoint number @var{number}.
32708 @node Source Annotations
32709 @section Displaying Source
32710 @cindex annotations for source display
32712 @findex source annotation
32713 The following annotation is used instead of displaying source code:
32716 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32719 where @var{filename} is an absolute file name indicating which source
32720 file, @var{line} is the line number within that file (where 1 is the
32721 first line in the file), @var{character} is the character position
32722 within the file (where 0 is the first character in the file) (for most
32723 debug formats this will necessarily point to the beginning of a line),
32724 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32725 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32726 @var{addr} is the address in the target program associated with the
32727 source which is being displayed. The @var{addr} is in the form @samp{0x}
32728 followed by one or more lowercase hex digits (note that this does not
32729 depend on the language).
32731 @node JIT Interface
32732 @chapter JIT Compilation Interface
32733 @cindex just-in-time compilation
32734 @cindex JIT compilation interface
32736 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32737 interface. A JIT compiler is a program or library that generates native
32738 executable code at runtime and executes it, usually in order to achieve good
32739 performance while maintaining platform independence.
32741 Programs that use JIT compilation are normally difficult to debug because
32742 portions of their code are generated at runtime, instead of being loaded from
32743 object files, which is where @value{GDBN} normally finds the program's symbols
32744 and debug information. In order to debug programs that use JIT compilation,
32745 @value{GDBN} has an interface that allows the program to register in-memory
32746 symbol files with @value{GDBN} at runtime.
32748 If you are using @value{GDBN} to debug a program that uses this interface, then
32749 it should work transparently so long as you have not stripped the binary. If
32750 you are developing a JIT compiler, then the interface is documented in the rest
32751 of this chapter. At this time, the only known client of this interface is the
32754 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32755 JIT compiler communicates with @value{GDBN} by writing data into a global
32756 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32757 attaches, it reads a linked list of symbol files from the global variable to
32758 find existing code, and puts a breakpoint in the function so that it can find
32759 out about additional code.
32762 * Declarations:: Relevant C struct declarations
32763 * Registering Code:: Steps to register code
32764 * Unregistering Code:: Steps to unregister code
32765 * Custom Debug Info:: Emit debug information in a custom format
32769 @section JIT Declarations
32771 These are the relevant struct declarations that a C program should include to
32772 implement the interface:
32782 struct jit_code_entry
32784 struct jit_code_entry *next_entry;
32785 struct jit_code_entry *prev_entry;
32786 const char *symfile_addr;
32787 uint64_t symfile_size;
32790 struct jit_descriptor
32793 /* This type should be jit_actions_t, but we use uint32_t
32794 to be explicit about the bitwidth. */
32795 uint32_t action_flag;
32796 struct jit_code_entry *relevant_entry;
32797 struct jit_code_entry *first_entry;
32800 /* GDB puts a breakpoint in this function. */
32801 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32803 /* Make sure to specify the version statically, because the
32804 debugger may check the version before we can set it. */
32805 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32808 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32809 modifications to this global data properly, which can easily be done by putting
32810 a global mutex around modifications to these structures.
32812 @node Registering Code
32813 @section Registering Code
32815 To register code with @value{GDBN}, the JIT should follow this protocol:
32819 Generate an object file in memory with symbols and other desired debug
32820 information. The file must include the virtual addresses of the sections.
32823 Create a code entry for the file, which gives the start and size of the symbol
32827 Add it to the linked list in the JIT descriptor.
32830 Point the relevant_entry field of the descriptor at the entry.
32833 Set @code{action_flag} to @code{JIT_REGISTER} and call
32834 @code{__jit_debug_register_code}.
32837 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32838 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32839 new code. However, the linked list must still be maintained in order to allow
32840 @value{GDBN} to attach to a running process and still find the symbol files.
32842 @node Unregistering Code
32843 @section Unregistering Code
32845 If code is freed, then the JIT should use the following protocol:
32849 Remove the code entry corresponding to the code from the linked list.
32852 Point the @code{relevant_entry} field of the descriptor at the code entry.
32855 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32856 @code{__jit_debug_register_code}.
32859 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32860 and the JIT will leak the memory used for the associated symbol files.
32862 @node Custom Debug Info
32863 @section Custom Debug Info
32864 @cindex custom JIT debug info
32865 @cindex JIT debug info reader
32867 Generating debug information in platform-native file formats (like ELF
32868 or COFF) may be an overkill for JIT compilers; especially if all the
32869 debug info is used for is displaying a meaningful backtrace. The
32870 issue can be resolved by having the JIT writers decide on a debug info
32871 format and also provide a reader that parses the debug info generated
32872 by the JIT compiler. This section gives a brief overview on writing
32873 such a parser. More specific details can be found in the source file
32874 @file{gdb/jit-reader.in}, which is also installed as a header at
32875 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32877 The reader is implemented as a shared object (so this functionality is
32878 not available on platforms which don't allow loading shared objects at
32879 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32880 @code{jit-reader-unload} are provided, to be used to load and unload
32881 the readers from a preconfigured directory. Once loaded, the shared
32882 object is used the parse the debug information emitted by the JIT
32886 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32887 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32890 @node Using JIT Debug Info Readers
32891 @subsection Using JIT Debug Info Readers
32892 @kindex jit-reader-load
32893 @kindex jit-reader-unload
32895 Readers can be loaded and unloaded using the @code{jit-reader-load}
32896 and @code{jit-reader-unload} commands.
32899 @item jit-reader-load @var{reader}
32900 Load the JIT reader named @var{reader}, which is a shared
32901 object specified as either an absolute or a relative file name. In
32902 the latter case, @value{GDBN} will try to load the reader from a
32903 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32904 system (here @var{libdir} is the system library directory, often
32905 @file{/usr/local/lib}).
32907 Only one reader can be active at a time; trying to load a second
32908 reader when one is already loaded will result in @value{GDBN}
32909 reporting an error. A new JIT reader can be loaded by first unloading
32910 the current one using @code{jit-reader-unload} and then invoking
32911 @code{jit-reader-load}.
32913 @item jit-reader-unload
32914 Unload the currently loaded JIT reader.
32918 @node Writing JIT Debug Info Readers
32919 @subsection Writing JIT Debug Info Readers
32920 @cindex writing JIT debug info readers
32922 As mentioned, a reader is essentially a shared object conforming to a
32923 certain ABI. This ABI is described in @file{jit-reader.h}.
32925 @file{jit-reader.h} defines the structures, macros and functions
32926 required to write a reader. It is installed (along with
32927 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32928 the system include directory.
32930 Readers need to be released under a GPL compatible license. A reader
32931 can be declared as released under such a license by placing the macro
32932 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32934 The entry point for readers is the symbol @code{gdb_init_reader},
32935 which is expected to be a function with the prototype
32937 @findex gdb_init_reader
32939 extern struct gdb_reader_funcs *gdb_init_reader (void);
32942 @cindex @code{struct gdb_reader_funcs}
32944 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32945 functions. These functions are executed to read the debug info
32946 generated by the JIT compiler (@code{read}), to unwind stack frames
32947 (@code{unwind}) and to create canonical frame IDs
32948 (@code{get_Frame_id}). It also has a callback that is called when the
32949 reader is being unloaded (@code{destroy}). The struct looks like this
32952 struct gdb_reader_funcs
32954 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32955 int reader_version;
32957 /* For use by the reader. */
32960 gdb_read_debug_info *read;
32961 gdb_unwind_frame *unwind;
32962 gdb_get_frame_id *get_frame_id;
32963 gdb_destroy_reader *destroy;
32967 @cindex @code{struct gdb_symbol_callbacks}
32968 @cindex @code{struct gdb_unwind_callbacks}
32970 The callbacks are provided with another set of callbacks by
32971 @value{GDBN} to do their job. For @code{read}, these callbacks are
32972 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32973 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32974 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32975 files and new symbol tables inside those object files. @code{struct
32976 gdb_unwind_callbacks} has callbacks to read registers off the current
32977 frame and to write out the values of the registers in the previous
32978 frame. Both have a callback (@code{target_read}) to read bytes off the
32979 target's address space.
32981 @node In-Process Agent
32982 @chapter In-Process Agent
32983 @cindex debugging agent
32984 The traditional debugging model is conceptually low-speed, but works fine,
32985 because most bugs can be reproduced in debugging-mode execution. However,
32986 as multi-core or many-core processors are becoming mainstream, and
32987 multi-threaded programs become more and more popular, there should be more
32988 and more bugs that only manifest themselves at normal-mode execution, for
32989 example, thread races, because debugger's interference with the program's
32990 timing may conceal the bugs. On the other hand, in some applications,
32991 it is not feasible for the debugger to interrupt the program's execution
32992 long enough for the developer to learn anything helpful about its behavior.
32993 If the program's correctness depends on its real-time behavior, delays
32994 introduced by a debugger might cause the program to fail, even when the
32995 code itself is correct. It is useful to be able to observe the program's
32996 behavior without interrupting it.
32998 Therefore, traditional debugging model is too intrusive to reproduce
32999 some bugs. In order to reduce the interference with the program, we can
33000 reduce the number of operations performed by debugger. The
33001 @dfn{In-Process Agent}, a shared library, is running within the same
33002 process with inferior, and is able to perform some debugging operations
33003 itself. As a result, debugger is only involved when necessary, and
33004 performance of debugging can be improved accordingly. Note that
33005 interference with program can be reduced but can't be removed completely,
33006 because the in-process agent will still stop or slow down the program.
33008 The in-process agent can interpret and execute Agent Expressions
33009 (@pxref{Agent Expressions}) during performing debugging operations. The
33010 agent expressions can be used for different purposes, such as collecting
33011 data in tracepoints, and condition evaluation in breakpoints.
33013 @anchor{Control Agent}
33014 You can control whether the in-process agent is used as an aid for
33015 debugging with the following commands:
33018 @kindex set agent on
33020 Causes the in-process agent to perform some operations on behalf of the
33021 debugger. Just which operations requested by the user will be done
33022 by the in-process agent depends on the its capabilities. For example,
33023 if you request to evaluate breakpoint conditions in the in-process agent,
33024 and the in-process agent has such capability as well, then breakpoint
33025 conditions will be evaluated in the in-process agent.
33027 @kindex set agent off
33028 @item set agent off
33029 Disables execution of debugging operations by the in-process agent. All
33030 of the operations will be performed by @value{GDBN}.
33034 Display the current setting of execution of debugging operations by
33035 the in-process agent.
33039 * In-Process Agent Protocol::
33042 @node In-Process Agent Protocol
33043 @section In-Process Agent Protocol
33044 @cindex in-process agent protocol
33046 The in-process agent is able to communicate with both @value{GDBN} and
33047 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33048 used for communications between @value{GDBN} or GDBserver and the IPA.
33049 In general, @value{GDBN} or GDBserver sends commands
33050 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33051 in-process agent replies back with the return result of the command, or
33052 some other information. The data sent to in-process agent is composed
33053 of primitive data types, such as 4-byte or 8-byte type, and composite
33054 types, which are called objects (@pxref{IPA Protocol Objects}).
33057 * IPA Protocol Objects::
33058 * IPA Protocol Commands::
33061 @node IPA Protocol Objects
33062 @subsection IPA Protocol Objects
33063 @cindex ipa protocol objects
33065 The commands sent to and results received from agent may contain some
33066 complex data types called @dfn{objects}.
33068 The in-process agent is running on the same machine with @value{GDBN}
33069 or GDBserver, so it doesn't have to handle as much differences between
33070 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33071 However, there are still some differences of two ends in two processes:
33075 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33076 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33078 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33079 GDBserver is compiled with one, and in-process agent is compiled with
33083 Here are the IPA Protocol Objects:
33087 agent expression object. It represents an agent expression
33088 (@pxref{Agent Expressions}).
33089 @anchor{agent expression object}
33091 tracepoint action object. It represents a tracepoint action
33092 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33093 memory, static trace data and to evaluate expression.
33094 @anchor{tracepoint action object}
33096 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33097 @anchor{tracepoint object}
33101 The following table describes important attributes of each IPA protocol
33104 @multitable @columnfractions .30 .20 .50
33105 @headitem Name @tab Size @tab Description
33106 @item @emph{agent expression object} @tab @tab
33107 @item length @tab 4 @tab length of bytes code
33108 @item byte code @tab @var{length} @tab contents of byte code
33109 @item @emph{tracepoint action for collecting memory} @tab @tab
33110 @item 'M' @tab 1 @tab type of tracepoint action
33111 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33112 address of the lowest byte to collect, otherwise @var{addr} is the offset
33113 of @var{basereg} for memory collecting.
33114 @item len @tab 8 @tab length of memory for collecting
33115 @item basereg @tab 4 @tab the register number containing the starting
33116 memory address for collecting.
33117 @item @emph{tracepoint action for collecting registers} @tab @tab
33118 @item 'R' @tab 1 @tab type of tracepoint action
33119 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33120 @item 'L' @tab 1 @tab type of tracepoint action
33121 @item @emph{tracepoint action for expression evaluation} @tab @tab
33122 @item 'X' @tab 1 @tab type of tracepoint action
33123 @item agent expression @tab length of @tab @ref{agent expression object}
33124 @item @emph{tracepoint object} @tab @tab
33125 @item number @tab 4 @tab number of tracepoint
33126 @item address @tab 8 @tab address of tracepoint inserted on
33127 @item type @tab 4 @tab type of tracepoint
33128 @item enabled @tab 1 @tab enable or disable of tracepoint
33129 @item step_count @tab 8 @tab step
33130 @item pass_count @tab 8 @tab pass
33131 @item numactions @tab 4 @tab number of tracepoint actions
33132 @item hit count @tab 8 @tab hit count
33133 @item trace frame usage @tab 8 @tab trace frame usage
33134 @item compiled_cond @tab 8 @tab compiled condition
33135 @item orig_size @tab 8 @tab orig size
33136 @item condition @tab 4 if condition is NULL otherwise length of
33137 @ref{agent expression object}
33138 @tab zero if condition is NULL, otherwise is
33139 @ref{agent expression object}
33140 @item actions @tab variable
33141 @tab numactions number of @ref{tracepoint action object}
33144 @node IPA Protocol Commands
33145 @subsection IPA Protocol Commands
33146 @cindex ipa protocol commands
33148 The spaces in each command are delimiters to ease reading this commands
33149 specification. They don't exist in real commands.
33153 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33154 Installs a new fast tracepoint described by @var{tracepoint_object}
33155 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33156 head of @dfn{jumppad}, which is used to jump to data collection routine
33161 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33162 @var{target_address} is address of tracepoint in the inferior.
33163 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33164 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33165 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33166 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33173 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33174 is about to kill inferiors.
33182 @item probe_marker_at:@var{address}
33183 Asks in-process agent to probe the marker at @var{address}.
33190 @item unprobe_marker_at:@var{address}
33191 Asks in-process agent to unprobe the marker at @var{address}.
33195 @chapter Reporting Bugs in @value{GDBN}
33196 @cindex bugs in @value{GDBN}
33197 @cindex reporting bugs in @value{GDBN}
33199 Your bug reports play an essential role in making @value{GDBN} reliable.
33201 Reporting a bug may help you by bringing a solution to your problem, or it
33202 may not. But in any case the principal function of a bug report is to help
33203 the entire community by making the next version of @value{GDBN} work better. Bug
33204 reports are your contribution to the maintenance of @value{GDBN}.
33206 In order for a bug report to serve its purpose, you must include the
33207 information that enables us to fix the bug.
33210 * Bug Criteria:: Have you found a bug?
33211 * Bug Reporting:: How to report bugs
33215 @section Have You Found a Bug?
33216 @cindex bug criteria
33218 If you are not sure whether you have found a bug, here are some guidelines:
33221 @cindex fatal signal
33222 @cindex debugger crash
33223 @cindex crash of debugger
33225 If the debugger gets a fatal signal, for any input whatever, that is a
33226 @value{GDBN} bug. Reliable debuggers never crash.
33228 @cindex error on valid input
33230 If @value{GDBN} produces an error message for valid input, that is a
33231 bug. (Note that if you're cross debugging, the problem may also be
33232 somewhere in the connection to the target.)
33234 @cindex invalid input
33236 If @value{GDBN} does not produce an error message for invalid input,
33237 that is a bug. However, you should note that your idea of
33238 ``invalid input'' might be our idea of ``an extension'' or ``support
33239 for traditional practice''.
33242 If you are an experienced user of debugging tools, your suggestions
33243 for improvement of @value{GDBN} are welcome in any case.
33246 @node Bug Reporting
33247 @section How to Report Bugs
33248 @cindex bug reports
33249 @cindex @value{GDBN} bugs, reporting
33251 A number of companies and individuals offer support for @sc{gnu} products.
33252 If you obtained @value{GDBN} from a support organization, we recommend you
33253 contact that organization first.
33255 You can find contact information for many support companies and
33256 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33258 @c should add a web page ref...
33261 @ifset BUGURL_DEFAULT
33262 In any event, we also recommend that you submit bug reports for
33263 @value{GDBN}. The preferred method is to submit them directly using
33264 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33265 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33268 @strong{Do not send bug reports to @samp{info-gdb}, or to
33269 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33270 not want to receive bug reports. Those that do have arranged to receive
33273 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33274 serves as a repeater. The mailing list and the newsgroup carry exactly
33275 the same messages. Often people think of posting bug reports to the
33276 newsgroup instead of mailing them. This appears to work, but it has one
33277 problem which can be crucial: a newsgroup posting often lacks a mail
33278 path back to the sender. Thus, if we need to ask for more information,
33279 we may be unable to reach you. For this reason, it is better to send
33280 bug reports to the mailing list.
33282 @ifclear BUGURL_DEFAULT
33283 In any event, we also recommend that you submit bug reports for
33284 @value{GDBN} to @value{BUGURL}.
33288 The fundamental principle of reporting bugs usefully is this:
33289 @strong{report all the facts}. If you are not sure whether to state a
33290 fact or leave it out, state it!
33292 Often people omit facts because they think they know what causes the
33293 problem and assume that some details do not matter. Thus, you might
33294 assume that the name of the variable you use in an example does not matter.
33295 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33296 stray memory reference which happens to fetch from the location where that
33297 name is stored in memory; perhaps, if the name were different, the contents
33298 of that location would fool the debugger into doing the right thing despite
33299 the bug. Play it safe and give a specific, complete example. That is the
33300 easiest thing for you to do, and the most helpful.
33302 Keep in mind that the purpose of a bug report is to enable us to fix the
33303 bug. It may be that the bug has been reported previously, but neither
33304 you nor we can know that unless your bug report is complete and
33307 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33308 bell?'' Those bug reports are useless, and we urge everyone to
33309 @emph{refuse to respond to them} except to chide the sender to report
33312 To enable us to fix the bug, you should include all these things:
33316 The version of @value{GDBN}. @value{GDBN} announces it if you start
33317 with no arguments; you can also print it at any time using @code{show
33320 Without this, we will not know whether there is any point in looking for
33321 the bug in the current version of @value{GDBN}.
33324 The type of machine you are using, and the operating system name and
33328 The details of the @value{GDBN} build-time configuration.
33329 @value{GDBN} shows these details if you invoke it with the
33330 @option{--configuration} command-line option, or if you type
33331 @code{show configuration} at @value{GDBN}'s prompt.
33334 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33335 ``@value{GCC}--2.8.1''.
33338 What compiler (and its version) was used to compile the program you are
33339 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33340 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33341 to get this information; for other compilers, see the documentation for
33345 The command arguments you gave the compiler to compile your example and
33346 observe the bug. For example, did you use @samp{-O}? To guarantee
33347 you will not omit something important, list them all. A copy of the
33348 Makefile (or the output from make) is sufficient.
33350 If we were to try to guess the arguments, we would probably guess wrong
33351 and then we might not encounter the bug.
33354 A complete input script, and all necessary source files, that will
33358 A description of what behavior you observe that you believe is
33359 incorrect. For example, ``It gets a fatal signal.''
33361 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33362 will certainly notice it. But if the bug is incorrect output, we might
33363 not notice unless it is glaringly wrong. You might as well not give us
33364 a chance to make a mistake.
33366 Even if the problem you experience is a fatal signal, you should still
33367 say so explicitly. Suppose something strange is going on, such as, your
33368 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33369 the C library on your system. (This has happened!) Your copy might
33370 crash and ours would not. If you told us to expect a crash, then when
33371 ours fails to crash, we would know that the bug was not happening for
33372 us. If you had not told us to expect a crash, then we would not be able
33373 to draw any conclusion from our observations.
33376 @cindex recording a session script
33377 To collect all this information, you can use a session recording program
33378 such as @command{script}, which is available on many Unix systems.
33379 Just run your @value{GDBN} session inside @command{script} and then
33380 include the @file{typescript} file with your bug report.
33382 Another way to record a @value{GDBN} session is to run @value{GDBN}
33383 inside Emacs and then save the entire buffer to a file.
33386 If you wish to suggest changes to the @value{GDBN} source, send us context
33387 diffs. If you even discuss something in the @value{GDBN} source, refer to
33388 it by context, not by line number.
33390 The line numbers in our development sources will not match those in your
33391 sources. Your line numbers would convey no useful information to us.
33395 Here are some things that are not necessary:
33399 A description of the envelope of the bug.
33401 Often people who encounter a bug spend a lot of time investigating
33402 which changes to the input file will make the bug go away and which
33403 changes will not affect it.
33405 This is often time consuming and not very useful, because the way we
33406 will find the bug is by running a single example under the debugger
33407 with breakpoints, not by pure deduction from a series of examples.
33408 We recommend that you save your time for something else.
33410 Of course, if you can find a simpler example to report @emph{instead}
33411 of the original one, that is a convenience for us. Errors in the
33412 output will be easier to spot, running under the debugger will take
33413 less time, and so on.
33415 However, simplification is not vital; if you do not want to do this,
33416 report the bug anyway and send us the entire test case you used.
33419 A patch for the bug.
33421 A patch for the bug does help us if it is a good one. But do not omit
33422 the necessary information, such as the test case, on the assumption that
33423 a patch is all we need. We might see problems with your patch and decide
33424 to fix the problem another way, or we might not understand it at all.
33426 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33427 construct an example that will make the program follow a certain path
33428 through the code. If you do not send us the example, we will not be able
33429 to construct one, so we will not be able to verify that the bug is fixed.
33431 And if we cannot understand what bug you are trying to fix, or why your
33432 patch should be an improvement, we will not install it. A test case will
33433 help us to understand.
33436 A guess about what the bug is or what it depends on.
33438 Such guesses are usually wrong. Even we cannot guess right about such
33439 things without first using the debugger to find the facts.
33442 @c The readline documentation is distributed with the readline code
33443 @c and consists of the two following files:
33446 @c Use -I with makeinfo to point to the appropriate directory,
33447 @c environment var TEXINPUTS with TeX.
33448 @ifclear SYSTEM_READLINE
33449 @include rluser.texi
33450 @include hsuser.texi
33454 @appendix In Memoriam
33456 The @value{GDBN} project mourns the loss of the following long-time
33461 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33462 to Free Software in general. Outside of @value{GDBN}, he was known in
33463 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33465 @item Michael Snyder
33466 Michael was one of the Global Maintainers of the @value{GDBN} project,
33467 with contributions recorded as early as 1996, until 2011. In addition
33468 to his day to day participation, he was a large driving force behind
33469 adding Reverse Debugging to @value{GDBN}.
33472 Beyond their technical contributions to the project, they were also
33473 enjoyable members of the Free Software Community. We will miss them.
33475 @node Formatting Documentation
33476 @appendix Formatting Documentation
33478 @cindex @value{GDBN} reference card
33479 @cindex reference card
33480 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33481 for printing with PostScript or Ghostscript, in the @file{gdb}
33482 subdirectory of the main source directory@footnote{In
33483 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33484 release.}. If you can use PostScript or Ghostscript with your printer,
33485 you can print the reference card immediately with @file{refcard.ps}.
33487 The release also includes the source for the reference card. You
33488 can format it, using @TeX{}, by typing:
33494 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33495 mode on US ``letter'' size paper;
33496 that is, on a sheet 11 inches wide by 8.5 inches
33497 high. You will need to specify this form of printing as an option to
33498 your @sc{dvi} output program.
33500 @cindex documentation
33502 All the documentation for @value{GDBN} comes as part of the machine-readable
33503 distribution. The documentation is written in Texinfo format, which is
33504 a documentation system that uses a single source file to produce both
33505 on-line information and a printed manual. You can use one of the Info
33506 formatting commands to create the on-line version of the documentation
33507 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33509 @value{GDBN} includes an already formatted copy of the on-line Info
33510 version of this manual in the @file{gdb} subdirectory. The main Info
33511 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33512 subordinate files matching @samp{gdb.info*} in the same directory. If
33513 necessary, you can print out these files, or read them with any editor;
33514 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33515 Emacs or the standalone @code{info} program, available as part of the
33516 @sc{gnu} Texinfo distribution.
33518 If you want to format these Info files yourself, you need one of the
33519 Info formatting programs, such as @code{texinfo-format-buffer} or
33522 If you have @code{makeinfo} installed, and are in the top level
33523 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33524 version @value{GDBVN}), you can make the Info file by typing:
33531 If you want to typeset and print copies of this manual, you need @TeX{},
33532 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33533 Texinfo definitions file.
33535 @TeX{} is a typesetting program; it does not print files directly, but
33536 produces output files called @sc{dvi} files. To print a typeset
33537 document, you need a program to print @sc{dvi} files. If your system
33538 has @TeX{} installed, chances are it has such a program. The precise
33539 command to use depends on your system; @kbd{lpr -d} is common; another
33540 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33541 require a file name without any extension or a @samp{.dvi} extension.
33543 @TeX{} also requires a macro definitions file called
33544 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33545 written in Texinfo format. On its own, @TeX{} cannot either read or
33546 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33547 and is located in the @file{gdb-@var{version-number}/texinfo}
33550 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33551 typeset and print this manual. First switch to the @file{gdb}
33552 subdirectory of the main source directory (for example, to
33553 @file{gdb-@value{GDBVN}/gdb}) and type:
33559 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33561 @node Installing GDB
33562 @appendix Installing @value{GDBN}
33563 @cindex installation
33566 * Requirements:: Requirements for building @value{GDBN}
33567 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33568 * Separate Objdir:: Compiling @value{GDBN} in another directory
33569 * Config Names:: Specifying names for hosts and targets
33570 * Configure Options:: Summary of options for configure
33571 * System-wide configuration:: Having a system-wide init file
33575 @section Requirements for Building @value{GDBN}
33576 @cindex building @value{GDBN}, requirements for
33578 Building @value{GDBN} requires various tools and packages to be available.
33579 Other packages will be used only if they are found.
33581 @heading Tools/Packages Necessary for Building @value{GDBN}
33583 @item ISO C90 compiler
33584 @value{GDBN} is written in ISO C90. It should be buildable with any
33585 working C90 compiler, e.g.@: GCC.
33589 @heading Tools/Packages Optional for Building @value{GDBN}
33593 @value{GDBN} can use the Expat XML parsing library. This library may be
33594 included with your operating system distribution; if it is not, you
33595 can get the latest version from @url{http://expat.sourceforge.net}.
33596 The @file{configure} script will search for this library in several
33597 standard locations; if it is installed in an unusual path, you can
33598 use the @option{--with-libexpat-prefix} option to specify its location.
33604 Remote protocol memory maps (@pxref{Memory Map Format})
33606 Target descriptions (@pxref{Target Descriptions})
33608 Remote shared library lists (@xref{Library List Format},
33609 or alternatively @pxref{Library List Format for SVR4 Targets})
33611 MS-Windows shared libraries (@pxref{Shared Libraries})
33613 Traceframe info (@pxref{Traceframe Info Format})
33615 Branch trace (@pxref{Branch Trace Format},
33616 @pxref{Branch Trace Configuration Format})
33620 @cindex compressed debug sections
33621 @value{GDBN} will use the @samp{zlib} library, if available, to read
33622 compressed debug sections. Some linkers, such as GNU gold, are capable
33623 of producing binaries with compressed debug sections. If @value{GDBN}
33624 is compiled with @samp{zlib}, it will be able to read the debug
33625 information in such binaries.
33627 The @samp{zlib} library is likely included with your operating system
33628 distribution; if it is not, you can get the latest version from
33629 @url{http://zlib.net}.
33632 @value{GDBN}'s features related to character sets (@pxref{Character
33633 Sets}) require a functioning @code{iconv} implementation. If you are
33634 on a GNU system, then this is provided by the GNU C Library. Some
33635 other systems also provide a working @code{iconv}.
33637 If @value{GDBN} is using the @code{iconv} program which is installed
33638 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33639 This is done with @option{--with-iconv-bin} which specifies the
33640 directory that contains the @code{iconv} program.
33642 On systems without @code{iconv}, you can install GNU Libiconv. If you
33643 have previously installed Libiconv, you can use the
33644 @option{--with-libiconv-prefix} option to configure.
33646 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33647 arrange to build Libiconv if a directory named @file{libiconv} appears
33648 in the top-most source directory. If Libiconv is built this way, and
33649 if the operating system does not provide a suitable @code{iconv}
33650 implementation, then the just-built library will automatically be used
33651 by @value{GDBN}. One easy way to set this up is to download GNU
33652 Libiconv, unpack it, and then rename the directory holding the
33653 Libiconv source code to @samp{libiconv}.
33656 @node Running Configure
33657 @section Invoking the @value{GDBN} @file{configure} Script
33658 @cindex configuring @value{GDBN}
33659 @value{GDBN} comes with a @file{configure} script that automates the process
33660 of preparing @value{GDBN} for installation; you can then use @code{make} to
33661 build the @code{gdb} program.
33663 @c irrelevant in info file; it's as current as the code it lives with.
33664 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33665 look at the @file{README} file in the sources; we may have improved the
33666 installation procedures since publishing this manual.}
33669 The @value{GDBN} distribution includes all the source code you need for
33670 @value{GDBN} in a single directory, whose name is usually composed by
33671 appending the version number to @samp{gdb}.
33673 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33674 @file{gdb-@value{GDBVN}} directory. That directory contains:
33677 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33678 script for configuring @value{GDBN} and all its supporting libraries
33680 @item gdb-@value{GDBVN}/gdb
33681 the source specific to @value{GDBN} itself
33683 @item gdb-@value{GDBVN}/bfd
33684 source for the Binary File Descriptor library
33686 @item gdb-@value{GDBVN}/include
33687 @sc{gnu} include files
33689 @item gdb-@value{GDBVN}/libiberty
33690 source for the @samp{-liberty} free software library
33692 @item gdb-@value{GDBVN}/opcodes
33693 source for the library of opcode tables and disassemblers
33695 @item gdb-@value{GDBVN}/readline
33696 source for the @sc{gnu} command-line interface
33698 @item gdb-@value{GDBVN}/glob
33699 source for the @sc{gnu} filename pattern-matching subroutine
33701 @item gdb-@value{GDBVN}/mmalloc
33702 source for the @sc{gnu} memory-mapped malloc package
33705 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33706 from the @file{gdb-@var{version-number}} source directory, which in
33707 this example is the @file{gdb-@value{GDBVN}} directory.
33709 First switch to the @file{gdb-@var{version-number}} source directory
33710 if you are not already in it; then run @file{configure}. Pass the
33711 identifier for the platform on which @value{GDBN} will run as an
33717 cd gdb-@value{GDBVN}
33718 ./configure @var{host}
33723 where @var{host} is an identifier such as @samp{sun4} or
33724 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33725 (You can often leave off @var{host}; @file{configure} tries to guess the
33726 correct value by examining your system.)
33728 Running @samp{configure @var{host}} and then running @code{make} builds the
33729 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33730 libraries, then @code{gdb} itself. The configured source files, and the
33731 binaries, are left in the corresponding source directories.
33734 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33735 system does not recognize this automatically when you run a different
33736 shell, you may need to run @code{sh} on it explicitly:
33739 sh configure @var{host}
33742 If you run @file{configure} from a directory that contains source
33743 directories for multiple libraries or programs, such as the
33744 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33746 creates configuration files for every directory level underneath (unless
33747 you tell it not to, with the @samp{--norecursion} option).
33749 You should run the @file{configure} script from the top directory in the
33750 source tree, the @file{gdb-@var{version-number}} directory. If you run
33751 @file{configure} from one of the subdirectories, you will configure only
33752 that subdirectory. That is usually not what you want. In particular,
33753 if you run the first @file{configure} from the @file{gdb} subdirectory
33754 of the @file{gdb-@var{version-number}} directory, you will omit the
33755 configuration of @file{bfd}, @file{readline}, and other sibling
33756 directories of the @file{gdb} subdirectory. This leads to build errors
33757 about missing include files such as @file{bfd/bfd.h}.
33759 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33760 However, you should make sure that the shell on your path (named by
33761 the @samp{SHELL} environment variable) is publicly readable. Remember
33762 that @value{GDBN} uses the shell to start your program---some systems refuse to
33763 let @value{GDBN} debug child processes whose programs are not readable.
33765 @node Separate Objdir
33766 @section Compiling @value{GDBN} in Another Directory
33768 If you want to run @value{GDBN} versions for several host or target machines,
33769 you need a different @code{gdb} compiled for each combination of
33770 host and target. @file{configure} is designed to make this easy by
33771 allowing you to generate each configuration in a separate subdirectory,
33772 rather than in the source directory. If your @code{make} program
33773 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33774 @code{make} in each of these directories builds the @code{gdb}
33775 program specified there.
33777 To build @code{gdb} in a separate directory, run @file{configure}
33778 with the @samp{--srcdir} option to specify where to find the source.
33779 (You also need to specify a path to find @file{configure}
33780 itself from your working directory. If the path to @file{configure}
33781 would be the same as the argument to @samp{--srcdir}, you can leave out
33782 the @samp{--srcdir} option; it is assumed.)
33784 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33785 separate directory for a Sun 4 like this:
33789 cd gdb-@value{GDBVN}
33792 ../gdb-@value{GDBVN}/configure sun4
33797 When @file{configure} builds a configuration using a remote source
33798 directory, it creates a tree for the binaries with the same structure
33799 (and using the same names) as the tree under the source directory. In
33800 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33801 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33802 @file{gdb-sun4/gdb}.
33804 Make sure that your path to the @file{configure} script has just one
33805 instance of @file{gdb} in it. If your path to @file{configure} looks
33806 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33807 one subdirectory of @value{GDBN}, not the whole package. This leads to
33808 build errors about missing include files such as @file{bfd/bfd.h}.
33810 One popular reason to build several @value{GDBN} configurations in separate
33811 directories is to configure @value{GDBN} for cross-compiling (where
33812 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33813 programs that run on another machine---the @dfn{target}).
33814 You specify a cross-debugging target by
33815 giving the @samp{--target=@var{target}} option to @file{configure}.
33817 When you run @code{make} to build a program or library, you must run
33818 it in a configured directory---whatever directory you were in when you
33819 called @file{configure} (or one of its subdirectories).
33821 The @code{Makefile} that @file{configure} generates in each source
33822 directory also runs recursively. If you type @code{make} in a source
33823 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33824 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33825 will build all the required libraries, and then build GDB.
33827 When you have multiple hosts or targets configured in separate
33828 directories, you can run @code{make} on them in parallel (for example,
33829 if they are NFS-mounted on each of the hosts); they will not interfere
33833 @section Specifying Names for Hosts and Targets
33835 The specifications used for hosts and targets in the @file{configure}
33836 script are based on a three-part naming scheme, but some short predefined
33837 aliases are also supported. The full naming scheme encodes three pieces
33838 of information in the following pattern:
33841 @var{architecture}-@var{vendor}-@var{os}
33844 For example, you can use the alias @code{sun4} as a @var{host} argument,
33845 or as the value for @var{target} in a @code{--target=@var{target}}
33846 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33848 The @file{configure} script accompanying @value{GDBN} does not provide
33849 any query facility to list all supported host and target names or
33850 aliases. @file{configure} calls the Bourne shell script
33851 @code{config.sub} to map abbreviations to full names; you can read the
33852 script, if you wish, or you can use it to test your guesses on
33853 abbreviations---for example:
33856 % sh config.sub i386-linux
33858 % sh config.sub alpha-linux
33859 alpha-unknown-linux-gnu
33860 % sh config.sub hp9k700
33862 % sh config.sub sun4
33863 sparc-sun-sunos4.1.1
33864 % sh config.sub sun3
33865 m68k-sun-sunos4.1.1
33866 % sh config.sub i986v
33867 Invalid configuration `i986v': machine `i986v' not recognized
33871 @code{config.sub} is also distributed in the @value{GDBN} source
33872 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33874 @node Configure Options
33875 @section @file{configure} Options
33877 Here is a summary of the @file{configure} options and arguments that
33878 are most often useful for building @value{GDBN}. @file{configure} also has
33879 several other options not listed here. @inforef{What Configure
33880 Does,,configure.info}, for a full explanation of @file{configure}.
33883 configure @r{[}--help@r{]}
33884 @r{[}--prefix=@var{dir}@r{]}
33885 @r{[}--exec-prefix=@var{dir}@r{]}
33886 @r{[}--srcdir=@var{dirname}@r{]}
33887 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33888 @r{[}--target=@var{target}@r{]}
33893 You may introduce options with a single @samp{-} rather than
33894 @samp{--} if you prefer; but you may abbreviate option names if you use
33899 Display a quick summary of how to invoke @file{configure}.
33901 @item --prefix=@var{dir}
33902 Configure the source to install programs and files under directory
33905 @item --exec-prefix=@var{dir}
33906 Configure the source to install programs under directory
33909 @c avoid splitting the warning from the explanation:
33911 @item --srcdir=@var{dirname}
33912 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33913 @code{make} that implements the @code{VPATH} feature.}@*
33914 Use this option to make configurations in directories separate from the
33915 @value{GDBN} source directories. Among other things, you can use this to
33916 build (or maintain) several configurations simultaneously, in separate
33917 directories. @file{configure} writes configuration-specific files in
33918 the current directory, but arranges for them to use the source in the
33919 directory @var{dirname}. @file{configure} creates directories under
33920 the working directory in parallel to the source directories below
33923 @item --norecursion
33924 Configure only the directory level where @file{configure} is executed; do not
33925 propagate configuration to subdirectories.
33927 @item --target=@var{target}
33928 Configure @value{GDBN} for cross-debugging programs running on the specified
33929 @var{target}. Without this option, @value{GDBN} is configured to debug
33930 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33932 There is no convenient way to generate a list of all available targets.
33934 @item @var{host} @dots{}
33935 Configure @value{GDBN} to run on the specified @var{host}.
33937 There is no convenient way to generate a list of all available hosts.
33940 There are many other options available as well, but they are generally
33941 needed for special purposes only.
33943 @node System-wide configuration
33944 @section System-wide configuration and settings
33945 @cindex system-wide init file
33947 @value{GDBN} can be configured to have a system-wide init file;
33948 this file will be read and executed at startup (@pxref{Startup, , What
33949 @value{GDBN} does during startup}).
33951 Here is the corresponding configure option:
33954 @item --with-system-gdbinit=@var{file}
33955 Specify that the default location of the system-wide init file is
33959 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33960 it may be subject to relocation. Two possible cases:
33964 If the default location of this init file contains @file{$prefix},
33965 it will be subject to relocation. Suppose that the configure options
33966 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33967 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33968 init file is looked for as @file{$install/etc/gdbinit} instead of
33969 @file{$prefix/etc/gdbinit}.
33972 By contrast, if the default location does not contain the prefix,
33973 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33974 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33975 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33976 wherever @value{GDBN} is installed.
33979 If the configured location of the system-wide init file (as given by the
33980 @option{--with-system-gdbinit} option at configure time) is in the
33981 data-directory (as specified by @option{--with-gdb-datadir} at configure
33982 time) or in one of its subdirectories, then @value{GDBN} will look for the
33983 system-wide init file in the directory specified by the
33984 @option{--data-directory} command-line option.
33985 Note that the system-wide init file is only read once, during @value{GDBN}
33986 initialization. If the data-directory is changed after @value{GDBN} has
33987 started with the @code{set data-directory} command, the file will not be
33991 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33994 @node System-wide Configuration Scripts
33995 @subsection Installed System-wide Configuration Scripts
33996 @cindex system-wide configuration scripts
33998 The @file{system-gdbinit} directory, located inside the data-directory
33999 (as specified by @option{--with-gdb-datadir} at configure time) contains
34000 a number of scripts which can be used as system-wide init files. To
34001 automatically source those scripts at startup, @value{GDBN} should be
34002 configured with @option{--with-system-gdbinit}. Otherwise, any user
34003 should be able to source them by hand as needed.
34005 The following scripts are currently available:
34008 @item @file{elinos.py}
34010 @cindex ELinOS system-wide configuration script
34011 This script is useful when debugging a program on an ELinOS target.
34012 It takes advantage of the environment variables defined in a standard
34013 ELinOS environment in order to determine the location of the system
34014 shared libraries, and then sets the @samp{solib-absolute-prefix}
34015 and @samp{solib-search-path} variables appropriately.
34017 @item @file{wrs-linux.py}
34018 @pindex wrs-linux.py
34019 @cindex Wind River Linux system-wide configuration script
34020 This script is useful when debugging a program on a target running
34021 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34022 the host-side sysroot used by the target system.
34026 @node Maintenance Commands
34027 @appendix Maintenance Commands
34028 @cindex maintenance commands
34029 @cindex internal commands
34031 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34032 includes a number of commands intended for @value{GDBN} developers,
34033 that are not documented elsewhere in this manual. These commands are
34034 provided here for reference. (For commands that turn on debugging
34035 messages, see @ref{Debugging Output}.)
34038 @kindex maint agent
34039 @kindex maint agent-eval
34040 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34041 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34042 Translate the given @var{expression} into remote agent bytecodes.
34043 This command is useful for debugging the Agent Expression mechanism
34044 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34045 expression useful for data collection, such as by tracepoints, while
34046 @samp{maint agent-eval} produces an expression that evaluates directly
34047 to a result. For instance, a collection expression for @code{globa +
34048 globb} will include bytecodes to record four bytes of memory at each
34049 of the addresses of @code{globa} and @code{globb}, while discarding
34050 the result of the addition, while an evaluation expression will do the
34051 addition and return the sum.
34052 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34053 If not, generate remote agent bytecode for current frame PC address.
34055 @kindex maint agent-printf
34056 @item maint agent-printf @var{format},@var{expr},...
34057 Translate the given format string and list of argument expressions
34058 into remote agent bytecodes and display them as a disassembled list.
34059 This command is useful for debugging the agent version of dynamic
34060 printf (@pxref{Dynamic Printf}).
34062 @kindex maint info breakpoints
34063 @item @anchor{maint info breakpoints}maint info breakpoints
34064 Using the same format as @samp{info breakpoints}, display both the
34065 breakpoints you've set explicitly, and those @value{GDBN} is using for
34066 internal purposes. Internal breakpoints are shown with negative
34067 breakpoint numbers. The type column identifies what kind of breakpoint
34072 Normal, explicitly set breakpoint.
34075 Normal, explicitly set watchpoint.
34078 Internal breakpoint, used to handle correctly stepping through
34079 @code{longjmp} calls.
34081 @item longjmp resume
34082 Internal breakpoint at the target of a @code{longjmp}.
34085 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34088 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34091 Shared library events.
34095 @kindex maint info btrace
34096 @item maint info btrace
34097 Pint information about raw branch tracing data.
34099 @kindex maint btrace packet-history
34100 @item maint btrace packet-history
34101 Print the raw branch trace packets that are used to compute the
34102 execution history for the @samp{record btrace} command. Both the
34103 information and the format in which it is printed depend on the btrace
34108 For the BTS recording format, print a list of blocks of sequential
34109 code. For each block, the following information is printed:
34113 Newer blocks have higher numbers. The oldest block has number zero.
34114 @item Lowest @samp{PC}
34115 @item Highest @samp{PC}
34119 For the Intel Processor Trace recording format, print a list of
34120 Intel Processor Trace packets. For each packet, the following
34121 information is printed:
34124 @item Packet number
34125 Newer packets have higher numbers. The oldest packet has number zero.
34127 The packet's offset in the trace stream.
34128 @item Packet opcode and payload
34132 @kindex maint btrace clear-packet-history
34133 @item maint btrace clear-packet-history
34134 Discards the cached packet history printed by the @samp{maint btrace
34135 packet-history} command. The history will be computed again when
34138 @kindex maint btrace clear
34139 @item maint btrace clear
34140 Discard the branch trace data. The data will be fetched anew and the
34141 branch trace will be recomputed when needed.
34143 This implicitly truncates the branch trace to a single branch trace
34144 buffer. When updating branch trace incrementally, the branch trace
34145 available to @value{GDBN} may be bigger than a single branch trace
34148 @kindex maint set btrace pt skip-pad
34149 @item maint set btrace pt skip-pad
34150 @kindex maint show btrace pt skip-pad
34151 @item maint show btrace pt skip-pad
34152 Control whether @value{GDBN} will skip PAD packets when computing the
34155 @kindex set displaced-stepping
34156 @kindex show displaced-stepping
34157 @cindex displaced stepping support
34158 @cindex out-of-line single-stepping
34159 @item set displaced-stepping
34160 @itemx show displaced-stepping
34161 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34162 if the target supports it. Displaced stepping is a way to single-step
34163 over breakpoints without removing them from the inferior, by executing
34164 an out-of-line copy of the instruction that was originally at the
34165 breakpoint location. It is also known as out-of-line single-stepping.
34168 @item set displaced-stepping on
34169 If the target architecture supports it, @value{GDBN} will use
34170 displaced stepping to step over breakpoints.
34172 @item set displaced-stepping off
34173 @value{GDBN} will not use displaced stepping to step over breakpoints,
34174 even if such is supported by the target architecture.
34176 @cindex non-stop mode, and @samp{set displaced-stepping}
34177 @item set displaced-stepping auto
34178 This is the default mode. @value{GDBN} will use displaced stepping
34179 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34180 architecture supports displaced stepping.
34183 @kindex maint check-psymtabs
34184 @item maint check-psymtabs
34185 Check the consistency of currently expanded psymtabs versus symtabs.
34186 Use this to check, for example, whether a symbol is in one but not the other.
34188 @kindex maint check-symtabs
34189 @item maint check-symtabs
34190 Check the consistency of currently expanded symtabs.
34192 @kindex maint expand-symtabs
34193 @item maint expand-symtabs [@var{regexp}]
34194 Expand symbol tables.
34195 If @var{regexp} is specified, only expand symbol tables for file
34196 names matching @var{regexp}.
34198 @kindex maint set catch-demangler-crashes
34199 @kindex maint show catch-demangler-crashes
34200 @cindex demangler crashes
34201 @item maint set catch-demangler-crashes [on|off]
34202 @itemx maint show catch-demangler-crashes
34203 Control whether @value{GDBN} should attempt to catch crashes in the
34204 symbol name demangler. The default is to attempt to catch crashes.
34205 If enabled, the first time a crash is caught, a core file is created,
34206 the offending symbol is displayed and the user is presented with the
34207 option to terminate the current session.
34209 @kindex maint cplus first_component
34210 @item maint cplus first_component @var{name}
34211 Print the first C@t{++} class/namespace component of @var{name}.
34213 @kindex maint cplus namespace
34214 @item maint cplus namespace
34215 Print the list of possible C@t{++} namespaces.
34217 @kindex maint deprecate
34218 @kindex maint undeprecate
34219 @cindex deprecated commands
34220 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34221 @itemx maint undeprecate @var{command}
34222 Deprecate or undeprecate the named @var{command}. Deprecated commands
34223 cause @value{GDBN} to issue a warning when you use them. The optional
34224 argument @var{replacement} says which newer command should be used in
34225 favor of the deprecated one; if it is given, @value{GDBN} will mention
34226 the replacement as part of the warning.
34228 @kindex maint dump-me
34229 @item maint dump-me
34230 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34231 Cause a fatal signal in the debugger and force it to dump its core.
34232 This is supported only on systems which support aborting a program
34233 with the @code{SIGQUIT} signal.
34235 @kindex maint internal-error
34236 @kindex maint internal-warning
34237 @kindex maint demangler-warning
34238 @cindex demangler crashes
34239 @item maint internal-error @r{[}@var{message-text}@r{]}
34240 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34241 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34243 Cause @value{GDBN} to call the internal function @code{internal_error},
34244 @code{internal_warning} or @code{demangler_warning} and hence behave
34245 as though an internal problem has been detected. In addition to
34246 reporting the internal problem, these functions give the user the
34247 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34248 and @code{internal_warning}) create a core file of the current
34249 @value{GDBN} session.
34251 These commands take an optional parameter @var{message-text} that is
34252 used as the text of the error or warning message.
34254 Here's an example of using @code{internal-error}:
34257 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34258 @dots{}/maint.c:121: internal-error: testing, 1, 2
34259 A problem internal to GDB has been detected. Further
34260 debugging may prove unreliable.
34261 Quit this debugging session? (y or n) @kbd{n}
34262 Create a core file? (y or n) @kbd{n}
34266 @cindex @value{GDBN} internal error
34267 @cindex internal errors, control of @value{GDBN} behavior
34268 @cindex demangler crashes
34270 @kindex maint set internal-error
34271 @kindex maint show internal-error
34272 @kindex maint set internal-warning
34273 @kindex maint show internal-warning
34274 @kindex maint set demangler-warning
34275 @kindex maint show demangler-warning
34276 @item maint set internal-error @var{action} [ask|yes|no]
34277 @itemx maint show internal-error @var{action}
34278 @itemx maint set internal-warning @var{action} [ask|yes|no]
34279 @itemx maint show internal-warning @var{action}
34280 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34281 @itemx maint show demangler-warning @var{action}
34282 When @value{GDBN} reports an internal problem (error or warning) it
34283 gives the user the opportunity to both quit @value{GDBN} and create a
34284 core file of the current @value{GDBN} session. These commands let you
34285 override the default behaviour for each particular @var{action},
34286 described in the table below.
34290 You can specify that @value{GDBN} should always (yes) or never (no)
34291 quit. The default is to ask the user what to do.
34294 You can specify that @value{GDBN} should always (yes) or never (no)
34295 create a core file. The default is to ask the user what to do. Note
34296 that there is no @code{corefile} option for @code{demangler-warning}:
34297 demangler warnings always create a core file and this cannot be
34301 @kindex maint packet
34302 @item maint packet @var{text}
34303 If @value{GDBN} is talking to an inferior via the serial protocol,
34304 then this command sends the string @var{text} to the inferior, and
34305 displays the response packet. @value{GDBN} supplies the initial
34306 @samp{$} character, the terminating @samp{#} character, and the
34309 @kindex maint print architecture
34310 @item maint print architecture @r{[}@var{file}@r{]}
34311 Print the entire architecture configuration. The optional argument
34312 @var{file} names the file where the output goes.
34314 @kindex maint print c-tdesc
34315 @item maint print c-tdesc
34316 Print the current target description (@pxref{Target Descriptions}) as
34317 a C source file. The created source file can be used in @value{GDBN}
34318 when an XML parser is not available to parse the description.
34320 @kindex maint print dummy-frames
34321 @item maint print dummy-frames
34322 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34325 (@value{GDBP}) @kbd{b add}
34327 (@value{GDBP}) @kbd{print add(2,3)}
34328 Breakpoint 2, add (a=2, b=3) at @dots{}
34330 The program being debugged stopped while in a function called from GDB.
34332 (@value{GDBP}) @kbd{maint print dummy-frames}
34333 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34337 Takes an optional file parameter.
34339 @kindex maint print registers
34340 @kindex maint print raw-registers
34341 @kindex maint print cooked-registers
34342 @kindex maint print register-groups
34343 @kindex maint print remote-registers
34344 @item maint print registers @r{[}@var{file}@r{]}
34345 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34346 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34347 @itemx maint print register-groups @r{[}@var{file}@r{]}
34348 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34349 Print @value{GDBN}'s internal register data structures.
34351 The command @code{maint print raw-registers} includes the contents of
34352 the raw register cache; the command @code{maint print
34353 cooked-registers} includes the (cooked) value of all registers,
34354 including registers which aren't available on the target nor visible
34355 to user; the command @code{maint print register-groups} includes the
34356 groups that each register is a member of; and the command @code{maint
34357 print remote-registers} includes the remote target's register numbers
34358 and offsets in the `G' packets.
34360 These commands take an optional parameter, a file name to which to
34361 write the information.
34363 @kindex maint print reggroups
34364 @item maint print reggroups @r{[}@var{file}@r{]}
34365 Print @value{GDBN}'s internal register group data structures. The
34366 optional argument @var{file} tells to what file to write the
34369 The register groups info looks like this:
34372 (@value{GDBP}) @kbd{maint print reggroups}
34385 This command forces @value{GDBN} to flush its internal register cache.
34387 @kindex maint print objfiles
34388 @cindex info for known object files
34389 @item maint print objfiles @r{[}@var{regexp}@r{]}
34390 Print a dump of all known object files.
34391 If @var{regexp} is specified, only print object files whose names
34392 match @var{regexp}. For each object file, this command prints its name,
34393 address in memory, and all of its psymtabs and symtabs.
34395 @kindex maint print user-registers
34396 @cindex user registers
34397 @item maint print user-registers
34398 List all currently available @dfn{user registers}. User registers
34399 typically provide alternate names for actual hardware registers. They
34400 include the four ``standard'' registers @code{$fp}, @code{$pc},
34401 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34402 registers can be used in expressions in the same way as the canonical
34403 register names, but only the latter are listed by the @code{info
34404 registers} and @code{maint print registers} commands.
34406 @kindex maint print section-scripts
34407 @cindex info for known .debug_gdb_scripts-loaded scripts
34408 @item maint print section-scripts [@var{regexp}]
34409 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34410 If @var{regexp} is specified, only print scripts loaded by object files
34411 matching @var{regexp}.
34412 For each script, this command prints its name as specified in the objfile,
34413 and the full path if known.
34414 @xref{dotdebug_gdb_scripts section}.
34416 @kindex maint print statistics
34417 @cindex bcache statistics
34418 @item maint print statistics
34419 This command prints, for each object file in the program, various data
34420 about that object file followed by the byte cache (@dfn{bcache})
34421 statistics for the object file. The objfile data includes the number
34422 of minimal, partial, full, and stabs symbols, the number of types
34423 defined by the objfile, the number of as yet unexpanded psym tables,
34424 the number of line tables and string tables, and the amount of memory
34425 used by the various tables. The bcache statistics include the counts,
34426 sizes, and counts of duplicates of all and unique objects, max,
34427 average, and median entry size, total memory used and its overhead and
34428 savings, and various measures of the hash table size and chain
34431 @kindex maint print target-stack
34432 @cindex target stack description
34433 @item maint print target-stack
34434 A @dfn{target} is an interface between the debugger and a particular
34435 kind of file or process. Targets can be stacked in @dfn{strata},
34436 so that more than one target can potentially respond to a request.
34437 In particular, memory accesses will walk down the stack of targets
34438 until they find a target that is interested in handling that particular
34441 This command prints a short description of each layer that was pushed on
34442 the @dfn{target stack}, starting from the top layer down to the bottom one.
34444 @kindex maint print type
34445 @cindex type chain of a data type
34446 @item maint print type @var{expr}
34447 Print the type chain for a type specified by @var{expr}. The argument
34448 can be either a type name or a symbol. If it is a symbol, the type of
34449 that symbol is described. The type chain produced by this command is
34450 a recursive definition of the data type as stored in @value{GDBN}'s
34451 data structures, including its flags and contained types.
34453 @kindex maint set dwarf always-disassemble
34454 @kindex maint show dwarf always-disassemble
34455 @item maint set dwarf always-disassemble
34456 @item maint show dwarf always-disassemble
34457 Control the behavior of @code{info address} when using DWARF debugging
34460 The default is @code{off}, which means that @value{GDBN} should try to
34461 describe a variable's location in an easily readable format. When
34462 @code{on}, @value{GDBN} will instead display the DWARF location
34463 expression in an assembly-like format. Note that some locations are
34464 too complex for @value{GDBN} to describe simply; in this case you will
34465 always see the disassembly form.
34467 Here is an example of the resulting disassembly:
34470 (gdb) info addr argc
34471 Symbol "argc" is a complex DWARF expression:
34475 For more information on these expressions, see
34476 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34478 @kindex maint set dwarf max-cache-age
34479 @kindex maint show dwarf max-cache-age
34480 @item maint set dwarf max-cache-age
34481 @itemx maint show dwarf max-cache-age
34482 Control the DWARF compilation unit cache.
34484 @cindex DWARF compilation units cache
34485 In object files with inter-compilation-unit references, such as those
34486 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34487 reader needs to frequently refer to previously read compilation units.
34488 This setting controls how long a compilation unit will remain in the
34489 cache if it is not referenced. A higher limit means that cached
34490 compilation units will be stored in memory longer, and more total
34491 memory will be used. Setting it to zero disables caching, which will
34492 slow down @value{GDBN} startup, but reduce memory consumption.
34494 @kindex maint set profile
34495 @kindex maint show profile
34496 @cindex profiling GDB
34497 @item maint set profile
34498 @itemx maint show profile
34499 Control profiling of @value{GDBN}.
34501 Profiling will be disabled until you use the @samp{maint set profile}
34502 command to enable it. When you enable profiling, the system will begin
34503 collecting timing and execution count data; when you disable profiling or
34504 exit @value{GDBN}, the results will be written to a log file. Remember that
34505 if you use profiling, @value{GDBN} will overwrite the profiling log file
34506 (often called @file{gmon.out}). If you have a record of important profiling
34507 data in a @file{gmon.out} file, be sure to move it to a safe location.
34509 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34510 compiled with the @samp{-pg} compiler option.
34512 @kindex maint set show-debug-regs
34513 @kindex maint show show-debug-regs
34514 @cindex hardware debug registers
34515 @item maint set show-debug-regs
34516 @itemx maint show show-debug-regs
34517 Control whether to show variables that mirror the hardware debug
34518 registers. Use @code{on} to enable, @code{off} to disable. If
34519 enabled, the debug registers values are shown when @value{GDBN} inserts or
34520 removes a hardware breakpoint or watchpoint, and when the inferior
34521 triggers a hardware-assisted breakpoint or watchpoint.
34523 @kindex maint set show-all-tib
34524 @kindex maint show show-all-tib
34525 @item maint set show-all-tib
34526 @itemx maint show show-all-tib
34527 Control whether to show all non zero areas within a 1k block starting
34528 at thread local base, when using the @samp{info w32 thread-information-block}
34531 @kindex maint set target-async
34532 @kindex maint show target-async
34533 @item maint set target-async
34534 @itemx maint show target-async
34535 This controls whether @value{GDBN} targets operate in synchronous or
34536 asynchronous mode (@pxref{Background Execution}). Normally the
34537 default is asynchronous, if it is available; but this can be changed
34538 to more easily debug problems occurring only in synchronous mode.
34540 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34541 @kindex maint show target-non-stop
34542 @item maint set target-non-stop
34543 @itemx maint show target-non-stop
34545 This controls whether @value{GDBN} targets always operate in non-stop
34546 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34547 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34548 if supported by the target.
34551 @item maint set target-non-stop auto
34552 This is the default mode. @value{GDBN} controls the target in
34553 non-stop mode if the target supports it.
34555 @item maint set target-non-stop on
34556 @value{GDBN} controls the target in non-stop mode even if the target
34557 does not indicate support.
34559 @item maint set target-non-stop off
34560 @value{GDBN} does not control the target in non-stop mode even if the
34561 target supports it.
34564 @kindex maint set per-command
34565 @kindex maint show per-command
34566 @item maint set per-command
34567 @itemx maint show per-command
34568 @cindex resources used by commands
34570 @value{GDBN} can display the resources used by each command.
34571 This is useful in debugging performance problems.
34574 @item maint set per-command space [on|off]
34575 @itemx maint show per-command space
34576 Enable or disable the printing of the memory used by GDB for each command.
34577 If enabled, @value{GDBN} will display how much memory each command
34578 took, following the command's own output.
34579 This can also be requested by invoking @value{GDBN} with the
34580 @option{--statistics} command-line switch (@pxref{Mode Options}).
34582 @item maint set per-command time [on|off]
34583 @itemx maint show per-command time
34584 Enable or disable the printing of the execution time of @value{GDBN}
34586 If enabled, @value{GDBN} will display how much time it
34587 took to execute each command, following the command's own output.
34588 Both CPU time and wallclock time are printed.
34589 Printing both is useful when trying to determine whether the cost is
34590 CPU or, e.g., disk/network latency.
34591 Note that the CPU time printed is for @value{GDBN} only, it does not include
34592 the execution time of the inferior because there's no mechanism currently
34593 to compute how much time was spent by @value{GDBN} and how much time was
34594 spent by the program been debugged.
34595 This can also be requested by invoking @value{GDBN} with the
34596 @option{--statistics} command-line switch (@pxref{Mode Options}).
34598 @item maint set per-command symtab [on|off]
34599 @itemx maint show per-command symtab
34600 Enable or disable the printing of basic symbol table statistics
34602 If enabled, @value{GDBN} will display the following information:
34606 number of symbol tables
34608 number of primary symbol tables
34610 number of blocks in the blockvector
34614 @kindex maint space
34615 @cindex memory used by commands
34616 @item maint space @var{value}
34617 An alias for @code{maint set per-command space}.
34618 A non-zero value enables it, zero disables it.
34621 @cindex time of command execution
34622 @item maint time @var{value}
34623 An alias for @code{maint set per-command time}.
34624 A non-zero value enables it, zero disables it.
34626 @kindex maint translate-address
34627 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34628 Find the symbol stored at the location specified by the address
34629 @var{addr} and an optional section name @var{section}. If found,
34630 @value{GDBN} prints the name of the closest symbol and an offset from
34631 the symbol's location to the specified address. This is similar to
34632 the @code{info address} command (@pxref{Symbols}), except that this
34633 command also allows to find symbols in other sections.
34635 If section was not specified, the section in which the symbol was found
34636 is also printed. For dynamically linked executables, the name of
34637 executable or shared library containing the symbol is printed as well.
34641 The following command is useful for non-interactive invocations of
34642 @value{GDBN}, such as in the test suite.
34645 @item set watchdog @var{nsec}
34646 @kindex set watchdog
34647 @cindex watchdog timer
34648 @cindex timeout for commands
34649 Set the maximum number of seconds @value{GDBN} will wait for the
34650 target operation to finish. If this time expires, @value{GDBN}
34651 reports and error and the command is aborted.
34653 @item show watchdog
34654 Show the current setting of the target wait timeout.
34657 @node Remote Protocol
34658 @appendix @value{GDBN} Remote Serial Protocol
34663 * Stop Reply Packets::
34664 * General Query Packets::
34665 * Architecture-Specific Protocol Details::
34666 * Tracepoint Packets::
34667 * Host I/O Packets::
34669 * Notification Packets::
34670 * Remote Non-Stop::
34671 * Packet Acknowledgment::
34673 * File-I/O Remote Protocol Extension::
34674 * Library List Format::
34675 * Library List Format for SVR4 Targets::
34676 * Memory Map Format::
34677 * Thread List Format::
34678 * Traceframe Info Format::
34679 * Branch Trace Format::
34680 * Branch Trace Configuration Format::
34686 There may be occasions when you need to know something about the
34687 protocol---for example, if there is only one serial port to your target
34688 machine, you might want your program to do something special if it
34689 recognizes a packet meant for @value{GDBN}.
34691 In the examples below, @samp{->} and @samp{<-} are used to indicate
34692 transmitted and received data, respectively.
34694 @cindex protocol, @value{GDBN} remote serial
34695 @cindex serial protocol, @value{GDBN} remote
34696 @cindex remote serial protocol
34697 All @value{GDBN} commands and responses (other than acknowledgments
34698 and notifications, see @ref{Notification Packets}) are sent as a
34699 @var{packet}. A @var{packet} is introduced with the character
34700 @samp{$}, the actual @var{packet-data}, and the terminating character
34701 @samp{#} followed by a two-digit @var{checksum}:
34704 @code{$}@var{packet-data}@code{#}@var{checksum}
34708 @cindex checksum, for @value{GDBN} remote
34710 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34711 characters between the leading @samp{$} and the trailing @samp{#} (an
34712 eight bit unsigned checksum).
34714 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34715 specification also included an optional two-digit @var{sequence-id}:
34718 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34721 @cindex sequence-id, for @value{GDBN} remote
34723 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34724 has never output @var{sequence-id}s. Stubs that handle packets added
34725 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34727 When either the host or the target machine receives a packet, the first
34728 response expected is an acknowledgment: either @samp{+} (to indicate
34729 the package was received correctly) or @samp{-} (to request
34733 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34738 The @samp{+}/@samp{-} acknowledgments can be disabled
34739 once a connection is established.
34740 @xref{Packet Acknowledgment}, for details.
34742 The host (@value{GDBN}) sends @var{command}s, and the target (the
34743 debugging stub incorporated in your program) sends a @var{response}. In
34744 the case of step and continue @var{command}s, the response is only sent
34745 when the operation has completed, and the target has again stopped all
34746 threads in all attached processes. This is the default all-stop mode
34747 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34748 execution mode; see @ref{Remote Non-Stop}, for details.
34750 @var{packet-data} consists of a sequence of characters with the
34751 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34754 @cindex remote protocol, field separator
34755 Fields within the packet should be separated using @samp{,} @samp{;} or
34756 @samp{:}. Except where otherwise noted all numbers are represented in
34757 @sc{hex} with leading zeros suppressed.
34759 Implementors should note that prior to @value{GDBN} 5.0, the character
34760 @samp{:} could not appear as the third character in a packet (as it
34761 would potentially conflict with the @var{sequence-id}).
34763 @cindex remote protocol, binary data
34764 @anchor{Binary Data}
34765 Binary data in most packets is encoded either as two hexadecimal
34766 digits per byte of binary data. This allowed the traditional remote
34767 protocol to work over connections which were only seven-bit clean.
34768 Some packets designed more recently assume an eight-bit clean
34769 connection, and use a more efficient encoding to send and receive
34772 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34773 as an escape character. Any escaped byte is transmitted as the escape
34774 character followed by the original character XORed with @code{0x20}.
34775 For example, the byte @code{0x7d} would be transmitted as the two
34776 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34777 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34778 @samp{@}}) must always be escaped. Responses sent by the stub
34779 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34780 is not interpreted as the start of a run-length encoded sequence
34783 Response @var{data} can be run-length encoded to save space.
34784 Run-length encoding replaces runs of identical characters with one
34785 instance of the repeated character, followed by a @samp{*} and a
34786 repeat count. The repeat count is itself sent encoded, to avoid
34787 binary characters in @var{data}: a value of @var{n} is sent as
34788 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34789 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34790 code 32) for a repeat count of 3. (This is because run-length
34791 encoding starts to win for counts 3 or more.) Thus, for example,
34792 @samp{0* } is a run-length encoding of ``0000'': the space character
34793 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34796 The printable characters @samp{#} and @samp{$} or with a numeric value
34797 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34798 seven repeats (@samp{$}) can be expanded using a repeat count of only
34799 five (@samp{"}). For example, @samp{00000000} can be encoded as
34802 The error response returned for some packets includes a two character
34803 error number. That number is not well defined.
34805 @cindex empty response, for unsupported packets
34806 For any @var{command} not supported by the stub, an empty response
34807 (@samp{$#00}) should be returned. That way it is possible to extend the
34808 protocol. A newer @value{GDBN} can tell if a packet is supported based
34811 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34812 commands for register access, and the @samp{m} and @samp{M} commands
34813 for memory access. Stubs that only control single-threaded targets
34814 can implement run control with the @samp{c} (continue), and @samp{s}
34815 (step) commands. Stubs that support multi-threading targets should
34816 support the @samp{vCont} command. All other commands are optional.
34821 The following table provides a complete list of all currently defined
34822 @var{command}s and their corresponding response @var{data}.
34823 @xref{File-I/O Remote Protocol Extension}, for details about the File
34824 I/O extension of the remote protocol.
34826 Each packet's description has a template showing the packet's overall
34827 syntax, followed by an explanation of the packet's meaning. We
34828 include spaces in some of the templates for clarity; these are not
34829 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34830 separate its components. For example, a template like @samp{foo
34831 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34832 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34833 @var{baz}. @value{GDBN} does not transmit a space character between the
34834 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34837 @cindex @var{thread-id}, in remote protocol
34838 @anchor{thread-id syntax}
34839 Several packets and replies include a @var{thread-id} field to identify
34840 a thread. Normally these are positive numbers with a target-specific
34841 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34842 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34845 In addition, the remote protocol supports a multiprocess feature in
34846 which the @var{thread-id} syntax is extended to optionally include both
34847 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34848 The @var{pid} (process) and @var{tid} (thread) components each have the
34849 format described above: a positive number with target-specific
34850 interpretation formatted as a big-endian hex string, literal @samp{-1}
34851 to indicate all processes or threads (respectively), or @samp{0} to
34852 indicate an arbitrary process or thread. Specifying just a process, as
34853 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34854 error to specify all processes but a specific thread, such as
34855 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34856 for those packets and replies explicitly documented to include a process
34857 ID, rather than a @var{thread-id}.
34859 The multiprocess @var{thread-id} syntax extensions are only used if both
34860 @value{GDBN} and the stub report support for the @samp{multiprocess}
34861 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34864 Note that all packet forms beginning with an upper- or lower-case
34865 letter, other than those described here, are reserved for future use.
34867 Here are the packet descriptions.
34872 @cindex @samp{!} packet
34873 @anchor{extended mode}
34874 Enable extended mode. In extended mode, the remote server is made
34875 persistent. The @samp{R} packet is used to restart the program being
34881 The remote target both supports and has enabled extended mode.
34885 @cindex @samp{?} packet
34887 Indicate the reason the target halted. The reply is the same as for
34888 step and continue. This packet has a special interpretation when the
34889 target is in non-stop mode; see @ref{Remote Non-Stop}.
34892 @xref{Stop Reply Packets}, for the reply specifications.
34894 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34895 @cindex @samp{A} packet
34896 Initialized @code{argv[]} array passed into program. @var{arglen}
34897 specifies the number of bytes in the hex encoded byte stream
34898 @var{arg}. See @code{gdbserver} for more details.
34903 The arguments were set.
34909 @cindex @samp{b} packet
34910 (Don't use this packet; its behavior is not well-defined.)
34911 Change the serial line speed to @var{baud}.
34913 JTC: @emph{When does the transport layer state change? When it's
34914 received, or after the ACK is transmitted. In either case, there are
34915 problems if the command or the acknowledgment packet is dropped.}
34917 Stan: @emph{If people really wanted to add something like this, and get
34918 it working for the first time, they ought to modify ser-unix.c to send
34919 some kind of out-of-band message to a specially-setup stub and have the
34920 switch happen "in between" packets, so that from remote protocol's point
34921 of view, nothing actually happened.}
34923 @item B @var{addr},@var{mode}
34924 @cindex @samp{B} packet
34925 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34926 breakpoint at @var{addr}.
34928 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34929 (@pxref{insert breakpoint or watchpoint packet}).
34931 @cindex @samp{bc} packet
34934 Backward continue. Execute the target system in reverse. No parameter.
34935 @xref{Reverse Execution}, for more information.
34938 @xref{Stop Reply Packets}, for the reply specifications.
34940 @cindex @samp{bs} packet
34943 Backward single step. Execute one instruction in reverse. No parameter.
34944 @xref{Reverse Execution}, for more information.
34947 @xref{Stop Reply Packets}, for the reply specifications.
34949 @item c @r{[}@var{addr}@r{]}
34950 @cindex @samp{c} packet
34951 Continue at @var{addr}, which is the address to resume. If @var{addr}
34952 is omitted, resume at current address.
34954 This packet is deprecated for multi-threading support. @xref{vCont
34958 @xref{Stop Reply Packets}, for the reply specifications.
34960 @item C @var{sig}@r{[};@var{addr}@r{]}
34961 @cindex @samp{C} packet
34962 Continue with signal @var{sig} (hex signal number). If
34963 @samp{;@var{addr}} is omitted, resume at same address.
34965 This packet is deprecated for multi-threading support. @xref{vCont
34969 @xref{Stop Reply Packets}, for the reply specifications.
34972 @cindex @samp{d} packet
34975 Don't use this packet; instead, define a general set packet
34976 (@pxref{General Query Packets}).
34980 @cindex @samp{D} packet
34981 The first form of the packet is used to detach @value{GDBN} from the
34982 remote system. It is sent to the remote target
34983 before @value{GDBN} disconnects via the @code{detach} command.
34985 The second form, including a process ID, is used when multiprocess
34986 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34987 detach only a specific process. The @var{pid} is specified as a
34988 big-endian hex string.
34998 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34999 @cindex @samp{F} packet
35000 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35001 This is part of the File-I/O protocol extension. @xref{File-I/O
35002 Remote Protocol Extension}, for the specification.
35005 @anchor{read registers packet}
35006 @cindex @samp{g} packet
35007 Read general registers.
35011 @item @var{XX@dots{}}
35012 Each byte of register data is described by two hex digits. The bytes
35013 with the register are transmitted in target byte order. The size of
35014 each register and their position within the @samp{g} packet are
35015 determined by the @value{GDBN} internal gdbarch functions
35016 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35017 specification of several standard @samp{g} packets is specified below.
35019 When reading registers from a trace frame (@pxref{Analyze Collected
35020 Data,,Using the Collected Data}), the stub may also return a string of
35021 literal @samp{x}'s in place of the register data digits, to indicate
35022 that the corresponding register has not been collected, thus its value
35023 is unavailable. For example, for an architecture with 4 registers of
35024 4 bytes each, the following reply indicates to @value{GDBN} that
35025 registers 0 and 2 have not been collected, while registers 1 and 3
35026 have been collected, and both have zero value:
35030 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35037 @item G @var{XX@dots{}}
35038 @cindex @samp{G} packet
35039 Write general registers. @xref{read registers packet}, for a
35040 description of the @var{XX@dots{}} data.
35050 @item H @var{op} @var{thread-id}
35051 @cindex @samp{H} packet
35052 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35053 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35054 should be @samp{c} for step and continue operations (note that this
35055 is deprecated, supporting the @samp{vCont} command is a better
35056 option), and @samp{g} for other operations. The thread designator
35057 @var{thread-id} has the format and interpretation described in
35058 @ref{thread-id syntax}.
35069 @c 'H': How restrictive (or permissive) is the thread model. If a
35070 @c thread is selected and stopped, are other threads allowed
35071 @c to continue to execute? As I mentioned above, I think the
35072 @c semantics of each command when a thread is selected must be
35073 @c described. For example:
35075 @c 'g': If the stub supports threads and a specific thread is
35076 @c selected, returns the register block from that thread;
35077 @c otherwise returns current registers.
35079 @c 'G' If the stub supports threads and a specific thread is
35080 @c selected, sets the registers of the register block of
35081 @c that thread; otherwise sets current registers.
35083 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35084 @anchor{cycle step packet}
35085 @cindex @samp{i} packet
35086 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35087 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35088 step starting at that address.
35091 @cindex @samp{I} packet
35092 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35096 @cindex @samp{k} packet
35099 The exact effect of this packet is not specified.
35101 For a bare-metal target, it may power cycle or reset the target
35102 system. For that reason, the @samp{k} packet has no reply.
35104 For a single-process target, it may kill that process if possible.
35106 A multiple-process target may choose to kill just one process, or all
35107 that are under @value{GDBN}'s control. For more precise control, use
35108 the vKill packet (@pxref{vKill packet}).
35110 If the target system immediately closes the connection in response to
35111 @samp{k}, @value{GDBN} does not consider the lack of packet
35112 acknowledgment to be an error, and assumes the kill was successful.
35114 If connected using @kbd{target extended-remote}, and the target does
35115 not close the connection in response to a kill request, @value{GDBN}
35116 probes the target state as if a new connection was opened
35117 (@pxref{? packet}).
35119 @item m @var{addr},@var{length}
35120 @cindex @samp{m} packet
35121 Read @var{length} addressable memory units starting at address @var{addr}
35122 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35123 any particular boundary.
35125 The stub need not use any particular size or alignment when gathering
35126 data from memory for the response; even if @var{addr} is word-aligned
35127 and @var{length} is a multiple of the word size, the stub is free to
35128 use byte accesses, or not. For this reason, this packet may not be
35129 suitable for accessing memory-mapped I/O devices.
35130 @cindex alignment of remote memory accesses
35131 @cindex size of remote memory accesses
35132 @cindex memory, alignment and size of remote accesses
35136 @item @var{XX@dots{}}
35137 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35138 The reply may contain fewer addressable memory units than requested if the
35139 server was able to read only part of the region of memory.
35144 @item M @var{addr},@var{length}:@var{XX@dots{}}
35145 @cindex @samp{M} packet
35146 Write @var{length} addressable memory units starting at address @var{addr}
35147 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35148 byte is transmitted as a two-digit hexadecimal number.
35155 for an error (this includes the case where only part of the data was
35160 @cindex @samp{p} packet
35161 Read the value of register @var{n}; @var{n} is in hex.
35162 @xref{read registers packet}, for a description of how the returned
35163 register value is encoded.
35167 @item @var{XX@dots{}}
35168 the register's value
35172 Indicating an unrecognized @var{query}.
35175 @item P @var{n@dots{}}=@var{r@dots{}}
35176 @anchor{write register packet}
35177 @cindex @samp{P} packet
35178 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35179 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35180 digits for each byte in the register (target byte order).
35190 @item q @var{name} @var{params}@dots{}
35191 @itemx Q @var{name} @var{params}@dots{}
35192 @cindex @samp{q} packet
35193 @cindex @samp{Q} packet
35194 General query (@samp{q}) and set (@samp{Q}). These packets are
35195 described fully in @ref{General Query Packets}.
35198 @cindex @samp{r} packet
35199 Reset the entire system.
35201 Don't use this packet; use the @samp{R} packet instead.
35204 @cindex @samp{R} packet
35205 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35206 This packet is only available in extended mode (@pxref{extended mode}).
35208 The @samp{R} packet has no reply.
35210 @item s @r{[}@var{addr}@r{]}
35211 @cindex @samp{s} packet
35212 Single step, resuming at @var{addr}. If
35213 @var{addr} is omitted, resume at same address.
35215 This packet is deprecated for multi-threading support. @xref{vCont
35219 @xref{Stop Reply Packets}, for the reply specifications.
35221 @item S @var{sig}@r{[};@var{addr}@r{]}
35222 @anchor{step with signal packet}
35223 @cindex @samp{S} packet
35224 Step with signal. This is analogous to the @samp{C} packet, but
35225 requests a single-step, rather than a normal resumption of execution.
35227 This packet is deprecated for multi-threading support. @xref{vCont
35231 @xref{Stop Reply Packets}, for the reply specifications.
35233 @item t @var{addr}:@var{PP},@var{MM}
35234 @cindex @samp{t} packet
35235 Search backwards starting at address @var{addr} for a match with pattern
35236 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35237 There must be at least 3 digits in @var{addr}.
35239 @item T @var{thread-id}
35240 @cindex @samp{T} packet
35241 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35246 thread is still alive
35252 Packets starting with @samp{v} are identified by a multi-letter name,
35253 up to the first @samp{;} or @samp{?} (or the end of the packet).
35255 @item vAttach;@var{pid}
35256 @cindex @samp{vAttach} packet
35257 Attach to a new process with the specified process ID @var{pid}.
35258 The process ID is a
35259 hexadecimal integer identifying the process. In all-stop mode, all
35260 threads in the attached process are stopped; in non-stop mode, it may be
35261 attached without being stopped if that is supported by the target.
35263 @c In non-stop mode, on a successful vAttach, the stub should set the
35264 @c current thread to a thread of the newly-attached process. After
35265 @c attaching, GDB queries for the attached process's thread ID with qC.
35266 @c Also note that, from a user perspective, whether or not the
35267 @c target is stopped on attach in non-stop mode depends on whether you
35268 @c use the foreground or background version of the attach command, not
35269 @c on what vAttach does; GDB does the right thing with respect to either
35270 @c stopping or restarting threads.
35272 This packet is only available in extended mode (@pxref{extended mode}).
35278 @item @r{Any stop packet}
35279 for success in all-stop mode (@pxref{Stop Reply Packets})
35281 for success in non-stop mode (@pxref{Remote Non-Stop})
35284 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35285 @cindex @samp{vCont} packet
35286 @anchor{vCont packet}
35287 Resume the inferior, specifying different actions for each thread.
35288 If an action is specified with no @var{thread-id}, then it is applied to any
35289 threads that don't have a specific action specified; if no default action is
35290 specified then other threads should remain stopped in all-stop mode and
35291 in their current state in non-stop mode.
35292 Specifying multiple
35293 default actions is an error; specifying no actions is also an error.
35294 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35296 Currently supported actions are:
35302 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35306 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35309 @item r @var{start},@var{end}
35310 Step once, and then keep stepping as long as the thread stops at
35311 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35312 The remote stub reports a stop reply when either the thread goes out
35313 of the range or is stopped due to an unrelated reason, such as hitting
35314 a breakpoint. @xref{range stepping}.
35316 If the range is empty (@var{start} == @var{end}), then the action
35317 becomes equivalent to the @samp{s} action. In other words,
35318 single-step once, and report the stop (even if the stepped instruction
35319 jumps to @var{start}).
35321 (A stop reply may be sent at any point even if the PC is still within
35322 the stepping range; for example, it is valid to implement this packet
35323 in a degenerate way as a single instruction step operation.)
35327 The optional argument @var{addr} normally associated with the
35328 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35329 not supported in @samp{vCont}.
35331 The @samp{t} action is only relevant in non-stop mode
35332 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35333 A stop reply should be generated for any affected thread not already stopped.
35334 When a thread is stopped by means of a @samp{t} action,
35335 the corresponding stop reply should indicate that the thread has stopped with
35336 signal @samp{0}, regardless of whether the target uses some other signal
35337 as an implementation detail.
35339 The stub must support @samp{vCont} if it reports support for
35340 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35341 this case @samp{vCont} actions can be specified to apply to all threads
35342 in a process by using the @samp{p@var{pid}.-1} form of the
35346 @xref{Stop Reply Packets}, for the reply specifications.
35349 @cindex @samp{vCont?} packet
35350 Request a list of actions supported by the @samp{vCont} packet.
35354 @item vCont@r{[};@var{action}@dots{}@r{]}
35355 The @samp{vCont} packet is supported. Each @var{action} is a supported
35356 command in the @samp{vCont} packet.
35358 The @samp{vCont} packet is not supported.
35361 @anchor{vCtrlC packet}
35363 @cindex @samp{vCtrlC} packet
35364 Interrupt remote target as if a control-C was pressed on the remote
35365 terminal. This is the equivalent to reacting to the @code{^C}
35366 (@samp{\003}, the control-C character) character in all-stop mode
35367 while the target is running, except this works in non-stop mode.
35368 @xref{interrupting remote targets}, for more info on the all-stop
35379 @item vFile:@var{operation}:@var{parameter}@dots{}
35380 @cindex @samp{vFile} packet
35381 Perform a file operation on the target system. For details,
35382 see @ref{Host I/O Packets}.
35384 @item vFlashErase:@var{addr},@var{length}
35385 @cindex @samp{vFlashErase} packet
35386 Direct the stub to erase @var{length} bytes of flash starting at
35387 @var{addr}. The region may enclose any number of flash blocks, but
35388 its start and end must fall on block boundaries, as indicated by the
35389 flash block size appearing in the memory map (@pxref{Memory Map
35390 Format}). @value{GDBN} groups flash memory programming operations
35391 together, and sends a @samp{vFlashDone} request after each group; the
35392 stub is allowed to delay erase operation until the @samp{vFlashDone}
35393 packet is received.
35403 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35404 @cindex @samp{vFlashWrite} packet
35405 Direct the stub to write data to flash address @var{addr}. The data
35406 is passed in binary form using the same encoding as for the @samp{X}
35407 packet (@pxref{Binary Data}). The memory ranges specified by
35408 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35409 not overlap, and must appear in order of increasing addresses
35410 (although @samp{vFlashErase} packets for higher addresses may already
35411 have been received; the ordering is guaranteed only between
35412 @samp{vFlashWrite} packets). If a packet writes to an address that was
35413 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35414 target-specific method, the results are unpredictable.
35422 for vFlashWrite addressing non-flash memory
35428 @cindex @samp{vFlashDone} packet
35429 Indicate to the stub that flash programming operation is finished.
35430 The stub is permitted to delay or batch the effects of a group of
35431 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35432 @samp{vFlashDone} packet is received. The contents of the affected
35433 regions of flash memory are unpredictable until the @samp{vFlashDone}
35434 request is completed.
35436 @item vKill;@var{pid}
35437 @cindex @samp{vKill} packet
35438 @anchor{vKill packet}
35439 Kill the process with the specified process ID @var{pid}, which is a
35440 hexadecimal integer identifying the process. This packet is used in
35441 preference to @samp{k} when multiprocess protocol extensions are
35442 supported; see @ref{multiprocess extensions}.
35452 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35453 @cindex @samp{vRun} packet
35454 Run the program @var{filename}, passing it each @var{argument} on its
35455 command line. The file and arguments are hex-encoded strings. If
35456 @var{filename} is an empty string, the stub may use a default program
35457 (e.g.@: the last program run). The program is created in the stopped
35460 @c FIXME: What about non-stop mode?
35462 This packet is only available in extended mode (@pxref{extended mode}).
35468 @item @r{Any stop packet}
35469 for success (@pxref{Stop Reply Packets})
35473 @cindex @samp{vStopped} packet
35474 @xref{Notification Packets}.
35476 @item X @var{addr},@var{length}:@var{XX@dots{}}
35478 @cindex @samp{X} packet
35479 Write data to memory, where the data is transmitted in binary.
35480 Memory is specified by its address @var{addr} and number of addressable memory
35481 units @var{length} (@pxref{addressable memory unit});
35482 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35492 @item z @var{type},@var{addr},@var{kind}
35493 @itemx Z @var{type},@var{addr},@var{kind}
35494 @anchor{insert breakpoint or watchpoint packet}
35495 @cindex @samp{z} packet
35496 @cindex @samp{Z} packets
35497 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35498 watchpoint starting at address @var{address} of kind @var{kind}.
35500 Each breakpoint and watchpoint packet @var{type} is documented
35503 @emph{Implementation notes: A remote target shall return an empty string
35504 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35505 remote target shall support either both or neither of a given
35506 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35507 avoid potential problems with duplicate packets, the operations should
35508 be implemented in an idempotent way.}
35510 @item z0,@var{addr},@var{kind}
35511 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35512 @cindex @samp{z0} packet
35513 @cindex @samp{Z0} packet
35514 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35515 @var{addr} of type @var{kind}.
35517 A memory breakpoint is implemented by replacing the instruction at
35518 @var{addr} with a software breakpoint or trap instruction. The
35519 @var{kind} is target-specific and typically indicates the size of
35520 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35521 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35522 architectures have additional meanings for @var{kind};
35523 @var{cond_list} is an optional list of conditional expressions in bytecode
35524 form that should be evaluated on the target's side. These are the
35525 conditions that should be taken into consideration when deciding if
35526 the breakpoint trigger should be reported back to @var{GDBN}.
35528 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35529 for how to best report a memory breakpoint event to @value{GDBN}.
35531 The @var{cond_list} parameter is comprised of a series of expressions,
35532 concatenated without separators. Each expression has the following form:
35536 @item X @var{len},@var{expr}
35537 @var{len} is the length of the bytecode expression and @var{expr} is the
35538 actual conditional expression in bytecode form.
35542 The optional @var{cmd_list} parameter introduces commands that may be
35543 run on the target, rather than being reported back to @value{GDBN}.
35544 The parameter starts with a numeric flag @var{persist}; if the flag is
35545 nonzero, then the breakpoint may remain active and the commands
35546 continue to be run even when @value{GDBN} disconnects from the target.
35547 Following this flag is a series of expressions concatenated with no
35548 separators. Each expression has the following form:
35552 @item X @var{len},@var{expr}
35553 @var{len} is the length of the bytecode expression and @var{expr} is the
35554 actual conditional expression in bytecode form.
35558 see @ref{Architecture-Specific Protocol Details}.
35560 @emph{Implementation note: It is possible for a target to copy or move
35561 code that contains memory breakpoints (e.g., when implementing
35562 overlays). The behavior of this packet, in the presence of such a
35563 target, is not defined.}
35575 @item z1,@var{addr},@var{kind}
35576 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35577 @cindex @samp{z1} packet
35578 @cindex @samp{Z1} packet
35579 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35580 address @var{addr}.
35582 A hardware breakpoint is implemented using a mechanism that is not
35583 dependant on being able to modify the target's memory. The @var{kind}
35584 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35586 @emph{Implementation note: A hardware breakpoint is not affected by code
35599 @item z2,@var{addr},@var{kind}
35600 @itemx Z2,@var{addr},@var{kind}
35601 @cindex @samp{z2} packet
35602 @cindex @samp{Z2} packet
35603 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35604 The number of bytes to watch is specified by @var{kind}.
35616 @item z3,@var{addr},@var{kind}
35617 @itemx Z3,@var{addr},@var{kind}
35618 @cindex @samp{z3} packet
35619 @cindex @samp{Z3} packet
35620 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35621 The number of bytes to watch is specified by @var{kind}.
35633 @item z4,@var{addr},@var{kind}
35634 @itemx Z4,@var{addr},@var{kind}
35635 @cindex @samp{z4} packet
35636 @cindex @samp{Z4} packet
35637 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35638 The number of bytes to watch is specified by @var{kind}.
35652 @node Stop Reply Packets
35653 @section Stop Reply Packets
35654 @cindex stop reply packets
35656 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35657 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35658 receive any of the below as a reply. Except for @samp{?}
35659 and @samp{vStopped}, that reply is only returned
35660 when the target halts. In the below the exact meaning of @dfn{signal
35661 number} is defined by the header @file{include/gdb/signals.h} in the
35662 @value{GDBN} source code.
35664 As in the description of request packets, we include spaces in the
35665 reply templates for clarity; these are not part of the reply packet's
35666 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35672 The program received signal number @var{AA} (a two-digit hexadecimal
35673 number). This is equivalent to a @samp{T} response with no
35674 @var{n}:@var{r} pairs.
35676 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35677 @cindex @samp{T} packet reply
35678 The program received signal number @var{AA} (a two-digit hexadecimal
35679 number). This is equivalent to an @samp{S} response, except that the
35680 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35681 and other information directly in the stop reply packet, reducing
35682 round-trip latency. Single-step and breakpoint traps are reported
35683 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35687 If @var{n} is a hexadecimal number, it is a register number, and the
35688 corresponding @var{r} gives that register's value. The data @var{r} is a
35689 series of bytes in target byte order, with each byte given by a
35690 two-digit hex number.
35693 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35694 the stopped thread, as specified in @ref{thread-id syntax}.
35697 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35698 the core on which the stop event was detected.
35701 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35702 specific event that stopped the target. The currently defined stop
35703 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35704 signal. At most one stop reason should be present.
35707 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35708 and go on to the next; this allows us to extend the protocol in the
35712 The currently defined stop reasons are:
35718 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35721 @item syscall_entry
35722 @itemx syscall_return
35723 The packet indicates a syscall entry or return, and @var{r} is the
35724 syscall number, in hex.
35726 @cindex shared library events, remote reply
35728 The packet indicates that the loaded libraries have changed.
35729 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35730 list of loaded libraries. The @var{r} part is ignored.
35732 @cindex replay log events, remote reply
35734 The packet indicates that the target cannot continue replaying
35735 logged execution events, because it has reached the end (or the
35736 beginning when executing backward) of the log. The value of @var{r}
35737 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35738 for more information.
35741 @anchor{swbreak stop reason}
35742 The packet indicates a memory breakpoint instruction was executed,
35743 irrespective of whether it was @value{GDBN} that planted the
35744 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35745 part must be left empty.
35747 On some architectures, such as x86, at the architecture level, when a
35748 breakpoint instruction executes the program counter points at the
35749 breakpoint address plus an offset. On such targets, the stub is
35750 responsible for adjusting the PC to point back at the breakpoint
35753 This packet should not be sent by default; older @value{GDBN} versions
35754 did not support it. @value{GDBN} requests it, by supplying an
35755 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35756 remote stub must also supply the appropriate @samp{qSupported} feature
35757 indicating support.
35759 This packet is required for correct non-stop mode operation.
35762 The packet indicates the target stopped for a hardware breakpoint.
35763 The @var{r} part must be left empty.
35765 The same remarks about @samp{qSupported} and non-stop mode above
35768 @cindex fork events, remote reply
35770 The packet indicates that @code{fork} was called, and @var{r}
35771 is the thread ID of the new child process. Refer to
35772 @ref{thread-id syntax} for the format of the @var{thread-id}
35773 field. This packet is only applicable to targets that support
35776 This packet should not be sent by default; older @value{GDBN} versions
35777 did not support it. @value{GDBN} requests it, by supplying an
35778 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35779 remote stub must also supply the appropriate @samp{qSupported} feature
35780 indicating support.
35782 @cindex vfork events, remote reply
35784 The packet indicates that @code{vfork} was called, and @var{r}
35785 is the thread ID of the new child process. Refer to
35786 @ref{thread-id syntax} for the format of the @var{thread-id}
35787 field. This packet is only applicable to targets that support
35790 This packet should not be sent by default; older @value{GDBN} versions
35791 did not support it. @value{GDBN} requests it, by supplying an
35792 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35793 remote stub must also supply the appropriate @samp{qSupported} feature
35794 indicating support.
35796 @cindex vforkdone events, remote reply
35798 The packet indicates that a child process created by a vfork
35799 has either called @code{exec} or terminated, so that the
35800 address spaces of the parent and child process are no longer
35801 shared. The @var{r} part is ignored. This packet is only
35802 applicable to targets that support vforkdone events.
35804 This packet should not be sent by default; older @value{GDBN} versions
35805 did not support it. @value{GDBN} requests it, by supplying an
35806 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35807 remote stub must also supply the appropriate @samp{qSupported} feature
35808 indicating support.
35810 @cindex exec events, remote reply
35812 The packet indicates that @code{execve} was called, and @var{r}
35813 is the absolute pathname of the file that was executed, in hex.
35814 This packet is only applicable to targets that support exec events.
35816 This packet should not be sent by default; older @value{GDBN} versions
35817 did not support it. @value{GDBN} requests it, by supplying an
35818 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35819 remote stub must also supply the appropriate @samp{qSupported} feature
35820 indicating support.
35822 @cindex thread create event, remote reply
35823 @anchor{thread create event}
35825 The packet indicates that the thread was just created. The new thread
35826 is stopped until @value{GDBN} sets it running with a resumption packet
35827 (@pxref{vCont packet}). This packet should not be sent by default;
35828 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35829 also the @samp{w} (@ref{thread exit event}) remote reply below.
35834 @itemx W @var{AA} ; process:@var{pid}
35835 The process exited, and @var{AA} is the exit status. This is only
35836 applicable to certain targets.
35838 The second form of the response, including the process ID of the exited
35839 process, can be used only when @value{GDBN} has reported support for
35840 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35841 The @var{pid} is formatted as a big-endian hex string.
35844 @itemx X @var{AA} ; process:@var{pid}
35845 The process terminated with signal @var{AA}.
35847 The second form of the response, including the process ID of the
35848 terminated process, can be used only when @value{GDBN} has reported
35849 support for multiprocess protocol extensions; see @ref{multiprocess
35850 extensions}. The @var{pid} is formatted as a big-endian hex string.
35852 @anchor{thread exit event}
35853 @cindex thread exit event, remote reply
35854 @item w @var{AA} ; @var{tid}
35856 The thread exited, and @var{AA} is the exit status. This response
35857 should not be sent by default; @value{GDBN} requests it with the
35858 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35861 There are no resumed threads left in the target. In other words, even
35862 though the process is alive, the last resumed thread has exited. For
35863 example, say the target process has two threads: thread 1 and thread
35864 2. The client leaves thread 1 stopped, and resumes thread 2, which
35865 subsequently exits. At this point, even though the process is still
35866 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35867 executing either. The @samp{N} stop reply thus informs the client
35868 that it can stop waiting for stop replies. This packet should not be
35869 sent by default; older @value{GDBN} versions did not support it.
35870 @value{GDBN} requests it, by supplying an appropriate
35871 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35872 also supply the appropriate @samp{qSupported} feature indicating
35875 @item O @var{XX}@dots{}
35876 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35877 written as the program's console output. This can happen at any time
35878 while the program is running and the debugger should continue to wait
35879 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35881 @item F @var{call-id},@var{parameter}@dots{}
35882 @var{call-id} is the identifier which says which host system call should
35883 be called. This is just the name of the function. Translation into the
35884 correct system call is only applicable as it's defined in @value{GDBN}.
35885 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35888 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35889 this very system call.
35891 The target replies with this packet when it expects @value{GDBN} to
35892 call a host system call on behalf of the target. @value{GDBN} replies
35893 with an appropriate @samp{F} packet and keeps up waiting for the next
35894 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35895 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35896 Protocol Extension}, for more details.
35900 @node General Query Packets
35901 @section General Query Packets
35902 @cindex remote query requests
35904 Packets starting with @samp{q} are @dfn{general query packets};
35905 packets starting with @samp{Q} are @dfn{general set packets}. General
35906 query and set packets are a semi-unified form for retrieving and
35907 sending information to and from the stub.
35909 The initial letter of a query or set packet is followed by a name
35910 indicating what sort of thing the packet applies to. For example,
35911 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35912 definitions with the stub. These packet names follow some
35917 The name must not contain commas, colons or semicolons.
35919 Most @value{GDBN} query and set packets have a leading upper case
35922 The names of custom vendor packets should use a company prefix, in
35923 lower case, followed by a period. For example, packets designed at
35924 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35925 foos) or @samp{Qacme.bar} (for setting bars).
35928 The name of a query or set packet should be separated from any
35929 parameters by a @samp{:}; the parameters themselves should be
35930 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35931 full packet name, and check for a separator or the end of the packet,
35932 in case two packet names share a common prefix. New packets should not begin
35933 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35934 packets predate these conventions, and have arguments without any terminator
35935 for the packet name; we suspect they are in widespread use in places that
35936 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35937 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35940 Like the descriptions of the other packets, each description here
35941 has a template showing the packet's overall syntax, followed by an
35942 explanation of the packet's meaning. We include spaces in some of the
35943 templates for clarity; these are not part of the packet's syntax. No
35944 @value{GDBN} packet uses spaces to separate its components.
35946 Here are the currently defined query and set packets:
35952 Turn on or off the agent as a helper to perform some debugging operations
35953 delegated from @value{GDBN} (@pxref{Control Agent}).
35955 @item QAllow:@var{op}:@var{val}@dots{}
35956 @cindex @samp{QAllow} packet
35957 Specify which operations @value{GDBN} expects to request of the
35958 target, as a semicolon-separated list of operation name and value
35959 pairs. Possible values for @var{op} include @samp{WriteReg},
35960 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35961 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35962 indicating that @value{GDBN} will not request the operation, or 1,
35963 indicating that it may. (The target can then use this to set up its
35964 own internals optimally, for instance if the debugger never expects to
35965 insert breakpoints, it may not need to install its own trap handler.)
35968 @cindex current thread, remote request
35969 @cindex @samp{qC} packet
35970 Return the current thread ID.
35974 @item QC @var{thread-id}
35975 Where @var{thread-id} is a thread ID as documented in
35976 @ref{thread-id syntax}.
35977 @item @r{(anything else)}
35978 Any other reply implies the old thread ID.
35981 @item qCRC:@var{addr},@var{length}
35982 @cindex CRC of memory block, remote request
35983 @cindex @samp{qCRC} packet
35984 @anchor{qCRC packet}
35985 Compute the CRC checksum of a block of memory using CRC-32 defined in
35986 IEEE 802.3. The CRC is computed byte at a time, taking the most
35987 significant bit of each byte first. The initial pattern code
35988 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35990 @emph{Note:} This is the same CRC used in validating separate debug
35991 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35992 Files}). However the algorithm is slightly different. When validating
35993 separate debug files, the CRC is computed taking the @emph{least}
35994 significant bit of each byte first, and the final result is inverted to
35995 detect trailing zeros.
36000 An error (such as memory fault)
36001 @item C @var{crc32}
36002 The specified memory region's checksum is @var{crc32}.
36005 @item QDisableRandomization:@var{value}
36006 @cindex disable address space randomization, remote request
36007 @cindex @samp{QDisableRandomization} packet
36008 Some target operating systems will randomize the virtual address space
36009 of the inferior process as a security feature, but provide a feature
36010 to disable such randomization, e.g.@: to allow for a more deterministic
36011 debugging experience. On such systems, this packet with a @var{value}
36012 of 1 directs the target to disable address space randomization for
36013 processes subsequently started via @samp{vRun} packets, while a packet
36014 with a @var{value} of 0 tells the target to enable address space
36017 This packet is only available in extended mode (@pxref{extended mode}).
36022 The request succeeded.
36025 An error occurred. The error number @var{nn} is given as hex digits.
36028 An empty reply indicates that @samp{QDisableRandomization} is not supported
36032 This packet is not probed by default; the remote stub must request it,
36033 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36034 This should only be done on targets that actually support disabling
36035 address space randomization.
36038 @itemx qsThreadInfo
36039 @cindex list active threads, remote request
36040 @cindex @samp{qfThreadInfo} packet
36041 @cindex @samp{qsThreadInfo} packet
36042 Obtain a list of all active thread IDs from the target (OS). Since there
36043 may be too many active threads to fit into one reply packet, this query
36044 works iteratively: it may require more than one query/reply sequence to
36045 obtain the entire list of threads. The first query of the sequence will
36046 be the @samp{qfThreadInfo} query; subsequent queries in the
36047 sequence will be the @samp{qsThreadInfo} query.
36049 NOTE: This packet replaces the @samp{qL} query (see below).
36053 @item m @var{thread-id}
36055 @item m @var{thread-id},@var{thread-id}@dots{}
36056 a comma-separated list of thread IDs
36058 (lower case letter @samp{L}) denotes end of list.
36061 In response to each query, the target will reply with a list of one or
36062 more thread IDs, separated by commas.
36063 @value{GDBN} will respond to each reply with a request for more thread
36064 ids (using the @samp{qs} form of the query), until the target responds
36065 with @samp{l} (lower-case ell, for @dfn{last}).
36066 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36069 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36070 initial connection with the remote target, and the very first thread ID
36071 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36072 message. Therefore, the stub should ensure that the first thread ID in
36073 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36075 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36076 @cindex get thread-local storage address, remote request
36077 @cindex @samp{qGetTLSAddr} packet
36078 Fetch the address associated with thread local storage specified
36079 by @var{thread-id}, @var{offset}, and @var{lm}.
36081 @var{thread-id} is the thread ID associated with the
36082 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36084 @var{offset} is the (big endian, hex encoded) offset associated with the
36085 thread local variable. (This offset is obtained from the debug
36086 information associated with the variable.)
36088 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36089 load module associated with the thread local storage. For example,
36090 a @sc{gnu}/Linux system will pass the link map address of the shared
36091 object associated with the thread local storage under consideration.
36092 Other operating environments may choose to represent the load module
36093 differently, so the precise meaning of this parameter will vary.
36097 @item @var{XX}@dots{}
36098 Hex encoded (big endian) bytes representing the address of the thread
36099 local storage requested.
36102 An error occurred. The error number @var{nn} is given as hex digits.
36105 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36108 @item qGetTIBAddr:@var{thread-id}
36109 @cindex get thread information block address
36110 @cindex @samp{qGetTIBAddr} packet
36111 Fetch address of the Windows OS specific Thread Information Block.
36113 @var{thread-id} is the thread ID associated with the thread.
36117 @item @var{XX}@dots{}
36118 Hex encoded (big endian) bytes representing the linear address of the
36119 thread information block.
36122 An error occured. This means that either the thread was not found, or the
36123 address could not be retrieved.
36126 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36129 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36130 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36131 digit) is one to indicate the first query and zero to indicate a
36132 subsequent query; @var{threadcount} (two hex digits) is the maximum
36133 number of threads the response packet can contain; and @var{nextthread}
36134 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36135 returned in the response as @var{argthread}.
36137 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36141 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36142 Where: @var{count} (two hex digits) is the number of threads being
36143 returned; @var{done} (one hex digit) is zero to indicate more threads
36144 and one indicates no further threads; @var{argthreadid} (eight hex
36145 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36146 is a sequence of thread IDs, @var{threadid} (eight hex
36147 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36151 @cindex section offsets, remote request
36152 @cindex @samp{qOffsets} packet
36153 Get section offsets that the target used when relocating the downloaded
36158 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36159 Relocate the @code{Text} section by @var{xxx} from its original address.
36160 Relocate the @code{Data} section by @var{yyy} from its original address.
36161 If the object file format provides segment information (e.g.@: @sc{elf}
36162 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36163 segments by the supplied offsets.
36165 @emph{Note: while a @code{Bss} offset may be included in the response,
36166 @value{GDBN} ignores this and instead applies the @code{Data} offset
36167 to the @code{Bss} section.}
36169 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36170 Relocate the first segment of the object file, which conventionally
36171 contains program code, to a starting address of @var{xxx}. If
36172 @samp{DataSeg} is specified, relocate the second segment, which
36173 conventionally contains modifiable data, to a starting address of
36174 @var{yyy}. @value{GDBN} will report an error if the object file
36175 does not contain segment information, or does not contain at least
36176 as many segments as mentioned in the reply. Extra segments are
36177 kept at fixed offsets relative to the last relocated segment.
36180 @item qP @var{mode} @var{thread-id}
36181 @cindex thread information, remote request
36182 @cindex @samp{qP} packet
36183 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36184 encoded 32 bit mode; @var{thread-id} is a thread ID
36185 (@pxref{thread-id syntax}).
36187 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36190 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36194 @cindex non-stop mode, remote request
36195 @cindex @samp{QNonStop} packet
36197 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36198 @xref{Remote Non-Stop}, for more information.
36203 The request succeeded.
36206 An error occurred. The error number @var{nn} is given as hex digits.
36209 An empty reply indicates that @samp{QNonStop} is not supported by
36213 This packet is not probed by default; the remote stub must request it,
36214 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36215 Use of this packet is controlled by the @code{set non-stop} command;
36216 @pxref{Non-Stop Mode}.
36218 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36219 @itemx QCatchSyscalls:0
36220 @cindex catch syscalls from inferior, remote request
36221 @cindex @samp{QCatchSyscalls} packet
36222 @anchor{QCatchSyscalls}
36223 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36224 catching syscalls from the inferior process.
36226 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36227 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36228 is listed, every system call should be reported.
36230 Note that if a syscall not in the list is reported, @value{GDBN} will
36231 still filter the event according to its own list from all corresponding
36232 @code{catch syscall} commands. However, it is more efficient to only
36233 report the requested syscalls.
36235 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36236 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36238 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36239 kept for the new process too. On targets where exec may affect syscall
36240 numbers, for example with exec between 32 and 64-bit processes, the
36241 client should send a new packet with the new syscall list.
36246 The request succeeded.
36249 An error occurred. @var{nn} are hex digits.
36252 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36256 Use of this packet is controlled by the @code{set remote catch-syscalls}
36257 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36258 This packet is not probed by default; the remote stub must request it,
36259 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36261 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36262 @cindex pass signals to inferior, remote request
36263 @cindex @samp{QPassSignals} packet
36264 @anchor{QPassSignals}
36265 Each listed @var{signal} should be passed directly to the inferior process.
36266 Signals are numbered identically to continue packets and stop replies
36267 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36268 strictly greater than the previous item. These signals do not need to stop
36269 the inferior, or be reported to @value{GDBN}. All other signals should be
36270 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36271 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36272 new list. This packet improves performance when using @samp{handle
36273 @var{signal} nostop noprint pass}.
36278 The request succeeded.
36281 An error occurred. The error number @var{nn} is given as hex digits.
36284 An empty reply indicates that @samp{QPassSignals} is not supported by
36288 Use of this packet is controlled by the @code{set remote pass-signals}
36289 command (@pxref{Remote Configuration, set remote pass-signals}).
36290 This packet is not probed by default; the remote stub must request it,
36291 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36293 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36294 @cindex signals the inferior may see, remote request
36295 @cindex @samp{QProgramSignals} packet
36296 @anchor{QProgramSignals}
36297 Each listed @var{signal} may be delivered to the inferior process.
36298 Others should be silently discarded.
36300 In some cases, the remote stub may need to decide whether to deliver a
36301 signal to the program or not without @value{GDBN} involvement. One
36302 example of that is while detaching --- the program's threads may have
36303 stopped for signals that haven't yet had a chance of being reported to
36304 @value{GDBN}, and so the remote stub can use the signal list specified
36305 by this packet to know whether to deliver or ignore those pending
36308 This does not influence whether to deliver a signal as requested by a
36309 resumption packet (@pxref{vCont packet}).
36311 Signals are numbered identically to continue packets and stop replies
36312 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36313 strictly greater than the previous item. Multiple
36314 @samp{QProgramSignals} packets do not combine; any earlier
36315 @samp{QProgramSignals} list is completely replaced by the new list.
36320 The request succeeded.
36323 An error occurred. The error number @var{nn} is given as hex digits.
36326 An empty reply indicates that @samp{QProgramSignals} is not supported
36330 Use of this packet is controlled by the @code{set remote program-signals}
36331 command (@pxref{Remote Configuration, set remote program-signals}).
36332 This packet is not probed by default; the remote stub must request it,
36333 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36335 @anchor{QThreadEvents}
36336 @item QThreadEvents:1
36337 @itemx QThreadEvents:0
36338 @cindex thread create/exit events, remote request
36339 @cindex @samp{QThreadEvents} packet
36341 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36342 reporting of thread create and exit events. @xref{thread create
36343 event}, for the reply specifications. For example, this is used in
36344 non-stop mode when @value{GDBN} stops a set of threads and
36345 synchronously waits for the their corresponding stop replies. Without
36346 exit events, if one of the threads exits, @value{GDBN} would hang
36347 forever not knowing that it should no longer expect a stop for that
36348 same thread. @value{GDBN} does not enable this feature unless the
36349 stub reports that it supports it by including @samp{QThreadEvents+} in
36350 its @samp{qSupported} reply.
36355 The request succeeded.
36358 An error occurred. The error number @var{nn} is given as hex digits.
36361 An empty reply indicates that @samp{QThreadEvents} is not supported by
36365 Use of this packet is controlled by the @code{set remote thread-events}
36366 command (@pxref{Remote Configuration, set remote thread-events}).
36368 @item qRcmd,@var{command}
36369 @cindex execute remote command, remote request
36370 @cindex @samp{qRcmd} packet
36371 @var{command} (hex encoded) is passed to the local interpreter for
36372 execution. Invalid commands should be reported using the output
36373 string. Before the final result packet, the target may also respond
36374 with a number of intermediate @samp{O@var{output}} console output
36375 packets. @emph{Implementors should note that providing access to a
36376 stubs's interpreter may have security implications}.
36381 A command response with no output.
36383 A command response with the hex encoded output string @var{OUTPUT}.
36385 Indicate a badly formed request.
36387 An empty reply indicates that @samp{qRcmd} is not recognized.
36390 (Note that the @code{qRcmd} packet's name is separated from the
36391 command by a @samp{,}, not a @samp{:}, contrary to the naming
36392 conventions above. Please don't use this packet as a model for new
36395 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36396 @cindex searching memory, in remote debugging
36398 @cindex @samp{qSearch:memory} packet
36400 @cindex @samp{qSearch memory} packet
36401 @anchor{qSearch memory}
36402 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36403 Both @var{address} and @var{length} are encoded in hex;
36404 @var{search-pattern} is a sequence of bytes, also hex encoded.
36409 The pattern was not found.
36411 The pattern was found at @var{address}.
36413 A badly formed request or an error was encountered while searching memory.
36415 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36418 @item QStartNoAckMode
36419 @cindex @samp{QStartNoAckMode} packet
36420 @anchor{QStartNoAckMode}
36421 Request that the remote stub disable the normal @samp{+}/@samp{-}
36422 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36427 The stub has switched to no-acknowledgment mode.
36428 @value{GDBN} acknowledges this reponse,
36429 but neither the stub nor @value{GDBN} shall send or expect further
36430 @samp{+}/@samp{-} acknowledgments in the current connection.
36432 An empty reply indicates that the stub does not support no-acknowledgment mode.
36435 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36436 @cindex supported packets, remote query
36437 @cindex features of the remote protocol
36438 @cindex @samp{qSupported} packet
36439 @anchor{qSupported}
36440 Tell the remote stub about features supported by @value{GDBN}, and
36441 query the stub for features it supports. This packet allows
36442 @value{GDBN} and the remote stub to take advantage of each others'
36443 features. @samp{qSupported} also consolidates multiple feature probes
36444 at startup, to improve @value{GDBN} performance---a single larger
36445 packet performs better than multiple smaller probe packets on
36446 high-latency links. Some features may enable behavior which must not
36447 be on by default, e.g.@: because it would confuse older clients or
36448 stubs. Other features may describe packets which could be
36449 automatically probed for, but are not. These features must be
36450 reported before @value{GDBN} will use them. This ``default
36451 unsupported'' behavior is not appropriate for all packets, but it
36452 helps to keep the initial connection time under control with new
36453 versions of @value{GDBN} which support increasing numbers of packets.
36457 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36458 The stub supports or does not support each returned @var{stubfeature},
36459 depending on the form of each @var{stubfeature} (see below for the
36462 An empty reply indicates that @samp{qSupported} is not recognized,
36463 or that no features needed to be reported to @value{GDBN}.
36466 The allowed forms for each feature (either a @var{gdbfeature} in the
36467 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36471 @item @var{name}=@var{value}
36472 The remote protocol feature @var{name} is supported, and associated
36473 with the specified @var{value}. The format of @var{value} depends
36474 on the feature, but it must not include a semicolon.
36476 The remote protocol feature @var{name} is supported, and does not
36477 need an associated value.
36479 The remote protocol feature @var{name} is not supported.
36481 The remote protocol feature @var{name} may be supported, and
36482 @value{GDBN} should auto-detect support in some other way when it is
36483 needed. This form will not be used for @var{gdbfeature} notifications,
36484 but may be used for @var{stubfeature} responses.
36487 Whenever the stub receives a @samp{qSupported} request, the
36488 supplied set of @value{GDBN} features should override any previous
36489 request. This allows @value{GDBN} to put the stub in a known
36490 state, even if the stub had previously been communicating with
36491 a different version of @value{GDBN}.
36493 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36498 This feature indicates whether @value{GDBN} supports multiprocess
36499 extensions to the remote protocol. @value{GDBN} does not use such
36500 extensions unless the stub also reports that it supports them by
36501 including @samp{multiprocess+} in its @samp{qSupported} reply.
36502 @xref{multiprocess extensions}, for details.
36505 This feature indicates that @value{GDBN} supports the XML target
36506 description. If the stub sees @samp{xmlRegisters=} with target
36507 specific strings separated by a comma, it will report register
36511 This feature indicates whether @value{GDBN} supports the
36512 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36513 instruction reply packet}).
36516 This feature indicates whether @value{GDBN} supports the swbreak stop
36517 reason in stop replies. @xref{swbreak stop reason}, for details.
36520 This feature indicates whether @value{GDBN} supports the hwbreak stop
36521 reason in stop replies. @xref{swbreak stop reason}, for details.
36524 This feature indicates whether @value{GDBN} supports fork event
36525 extensions to the remote protocol. @value{GDBN} does not use such
36526 extensions unless the stub also reports that it supports them by
36527 including @samp{fork-events+} in its @samp{qSupported} reply.
36530 This feature indicates whether @value{GDBN} supports vfork event
36531 extensions to the remote protocol. @value{GDBN} does not use such
36532 extensions unless the stub also reports that it supports them by
36533 including @samp{vfork-events+} in its @samp{qSupported} reply.
36536 This feature indicates whether @value{GDBN} supports exec event
36537 extensions to the remote protocol. @value{GDBN} does not use such
36538 extensions unless the stub also reports that it supports them by
36539 including @samp{exec-events+} in its @samp{qSupported} reply.
36541 @item vContSupported
36542 This feature indicates whether @value{GDBN} wants to know the
36543 supported actions in the reply to @samp{vCont?} packet.
36546 Stubs should ignore any unknown values for
36547 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36548 packet supports receiving packets of unlimited length (earlier
36549 versions of @value{GDBN} may reject overly long responses). Additional values
36550 for @var{gdbfeature} may be defined in the future to let the stub take
36551 advantage of new features in @value{GDBN}, e.g.@: incompatible
36552 improvements in the remote protocol---the @samp{multiprocess} feature is
36553 an example of such a feature. The stub's reply should be independent
36554 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36555 describes all the features it supports, and then the stub replies with
36556 all the features it supports.
36558 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36559 responses, as long as each response uses one of the standard forms.
36561 Some features are flags. A stub which supports a flag feature
36562 should respond with a @samp{+} form response. Other features
36563 require values, and the stub should respond with an @samp{=}
36566 Each feature has a default value, which @value{GDBN} will use if
36567 @samp{qSupported} is not available or if the feature is not mentioned
36568 in the @samp{qSupported} response. The default values are fixed; a
36569 stub is free to omit any feature responses that match the defaults.
36571 Not all features can be probed, but for those which can, the probing
36572 mechanism is useful: in some cases, a stub's internal
36573 architecture may not allow the protocol layer to know some information
36574 about the underlying target in advance. This is especially common in
36575 stubs which may be configured for multiple targets.
36577 These are the currently defined stub features and their properties:
36579 @multitable @columnfractions 0.35 0.2 0.12 0.2
36580 @c NOTE: The first row should be @headitem, but we do not yet require
36581 @c a new enough version of Texinfo (4.7) to use @headitem.
36583 @tab Value Required
36587 @item @samp{PacketSize}
36592 @item @samp{qXfer:auxv:read}
36597 @item @samp{qXfer:btrace:read}
36602 @item @samp{qXfer:btrace-conf:read}
36607 @item @samp{qXfer:exec-file:read}
36612 @item @samp{qXfer:features:read}
36617 @item @samp{qXfer:libraries:read}
36622 @item @samp{qXfer:libraries-svr4:read}
36627 @item @samp{augmented-libraries-svr4-read}
36632 @item @samp{qXfer:memory-map:read}
36637 @item @samp{qXfer:sdata:read}
36642 @item @samp{qXfer:spu:read}
36647 @item @samp{qXfer:spu:write}
36652 @item @samp{qXfer:siginfo:read}
36657 @item @samp{qXfer:siginfo:write}
36662 @item @samp{qXfer:threads:read}
36667 @item @samp{qXfer:traceframe-info:read}
36672 @item @samp{qXfer:uib:read}
36677 @item @samp{qXfer:fdpic:read}
36682 @item @samp{Qbtrace:off}
36687 @item @samp{Qbtrace:bts}
36692 @item @samp{Qbtrace:pt}
36697 @item @samp{Qbtrace-conf:bts:size}
36702 @item @samp{Qbtrace-conf:pt:size}
36707 @item @samp{QNonStop}
36712 @item @samp{QCatchSyscalls}
36717 @item @samp{QPassSignals}
36722 @item @samp{QStartNoAckMode}
36727 @item @samp{multiprocess}
36732 @item @samp{ConditionalBreakpoints}
36737 @item @samp{ConditionalTracepoints}
36742 @item @samp{ReverseContinue}
36747 @item @samp{ReverseStep}
36752 @item @samp{TracepointSource}
36757 @item @samp{QAgent}
36762 @item @samp{QAllow}
36767 @item @samp{QDisableRandomization}
36772 @item @samp{EnableDisableTracepoints}
36777 @item @samp{QTBuffer:size}
36782 @item @samp{tracenz}
36787 @item @samp{BreakpointCommands}
36792 @item @samp{swbreak}
36797 @item @samp{hwbreak}
36802 @item @samp{fork-events}
36807 @item @samp{vfork-events}
36812 @item @samp{exec-events}
36817 @item @samp{QThreadEvents}
36822 @item @samp{no-resumed}
36829 These are the currently defined stub features, in more detail:
36832 @cindex packet size, remote protocol
36833 @item PacketSize=@var{bytes}
36834 The remote stub can accept packets up to at least @var{bytes} in
36835 length. @value{GDBN} will send packets up to this size for bulk
36836 transfers, and will never send larger packets. This is a limit on the
36837 data characters in the packet, including the frame and checksum.
36838 There is no trailing NUL byte in a remote protocol packet; if the stub
36839 stores packets in a NUL-terminated format, it should allow an extra
36840 byte in its buffer for the NUL. If this stub feature is not supported,
36841 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36843 @item qXfer:auxv:read
36844 The remote stub understands the @samp{qXfer:auxv:read} packet
36845 (@pxref{qXfer auxiliary vector read}).
36847 @item qXfer:btrace:read
36848 The remote stub understands the @samp{qXfer:btrace:read}
36849 packet (@pxref{qXfer btrace read}).
36851 @item qXfer:btrace-conf:read
36852 The remote stub understands the @samp{qXfer:btrace-conf:read}
36853 packet (@pxref{qXfer btrace-conf read}).
36855 @item qXfer:exec-file:read
36856 The remote stub understands the @samp{qXfer:exec-file:read} packet
36857 (@pxref{qXfer executable filename read}).
36859 @item qXfer:features:read
36860 The remote stub understands the @samp{qXfer:features:read} packet
36861 (@pxref{qXfer target description read}).
36863 @item qXfer:libraries:read
36864 The remote stub understands the @samp{qXfer:libraries:read} packet
36865 (@pxref{qXfer library list read}).
36867 @item qXfer:libraries-svr4:read
36868 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36869 (@pxref{qXfer svr4 library list read}).
36871 @item augmented-libraries-svr4-read
36872 The remote stub understands the augmented form of the
36873 @samp{qXfer:libraries-svr4:read} packet
36874 (@pxref{qXfer svr4 library list read}).
36876 @item qXfer:memory-map:read
36877 The remote stub understands the @samp{qXfer:memory-map:read} packet
36878 (@pxref{qXfer memory map read}).
36880 @item qXfer:sdata:read
36881 The remote stub understands the @samp{qXfer:sdata:read} packet
36882 (@pxref{qXfer sdata read}).
36884 @item qXfer:spu:read
36885 The remote stub understands the @samp{qXfer:spu:read} packet
36886 (@pxref{qXfer spu read}).
36888 @item qXfer:spu:write
36889 The remote stub understands the @samp{qXfer:spu:write} packet
36890 (@pxref{qXfer spu write}).
36892 @item qXfer:siginfo:read
36893 The remote stub understands the @samp{qXfer:siginfo:read} packet
36894 (@pxref{qXfer siginfo read}).
36896 @item qXfer:siginfo:write
36897 The remote stub understands the @samp{qXfer:siginfo:write} packet
36898 (@pxref{qXfer siginfo write}).
36900 @item qXfer:threads:read
36901 The remote stub understands the @samp{qXfer:threads:read} packet
36902 (@pxref{qXfer threads read}).
36904 @item qXfer:traceframe-info:read
36905 The remote stub understands the @samp{qXfer:traceframe-info:read}
36906 packet (@pxref{qXfer traceframe info read}).
36908 @item qXfer:uib:read
36909 The remote stub understands the @samp{qXfer:uib:read}
36910 packet (@pxref{qXfer unwind info block}).
36912 @item qXfer:fdpic:read
36913 The remote stub understands the @samp{qXfer:fdpic:read}
36914 packet (@pxref{qXfer fdpic loadmap read}).
36917 The remote stub understands the @samp{QNonStop} packet
36918 (@pxref{QNonStop}).
36920 @item QCatchSyscalls
36921 The remote stub understands the @samp{QCatchSyscalls} packet
36922 (@pxref{QCatchSyscalls}).
36925 The remote stub understands the @samp{QPassSignals} packet
36926 (@pxref{QPassSignals}).
36928 @item QStartNoAckMode
36929 The remote stub understands the @samp{QStartNoAckMode} packet and
36930 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36933 @anchor{multiprocess extensions}
36934 @cindex multiprocess extensions, in remote protocol
36935 The remote stub understands the multiprocess extensions to the remote
36936 protocol syntax. The multiprocess extensions affect the syntax of
36937 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36938 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36939 replies. Note that reporting this feature indicates support for the
36940 syntactic extensions only, not that the stub necessarily supports
36941 debugging of more than one process at a time. The stub must not use
36942 multiprocess extensions in packet replies unless @value{GDBN} has also
36943 indicated it supports them in its @samp{qSupported} request.
36945 @item qXfer:osdata:read
36946 The remote stub understands the @samp{qXfer:osdata:read} packet
36947 ((@pxref{qXfer osdata read}).
36949 @item ConditionalBreakpoints
36950 The target accepts and implements evaluation of conditional expressions
36951 defined for breakpoints. The target will only report breakpoint triggers
36952 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36954 @item ConditionalTracepoints
36955 The remote stub accepts and implements conditional expressions defined
36956 for tracepoints (@pxref{Tracepoint Conditions}).
36958 @item ReverseContinue
36959 The remote stub accepts and implements the reverse continue packet
36963 The remote stub accepts and implements the reverse step packet
36966 @item TracepointSource
36967 The remote stub understands the @samp{QTDPsrc} packet that supplies
36968 the source form of tracepoint definitions.
36971 The remote stub understands the @samp{QAgent} packet.
36974 The remote stub understands the @samp{QAllow} packet.
36976 @item QDisableRandomization
36977 The remote stub understands the @samp{QDisableRandomization} packet.
36979 @item StaticTracepoint
36980 @cindex static tracepoints, in remote protocol
36981 The remote stub supports static tracepoints.
36983 @item InstallInTrace
36984 @anchor{install tracepoint in tracing}
36985 The remote stub supports installing tracepoint in tracing.
36987 @item EnableDisableTracepoints
36988 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36989 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36990 to be enabled and disabled while a trace experiment is running.
36992 @item QTBuffer:size
36993 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36994 packet that allows to change the size of the trace buffer.
36997 @cindex string tracing, in remote protocol
36998 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36999 See @ref{Bytecode Descriptions} for details about the bytecode.
37001 @item BreakpointCommands
37002 @cindex breakpoint commands, in remote protocol
37003 The remote stub supports running a breakpoint's command list itself,
37004 rather than reporting the hit to @value{GDBN}.
37007 The remote stub understands the @samp{Qbtrace:off} packet.
37010 The remote stub understands the @samp{Qbtrace:bts} packet.
37013 The remote stub understands the @samp{Qbtrace:pt} packet.
37015 @item Qbtrace-conf:bts:size
37016 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37018 @item Qbtrace-conf:pt:size
37019 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37022 The remote stub reports the @samp{swbreak} stop reason for memory
37026 The remote stub reports the @samp{hwbreak} stop reason for hardware
37030 The remote stub reports the @samp{fork} stop reason for fork events.
37033 The remote stub reports the @samp{vfork} stop reason for vfork events
37034 and vforkdone events.
37037 The remote stub reports the @samp{exec} stop reason for exec events.
37039 @item vContSupported
37040 The remote stub reports the supported actions in the reply to
37041 @samp{vCont?} packet.
37043 @item QThreadEvents
37044 The remote stub understands the @samp{QThreadEvents} packet.
37047 The remote stub reports the @samp{N} stop reply.
37052 @cindex symbol lookup, remote request
37053 @cindex @samp{qSymbol} packet
37054 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37055 requests. Accept requests from the target for the values of symbols.
37060 The target does not need to look up any (more) symbols.
37061 @item qSymbol:@var{sym_name}
37062 The target requests the value of symbol @var{sym_name} (hex encoded).
37063 @value{GDBN} may provide the value by using the
37064 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37068 @item qSymbol:@var{sym_value}:@var{sym_name}
37069 Set the value of @var{sym_name} to @var{sym_value}.
37071 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37072 target has previously requested.
37074 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37075 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37081 The target does not need to look up any (more) symbols.
37082 @item qSymbol:@var{sym_name}
37083 The target requests the value of a new symbol @var{sym_name} (hex
37084 encoded). @value{GDBN} will continue to supply the values of symbols
37085 (if available), until the target ceases to request them.
37090 @itemx QTDisconnected
37097 @itemx qTMinFTPILen
37099 @xref{Tracepoint Packets}.
37101 @item qThreadExtraInfo,@var{thread-id}
37102 @cindex thread attributes info, remote request
37103 @cindex @samp{qThreadExtraInfo} packet
37104 Obtain from the target OS a printable string description of thread
37105 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37106 for the forms of @var{thread-id}. This
37107 string may contain anything that the target OS thinks is interesting
37108 for @value{GDBN} to tell the user about the thread. The string is
37109 displayed in @value{GDBN}'s @code{info threads} display. Some
37110 examples of possible thread extra info strings are @samp{Runnable}, or
37111 @samp{Blocked on Mutex}.
37115 @item @var{XX}@dots{}
37116 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37117 comprising the printable string containing the extra information about
37118 the thread's attributes.
37121 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37122 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37123 conventions above. Please don't use this packet as a model for new
37142 @xref{Tracepoint Packets}.
37144 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37145 @cindex read special object, remote request
37146 @cindex @samp{qXfer} packet
37147 @anchor{qXfer read}
37148 Read uninterpreted bytes from the target's special data area
37149 identified by the keyword @var{object}. Request @var{length} bytes
37150 starting at @var{offset} bytes into the data. The content and
37151 encoding of @var{annex} is specific to @var{object}; it can supply
37152 additional details about what data to access.
37154 Here are the specific requests of this form defined so far. All
37155 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37156 formats, listed below.
37159 @item qXfer:auxv:read::@var{offset},@var{length}
37160 @anchor{qXfer auxiliary vector read}
37161 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37162 auxiliary vector}. Note @var{annex} must be empty.
37164 This packet is not probed by default; the remote stub must request it,
37165 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37167 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37168 @anchor{qXfer btrace read}
37170 Return a description of the current branch trace.
37171 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37172 packet may have one of the following values:
37176 Returns all available branch trace.
37179 Returns all available branch trace if the branch trace changed since
37180 the last read request.
37183 Returns the new branch trace since the last read request. Adds a new
37184 block to the end of the trace that begins at zero and ends at the source
37185 location of the first branch in the trace buffer. This extra block is
37186 used to stitch traces together.
37188 If the trace buffer overflowed, returns an error indicating the overflow.
37191 This packet is not probed by default; the remote stub must request it
37192 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37194 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37195 @anchor{qXfer btrace-conf read}
37197 Return a description of the current branch trace configuration.
37198 @xref{Branch Trace Configuration Format}.
37200 This packet is not probed by default; the remote stub must request it
37201 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37203 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37204 @anchor{qXfer executable filename read}
37205 Return the full absolute name of the file that was executed to create
37206 a process running on the remote system. The annex specifies the
37207 numeric process ID of the process to query, encoded as a hexadecimal
37208 number. If the annex part is empty the remote stub should return the
37209 filename corresponding to the currently executing process.
37211 This packet is not probed by default; the remote stub must request it,
37212 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37214 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37215 @anchor{qXfer target description read}
37216 Access the @dfn{target description}. @xref{Target Descriptions}. The
37217 annex specifies which XML document to access. The main description is
37218 always loaded from the @samp{target.xml} annex.
37220 This packet is not probed by default; the remote stub must request it,
37221 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37223 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37224 @anchor{qXfer library list read}
37225 Access the target's list of loaded libraries. @xref{Library List Format}.
37226 The annex part of the generic @samp{qXfer} packet must be empty
37227 (@pxref{qXfer read}).
37229 Targets which maintain a list of libraries in the program's memory do
37230 not need to implement this packet; it is designed for platforms where
37231 the operating system manages the list of loaded libraries.
37233 This packet is not probed by default; the remote stub must request it,
37234 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37236 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37237 @anchor{qXfer svr4 library list read}
37238 Access the target's list of loaded libraries when the target is an SVR4
37239 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37240 of the generic @samp{qXfer} packet must be empty unless the remote
37241 stub indicated it supports the augmented form of this packet
37242 by supplying an appropriate @samp{qSupported} response
37243 (@pxref{qXfer read}, @ref{qSupported}).
37245 This packet is optional for better performance on SVR4 targets.
37246 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37248 This packet is not probed by default; the remote stub must request it,
37249 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37251 If the remote stub indicates it supports the augmented form of this
37252 packet then the annex part of the generic @samp{qXfer} packet may
37253 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37254 arguments. The currently supported arguments are:
37257 @item start=@var{address}
37258 A hexadecimal number specifying the address of the @samp{struct
37259 link_map} to start reading the library list from. If unset or zero
37260 then the first @samp{struct link_map} in the library list will be
37261 chosen as the starting point.
37263 @item prev=@var{address}
37264 A hexadecimal number specifying the address of the @samp{struct
37265 link_map} immediately preceding the @samp{struct link_map}
37266 specified by the @samp{start} argument. If unset or zero then
37267 the remote stub will expect that no @samp{struct link_map}
37268 exists prior to the starting point.
37272 Arguments that are not understood by the remote stub will be silently
37275 @item qXfer:memory-map:read::@var{offset},@var{length}
37276 @anchor{qXfer memory map read}
37277 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37278 annex part of the generic @samp{qXfer} packet must be empty
37279 (@pxref{qXfer read}).
37281 This packet is not probed by default; the remote stub must request it,
37282 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37284 @item qXfer:sdata:read::@var{offset},@var{length}
37285 @anchor{qXfer sdata read}
37287 Read contents of the extra collected static tracepoint marker
37288 information. The annex part of the generic @samp{qXfer} packet must
37289 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37292 This packet is not probed by default; the remote stub must request it,
37293 by supplying an appropriate @samp{qSupported} response
37294 (@pxref{qSupported}).
37296 @item qXfer:siginfo:read::@var{offset},@var{length}
37297 @anchor{qXfer siginfo read}
37298 Read contents of the extra signal information on the target
37299 system. The annex part of the generic @samp{qXfer} packet must be
37300 empty (@pxref{qXfer read}).
37302 This packet is not probed by default; the remote stub must request it,
37303 by supplying an appropriate @samp{qSupported} response
37304 (@pxref{qSupported}).
37306 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37307 @anchor{qXfer spu read}
37308 Read contents of an @code{spufs} file on the target system. The
37309 annex specifies which file to read; it must be of the form
37310 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37311 in the target process, and @var{name} identifes the @code{spufs} file
37312 in that context to be accessed.
37314 This packet is not probed by default; the remote stub must request it,
37315 by supplying an appropriate @samp{qSupported} response
37316 (@pxref{qSupported}).
37318 @item qXfer:threads:read::@var{offset},@var{length}
37319 @anchor{qXfer threads read}
37320 Access the list of threads on target. @xref{Thread List Format}. The
37321 annex part of the generic @samp{qXfer} packet must be empty
37322 (@pxref{qXfer read}).
37324 This packet is not probed by default; the remote stub must request it,
37325 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37327 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37328 @anchor{qXfer traceframe info read}
37330 Return a description of the current traceframe's contents.
37331 @xref{Traceframe Info Format}. The annex part of the generic
37332 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
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 qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37338 @anchor{qXfer unwind info block}
37340 Return the unwind information block for @var{pc}. This packet is used
37341 on OpenVMS/ia64 to ask the kernel unwind information.
37343 This packet is not probed by default.
37345 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37346 @anchor{qXfer fdpic loadmap read}
37347 Read contents of @code{loadmap}s on the target system. The
37348 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37349 executable @code{loadmap} or interpreter @code{loadmap} to read.
37351 This packet is not probed by default; the remote stub must request it,
37352 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37354 @item qXfer:osdata:read::@var{offset},@var{length}
37355 @anchor{qXfer osdata read}
37356 Access the target's @dfn{operating system information}.
37357 @xref{Operating System Information}.
37364 Data @var{data} (@pxref{Binary Data}) has been read from the
37365 target. There may be more data at a higher address (although
37366 it is permitted to return @samp{m} even for the last valid
37367 block of data, as long as at least one byte of data was read).
37368 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37372 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37373 There is no more data to be read. It is possible for @var{data} to
37374 have fewer bytes than the @var{length} in the request.
37377 The @var{offset} in the request is at the end of the data.
37378 There is no more data to be read.
37381 The request was malformed, or @var{annex} was invalid.
37384 The offset was invalid, or there was an error encountered reading the data.
37385 The @var{nn} part is a hex-encoded @code{errno} value.
37388 An empty reply indicates the @var{object} string was not recognized by
37389 the stub, or that the object does not support reading.
37392 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37393 @cindex write data into object, remote request
37394 @anchor{qXfer write}
37395 Write uninterpreted bytes into the target's special data area
37396 identified by the keyword @var{object}, starting at @var{offset} bytes
37397 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37398 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37399 is specific to @var{object}; it can supply additional details about what data
37402 Here are the specific requests of this form defined so far. All
37403 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37404 formats, listed below.
37407 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37408 @anchor{qXfer siginfo write}
37409 Write @var{data} to the extra signal information on the target system.
37410 The annex part of the generic @samp{qXfer} packet must be
37411 empty (@pxref{qXfer write}).
37413 This packet is not probed by default; the remote stub must request it,
37414 by supplying an appropriate @samp{qSupported} response
37415 (@pxref{qSupported}).
37417 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37418 @anchor{qXfer spu write}
37419 Write @var{data} to an @code{spufs} file on the target system. The
37420 annex specifies which file to write; it must be of the form
37421 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37422 in the target process, and @var{name} identifes the @code{spufs} file
37423 in that context to be accessed.
37425 This packet is not probed by default; the remote stub must request it,
37426 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37432 @var{nn} (hex encoded) is the number of bytes written.
37433 This may be fewer bytes than supplied in the request.
37436 The request was malformed, or @var{annex} was invalid.
37439 The offset was invalid, or there was an error encountered writing the data.
37440 The @var{nn} part is a hex-encoded @code{errno} value.
37443 An empty reply indicates the @var{object} string was not
37444 recognized by the stub, or that the object does not support writing.
37447 @item qXfer:@var{object}:@var{operation}:@dots{}
37448 Requests of this form may be added in the future. When a stub does
37449 not recognize the @var{object} keyword, or its support for
37450 @var{object} does not recognize the @var{operation} keyword, the stub
37451 must respond with an empty packet.
37453 @item qAttached:@var{pid}
37454 @cindex query attached, remote request
37455 @cindex @samp{qAttached} packet
37456 Return an indication of whether the remote server attached to an
37457 existing process or created a new process. When the multiprocess
37458 protocol extensions are supported (@pxref{multiprocess extensions}),
37459 @var{pid} is an integer in hexadecimal format identifying the target
37460 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37461 the query packet will be simplified as @samp{qAttached}.
37463 This query is used, for example, to know whether the remote process
37464 should be detached or killed when a @value{GDBN} session is ended with
37465 the @code{quit} command.
37470 The remote server attached to an existing process.
37472 The remote server created a new process.
37474 A badly formed request or an error was encountered.
37478 Enable branch tracing for the current thread using Branch Trace Store.
37483 Branch tracing has been enabled.
37485 A badly formed request or an error was encountered.
37489 Enable branch tracing for the current thread using Intel Processor Trace.
37494 Branch tracing has been enabled.
37496 A badly formed request or an error was encountered.
37500 Disable branch tracing for the current thread.
37505 Branch tracing has been disabled.
37507 A badly formed request or an error was encountered.
37510 @item Qbtrace-conf:bts:size=@var{value}
37511 Set the requested ring buffer size for new threads that use the
37512 btrace recording method in bts format.
37517 The ring buffer size has been set.
37519 A badly formed request or an error was encountered.
37522 @item Qbtrace-conf:pt:size=@var{value}
37523 Set the requested ring buffer size for new threads that use the
37524 btrace recording method in pt format.
37529 The ring buffer size has been set.
37531 A badly formed request or an error was encountered.
37536 @node Architecture-Specific Protocol Details
37537 @section Architecture-Specific Protocol Details
37539 This section describes how the remote protocol is applied to specific
37540 target architectures. Also see @ref{Standard Target Features}, for
37541 details of XML target descriptions for each architecture.
37544 * ARM-Specific Protocol Details::
37545 * MIPS-Specific Protocol Details::
37548 @node ARM-Specific Protocol Details
37549 @subsection @acronym{ARM}-specific Protocol Details
37552 * ARM Breakpoint Kinds::
37555 @node ARM Breakpoint Kinds
37556 @subsubsection @acronym{ARM} Breakpoint Kinds
37557 @cindex breakpoint kinds, @acronym{ARM}
37559 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37564 16-bit Thumb mode breakpoint.
37567 32-bit Thumb mode (Thumb-2) breakpoint.
37570 32-bit @acronym{ARM} mode breakpoint.
37574 @node MIPS-Specific Protocol Details
37575 @subsection @acronym{MIPS}-specific Protocol Details
37578 * MIPS Register packet Format::
37579 * MIPS Breakpoint Kinds::
37582 @node MIPS Register packet Format
37583 @subsubsection @acronym{MIPS} Register Packet Format
37584 @cindex register packet format, @acronym{MIPS}
37586 The following @code{g}/@code{G} packets have previously been defined.
37587 In the below, some thirty-two bit registers are transferred as
37588 sixty-four bits. Those registers should be zero/sign extended (which?)
37589 to fill the space allocated. Register bytes are transferred in target
37590 byte order. The two nibbles within a register byte are transferred
37591 most-significant -- least-significant.
37596 All registers are transferred as thirty-two bit quantities in the order:
37597 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37598 registers; fsr; fir; fp.
37601 All registers are transferred as sixty-four bit quantities (including
37602 thirty-two bit registers such as @code{sr}). The ordering is the same
37607 @node MIPS Breakpoint Kinds
37608 @subsubsection @acronym{MIPS} Breakpoint Kinds
37609 @cindex breakpoint kinds, @acronym{MIPS}
37611 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37616 16-bit @acronym{MIPS16} mode breakpoint.
37619 16-bit @acronym{microMIPS} mode breakpoint.
37622 32-bit standard @acronym{MIPS} mode breakpoint.
37625 32-bit @acronym{microMIPS} mode breakpoint.
37629 @node Tracepoint Packets
37630 @section Tracepoint Packets
37631 @cindex tracepoint packets
37632 @cindex packets, tracepoint
37634 Here we describe the packets @value{GDBN} uses to implement
37635 tracepoints (@pxref{Tracepoints}).
37639 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37640 @cindex @samp{QTDP} packet
37641 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37642 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37643 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37644 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37645 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37646 the number of bytes that the target should copy elsewhere to make room
37647 for the tracepoint. If an @samp{X} is present, it introduces a
37648 tracepoint condition, which consists of a hexadecimal length, followed
37649 by a comma and hex-encoded bytes, in a manner similar to action
37650 encodings as described below. If the trailing @samp{-} is present,
37651 further @samp{QTDP} packets will follow to specify this tracepoint's
37657 The packet was understood and carried out.
37659 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37661 The packet was not recognized.
37664 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37665 Define actions to be taken when a tracepoint is hit. The @var{n} and
37666 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37667 this tracepoint. This packet may only be sent immediately after
37668 another @samp{QTDP} packet that ended with a @samp{-}. If the
37669 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37670 specifying more actions for this tracepoint.
37672 In the series of action packets for a given tracepoint, at most one
37673 can have an @samp{S} before its first @var{action}. If such a packet
37674 is sent, it and the following packets define ``while-stepping''
37675 actions. Any prior packets define ordinary actions --- that is, those
37676 taken when the tracepoint is first hit. If no action packet has an
37677 @samp{S}, then all the packets in the series specify ordinary
37678 tracepoint actions.
37680 The @samp{@var{action}@dots{}} portion of the packet is a series of
37681 actions, concatenated without separators. Each action has one of the
37687 Collect the registers whose bits are set in @var{mask},
37688 a hexadecimal number whose @var{i}'th bit is set if register number
37689 @var{i} should be collected. (The least significant bit is numbered
37690 zero.) Note that @var{mask} may be any number of digits long; it may
37691 not fit in a 32-bit word.
37693 @item M @var{basereg},@var{offset},@var{len}
37694 Collect @var{len} bytes of memory starting at the address in register
37695 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37696 @samp{-1}, then the range has a fixed address: @var{offset} is the
37697 address of the lowest byte to collect. The @var{basereg},
37698 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37699 values (the @samp{-1} value for @var{basereg} is a special case).
37701 @item X @var{len},@var{expr}
37702 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37703 it directs. The agent expression @var{expr} is as described in
37704 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37705 two-digit hex number in the packet; @var{len} is the number of bytes
37706 in the expression (and thus one-half the number of hex digits in the
37711 Any number of actions may be packed together in a single @samp{QTDP}
37712 packet, as long as the packet does not exceed the maximum packet
37713 length (400 bytes, for many stubs). There may be only one @samp{R}
37714 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37715 actions. Any registers referred to by @samp{M} and @samp{X} actions
37716 must be collected by a preceding @samp{R} action. (The
37717 ``while-stepping'' actions are treated as if they were attached to a
37718 separate tracepoint, as far as these restrictions are concerned.)
37723 The packet was understood and carried out.
37725 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37727 The packet was not recognized.
37730 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37731 @cindex @samp{QTDPsrc} packet
37732 Specify a source string of tracepoint @var{n} at address @var{addr}.
37733 This is useful to get accurate reproduction of the tracepoints
37734 originally downloaded at the beginning of the trace run. The @var{type}
37735 is the name of the tracepoint part, such as @samp{cond} for the
37736 tracepoint's conditional expression (see below for a list of types), while
37737 @var{bytes} is the string, encoded in hexadecimal.
37739 @var{start} is the offset of the @var{bytes} within the overall source
37740 string, while @var{slen} is the total length of the source string.
37741 This is intended for handling source strings that are longer than will
37742 fit in a single packet.
37743 @c Add detailed example when this info is moved into a dedicated
37744 @c tracepoint descriptions section.
37746 The available string types are @samp{at} for the location,
37747 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37748 @value{GDBN} sends a separate packet for each command in the action
37749 list, in the same order in which the commands are stored in the list.
37751 The target does not need to do anything with source strings except
37752 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37755 Although this packet is optional, and @value{GDBN} will only send it
37756 if the target replies with @samp{TracepointSource} @xref{General
37757 Query Packets}, it makes both disconnected tracing and trace files
37758 much easier to use. Otherwise the user must be careful that the
37759 tracepoints in effect while looking at trace frames are identical to
37760 the ones in effect during the trace run; even a small discrepancy
37761 could cause @samp{tdump} not to work, or a particular trace frame not
37764 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37765 @cindex define trace state variable, remote request
37766 @cindex @samp{QTDV} packet
37767 Create a new trace state variable, number @var{n}, with an initial
37768 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37769 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37770 the option of not using this packet for initial values of zero; the
37771 target should simply create the trace state variables as they are
37772 mentioned in expressions. The value @var{builtin} should be 1 (one)
37773 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37774 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37775 @samp{qTsV} packet had it set. The contents of @var{name} is the
37776 hex-encoded name (without the leading @samp{$}) of the trace state
37779 @item QTFrame:@var{n}
37780 @cindex @samp{QTFrame} packet
37781 Select the @var{n}'th tracepoint frame from the buffer, and use the
37782 register and memory contents recorded there to answer subsequent
37783 request packets from @value{GDBN}.
37785 A successful reply from the stub indicates that the stub has found the
37786 requested frame. The response is a series of parts, concatenated
37787 without separators, describing the frame we selected. Each part has
37788 one of the following forms:
37792 The selected frame is number @var{n} in the trace frame buffer;
37793 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37794 was no frame matching the criteria in the request packet.
37797 The selected trace frame records a hit of tracepoint number @var{t};
37798 @var{t} is a hexadecimal number.
37802 @item QTFrame:pc:@var{addr}
37803 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37804 currently selected frame whose PC is @var{addr};
37805 @var{addr} is a hexadecimal number.
37807 @item QTFrame:tdp:@var{t}
37808 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37809 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37810 is a hexadecimal number.
37812 @item QTFrame:range:@var{start}:@var{end}
37813 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37814 currently selected frame whose PC is between @var{start} (inclusive)
37815 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37818 @item QTFrame:outside:@var{start}:@var{end}
37819 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37820 frame @emph{outside} the given range of addresses (exclusive).
37823 @cindex @samp{qTMinFTPILen} packet
37824 This packet requests the minimum length of instruction at which a fast
37825 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37826 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37827 it depends on the target system being able to create trampolines in
37828 the first 64K of memory, which might or might not be possible for that
37829 system. So the reply to this packet will be 4 if it is able to
37836 The minimum instruction length is currently unknown.
37838 The minimum instruction length is @var{length}, where @var{length}
37839 is a hexadecimal number greater or equal to 1. A reply
37840 of 1 means that a fast tracepoint may be placed on any instruction
37841 regardless of size.
37843 An error has occurred.
37845 An empty reply indicates that the request is not supported by the stub.
37849 @cindex @samp{QTStart} packet
37850 Begin the tracepoint experiment. Begin collecting data from
37851 tracepoint hits in the trace frame buffer. This packet supports the
37852 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37853 instruction reply packet}).
37856 @cindex @samp{QTStop} packet
37857 End the tracepoint experiment. Stop collecting trace frames.
37859 @item QTEnable:@var{n}:@var{addr}
37861 @cindex @samp{QTEnable} packet
37862 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37863 experiment. If the tracepoint was previously disabled, then collection
37864 of data from it will resume.
37866 @item QTDisable:@var{n}:@var{addr}
37868 @cindex @samp{QTDisable} packet
37869 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37870 experiment. No more data will be collected from the tracepoint unless
37871 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37874 @cindex @samp{QTinit} packet
37875 Clear the table of tracepoints, and empty the trace frame buffer.
37877 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37878 @cindex @samp{QTro} packet
37879 Establish the given ranges of memory as ``transparent''. The stub
37880 will answer requests for these ranges from memory's current contents,
37881 if they were not collected as part of the tracepoint hit.
37883 @value{GDBN} uses this to mark read-only regions of memory, like those
37884 containing program code. Since these areas never change, they should
37885 still have the same contents they did when the tracepoint was hit, so
37886 there's no reason for the stub to refuse to provide their contents.
37888 @item QTDisconnected:@var{value}
37889 @cindex @samp{QTDisconnected} packet
37890 Set the choice to what to do with the tracing run when @value{GDBN}
37891 disconnects from the target. A @var{value} of 1 directs the target to
37892 continue the tracing run, while 0 tells the target to stop tracing if
37893 @value{GDBN} is no longer in the picture.
37896 @cindex @samp{qTStatus} packet
37897 Ask the stub if there is a trace experiment running right now.
37899 The reply has the form:
37903 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37904 @var{running} is a single digit @code{1} if the trace is presently
37905 running, or @code{0} if not. It is followed by semicolon-separated
37906 optional fields that an agent may use to report additional status.
37910 If the trace is not running, the agent may report any of several
37911 explanations as one of the optional fields:
37916 No trace has been run yet.
37918 @item tstop[:@var{text}]:0
37919 The trace was stopped by a user-originated stop command. The optional
37920 @var{text} field is a user-supplied string supplied as part of the
37921 stop command (for instance, an explanation of why the trace was
37922 stopped manually). It is hex-encoded.
37925 The trace stopped because the trace buffer filled up.
37927 @item tdisconnected:0
37928 The trace stopped because @value{GDBN} disconnected from the target.
37930 @item tpasscount:@var{tpnum}
37931 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37933 @item terror:@var{text}:@var{tpnum}
37934 The trace stopped because tracepoint @var{tpnum} had an error. The
37935 string @var{text} is available to describe the nature of the error
37936 (for instance, a divide by zero in the condition expression); it
37940 The trace stopped for some other reason.
37944 Additional optional fields supply statistical and other information.
37945 Although not required, they are extremely useful for users monitoring
37946 the progress of a trace run. If a trace has stopped, and these
37947 numbers are reported, they must reflect the state of the just-stopped
37952 @item tframes:@var{n}
37953 The number of trace frames in the buffer.
37955 @item tcreated:@var{n}
37956 The total number of trace frames created during the run. This may
37957 be larger than the trace frame count, if the buffer is circular.
37959 @item tsize:@var{n}
37960 The total size of the trace buffer, in bytes.
37962 @item tfree:@var{n}
37963 The number of bytes still unused in the buffer.
37965 @item circular:@var{n}
37966 The value of the circular trace buffer flag. @code{1} means that the
37967 trace buffer is circular and old trace frames will be discarded if
37968 necessary to make room, @code{0} means that the trace buffer is linear
37971 @item disconn:@var{n}
37972 The value of the disconnected tracing flag. @code{1} means that
37973 tracing will continue after @value{GDBN} disconnects, @code{0} means
37974 that the trace run will stop.
37978 @item qTP:@var{tp}:@var{addr}
37979 @cindex tracepoint status, remote request
37980 @cindex @samp{qTP} packet
37981 Ask the stub for the current state of tracepoint number @var{tp} at
37982 address @var{addr}.
37986 @item V@var{hits}:@var{usage}
37987 The tracepoint has been hit @var{hits} times so far during the trace
37988 run, and accounts for @var{usage} in the trace buffer. Note that
37989 @code{while-stepping} steps are not counted as separate hits, but the
37990 steps' space consumption is added into the usage number.
37994 @item qTV:@var{var}
37995 @cindex trace state variable value, remote request
37996 @cindex @samp{qTV} packet
37997 Ask the stub for the value of the trace state variable number @var{var}.
38002 The value of the variable is @var{value}. This will be the current
38003 value of the variable if the user is examining a running target, or a
38004 saved value if the variable was collected in the trace frame that the
38005 user is looking at. Note that multiple requests may result in
38006 different reply values, such as when requesting values while the
38007 program is running.
38010 The value of the variable is unknown. This would occur, for example,
38011 if the user is examining a trace frame in which the requested variable
38016 @cindex @samp{qTfP} packet
38018 @cindex @samp{qTsP} packet
38019 These packets request data about tracepoints that are being used by
38020 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38021 of data, and multiple @code{qTsP} to get additional pieces. Replies
38022 to these packets generally take the form of the @code{QTDP} packets
38023 that define tracepoints. (FIXME add detailed syntax)
38026 @cindex @samp{qTfV} packet
38028 @cindex @samp{qTsV} packet
38029 These packets request data about trace state variables that are on the
38030 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38031 and multiple @code{qTsV} to get additional variables. Replies to
38032 these packets follow the syntax of the @code{QTDV} packets that define
38033 trace state variables.
38039 @cindex @samp{qTfSTM} packet
38040 @cindex @samp{qTsSTM} packet
38041 These packets request data about static tracepoint markers that exist
38042 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38043 first piece of data, and multiple @code{qTsSTM} to get additional
38044 pieces. Replies to these packets take the following form:
38048 @item m @var{address}:@var{id}:@var{extra}
38050 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38051 a comma-separated list of markers
38053 (lower case letter @samp{L}) denotes end of list.
38055 An error occurred. The error number @var{nn} is given as hex digits.
38057 An empty reply indicates that the request is not supported by the
38061 The @var{address} is encoded in hex;
38062 @var{id} and @var{extra} are strings encoded in hex.
38064 In response to each query, the target will reply with a list of one or
38065 more markers, separated by commas. @value{GDBN} will respond to each
38066 reply with a request for more markers (using the @samp{qs} form of the
38067 query), until the target responds with @samp{l} (lower-case ell, for
38070 @item qTSTMat:@var{address}
38072 @cindex @samp{qTSTMat} packet
38073 This packets requests data about static tracepoint markers in the
38074 target program at @var{address}. Replies to this packet follow the
38075 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38076 tracepoint markers.
38078 @item QTSave:@var{filename}
38079 @cindex @samp{QTSave} packet
38080 This packet directs the target to save trace data to the file name
38081 @var{filename} in the target's filesystem. The @var{filename} is encoded
38082 as a hex string; the interpretation of the file name (relative vs
38083 absolute, wild cards, etc) is up to the target.
38085 @item qTBuffer:@var{offset},@var{len}
38086 @cindex @samp{qTBuffer} packet
38087 Return up to @var{len} bytes of the current contents of trace buffer,
38088 starting at @var{offset}. The trace buffer is treated as if it were
38089 a contiguous collection of traceframes, as per the trace file format.
38090 The reply consists as many hex-encoded bytes as the target can deliver
38091 in a packet; it is not an error to return fewer than were asked for.
38092 A reply consisting of just @code{l} indicates that no bytes are
38095 @item QTBuffer:circular:@var{value}
38096 This packet directs the target to use a circular trace buffer if
38097 @var{value} is 1, or a linear buffer if the value is 0.
38099 @item QTBuffer:size:@var{size}
38100 @anchor{QTBuffer-size}
38101 @cindex @samp{QTBuffer size} packet
38102 This packet directs the target to make the trace buffer be of size
38103 @var{size} if possible. A value of @code{-1} tells the target to
38104 use whatever size it prefers.
38106 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38107 @cindex @samp{QTNotes} packet
38108 This packet adds optional textual notes to the trace run. Allowable
38109 types include @code{user}, @code{notes}, and @code{tstop}, the
38110 @var{text} fields are arbitrary strings, hex-encoded.
38114 @subsection Relocate instruction reply packet
38115 When installing fast tracepoints in memory, the target may need to
38116 relocate the instruction currently at the tracepoint address to a
38117 different address in memory. For most instructions, a simple copy is
38118 enough, but, for example, call instructions that implicitly push the
38119 return address on the stack, and relative branches or other
38120 PC-relative instructions require offset adjustment, so that the effect
38121 of executing the instruction at a different address is the same as if
38122 it had executed in the original location.
38124 In response to several of the tracepoint packets, the target may also
38125 respond with a number of intermediate @samp{qRelocInsn} request
38126 packets before the final result packet, to have @value{GDBN} handle
38127 this relocation operation. If a packet supports this mechanism, its
38128 documentation will explicitly say so. See for example the above
38129 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38130 format of the request is:
38133 @item qRelocInsn:@var{from};@var{to}
38135 This requests @value{GDBN} to copy instruction at address @var{from}
38136 to address @var{to}, possibly adjusted so that executing the
38137 instruction at @var{to} has the same effect as executing it at
38138 @var{from}. @value{GDBN} writes the adjusted instruction to target
38139 memory starting at @var{to}.
38144 @item qRelocInsn:@var{adjusted_size}
38145 Informs the stub the relocation is complete. The @var{adjusted_size} is
38146 the length in bytes of resulting relocated instruction sequence.
38148 A badly formed request was detected, or an error was encountered while
38149 relocating the instruction.
38152 @node Host I/O Packets
38153 @section Host I/O Packets
38154 @cindex Host I/O, remote protocol
38155 @cindex file transfer, remote protocol
38157 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38158 operations on the far side of a remote link. For example, Host I/O is
38159 used to upload and download files to a remote target with its own
38160 filesystem. Host I/O uses the same constant values and data structure
38161 layout as the target-initiated File-I/O protocol. However, the
38162 Host I/O packets are structured differently. The target-initiated
38163 protocol relies on target memory to store parameters and buffers.
38164 Host I/O requests are initiated by @value{GDBN}, and the
38165 target's memory is not involved. @xref{File-I/O Remote Protocol
38166 Extension}, for more details on the target-initiated protocol.
38168 The Host I/O request packets all encode a single operation along with
38169 its arguments. They have this format:
38173 @item vFile:@var{operation}: @var{parameter}@dots{}
38174 @var{operation} is the name of the particular request; the target
38175 should compare the entire packet name up to the second colon when checking
38176 for a supported operation. The format of @var{parameter} depends on
38177 the operation. Numbers are always passed in hexadecimal. Negative
38178 numbers have an explicit minus sign (i.e.@: two's complement is not
38179 used). Strings (e.g.@: filenames) are encoded as a series of
38180 hexadecimal bytes. The last argument to a system call may be a
38181 buffer of escaped binary data (@pxref{Binary Data}).
38185 The valid responses to Host I/O packets are:
38189 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38190 @var{result} is the integer value returned by this operation, usually
38191 non-negative for success and -1 for errors. If an error has occured,
38192 @var{errno} will be included in the result specifying a
38193 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38194 operations which return data, @var{attachment} supplies the data as a
38195 binary buffer. Binary buffers in response packets are escaped in the
38196 normal way (@pxref{Binary Data}). See the individual packet
38197 documentation for the interpretation of @var{result} and
38201 An empty response indicates that this operation is not recognized.
38205 These are the supported Host I/O operations:
38208 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38209 Open a file at @var{filename} and return a file descriptor for it, or
38210 return -1 if an error occurs. The @var{filename} is a string,
38211 @var{flags} is an integer indicating a mask of open flags
38212 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38213 of mode bits to use if the file is created (@pxref{mode_t Values}).
38214 @xref{open}, for details of the open flags and mode values.
38216 @item vFile:close: @var{fd}
38217 Close the open file corresponding to @var{fd} and return 0, or
38218 -1 if an error occurs.
38220 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38221 Read data from the open file corresponding to @var{fd}. Up to
38222 @var{count} bytes will be read from the file, starting at @var{offset}
38223 relative to the start of the file. The target may read fewer bytes;
38224 common reasons include packet size limits and an end-of-file
38225 condition. The number of bytes read is returned. Zero should only be
38226 returned for a successful read at the end of the file, or if
38227 @var{count} was zero.
38229 The data read should be returned as a binary attachment on success.
38230 If zero bytes were read, the response should include an empty binary
38231 attachment (i.e.@: a trailing semicolon). The return value is the
38232 number of target bytes read; the binary attachment may be longer if
38233 some characters were escaped.
38235 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38236 Write @var{data} (a binary buffer) to the open file corresponding
38237 to @var{fd}. Start the write at @var{offset} from the start of the
38238 file. Unlike many @code{write} system calls, there is no
38239 separate @var{count} argument; the length of @var{data} in the
38240 packet is used. @samp{vFile:write} returns the number of bytes written,
38241 which may be shorter than the length of @var{data}, or -1 if an
38244 @item vFile:fstat: @var{fd}
38245 Get information about the open file corresponding to @var{fd}.
38246 On success the information is returned as a binary attachment
38247 and the return value is the size of this attachment in bytes.
38248 If an error occurs the return value is -1. The format of the
38249 returned binary attachment is as described in @ref{struct stat}.
38251 @item vFile:unlink: @var{filename}
38252 Delete the file at @var{filename} on the target. Return 0,
38253 or -1 if an error occurs. The @var{filename} is a string.
38255 @item vFile:readlink: @var{filename}
38256 Read value of symbolic link @var{filename} on the target. Return
38257 the number of bytes read, or -1 if an error occurs.
38259 The data read should be returned as a binary attachment on success.
38260 If zero bytes were read, the response should include an empty binary
38261 attachment (i.e.@: a trailing semicolon). The return value is the
38262 number of target bytes read; the binary attachment may be longer if
38263 some characters were escaped.
38265 @item vFile:setfs: @var{pid}
38266 Select the filesystem on which @code{vFile} operations with
38267 @var{filename} arguments will operate. This is required for
38268 @value{GDBN} to be able to access files on remote targets where
38269 the remote stub does not share a common filesystem with the
38272 If @var{pid} is nonzero, select the filesystem as seen by process
38273 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38274 the remote stub. Return 0 on success, or -1 if an error occurs.
38275 If @code{vFile:setfs:} indicates success, the selected filesystem
38276 remains selected until the next successful @code{vFile:setfs:}
38282 @section Interrupts
38283 @cindex interrupts (remote protocol)
38284 @anchor{interrupting remote targets}
38286 In all-stop mode, when a program on the remote target is running,
38287 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38288 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38289 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38291 The precise meaning of @code{BREAK} is defined by the transport
38292 mechanism and may, in fact, be undefined. @value{GDBN} does not
38293 currently define a @code{BREAK} mechanism for any of the network
38294 interfaces except for TCP, in which case @value{GDBN} sends the
38295 @code{telnet} BREAK sequence.
38297 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38298 transport mechanisms. It is represented by sending the single byte
38299 @code{0x03} without any of the usual packet overhead described in
38300 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38301 transmitted as part of a packet, it is considered to be packet data
38302 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38303 (@pxref{X packet}), used for binary downloads, may include an unescaped
38304 @code{0x03} as part of its packet.
38306 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38307 When Linux kernel receives this sequence from serial port,
38308 it stops execution and connects to gdb.
38310 In non-stop mode, because packet resumptions are asynchronous
38311 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38312 command to the remote stub, even when the target is running. For that
38313 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38314 packet}) with the usual packet framing instead of the single byte
38317 Stubs are not required to recognize these interrupt mechanisms and the
38318 precise meaning associated with receipt of the interrupt is
38319 implementation defined. If the target supports debugging of multiple
38320 threads and/or processes, it should attempt to interrupt all
38321 currently-executing threads and processes.
38322 If the stub is successful at interrupting the
38323 running program, it should send one of the stop
38324 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38325 of successfully stopping the program in all-stop mode, and a stop reply
38326 for each stopped thread in non-stop mode.
38327 Interrupts received while the
38328 program is stopped are queued and the program will be interrupted when
38329 it is resumed next time.
38331 @node Notification Packets
38332 @section Notification Packets
38333 @cindex notification packets
38334 @cindex packets, notification
38336 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38337 packets that require no acknowledgment. Both the GDB and the stub
38338 may send notifications (although the only notifications defined at
38339 present are sent by the stub). Notifications carry information
38340 without incurring the round-trip latency of an acknowledgment, and so
38341 are useful for low-impact communications where occasional packet loss
38344 A notification packet has the form @samp{% @var{data} #
38345 @var{checksum}}, where @var{data} is the content of the notification,
38346 and @var{checksum} is a checksum of @var{data}, computed and formatted
38347 as for ordinary @value{GDBN} packets. A notification's @var{data}
38348 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38349 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38350 to acknowledge the notification's receipt or to report its corruption.
38352 Every notification's @var{data} begins with a name, which contains no
38353 colon characters, followed by a colon character.
38355 Recipients should silently ignore corrupted notifications and
38356 notifications they do not understand. Recipients should restart
38357 timeout periods on receipt of a well-formed notification, whether or
38358 not they understand it.
38360 Senders should only send the notifications described here when this
38361 protocol description specifies that they are permitted. In the
38362 future, we may extend the protocol to permit existing notifications in
38363 new contexts; this rule helps older senders avoid confusing newer
38366 (Older versions of @value{GDBN} ignore bytes received until they see
38367 the @samp{$} byte that begins an ordinary packet, so new stubs may
38368 transmit notifications without fear of confusing older clients. There
38369 are no notifications defined for @value{GDBN} to send at the moment, but we
38370 assume that most older stubs would ignore them, as well.)
38372 Each notification is comprised of three parts:
38374 @item @var{name}:@var{event}
38375 The notification packet is sent by the side that initiates the
38376 exchange (currently, only the stub does that), with @var{event}
38377 carrying the specific information about the notification, and
38378 @var{name} specifying the name of the notification.
38380 The acknowledge sent by the other side, usually @value{GDBN}, to
38381 acknowledge the exchange and request the event.
38384 The purpose of an asynchronous notification mechanism is to report to
38385 @value{GDBN} that something interesting happened in the remote stub.
38387 The remote stub may send notification @var{name}:@var{event}
38388 at any time, but @value{GDBN} acknowledges the notification when
38389 appropriate. The notification event is pending before @value{GDBN}
38390 acknowledges. Only one notification at a time may be pending; if
38391 additional events occur before @value{GDBN} has acknowledged the
38392 previous notification, they must be queued by the stub for later
38393 synchronous transmission in response to @var{ack} packets from
38394 @value{GDBN}. Because the notification mechanism is unreliable,
38395 the stub is permitted to resend a notification if it believes
38396 @value{GDBN} may not have received it.
38398 Specifically, notifications may appear when @value{GDBN} is not
38399 otherwise reading input from the stub, or when @value{GDBN} is
38400 expecting to read a normal synchronous response or a
38401 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38402 Notification packets are distinct from any other communication from
38403 the stub so there is no ambiguity.
38405 After receiving a notification, @value{GDBN} shall acknowledge it by
38406 sending a @var{ack} packet as a regular, synchronous request to the
38407 stub. Such acknowledgment is not required to happen immediately, as
38408 @value{GDBN} is permitted to send other, unrelated packets to the
38409 stub first, which the stub should process normally.
38411 Upon receiving a @var{ack} packet, if the stub has other queued
38412 events to report to @value{GDBN}, it shall respond by sending a
38413 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38414 packet to solicit further responses; again, it is permitted to send
38415 other, unrelated packets as well which the stub should process
38418 If the stub receives a @var{ack} packet and there are no additional
38419 @var{event} to report, the stub shall return an @samp{OK} response.
38420 At this point, @value{GDBN} has finished processing a notification
38421 and the stub has completed sending any queued events. @value{GDBN}
38422 won't accept any new notifications until the final @samp{OK} is
38423 received . If further notification events occur, the stub shall send
38424 a new notification, @value{GDBN} shall accept the notification, and
38425 the process shall be repeated.
38427 The process of asynchronous notification can be illustrated by the
38430 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38433 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38435 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38440 The following notifications are defined:
38441 @multitable @columnfractions 0.12 0.12 0.38 0.38
38450 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38451 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38452 for information on how these notifications are acknowledged by
38454 @tab Report an asynchronous stop event in non-stop mode.
38458 @node Remote Non-Stop
38459 @section Remote Protocol Support for Non-Stop Mode
38461 @value{GDBN}'s remote protocol supports non-stop debugging of
38462 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38463 supports non-stop mode, it should report that to @value{GDBN} by including
38464 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38466 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38467 establishing a new connection with the stub. Entering non-stop mode
38468 does not alter the state of any currently-running threads, but targets
38469 must stop all threads in any already-attached processes when entering
38470 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38471 probe the target state after a mode change.
38473 In non-stop mode, when an attached process encounters an event that
38474 would otherwise be reported with a stop reply, it uses the
38475 asynchronous notification mechanism (@pxref{Notification Packets}) to
38476 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38477 in all processes are stopped when a stop reply is sent, in non-stop
38478 mode only the thread reporting the stop event is stopped. That is,
38479 when reporting a @samp{S} or @samp{T} response to indicate completion
38480 of a step operation, hitting a breakpoint, or a fault, only the
38481 affected thread is stopped; any other still-running threads continue
38482 to run. When reporting a @samp{W} or @samp{X} response, all running
38483 threads belonging to other attached processes continue to run.
38485 In non-stop mode, the target shall respond to the @samp{?} packet as
38486 follows. First, any incomplete stop reply notification/@samp{vStopped}
38487 sequence in progress is abandoned. The target must begin a new
38488 sequence reporting stop events for all stopped threads, whether or not
38489 it has previously reported those events to @value{GDBN}. The first
38490 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38491 subsequent stop replies are sent as responses to @samp{vStopped} packets
38492 using the mechanism described above. The target must not send
38493 asynchronous stop reply notifications until the sequence is complete.
38494 If all threads are running when the target receives the @samp{?} packet,
38495 or if the target is not attached to any process, it shall respond
38498 If the stub supports non-stop mode, it should also support the
38499 @samp{swbreak} stop reason if software breakpoints are supported, and
38500 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38501 (@pxref{swbreak stop reason}). This is because given the asynchronous
38502 nature of non-stop mode, between the time a thread hits a breakpoint
38503 and the time the event is finally processed by @value{GDBN}, the
38504 breakpoint may have already been removed from the target. Due to
38505 this, @value{GDBN} needs to be able to tell whether a trap stop was
38506 caused by a delayed breakpoint event, which should be ignored, as
38507 opposed to a random trap signal, which should be reported to the user.
38508 Note the @samp{swbreak} feature implies that the target is responsible
38509 for adjusting the PC when a software breakpoint triggers, if
38510 necessary, such as on the x86 architecture.
38512 @node Packet Acknowledgment
38513 @section Packet Acknowledgment
38515 @cindex acknowledgment, for @value{GDBN} remote
38516 @cindex packet acknowledgment, for @value{GDBN} remote
38517 By default, when either the host or the target machine receives a packet,
38518 the first response expected is an acknowledgment: either @samp{+} (to indicate
38519 the package was received correctly) or @samp{-} (to request retransmission).
38520 This mechanism allows the @value{GDBN} remote protocol to operate over
38521 unreliable transport mechanisms, such as a serial line.
38523 In cases where the transport mechanism is itself reliable (such as a pipe or
38524 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38525 It may be desirable to disable them in that case to reduce communication
38526 overhead, or for other reasons. This can be accomplished by means of the
38527 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38529 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38530 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38531 and response format still includes the normal checksum, as described in
38532 @ref{Overview}, but the checksum may be ignored by the receiver.
38534 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38535 no-acknowledgment mode, it should report that to @value{GDBN}
38536 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38537 @pxref{qSupported}.
38538 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38539 disabled via the @code{set remote noack-packet off} command
38540 (@pxref{Remote Configuration}),
38541 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38542 Only then may the stub actually turn off packet acknowledgments.
38543 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38544 response, which can be safely ignored by the stub.
38546 Note that @code{set remote noack-packet} command only affects negotiation
38547 between @value{GDBN} and the stub when subsequent connections are made;
38548 it does not affect the protocol acknowledgment state for any current
38550 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38551 new connection is established,
38552 there is also no protocol request to re-enable the acknowledgments
38553 for the current connection, once disabled.
38558 Example sequence of a target being re-started. Notice how the restart
38559 does not get any direct output:
38564 @emph{target restarts}
38567 <- @code{T001:1234123412341234}
38571 Example sequence of a target being stepped by a single instruction:
38574 -> @code{G1445@dots{}}
38579 <- @code{T001:1234123412341234}
38583 <- @code{1455@dots{}}
38587 @node File-I/O Remote Protocol Extension
38588 @section File-I/O Remote Protocol Extension
38589 @cindex File-I/O remote protocol extension
38592 * File-I/O Overview::
38593 * Protocol Basics::
38594 * The F Request Packet::
38595 * The F Reply Packet::
38596 * The Ctrl-C Message::
38598 * List of Supported Calls::
38599 * Protocol-specific Representation of Datatypes::
38601 * File-I/O Examples::
38604 @node File-I/O Overview
38605 @subsection File-I/O Overview
38606 @cindex file-i/o overview
38608 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38609 target to use the host's file system and console I/O to perform various
38610 system calls. System calls on the target system are translated into a
38611 remote protocol packet to the host system, which then performs the needed
38612 actions and returns a response packet to the target system.
38613 This simulates file system operations even on targets that lack file systems.
38615 The protocol is defined to be independent of both the host and target systems.
38616 It uses its own internal representation of datatypes and values. Both
38617 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38618 translating the system-dependent value representations into the internal
38619 protocol representations when data is transmitted.
38621 The communication is synchronous. A system call is possible only when
38622 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38623 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38624 the target is stopped to allow deterministic access to the target's
38625 memory. Therefore File-I/O is not interruptible by target signals. On
38626 the other hand, it is possible to interrupt File-I/O by a user interrupt
38627 (@samp{Ctrl-C}) within @value{GDBN}.
38629 The target's request to perform a host system call does not finish
38630 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38631 after finishing the system call, the target returns to continuing the
38632 previous activity (continue, step). No additional continue or step
38633 request from @value{GDBN} is required.
38636 (@value{GDBP}) continue
38637 <- target requests 'system call X'
38638 target is stopped, @value{GDBN} executes system call
38639 -> @value{GDBN} returns result
38640 ... target continues, @value{GDBN} returns to wait for the target
38641 <- target hits breakpoint and sends a Txx packet
38644 The protocol only supports I/O on the console and to regular files on
38645 the host file system. Character or block special devices, pipes,
38646 named pipes, sockets or any other communication method on the host
38647 system are not supported by this protocol.
38649 File I/O is not supported in non-stop mode.
38651 @node Protocol Basics
38652 @subsection Protocol Basics
38653 @cindex protocol basics, file-i/o
38655 The File-I/O protocol uses the @code{F} packet as the request as well
38656 as reply packet. Since a File-I/O system call can only occur when
38657 @value{GDBN} is waiting for a response from the continuing or stepping target,
38658 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38659 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38660 This @code{F} packet contains all information needed to allow @value{GDBN}
38661 to call the appropriate host system call:
38665 A unique identifier for the requested system call.
38668 All parameters to the system call. Pointers are given as addresses
38669 in the target memory address space. Pointers to strings are given as
38670 pointer/length pair. Numerical values are given as they are.
38671 Numerical control flags are given in a protocol-specific representation.
38675 At this point, @value{GDBN} has to perform the following actions.
38679 If the parameters include pointer values to data needed as input to a
38680 system call, @value{GDBN} requests this data from the target with a
38681 standard @code{m} packet request. This additional communication has to be
38682 expected by the target implementation and is handled as any other @code{m}
38686 @value{GDBN} translates all value from protocol representation to host
38687 representation as needed. Datatypes are coerced into the host types.
38690 @value{GDBN} calls the system call.
38693 It then coerces datatypes back to protocol representation.
38696 If the system call is expected to return data in buffer space specified
38697 by pointer parameters to the call, the data is transmitted to the
38698 target using a @code{M} or @code{X} packet. This packet has to be expected
38699 by the target implementation and is handled as any other @code{M} or @code{X}
38704 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38705 necessary information for the target to continue. This at least contains
38712 @code{errno}, if has been changed by the system call.
38719 After having done the needed type and value coercion, the target continues
38720 the latest continue or step action.
38722 @node The F Request Packet
38723 @subsection The @code{F} Request Packet
38724 @cindex file-i/o request packet
38725 @cindex @code{F} request packet
38727 The @code{F} request packet has the following format:
38730 @item F@var{call-id},@var{parameter@dots{}}
38732 @var{call-id} is the identifier to indicate the host system call to be called.
38733 This is just the name of the function.
38735 @var{parameter@dots{}} are the parameters to the system call.
38736 Parameters are hexadecimal integer values, either the actual values in case
38737 of scalar datatypes, pointers to target buffer space in case of compound
38738 datatypes and unspecified memory areas, or pointer/length pairs in case
38739 of string parameters. These are appended to the @var{call-id} as a
38740 comma-delimited list. All values are transmitted in ASCII
38741 string representation, pointer/length pairs separated by a slash.
38747 @node The F Reply Packet
38748 @subsection The @code{F} Reply Packet
38749 @cindex file-i/o reply packet
38750 @cindex @code{F} reply packet
38752 The @code{F} reply packet has the following format:
38756 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38758 @var{retcode} is the return code of the system call as hexadecimal value.
38760 @var{errno} is the @code{errno} set by the call, in protocol-specific
38762 This parameter can be omitted if the call was successful.
38764 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38765 case, @var{errno} must be sent as well, even if the call was successful.
38766 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38773 or, if the call was interrupted before the host call has been performed:
38780 assuming 4 is the protocol-specific representation of @code{EINTR}.
38785 @node The Ctrl-C Message
38786 @subsection The @samp{Ctrl-C} Message
38787 @cindex ctrl-c message, in file-i/o protocol
38789 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38790 reply packet (@pxref{The F Reply Packet}),
38791 the target should behave as if it had
38792 gotten a break message. The meaning for the target is ``system call
38793 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38794 (as with a break message) and return to @value{GDBN} with a @code{T02}
38797 It's important for the target to know in which
38798 state the system call was interrupted. There are two possible cases:
38802 The system call hasn't been performed on the host yet.
38805 The system call on the host has been finished.
38809 These two states can be distinguished by the target by the value of the
38810 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38811 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38812 on POSIX systems. In any other case, the target may presume that the
38813 system call has been finished --- successfully or not --- and should behave
38814 as if the break message arrived right after the system call.
38816 @value{GDBN} must behave reliably. If the system call has not been called
38817 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38818 @code{errno} in the packet. If the system call on the host has been finished
38819 before the user requests a break, the full action must be finished by
38820 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38821 The @code{F} packet may only be sent when either nothing has happened
38822 or the full action has been completed.
38825 @subsection Console I/O
38826 @cindex console i/o as part of file-i/o
38828 By default and if not explicitly closed by the target system, the file
38829 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38830 on the @value{GDBN} console is handled as any other file output operation
38831 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38832 by @value{GDBN} so that after the target read request from file descriptor
38833 0 all following typing is buffered until either one of the following
38838 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38840 system call is treated as finished.
38843 The user presses @key{RET}. This is treated as end of input with a trailing
38847 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38848 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38852 If the user has typed more characters than fit in the buffer given to
38853 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38854 either another @code{read(0, @dots{})} is requested by the target, or debugging
38855 is stopped at the user's request.
38858 @node List of Supported Calls
38859 @subsection List of Supported Calls
38860 @cindex list of supported file-i/o calls
38877 @unnumberedsubsubsec open
38878 @cindex open, file-i/o system call
38883 int open(const char *pathname, int flags);
38884 int open(const char *pathname, int flags, mode_t mode);
38888 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38891 @var{flags} is the bitwise @code{OR} of the following values:
38895 If the file does not exist it will be created. The host
38896 rules apply as far as file ownership and time stamps
38900 When used with @code{O_CREAT}, if the file already exists it is
38901 an error and open() fails.
38904 If the file already exists and the open mode allows
38905 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38906 truncated to zero length.
38909 The file is opened in append mode.
38912 The file is opened for reading only.
38915 The file is opened for writing only.
38918 The file is opened for reading and writing.
38922 Other bits are silently ignored.
38926 @var{mode} is the bitwise @code{OR} of the following values:
38930 User has read permission.
38933 User has write permission.
38936 Group has read permission.
38939 Group has write permission.
38942 Others have read permission.
38945 Others have write permission.
38949 Other bits are silently ignored.
38952 @item Return value:
38953 @code{open} returns the new file descriptor or -1 if an error
38960 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38963 @var{pathname} refers to a directory.
38966 The requested access is not allowed.
38969 @var{pathname} was too long.
38972 A directory component in @var{pathname} does not exist.
38975 @var{pathname} refers to a device, pipe, named pipe or socket.
38978 @var{pathname} refers to a file on a read-only filesystem and
38979 write access was requested.
38982 @var{pathname} is an invalid pointer value.
38985 No space on device to create the file.
38988 The process already has the maximum number of files open.
38991 The limit on the total number of files open on the system
38995 The call was interrupted by the user.
39001 @unnumberedsubsubsec close
39002 @cindex close, file-i/o system call
39011 @samp{Fclose,@var{fd}}
39013 @item Return value:
39014 @code{close} returns zero on success, or -1 if an error occurred.
39020 @var{fd} isn't a valid open file descriptor.
39023 The call was interrupted by the user.
39029 @unnumberedsubsubsec read
39030 @cindex read, file-i/o system call
39035 int read(int fd, void *buf, unsigned int count);
39039 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39041 @item Return value:
39042 On success, the number of bytes read is returned.
39043 Zero indicates end of file. If count is zero, read
39044 returns zero as well. On error, -1 is returned.
39050 @var{fd} is not a valid file descriptor or is not open for
39054 @var{bufptr} is an invalid pointer value.
39057 The call was interrupted by the user.
39063 @unnumberedsubsubsec write
39064 @cindex write, file-i/o system call
39069 int write(int fd, const void *buf, unsigned int count);
39073 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39075 @item Return value:
39076 On success, the number of bytes written are returned.
39077 Zero indicates nothing was written. On error, -1
39084 @var{fd} is not a valid file descriptor or is not open for
39088 @var{bufptr} is an invalid pointer value.
39091 An attempt was made to write a file that exceeds the
39092 host-specific maximum file size allowed.
39095 No space on device to write the data.
39098 The call was interrupted by the user.
39104 @unnumberedsubsubsec lseek
39105 @cindex lseek, file-i/o system call
39110 long lseek (int fd, long offset, int flag);
39114 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39116 @var{flag} is one of:
39120 The offset is set to @var{offset} bytes.
39123 The offset is set to its current location plus @var{offset}
39127 The offset is set to the size of the file plus @var{offset}
39131 @item Return value:
39132 On success, the resulting unsigned offset in bytes from
39133 the beginning of the file is returned. Otherwise, a
39134 value of -1 is returned.
39140 @var{fd} is not a valid open file descriptor.
39143 @var{fd} is associated with the @value{GDBN} console.
39146 @var{flag} is not a proper value.
39149 The call was interrupted by the user.
39155 @unnumberedsubsubsec rename
39156 @cindex rename, file-i/o system call
39161 int rename(const char *oldpath, const char *newpath);
39165 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39167 @item Return value:
39168 On success, zero is returned. On error, -1 is returned.
39174 @var{newpath} is an existing directory, but @var{oldpath} is not a
39178 @var{newpath} is a non-empty directory.
39181 @var{oldpath} or @var{newpath} is a directory that is in use by some
39185 An attempt was made to make a directory a subdirectory
39189 A component used as a directory in @var{oldpath} or new
39190 path is not a directory. Or @var{oldpath} is a directory
39191 and @var{newpath} exists but is not a directory.
39194 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39197 No access to the file or the path of the file.
39201 @var{oldpath} or @var{newpath} was too long.
39204 A directory component in @var{oldpath} or @var{newpath} does not exist.
39207 The file is on a read-only filesystem.
39210 The device containing the file has no room for the new
39214 The call was interrupted by the user.
39220 @unnumberedsubsubsec unlink
39221 @cindex unlink, file-i/o system call
39226 int unlink(const char *pathname);
39230 @samp{Funlink,@var{pathnameptr}/@var{len}}
39232 @item Return value:
39233 On success, zero is returned. On error, -1 is returned.
39239 No access to the file or the path of the file.
39242 The system does not allow unlinking of directories.
39245 The file @var{pathname} cannot be unlinked because it's
39246 being used by another process.
39249 @var{pathnameptr} is an invalid pointer value.
39252 @var{pathname} was too long.
39255 A directory component in @var{pathname} does not exist.
39258 A component of the path is not a directory.
39261 The file is on a read-only filesystem.
39264 The call was interrupted by the user.
39270 @unnumberedsubsubsec stat/fstat
39271 @cindex fstat, file-i/o system call
39272 @cindex stat, file-i/o system call
39277 int stat(const char *pathname, struct stat *buf);
39278 int fstat(int fd, struct stat *buf);
39282 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39283 @samp{Ffstat,@var{fd},@var{bufptr}}
39285 @item Return value:
39286 On success, zero is returned. On error, -1 is returned.
39292 @var{fd} is not a valid open file.
39295 A directory component in @var{pathname} does not exist or the
39296 path is an empty string.
39299 A component of the path is not a directory.
39302 @var{pathnameptr} is an invalid pointer value.
39305 No access to the file or the path of the file.
39308 @var{pathname} was too long.
39311 The call was interrupted by the user.
39317 @unnumberedsubsubsec gettimeofday
39318 @cindex gettimeofday, file-i/o system call
39323 int gettimeofday(struct timeval *tv, void *tz);
39327 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39329 @item Return value:
39330 On success, 0 is returned, -1 otherwise.
39336 @var{tz} is a non-NULL pointer.
39339 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39345 @unnumberedsubsubsec isatty
39346 @cindex isatty, file-i/o system call
39351 int isatty(int fd);
39355 @samp{Fisatty,@var{fd}}
39357 @item Return value:
39358 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39364 The call was interrupted by the user.
39369 Note that the @code{isatty} call is treated as a special case: it returns
39370 1 to the target if the file descriptor is attached
39371 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39372 would require implementing @code{ioctl} and would be more complex than
39377 @unnumberedsubsubsec system
39378 @cindex system, file-i/o system call
39383 int system(const char *command);
39387 @samp{Fsystem,@var{commandptr}/@var{len}}
39389 @item Return value:
39390 If @var{len} is zero, the return value indicates whether a shell is
39391 available. A zero return value indicates a shell is not available.
39392 For non-zero @var{len}, the value returned is -1 on error and the
39393 return status of the command otherwise. Only the exit status of the
39394 command is returned, which is extracted from the host's @code{system}
39395 return value by calling @code{WEXITSTATUS(retval)}. In case
39396 @file{/bin/sh} could not be executed, 127 is returned.
39402 The call was interrupted by the user.
39407 @value{GDBN} takes over the full task of calling the necessary host calls
39408 to perform the @code{system} call. The return value of @code{system} on
39409 the host is simplified before it's returned
39410 to the target. Any termination signal information from the child process
39411 is discarded, and the return value consists
39412 entirely of the exit status of the called command.
39414 Due to security concerns, the @code{system} call is by default refused
39415 by @value{GDBN}. The user has to allow this call explicitly with the
39416 @code{set remote system-call-allowed 1} command.
39419 @item set remote system-call-allowed
39420 @kindex set remote system-call-allowed
39421 Control whether to allow the @code{system} calls in the File I/O
39422 protocol for the remote target. The default is zero (disabled).
39424 @item show remote system-call-allowed
39425 @kindex show remote system-call-allowed
39426 Show whether the @code{system} calls are allowed in the File I/O
39430 @node Protocol-specific Representation of Datatypes
39431 @subsection Protocol-specific Representation of Datatypes
39432 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39435 * Integral Datatypes::
39437 * Memory Transfer::
39442 @node Integral Datatypes
39443 @unnumberedsubsubsec Integral Datatypes
39444 @cindex integral datatypes, in file-i/o protocol
39446 The integral datatypes used in the system calls are @code{int},
39447 @code{unsigned int}, @code{long}, @code{unsigned long},
39448 @code{mode_t}, and @code{time_t}.
39450 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39451 implemented as 32 bit values in this protocol.
39453 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39455 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39456 in @file{limits.h}) to allow range checking on host and target.
39458 @code{time_t} datatypes are defined as seconds since the Epoch.
39460 All integral datatypes transferred as part of a memory read or write of a
39461 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39464 @node Pointer Values
39465 @unnumberedsubsubsec Pointer Values
39466 @cindex pointer values, in file-i/o protocol
39468 Pointers to target data are transmitted as they are. An exception
39469 is made for pointers to buffers for which the length isn't
39470 transmitted as part of the function call, namely strings. Strings
39471 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39478 which is a pointer to data of length 18 bytes at position 0x1aaf.
39479 The length is defined as the full string length in bytes, including
39480 the trailing null byte. For example, the string @code{"hello world"}
39481 at address 0x123456 is transmitted as
39487 @node Memory Transfer
39488 @unnumberedsubsubsec Memory Transfer
39489 @cindex memory transfer, in file-i/o protocol
39491 Structured data which is transferred using a memory read or write (for
39492 example, a @code{struct stat}) is expected to be in a protocol-specific format
39493 with all scalar multibyte datatypes being big endian. Translation to
39494 this representation needs to be done both by the target before the @code{F}
39495 packet is sent, and by @value{GDBN} before
39496 it transfers memory to the target. Transferred pointers to structured
39497 data should point to the already-coerced data at any time.
39501 @unnumberedsubsubsec struct stat
39502 @cindex struct stat, in file-i/o protocol
39504 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39505 is defined as follows:
39509 unsigned int st_dev; /* device */
39510 unsigned int st_ino; /* inode */
39511 mode_t st_mode; /* protection */
39512 unsigned int st_nlink; /* number of hard links */
39513 unsigned int st_uid; /* user ID of owner */
39514 unsigned int st_gid; /* group ID of owner */
39515 unsigned int st_rdev; /* device type (if inode device) */
39516 unsigned long st_size; /* total size, in bytes */
39517 unsigned long st_blksize; /* blocksize for filesystem I/O */
39518 unsigned long st_blocks; /* number of blocks allocated */
39519 time_t st_atime; /* time of last access */
39520 time_t st_mtime; /* time of last modification */
39521 time_t st_ctime; /* time of last change */
39525 The integral datatypes conform to the definitions given in the
39526 appropriate section (see @ref{Integral Datatypes}, for details) so this
39527 structure is of size 64 bytes.
39529 The values of several fields have a restricted meaning and/or
39535 A value of 0 represents a file, 1 the console.
39538 No valid meaning for the target. Transmitted unchanged.
39541 Valid mode bits are described in @ref{Constants}. Any other
39542 bits have currently no meaning for the target.
39547 No valid meaning for the target. Transmitted unchanged.
39552 These values have a host and file system dependent
39553 accuracy. Especially on Windows hosts, the file system may not
39554 support exact timing values.
39557 The target gets a @code{struct stat} of the above representation and is
39558 responsible for coercing it to the target representation before
39561 Note that due to size differences between the host, target, and protocol
39562 representations of @code{struct stat} members, these members could eventually
39563 get truncated on the target.
39565 @node struct timeval
39566 @unnumberedsubsubsec struct timeval
39567 @cindex struct timeval, in file-i/o protocol
39569 The buffer of type @code{struct timeval} used by the File-I/O protocol
39570 is defined as follows:
39574 time_t tv_sec; /* second */
39575 long tv_usec; /* microsecond */
39579 The integral datatypes conform to the definitions given in the
39580 appropriate section (see @ref{Integral Datatypes}, for details) so this
39581 structure is of size 8 bytes.
39584 @subsection Constants
39585 @cindex constants, in file-i/o protocol
39587 The following values are used for the constants inside of the
39588 protocol. @value{GDBN} and target are responsible for translating these
39589 values before and after the call as needed.
39600 @unnumberedsubsubsec Open Flags
39601 @cindex open flags, in file-i/o protocol
39603 All values are given in hexadecimal representation.
39615 @node mode_t Values
39616 @unnumberedsubsubsec mode_t Values
39617 @cindex mode_t values, in file-i/o protocol
39619 All values are given in octal representation.
39636 @unnumberedsubsubsec Errno Values
39637 @cindex errno values, in file-i/o protocol
39639 All values are given in decimal representation.
39664 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39665 any error value not in the list of supported error numbers.
39668 @unnumberedsubsubsec Lseek Flags
39669 @cindex lseek flags, in file-i/o protocol
39678 @unnumberedsubsubsec Limits
39679 @cindex limits, in file-i/o protocol
39681 All values are given in decimal representation.
39684 INT_MIN -2147483648
39686 UINT_MAX 4294967295
39687 LONG_MIN -9223372036854775808
39688 LONG_MAX 9223372036854775807
39689 ULONG_MAX 18446744073709551615
39692 @node File-I/O Examples
39693 @subsection File-I/O Examples
39694 @cindex file-i/o examples
39696 Example sequence of a write call, file descriptor 3, buffer is at target
39697 address 0x1234, 6 bytes should be written:
39700 <- @code{Fwrite,3,1234,6}
39701 @emph{request memory read from target}
39704 @emph{return "6 bytes written"}
39708 Example sequence of a read call, file descriptor 3, buffer is at target
39709 address 0x1234, 6 bytes should be read:
39712 <- @code{Fread,3,1234,6}
39713 @emph{request memory write to target}
39714 -> @code{X1234,6:XXXXXX}
39715 @emph{return "6 bytes read"}
39719 Example sequence of a read call, call fails on the host due to invalid
39720 file descriptor (@code{EBADF}):
39723 <- @code{Fread,3,1234,6}
39727 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39731 <- @code{Fread,3,1234,6}
39736 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39740 <- @code{Fread,3,1234,6}
39741 -> @code{X1234,6:XXXXXX}
39745 @node Library List Format
39746 @section Library List Format
39747 @cindex library list format, remote protocol
39749 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39750 same process as your application to manage libraries. In this case,
39751 @value{GDBN} can use the loader's symbol table and normal memory
39752 operations to maintain a list of shared libraries. On other
39753 platforms, the operating system manages loaded libraries.
39754 @value{GDBN} can not retrieve the list of currently loaded libraries
39755 through memory operations, so it uses the @samp{qXfer:libraries:read}
39756 packet (@pxref{qXfer library list read}) instead. The remote stub
39757 queries the target's operating system and reports which libraries
39760 The @samp{qXfer:libraries:read} packet returns an XML document which
39761 lists loaded libraries and their offsets. Each library has an
39762 associated name and one or more segment or section base addresses,
39763 which report where the library was loaded in memory.
39765 For the common case of libraries that are fully linked binaries, the
39766 library should have a list of segments. If the target supports
39767 dynamic linking of a relocatable object file, its library XML element
39768 should instead include a list of allocated sections. The segment or
39769 section bases are start addresses, not relocation offsets; they do not
39770 depend on the library's link-time base addresses.
39772 @value{GDBN} must be linked with the Expat library to support XML
39773 library lists. @xref{Expat}.
39775 A simple memory map, with one loaded library relocated by a single
39776 offset, looks like this:
39780 <library name="/lib/libc.so.6">
39781 <segment address="0x10000000"/>
39786 Another simple memory map, with one loaded library with three
39787 allocated sections (.text, .data, .bss), looks like this:
39791 <library name="sharedlib.o">
39792 <section address="0x10000000"/>
39793 <section address="0x20000000"/>
39794 <section address="0x30000000"/>
39799 The format of a library list is described by this DTD:
39802 <!-- library-list: Root element with versioning -->
39803 <!ELEMENT library-list (library)*>
39804 <!ATTLIST library-list version CDATA #FIXED "1.0">
39805 <!ELEMENT library (segment*, section*)>
39806 <!ATTLIST library name CDATA #REQUIRED>
39807 <!ELEMENT segment EMPTY>
39808 <!ATTLIST segment address CDATA #REQUIRED>
39809 <!ELEMENT section EMPTY>
39810 <!ATTLIST section address CDATA #REQUIRED>
39813 In addition, segments and section descriptors cannot be mixed within a
39814 single library element, and you must supply at least one segment or
39815 section for each library.
39817 @node Library List Format for SVR4 Targets
39818 @section Library List Format for SVR4 Targets
39819 @cindex library list format, remote protocol
39821 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39822 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39823 shared libraries. Still a special library list provided by this packet is
39824 more efficient for the @value{GDBN} remote protocol.
39826 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39827 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39828 target, the following parameters are reported:
39832 @code{name}, the absolute file name from the @code{l_name} field of
39833 @code{struct link_map}.
39835 @code{lm} with address of @code{struct link_map} used for TLS
39836 (Thread Local Storage) access.
39838 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39839 @code{struct link_map}. For prelinked libraries this is not an absolute
39840 memory address. It is a displacement of absolute memory address against
39841 address the file was prelinked to during the library load.
39843 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39846 Additionally the single @code{main-lm} attribute specifies address of
39847 @code{struct link_map} used for the main executable. This parameter is used
39848 for TLS access and its presence is optional.
39850 @value{GDBN} must be linked with the Expat library to support XML
39851 SVR4 library lists. @xref{Expat}.
39853 A simple memory map, with two loaded libraries (which do not use prelink),
39857 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39858 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39860 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39862 </library-list-svr>
39865 The format of an SVR4 library list is described by this DTD:
39868 <!-- library-list-svr4: Root element with versioning -->
39869 <!ELEMENT library-list-svr4 (library)*>
39870 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39871 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39872 <!ELEMENT library EMPTY>
39873 <!ATTLIST library name CDATA #REQUIRED>
39874 <!ATTLIST library lm CDATA #REQUIRED>
39875 <!ATTLIST library l_addr CDATA #REQUIRED>
39876 <!ATTLIST library l_ld CDATA #REQUIRED>
39879 @node Memory Map Format
39880 @section Memory Map Format
39881 @cindex memory map format
39883 To be able to write into flash memory, @value{GDBN} needs to obtain a
39884 memory map from the target. This section describes the format of the
39887 The memory map is obtained using the @samp{qXfer:memory-map:read}
39888 (@pxref{qXfer memory map read}) packet and is an XML document that
39889 lists memory regions.
39891 @value{GDBN} must be linked with the Expat library to support XML
39892 memory maps. @xref{Expat}.
39894 The top-level structure of the document is shown below:
39897 <?xml version="1.0"?>
39898 <!DOCTYPE memory-map
39899 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39900 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39906 Each region can be either:
39911 A region of RAM starting at @var{addr} and extending for @var{length}
39915 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39920 A region of read-only memory:
39923 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39928 A region of flash memory, with erasure blocks @var{blocksize}
39932 <memory type="flash" start="@var{addr}" length="@var{length}">
39933 <property name="blocksize">@var{blocksize}</property>
39939 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39940 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39941 packets to write to addresses in such ranges.
39943 The formal DTD for memory map format is given below:
39946 <!-- ................................................... -->
39947 <!-- Memory Map XML DTD ................................ -->
39948 <!-- File: memory-map.dtd .............................. -->
39949 <!-- .................................... .............. -->
39950 <!-- memory-map.dtd -->
39951 <!-- memory-map: Root element with versioning -->
39952 <!ELEMENT memory-map (memory | property)>
39953 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39954 <!ELEMENT memory (property)>
39955 <!-- memory: Specifies a memory region,
39956 and its type, or device. -->
39957 <!ATTLIST memory type CDATA #REQUIRED
39958 start CDATA #REQUIRED
39959 length CDATA #REQUIRED
39960 device CDATA #IMPLIED>
39961 <!-- property: Generic attribute tag -->
39962 <!ELEMENT property (#PCDATA | property)*>
39963 <!ATTLIST property name CDATA #REQUIRED>
39966 @node Thread List Format
39967 @section Thread List Format
39968 @cindex thread list format
39970 To efficiently update the list of threads and their attributes,
39971 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39972 (@pxref{qXfer threads read}) and obtains the XML document with
39973 the following structure:
39976 <?xml version="1.0"?>
39978 <thread id="id" core="0" name="name">
39979 ... description ...
39984 Each @samp{thread} element must have the @samp{id} attribute that
39985 identifies the thread (@pxref{thread-id syntax}). The
39986 @samp{core} attribute, if present, specifies which processor core
39987 the thread was last executing on. The @samp{name} attribute, if
39988 present, specifies the human-readable name of the thread. The content
39989 of the of @samp{thread} element is interpreted as human-readable
39990 auxiliary information.
39992 @node Traceframe Info Format
39993 @section Traceframe Info Format
39994 @cindex traceframe info format
39996 To be able to know which objects in the inferior can be examined when
39997 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39998 memory ranges, registers and trace state variables that have been
39999 collected in a traceframe.
40001 This list is obtained using the @samp{qXfer:traceframe-info:read}
40002 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40004 @value{GDBN} must be linked with the Expat library to support XML
40005 traceframe info discovery. @xref{Expat}.
40007 The top-level structure of the document is shown below:
40010 <?xml version="1.0"?>
40011 <!DOCTYPE traceframe-info
40012 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40013 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40019 Each traceframe block can be either:
40024 A region of collected memory starting at @var{addr} and extending for
40025 @var{length} bytes from there:
40028 <memory start="@var{addr}" length="@var{length}"/>
40032 A block indicating trace state variable numbered @var{number} has been
40036 <tvar id="@var{number}"/>
40041 The formal DTD for the traceframe info format is given below:
40044 <!ELEMENT traceframe-info (memory | tvar)* >
40045 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40047 <!ELEMENT memory EMPTY>
40048 <!ATTLIST memory start CDATA #REQUIRED
40049 length CDATA #REQUIRED>
40051 <!ATTLIST tvar id CDATA #REQUIRED>
40054 @node Branch Trace Format
40055 @section Branch Trace Format
40056 @cindex branch trace format
40058 In order to display the branch trace of an inferior thread,
40059 @value{GDBN} needs to obtain the list of branches. This list is
40060 represented as list of sequential code blocks that are connected via
40061 branches. The code in each block has been executed sequentially.
40063 This list is obtained using the @samp{qXfer:btrace:read}
40064 (@pxref{qXfer btrace read}) packet and is an XML document.
40066 @value{GDBN} must be linked with the Expat library to support XML
40067 traceframe info discovery. @xref{Expat}.
40069 The top-level structure of the document is shown below:
40072 <?xml version="1.0"?>
40074 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40075 "http://sourceware.org/gdb/gdb-btrace.dtd">
40084 A block of sequentially executed instructions starting at @var{begin}
40085 and ending at @var{end}:
40088 <block begin="@var{begin}" end="@var{end}"/>
40093 The formal DTD for the branch trace format is given below:
40096 <!ELEMENT btrace (block* | pt) >
40097 <!ATTLIST btrace version CDATA #FIXED "1.0">
40099 <!ELEMENT block EMPTY>
40100 <!ATTLIST block begin CDATA #REQUIRED
40101 end CDATA #REQUIRED>
40103 <!ELEMENT pt (pt-config?, raw?)>
40105 <!ELEMENT pt-config (cpu?)>
40107 <!ELEMENT cpu EMPTY>
40108 <!ATTLIST cpu vendor CDATA #REQUIRED
40109 family CDATA #REQUIRED
40110 model CDATA #REQUIRED
40111 stepping CDATA #REQUIRED>
40113 <!ELEMENT raw (#PCDATA)>
40116 @node Branch Trace Configuration Format
40117 @section Branch Trace Configuration Format
40118 @cindex branch trace configuration format
40120 For each inferior thread, @value{GDBN} can obtain the branch trace
40121 configuration using the @samp{qXfer:btrace-conf:read}
40122 (@pxref{qXfer btrace-conf read}) packet.
40124 The configuration describes the branch trace format and configuration
40125 settings for that format. The following information is described:
40129 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40132 The size of the @acronym{BTS} ring buffer in bytes.
40135 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40139 The size of the @acronym{Intel PT} ring buffer in bytes.
40143 @value{GDBN} must be linked with the Expat library to support XML
40144 branch trace configuration discovery. @xref{Expat}.
40146 The formal DTD for the branch trace configuration format is given below:
40149 <!ELEMENT btrace-conf (bts?, pt?)>
40150 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40152 <!ELEMENT bts EMPTY>
40153 <!ATTLIST bts size CDATA #IMPLIED>
40155 <!ELEMENT pt EMPTY>
40156 <!ATTLIST pt size CDATA #IMPLIED>
40159 @include agentexpr.texi
40161 @node Target Descriptions
40162 @appendix Target Descriptions
40163 @cindex target descriptions
40165 One of the challenges of using @value{GDBN} to debug embedded systems
40166 is that there are so many minor variants of each processor
40167 architecture in use. It is common practice for vendors to start with
40168 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40169 and then make changes to adapt it to a particular market niche. Some
40170 architectures have hundreds of variants, available from dozens of
40171 vendors. This leads to a number of problems:
40175 With so many different customized processors, it is difficult for
40176 the @value{GDBN} maintainers to keep up with the changes.
40178 Since individual variants may have short lifetimes or limited
40179 audiences, it may not be worthwhile to carry information about every
40180 variant in the @value{GDBN} source tree.
40182 When @value{GDBN} does support the architecture of the embedded system
40183 at hand, the task of finding the correct architecture name to give the
40184 @command{set architecture} command can be error-prone.
40187 To address these problems, the @value{GDBN} remote protocol allows a
40188 target system to not only identify itself to @value{GDBN}, but to
40189 actually describe its own features. This lets @value{GDBN} support
40190 processor variants it has never seen before --- to the extent that the
40191 descriptions are accurate, and that @value{GDBN} understands them.
40193 @value{GDBN} must be linked with the Expat library to support XML
40194 target descriptions. @xref{Expat}.
40197 * Retrieving Descriptions:: How descriptions are fetched from a target.
40198 * Target Description Format:: The contents of a target description.
40199 * Predefined Target Types:: Standard types available for target
40201 * Enum Target Types:: How to define enum target types.
40202 * Standard Target Features:: Features @value{GDBN} knows about.
40205 @node Retrieving Descriptions
40206 @section Retrieving Descriptions
40208 Target descriptions can be read from the target automatically, or
40209 specified by the user manually. The default behavior is to read the
40210 description from the target. @value{GDBN} retrieves it via the remote
40211 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40212 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40213 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40214 XML document, of the form described in @ref{Target Description
40217 Alternatively, you can specify a file to read for the target description.
40218 If a file is set, the target will not be queried. The commands to
40219 specify a file are:
40222 @cindex set tdesc filename
40223 @item set tdesc filename @var{path}
40224 Read the target description from @var{path}.
40226 @cindex unset tdesc filename
40227 @item unset tdesc filename
40228 Do not read the XML target description from a file. @value{GDBN}
40229 will use the description supplied by the current target.
40231 @cindex show tdesc filename
40232 @item show tdesc filename
40233 Show the filename to read for a target description, if any.
40237 @node Target Description Format
40238 @section Target Description Format
40239 @cindex target descriptions, XML format
40241 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40242 document which complies with the Document Type Definition provided in
40243 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40244 means you can use generally available tools like @command{xmllint} to
40245 check that your feature descriptions are well-formed and valid.
40246 However, to help people unfamiliar with XML write descriptions for
40247 their targets, we also describe the grammar here.
40249 Target descriptions can identify the architecture of the remote target
40250 and (for some architectures) provide information about custom register
40251 sets. They can also identify the OS ABI of the remote target.
40252 @value{GDBN} can use this information to autoconfigure for your
40253 target, or to warn you if you connect to an unsupported target.
40255 Here is a simple target description:
40258 <target version="1.0">
40259 <architecture>i386:x86-64</architecture>
40264 This minimal description only says that the target uses
40265 the x86-64 architecture.
40267 A target description has the following overall form, with [ ] marking
40268 optional elements and @dots{} marking repeatable elements. The elements
40269 are explained further below.
40272 <?xml version="1.0"?>
40273 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40274 <target version="1.0">
40275 @r{[}@var{architecture}@r{]}
40276 @r{[}@var{osabi}@r{]}
40277 @r{[}@var{compatible}@r{]}
40278 @r{[}@var{feature}@dots{}@r{]}
40283 The description is generally insensitive to whitespace and line
40284 breaks, under the usual common-sense rules. The XML version
40285 declaration and document type declaration can generally be omitted
40286 (@value{GDBN} does not require them), but specifying them may be
40287 useful for XML validation tools. The @samp{version} attribute for
40288 @samp{<target>} may also be omitted, but we recommend
40289 including it; if future versions of @value{GDBN} use an incompatible
40290 revision of @file{gdb-target.dtd}, they will detect and report
40291 the version mismatch.
40293 @subsection Inclusion
40294 @cindex target descriptions, inclusion
40297 @cindex <xi:include>
40300 It can sometimes be valuable to split a target description up into
40301 several different annexes, either for organizational purposes, or to
40302 share files between different possible target descriptions. You can
40303 divide a description into multiple files by replacing any element of
40304 the target description with an inclusion directive of the form:
40307 <xi:include href="@var{document}"/>
40311 When @value{GDBN} encounters an element of this form, it will retrieve
40312 the named XML @var{document}, and replace the inclusion directive with
40313 the contents of that document. If the current description was read
40314 using @samp{qXfer}, then so will be the included document;
40315 @var{document} will be interpreted as the name of an annex. If the
40316 current description was read from a file, @value{GDBN} will look for
40317 @var{document} as a file in the same directory where it found the
40318 original description.
40320 @subsection Architecture
40321 @cindex <architecture>
40323 An @samp{<architecture>} element has this form:
40326 <architecture>@var{arch}</architecture>
40329 @var{arch} is one of the architectures from the set accepted by
40330 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40333 @cindex @code{<osabi>}
40335 This optional field was introduced in @value{GDBN} version 7.0.
40336 Previous versions of @value{GDBN} ignore it.
40338 An @samp{<osabi>} element has this form:
40341 <osabi>@var{abi-name}</osabi>
40344 @var{abi-name} is an OS ABI name from the same selection accepted by
40345 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40347 @subsection Compatible Architecture
40348 @cindex @code{<compatible>}
40350 This optional field was introduced in @value{GDBN} version 7.0.
40351 Previous versions of @value{GDBN} ignore it.
40353 A @samp{<compatible>} element has this form:
40356 <compatible>@var{arch}</compatible>
40359 @var{arch} is one of the architectures from the set accepted by
40360 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40362 A @samp{<compatible>} element is used to specify that the target
40363 is able to run binaries in some other than the main target architecture
40364 given by the @samp{<architecture>} element. For example, on the
40365 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40366 or @code{powerpc:common64}, but the system is able to run binaries
40367 in the @code{spu} architecture as well. The way to describe this
40368 capability with @samp{<compatible>} is as follows:
40371 <architecture>powerpc:common</architecture>
40372 <compatible>spu</compatible>
40375 @subsection Features
40378 Each @samp{<feature>} describes some logical portion of the target
40379 system. Features are currently used to describe available CPU
40380 registers and the types of their contents. A @samp{<feature>} element
40384 <feature name="@var{name}">
40385 @r{[}@var{type}@dots{}@r{]}
40391 Each feature's name should be unique within the description. The name
40392 of a feature does not matter unless @value{GDBN} has some special
40393 knowledge of the contents of that feature; if it does, the feature
40394 should have its standard name. @xref{Standard Target Features}.
40398 Any register's value is a collection of bits which @value{GDBN} must
40399 interpret. The default interpretation is a two's complement integer,
40400 but other types can be requested by name in the register description.
40401 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40402 Target Types}), and the description can define additional composite
40405 Each type element must have an @samp{id} attribute, which gives
40406 a unique (within the containing @samp{<feature>}) name to the type.
40407 Types must be defined before they are used.
40410 Some targets offer vector registers, which can be treated as arrays
40411 of scalar elements. These types are written as @samp{<vector>} elements,
40412 specifying the array element type, @var{type}, and the number of elements,
40416 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40420 If a register's value is usefully viewed in multiple ways, define it
40421 with a union type containing the useful representations. The
40422 @samp{<union>} element contains one or more @samp{<field>} elements,
40423 each of which has a @var{name} and a @var{type}:
40426 <union id="@var{id}">
40427 <field name="@var{name}" type="@var{type}"/>
40434 If a register's value is composed from several separate values, define
40435 it with either a structure type or a flags type.
40436 A flags type may only contain bitfields.
40437 A structure type may either contain only bitfields or contain no bitfields.
40438 If the value contains only bitfields, its total size in bytes must be
40441 Non-bitfield values have a @var{name} and @var{type}.
40444 <struct id="@var{id}">
40445 <field name="@var{name}" type="@var{type}"/>
40450 Both @var{name} and @var{type} values are required.
40451 No implicit padding is added.
40453 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40456 <struct id="@var{id}" size="@var{size}">
40457 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40463 <flags id="@var{id}" size="@var{size}">
40464 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40469 The @var{name} value is required.
40470 Bitfield values may be named with the empty string, @samp{""},
40471 in which case the field is ``filler'' and its value is not printed.
40472 Not all bits need to be specified, so ``filler'' fields are optional.
40474 The @var{start} value is required, and @var{end} and @var{type}
40476 The field's @var{start} must be less than or equal to its @var{end},
40477 and zero represents the least significant bit.
40478 The default value of @var{end} is @var{start}, a single bit field.
40480 The default value of @var{type} depends on whether the
40481 @var{end} was specified. If @var{end} is specified then the default
40482 value of @var{type} is an unsigned integer. If @var{end} is unspecified
40483 then the default value of @var{type} is @code{bool}.
40485 Which to choose? Structures or flags?
40487 Registers defined with @samp{flags} have these advantages over
40488 defining them with @samp{struct}:
40492 Arithmetic may be performed on them as if they were integers.
40494 They are printed in a more readable fashion.
40497 Registers defined with @samp{struct} have one advantage over
40498 defining them with @samp{flags}:
40502 One can fetch individual fields like in @samp{C}.
40505 (gdb) print $my_struct_reg.field3
40511 @subsection Registers
40514 Each register is represented as an element with this form:
40517 <reg name="@var{name}"
40518 bitsize="@var{size}"
40519 @r{[}regnum="@var{num}"@r{]}
40520 @r{[}save-restore="@var{save-restore}"@r{]}
40521 @r{[}type="@var{type}"@r{]}
40522 @r{[}group="@var{group}"@r{]}/>
40526 The components are as follows:
40531 The register's name; it must be unique within the target description.
40534 The register's size, in bits.
40537 The register's number. If omitted, a register's number is one greater
40538 than that of the previous register (either in the current feature or in
40539 a preceding feature); the first register in the target description
40540 defaults to zero. This register number is used to read or write
40541 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40542 packets, and registers appear in the @code{g} and @code{G} packets
40543 in order of increasing register number.
40546 Whether the register should be preserved across inferior function
40547 calls; this must be either @code{yes} or @code{no}. The default is
40548 @code{yes}, which is appropriate for most registers except for
40549 some system control registers; this is not related to the target's
40553 The type of the register. It may be a predefined type, a type
40554 defined in the current feature, or one of the special types @code{int}
40555 and @code{float}. @code{int} is an integer type of the correct size
40556 for @var{bitsize}, and @code{float} is a floating point type (in the
40557 architecture's normal floating point format) of the correct size for
40558 @var{bitsize}. The default is @code{int}.
40561 The register group to which this register belongs. It must
40562 be either @code{general}, @code{float}, or @code{vector}. If no
40563 @var{group} is specified, @value{GDBN} will not display the register
40564 in @code{info registers}.
40568 @node Predefined Target Types
40569 @section Predefined Target Types
40570 @cindex target descriptions, predefined types
40572 Type definitions in the self-description can build up composite types
40573 from basic building blocks, but can not define fundamental types. Instead,
40574 standard identifiers are provided by @value{GDBN} for the fundamental
40575 types. The currently supported types are:
40580 Boolean type, occupying a single bit.
40587 Signed integer types holding the specified number of bits.
40594 Unsigned integer types holding the specified number of bits.
40598 Pointers to unspecified code and data. The program counter and
40599 any dedicated return address register may be marked as code
40600 pointers; printing a code pointer converts it into a symbolic
40601 address. The stack pointer and any dedicated address registers
40602 may be marked as data pointers.
40605 Single precision IEEE floating point.
40608 Double precision IEEE floating point.
40611 The 12-byte extended precision format used by ARM FPA registers.
40614 The 10-byte extended precision format used by x87 registers.
40617 32bit @sc{eflags} register used by x86.
40620 32bit @sc{mxcsr} register used by x86.
40624 @node Enum Target Types
40625 @section Enum Target Types
40626 @cindex target descriptions, enum types
40628 Enum target types are useful in @samp{struct} and @samp{flags}
40629 register descriptions. @xref{Target Description Format}.
40631 Enum types have a name, size and a list of name/value pairs.
40634 <enum id="@var{id}" size="@var{size}">
40635 <evalue name="@var{name}" value="@var{value}"/>
40640 Enums must be defined before they are used.
40643 <enum id="levels_type" size="4">
40644 <evalue name="low" value="0"/>
40645 <evalue name="high" value="1"/>
40647 <flags id="flags_type" size="4">
40648 <field name="X" start="0"/>
40649 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40651 <reg name="flags" bitsize="32" type="flags_type"/>
40654 Given that description, a value of 3 for the @samp{flags} register
40655 would be printed as:
40658 (gdb) info register flags
40659 flags 0x3 [ X LEVEL=high ]
40662 @node Standard Target Features
40663 @section Standard Target Features
40664 @cindex target descriptions, standard features
40666 A target description must contain either no registers or all the
40667 target's registers. If the description contains no registers, then
40668 @value{GDBN} will assume a default register layout, selected based on
40669 the architecture. If the description contains any registers, the
40670 default layout will not be used; the standard registers must be
40671 described in the target description, in such a way that @value{GDBN}
40672 can recognize them.
40674 This is accomplished by giving specific names to feature elements
40675 which contain standard registers. @value{GDBN} will look for features
40676 with those names and verify that they contain the expected registers;
40677 if any known feature is missing required registers, or if any required
40678 feature is missing, @value{GDBN} will reject the target
40679 description. You can add additional registers to any of the
40680 standard features --- @value{GDBN} will display them just as if
40681 they were added to an unrecognized feature.
40683 This section lists the known features and their expected contents.
40684 Sample XML documents for these features are included in the
40685 @value{GDBN} source tree, in the directory @file{gdb/features}.
40687 Names recognized by @value{GDBN} should include the name of the
40688 company or organization which selected the name, and the overall
40689 architecture to which the feature applies; so e.g.@: the feature
40690 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40692 The names of registers are not case sensitive for the purpose
40693 of recognizing standard features, but @value{GDBN} will only display
40694 registers using the capitalization used in the description.
40697 * AArch64 Features::
40700 * MicroBlaze Features::
40703 * Nios II Features::
40704 * PowerPC Features::
40705 * S/390 and System z Features::
40710 @node AArch64 Features
40711 @subsection AArch64 Features
40712 @cindex target descriptions, AArch64 features
40714 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40715 targets. It should contain registers @samp{x0} through @samp{x30},
40716 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40718 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40719 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40723 @subsection ARM Features
40724 @cindex target descriptions, ARM features
40726 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40728 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40729 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40731 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40732 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40733 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40736 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40737 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40739 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40740 it should contain at least registers @samp{wR0} through @samp{wR15} and
40741 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40742 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40744 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40745 should contain at least registers @samp{d0} through @samp{d15}. If
40746 they are present, @samp{d16} through @samp{d31} should also be included.
40747 @value{GDBN} will synthesize the single-precision registers from
40748 halves of the double-precision registers.
40750 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40751 need to contain registers; it instructs @value{GDBN} to display the
40752 VFP double-precision registers as vectors and to synthesize the
40753 quad-precision registers from pairs of double-precision registers.
40754 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40755 be present and include 32 double-precision registers.
40757 @node i386 Features
40758 @subsection i386 Features
40759 @cindex target descriptions, i386 features
40761 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40762 targets. It should describe the following registers:
40766 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40768 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40770 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40771 @samp{fs}, @samp{gs}
40773 @samp{st0} through @samp{st7}
40775 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40776 @samp{foseg}, @samp{fooff} and @samp{fop}
40779 The register sets may be different, depending on the target.
40781 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40782 describe registers:
40786 @samp{xmm0} through @samp{xmm7} for i386
40788 @samp{xmm0} through @samp{xmm15} for amd64
40793 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40794 @samp{org.gnu.gdb.i386.sse} feature. It should
40795 describe the upper 128 bits of @sc{ymm} registers:
40799 @samp{ymm0h} through @samp{ymm7h} for i386
40801 @samp{ymm0h} through @samp{ymm15h} for amd64
40804 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
40805 Memory Protection Extension (MPX). It should describe the following registers:
40809 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40811 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40814 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40815 describe a single register, @samp{orig_eax}.
40817 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40818 @samp{org.gnu.gdb.i386.avx} feature. It should
40819 describe additional @sc{xmm} registers:
40823 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40826 It should describe the upper 128 bits of additional @sc{ymm} registers:
40830 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40834 describe the upper 256 bits of @sc{zmm} registers:
40838 @samp{zmm0h} through @samp{zmm7h} for i386.
40840 @samp{zmm0h} through @samp{zmm15h} for amd64.
40844 describe the additional @sc{zmm} registers:
40848 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40851 @node MicroBlaze Features
40852 @subsection MicroBlaze Features
40853 @cindex target descriptions, MicroBlaze features
40855 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40856 targets. It should contain registers @samp{r0} through @samp{r31},
40857 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40858 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40859 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40861 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40862 If present, it should contain registers @samp{rshr} and @samp{rslr}
40864 @node MIPS Features
40865 @subsection @acronym{MIPS} Features
40866 @cindex target descriptions, @acronym{MIPS} features
40868 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40869 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40870 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40873 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40874 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40875 registers. They may be 32-bit or 64-bit depending on the target.
40877 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40878 it may be optional in a future version of @value{GDBN}. It should
40879 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40880 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40882 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40883 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40884 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40885 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40887 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40888 contain a single register, @samp{restart}, which is used by the
40889 Linux kernel to control restartable syscalls.
40891 @node M68K Features
40892 @subsection M68K Features
40893 @cindex target descriptions, M68K features
40896 @item @samp{org.gnu.gdb.m68k.core}
40897 @itemx @samp{org.gnu.gdb.coldfire.core}
40898 @itemx @samp{org.gnu.gdb.fido.core}
40899 One of those features must be always present.
40900 The feature that is present determines which flavor of m68k is
40901 used. The feature that is present should contain registers
40902 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40903 @samp{sp}, @samp{ps} and @samp{pc}.
40905 @item @samp{org.gnu.gdb.coldfire.fp}
40906 This feature is optional. If present, it should contain registers
40907 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40911 @node Nios II Features
40912 @subsection Nios II Features
40913 @cindex target descriptions, Nios II features
40915 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40916 targets. It should contain the 32 core registers (@samp{zero},
40917 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40918 @samp{pc}, and the 16 control registers (@samp{status} through
40921 @node PowerPC Features
40922 @subsection PowerPC Features
40923 @cindex target descriptions, PowerPC features
40925 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40926 targets. It should contain registers @samp{r0} through @samp{r31},
40927 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40928 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40930 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40931 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40933 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40934 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40937 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40938 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40939 will combine these registers with the floating point registers
40940 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40941 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40942 through @samp{vs63}, the set of vector registers for POWER7.
40944 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40945 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40946 @samp{spefscr}. SPE targets should provide 32-bit registers in
40947 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40948 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40949 these to present registers @samp{ev0} through @samp{ev31} to the
40952 @node S/390 and System z Features
40953 @subsection S/390 and System z Features
40954 @cindex target descriptions, S/390 features
40955 @cindex target descriptions, System z features
40957 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40958 System z targets. It should contain the PSW and the 16 general
40959 registers. In particular, System z targets should provide the 64-bit
40960 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40961 S/390 targets should provide the 32-bit versions of these registers.
40962 A System z target that runs in 31-bit addressing mode should provide
40963 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40964 register's upper halves @samp{r0h} through @samp{r15h}, and their
40965 lower halves @samp{r0l} through @samp{r15l}.
40967 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40968 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40971 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40972 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40974 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40975 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40976 targets and 32-bit otherwise. In addition, the feature may contain
40977 the @samp{last_break} register, whose width depends on the addressing
40978 mode, as well as the @samp{system_call} register, which is always
40981 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40982 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40983 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40985 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40986 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40987 combined by @value{GDBN} with the floating point registers @samp{f0}
40988 through @samp{f15} to present the 128-bit wide vector registers
40989 @samp{v0} through @samp{v15}. In addition, this feature should
40990 contain the 128-bit wide vector registers @samp{v16} through
40993 @node TIC6x Features
40994 @subsection TMS320C6x Features
40995 @cindex target descriptions, TIC6x features
40996 @cindex target descriptions, TMS320C6x features
40997 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40998 targets. It should contain registers @samp{A0} through @samp{A15},
40999 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41001 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41002 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41003 through @samp{B31}.
41005 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41006 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41008 @node Operating System Information
41009 @appendix Operating System Information
41010 @cindex operating system information
41016 Users of @value{GDBN} often wish to obtain information about the state of
41017 the operating system running on the target---for example the list of
41018 processes, or the list of open files. This section describes the
41019 mechanism that makes it possible. This mechanism is similar to the
41020 target features mechanism (@pxref{Target Descriptions}), but focuses
41021 on a different aspect of target.
41023 Operating system information is retrived from the target via the
41024 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41025 read}). The object name in the request should be @samp{osdata}, and
41026 the @var{annex} identifies the data to be fetched.
41029 @appendixsection Process list
41030 @cindex operating system information, process list
41032 When requesting the process list, the @var{annex} field in the
41033 @samp{qXfer} request should be @samp{processes}. The returned data is
41034 an XML document. The formal syntax of this document is defined in
41035 @file{gdb/features/osdata.dtd}.
41037 An example document is:
41040 <?xml version="1.0"?>
41041 <!DOCTYPE target SYSTEM "osdata.dtd">
41042 <osdata type="processes">
41044 <column name="pid">1</column>
41045 <column name="user">root</column>
41046 <column name="command">/sbin/init</column>
41047 <column name="cores">1,2,3</column>
41052 Each item should include a column whose name is @samp{pid}. The value
41053 of that column should identify the process on the target. The
41054 @samp{user} and @samp{command} columns are optional, and will be
41055 displayed by @value{GDBN}. The @samp{cores} column, if present,
41056 should contain a comma-separated list of cores that this process
41057 is running on. Target may provide additional columns,
41058 which @value{GDBN} currently ignores.
41060 @node Trace File Format
41061 @appendix Trace File Format
41062 @cindex trace file format
41064 The trace file comes in three parts: a header, a textual description
41065 section, and a trace frame section with binary data.
41067 The header has the form @code{\x7fTRACE0\n}. The first byte is
41068 @code{0x7f} so as to indicate that the file contains binary data,
41069 while the @code{0} is a version number that may have different values
41072 The description section consists of multiple lines of @sc{ascii} text
41073 separated by newline characters (@code{0xa}). The lines may include a
41074 variety of optional descriptive or context-setting information, such
41075 as tracepoint definitions or register set size. @value{GDBN} will
41076 ignore any line that it does not recognize. An empty line marks the end
41081 Specifies the size of a register block in bytes. This is equal to the
41082 size of a @code{g} packet payload in the remote protocol. @var{size}
41083 is an ascii decimal number. There should be only one such line in
41084 a single trace file.
41086 @item status @var{status}
41087 Trace status. @var{status} has the same format as a @code{qTStatus}
41088 remote packet reply. There should be only one such line in a single trace
41091 @item tp @var{payload}
41092 Tracepoint definition. The @var{payload} has the same format as
41093 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41094 may take multiple lines of definition, corresponding to the multiple
41097 @item tsv @var{payload}
41098 Trace state variable definition. The @var{payload} has the same format as
41099 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41100 may take multiple lines of definition, corresponding to the multiple
41103 @item tdesc @var{payload}
41104 Target description in XML format. The @var{payload} is a single line of
41105 the XML file. All such lines should be concatenated together to get
41106 the original XML file. This file is in the same format as @code{qXfer}
41107 @code{features} payload, and corresponds to the main @code{target.xml}
41108 file. Includes are not allowed.
41112 The trace frame section consists of a number of consecutive frames.
41113 Each frame begins with a two-byte tracepoint number, followed by a
41114 four-byte size giving the amount of data in the frame. The data in
41115 the frame consists of a number of blocks, each introduced by a
41116 character indicating its type (at least register, memory, and trace
41117 state variable). The data in this section is raw binary, not a
41118 hexadecimal or other encoding; its endianness matches the target's
41121 @c FIXME bi-arch may require endianness/arch info in description section
41124 @item R @var{bytes}
41125 Register block. The number and ordering of bytes matches that of a
41126 @code{g} packet in the remote protocol. Note that these are the
41127 actual bytes, in target order, not a hexadecimal encoding.
41129 @item M @var{address} @var{length} @var{bytes}...
41130 Memory block. This is a contiguous block of memory, at the 8-byte
41131 address @var{address}, with a 2-byte length @var{length}, followed by
41132 @var{length} bytes.
41134 @item V @var{number} @var{value}
41135 Trace state variable block. This records the 8-byte signed value
41136 @var{value} of trace state variable numbered @var{number}.
41140 Future enhancements of the trace file format may include additional types
41143 @node Index Section Format
41144 @appendix @code{.gdb_index} section format
41145 @cindex .gdb_index section format
41146 @cindex index section format
41148 This section documents the index section that is created by @code{save
41149 gdb-index} (@pxref{Index Files}). The index section is
41150 DWARF-specific; some knowledge of DWARF is assumed in this
41153 The mapped index file format is designed to be directly
41154 @code{mmap}able on any architecture. In most cases, a datum is
41155 represented using a little-endian 32-bit integer value, called an
41156 @code{offset_type}. Big endian machines must byte-swap the values
41157 before using them. Exceptions to this rule are noted. The data is
41158 laid out such that alignment is always respected.
41160 A mapped index consists of several areas, laid out in order.
41164 The file header. This is a sequence of values, of @code{offset_type}
41165 unless otherwise noted:
41169 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41170 Version 4 uses a different hashing function from versions 5 and 6.
41171 Version 6 includes symbols for inlined functions, whereas versions 4
41172 and 5 do not. Version 7 adds attributes to the CU indices in the
41173 symbol table. Version 8 specifies that symbols from DWARF type units
41174 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41175 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41177 @value{GDBN} will only read version 4, 5, or 6 indices
41178 by specifying @code{set use-deprecated-index-sections on}.
41179 GDB has a workaround for potentially broken version 7 indices so it is
41180 currently not flagged as deprecated.
41183 The offset, from the start of the file, of the CU list.
41186 The offset, from the start of the file, of the types CU list. Note
41187 that this area can be empty, in which case this offset will be equal
41188 to the next offset.
41191 The offset, from the start of the file, of the address area.
41194 The offset, from the start of the file, of the symbol table.
41197 The offset, from the start of the file, of the constant pool.
41201 The CU list. This is a sequence of pairs of 64-bit little-endian
41202 values, sorted by the CU offset. The first element in each pair is
41203 the offset of a CU in the @code{.debug_info} section. The second
41204 element in each pair is the length of that CU. References to a CU
41205 elsewhere in the map are done using a CU index, which is just the
41206 0-based index into this table. Note that if there are type CUs, then
41207 conceptually CUs and type CUs form a single list for the purposes of
41211 The types CU list. This is a sequence of triplets of 64-bit
41212 little-endian values. In a triplet, the first value is the CU offset,
41213 the second value is the type offset in the CU, and the third value is
41214 the type signature. The types CU list is not sorted.
41217 The address area. The address area consists of a sequence of address
41218 entries. Each address entry has three elements:
41222 The low address. This is a 64-bit little-endian value.
41225 The high address. This is a 64-bit little-endian value. Like
41226 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41229 The CU index. This is an @code{offset_type} value.
41233 The symbol table. This is an open-addressed hash table. The size of
41234 the hash table is always a power of 2.
41236 Each slot in the hash table consists of a pair of @code{offset_type}
41237 values. The first value is the offset of the symbol's name in the
41238 constant pool. The second value is the offset of the CU vector in the
41241 If both values are 0, then this slot in the hash table is empty. This
41242 is ok because while 0 is a valid constant pool index, it cannot be a
41243 valid index for both a string and a CU vector.
41245 The hash value for a table entry is computed by applying an
41246 iterative hash function to the symbol's name. Starting with an
41247 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41248 the string is incorporated into the hash using the formula depending on the
41253 The formula is @code{r = r * 67 + c - 113}.
41255 @item Versions 5 to 7
41256 The formula is @code{r = r * 67 + tolower (c) - 113}.
41259 The terminating @samp{\0} is not incorporated into the hash.
41261 The step size used in the hash table is computed via
41262 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41263 value, and @samp{size} is the size of the hash table. The step size
41264 is used to find the next candidate slot when handling a hash
41267 The names of C@t{++} symbols in the hash table are canonicalized. We
41268 don't currently have a simple description of the canonicalization
41269 algorithm; if you intend to create new index sections, you must read
41273 The constant pool. This is simply a bunch of bytes. It is organized
41274 so that alignment is correct: CU vectors are stored first, followed by
41277 A CU vector in the constant pool is a sequence of @code{offset_type}
41278 values. The first value is the number of CU indices in the vector.
41279 Each subsequent value is the index and symbol attributes of a CU in
41280 the CU list. This element in the hash table is used to indicate which
41281 CUs define the symbol and how the symbol is used.
41282 See below for the format of each CU index+attributes entry.
41284 A string in the constant pool is zero-terminated.
41287 Attributes were added to CU index values in @code{.gdb_index} version 7.
41288 If a symbol has multiple uses within a CU then there is one
41289 CU index+attributes value for each use.
41291 The format of each CU index+attributes entry is as follows
41297 This is the index of the CU in the CU list.
41299 These bits are reserved for future purposes and must be zero.
41301 The kind of the symbol in the CU.
41305 This value is reserved and should not be used.
41306 By reserving zero the full @code{offset_type} value is backwards compatible
41307 with previous versions of the index.
41309 The symbol is a type.
41311 The symbol is a variable or an enum value.
41313 The symbol is a function.
41315 Any other kind of symbol.
41317 These values are reserved.
41321 This bit is zero if the value is global and one if it is static.
41323 The determination of whether a symbol is global or static is complicated.
41324 The authorative reference is the file @file{dwarf2read.c} in
41325 @value{GDBN} sources.
41329 This pseudo-code describes the computation of a symbol's kind and
41330 global/static attributes in the index.
41333 is_external = get_attribute (die, DW_AT_external);
41334 language = get_attribute (cu_die, DW_AT_language);
41337 case DW_TAG_typedef:
41338 case DW_TAG_base_type:
41339 case DW_TAG_subrange_type:
41343 case DW_TAG_enumerator:
41345 is_static = (language != CPLUS && language != JAVA);
41347 case DW_TAG_subprogram:
41349 is_static = ! (is_external || language == ADA);
41351 case DW_TAG_constant:
41353 is_static = ! is_external;
41355 case DW_TAG_variable:
41357 is_static = ! is_external;
41359 case DW_TAG_namespace:
41363 case DW_TAG_class_type:
41364 case DW_TAG_interface_type:
41365 case DW_TAG_structure_type:
41366 case DW_TAG_union_type:
41367 case DW_TAG_enumeration_type:
41369 is_static = (language != CPLUS && language != JAVA);
41377 @appendix Manual pages
41381 * gdb man:: The GNU Debugger man page
41382 * gdbserver man:: Remote Server for the GNU Debugger man page
41383 * gcore man:: Generate a core file of a running program
41384 * gdbinit man:: gdbinit scripts
41390 @c man title gdb The GNU Debugger
41392 @c man begin SYNOPSIS gdb
41393 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41394 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41395 [@option{-b}@w{ }@var{bps}]
41396 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41397 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41398 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41399 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41400 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41403 @c man begin DESCRIPTION gdb
41404 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41405 going on ``inside'' another program while it executes -- or what another
41406 program was doing at the moment it crashed.
41408 @value{GDBN} can do four main kinds of things (plus other things in support of
41409 these) to help you catch bugs in the act:
41413 Start your program, specifying anything that might affect its behavior.
41416 Make your program stop on specified conditions.
41419 Examine what has happened, when your program has stopped.
41422 Change things in your program, so you can experiment with correcting the
41423 effects of one bug and go on to learn about another.
41426 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41429 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41430 commands from the terminal until you tell it to exit with the @value{GDBN}
41431 command @code{quit}. You can get online help from @value{GDBN} itself
41432 by using the command @code{help}.
41434 You can run @code{gdb} with no arguments or options; but the most
41435 usual way to start @value{GDBN} is with one argument or two, specifying an
41436 executable program as the argument:
41442 You can also start with both an executable program and a core file specified:
41448 You can, instead, specify a process ID as a second argument, if you want
41449 to debug a running process:
41457 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41458 named @file{1234}; @value{GDBN} does check for a core file first).
41459 With option @option{-p} you can omit the @var{program} filename.
41461 Here are some of the most frequently needed @value{GDBN} commands:
41463 @c pod2man highlights the right hand side of the @item lines.
41465 @item break [@var{file}:]@var{functiop}
41466 Set a breakpoint at @var{function} (in @var{file}).
41468 @item run [@var{arglist}]
41469 Start your program (with @var{arglist}, if specified).
41472 Backtrace: display the program stack.
41474 @item print @var{expr}
41475 Display the value of an expression.
41478 Continue running your program (after stopping, e.g. at a breakpoint).
41481 Execute next program line (after stopping); step @emph{over} any
41482 function calls in the line.
41484 @item edit [@var{file}:]@var{function}
41485 look at the program line where it is presently stopped.
41487 @item list [@var{file}:]@var{function}
41488 type the text of the program in the vicinity of where it is presently stopped.
41491 Execute next program line (after stopping); step @emph{into} any
41492 function calls in the line.
41494 @item help [@var{name}]
41495 Show information about @value{GDBN} command @var{name}, or general information
41496 about using @value{GDBN}.
41499 Exit from @value{GDBN}.
41503 For full details on @value{GDBN},
41504 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41505 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41506 as the @code{gdb} entry in the @code{info} program.
41510 @c man begin OPTIONS gdb
41511 Any arguments other than options specify an executable
41512 file and core file (or process ID); that is, the first argument
41513 encountered with no
41514 associated option flag is equivalent to a @option{-se} option, and the second,
41515 if any, is equivalent to a @option{-c} option if it's the name of a file.
41517 both long and short forms; both are shown here. The long forms are also
41518 recognized if you truncate them, so long as enough of the option is
41519 present to be unambiguous. (If you prefer, you can flag option
41520 arguments with @option{+} rather than @option{-}, though we illustrate the
41521 more usual convention.)
41523 All the options and command line arguments you give are processed
41524 in sequential order. The order makes a difference when the @option{-x}
41530 List all options, with brief explanations.
41532 @item -symbols=@var{file}
41533 @itemx -s @var{file}
41534 Read symbol table from file @var{file}.
41537 Enable writing into executable and core files.
41539 @item -exec=@var{file}
41540 @itemx -e @var{file}
41541 Use file @var{file} as the executable file to execute when
41542 appropriate, and for examining pure data in conjunction with a core
41545 @item -se=@var{file}
41546 Read symbol table from file @var{file} and use it as the executable
41549 @item -core=@var{file}
41550 @itemx -c @var{file}
41551 Use file @var{file} as a core dump to examine.
41553 @item -command=@var{file}
41554 @itemx -x @var{file}
41555 Execute @value{GDBN} commands from file @var{file}.
41557 @item -ex @var{command}
41558 Execute given @value{GDBN} @var{command}.
41560 @item -directory=@var{directory}
41561 @itemx -d @var{directory}
41562 Add @var{directory} to the path to search for source files.
41565 Do not execute commands from @file{~/.gdbinit}.
41569 Do not execute commands from any @file{.gdbinit} initialization files.
41573 ``Quiet''. Do not print the introductory and copyright messages. These
41574 messages are also suppressed in batch mode.
41577 Run in batch mode. Exit with status @code{0} after processing all the command
41578 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41579 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41580 commands in the command files.
41582 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41583 download and run a program on another computer; in order to make this
41584 more useful, the message
41587 Program exited normally.
41591 (which is ordinarily issued whenever a program running under @value{GDBN} control
41592 terminates) is not issued when running in batch mode.
41594 @item -cd=@var{directory}
41595 Run @value{GDBN} using @var{directory} as its working directory,
41596 instead of the current directory.
41600 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41601 @value{GDBN} to output the full file name and line number in a standard,
41602 recognizable fashion each time a stack frame is displayed (which
41603 includes each time the program stops). This recognizable format looks
41604 like two @samp{\032} characters, followed by the file name, line number
41605 and character position separated by colons, and a newline. The
41606 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41607 characters as a signal to display the source code for the frame.
41610 Set the line speed (baud rate or bits per second) of any serial
41611 interface used by @value{GDBN} for remote debugging.
41613 @item -tty=@var{device}
41614 Run using @var{device} for your program's standard input and output.
41618 @c man begin SEEALSO gdb
41620 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41621 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41622 documentation are properly installed at your site, the command
41629 should give you access to the complete manual.
41631 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41632 Richard M. Stallman and Roland H. Pesch, July 1991.
41636 @node gdbserver man
41637 @heading gdbserver man
41639 @c man title gdbserver Remote Server for the GNU Debugger
41641 @c man begin SYNOPSIS gdbserver
41642 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41644 gdbserver --attach @var{comm} @var{pid}
41646 gdbserver --multi @var{comm}
41650 @c man begin DESCRIPTION gdbserver
41651 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41652 than the one which is running the program being debugged.
41655 @subheading Usage (server (target) side)
41658 Usage (server (target) side):
41661 First, you need to have a copy of the program you want to debug put onto
41662 the target system. The program can be stripped to save space if needed, as
41663 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41664 the @value{GDBN} running on the host system.
41666 To use the server, you log on to the target system, and run the @command{gdbserver}
41667 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41668 your program, and (c) its arguments. The general syntax is:
41671 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41674 For example, using a serial port, you might say:
41678 @c @file would wrap it as F</dev/com1>.
41679 target> gdbserver /dev/com1 emacs foo.txt
41682 target> gdbserver @file{/dev/com1} emacs foo.txt
41686 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41687 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41688 waits patiently for the host @value{GDBN} to communicate with it.
41690 To use a TCP connection, you could say:
41693 target> gdbserver host:2345 emacs foo.txt
41696 This says pretty much the same thing as the last example, except that we are
41697 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41698 that we are expecting to see a TCP connection from @code{host} to local TCP port
41699 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41700 want for the port number as long as it does not conflict with any existing TCP
41701 ports on the target system. This same port number must be used in the host
41702 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41703 you chose a port number that conflicts with another service, @command{gdbserver} will
41704 print an error message and exit.
41706 @command{gdbserver} can also attach to running programs.
41707 This is accomplished via the @option{--attach} argument. The syntax is:
41710 target> gdbserver --attach @var{comm} @var{pid}
41713 @var{pid} is the process ID of a currently running process. It isn't
41714 necessary to point @command{gdbserver} at a binary for the running process.
41716 To start @code{gdbserver} without supplying an initial command to run
41717 or process ID to attach, use the @option{--multi} command line option.
41718 In such case you should connect using @kbd{target extended-remote} to start
41719 the program you want to debug.
41722 target> gdbserver --multi @var{comm}
41726 @subheading Usage (host side)
41732 You need an unstripped copy of the target program on your host system, since
41733 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41734 would, with the target program as the first argument. (You may need to use the
41735 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41736 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41737 new command you need to know about is @code{target remote}
41738 (or @code{target extended-remote}). Its argument is either
41739 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41740 descriptor. For example:
41744 @c @file would wrap it as F</dev/ttyb>.
41745 (gdb) target remote /dev/ttyb
41748 (gdb) target remote @file{/dev/ttyb}
41753 communicates with the server via serial line @file{/dev/ttyb}, and:
41756 (gdb) target remote the-target:2345
41760 communicates via a TCP connection to port 2345 on host `the-target', where
41761 you previously started up @command{gdbserver} with the same port number. Note that for
41762 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41763 command, otherwise you may get an error that looks something like
41764 `Connection refused'.
41766 @command{gdbserver} can also debug multiple inferiors at once,
41769 the @value{GDBN} manual in node @code{Inferiors and Programs}
41770 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41773 @ref{Inferiors and Programs}.
41775 In such case use the @code{extended-remote} @value{GDBN} command variant:
41778 (gdb) target extended-remote the-target:2345
41781 The @command{gdbserver} option @option{--multi} may or may not be used in such
41785 @c man begin OPTIONS gdbserver
41786 There are three different modes for invoking @command{gdbserver}:
41791 Debug a specific program specified by its program name:
41794 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41797 The @var{comm} parameter specifies how should the server communicate
41798 with @value{GDBN}; it is either a device name (to use a serial line),
41799 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41800 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41801 debug in @var{prog}. Any remaining arguments will be passed to the
41802 program verbatim. When the program exits, @value{GDBN} will close the
41803 connection, and @code{gdbserver} will exit.
41806 Debug a specific program by specifying the process ID of a running
41810 gdbserver --attach @var{comm} @var{pid}
41813 The @var{comm} parameter is as described above. Supply the process ID
41814 of a running program in @var{pid}; @value{GDBN} will do everything
41815 else. Like with the previous mode, when the process @var{pid} exits,
41816 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41819 Multi-process mode -- debug more than one program/process:
41822 gdbserver --multi @var{comm}
41825 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41826 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41827 close the connection when a process being debugged exits, so you can
41828 debug several processes in the same session.
41831 In each of the modes you may specify these options:
41836 List all options, with brief explanations.
41839 This option causes @command{gdbserver} to print its version number and exit.
41842 @command{gdbserver} will attach to a running program. The syntax is:
41845 target> gdbserver --attach @var{comm} @var{pid}
41848 @var{pid} is the process ID of a currently running process. It isn't
41849 necessary to point @command{gdbserver} at a binary for the running process.
41852 To start @code{gdbserver} without supplying an initial command to run
41853 or process ID to attach, use this command line option.
41854 Then you can connect using @kbd{target extended-remote} and start
41855 the program you want to debug. The syntax is:
41858 target> gdbserver --multi @var{comm}
41862 Instruct @code{gdbserver} to display extra status information about the debugging
41864 This option is intended for @code{gdbserver} development and for bug reports to
41867 @item --remote-debug
41868 Instruct @code{gdbserver} to display remote protocol debug output.
41869 This option is intended for @code{gdbserver} development and for bug reports to
41872 @item --debug-format=option1@r{[},option2,...@r{]}
41873 Instruct @code{gdbserver} to include extra information in each line
41874 of debugging output.
41875 @xref{Other Command-Line Arguments for gdbserver}.
41878 Specify a wrapper to launch programs
41879 for debugging. The option should be followed by the name of the
41880 wrapper, then any command-line arguments to pass to the wrapper, then
41881 @kbd{--} indicating the end of the wrapper arguments.
41884 By default, @command{gdbserver} keeps the listening TCP port open, so that
41885 additional connections are possible. However, if you start @code{gdbserver}
41886 with the @option{--once} option, it will stop listening for any further
41887 connection attempts after connecting to the first @value{GDBN} session.
41889 @c --disable-packet is not documented for users.
41891 @c --disable-randomization and --no-disable-randomization are superseded by
41892 @c QDisableRandomization.
41897 @c man begin SEEALSO gdbserver
41899 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41900 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41901 documentation are properly installed at your site, the command
41907 should give you access to the complete manual.
41909 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41910 Richard M. Stallman and Roland H. Pesch, July 1991.
41917 @c man title gcore Generate a core file of a running program
41920 @c man begin SYNOPSIS gcore
41921 gcore [-o @var{filename}] @var{pid}
41925 @c man begin DESCRIPTION gcore
41926 Generate a core dump of a running program with process ID @var{pid}.
41927 Produced file is equivalent to a kernel produced core file as if the process
41928 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41929 limit). Unlike after a crash, after @command{gcore} the program remains
41930 running without any change.
41933 @c man begin OPTIONS gcore
41935 @item -o @var{filename}
41936 The optional argument
41937 @var{filename} specifies the file name where to put the core dump.
41938 If not specified, the file name defaults to @file{core.@var{pid}},
41939 where @var{pid} is the running program process ID.
41943 @c man begin SEEALSO gcore
41945 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41946 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41947 documentation are properly installed at your site, the command
41954 should give you access to the complete manual.
41956 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41957 Richard M. Stallman and Roland H. Pesch, July 1991.
41964 @c man title gdbinit GDB initialization scripts
41967 @c man begin SYNOPSIS gdbinit
41968 @ifset SYSTEM_GDBINIT
41969 @value{SYSTEM_GDBINIT}
41978 @c man begin DESCRIPTION gdbinit
41979 These files contain @value{GDBN} commands to automatically execute during
41980 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41983 the @value{GDBN} manual in node @code{Sequences}
41984 -- shell command @code{info -f gdb -n Sequences}.
41990 Please read more in
41992 the @value{GDBN} manual in node @code{Startup}
41993 -- shell command @code{info -f gdb -n Startup}.
42000 @ifset SYSTEM_GDBINIT
42001 @item @value{SYSTEM_GDBINIT}
42003 @ifclear SYSTEM_GDBINIT
42004 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42006 System-wide initialization file. It is executed unless user specified
42007 @value{GDBN} option @code{-nx} or @code{-n}.
42010 the @value{GDBN} manual in node @code{System-wide configuration}
42011 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42014 @ref{System-wide configuration}.
42018 User initialization file. It is executed unless user specified
42019 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42022 Initialization file for current directory. It may need to be enabled with
42023 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42026 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42027 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42030 @ref{Init File in the Current Directory}.
42035 @c man begin SEEALSO gdbinit
42037 gdb(1), @code{info -f gdb -n Startup}
42039 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42040 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42041 documentation are properly installed at your site, the command
42047 should give you access to the complete manual.
42049 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42050 Richard M. Stallman and Roland H. Pesch, July 1991.
42056 @node GNU Free Documentation License
42057 @appendix GNU Free Documentation License
42060 @node Concept Index
42061 @unnumbered Concept Index
42065 @node Command and Variable Index
42066 @unnumbered Command, Variable, and Function Index
42071 % I think something like @@colophon should be in texinfo. In the
42073 \long\def\colophon{\hbox to0pt{}\vfill
42074 \centerline{The body of this manual is set in}
42075 \centerline{\fontname\tenrm,}
42076 \centerline{with headings in {\bf\fontname\tenbf}}
42077 \centerline{and examples in {\tt\fontname\tentt}.}
42078 \centerline{{\it\fontname\tenit\/},}
42079 \centerline{{\bf\fontname\tenbf}, and}
42080 \centerline{{\sl\fontname\tensl\/}}
42081 \centerline{are used for emphasis.}\vfill}
42083 % Blame: doc@@cygnus.com, 1991.