1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 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{} 1988-2014 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) 1988-2014 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}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @itemx -D @var{directory}
1168 @cindex @code{--data-directory}
1170 Run @value{GDBN} using @var{directory} as its data directory.
1171 The data directory is where @value{GDBN} searches for its
1172 auxiliary files. @xref{Data Files}.
1176 @cindex @code{--fullname}
1178 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1179 subprocess. It tells @value{GDBN} to output the full file name and line
1180 number in a standard, recognizable fashion each time a stack frame is
1181 displayed (which includes each time your program stops). This
1182 recognizable format looks like two @samp{\032} characters, followed by
1183 the file name, line number and character position separated by colons,
1184 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1185 @samp{\032} characters as a signal to display the source code for the
1188 @item -annotate @var{level}
1189 @cindex @code{--annotate}
1190 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1191 effect is identical to using @samp{set annotate @var{level}}
1192 (@pxref{Annotations}). The annotation @var{level} controls how much
1193 information @value{GDBN} prints together with its prompt, values of
1194 expressions, source lines, and other types of output. Level 0 is the
1195 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1196 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1197 that control @value{GDBN}, and level 2 has been deprecated.
1199 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1203 @cindex @code{--args}
1204 Change interpretation of command line so that arguments following the
1205 executable file are passed as command line arguments to the inferior.
1206 This option stops option processing.
1208 @item -baud @var{bps}
1210 @cindex @code{--baud}
1212 Set the line speed (baud rate or bits per second) of any serial
1213 interface used by @value{GDBN} for remote debugging.
1215 @item -l @var{timeout}
1217 Set the timeout (in seconds) of any communication used by @value{GDBN}
1218 for remote debugging.
1220 @item -tty @var{device}
1221 @itemx -t @var{device}
1222 @cindex @code{--tty}
1224 Run using @var{device} for your program's standard input and output.
1225 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1227 @c resolve the situation of these eventually
1229 @cindex @code{--tui}
1230 Activate the @dfn{Text User Interface} when starting. The Text User
1231 Interface manages several text windows on the terminal, showing
1232 source, assembly, registers and @value{GDBN} command outputs
1233 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1234 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1235 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @c @cindex @code{--xdb}
1239 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1240 @c For information, see the file @file{xdb_trans.html}, which is usually
1241 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1244 @item -interpreter @var{interp}
1245 @cindex @code{--interpreter}
1246 Use the interpreter @var{interp} for interface with the controlling
1247 program or device. This option is meant to be set by programs which
1248 communicate with @value{GDBN} using it as a back end.
1249 @xref{Interpreters, , Command Interpreters}.
1251 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1252 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1253 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1254 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1255 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1256 @sc{gdb/mi} interfaces are no longer supported.
1259 @cindex @code{--write}
1260 Open the executable and core files for both reading and writing. This
1261 is equivalent to the @samp{set write on} command inside @value{GDBN}
1265 @cindex @code{--statistics}
1266 This option causes @value{GDBN} to print statistics about time and
1267 memory usage after it completes each command and returns to the prompt.
1270 @cindex @code{--version}
1271 This option causes @value{GDBN} to print its version number and
1272 no-warranty blurb, and exit.
1274 @item -configuration
1275 @cindex @code{--configuration}
1276 This option causes @value{GDBN} to print details about its build-time
1277 configuration parameters, and then exit. These details can be
1278 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1283 @subsection What @value{GDBN} Does During Startup
1284 @cindex @value{GDBN} startup
1286 Here's the description of what @value{GDBN} does during session startup:
1290 Sets up the command interpreter as specified by the command line
1291 (@pxref{Mode Options, interpreter}).
1295 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1296 used when building @value{GDBN}; @pxref{System-wide configuration,
1297 ,System-wide configuration and settings}) and executes all the commands in
1300 @anchor{Home Directory Init File}
1302 Reads the init file (if any) in your home directory@footnote{On
1303 DOS/Windows systems, the home directory is the one pointed to by the
1304 @code{HOME} environment variable.} and executes all the commands in
1307 @anchor{Option -init-eval-command}
1309 Executes commands and command files specified by the @samp{-iex} and
1310 @samp{-ix} options in their specified order. Usually you should use the
1311 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1312 settings before @value{GDBN} init files get executed and before inferior
1316 Processes command line options and operands.
1318 @anchor{Init File in the Current Directory during Startup}
1320 Reads and executes the commands from init file (if any) in the current
1321 working directory as long as @samp{set auto-load local-gdbinit} is set to
1322 @samp{on} (@pxref{Init File in the Current Directory}).
1323 This is only done if the current directory is
1324 different from your home directory. Thus, you can have more than one
1325 init file, one generic in your home directory, and another, specific
1326 to the program you are debugging, in the directory where you invoke
1330 If the command line specified a program to debug, or a process to
1331 attach to, or a core file, @value{GDBN} loads any auto-loaded
1332 scripts provided for the program or for its loaded shared libraries.
1333 @xref{Auto-loading}.
1335 If you wish to disable the auto-loading during startup,
1336 you must do something like the following:
1339 $ gdb -iex "set auto-load python-scripts off" myprogram
1342 Option @samp{-ex} does not work because the auto-loading is then turned
1346 Executes commands and command files specified by the @samp{-ex} and
1347 @samp{-x} options in their specified order. @xref{Command Files}, for
1348 more details about @value{GDBN} command files.
1351 Reads the command history recorded in the @dfn{history file}.
1352 @xref{Command History}, for more details about the command history and the
1353 files where @value{GDBN} records it.
1356 Init files use the same syntax as @dfn{command files} (@pxref{Command
1357 Files}) and are processed by @value{GDBN} in the same way. The init
1358 file in your home directory can set options (such as @samp{set
1359 complaints}) that affect subsequent processing of command line options
1360 and operands. Init files are not executed if you use the @samp{-nx}
1361 option (@pxref{Mode Options, ,Choosing Modes}).
1363 To display the list of init files loaded by gdb at startup, you
1364 can use @kbd{gdb --help}.
1366 @cindex init file name
1367 @cindex @file{.gdbinit}
1368 @cindex @file{gdb.ini}
1369 The @value{GDBN} init files are normally called @file{.gdbinit}.
1370 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1371 the limitations of file names imposed by DOS filesystems. The Windows
1372 port of @value{GDBN} uses the standard name, but if it finds a
1373 @file{gdb.ini} file in your home directory, it warns you about that
1374 and suggests to rename the file to the standard name.
1378 @section Quitting @value{GDBN}
1379 @cindex exiting @value{GDBN}
1380 @cindex leaving @value{GDBN}
1383 @kindex quit @r{[}@var{expression}@r{]}
1384 @kindex q @r{(@code{quit})}
1385 @item quit @r{[}@var{expression}@r{]}
1387 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1388 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1389 do not supply @var{expression}, @value{GDBN} will terminate normally;
1390 otherwise it will terminate using the result of @var{expression} as the
1395 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1396 terminates the action of any @value{GDBN} command that is in progress and
1397 returns to @value{GDBN} command level. It is safe to type the interrupt
1398 character at any time because @value{GDBN} does not allow it to take effect
1399 until a time when it is safe.
1401 If you have been using @value{GDBN} to control an attached process or
1402 device, you can release it with the @code{detach} command
1403 (@pxref{Attach, ,Debugging an Already-running Process}).
1405 @node Shell Commands
1406 @section Shell Commands
1408 If you need to execute occasional shell commands during your
1409 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1410 just use the @code{shell} command.
1415 @cindex shell escape
1416 @item shell @var{command-string}
1417 @itemx !@var{command-string}
1418 Invoke a standard shell to execute @var{command-string}.
1419 Note that no space is needed between @code{!} and @var{command-string}.
1420 If it exists, the environment variable @code{SHELL} determines which
1421 shell to run. Otherwise @value{GDBN} uses the default shell
1422 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1425 The utility @code{make} is often needed in development environments.
1426 You do not have to use the @code{shell} command for this purpose in
1431 @cindex calling make
1432 @item make @var{make-args}
1433 Execute the @code{make} program with the specified
1434 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1437 @node Logging Output
1438 @section Logging Output
1439 @cindex logging @value{GDBN} output
1440 @cindex save @value{GDBN} output to a file
1442 You may want to save the output of @value{GDBN} commands to a file.
1443 There are several commands to control @value{GDBN}'s logging.
1447 @item set logging on
1449 @item set logging off
1451 @cindex logging file name
1452 @item set logging file @var{file}
1453 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1454 @item set logging overwrite [on|off]
1455 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1456 you want @code{set logging on} to overwrite the logfile instead.
1457 @item set logging redirect [on|off]
1458 By default, @value{GDBN} output will go to both the terminal and the logfile.
1459 Set @code{redirect} if you want output to go only to the log file.
1460 @kindex show logging
1462 Show the current values of the logging settings.
1466 @chapter @value{GDBN} Commands
1468 You can abbreviate a @value{GDBN} command to the first few letters of the command
1469 name, if that abbreviation is unambiguous; and you can repeat certain
1470 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1471 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1472 show you the alternatives available, if there is more than one possibility).
1475 * Command Syntax:: How to give commands to @value{GDBN}
1476 * Completion:: Command completion
1477 * Help:: How to ask @value{GDBN} for help
1480 @node Command Syntax
1481 @section Command Syntax
1483 A @value{GDBN} command is a single line of input. There is no limit on
1484 how long it can be. It starts with a command name, which is followed by
1485 arguments whose meaning depends on the command name. For example, the
1486 command @code{step} accepts an argument which is the number of times to
1487 step, as in @samp{step 5}. You can also use the @code{step} command
1488 with no arguments. Some commands do not allow any arguments.
1490 @cindex abbreviation
1491 @value{GDBN} command names may always be truncated if that abbreviation is
1492 unambiguous. Other possible command abbreviations are listed in the
1493 documentation for individual commands. In some cases, even ambiguous
1494 abbreviations are allowed; for example, @code{s} is specially defined as
1495 equivalent to @code{step} even though there are other commands whose
1496 names start with @code{s}. You can test abbreviations by using them as
1497 arguments to the @code{help} command.
1499 @cindex repeating commands
1500 @kindex RET @r{(repeat last command)}
1501 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1502 repeat the previous command. Certain commands (for example, @code{run})
1503 will not repeat this way; these are commands whose unintentional
1504 repetition might cause trouble and which you are unlikely to want to
1505 repeat. User-defined commands can disable this feature; see
1506 @ref{Define, dont-repeat}.
1508 The @code{list} and @code{x} commands, when you repeat them with
1509 @key{RET}, construct new arguments rather than repeating
1510 exactly as typed. This permits easy scanning of source or memory.
1512 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1513 output, in a way similar to the common utility @code{more}
1514 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1515 @key{RET} too many in this situation, @value{GDBN} disables command
1516 repetition after any command that generates this sort of display.
1518 @kindex # @r{(a comment)}
1520 Any text from a @kbd{#} to the end of the line is a comment; it does
1521 nothing. This is useful mainly in command files (@pxref{Command
1522 Files,,Command Files}).
1524 @cindex repeating command sequences
1525 @kindex Ctrl-o @r{(operate-and-get-next)}
1526 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1527 commands. This command accepts the current line, like @key{RET}, and
1528 then fetches the next line relative to the current line from the history
1532 @section Command Completion
1535 @cindex word completion
1536 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1537 only one possibility; it can also show you what the valid possibilities
1538 are for the next word in a command, at any time. This works for @value{GDBN}
1539 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1541 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1542 of a word. If there is only one possibility, @value{GDBN} fills in the
1543 word, and waits for you to finish the command (or press @key{RET} to
1544 enter it). For example, if you type
1546 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1547 @c complete accuracy in these examples; space introduced for clarity.
1548 @c If texinfo enhancements make it unnecessary, it would be nice to
1549 @c replace " @key" by "@key" in the following...
1551 (@value{GDBP}) info bre @key{TAB}
1555 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1556 the only @code{info} subcommand beginning with @samp{bre}:
1559 (@value{GDBP}) info breakpoints
1563 You can either press @key{RET} at this point, to run the @code{info
1564 breakpoints} command, or backspace and enter something else, if
1565 @samp{breakpoints} does not look like the command you expected. (If you
1566 were sure you wanted @code{info breakpoints} in the first place, you
1567 might as well just type @key{RET} immediately after @samp{info bre},
1568 to exploit command abbreviations rather than command completion).
1570 If there is more than one possibility for the next word when you press
1571 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1572 characters and try again, or just press @key{TAB} a second time;
1573 @value{GDBN} displays all the possible completions for that word. For
1574 example, you might want to set a breakpoint on a subroutine whose name
1575 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1576 just sounds the bell. Typing @key{TAB} again displays all the
1577 function names in your program that begin with those characters, for
1581 (@value{GDBP}) b make_ @key{TAB}
1582 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1583 make_a_section_from_file make_environ
1584 make_abs_section make_function_type
1585 make_blockvector make_pointer_type
1586 make_cleanup make_reference_type
1587 make_command make_symbol_completion_list
1588 (@value{GDBP}) b make_
1592 After displaying the available possibilities, @value{GDBN} copies your
1593 partial input (@samp{b make_} in the example) so you can finish the
1596 If you just want to see the list of alternatives in the first place, you
1597 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1598 means @kbd{@key{META} ?}. You can type this either by holding down a
1599 key designated as the @key{META} shift on your keyboard (if there is
1600 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1602 @cindex quotes in commands
1603 @cindex completion of quoted strings
1604 Sometimes the string you need, while logically a ``word'', may contain
1605 parentheses or other characters that @value{GDBN} normally excludes from
1606 its notion of a word. To permit word completion to work in this
1607 situation, you may enclose words in @code{'} (single quote marks) in
1608 @value{GDBN} commands.
1610 The most likely situation where you might need this is in typing the
1611 name of a C@t{++} function. This is because C@t{++} allows function
1612 overloading (multiple definitions of the same function, distinguished
1613 by argument type). For example, when you want to set a breakpoint you
1614 may need to distinguish whether you mean the version of @code{name}
1615 that takes an @code{int} parameter, @code{name(int)}, or the version
1616 that takes a @code{float} parameter, @code{name(float)}. To use the
1617 word-completion facilities in this situation, type a single quote
1618 @code{'} at the beginning of the function name. This alerts
1619 @value{GDBN} that it may need to consider more information than usual
1620 when you press @key{TAB} or @kbd{M-?} to request word completion:
1623 (@value{GDBP}) b 'bubble( @kbd{M-?}
1624 bubble(double,double) bubble(int,int)
1625 (@value{GDBP}) b 'bubble(
1628 In some cases, @value{GDBN} can tell that completing a name requires using
1629 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1630 completing as much as it can) if you do not type the quote in the first
1634 (@value{GDBP}) b bub @key{TAB}
1635 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1636 (@value{GDBP}) b 'bubble(
1640 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1641 you have not yet started typing the argument list when you ask for
1642 completion on an overloaded symbol.
1644 For more information about overloaded functions, see @ref{C Plus Plus
1645 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1646 overload-resolution off} to disable overload resolution;
1647 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1649 @cindex completion of structure field names
1650 @cindex structure field name completion
1651 @cindex completion of union field names
1652 @cindex union field name completion
1653 When completing in an expression which looks up a field in a
1654 structure, @value{GDBN} also tries@footnote{The completer can be
1655 confused by certain kinds of invalid expressions. Also, it only
1656 examines the static type of the expression, not the dynamic type.} to
1657 limit completions to the field names available in the type of the
1661 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1662 magic to_fputs to_rewind
1663 to_data to_isatty to_write
1664 to_delete to_put to_write_async_safe
1669 This is because the @code{gdb_stdout} is a variable of the type
1670 @code{struct ui_file} that is defined in @value{GDBN} sources as
1677 ui_file_flush_ftype *to_flush;
1678 ui_file_write_ftype *to_write;
1679 ui_file_write_async_safe_ftype *to_write_async_safe;
1680 ui_file_fputs_ftype *to_fputs;
1681 ui_file_read_ftype *to_read;
1682 ui_file_delete_ftype *to_delete;
1683 ui_file_isatty_ftype *to_isatty;
1684 ui_file_rewind_ftype *to_rewind;
1685 ui_file_put_ftype *to_put;
1692 @section Getting Help
1693 @cindex online documentation
1696 You can always ask @value{GDBN} itself for information on its commands,
1697 using the command @code{help}.
1700 @kindex h @r{(@code{help})}
1703 You can use @code{help} (abbreviated @code{h}) with no arguments to
1704 display a short list of named classes of commands:
1708 List of classes of commands:
1710 aliases -- Aliases of other commands
1711 breakpoints -- Making program stop at certain points
1712 data -- Examining data
1713 files -- Specifying and examining files
1714 internals -- Maintenance commands
1715 obscure -- Obscure features
1716 running -- Running the program
1717 stack -- Examining the stack
1718 status -- Status inquiries
1719 support -- Support facilities
1720 tracepoints -- Tracing of program execution without
1721 stopping the program
1722 user-defined -- User-defined commands
1724 Type "help" followed by a class name for a list of
1725 commands in that class.
1726 Type "help" followed by command name for full
1728 Command name abbreviations are allowed if unambiguous.
1731 @c the above line break eliminates huge line overfull...
1733 @item help @var{class}
1734 Using one of the general help classes as an argument, you can get a
1735 list of the individual commands in that class. For example, here is the
1736 help display for the class @code{status}:
1739 (@value{GDBP}) help status
1744 @c Line break in "show" line falsifies real output, but needed
1745 @c to fit in smallbook page size.
1746 info -- Generic command for showing things
1747 about the program being debugged
1748 show -- Generic command for showing things
1751 Type "help" followed by command name for full
1753 Command name abbreviations are allowed if unambiguous.
1757 @item help @var{command}
1758 With a command name as @code{help} argument, @value{GDBN} displays a
1759 short paragraph on how to use that command.
1762 @item apropos @var{args}
1763 The @code{apropos} command searches through all of the @value{GDBN}
1764 commands, and their documentation, for the regular expression specified in
1765 @var{args}. It prints out all matches found. For example:
1776 alias -- Define a new command that is an alias of an existing command
1777 aliases -- Aliases of other commands
1778 d -- Delete some breakpoints or auto-display expressions
1779 del -- Delete some breakpoints or auto-display expressions
1780 delete -- Delete some breakpoints or auto-display expressions
1785 @item complete @var{args}
1786 The @code{complete @var{args}} command lists all the possible completions
1787 for the beginning of a command. Use @var{args} to specify the beginning of the
1788 command you want completed. For example:
1794 @noindent results in:
1805 @noindent This is intended for use by @sc{gnu} Emacs.
1808 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1809 and @code{show} to inquire about the state of your program, or the state
1810 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1811 manual introduces each of them in the appropriate context. The listings
1812 under @code{info} and under @code{show} in the Command, Variable, and
1813 Function Index point to all the sub-commands. @xref{Command and Variable
1819 @kindex i @r{(@code{info})}
1821 This command (abbreviated @code{i}) is for describing the state of your
1822 program. For example, you can show the arguments passed to a function
1823 with @code{info args}, list the registers currently in use with @code{info
1824 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1825 You can get a complete list of the @code{info} sub-commands with
1826 @w{@code{help info}}.
1830 You can assign the result of an expression to an environment variable with
1831 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1832 @code{set prompt $}.
1836 In contrast to @code{info}, @code{show} is for describing the state of
1837 @value{GDBN} itself.
1838 You can change most of the things you can @code{show}, by using the
1839 related command @code{set}; for example, you can control what number
1840 system is used for displays with @code{set radix}, or simply inquire
1841 which is currently in use with @code{show radix}.
1844 To display all the settable parameters and their current
1845 values, you can use @code{show} with no arguments; you may also use
1846 @code{info set}. Both commands produce the same display.
1847 @c FIXME: "info set" violates the rule that "info" is for state of
1848 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1849 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1853 Here are several miscellaneous @code{show} subcommands, all of which are
1854 exceptional in lacking corresponding @code{set} commands:
1857 @kindex show version
1858 @cindex @value{GDBN} version number
1860 Show what version of @value{GDBN} is running. You should include this
1861 information in @value{GDBN} bug-reports. If multiple versions of
1862 @value{GDBN} are in use at your site, you may need to determine which
1863 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1864 commands are introduced, and old ones may wither away. Also, many
1865 system vendors ship variant versions of @value{GDBN}, and there are
1866 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1867 The version number is the same as the one announced when you start
1870 @kindex show copying
1871 @kindex info copying
1872 @cindex display @value{GDBN} copyright
1875 Display information about permission for copying @value{GDBN}.
1877 @kindex show warranty
1878 @kindex info warranty
1880 @itemx info warranty
1881 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1882 if your version of @value{GDBN} comes with one.
1884 @kindex show configuration
1885 @item show configuration
1886 Display detailed information about the way @value{GDBN} was configured
1887 when it was built. This displays the optional arguments passed to the
1888 @file{configure} script and also configuration parameters detected
1889 automatically by @command{configure}. When reporting a @value{GDBN}
1890 bug (@pxref{GDB Bugs}), it is important to include this information in
1896 @chapter Running Programs Under @value{GDBN}
1898 When you run a program under @value{GDBN}, you must first generate
1899 debugging information when you compile it.
1901 You may start @value{GDBN} with its arguments, if any, in an environment
1902 of your choice. If you are doing native debugging, you may redirect
1903 your program's input and output, debug an already running process, or
1904 kill a child process.
1907 * Compilation:: Compiling for debugging
1908 * Starting:: Starting your program
1909 * Arguments:: Your program's arguments
1910 * Environment:: Your program's environment
1912 * Working Directory:: Your program's working directory
1913 * Input/Output:: Your program's input and output
1914 * Attach:: Debugging an already-running process
1915 * Kill Process:: Killing the child process
1917 * Inferiors and Programs:: Debugging multiple inferiors and programs
1918 * Threads:: Debugging programs with multiple threads
1919 * Forks:: Debugging forks
1920 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1924 @section Compiling for Debugging
1926 In order to debug a program effectively, you need to generate
1927 debugging information when you compile it. This debugging information
1928 is stored in the object file; it describes the data type of each
1929 variable or function and the correspondence between source line numbers
1930 and addresses in the executable code.
1932 To request debugging information, specify the @samp{-g} option when you run
1935 Programs that are to be shipped to your customers are compiled with
1936 optimizations, using the @samp{-O} compiler option. However, some
1937 compilers are unable to handle the @samp{-g} and @samp{-O} options
1938 together. Using those compilers, you cannot generate optimized
1939 executables containing debugging information.
1941 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1942 without @samp{-O}, making it possible to debug optimized code. We
1943 recommend that you @emph{always} use @samp{-g} whenever you compile a
1944 program. You may think your program is correct, but there is no sense
1945 in pushing your luck. For more information, see @ref{Optimized Code}.
1947 Older versions of the @sc{gnu} C compiler permitted a variant option
1948 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1949 format; if your @sc{gnu} C compiler has this option, do not use it.
1951 @value{GDBN} knows about preprocessor macros and can show you their
1952 expansion (@pxref{Macros}). Most compilers do not include information
1953 about preprocessor macros in the debugging information if you specify
1954 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1955 the @sc{gnu} C compiler, provides macro information if you are using
1956 the DWARF debugging format, and specify the option @option{-g3}.
1958 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1959 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1960 information on @value{NGCC} options affecting debug information.
1962 You will have the best debugging experience if you use the latest
1963 version of the DWARF debugging format that your compiler supports.
1964 DWARF is currently the most expressive and best supported debugging
1965 format in @value{GDBN}.
1969 @section Starting your Program
1975 @kindex r @r{(@code{run})}
1978 Use the @code{run} command to start your program under @value{GDBN}.
1979 You must first specify the program name (except on VxWorks) with an
1980 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1981 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1982 (@pxref{Files, ,Commands to Specify Files}).
1986 If you are running your program in an execution environment that
1987 supports processes, @code{run} creates an inferior process and makes
1988 that process run your program. In some environments without processes,
1989 @code{run} jumps to the start of your program. Other targets,
1990 like @samp{remote}, are always running. If you get an error
1991 message like this one:
1994 The "remote" target does not support "run".
1995 Try "help target" or "continue".
1999 then use @code{continue} to run your program. You may need @code{load}
2000 first (@pxref{load}).
2002 The execution of a program is affected by certain information it
2003 receives from its superior. @value{GDBN} provides ways to specify this
2004 information, which you must do @emph{before} starting your program. (You
2005 can change it after starting your program, but such changes only affect
2006 your program the next time you start it.) This information may be
2007 divided into four categories:
2010 @item The @emph{arguments.}
2011 Specify the arguments to give your program as the arguments of the
2012 @code{run} command. If a shell is available on your target, the shell
2013 is used to pass the arguments, so that you may use normal conventions
2014 (such as wildcard expansion or variable substitution) in describing
2016 In Unix systems, you can control which shell is used with the
2017 @code{SHELL} environment variable. If you do not define @code{SHELL},
2018 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2019 use of any shell with the @code{set startup-with-shell} command (see
2022 @item The @emph{environment.}
2023 Your program normally inherits its environment from @value{GDBN}, but you can
2024 use the @value{GDBN} commands @code{set environment} and @code{unset
2025 environment} to change parts of the environment that affect
2026 your program. @xref{Environment, ,Your Program's Environment}.
2028 @item The @emph{working directory.}
2029 Your program inherits its working directory from @value{GDBN}. You can set
2030 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2031 @xref{Working Directory, ,Your Program's Working Directory}.
2033 @item The @emph{standard input and output.}
2034 Your program normally uses the same device for standard input and
2035 standard output as @value{GDBN} is using. You can redirect input and output
2036 in the @code{run} command line, or you can use the @code{tty} command to
2037 set a different device for your program.
2038 @xref{Input/Output, ,Your Program's Input and Output}.
2041 @emph{Warning:} While input and output redirection work, you cannot use
2042 pipes to pass the output of the program you are debugging to another
2043 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2047 When you issue the @code{run} command, your program begins to execute
2048 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2049 of how to arrange for your program to stop. Once your program has
2050 stopped, you may call functions in your program, using the @code{print}
2051 or @code{call} commands. @xref{Data, ,Examining Data}.
2053 If the modification time of your symbol file has changed since the last
2054 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2055 table, and reads it again. When it does this, @value{GDBN} tries to retain
2056 your current breakpoints.
2061 @cindex run to main procedure
2062 The name of the main procedure can vary from language to language.
2063 With C or C@t{++}, the main procedure name is always @code{main}, but
2064 other languages such as Ada do not require a specific name for their
2065 main procedure. The debugger provides a convenient way to start the
2066 execution of the program and to stop at the beginning of the main
2067 procedure, depending on the language used.
2069 The @samp{start} command does the equivalent of setting a temporary
2070 breakpoint at the beginning of the main procedure and then invoking
2071 the @samp{run} command.
2073 @cindex elaboration phase
2074 Some programs contain an @dfn{elaboration} phase where some startup code is
2075 executed before the main procedure is called. This depends on the
2076 languages used to write your program. In C@t{++}, for instance,
2077 constructors for static and global objects are executed before
2078 @code{main} is called. It is therefore possible that the debugger stops
2079 before reaching the main procedure. However, the temporary breakpoint
2080 will remain to halt execution.
2082 Specify the arguments to give to your program as arguments to the
2083 @samp{start} command. These arguments will be given verbatim to the
2084 underlying @samp{run} command. Note that the same arguments will be
2085 reused if no argument is provided during subsequent calls to
2086 @samp{start} or @samp{run}.
2088 It is sometimes necessary to debug the program during elaboration. In
2089 these cases, using the @code{start} command would stop the execution of
2090 your program too late, as the program would have already completed the
2091 elaboration phase. Under these circumstances, insert breakpoints in your
2092 elaboration code before running your program.
2094 @anchor{set exec-wrapper}
2095 @kindex set exec-wrapper
2096 @item set exec-wrapper @var{wrapper}
2097 @itemx show exec-wrapper
2098 @itemx unset exec-wrapper
2099 When @samp{exec-wrapper} is set, the specified wrapper is used to
2100 launch programs for debugging. @value{GDBN} starts your program
2101 with a shell command of the form @kbd{exec @var{wrapper}
2102 @var{program}}. Quoting is added to @var{program} and its
2103 arguments, but not to @var{wrapper}, so you should add quotes if
2104 appropriate for your shell. The wrapper runs until it executes
2105 your program, and then @value{GDBN} takes control.
2107 You can use any program that eventually calls @code{execve} with
2108 its arguments as a wrapper. Several standard Unix utilities do
2109 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2110 with @code{exec "$@@"} will also work.
2112 For example, you can use @code{env} to pass an environment variable to
2113 the debugged program, without setting the variable in your shell's
2117 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2121 This command is available when debugging locally on most targets, excluding
2122 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2124 @kindex set startup-with-shell
2125 @item set startup-with-shell
2126 @itemx set startup-with-shell on
2127 @itemx set startup-with-shell off
2128 @itemx show set startup-with-shell
2129 On Unix systems, by default, if a shell is available on your target,
2130 @value{GDBN}) uses it to start your program. Arguments of the
2131 @code{run} command are passed to the shell, which does variable
2132 substitution, expands wildcard characters and performs redirection of
2133 I/O. In some circumstances, it may be useful to disable such use of a
2134 shell, for example, when debugging the shell itself or diagnosing
2135 startup failures such as:
2139 Starting program: ./a.out
2140 During startup program terminated with signal SIGSEGV, Segmentation fault.
2144 which indicates the shell or the wrapper specified with
2145 @samp{exec-wrapper} crashed, not your program. Most often, this is
2146 caused by something odd in your shell's non-interactive mode
2147 initialization file---such as @file{.cshrc} for C-shell,
2148 $@file{.zshenv} for the Z shell, or the file specified in the
2149 @samp{BASH_ENV} environment variable for BASH.
2151 @anchor{set auto-connect-native-target}
2152 @kindex set auto-connect-native-target
2153 @item set auto-connect-native-target
2154 @itemx set auto-connect-native-target on
2155 @itemx set auto-connect-native-target off
2156 @itemx show auto-connect-native-target
2158 By default, if not connected to any target yet (e.g., with
2159 @code{target remote}), the @code{run} command starts your program as a
2160 native process under @value{GDBN}, on your local machine. If you're
2161 sure you don't want to debug programs on your local machine, you can
2162 tell @value{GDBN} to not connect to the native target automatically
2163 with the @code{set auto-connect-native-target off} command.
2165 If @code{on}, which is the default, and if @value{GDBN} is not
2166 connected to a target already, the @code{run} command automaticaly
2167 connects to the native target, if one is available.
2169 If @code{off}, and if @value{GDBN} is not connected to a target
2170 already, the @code{run} command fails with an error:
2174 Don't know how to run. Try "help target".
2177 If @value{GDBN} is already connected to a target, @value{GDBN} always
2178 uses it with the @code{run} command.
2180 In any case, you can explicitly connect to the native target with the
2181 @code{target native} command. For example,
2184 (@value{GDBP}) set auto-connect-native-target off
2186 Don't know how to run. Try "help target".
2187 (@value{GDBP}) target native
2189 Starting program: ./a.out
2190 [Inferior 1 (process 10421) exited normally]
2193 In case you connected explicitly to the @code{native} target,
2194 @value{GDBN} remains connected even if all inferiors exit, ready for
2195 the next @code{run} command. Use the @code{disconnect} command to
2198 Examples of other commands that likewise respect the
2199 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2200 proc}, @code{info os}.
2202 @kindex set disable-randomization
2203 @item set disable-randomization
2204 @itemx set disable-randomization on
2205 This option (enabled by default in @value{GDBN}) will turn off the native
2206 randomization of the virtual address space of the started program. This option
2207 is useful for multiple debugging sessions to make the execution better
2208 reproducible and memory addresses reusable across debugging sessions.
2210 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2211 On @sc{gnu}/Linux you can get the same behavior using
2214 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2217 @item set disable-randomization off
2218 Leave the behavior of the started executable unchanged. Some bugs rear their
2219 ugly heads only when the program is loaded at certain addresses. If your bug
2220 disappears when you run the program under @value{GDBN}, that might be because
2221 @value{GDBN} by default disables the address randomization on platforms, such
2222 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2223 disable-randomization off} to try to reproduce such elusive bugs.
2225 On targets where it is available, virtual address space randomization
2226 protects the programs against certain kinds of security attacks. In these
2227 cases the attacker needs to know the exact location of a concrete executable
2228 code. Randomizing its location makes it impossible to inject jumps misusing
2229 a code at its expected addresses.
2231 Prelinking shared libraries provides a startup performance advantage but it
2232 makes addresses in these libraries predictable for privileged processes by
2233 having just unprivileged access at the target system. Reading the shared
2234 library binary gives enough information for assembling the malicious code
2235 misusing it. Still even a prelinked shared library can get loaded at a new
2236 random address just requiring the regular relocation process during the
2237 startup. Shared libraries not already prelinked are always loaded at
2238 a randomly chosen address.
2240 Position independent executables (PIE) contain position independent code
2241 similar to the shared libraries and therefore such executables get loaded at
2242 a randomly chosen address upon startup. PIE executables always load even
2243 already prelinked shared libraries at a random address. You can build such
2244 executable using @command{gcc -fPIE -pie}.
2246 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2247 (as long as the randomization is enabled).
2249 @item show disable-randomization
2250 Show the current setting of the explicit disable of the native randomization of
2251 the virtual address space of the started program.
2256 @section Your Program's Arguments
2258 @cindex arguments (to your program)
2259 The arguments to your program can be specified by the arguments of the
2261 They are passed to a shell, which expands wildcard characters and
2262 performs redirection of I/O, and thence to your program. Your
2263 @code{SHELL} environment variable (if it exists) specifies what shell
2264 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2265 the default shell (@file{/bin/sh} on Unix).
2267 On non-Unix systems, the program is usually invoked directly by
2268 @value{GDBN}, which emulates I/O redirection via the appropriate system
2269 calls, and the wildcard characters are expanded by the startup code of
2270 the program, not by the shell.
2272 @code{run} with no arguments uses the same arguments used by the previous
2273 @code{run}, or those set by the @code{set args} command.
2278 Specify the arguments to be used the next time your program is run. If
2279 @code{set args} has no arguments, @code{run} executes your program
2280 with no arguments. Once you have run your program with arguments,
2281 using @code{set args} before the next @code{run} is the only way to run
2282 it again without arguments.
2286 Show the arguments to give your program when it is started.
2290 @section Your Program's Environment
2292 @cindex environment (of your program)
2293 The @dfn{environment} consists of a set of environment variables and
2294 their values. Environment variables conventionally record such things as
2295 your user name, your home directory, your terminal type, and your search
2296 path for programs to run. Usually you set up environment variables with
2297 the shell and they are inherited by all the other programs you run. When
2298 debugging, it can be useful to try running your program with a modified
2299 environment without having to start @value{GDBN} over again.
2303 @item path @var{directory}
2304 Add @var{directory} to the front of the @code{PATH} environment variable
2305 (the search path for executables) that will be passed to your program.
2306 The value of @code{PATH} used by @value{GDBN} does not change.
2307 You may specify several directory names, separated by whitespace or by a
2308 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2309 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2310 is moved to the front, so it is searched sooner.
2312 You can use the string @samp{$cwd} to refer to whatever is the current
2313 working directory at the time @value{GDBN} searches the path. If you
2314 use @samp{.} instead, it refers to the directory where you executed the
2315 @code{path} command. @value{GDBN} replaces @samp{.} in the
2316 @var{directory} argument (with the current path) before adding
2317 @var{directory} to the search path.
2318 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2319 @c document that, since repeating it would be a no-op.
2323 Display the list of search paths for executables (the @code{PATH}
2324 environment variable).
2326 @kindex show environment
2327 @item show environment @r{[}@var{varname}@r{]}
2328 Print the value of environment variable @var{varname} to be given to
2329 your program when it starts. If you do not supply @var{varname},
2330 print the names and values of all environment variables to be given to
2331 your program. You can abbreviate @code{environment} as @code{env}.
2333 @kindex set environment
2334 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2335 Set environment variable @var{varname} to @var{value}. The value
2336 changes for your program (and the shell @value{GDBN} uses to launch
2337 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2338 values of environment variables are just strings, and any
2339 interpretation is supplied by your program itself. The @var{value}
2340 parameter is optional; if it is eliminated, the variable is set to a
2342 @c "any string" here does not include leading, trailing
2343 @c blanks. Gnu asks: does anyone care?
2345 For example, this command:
2352 tells the debugged program, when subsequently run, that its user is named
2353 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2354 are not actually required.)
2356 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2357 which also inherits the environment set with @code{set environment}.
2358 If necessary, you can avoid that by using the @samp{env} program as a
2359 wrapper instead of using @code{set environment}. @xref{set
2360 exec-wrapper}, for an example doing just that.
2362 @kindex unset environment
2363 @item unset environment @var{varname}
2364 Remove variable @var{varname} from the environment to be passed to your
2365 program. This is different from @samp{set env @var{varname} =};
2366 @code{unset environment} removes the variable from the environment,
2367 rather than assigning it an empty value.
2370 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2371 the shell indicated by your @code{SHELL} environment variable if it
2372 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2373 names a shell that runs an initialization file when started
2374 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2375 for the Z shell, or the file specified in the @samp{BASH_ENV}
2376 environment variable for BASH---any variables you set in that file
2377 affect your program. You may wish to move setting of environment
2378 variables to files that are only run when you sign on, such as
2379 @file{.login} or @file{.profile}.
2381 @node Working Directory
2382 @section Your Program's Working Directory
2384 @cindex working directory (of your program)
2385 Each time you start your program with @code{run}, it inherits its
2386 working directory from the current working directory of @value{GDBN}.
2387 The @value{GDBN} working directory is initially whatever it inherited
2388 from its parent process (typically the shell), but you can specify a new
2389 working directory in @value{GDBN} with the @code{cd} command.
2391 The @value{GDBN} working directory also serves as a default for the commands
2392 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2397 @cindex change working directory
2398 @item cd @r{[}@var{directory}@r{]}
2399 Set the @value{GDBN} working directory to @var{directory}. If not
2400 given, @var{directory} uses @file{'~'}.
2404 Print the @value{GDBN} working directory.
2407 It is generally impossible to find the current working directory of
2408 the process being debugged (since a program can change its directory
2409 during its run). If you work on a system where @value{GDBN} is
2410 configured with the @file{/proc} support, you can use the @code{info
2411 proc} command (@pxref{SVR4 Process Information}) to find out the
2412 current working directory of the debuggee.
2415 @section Your Program's Input and Output
2420 By default, the program you run under @value{GDBN} does input and output to
2421 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2422 to its own terminal modes to interact with you, but it records the terminal
2423 modes your program was using and switches back to them when you continue
2424 running your program.
2427 @kindex info terminal
2429 Displays information recorded by @value{GDBN} about the terminal modes your
2433 You can redirect your program's input and/or output using shell
2434 redirection with the @code{run} command. For example,
2441 starts your program, diverting its output to the file @file{outfile}.
2444 @cindex controlling terminal
2445 Another way to specify where your program should do input and output is
2446 with the @code{tty} command. This command accepts a file name as
2447 argument, and causes this file to be the default for future @code{run}
2448 commands. It also resets the controlling terminal for the child
2449 process, for future @code{run} commands. For example,
2456 directs that processes started with subsequent @code{run} commands
2457 default to do input and output on the terminal @file{/dev/ttyb} and have
2458 that as their controlling terminal.
2460 An explicit redirection in @code{run} overrides the @code{tty} command's
2461 effect on the input/output device, but not its effect on the controlling
2464 When you use the @code{tty} command or redirect input in the @code{run}
2465 command, only the input @emph{for your program} is affected. The input
2466 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2467 for @code{set inferior-tty}.
2469 @cindex inferior tty
2470 @cindex set inferior controlling terminal
2471 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2472 display the name of the terminal that will be used for future runs of your
2476 @item set inferior-tty /dev/ttyb
2477 @kindex set inferior-tty
2478 Set the tty for the program being debugged to /dev/ttyb.
2480 @item show inferior-tty
2481 @kindex show inferior-tty
2482 Show the current tty for the program being debugged.
2486 @section Debugging an Already-running Process
2491 @item attach @var{process-id}
2492 This command attaches to a running process---one that was started
2493 outside @value{GDBN}. (@code{info files} shows your active
2494 targets.) The command takes as argument a process ID. The usual way to
2495 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2496 or with the @samp{jobs -l} shell command.
2498 @code{attach} does not repeat if you press @key{RET} a second time after
2499 executing the command.
2502 To use @code{attach}, your program must be running in an environment
2503 which supports processes; for example, @code{attach} does not work for
2504 programs on bare-board targets that lack an operating system. You must
2505 also have permission to send the process a signal.
2507 When you use @code{attach}, the debugger finds the program running in
2508 the process first by looking in the current working directory, then (if
2509 the program is not found) by using the source file search path
2510 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2511 the @code{file} command to load the program. @xref{Files, ,Commands to
2514 The first thing @value{GDBN} does after arranging to debug the specified
2515 process is to stop it. You can examine and modify an attached process
2516 with all the @value{GDBN} commands that are ordinarily available when
2517 you start processes with @code{run}. You can insert breakpoints; you
2518 can step and continue; you can modify storage. If you would rather the
2519 process continue running, you may use the @code{continue} command after
2520 attaching @value{GDBN} to the process.
2525 When you have finished debugging the attached process, you can use the
2526 @code{detach} command to release it from @value{GDBN} control. Detaching
2527 the process continues its execution. After the @code{detach} command,
2528 that process and @value{GDBN} become completely independent once more, and you
2529 are ready to @code{attach} another process or start one with @code{run}.
2530 @code{detach} does not repeat if you press @key{RET} again after
2531 executing the command.
2534 If you exit @value{GDBN} while you have an attached process, you detach
2535 that process. If you use the @code{run} command, you kill that process.
2536 By default, @value{GDBN} asks for confirmation if you try to do either of these
2537 things; you can control whether or not you need to confirm by using the
2538 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2542 @section Killing the Child Process
2547 Kill the child process in which your program is running under @value{GDBN}.
2550 This command is useful if you wish to debug a core dump instead of a
2551 running process. @value{GDBN} ignores any core dump file while your program
2554 On some operating systems, a program cannot be executed outside @value{GDBN}
2555 while you have breakpoints set on it inside @value{GDBN}. You can use the
2556 @code{kill} command in this situation to permit running your program
2557 outside the debugger.
2559 The @code{kill} command is also useful if you wish to recompile and
2560 relink your program, since on many systems it is impossible to modify an
2561 executable file while it is running in a process. In this case, when you
2562 next type @code{run}, @value{GDBN} notices that the file has changed, and
2563 reads the symbol table again (while trying to preserve your current
2564 breakpoint settings).
2566 @node Inferiors and Programs
2567 @section Debugging Multiple Inferiors and Programs
2569 @value{GDBN} lets you run and debug multiple programs in a single
2570 session. In addition, @value{GDBN} on some systems may let you run
2571 several programs simultaneously (otherwise you have to exit from one
2572 before starting another). In the most general case, you can have
2573 multiple threads of execution in each of multiple processes, launched
2574 from multiple executables.
2577 @value{GDBN} represents the state of each program execution with an
2578 object called an @dfn{inferior}. An inferior typically corresponds to
2579 a process, but is more general and applies also to targets that do not
2580 have processes. Inferiors may be created before a process runs, and
2581 may be retained after a process exits. Inferiors have unique
2582 identifiers that are different from process ids. Usually each
2583 inferior will also have its own distinct address space, although some
2584 embedded targets may have several inferiors running in different parts
2585 of a single address space. Each inferior may in turn have multiple
2586 threads running in it.
2588 To find out what inferiors exist at any moment, use @w{@code{info
2592 @kindex info inferiors
2593 @item info inferiors
2594 Print a list of all inferiors currently being managed by @value{GDBN}.
2596 @value{GDBN} displays for each inferior (in this order):
2600 the inferior number assigned by @value{GDBN}
2603 the target system's inferior identifier
2606 the name of the executable the inferior is running.
2611 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2612 indicates the current inferior.
2616 @c end table here to get a little more width for example
2619 (@value{GDBP}) info inferiors
2620 Num Description Executable
2621 2 process 2307 hello
2622 * 1 process 3401 goodbye
2625 To switch focus between inferiors, use the @code{inferior} command:
2628 @kindex inferior @var{infno}
2629 @item inferior @var{infno}
2630 Make inferior number @var{infno} the current inferior. The argument
2631 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2632 in the first field of the @samp{info inferiors} display.
2636 You can get multiple executables into a debugging session via the
2637 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2638 systems @value{GDBN} can add inferiors to the debug session
2639 automatically by following calls to @code{fork} and @code{exec}. To
2640 remove inferiors from the debugging session use the
2641 @w{@code{remove-inferiors}} command.
2644 @kindex add-inferior
2645 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2646 Adds @var{n} inferiors to be run using @var{executable} as the
2647 executable; @var{n} defaults to 1. If no executable is specified,
2648 the inferiors begins empty, with no program. You can still assign or
2649 change the program assigned to the inferior at any time by using the
2650 @code{file} command with the executable name as its argument.
2652 @kindex clone-inferior
2653 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2654 Adds @var{n} inferiors ready to execute the same program as inferior
2655 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2656 number of the current inferior. This is a convenient command when you
2657 want to run another instance of the inferior you are debugging.
2660 (@value{GDBP}) info inferiors
2661 Num Description Executable
2662 * 1 process 29964 helloworld
2663 (@value{GDBP}) clone-inferior
2666 (@value{GDBP}) info inferiors
2667 Num Description Executable
2669 * 1 process 29964 helloworld
2672 You can now simply switch focus to inferior 2 and run it.
2674 @kindex remove-inferiors
2675 @item remove-inferiors @var{infno}@dots{}
2676 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2677 possible to remove an inferior that is running with this command. For
2678 those, use the @code{kill} or @code{detach} command first.
2682 To quit debugging one of the running inferiors that is not the current
2683 inferior, you can either detach from it by using the @w{@code{detach
2684 inferior}} command (allowing it to run independently), or kill it
2685 using the @w{@code{kill inferiors}} command:
2688 @kindex detach inferiors @var{infno}@dots{}
2689 @item detach inferior @var{infno}@dots{}
2690 Detach from the inferior or inferiors identified by @value{GDBN}
2691 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2692 still stays on the list of inferiors shown by @code{info inferiors},
2693 but its Description will show @samp{<null>}.
2695 @kindex kill inferiors @var{infno}@dots{}
2696 @item kill inferiors @var{infno}@dots{}
2697 Kill the inferior or inferiors identified by @value{GDBN} inferior
2698 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2699 stays on the list of inferiors shown by @code{info inferiors}, but its
2700 Description will show @samp{<null>}.
2703 After the successful completion of a command such as @code{detach},
2704 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2705 a normal process exit, the inferior is still valid and listed with
2706 @code{info inferiors}, ready to be restarted.
2709 To be notified when inferiors are started or exit under @value{GDBN}'s
2710 control use @w{@code{set print inferior-events}}:
2713 @kindex set print inferior-events
2714 @cindex print messages on inferior start and exit
2715 @item set print inferior-events
2716 @itemx set print inferior-events on
2717 @itemx set print inferior-events off
2718 The @code{set print inferior-events} command allows you to enable or
2719 disable printing of messages when @value{GDBN} notices that new
2720 inferiors have started or that inferiors have exited or have been
2721 detached. By default, these messages will not be printed.
2723 @kindex show print inferior-events
2724 @item show print inferior-events
2725 Show whether messages will be printed when @value{GDBN} detects that
2726 inferiors have started, exited or have been detached.
2729 Many commands will work the same with multiple programs as with a
2730 single program: e.g., @code{print myglobal} will simply display the
2731 value of @code{myglobal} in the current inferior.
2734 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2735 get more info about the relationship of inferiors, programs, address
2736 spaces in a debug session. You can do that with the @w{@code{maint
2737 info program-spaces}} command.
2740 @kindex maint info program-spaces
2741 @item maint info program-spaces
2742 Print a list of all program spaces currently being managed by
2745 @value{GDBN} displays for each program space (in this order):
2749 the program space number assigned by @value{GDBN}
2752 the name of the executable loaded into the program space, with e.g.,
2753 the @code{file} command.
2758 An asterisk @samp{*} preceding the @value{GDBN} program space number
2759 indicates the current program space.
2761 In addition, below each program space line, @value{GDBN} prints extra
2762 information that isn't suitable to display in tabular form. For
2763 example, the list of inferiors bound to the program space.
2766 (@value{GDBP}) maint info program-spaces
2769 Bound inferiors: ID 1 (process 21561)
2773 Here we can see that no inferior is running the program @code{hello},
2774 while @code{process 21561} is running the program @code{goodbye}. On
2775 some targets, it is possible that multiple inferiors are bound to the
2776 same program space. The most common example is that of debugging both
2777 the parent and child processes of a @code{vfork} call. For example,
2780 (@value{GDBP}) maint info program-spaces
2783 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2786 Here, both inferior 2 and inferior 1 are running in the same program
2787 space as a result of inferior 1 having executed a @code{vfork} call.
2791 @section Debugging Programs with Multiple Threads
2793 @cindex threads of execution
2794 @cindex multiple threads
2795 @cindex switching threads
2796 In some operating systems, such as HP-UX and Solaris, a single program
2797 may have more than one @dfn{thread} of execution. The precise semantics
2798 of threads differ from one operating system to another, but in general
2799 the threads of a single program are akin to multiple processes---except
2800 that they share one address space (that is, they can all examine and
2801 modify the same variables). On the other hand, each thread has its own
2802 registers and execution stack, and perhaps private memory.
2804 @value{GDBN} provides these facilities for debugging multi-thread
2808 @item automatic notification of new threads
2809 @item @samp{thread @var{threadno}}, a command to switch among threads
2810 @item @samp{info threads}, a command to inquire about existing threads
2811 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2812 a command to apply a command to a list of threads
2813 @item thread-specific breakpoints
2814 @item @samp{set print thread-events}, which controls printing of
2815 messages on thread start and exit.
2816 @item @samp{set libthread-db-search-path @var{path}}, which lets
2817 the user specify which @code{libthread_db} to use if the default choice
2818 isn't compatible with the program.
2822 @emph{Warning:} These facilities are not yet available on every
2823 @value{GDBN} configuration where the operating system supports threads.
2824 If your @value{GDBN} does not support threads, these commands have no
2825 effect. For example, a system without thread support shows no output
2826 from @samp{info threads}, and always rejects the @code{thread} command,
2830 (@value{GDBP}) info threads
2831 (@value{GDBP}) thread 1
2832 Thread ID 1 not known. Use the "info threads" command to
2833 see the IDs of currently known threads.
2835 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2836 @c doesn't support threads"?
2839 @cindex focus of debugging
2840 @cindex current thread
2841 The @value{GDBN} thread debugging facility allows you to observe all
2842 threads while your program runs---but whenever @value{GDBN} takes
2843 control, one thread in particular is always the focus of debugging.
2844 This thread is called the @dfn{current thread}. Debugging commands show
2845 program information from the perspective of the current thread.
2847 @cindex @code{New} @var{systag} message
2848 @cindex thread identifier (system)
2849 @c FIXME-implementors!! It would be more helpful if the [New...] message
2850 @c included GDB's numeric thread handle, so you could just go to that
2851 @c thread without first checking `info threads'.
2852 Whenever @value{GDBN} detects a new thread in your program, it displays
2853 the target system's identification for the thread with a message in the
2854 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2855 whose form varies depending on the particular system. For example, on
2856 @sc{gnu}/Linux, you might see
2859 [New Thread 0x41e02940 (LWP 25582)]
2863 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2864 the @var{systag} is simply something like @samp{process 368}, with no
2867 @c FIXME!! (1) Does the [New...] message appear even for the very first
2868 @c thread of a program, or does it only appear for the
2869 @c second---i.e.@: when it becomes obvious we have a multithread
2871 @c (2) *Is* there necessarily a first thread always? Or do some
2872 @c multithread systems permit starting a program with multiple
2873 @c threads ab initio?
2875 @cindex thread number
2876 @cindex thread identifier (GDB)
2877 For debugging purposes, @value{GDBN} associates its own thread
2878 number---always a single integer---with each thread in your program.
2881 @kindex info threads
2882 @item info threads @r{[}@var{id}@dots{}@r{]}
2883 Display a summary of all threads currently in your program. Optional
2884 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2885 means to print information only about the specified thread or threads.
2886 @value{GDBN} displays for each thread (in this order):
2890 the thread number assigned by @value{GDBN}
2893 the target system's thread identifier (@var{systag})
2896 the thread's name, if one is known. A thread can either be named by
2897 the user (see @code{thread name}, below), or, in some cases, by the
2901 the current stack frame summary for that thread
2905 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2906 indicates the current thread.
2910 @c end table here to get a little more width for example
2913 (@value{GDBP}) info threads
2915 3 process 35 thread 27 0x34e5 in sigpause ()
2916 2 process 35 thread 23 0x34e5 in sigpause ()
2917 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2921 On Solaris, you can display more information about user threads with a
2922 Solaris-specific command:
2925 @item maint info sol-threads
2926 @kindex maint info sol-threads
2927 @cindex thread info (Solaris)
2928 Display info on Solaris user threads.
2932 @kindex thread @var{threadno}
2933 @item thread @var{threadno}
2934 Make thread number @var{threadno} the current thread. The command
2935 argument @var{threadno} is the internal @value{GDBN} thread number, as
2936 shown in the first field of the @samp{info threads} display.
2937 @value{GDBN} responds by displaying the system identifier of the thread
2938 you selected, and its current stack frame summary:
2941 (@value{GDBP}) thread 2
2942 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2943 #0 some_function (ignore=0x0) at example.c:8
2944 8 printf ("hello\n");
2948 As with the @samp{[New @dots{}]} message, the form of the text after
2949 @samp{Switching to} depends on your system's conventions for identifying
2952 @vindex $_thread@r{, convenience variable}
2953 The debugger convenience variable @samp{$_thread} contains the number
2954 of the current thread. You may find this useful in writing breakpoint
2955 conditional expressions, command scripts, and so forth. See
2956 @xref{Convenience Vars,, Convenience Variables}, for general
2957 information on convenience variables.
2959 @kindex thread apply
2960 @cindex apply command to several threads
2961 @item thread apply [@var{threadno} | all] @var{command}
2962 The @code{thread apply} command allows you to apply the named
2963 @var{command} to one or more threads. Specify the numbers of the
2964 threads that you want affected with the command argument
2965 @var{threadno}. It can be a single thread number, one of the numbers
2966 shown in the first field of the @samp{info threads} display; or it
2967 could be a range of thread numbers, as in @code{2-4}. To apply a
2968 command to all threads, type @kbd{thread apply all @var{command}}.
2971 @cindex name a thread
2972 @item thread name [@var{name}]
2973 This command assigns a name to the current thread. If no argument is
2974 given, any existing user-specified name is removed. The thread name
2975 appears in the @samp{info threads} display.
2977 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2978 determine the name of the thread as given by the OS. On these
2979 systems, a name specified with @samp{thread name} will override the
2980 system-give name, and removing the user-specified name will cause
2981 @value{GDBN} to once again display the system-specified name.
2984 @cindex search for a thread
2985 @item thread find [@var{regexp}]
2986 Search for and display thread ids whose name or @var{systag}
2987 matches the supplied regular expression.
2989 As well as being the complement to the @samp{thread name} command,
2990 this command also allows you to identify a thread by its target
2991 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2995 (@value{GDBN}) thread find 26688
2996 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2997 (@value{GDBN}) info thread 4
2999 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3002 @kindex set print thread-events
3003 @cindex print messages on thread start and exit
3004 @item set print thread-events
3005 @itemx set print thread-events on
3006 @itemx set print thread-events off
3007 The @code{set print thread-events} command allows you to enable or
3008 disable printing of messages when @value{GDBN} notices that new threads have
3009 started or that threads have exited. By default, these messages will
3010 be printed if detection of these events is supported by the target.
3011 Note that these messages cannot be disabled on all targets.
3013 @kindex show print thread-events
3014 @item show print thread-events
3015 Show whether messages will be printed when @value{GDBN} detects that threads
3016 have started and exited.
3019 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3020 more information about how @value{GDBN} behaves when you stop and start
3021 programs with multiple threads.
3023 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3024 watchpoints in programs with multiple threads.
3026 @anchor{set libthread-db-search-path}
3028 @kindex set libthread-db-search-path
3029 @cindex search path for @code{libthread_db}
3030 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3031 If this variable is set, @var{path} is a colon-separated list of
3032 directories @value{GDBN} will use to search for @code{libthread_db}.
3033 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3034 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3035 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3038 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3039 @code{libthread_db} library to obtain information about threads in the
3040 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3041 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3042 specific thread debugging library loading is enabled
3043 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3045 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3046 refers to the default system directories that are
3047 normally searched for loading shared libraries. The @samp{$sdir} entry
3048 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3049 (@pxref{libthread_db.so.1 file}).
3051 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3052 refers to the directory from which @code{libpthread}
3053 was loaded in the inferior process.
3055 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3056 @value{GDBN} attempts to initialize it with the current inferior process.
3057 If this initialization fails (which could happen because of a version
3058 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3059 will unload @code{libthread_db}, and continue with the next directory.
3060 If none of @code{libthread_db} libraries initialize successfully,
3061 @value{GDBN} will issue a warning and thread debugging will be disabled.
3063 Setting @code{libthread-db-search-path} is currently implemented
3064 only on some platforms.
3066 @kindex show libthread-db-search-path
3067 @item show libthread-db-search-path
3068 Display current libthread_db search path.
3070 @kindex set debug libthread-db
3071 @kindex show debug libthread-db
3072 @cindex debugging @code{libthread_db}
3073 @item set debug libthread-db
3074 @itemx show debug libthread-db
3075 Turns on or off display of @code{libthread_db}-related events.
3076 Use @code{1} to enable, @code{0} to disable.
3080 @section Debugging Forks
3082 @cindex fork, debugging programs which call
3083 @cindex multiple processes
3084 @cindex processes, multiple
3085 On most systems, @value{GDBN} has no special support for debugging
3086 programs which create additional processes using the @code{fork}
3087 function. When a program forks, @value{GDBN} will continue to debug the
3088 parent process and the child process will run unimpeded. If you have
3089 set a breakpoint in any code which the child then executes, the child
3090 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3091 will cause it to terminate.
3093 However, if you want to debug the child process there is a workaround
3094 which isn't too painful. Put a call to @code{sleep} in the code which
3095 the child process executes after the fork. It may be useful to sleep
3096 only if a certain environment variable is set, or a certain file exists,
3097 so that the delay need not occur when you don't want to run @value{GDBN}
3098 on the child. While the child is sleeping, use the @code{ps} program to
3099 get its process ID. Then tell @value{GDBN} (a new invocation of
3100 @value{GDBN} if you are also debugging the parent process) to attach to
3101 the child process (@pxref{Attach}). From that point on you can debug
3102 the child process just like any other process which you attached to.
3104 On some systems, @value{GDBN} provides support for debugging programs that
3105 create additional processes using the @code{fork} or @code{vfork} functions.
3106 Currently, the only platforms with this feature are HP-UX (11.x and later
3107 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3109 By default, when a program forks, @value{GDBN} will continue to debug
3110 the parent process and the child process will run unimpeded.
3112 If you want to follow the child process instead of the parent process,
3113 use the command @w{@code{set follow-fork-mode}}.
3116 @kindex set follow-fork-mode
3117 @item set follow-fork-mode @var{mode}
3118 Set the debugger response to a program call of @code{fork} or
3119 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3120 process. The @var{mode} argument can be:
3124 The original process is debugged after a fork. The child process runs
3125 unimpeded. This is the default.
3128 The new process is debugged after a fork. The parent process runs
3133 @kindex show follow-fork-mode
3134 @item show follow-fork-mode
3135 Display the current debugger response to a @code{fork} or @code{vfork} call.
3138 @cindex debugging multiple processes
3139 On Linux, if you want to debug both the parent and child processes, use the
3140 command @w{@code{set detach-on-fork}}.
3143 @kindex set detach-on-fork
3144 @item set detach-on-fork @var{mode}
3145 Tells gdb whether to detach one of the processes after a fork, or
3146 retain debugger control over them both.
3150 The child process (or parent process, depending on the value of
3151 @code{follow-fork-mode}) will be detached and allowed to run
3152 independently. This is the default.
3155 Both processes will be held under the control of @value{GDBN}.
3156 One process (child or parent, depending on the value of
3157 @code{follow-fork-mode}) is debugged as usual, while the other
3162 @kindex show detach-on-fork
3163 @item show detach-on-fork
3164 Show whether detach-on-fork mode is on/off.
3167 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3168 will retain control of all forked processes (including nested forks).
3169 You can list the forked processes under the control of @value{GDBN} by
3170 using the @w{@code{info inferiors}} command, and switch from one fork
3171 to another by using the @code{inferior} command (@pxref{Inferiors and
3172 Programs, ,Debugging Multiple Inferiors and Programs}).
3174 To quit debugging one of the forked processes, you can either detach
3175 from it by using the @w{@code{detach inferiors}} command (allowing it
3176 to run independently), or kill it using the @w{@code{kill inferiors}}
3177 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3180 If you ask to debug a child process and a @code{vfork} is followed by an
3181 @code{exec}, @value{GDBN} executes the new target up to the first
3182 breakpoint in the new target. If you have a breakpoint set on
3183 @code{main} in your original program, the breakpoint will also be set on
3184 the child process's @code{main}.
3186 On some systems, when a child process is spawned by @code{vfork}, you
3187 cannot debug the child or parent until an @code{exec} call completes.
3189 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3190 call executes, the new target restarts. To restart the parent
3191 process, use the @code{file} command with the parent executable name
3192 as its argument. By default, after an @code{exec} call executes,
3193 @value{GDBN} discards the symbols of the previous executable image.
3194 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3198 @kindex set follow-exec-mode
3199 @item set follow-exec-mode @var{mode}
3201 Set debugger response to a program call of @code{exec}. An
3202 @code{exec} call replaces the program image of a process.
3204 @code{follow-exec-mode} can be:
3208 @value{GDBN} creates a new inferior and rebinds the process to this
3209 new inferior. The program the process was running before the
3210 @code{exec} call can be restarted afterwards by restarting the
3216 (@value{GDBP}) info inferiors
3218 Id Description Executable
3221 process 12020 is executing new program: prog2
3222 Program exited normally.
3223 (@value{GDBP}) info inferiors
3224 Id Description Executable
3230 @value{GDBN} keeps the process bound to the same inferior. The new
3231 executable image replaces the previous executable loaded in the
3232 inferior. Restarting the inferior after the @code{exec} call, with
3233 e.g., the @code{run} command, restarts the executable the process was
3234 running after the @code{exec} call. This is the default mode.
3239 (@value{GDBP}) info inferiors
3240 Id Description Executable
3243 process 12020 is executing new program: prog2
3244 Program exited normally.
3245 (@value{GDBP}) info inferiors
3246 Id Description Executable
3253 You can use the @code{catch} command to make @value{GDBN} stop whenever
3254 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3255 Catchpoints, ,Setting Catchpoints}.
3257 @node Checkpoint/Restart
3258 @section Setting a @emph{Bookmark} to Return to Later
3263 @cindex snapshot of a process
3264 @cindex rewind program state
3266 On certain operating systems@footnote{Currently, only
3267 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3268 program's state, called a @dfn{checkpoint}, and come back to it
3271 Returning to a checkpoint effectively undoes everything that has
3272 happened in the program since the @code{checkpoint} was saved. This
3273 includes changes in memory, registers, and even (within some limits)
3274 system state. Effectively, it is like going back in time to the
3275 moment when the checkpoint was saved.
3277 Thus, if you're stepping thru a program and you think you're
3278 getting close to the point where things go wrong, you can save
3279 a checkpoint. Then, if you accidentally go too far and miss
3280 the critical statement, instead of having to restart your program
3281 from the beginning, you can just go back to the checkpoint and
3282 start again from there.
3284 This can be especially useful if it takes a lot of time or
3285 steps to reach the point where you think the bug occurs.
3287 To use the @code{checkpoint}/@code{restart} method of debugging:
3292 Save a snapshot of the debugged program's current execution state.
3293 The @code{checkpoint} command takes no arguments, but each checkpoint
3294 is assigned a small integer id, similar to a breakpoint id.
3296 @kindex info checkpoints
3297 @item info checkpoints
3298 List the checkpoints that have been saved in the current debugging
3299 session. For each checkpoint, the following information will be
3306 @item Source line, or label
3309 @kindex restart @var{checkpoint-id}
3310 @item restart @var{checkpoint-id}
3311 Restore the program state that was saved as checkpoint number
3312 @var{checkpoint-id}. All program variables, registers, stack frames
3313 etc.@: will be returned to the values that they had when the checkpoint
3314 was saved. In essence, gdb will ``wind back the clock'' to the point
3315 in time when the checkpoint was saved.
3317 Note that breakpoints, @value{GDBN} variables, command history etc.
3318 are not affected by restoring a checkpoint. In general, a checkpoint
3319 only restores things that reside in the program being debugged, not in
3322 @kindex delete checkpoint @var{checkpoint-id}
3323 @item delete checkpoint @var{checkpoint-id}
3324 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3328 Returning to a previously saved checkpoint will restore the user state
3329 of the program being debugged, plus a significant subset of the system
3330 (OS) state, including file pointers. It won't ``un-write'' data from
3331 a file, but it will rewind the file pointer to the previous location,
3332 so that the previously written data can be overwritten. For files
3333 opened in read mode, the pointer will also be restored so that the
3334 previously read data can be read again.
3336 Of course, characters that have been sent to a printer (or other
3337 external device) cannot be ``snatched back'', and characters received
3338 from eg.@: a serial device can be removed from internal program buffers,
3339 but they cannot be ``pushed back'' into the serial pipeline, ready to
3340 be received again. Similarly, the actual contents of files that have
3341 been changed cannot be restored (at this time).
3343 However, within those constraints, you actually can ``rewind'' your
3344 program to a previously saved point in time, and begin debugging it
3345 again --- and you can change the course of events so as to debug a
3346 different execution path this time.
3348 @cindex checkpoints and process id
3349 Finally, there is one bit of internal program state that will be
3350 different when you return to a checkpoint --- the program's process
3351 id. Each checkpoint will have a unique process id (or @var{pid}),
3352 and each will be different from the program's original @var{pid}.
3353 If your program has saved a local copy of its process id, this could
3354 potentially pose a problem.
3356 @subsection A Non-obvious Benefit of Using Checkpoints
3358 On some systems such as @sc{gnu}/Linux, address space randomization
3359 is performed on new processes for security reasons. This makes it
3360 difficult or impossible to set a breakpoint, or watchpoint, on an
3361 absolute address if you have to restart the program, since the
3362 absolute location of a symbol will change from one execution to the
3365 A checkpoint, however, is an @emph{identical} copy of a process.
3366 Therefore if you create a checkpoint at (eg.@:) the start of main,
3367 and simply return to that checkpoint instead of restarting the
3368 process, you can avoid the effects of address randomization and
3369 your symbols will all stay in the same place.
3372 @chapter Stopping and Continuing
3374 The principal purposes of using a debugger are so that you can stop your
3375 program before it terminates; or so that, if your program runs into
3376 trouble, you can investigate and find out why.
3378 Inside @value{GDBN}, your program may stop for any of several reasons,
3379 such as a signal, a breakpoint, or reaching a new line after a
3380 @value{GDBN} command such as @code{step}. You may then examine and
3381 change variables, set new breakpoints or remove old ones, and then
3382 continue execution. Usually, the messages shown by @value{GDBN} provide
3383 ample explanation of the status of your program---but you can also
3384 explicitly request this information at any time.
3387 @kindex info program
3389 Display information about the status of your program: whether it is
3390 running or not, what process it is, and why it stopped.
3394 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3395 * Continuing and Stepping:: Resuming execution
3396 * Skipping Over Functions and Files::
3397 Skipping over functions and files
3399 * Thread Stops:: Stopping and starting multi-thread programs
3403 @section Breakpoints, Watchpoints, and Catchpoints
3406 A @dfn{breakpoint} makes your program stop whenever a certain point in
3407 the program is reached. For each breakpoint, you can add conditions to
3408 control in finer detail whether your program stops. You can set
3409 breakpoints with the @code{break} command and its variants (@pxref{Set
3410 Breaks, ,Setting Breakpoints}), to specify the place where your program
3411 should stop by line number, function name or exact address in the
3414 On some systems, you can set breakpoints in shared libraries before
3415 the executable is run. There is a minor limitation on HP-UX systems:
3416 you must wait until the executable is run in order to set breakpoints
3417 in shared library routines that are not called directly by the program
3418 (for example, routines that are arguments in a @code{pthread_create}
3422 @cindex data breakpoints
3423 @cindex memory tracing
3424 @cindex breakpoint on memory address
3425 @cindex breakpoint on variable modification
3426 A @dfn{watchpoint} is a special breakpoint that stops your program
3427 when the value of an expression changes. The expression may be a value
3428 of a variable, or it could involve values of one or more variables
3429 combined by operators, such as @samp{a + b}. This is sometimes called
3430 @dfn{data breakpoints}. You must use a different command to set
3431 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3432 from that, you can manage a watchpoint like any other breakpoint: you
3433 enable, disable, and delete both breakpoints and watchpoints using the
3436 You can arrange to have values from your program displayed automatically
3437 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3441 @cindex breakpoint on events
3442 A @dfn{catchpoint} is another special breakpoint that stops your program
3443 when a certain kind of event occurs, such as the throwing of a C@t{++}
3444 exception or the loading of a library. As with watchpoints, you use a
3445 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3446 Catchpoints}), but aside from that, you can manage a catchpoint like any
3447 other breakpoint. (To stop when your program receives a signal, use the
3448 @code{handle} command; see @ref{Signals, ,Signals}.)
3450 @cindex breakpoint numbers
3451 @cindex numbers for breakpoints
3452 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3453 catchpoint when you create it; these numbers are successive integers
3454 starting with one. In many of the commands for controlling various
3455 features of breakpoints you use the breakpoint number to say which
3456 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3457 @dfn{disabled}; if disabled, it has no effect on your program until you
3460 @cindex breakpoint ranges
3461 @cindex ranges of breakpoints
3462 Some @value{GDBN} commands accept a range of breakpoints on which to
3463 operate. A breakpoint range is either a single breakpoint number, like
3464 @samp{5}, or two such numbers, in increasing order, separated by a
3465 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3466 all breakpoints in that range are operated on.
3469 * Set Breaks:: Setting breakpoints
3470 * Set Watchpoints:: Setting watchpoints
3471 * Set Catchpoints:: Setting catchpoints
3472 * Delete Breaks:: Deleting breakpoints
3473 * Disabling:: Disabling breakpoints
3474 * Conditions:: Break conditions
3475 * Break Commands:: Breakpoint command lists
3476 * Dynamic Printf:: Dynamic printf
3477 * Save Breakpoints:: How to save breakpoints in a file
3478 * Static Probe Points:: Listing static probe points
3479 * Error in Breakpoints:: ``Cannot insert breakpoints''
3480 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3484 @subsection Setting Breakpoints
3486 @c FIXME LMB what does GDB do if no code on line of breakpt?
3487 @c consider in particular declaration with/without initialization.
3489 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3492 @kindex b @r{(@code{break})}
3493 @vindex $bpnum@r{, convenience variable}
3494 @cindex latest breakpoint
3495 Breakpoints are set with the @code{break} command (abbreviated
3496 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3497 number of the breakpoint you've set most recently; see @ref{Convenience
3498 Vars,, Convenience Variables}, for a discussion of what you can do with
3499 convenience variables.
3502 @item break @var{location}
3503 Set a breakpoint at the given @var{location}, which can specify a
3504 function name, a line number, or an address of an instruction.
3505 (@xref{Specify Location}, for a list of all the possible ways to
3506 specify a @var{location}.) The breakpoint will stop your program just
3507 before it executes any of the code in the specified @var{location}.
3509 When using source languages that permit overloading of symbols, such as
3510 C@t{++}, a function name may refer to more than one possible place to break.
3511 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3514 It is also possible to insert a breakpoint that will stop the program
3515 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3516 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3519 When called without any arguments, @code{break} sets a breakpoint at
3520 the next instruction to be executed in the selected stack frame
3521 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3522 innermost, this makes your program stop as soon as control
3523 returns to that frame. This is similar to the effect of a
3524 @code{finish} command in the frame inside the selected frame---except
3525 that @code{finish} does not leave an active breakpoint. If you use
3526 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3527 the next time it reaches the current location; this may be useful
3530 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3531 least one instruction has been executed. If it did not do this, you
3532 would be unable to proceed past a breakpoint without first disabling the
3533 breakpoint. This rule applies whether or not the breakpoint already
3534 existed when your program stopped.
3536 @item break @dots{} if @var{cond}
3537 Set a breakpoint with condition @var{cond}; evaluate the expression
3538 @var{cond} each time the breakpoint is reached, and stop only if the
3539 value is nonzero---that is, if @var{cond} evaluates as true.
3540 @samp{@dots{}} stands for one of the possible arguments described
3541 above (or no argument) specifying where to break. @xref{Conditions,
3542 ,Break Conditions}, for more information on breakpoint conditions.
3545 @item tbreak @var{args}
3546 Set a breakpoint enabled only for one stop. The @var{args} are the
3547 same as for the @code{break} command, and the breakpoint is set in the same
3548 way, but the breakpoint is automatically deleted after the first time your
3549 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3552 @cindex hardware breakpoints
3553 @item hbreak @var{args}
3554 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3555 @code{break} command and the breakpoint is set in the same way, but the
3556 breakpoint requires hardware support and some target hardware may not
3557 have this support. The main purpose of this is EPROM/ROM code
3558 debugging, so you can set a breakpoint at an instruction without
3559 changing the instruction. This can be used with the new trap-generation
3560 provided by SPARClite DSU and most x86-based targets. These targets
3561 will generate traps when a program accesses some data or instruction
3562 address that is assigned to the debug registers. However the hardware
3563 breakpoint registers can take a limited number of breakpoints. For
3564 example, on the DSU, only two data breakpoints can be set at a time, and
3565 @value{GDBN} will reject this command if more than two are used. Delete
3566 or disable unused hardware breakpoints before setting new ones
3567 (@pxref{Disabling, ,Disabling Breakpoints}).
3568 @xref{Conditions, ,Break Conditions}.
3569 For remote targets, you can restrict the number of hardware
3570 breakpoints @value{GDBN} will use, see @ref{set remote
3571 hardware-breakpoint-limit}.
3574 @item thbreak @var{args}
3575 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3576 are the same as for the @code{hbreak} command and the breakpoint is set in
3577 the same way. However, like the @code{tbreak} command,
3578 the breakpoint is automatically deleted after the
3579 first time your program stops there. Also, like the @code{hbreak}
3580 command, the breakpoint requires hardware support and some target hardware
3581 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3582 See also @ref{Conditions, ,Break Conditions}.
3585 @cindex regular expression
3586 @cindex breakpoints at functions matching a regexp
3587 @cindex set breakpoints in many functions
3588 @item rbreak @var{regex}
3589 Set breakpoints on all functions matching the regular expression
3590 @var{regex}. This command sets an unconditional breakpoint on all
3591 matches, printing a list of all breakpoints it set. Once these
3592 breakpoints are set, they are treated just like the breakpoints set with
3593 the @code{break} command. You can delete them, disable them, or make
3594 them conditional the same way as any other breakpoint.
3596 The syntax of the regular expression is the standard one used with tools
3597 like @file{grep}. Note that this is different from the syntax used by
3598 shells, so for instance @code{foo*} matches all functions that include
3599 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3600 @code{.*} leading and trailing the regular expression you supply, so to
3601 match only functions that begin with @code{foo}, use @code{^foo}.
3603 @cindex non-member C@t{++} functions, set breakpoint in
3604 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3605 breakpoints on overloaded functions that are not members of any special
3608 @cindex set breakpoints on all functions
3609 The @code{rbreak} command can be used to set breakpoints in
3610 @strong{all} the functions in a program, like this:
3613 (@value{GDBP}) rbreak .
3616 @item rbreak @var{file}:@var{regex}
3617 If @code{rbreak} is called with a filename qualification, it limits
3618 the search for functions matching the given regular expression to the
3619 specified @var{file}. This can be used, for example, to set breakpoints on
3620 every function in a given file:
3623 (@value{GDBP}) rbreak file.c:.
3626 The colon separating the filename qualifier from the regex may
3627 optionally be surrounded by spaces.
3629 @kindex info breakpoints
3630 @cindex @code{$_} and @code{info breakpoints}
3631 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3632 @itemx info break @r{[}@var{n}@dots{}@r{]}
3633 Print a table of all breakpoints, watchpoints, and catchpoints set and
3634 not deleted. Optional argument @var{n} means print information only
3635 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3636 For each breakpoint, following columns are printed:
3639 @item Breakpoint Numbers
3641 Breakpoint, watchpoint, or catchpoint.
3643 Whether the breakpoint is marked to be disabled or deleted when hit.
3644 @item Enabled or Disabled
3645 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3646 that are not enabled.
3648 Where the breakpoint is in your program, as a memory address. For a
3649 pending breakpoint whose address is not yet known, this field will
3650 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3651 library that has the symbol or line referred by breakpoint is loaded.
3652 See below for details. A breakpoint with several locations will
3653 have @samp{<MULTIPLE>} in this field---see below for details.
3655 Where the breakpoint is in the source for your program, as a file and
3656 line number. For a pending breakpoint, the original string passed to
3657 the breakpoint command will be listed as it cannot be resolved until
3658 the appropriate shared library is loaded in the future.
3662 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3663 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3664 @value{GDBN} on the host's side. If it is ``target'', then the condition
3665 is evaluated by the target. The @code{info break} command shows
3666 the condition on the line following the affected breakpoint, together with
3667 its condition evaluation mode in between parentheses.
3669 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3670 allowed to have a condition specified for it. The condition is not parsed for
3671 validity until a shared library is loaded that allows the pending
3672 breakpoint to resolve to a valid location.
3675 @code{info break} with a breakpoint
3676 number @var{n} as argument lists only that breakpoint. The
3677 convenience variable @code{$_} and the default examining-address for
3678 the @code{x} command are set to the address of the last breakpoint
3679 listed (@pxref{Memory, ,Examining Memory}).
3682 @code{info break} displays a count of the number of times the breakpoint
3683 has been hit. This is especially useful in conjunction with the
3684 @code{ignore} command. You can ignore a large number of breakpoint
3685 hits, look at the breakpoint info to see how many times the breakpoint
3686 was hit, and then run again, ignoring one less than that number. This
3687 will get you quickly to the last hit of that breakpoint.
3690 For a breakpoints with an enable count (xref) greater than 1,
3691 @code{info break} also displays that count.
3695 @value{GDBN} allows you to set any number of breakpoints at the same place in
3696 your program. There is nothing silly or meaningless about this. When
3697 the breakpoints are conditional, this is even useful
3698 (@pxref{Conditions, ,Break Conditions}).
3700 @cindex multiple locations, breakpoints
3701 @cindex breakpoints, multiple locations
3702 It is possible that a breakpoint corresponds to several locations
3703 in your program. Examples of this situation are:
3707 Multiple functions in the program may have the same name.
3710 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3711 instances of the function body, used in different cases.
3714 For a C@t{++} template function, a given line in the function can
3715 correspond to any number of instantiations.
3718 For an inlined function, a given source line can correspond to
3719 several places where that function is inlined.
3722 In all those cases, @value{GDBN} will insert a breakpoint at all
3723 the relevant locations.
3725 A breakpoint with multiple locations is displayed in the breakpoint
3726 table using several rows---one header row, followed by one row for
3727 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3728 address column. The rows for individual locations contain the actual
3729 addresses for locations, and show the functions to which those
3730 locations belong. The number column for a location is of the form
3731 @var{breakpoint-number}.@var{location-number}.
3736 Num Type Disp Enb Address What
3737 1 breakpoint keep y <MULTIPLE>
3739 breakpoint already hit 1 time
3740 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3741 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3744 Each location can be individually enabled or disabled by passing
3745 @var{breakpoint-number}.@var{location-number} as argument to the
3746 @code{enable} and @code{disable} commands. Note that you cannot
3747 delete the individual locations from the list, you can only delete the
3748 entire list of locations that belong to their parent breakpoint (with
3749 the @kbd{delete @var{num}} command, where @var{num} is the number of
3750 the parent breakpoint, 1 in the above example). Disabling or enabling
3751 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3752 that belong to that breakpoint.
3754 @cindex pending breakpoints
3755 It's quite common to have a breakpoint inside a shared library.
3756 Shared libraries can be loaded and unloaded explicitly,
3757 and possibly repeatedly, as the program is executed. To support
3758 this use case, @value{GDBN} updates breakpoint locations whenever
3759 any shared library is loaded or unloaded. Typically, you would
3760 set a breakpoint in a shared library at the beginning of your
3761 debugging session, when the library is not loaded, and when the
3762 symbols from the library are not available. When you try to set
3763 breakpoint, @value{GDBN} will ask you if you want to set
3764 a so called @dfn{pending breakpoint}---breakpoint whose address
3765 is not yet resolved.
3767 After the program is run, whenever a new shared library is loaded,
3768 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3769 shared library contains the symbol or line referred to by some
3770 pending breakpoint, that breakpoint is resolved and becomes an
3771 ordinary breakpoint. When a library is unloaded, all breakpoints
3772 that refer to its symbols or source lines become pending again.
3774 This logic works for breakpoints with multiple locations, too. For
3775 example, if you have a breakpoint in a C@t{++} template function, and
3776 a newly loaded shared library has an instantiation of that template,
3777 a new location is added to the list of locations for the breakpoint.
3779 Except for having unresolved address, pending breakpoints do not
3780 differ from regular breakpoints. You can set conditions or commands,
3781 enable and disable them and perform other breakpoint operations.
3783 @value{GDBN} provides some additional commands for controlling what
3784 happens when the @samp{break} command cannot resolve breakpoint
3785 address specification to an address:
3787 @kindex set breakpoint pending
3788 @kindex show breakpoint pending
3790 @item set breakpoint pending auto
3791 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3792 location, it queries you whether a pending breakpoint should be created.
3794 @item set breakpoint pending on
3795 This indicates that an unrecognized breakpoint location should automatically
3796 result in a pending breakpoint being created.
3798 @item set breakpoint pending off
3799 This indicates that pending breakpoints are not to be created. Any
3800 unrecognized breakpoint location results in an error. This setting does
3801 not affect any pending breakpoints previously created.
3803 @item show breakpoint pending
3804 Show the current behavior setting for creating pending breakpoints.
3807 The settings above only affect the @code{break} command and its
3808 variants. Once breakpoint is set, it will be automatically updated
3809 as shared libraries are loaded and unloaded.
3811 @cindex automatic hardware breakpoints
3812 For some targets, @value{GDBN} can automatically decide if hardware or
3813 software breakpoints should be used, depending on whether the
3814 breakpoint address is read-only or read-write. This applies to
3815 breakpoints set with the @code{break} command as well as to internal
3816 breakpoints set by commands like @code{next} and @code{finish}. For
3817 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3820 You can control this automatic behaviour with the following commands::
3822 @kindex set breakpoint auto-hw
3823 @kindex show breakpoint auto-hw
3825 @item set breakpoint auto-hw on
3826 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3827 will try to use the target memory map to decide if software or hardware
3828 breakpoint must be used.
3830 @item set breakpoint auto-hw off
3831 This indicates @value{GDBN} should not automatically select breakpoint
3832 type. If the target provides a memory map, @value{GDBN} will warn when
3833 trying to set software breakpoint at a read-only address.
3836 @value{GDBN} normally implements breakpoints by replacing the program code
3837 at the breakpoint address with a special instruction, which, when
3838 executed, given control to the debugger. By default, the program
3839 code is so modified only when the program is resumed. As soon as
3840 the program stops, @value{GDBN} restores the original instructions. This
3841 behaviour guards against leaving breakpoints inserted in the
3842 target should gdb abrubptly disconnect. However, with slow remote
3843 targets, inserting and removing breakpoint can reduce the performance.
3844 This behavior can be controlled with the following commands::
3846 @kindex set breakpoint always-inserted
3847 @kindex show breakpoint always-inserted
3849 @item set breakpoint always-inserted off
3850 All breakpoints, including newly added by the user, are inserted in
3851 the target only when the target is resumed. All breakpoints are
3852 removed from the target when it stops.
3854 @item set breakpoint always-inserted on
3855 Causes all breakpoints to be inserted in the target at all times. If
3856 the user adds a new breakpoint, or changes an existing breakpoint, the
3857 breakpoints in the target are updated immediately. A breakpoint is
3858 removed from the target only when breakpoint itself is removed.
3860 @cindex non-stop mode, and @code{breakpoint always-inserted}
3861 @item set breakpoint always-inserted auto
3862 This is the default mode. If @value{GDBN} is controlling the inferior
3863 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3864 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3865 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3866 @code{breakpoint always-inserted} mode is off.
3869 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3870 when a breakpoint breaks. If the condition is true, then the process being
3871 debugged stops, otherwise the process is resumed.
3873 If the target supports evaluating conditions on its end, @value{GDBN} may
3874 download the breakpoint, together with its conditions, to it.
3876 This feature can be controlled via the following commands:
3878 @kindex set breakpoint condition-evaluation
3879 @kindex show breakpoint condition-evaluation
3881 @item set breakpoint condition-evaluation host
3882 This option commands @value{GDBN} to evaluate the breakpoint
3883 conditions on the host's side. Unconditional breakpoints are sent to
3884 the target which in turn receives the triggers and reports them back to GDB
3885 for condition evaluation. This is the standard evaluation mode.
3887 @item set breakpoint condition-evaluation target
3888 This option commands @value{GDBN} to download breakpoint conditions
3889 to the target at the moment of their insertion. The target
3890 is responsible for evaluating the conditional expression and reporting
3891 breakpoint stop events back to @value{GDBN} whenever the condition
3892 is true. Due to limitations of target-side evaluation, some conditions
3893 cannot be evaluated there, e.g., conditions that depend on local data
3894 that is only known to the host. Examples include
3895 conditional expressions involving convenience variables, complex types
3896 that cannot be handled by the agent expression parser and expressions
3897 that are too long to be sent over to the target, specially when the
3898 target is a remote system. In these cases, the conditions will be
3899 evaluated by @value{GDBN}.
3901 @item set breakpoint condition-evaluation auto
3902 This is the default mode. If the target supports evaluating breakpoint
3903 conditions on its end, @value{GDBN} will download breakpoint conditions to
3904 the target (limitations mentioned previously apply). If the target does
3905 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3906 to evaluating all these conditions on the host's side.
3910 @cindex negative breakpoint numbers
3911 @cindex internal @value{GDBN} breakpoints
3912 @value{GDBN} itself sometimes sets breakpoints in your program for
3913 special purposes, such as proper handling of @code{longjmp} (in C
3914 programs). These internal breakpoints are assigned negative numbers,
3915 starting with @code{-1}; @samp{info breakpoints} does not display them.
3916 You can see these breakpoints with the @value{GDBN} maintenance command
3917 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3920 @node Set Watchpoints
3921 @subsection Setting Watchpoints
3923 @cindex setting watchpoints
3924 You can use a watchpoint to stop execution whenever the value of an
3925 expression changes, without having to predict a particular place where
3926 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3927 The expression may be as simple as the value of a single variable, or
3928 as complex as many variables combined by operators. Examples include:
3932 A reference to the value of a single variable.
3935 An address cast to an appropriate data type. For example,
3936 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3937 address (assuming an @code{int} occupies 4 bytes).
3940 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3941 expression can use any operators valid in the program's native
3942 language (@pxref{Languages}).
3945 You can set a watchpoint on an expression even if the expression can
3946 not be evaluated yet. For instance, you can set a watchpoint on
3947 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3948 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3949 the expression produces a valid value. If the expression becomes
3950 valid in some other way than changing a variable (e.g.@: if the memory
3951 pointed to by @samp{*global_ptr} becomes readable as the result of a
3952 @code{malloc} call), @value{GDBN} may not stop until the next time
3953 the expression changes.
3955 @cindex software watchpoints
3956 @cindex hardware watchpoints
3957 Depending on your system, watchpoints may be implemented in software or
3958 hardware. @value{GDBN} does software watchpointing by single-stepping your
3959 program and testing the variable's value each time, which is hundreds of
3960 times slower than normal execution. (But this may still be worth it, to
3961 catch errors where you have no clue what part of your program is the
3964 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3965 x86-based targets, @value{GDBN} includes support for hardware
3966 watchpoints, which do not slow down the running of your program.
3970 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3971 Set a watchpoint for an expression. @value{GDBN} will break when the
3972 expression @var{expr} is written into by the program and its value
3973 changes. The simplest (and the most popular) use of this command is
3974 to watch the value of a single variable:
3977 (@value{GDBP}) watch foo
3980 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3981 argument, @value{GDBN} breaks only when the thread identified by
3982 @var{threadnum} changes the value of @var{expr}. If any other threads
3983 change the value of @var{expr}, @value{GDBN} will not break. Note
3984 that watchpoints restricted to a single thread in this way only work
3985 with Hardware Watchpoints.
3987 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3988 (see below). The @code{-location} argument tells @value{GDBN} to
3989 instead watch the memory referred to by @var{expr}. In this case,
3990 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3991 and watch the memory at that address. The type of the result is used
3992 to determine the size of the watched memory. If the expression's
3993 result does not have an address, then @value{GDBN} will print an
3996 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3997 of masked watchpoints, if the current architecture supports this
3998 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3999 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4000 to an address to watch. The mask specifies that some bits of an address
4001 (the bits which are reset in the mask) should be ignored when matching
4002 the address accessed by the inferior against the watchpoint address.
4003 Thus, a masked watchpoint watches many addresses simultaneously---those
4004 addresses whose unmasked bits are identical to the unmasked bits in the
4005 watchpoint address. The @code{mask} argument implies @code{-location}.
4009 (@value{GDBP}) watch foo mask 0xffff00ff
4010 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4014 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4015 Set a watchpoint that will break when the value of @var{expr} is read
4019 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4020 Set a watchpoint that will break when @var{expr} is either read from
4021 or written into by the program.
4023 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4024 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4025 This command prints a list of watchpoints, using the same format as
4026 @code{info break} (@pxref{Set Breaks}).
4029 If you watch for a change in a numerically entered address you need to
4030 dereference it, as the address itself is just a constant number which will
4031 never change. @value{GDBN} refuses to create a watchpoint that watches
4032 a never-changing value:
4035 (@value{GDBP}) watch 0x600850
4036 Cannot watch constant value 0x600850.
4037 (@value{GDBP}) watch *(int *) 0x600850
4038 Watchpoint 1: *(int *) 6293584
4041 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4042 watchpoints execute very quickly, and the debugger reports a change in
4043 value at the exact instruction where the change occurs. If @value{GDBN}
4044 cannot set a hardware watchpoint, it sets a software watchpoint, which
4045 executes more slowly and reports the change in value at the next
4046 @emph{statement}, not the instruction, after the change occurs.
4048 @cindex use only software watchpoints
4049 You can force @value{GDBN} to use only software watchpoints with the
4050 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4051 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4052 the underlying system supports them. (Note that hardware-assisted
4053 watchpoints that were set @emph{before} setting
4054 @code{can-use-hw-watchpoints} to zero will still use the hardware
4055 mechanism of watching expression values.)
4058 @item set can-use-hw-watchpoints
4059 @kindex set can-use-hw-watchpoints
4060 Set whether or not to use hardware watchpoints.
4062 @item show can-use-hw-watchpoints
4063 @kindex show can-use-hw-watchpoints
4064 Show the current mode of using hardware watchpoints.
4067 For remote targets, you can restrict the number of hardware
4068 watchpoints @value{GDBN} will use, see @ref{set remote
4069 hardware-breakpoint-limit}.
4071 When you issue the @code{watch} command, @value{GDBN} reports
4074 Hardware watchpoint @var{num}: @var{expr}
4078 if it was able to set a hardware watchpoint.
4080 Currently, the @code{awatch} and @code{rwatch} commands can only set
4081 hardware watchpoints, because accesses to data that don't change the
4082 value of the watched expression cannot be detected without examining
4083 every instruction as it is being executed, and @value{GDBN} does not do
4084 that currently. If @value{GDBN} finds that it is unable to set a
4085 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4086 will print a message like this:
4089 Expression cannot be implemented with read/access watchpoint.
4092 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4093 data type of the watched expression is wider than what a hardware
4094 watchpoint on the target machine can handle. For example, some systems
4095 can only watch regions that are up to 4 bytes wide; on such systems you
4096 cannot set hardware watchpoints for an expression that yields a
4097 double-precision floating-point number (which is typically 8 bytes
4098 wide). As a work-around, it might be possible to break the large region
4099 into a series of smaller ones and watch them with separate watchpoints.
4101 If you set too many hardware watchpoints, @value{GDBN} might be unable
4102 to insert all of them when you resume the execution of your program.
4103 Since the precise number of active watchpoints is unknown until such
4104 time as the program is about to be resumed, @value{GDBN} might not be
4105 able to warn you about this when you set the watchpoints, and the
4106 warning will be printed only when the program is resumed:
4109 Hardware watchpoint @var{num}: Could not insert watchpoint
4113 If this happens, delete or disable some of the watchpoints.
4115 Watching complex expressions that reference many variables can also
4116 exhaust the resources available for hardware-assisted watchpoints.
4117 That's because @value{GDBN} needs to watch every variable in the
4118 expression with separately allocated resources.
4120 If you call a function interactively using @code{print} or @code{call},
4121 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4122 kind of breakpoint or the call completes.
4124 @value{GDBN} automatically deletes watchpoints that watch local
4125 (automatic) variables, or expressions that involve such variables, when
4126 they go out of scope, that is, when the execution leaves the block in
4127 which these variables were defined. In particular, when the program
4128 being debugged terminates, @emph{all} local variables go out of scope,
4129 and so only watchpoints that watch global variables remain set. If you
4130 rerun the program, you will need to set all such watchpoints again. One
4131 way of doing that would be to set a code breakpoint at the entry to the
4132 @code{main} function and when it breaks, set all the watchpoints.
4134 @cindex watchpoints and threads
4135 @cindex threads and watchpoints
4136 In multi-threaded programs, watchpoints will detect changes to the
4137 watched expression from every thread.
4140 @emph{Warning:} In multi-threaded programs, software watchpoints
4141 have only limited usefulness. If @value{GDBN} creates a software
4142 watchpoint, it can only watch the value of an expression @emph{in a
4143 single thread}. If you are confident that the expression can only
4144 change due to the current thread's activity (and if you are also
4145 confident that no other thread can become current), then you can use
4146 software watchpoints as usual. However, @value{GDBN} may not notice
4147 when a non-current thread's activity changes the expression. (Hardware
4148 watchpoints, in contrast, watch an expression in all threads.)
4151 @xref{set remote hardware-watchpoint-limit}.
4153 @node Set Catchpoints
4154 @subsection Setting Catchpoints
4155 @cindex catchpoints, setting
4156 @cindex exception handlers
4157 @cindex event handling
4159 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4160 kinds of program events, such as C@t{++} exceptions or the loading of a
4161 shared library. Use the @code{catch} command to set a catchpoint.
4165 @item catch @var{event}
4166 Stop when @var{event} occurs. The @var{event} can be any of the following:
4169 @item throw @r{[}@var{regexp}@r{]}
4170 @itemx rethrow @r{[}@var{regexp}@r{]}
4171 @itemx catch @r{[}@var{regexp}@r{]}
4173 @kindex catch rethrow
4175 @cindex stop on C@t{++} exceptions
4176 The throwing, re-throwing, or catching of a C@t{++} exception.
4178 If @var{regexp} is given, then only exceptions whose type matches the
4179 regular expression will be caught.
4181 @vindex $_exception@r{, convenience variable}
4182 The convenience variable @code{$_exception} is available at an
4183 exception-related catchpoint, on some systems. This holds the
4184 exception being thrown.
4186 There are currently some limitations to C@t{++} exception handling in
4191 The support for these commands is system-dependent. Currently, only
4192 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4196 The regular expression feature and the @code{$_exception} convenience
4197 variable rely on the presence of some SDT probes in @code{libstdc++}.
4198 If these probes are not present, then these features cannot be used.
4199 These probes were first available in the GCC 4.8 release, but whether
4200 or not they are available in your GCC also depends on how it was
4204 The @code{$_exception} convenience variable is only valid at the
4205 instruction at which an exception-related catchpoint is set.
4208 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4209 location in the system library which implements runtime exception
4210 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4211 (@pxref{Selection}) to get to your code.
4214 If you call a function interactively, @value{GDBN} normally returns
4215 control to you when the function has finished executing. If the call
4216 raises an exception, however, the call may bypass the mechanism that
4217 returns control to you and cause your program either to abort or to
4218 simply continue running until it hits a breakpoint, catches a signal
4219 that @value{GDBN} is listening for, or exits. This is the case even if
4220 you set a catchpoint for the exception; catchpoints on exceptions are
4221 disabled within interactive calls. @xref{Calling}, for information on
4222 controlling this with @code{set unwind-on-terminating-exception}.
4225 You cannot raise an exception interactively.
4228 You cannot install an exception handler interactively.
4232 @kindex catch exception
4233 @cindex Ada exception catching
4234 @cindex catch Ada exceptions
4235 An Ada exception being raised. If an exception name is specified
4236 at the end of the command (eg @code{catch exception Program_Error}),
4237 the debugger will stop only when this specific exception is raised.
4238 Otherwise, the debugger stops execution when any Ada exception is raised.
4240 When inserting an exception catchpoint on a user-defined exception whose
4241 name is identical to one of the exceptions defined by the language, the
4242 fully qualified name must be used as the exception name. Otherwise,
4243 @value{GDBN} will assume that it should stop on the pre-defined exception
4244 rather than the user-defined one. For instance, assuming an exception
4245 called @code{Constraint_Error} is defined in package @code{Pck}, then
4246 the command to use to catch such exceptions is @kbd{catch exception
4247 Pck.Constraint_Error}.
4249 @item exception unhandled
4250 @kindex catch exception unhandled
4251 An exception that was raised but is not handled by the program.
4254 @kindex catch assert
4255 A failed Ada assertion.
4259 @cindex break on fork/exec
4260 A call to @code{exec}. This is currently only available for HP-UX
4264 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4265 @kindex catch syscall
4266 @cindex break on a system call.
4267 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4268 syscall is a mechanism for application programs to request a service
4269 from the operating system (OS) or one of the OS system services.
4270 @value{GDBN} can catch some or all of the syscalls issued by the
4271 debuggee, and show the related information for each syscall. If no
4272 argument is specified, calls to and returns from all system calls
4275 @var{name} can be any system call name that is valid for the
4276 underlying OS. Just what syscalls are valid depends on the OS. On
4277 GNU and Unix systems, you can find the full list of valid syscall
4278 names on @file{/usr/include/asm/unistd.h}.
4280 @c For MS-Windows, the syscall names and the corresponding numbers
4281 @c can be found, e.g., on this URL:
4282 @c http://www.metasploit.com/users/opcode/syscalls.html
4283 @c but we don't support Windows syscalls yet.
4285 Normally, @value{GDBN} knows in advance which syscalls are valid for
4286 each OS, so you can use the @value{GDBN} command-line completion
4287 facilities (@pxref{Completion,, command completion}) to list the
4290 You may also specify the system call numerically. A syscall's
4291 number is the value passed to the OS's syscall dispatcher to
4292 identify the requested service. When you specify the syscall by its
4293 name, @value{GDBN} uses its database of syscalls to convert the name
4294 into the corresponding numeric code, but using the number directly
4295 may be useful if @value{GDBN}'s database does not have the complete
4296 list of syscalls on your system (e.g., because @value{GDBN} lags
4297 behind the OS upgrades).
4299 The example below illustrates how this command works if you don't provide
4303 (@value{GDBP}) catch syscall
4304 Catchpoint 1 (syscall)
4306 Starting program: /tmp/catch-syscall
4308 Catchpoint 1 (call to syscall 'close'), \
4309 0xffffe424 in __kernel_vsyscall ()
4313 Catchpoint 1 (returned from syscall 'close'), \
4314 0xffffe424 in __kernel_vsyscall ()
4318 Here is an example of catching a system call by name:
4321 (@value{GDBP}) catch syscall chroot
4322 Catchpoint 1 (syscall 'chroot' [61])
4324 Starting program: /tmp/catch-syscall
4326 Catchpoint 1 (call to syscall 'chroot'), \
4327 0xffffe424 in __kernel_vsyscall ()
4331 Catchpoint 1 (returned from syscall 'chroot'), \
4332 0xffffe424 in __kernel_vsyscall ()
4336 An example of specifying a system call numerically. In the case
4337 below, the syscall number has a corresponding entry in the XML
4338 file, so @value{GDBN} finds its name and prints it:
4341 (@value{GDBP}) catch syscall 252
4342 Catchpoint 1 (syscall(s) 'exit_group')
4344 Starting program: /tmp/catch-syscall
4346 Catchpoint 1 (call to syscall 'exit_group'), \
4347 0xffffe424 in __kernel_vsyscall ()
4351 Program exited normally.
4355 However, there can be situations when there is no corresponding name
4356 in XML file for that syscall number. In this case, @value{GDBN} prints
4357 a warning message saying that it was not able to find the syscall name,
4358 but the catchpoint will be set anyway. See the example below:
4361 (@value{GDBP}) catch syscall 764
4362 warning: The number '764' does not represent a known syscall.
4363 Catchpoint 2 (syscall 764)
4367 If you configure @value{GDBN} using the @samp{--without-expat} option,
4368 it will not be able to display syscall names. Also, if your
4369 architecture does not have an XML file describing its system calls,
4370 you will not be able to see the syscall names. It is important to
4371 notice that these two features are used for accessing the syscall
4372 name database. In either case, you will see a warning like this:
4375 (@value{GDBP}) catch syscall
4376 warning: Could not open "syscalls/i386-linux.xml"
4377 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4378 GDB will not be able to display syscall names.
4379 Catchpoint 1 (syscall)
4383 Of course, the file name will change depending on your architecture and system.
4385 Still using the example above, you can also try to catch a syscall by its
4386 number. In this case, you would see something like:
4389 (@value{GDBP}) catch syscall 252
4390 Catchpoint 1 (syscall(s) 252)
4393 Again, in this case @value{GDBN} would not be able to display syscall's names.
4397 A call to @code{fork}. This is currently only available for HP-UX
4402 A call to @code{vfork}. This is currently only available for HP-UX
4405 @item load @r{[}regexp@r{]}
4406 @itemx unload @r{[}regexp@r{]}
4408 @kindex catch unload
4409 The loading or unloading of a shared library. If @var{regexp} is
4410 given, then the catchpoint will stop only if the regular expression
4411 matches one of the affected libraries.
4413 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4414 @kindex catch signal
4415 The delivery of a signal.
4417 With no arguments, this catchpoint will catch any signal that is not
4418 used internally by @value{GDBN}, specifically, all signals except
4419 @samp{SIGTRAP} and @samp{SIGINT}.
4421 With the argument @samp{all}, all signals, including those used by
4422 @value{GDBN}, will be caught. This argument cannot be used with other
4425 Otherwise, the arguments are a list of signal names as given to
4426 @code{handle} (@pxref{Signals}). Only signals specified in this list
4429 One reason that @code{catch signal} can be more useful than
4430 @code{handle} is that you can attach commands and conditions to the
4433 When a signal is caught by a catchpoint, the signal's @code{stop} and
4434 @code{print} settings, as specified by @code{handle}, are ignored.
4435 However, whether the signal is still delivered to the inferior depends
4436 on the @code{pass} setting; this can be changed in the catchpoint's
4441 @item tcatch @var{event}
4443 Set a catchpoint that is enabled only for one stop. The catchpoint is
4444 automatically deleted after the first time the event is caught.
4448 Use the @code{info break} command to list the current catchpoints.
4452 @subsection Deleting Breakpoints
4454 @cindex clearing breakpoints, watchpoints, catchpoints
4455 @cindex deleting breakpoints, watchpoints, catchpoints
4456 It is often necessary to eliminate a breakpoint, watchpoint, or
4457 catchpoint once it has done its job and you no longer want your program
4458 to stop there. This is called @dfn{deleting} the breakpoint. A
4459 breakpoint that has been deleted no longer exists; it is forgotten.
4461 With the @code{clear} command you can delete breakpoints according to
4462 where they are in your program. With the @code{delete} command you can
4463 delete individual breakpoints, watchpoints, or catchpoints by specifying
4464 their breakpoint numbers.
4466 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4467 automatically ignores breakpoints on the first instruction to be executed
4468 when you continue execution without changing the execution address.
4473 Delete any breakpoints at the next instruction to be executed in the
4474 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4475 the innermost frame is selected, this is a good way to delete a
4476 breakpoint where your program just stopped.
4478 @item clear @var{location}
4479 Delete any breakpoints set at the specified @var{location}.
4480 @xref{Specify Location}, for the various forms of @var{location}; the
4481 most useful ones are listed below:
4484 @item clear @var{function}
4485 @itemx clear @var{filename}:@var{function}
4486 Delete any breakpoints set at entry to the named @var{function}.
4488 @item clear @var{linenum}
4489 @itemx clear @var{filename}:@var{linenum}
4490 Delete any breakpoints set at or within the code of the specified
4491 @var{linenum} of the specified @var{filename}.
4494 @cindex delete breakpoints
4496 @kindex d @r{(@code{delete})}
4497 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4498 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4499 ranges specified as arguments. If no argument is specified, delete all
4500 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4501 confirm off}). You can abbreviate this command as @code{d}.
4505 @subsection Disabling Breakpoints
4507 @cindex enable/disable a breakpoint
4508 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4509 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4510 it had been deleted, but remembers the information on the breakpoint so
4511 that you can @dfn{enable} it again later.
4513 You disable and enable breakpoints, watchpoints, and catchpoints with
4514 the @code{enable} and @code{disable} commands, optionally specifying
4515 one or more breakpoint numbers as arguments. Use @code{info break} to
4516 print a list of all breakpoints, watchpoints, and catchpoints if you
4517 do not know which numbers to use.
4519 Disabling and enabling a breakpoint that has multiple locations
4520 affects all of its locations.
4522 A breakpoint, watchpoint, or catchpoint can have any of several
4523 different states of enablement:
4527 Enabled. The breakpoint stops your program. A breakpoint set
4528 with the @code{break} command starts out in this state.
4530 Disabled. The breakpoint has no effect on your program.
4532 Enabled once. The breakpoint stops your program, but then becomes
4535 Enabled for a count. The breakpoint stops your program for the next
4536 N times, then becomes disabled.
4538 Enabled for deletion. The breakpoint stops your program, but
4539 immediately after it does so it is deleted permanently. A breakpoint
4540 set with the @code{tbreak} command starts out in this state.
4543 You can use the following commands to enable or disable breakpoints,
4544 watchpoints, and catchpoints:
4548 @kindex dis @r{(@code{disable})}
4549 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4550 Disable the specified breakpoints---or all breakpoints, if none are
4551 listed. A disabled breakpoint has no effect but is not forgotten. All
4552 options such as ignore-counts, conditions and commands are remembered in
4553 case the breakpoint is enabled again later. You may abbreviate
4554 @code{disable} as @code{dis}.
4557 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4558 Enable the specified breakpoints (or all defined breakpoints). They
4559 become effective once again in stopping your program.
4561 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4562 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4563 of these breakpoints immediately after stopping your program.
4565 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4566 Enable the specified breakpoints temporarily. @value{GDBN} records
4567 @var{count} with each of the specified breakpoints, and decrements a
4568 breakpoint's count when it is hit. When any count reaches 0,
4569 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4570 count (@pxref{Conditions, ,Break Conditions}), that will be
4571 decremented to 0 before @var{count} is affected.
4573 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4574 Enable the specified breakpoints to work once, then die. @value{GDBN}
4575 deletes any of these breakpoints as soon as your program stops there.
4576 Breakpoints set by the @code{tbreak} command start out in this state.
4579 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4580 @c confusing: tbreak is also initially enabled.
4581 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4582 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4583 subsequently, they become disabled or enabled only when you use one of
4584 the commands above. (The command @code{until} can set and delete a
4585 breakpoint of its own, but it does not change the state of your other
4586 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4590 @subsection Break Conditions
4591 @cindex conditional breakpoints
4592 @cindex breakpoint conditions
4594 @c FIXME what is scope of break condition expr? Context where wanted?
4595 @c in particular for a watchpoint?
4596 The simplest sort of breakpoint breaks every time your program reaches a
4597 specified place. You can also specify a @dfn{condition} for a
4598 breakpoint. A condition is just a Boolean expression in your
4599 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4600 a condition evaluates the expression each time your program reaches it,
4601 and your program stops only if the condition is @emph{true}.
4603 This is the converse of using assertions for program validation; in that
4604 situation, you want to stop when the assertion is violated---that is,
4605 when the condition is false. In C, if you want to test an assertion expressed
4606 by the condition @var{assert}, you should set the condition
4607 @samp{! @var{assert}} on the appropriate breakpoint.
4609 Conditions are also accepted for watchpoints; you may not need them,
4610 since a watchpoint is inspecting the value of an expression anyhow---but
4611 it might be simpler, say, to just set a watchpoint on a variable name,
4612 and specify a condition that tests whether the new value is an interesting
4615 Break conditions can have side effects, and may even call functions in
4616 your program. This can be useful, for example, to activate functions
4617 that log program progress, or to use your own print functions to
4618 format special data structures. The effects are completely predictable
4619 unless there is another enabled breakpoint at the same address. (In
4620 that case, @value{GDBN} might see the other breakpoint first and stop your
4621 program without checking the condition of this one.) Note that
4622 breakpoint commands are usually more convenient and flexible than break
4624 purpose of performing side effects when a breakpoint is reached
4625 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4627 Breakpoint conditions can also be evaluated on the target's side if
4628 the target supports it. Instead of evaluating the conditions locally,
4629 @value{GDBN} encodes the expression into an agent expression
4630 (@pxref{Agent Expressions}) suitable for execution on the target,
4631 independently of @value{GDBN}. Global variables become raw memory
4632 locations, locals become stack accesses, and so forth.
4634 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4635 when its condition evaluates to true. This mechanism may provide faster
4636 response times depending on the performance characteristics of the target
4637 since it does not need to keep @value{GDBN} informed about
4638 every breakpoint trigger, even those with false conditions.
4640 Break conditions can be specified when a breakpoint is set, by using
4641 @samp{if} in the arguments to the @code{break} command. @xref{Set
4642 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4643 with the @code{condition} command.
4645 You can also use the @code{if} keyword with the @code{watch} command.
4646 The @code{catch} command does not recognize the @code{if} keyword;
4647 @code{condition} is the only way to impose a further condition on a
4652 @item condition @var{bnum} @var{expression}
4653 Specify @var{expression} as the break condition for breakpoint,
4654 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4655 breakpoint @var{bnum} stops your program only if the value of
4656 @var{expression} is true (nonzero, in C). When you use
4657 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4658 syntactic correctness, and to determine whether symbols in it have
4659 referents in the context of your breakpoint. If @var{expression} uses
4660 symbols not referenced in the context of the breakpoint, @value{GDBN}
4661 prints an error message:
4664 No symbol "foo" in current context.
4669 not actually evaluate @var{expression} at the time the @code{condition}
4670 command (or a command that sets a breakpoint with a condition, like
4671 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4673 @item condition @var{bnum}
4674 Remove the condition from breakpoint number @var{bnum}. It becomes
4675 an ordinary unconditional breakpoint.
4678 @cindex ignore count (of breakpoint)
4679 A special case of a breakpoint condition is to stop only when the
4680 breakpoint has been reached a certain number of times. This is so
4681 useful that there is a special way to do it, using the @dfn{ignore
4682 count} of the breakpoint. Every breakpoint has an ignore count, which
4683 is an integer. Most of the time, the ignore count is zero, and
4684 therefore has no effect. But if your program reaches a breakpoint whose
4685 ignore count is positive, then instead of stopping, it just decrements
4686 the ignore count by one and continues. As a result, if the ignore count
4687 value is @var{n}, the breakpoint does not stop the next @var{n} times
4688 your program reaches it.
4692 @item ignore @var{bnum} @var{count}
4693 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4694 The next @var{count} times the breakpoint is reached, your program's
4695 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4698 To make the breakpoint stop the next time it is reached, specify
4701 When you use @code{continue} to resume execution of your program from a
4702 breakpoint, you can specify an ignore count directly as an argument to
4703 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4704 Stepping,,Continuing and Stepping}.
4706 If a breakpoint has a positive ignore count and a condition, the
4707 condition is not checked. Once the ignore count reaches zero,
4708 @value{GDBN} resumes checking the condition.
4710 You could achieve the effect of the ignore count with a condition such
4711 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4712 is decremented each time. @xref{Convenience Vars, ,Convenience
4716 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4719 @node Break Commands
4720 @subsection Breakpoint Command Lists
4722 @cindex breakpoint commands
4723 You can give any breakpoint (or watchpoint or catchpoint) a series of
4724 commands to execute when your program stops due to that breakpoint. For
4725 example, you might want to print the values of certain expressions, or
4726 enable other breakpoints.
4730 @kindex end@r{ (breakpoint commands)}
4731 @item commands @r{[}@var{range}@dots{}@r{]}
4732 @itemx @dots{} @var{command-list} @dots{}
4734 Specify a list of commands for the given breakpoints. The commands
4735 themselves appear on the following lines. Type a line containing just
4736 @code{end} to terminate the commands.
4738 To remove all commands from a breakpoint, type @code{commands} and
4739 follow it immediately with @code{end}; that is, give no commands.
4741 With no argument, @code{commands} refers to the last breakpoint,
4742 watchpoint, or catchpoint set (not to the breakpoint most recently
4743 encountered). If the most recent breakpoints were set with a single
4744 command, then the @code{commands} will apply to all the breakpoints
4745 set by that command. This applies to breakpoints set by
4746 @code{rbreak}, and also applies when a single @code{break} command
4747 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4751 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4752 disabled within a @var{command-list}.
4754 You can use breakpoint commands to start your program up again. Simply
4755 use the @code{continue} command, or @code{step}, or any other command
4756 that resumes execution.
4758 Any other commands in the command list, after a command that resumes
4759 execution, are ignored. This is because any time you resume execution
4760 (even with a simple @code{next} or @code{step}), you may encounter
4761 another breakpoint---which could have its own command list, leading to
4762 ambiguities about which list to execute.
4765 If the first command you specify in a command list is @code{silent}, the
4766 usual message about stopping at a breakpoint is not printed. This may
4767 be desirable for breakpoints that are to print a specific message and
4768 then continue. If none of the remaining commands print anything, you
4769 see no sign that the breakpoint was reached. @code{silent} is
4770 meaningful only at the beginning of a breakpoint command list.
4772 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4773 print precisely controlled output, and are often useful in silent
4774 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4776 For example, here is how you could use breakpoint commands to print the
4777 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4783 printf "x is %d\n",x
4788 One application for breakpoint commands is to compensate for one bug so
4789 you can test for another. Put a breakpoint just after the erroneous line
4790 of code, give it a condition to detect the case in which something
4791 erroneous has been done, and give it commands to assign correct values
4792 to any variables that need them. End with the @code{continue} command
4793 so that your program does not stop, and start with the @code{silent}
4794 command so that no output is produced. Here is an example:
4805 @node Dynamic Printf
4806 @subsection Dynamic Printf
4808 @cindex dynamic printf
4810 The dynamic printf command @code{dprintf} combines a breakpoint with
4811 formatted printing of your program's data to give you the effect of
4812 inserting @code{printf} calls into your program on-the-fly, without
4813 having to recompile it.
4815 In its most basic form, the output goes to the GDB console. However,
4816 you can set the variable @code{dprintf-style} for alternate handling.
4817 For instance, you can ask to format the output by calling your
4818 program's @code{printf} function. This has the advantage that the
4819 characters go to the program's output device, so they can recorded in
4820 redirects to files and so forth.
4822 If you are doing remote debugging with a stub or agent, you can also
4823 ask to have the printf handled by the remote agent. In addition to
4824 ensuring that the output goes to the remote program's device along
4825 with any other output the program might produce, you can also ask that
4826 the dprintf remain active even after disconnecting from the remote
4827 target. Using the stub/agent is also more efficient, as it can do
4828 everything without needing to communicate with @value{GDBN}.
4832 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4833 Whenever execution reaches @var{location}, print the values of one or
4834 more @var{expressions} under the control of the string @var{template}.
4835 To print several values, separate them with commas.
4837 @item set dprintf-style @var{style}
4838 Set the dprintf output to be handled in one of several different
4839 styles enumerated below. A change of style affects all existing
4840 dynamic printfs immediately. (If you need individual control over the
4841 print commands, simply define normal breakpoints with
4842 explicitly-supplied command lists.)
4845 @kindex dprintf-style gdb
4846 Handle the output using the @value{GDBN} @code{printf} command.
4849 @kindex dprintf-style call
4850 Handle the output by calling a function in your program (normally
4854 @kindex dprintf-style agent
4855 Have the remote debugging agent (such as @code{gdbserver}) handle
4856 the output itself. This style is only available for agents that
4857 support running commands on the target.
4859 @item set dprintf-function @var{function}
4860 Set the function to call if the dprintf style is @code{call}. By
4861 default its value is @code{printf}. You may set it to any expression.
4862 that @value{GDBN} can evaluate to a function, as per the @code{call}
4865 @item set dprintf-channel @var{channel}
4866 Set a ``channel'' for dprintf. If set to a non-empty value,
4867 @value{GDBN} will evaluate it as an expression and pass the result as
4868 a first argument to the @code{dprintf-function}, in the manner of
4869 @code{fprintf} and similar functions. Otherwise, the dprintf format
4870 string will be the first argument, in the manner of @code{printf}.
4872 As an example, if you wanted @code{dprintf} output to go to a logfile
4873 that is a standard I/O stream assigned to the variable @code{mylog},
4874 you could do the following:
4877 (gdb) set dprintf-style call
4878 (gdb) set dprintf-function fprintf
4879 (gdb) set dprintf-channel mylog
4880 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4881 Dprintf 1 at 0x123456: file main.c, line 25.
4883 1 dprintf keep y 0x00123456 in main at main.c:25
4884 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4889 Note that the @code{info break} displays the dynamic printf commands
4890 as normal breakpoint commands; you can thus easily see the effect of
4891 the variable settings.
4893 @item set disconnected-dprintf on
4894 @itemx set disconnected-dprintf off
4895 @kindex set disconnected-dprintf
4896 Choose whether @code{dprintf} commands should continue to run if
4897 @value{GDBN} has disconnected from the target. This only applies
4898 if the @code{dprintf-style} is @code{agent}.
4900 @item show disconnected-dprintf off
4901 @kindex show disconnected-dprintf
4902 Show the current choice for disconnected @code{dprintf}.
4906 @value{GDBN} does not check the validity of function and channel,
4907 relying on you to supply values that are meaningful for the contexts
4908 in which they are being used. For instance, the function and channel
4909 may be the values of local variables, but if that is the case, then
4910 all enabled dynamic prints must be at locations within the scope of
4911 those locals. If evaluation fails, @value{GDBN} will report an error.
4913 @node Save Breakpoints
4914 @subsection How to save breakpoints to a file
4916 To save breakpoint definitions to a file use the @w{@code{save
4917 breakpoints}} command.
4920 @kindex save breakpoints
4921 @cindex save breakpoints to a file for future sessions
4922 @item save breakpoints [@var{filename}]
4923 This command saves all current breakpoint definitions together with
4924 their commands and ignore counts, into a file @file{@var{filename}}
4925 suitable for use in a later debugging session. This includes all
4926 types of breakpoints (breakpoints, watchpoints, catchpoints,
4927 tracepoints). To read the saved breakpoint definitions, use the
4928 @code{source} command (@pxref{Command Files}). Note that watchpoints
4929 with expressions involving local variables may fail to be recreated
4930 because it may not be possible to access the context where the
4931 watchpoint is valid anymore. Because the saved breakpoint definitions
4932 are simply a sequence of @value{GDBN} commands that recreate the
4933 breakpoints, you can edit the file in your favorite editing program,
4934 and remove the breakpoint definitions you're not interested in, or
4935 that can no longer be recreated.
4938 @node Static Probe Points
4939 @subsection Static Probe Points
4941 @cindex static probe point, SystemTap
4942 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4943 for Statically Defined Tracing, and the probes are designed to have a tiny
4944 runtime code and data footprint, and no dynamic relocations. They are
4945 usable from assembly, C and C@t{++} languages. See
4946 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4947 for a good reference on how the @acronym{SDT} probes are implemented.
4949 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4950 @acronym{SDT} probes are supported on ELF-compatible systems. See
4951 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4952 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4953 in your applications.
4955 @cindex semaphores on static probe points
4956 Some probes have an associated semaphore variable; for instance, this
4957 happens automatically if you defined your probe using a DTrace-style
4958 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4959 automatically enable it when you specify a breakpoint using the
4960 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4961 location by some other method (e.g., @code{break file:line}), then
4962 @value{GDBN} will not automatically set the semaphore.
4964 You can examine the available static static probes using @code{info
4965 probes}, with optional arguments:
4969 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4970 If given, @var{provider} is a regular expression used to match against provider
4971 names when selecting which probes to list. If omitted, probes by all
4972 probes from all providers are listed.
4974 If given, @var{name} is a regular expression to match against probe names
4975 when selecting which probes to list. If omitted, probe names are not
4976 considered when deciding whether to display them.
4978 If given, @var{objfile} is a regular expression used to select which
4979 object files (executable or shared libraries) to examine. If not
4980 given, all object files are considered.
4982 @item info probes all
4983 List the available static probes, from all types.
4986 @vindex $_probe_arg@r{, convenience variable}
4987 A probe may specify up to twelve arguments. These are available at the
4988 point at which the probe is defined---that is, when the current PC is
4989 at the probe's location. The arguments are available using the
4990 convenience variables (@pxref{Convenience Vars})
4991 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4992 an integer of the appropriate size; types are not preserved. The
4993 convenience variable @code{$_probe_argc} holds the number of arguments
4994 at the current probe point.
4996 These variables are always available, but attempts to access them at
4997 any location other than a probe point will cause @value{GDBN} to give
5001 @c @ifclear BARETARGET
5002 @node Error in Breakpoints
5003 @subsection ``Cannot insert breakpoints''
5005 If you request too many active hardware-assisted breakpoints and
5006 watchpoints, you will see this error message:
5008 @c FIXME: the precise wording of this message may change; the relevant
5009 @c source change is not committed yet (Sep 3, 1999).
5011 Stopped; cannot insert breakpoints.
5012 You may have requested too many hardware breakpoints and watchpoints.
5016 This message is printed when you attempt to resume the program, since
5017 only then @value{GDBN} knows exactly how many hardware breakpoints and
5018 watchpoints it needs to insert.
5020 When this message is printed, you need to disable or remove some of the
5021 hardware-assisted breakpoints and watchpoints, and then continue.
5023 @node Breakpoint-related Warnings
5024 @subsection ``Breakpoint address adjusted...''
5025 @cindex breakpoint address adjusted
5027 Some processor architectures place constraints on the addresses at
5028 which breakpoints may be placed. For architectures thus constrained,
5029 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5030 with the constraints dictated by the architecture.
5032 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5033 a VLIW architecture in which a number of RISC-like instructions may be
5034 bundled together for parallel execution. The FR-V architecture
5035 constrains the location of a breakpoint instruction within such a
5036 bundle to the instruction with the lowest address. @value{GDBN}
5037 honors this constraint by adjusting a breakpoint's address to the
5038 first in the bundle.
5040 It is not uncommon for optimized code to have bundles which contain
5041 instructions from different source statements, thus it may happen that
5042 a breakpoint's address will be adjusted from one source statement to
5043 another. Since this adjustment may significantly alter @value{GDBN}'s
5044 breakpoint related behavior from what the user expects, a warning is
5045 printed when the breakpoint is first set and also when the breakpoint
5048 A warning like the one below is printed when setting a breakpoint
5049 that's been subject to address adjustment:
5052 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5055 Such warnings are printed both for user settable and @value{GDBN}'s
5056 internal breakpoints. If you see one of these warnings, you should
5057 verify that a breakpoint set at the adjusted address will have the
5058 desired affect. If not, the breakpoint in question may be removed and
5059 other breakpoints may be set which will have the desired behavior.
5060 E.g., it may be sufficient to place the breakpoint at a later
5061 instruction. A conditional breakpoint may also be useful in some
5062 cases to prevent the breakpoint from triggering too often.
5064 @value{GDBN} will also issue a warning when stopping at one of these
5065 adjusted breakpoints:
5068 warning: Breakpoint 1 address previously adjusted from 0x00010414
5072 When this warning is encountered, it may be too late to take remedial
5073 action except in cases where the breakpoint is hit earlier or more
5074 frequently than expected.
5076 @node Continuing and Stepping
5077 @section Continuing and Stepping
5081 @cindex resuming execution
5082 @dfn{Continuing} means resuming program execution until your program
5083 completes normally. In contrast, @dfn{stepping} means executing just
5084 one more ``step'' of your program, where ``step'' may mean either one
5085 line of source code, or one machine instruction (depending on what
5086 particular command you use). Either when continuing or when stepping,
5087 your program may stop even sooner, due to a breakpoint or a signal. (If
5088 it stops due to a signal, you may want to use @code{handle}, or use
5089 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5093 @kindex c @r{(@code{continue})}
5094 @kindex fg @r{(resume foreground execution)}
5095 @item continue @r{[}@var{ignore-count}@r{]}
5096 @itemx c @r{[}@var{ignore-count}@r{]}
5097 @itemx fg @r{[}@var{ignore-count}@r{]}
5098 Resume program execution, at the address where your program last stopped;
5099 any breakpoints set at that address are bypassed. The optional argument
5100 @var{ignore-count} allows you to specify a further number of times to
5101 ignore a breakpoint at this location; its effect is like that of
5102 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5104 The argument @var{ignore-count} is meaningful only when your program
5105 stopped due to a breakpoint. At other times, the argument to
5106 @code{continue} is ignored.
5108 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5109 debugged program is deemed to be the foreground program) are provided
5110 purely for convenience, and have exactly the same behavior as
5114 To resume execution at a different place, you can use @code{return}
5115 (@pxref{Returning, ,Returning from a Function}) to go back to the
5116 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5117 Different Address}) to go to an arbitrary location in your program.
5119 A typical technique for using stepping is to set a breakpoint
5120 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5121 beginning of the function or the section of your program where a problem
5122 is believed to lie, run your program until it stops at that breakpoint,
5123 and then step through the suspect area, examining the variables that are
5124 interesting, until you see the problem happen.
5128 @kindex s @r{(@code{step})}
5130 Continue running your program until control reaches a different source
5131 line, then stop it and return control to @value{GDBN}. This command is
5132 abbreviated @code{s}.
5135 @c "without debugging information" is imprecise; actually "without line
5136 @c numbers in the debugging information". (gcc -g1 has debugging info but
5137 @c not line numbers). But it seems complex to try to make that
5138 @c distinction here.
5139 @emph{Warning:} If you use the @code{step} command while control is
5140 within a function that was compiled without debugging information,
5141 execution proceeds until control reaches a function that does have
5142 debugging information. Likewise, it will not step into a function which
5143 is compiled without debugging information. To step through functions
5144 without debugging information, use the @code{stepi} command, described
5148 The @code{step} command only stops at the first instruction of a source
5149 line. This prevents the multiple stops that could otherwise occur in
5150 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5151 to stop if a function that has debugging information is called within
5152 the line. In other words, @code{step} @emph{steps inside} any functions
5153 called within the line.
5155 Also, the @code{step} command only enters a function if there is line
5156 number information for the function. Otherwise it acts like the
5157 @code{next} command. This avoids problems when using @code{cc -gl}
5158 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5159 was any debugging information about the routine.
5161 @item step @var{count}
5162 Continue running as in @code{step}, but do so @var{count} times. If a
5163 breakpoint is reached, or a signal not related to stepping occurs before
5164 @var{count} steps, stepping stops right away.
5167 @kindex n @r{(@code{next})}
5168 @item next @r{[}@var{count}@r{]}
5169 Continue to the next source line in the current (innermost) stack frame.
5170 This is similar to @code{step}, but function calls that appear within
5171 the line of code are executed without stopping. Execution stops when
5172 control reaches a different line of code at the original stack level
5173 that was executing when you gave the @code{next} command. This command
5174 is abbreviated @code{n}.
5176 An argument @var{count} is a repeat count, as for @code{step}.
5179 @c FIX ME!! Do we delete this, or is there a way it fits in with
5180 @c the following paragraph? --- Vctoria
5182 @c @code{next} within a function that lacks debugging information acts like
5183 @c @code{step}, but any function calls appearing within the code of the
5184 @c function are executed without stopping.
5186 The @code{next} command only stops at the first instruction of a
5187 source line. This prevents multiple stops that could otherwise occur in
5188 @code{switch} statements, @code{for} loops, etc.
5190 @kindex set step-mode
5192 @cindex functions without line info, and stepping
5193 @cindex stepping into functions with no line info
5194 @itemx set step-mode on
5195 The @code{set step-mode on} command causes the @code{step} command to
5196 stop at the first instruction of a function which contains no debug line
5197 information rather than stepping over it.
5199 This is useful in cases where you may be interested in inspecting the
5200 machine instructions of a function which has no symbolic info and do not
5201 want @value{GDBN} to automatically skip over this function.
5203 @item set step-mode off
5204 Causes the @code{step} command to step over any functions which contains no
5205 debug information. This is the default.
5207 @item show step-mode
5208 Show whether @value{GDBN} will stop in or step over functions without
5209 source line debug information.
5212 @kindex fin @r{(@code{finish})}
5214 Continue running until just after function in the selected stack frame
5215 returns. Print the returned value (if any). This command can be
5216 abbreviated as @code{fin}.
5218 Contrast this with the @code{return} command (@pxref{Returning,
5219 ,Returning from a Function}).
5222 @kindex u @r{(@code{until})}
5223 @cindex run until specified location
5226 Continue running until a source line past the current line, in the
5227 current stack frame, is reached. This command is used to avoid single
5228 stepping through a loop more than once. It is like the @code{next}
5229 command, except that when @code{until} encounters a jump, it
5230 automatically continues execution until the program counter is greater
5231 than the address of the jump.
5233 This means that when you reach the end of a loop after single stepping
5234 though it, @code{until} makes your program continue execution until it
5235 exits the loop. In contrast, a @code{next} command at the end of a loop
5236 simply steps back to the beginning of the loop, which forces you to step
5237 through the next iteration.
5239 @code{until} always stops your program if it attempts to exit the current
5242 @code{until} may produce somewhat counterintuitive results if the order
5243 of machine code does not match the order of the source lines. For
5244 example, in the following excerpt from a debugging session, the @code{f}
5245 (@code{frame}) command shows that execution is stopped at line
5246 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5250 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5252 (@value{GDBP}) until
5253 195 for ( ; argc > 0; NEXTARG) @{
5256 This happened because, for execution efficiency, the compiler had
5257 generated code for the loop closure test at the end, rather than the
5258 start, of the loop---even though the test in a C @code{for}-loop is
5259 written before the body of the loop. The @code{until} command appeared
5260 to step back to the beginning of the loop when it advanced to this
5261 expression; however, it has not really gone to an earlier
5262 statement---not in terms of the actual machine code.
5264 @code{until} with no argument works by means of single
5265 instruction stepping, and hence is slower than @code{until} with an
5268 @item until @var{location}
5269 @itemx u @var{location}
5270 Continue running your program until either the specified @var{location} is
5271 reached, or the current stack frame returns. The location is any of
5272 the forms described in @ref{Specify Location}.
5273 This form of the command uses temporary breakpoints, and
5274 hence is quicker than @code{until} without an argument. The specified
5275 location is actually reached only if it is in the current frame. This
5276 implies that @code{until} can be used to skip over recursive function
5277 invocations. For instance in the code below, if the current location is
5278 line @code{96}, issuing @code{until 99} will execute the program up to
5279 line @code{99} in the same invocation of factorial, i.e., after the inner
5280 invocations have returned.
5283 94 int factorial (int value)
5285 96 if (value > 1) @{
5286 97 value *= factorial (value - 1);
5293 @kindex advance @var{location}
5294 @item advance @var{location}
5295 Continue running the program up to the given @var{location}. An argument is
5296 required, which should be of one of the forms described in
5297 @ref{Specify Location}.
5298 Execution will also stop upon exit from the current stack
5299 frame. This command is similar to @code{until}, but @code{advance} will
5300 not skip over recursive function calls, and the target location doesn't
5301 have to be in the same frame as the current one.
5305 @kindex si @r{(@code{stepi})}
5307 @itemx stepi @var{arg}
5309 Execute one machine instruction, then stop and return to the debugger.
5311 It is often useful to do @samp{display/i $pc} when stepping by machine
5312 instructions. This makes @value{GDBN} automatically display the next
5313 instruction to be executed, each time your program stops. @xref{Auto
5314 Display,, Automatic Display}.
5316 An argument is a repeat count, as in @code{step}.
5320 @kindex ni @r{(@code{nexti})}
5322 @itemx nexti @var{arg}
5324 Execute one machine instruction, but if it is a function call,
5325 proceed until the function returns.
5327 An argument is a repeat count, as in @code{next}.
5331 @anchor{range stepping}
5332 @cindex range stepping
5333 @cindex target-assisted range stepping
5334 By default, and if available, @value{GDBN} makes use of
5335 target-assisted @dfn{range stepping}. In other words, whenever you
5336 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5337 tells the target to step the corresponding range of instruction
5338 addresses instead of issuing multiple single-steps. This speeds up
5339 line stepping, particularly for remote targets. Ideally, there should
5340 be no reason you would want to turn range stepping off. However, it's
5341 possible that a bug in the debug info, a bug in the remote stub (for
5342 remote targets), or even a bug in @value{GDBN} could make line
5343 stepping behave incorrectly when target-assisted range stepping is
5344 enabled. You can use the following command to turn off range stepping
5348 @kindex set range-stepping
5349 @kindex show range-stepping
5350 @item set range-stepping
5351 @itemx show range-stepping
5352 Control whether range stepping is enabled.
5354 If @code{on}, and the target supports it, @value{GDBN} tells the
5355 target to step a range of addresses itself, instead of issuing
5356 multiple single-steps. If @code{off}, @value{GDBN} always issues
5357 single-steps, even if range stepping is supported by the target. The
5358 default is @code{on}.
5362 @node Skipping Over Functions and Files
5363 @section Skipping Over Functions and Files
5364 @cindex skipping over functions and files
5366 The program you are debugging may contain some functions which are
5367 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5368 skip a function or all functions in a file when stepping.
5370 For example, consider the following C function:
5381 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5382 are not interested in stepping through @code{boring}. If you run @code{step}
5383 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5384 step over both @code{foo} and @code{boring}!
5386 One solution is to @code{step} into @code{boring} and use the @code{finish}
5387 command to immediately exit it. But this can become tedious if @code{boring}
5388 is called from many places.
5390 A more flexible solution is to execute @kbd{skip boring}. This instructs
5391 @value{GDBN} never to step into @code{boring}. Now when you execute
5392 @code{step} at line 103, you'll step over @code{boring} and directly into
5395 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5396 example, @code{skip file boring.c}.
5399 @kindex skip function
5400 @item skip @r{[}@var{linespec}@r{]}
5401 @itemx skip function @r{[}@var{linespec}@r{]}
5402 After running this command, the function named by @var{linespec} or the
5403 function containing the line named by @var{linespec} will be skipped over when
5404 stepping. @xref{Specify Location}.
5406 If you do not specify @var{linespec}, the function you're currently debugging
5409 (If you have a function called @code{file} that you want to skip, use
5410 @kbd{skip function file}.)
5413 @item skip file @r{[}@var{filename}@r{]}
5414 After running this command, any function whose source lives in @var{filename}
5415 will be skipped over when stepping.
5417 If you do not specify @var{filename}, functions whose source lives in the file
5418 you're currently debugging will be skipped.
5421 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5422 These are the commands for managing your list of skips:
5426 @item info skip @r{[}@var{range}@r{]}
5427 Print details about the specified skip(s). If @var{range} is not specified,
5428 print a table with details about all functions and files marked for skipping.
5429 @code{info skip} prints the following information about each skip:
5433 A number identifying this skip.
5435 The type of this skip, either @samp{function} or @samp{file}.
5436 @item Enabled or Disabled
5437 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5439 For function skips, this column indicates the address in memory of the function
5440 being skipped. If you've set a function skip on a function which has not yet
5441 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5442 which has the function is loaded, @code{info skip} will show the function's
5445 For file skips, this field contains the filename being skipped. For functions
5446 skips, this field contains the function name and its line number in the file
5447 where it is defined.
5451 @item skip delete @r{[}@var{range}@r{]}
5452 Delete the specified skip(s). If @var{range} is not specified, delete all
5456 @item skip enable @r{[}@var{range}@r{]}
5457 Enable the specified skip(s). If @var{range} is not specified, enable all
5460 @kindex skip disable
5461 @item skip disable @r{[}@var{range}@r{]}
5462 Disable the specified skip(s). If @var{range} is not specified, disable all
5471 A signal is an asynchronous event that can happen in a program. The
5472 operating system defines the possible kinds of signals, and gives each
5473 kind a name and a number. For example, in Unix @code{SIGINT} is the
5474 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5475 @code{SIGSEGV} is the signal a program gets from referencing a place in
5476 memory far away from all the areas in use; @code{SIGALRM} occurs when
5477 the alarm clock timer goes off (which happens only if your program has
5478 requested an alarm).
5480 @cindex fatal signals
5481 Some signals, including @code{SIGALRM}, are a normal part of the
5482 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5483 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5484 program has not specified in advance some other way to handle the signal.
5485 @code{SIGINT} does not indicate an error in your program, but it is normally
5486 fatal so it can carry out the purpose of the interrupt: to kill the program.
5488 @value{GDBN} has the ability to detect any occurrence of a signal in your
5489 program. You can tell @value{GDBN} in advance what to do for each kind of
5492 @cindex handling signals
5493 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5494 @code{SIGALRM} be silently passed to your program
5495 (so as not to interfere with their role in the program's functioning)
5496 but to stop your program immediately whenever an error signal happens.
5497 You can change these settings with the @code{handle} command.
5500 @kindex info signals
5504 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5505 handle each one. You can use this to see the signal numbers of all
5506 the defined types of signals.
5508 @item info signals @var{sig}
5509 Similar, but print information only about the specified signal number.
5511 @code{info handle} is an alias for @code{info signals}.
5513 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5514 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5515 for details about this command.
5518 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5519 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5520 can be the number of a signal or its name (with or without the
5521 @samp{SIG} at the beginning); a list of signal numbers of the form
5522 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5523 known signals. Optional arguments @var{keywords}, described below,
5524 say what change to make.
5528 The keywords allowed by the @code{handle} command can be abbreviated.
5529 Their full names are:
5533 @value{GDBN} should not stop your program when this signal happens. It may
5534 still print a message telling you that the signal has come in.
5537 @value{GDBN} should stop your program when this signal happens. This implies
5538 the @code{print} keyword as well.
5541 @value{GDBN} should print a message when this signal happens.
5544 @value{GDBN} should not mention the occurrence of the signal at all. This
5545 implies the @code{nostop} keyword as well.
5549 @value{GDBN} should allow your program to see this signal; your program
5550 can handle the signal, or else it may terminate if the signal is fatal
5551 and not handled. @code{pass} and @code{noignore} are synonyms.
5555 @value{GDBN} should not allow your program to see this signal.
5556 @code{nopass} and @code{ignore} are synonyms.
5560 When a signal stops your program, the signal is not visible to the
5562 continue. Your program sees the signal then, if @code{pass} is in
5563 effect for the signal in question @emph{at that time}. In other words,
5564 after @value{GDBN} reports a signal, you can use the @code{handle}
5565 command with @code{pass} or @code{nopass} to control whether your
5566 program sees that signal when you continue.
5568 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5569 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5570 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5573 You can also use the @code{signal} command to prevent your program from
5574 seeing a signal, or cause it to see a signal it normally would not see,
5575 or to give it any signal at any time. For example, if your program stopped
5576 due to some sort of memory reference error, you might store correct
5577 values into the erroneous variables and continue, hoping to see more
5578 execution; but your program would probably terminate immediately as
5579 a result of the fatal signal once it saw the signal. To prevent this,
5580 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5583 @cindex extra signal information
5584 @anchor{extra signal information}
5586 On some targets, @value{GDBN} can inspect extra signal information
5587 associated with the intercepted signal, before it is actually
5588 delivered to the program being debugged. This information is exported
5589 by the convenience variable @code{$_siginfo}, and consists of data
5590 that is passed by the kernel to the signal handler at the time of the
5591 receipt of a signal. The data type of the information itself is
5592 target dependent. You can see the data type using the @code{ptype
5593 $_siginfo} command. On Unix systems, it typically corresponds to the
5594 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5597 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5598 referenced address that raised a segmentation fault.
5602 (@value{GDBP}) continue
5603 Program received signal SIGSEGV, Segmentation fault.
5604 0x0000000000400766 in main ()
5606 (@value{GDBP}) ptype $_siginfo
5613 struct @{...@} _kill;
5614 struct @{...@} _timer;
5616 struct @{...@} _sigchld;
5617 struct @{...@} _sigfault;
5618 struct @{...@} _sigpoll;
5621 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5625 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5626 $1 = (void *) 0x7ffff7ff7000
5630 Depending on target support, @code{$_siginfo} may also be writable.
5633 @section Stopping and Starting Multi-thread Programs
5635 @cindex stopped threads
5636 @cindex threads, stopped
5638 @cindex continuing threads
5639 @cindex threads, continuing
5641 @value{GDBN} supports debugging programs with multiple threads
5642 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5643 are two modes of controlling execution of your program within the
5644 debugger. In the default mode, referred to as @dfn{all-stop mode},
5645 when any thread in your program stops (for example, at a breakpoint
5646 or while being stepped), all other threads in the program are also stopped by
5647 @value{GDBN}. On some targets, @value{GDBN} also supports
5648 @dfn{non-stop mode}, in which other threads can continue to run freely while
5649 you examine the stopped thread in the debugger.
5652 * All-Stop Mode:: All threads stop when GDB takes control
5653 * Non-Stop Mode:: Other threads continue to execute
5654 * Background Execution:: Running your program asynchronously
5655 * Thread-Specific Breakpoints:: Controlling breakpoints
5656 * Interrupted System Calls:: GDB may interfere with system calls
5657 * Observer Mode:: GDB does not alter program behavior
5661 @subsection All-Stop Mode
5663 @cindex all-stop mode
5665 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5666 @emph{all} threads of execution stop, not just the current thread. This
5667 allows you to examine the overall state of the program, including
5668 switching between threads, without worrying that things may change
5671 Conversely, whenever you restart the program, @emph{all} threads start
5672 executing. @emph{This is true even when single-stepping} with commands
5673 like @code{step} or @code{next}.
5675 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5676 Since thread scheduling is up to your debugging target's operating
5677 system (not controlled by @value{GDBN}), other threads may
5678 execute more than one statement while the current thread completes a
5679 single step. Moreover, in general other threads stop in the middle of a
5680 statement, rather than at a clean statement boundary, when the program
5683 You might even find your program stopped in another thread after
5684 continuing or even single-stepping. This happens whenever some other
5685 thread runs into a breakpoint, a signal, or an exception before the
5686 first thread completes whatever you requested.
5688 @cindex automatic thread selection
5689 @cindex switching threads automatically
5690 @cindex threads, automatic switching
5691 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5692 signal, it automatically selects the thread where that breakpoint or
5693 signal happened. @value{GDBN} alerts you to the context switch with a
5694 message such as @samp{[Switching to Thread @var{n}]} to identify the
5697 On some OSes, you can modify @value{GDBN}'s default behavior by
5698 locking the OS scheduler to allow only a single thread to run.
5701 @item set scheduler-locking @var{mode}
5702 @cindex scheduler locking mode
5703 @cindex lock scheduler
5704 Set the scheduler locking mode. If it is @code{off}, then there is no
5705 locking and any thread may run at any time. If @code{on}, then only the
5706 current thread may run when the inferior is resumed. The @code{step}
5707 mode optimizes for single-stepping; it prevents other threads
5708 from preempting the current thread while you are stepping, so that
5709 the focus of debugging does not change unexpectedly.
5710 Other threads only rarely (or never) get a chance to run
5711 when you step. They are more likely to run when you @samp{next} over a
5712 function call, and they are completely free to run when you use commands
5713 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5714 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5715 the current thread away from the thread that you are debugging.
5717 @item show scheduler-locking
5718 Display the current scheduler locking mode.
5721 @cindex resume threads of multiple processes simultaneously
5722 By default, when you issue one of the execution commands such as
5723 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5724 threads of the current inferior to run. For example, if @value{GDBN}
5725 is attached to two inferiors, each with two threads, the
5726 @code{continue} command resumes only the two threads of the current
5727 inferior. This is useful, for example, when you debug a program that
5728 forks and you want to hold the parent stopped (so that, for instance,
5729 it doesn't run to exit), while you debug the child. In other
5730 situations, you may not be interested in inspecting the current state
5731 of any of the processes @value{GDBN} is attached to, and you may want
5732 to resume them all until some breakpoint is hit. In the latter case,
5733 you can instruct @value{GDBN} to allow all threads of all the
5734 inferiors to run with the @w{@code{set schedule-multiple}} command.
5737 @kindex set schedule-multiple
5738 @item set schedule-multiple
5739 Set the mode for allowing threads of multiple processes to be resumed
5740 when an execution command is issued. When @code{on}, all threads of
5741 all processes are allowed to run. When @code{off}, only the threads
5742 of the current process are resumed. The default is @code{off}. The
5743 @code{scheduler-locking} mode takes precedence when set to @code{on},
5744 or while you are stepping and set to @code{step}.
5746 @item show schedule-multiple
5747 Display the current mode for resuming the execution of threads of
5752 @subsection Non-Stop Mode
5754 @cindex non-stop mode
5756 @c This section is really only a place-holder, and needs to be expanded
5757 @c with more details.
5759 For some multi-threaded targets, @value{GDBN} supports an optional
5760 mode of operation in which you can examine stopped program threads in
5761 the debugger while other threads continue to execute freely. This
5762 minimizes intrusion when debugging live systems, such as programs
5763 where some threads have real-time constraints or must continue to
5764 respond to external events. This is referred to as @dfn{non-stop} mode.
5766 In non-stop mode, when a thread stops to report a debugging event,
5767 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5768 threads as well, in contrast to the all-stop mode behavior. Additionally,
5769 execution commands such as @code{continue} and @code{step} apply by default
5770 only to the current thread in non-stop mode, rather than all threads as
5771 in all-stop mode. This allows you to control threads explicitly in
5772 ways that are not possible in all-stop mode --- for example, stepping
5773 one thread while allowing others to run freely, stepping
5774 one thread while holding all others stopped, or stepping several threads
5775 independently and simultaneously.
5777 To enter non-stop mode, use this sequence of commands before you run
5778 or attach to your program:
5781 # If using the CLI, pagination breaks non-stop.
5784 # Finally, turn it on!
5788 You can use these commands to manipulate the non-stop mode setting:
5791 @kindex set non-stop
5792 @item set non-stop on
5793 Enable selection of non-stop mode.
5794 @item set non-stop off
5795 Disable selection of non-stop mode.
5796 @kindex show non-stop
5798 Show the current non-stop enablement setting.
5801 Note these commands only reflect whether non-stop mode is enabled,
5802 not whether the currently-executing program is being run in non-stop mode.
5803 In particular, the @code{set non-stop} preference is only consulted when
5804 @value{GDBN} starts or connects to the target program, and it is generally
5805 not possible to switch modes once debugging has started. Furthermore,
5806 since not all targets support non-stop mode, even when you have enabled
5807 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5810 In non-stop mode, all execution commands apply only to the current thread
5811 by default. That is, @code{continue} only continues one thread.
5812 To continue all threads, issue @code{continue -a} or @code{c -a}.
5814 You can use @value{GDBN}'s background execution commands
5815 (@pxref{Background Execution}) to run some threads in the background
5816 while you continue to examine or step others from @value{GDBN}.
5817 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5818 always executed asynchronously in non-stop mode.
5820 Suspending execution is done with the @code{interrupt} command when
5821 running in the background, or @kbd{Ctrl-c} during foreground execution.
5822 In all-stop mode, this stops the whole process;
5823 but in non-stop mode the interrupt applies only to the current thread.
5824 To stop the whole program, use @code{interrupt -a}.
5826 Other execution commands do not currently support the @code{-a} option.
5828 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5829 that thread current, as it does in all-stop mode. This is because the
5830 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5831 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5832 changed to a different thread just as you entered a command to operate on the
5833 previously current thread.
5835 @node Background Execution
5836 @subsection Background Execution
5838 @cindex foreground execution
5839 @cindex background execution
5840 @cindex asynchronous execution
5841 @cindex execution, foreground, background and asynchronous
5843 @value{GDBN}'s execution commands have two variants: the normal
5844 foreground (synchronous) behavior, and a background
5845 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5846 the program to report that some thread has stopped before prompting for
5847 another command. In background execution, @value{GDBN} immediately gives
5848 a command prompt so that you can issue other commands while your program runs.
5850 If the target doesn't support async mode, @value{GDBN} issues an error
5851 message if you attempt to use the background execution commands.
5853 To specify background execution, add a @code{&} to the command. For example,
5854 the background form of the @code{continue} command is @code{continue&}, or
5855 just @code{c&}. The execution commands that accept background execution
5861 @xref{Starting, , Starting your Program}.
5865 @xref{Attach, , Debugging an Already-running Process}.
5869 @xref{Continuing and Stepping, step}.
5873 @xref{Continuing and Stepping, stepi}.
5877 @xref{Continuing and Stepping, next}.
5881 @xref{Continuing and Stepping, nexti}.
5885 @xref{Continuing and Stepping, continue}.
5889 @xref{Continuing and Stepping, finish}.
5893 @xref{Continuing and Stepping, until}.
5897 Background execution is especially useful in conjunction with non-stop
5898 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5899 However, you can also use these commands in the normal all-stop mode with
5900 the restriction that you cannot issue another execution command until the
5901 previous one finishes. Examples of commands that are valid in all-stop
5902 mode while the program is running include @code{help} and @code{info break}.
5904 You can interrupt your program while it is running in the background by
5905 using the @code{interrupt} command.
5912 Suspend execution of the running program. In all-stop mode,
5913 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5914 only the current thread. To stop the whole program in non-stop mode,
5915 use @code{interrupt -a}.
5918 @node Thread-Specific Breakpoints
5919 @subsection Thread-Specific Breakpoints
5921 When your program has multiple threads (@pxref{Threads,, Debugging
5922 Programs with Multiple Threads}), you can choose whether to set
5923 breakpoints on all threads, or on a particular thread.
5926 @cindex breakpoints and threads
5927 @cindex thread breakpoints
5928 @kindex break @dots{} thread @var{threadno}
5929 @item break @var{linespec} thread @var{threadno}
5930 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5931 @var{linespec} specifies source lines; there are several ways of
5932 writing them (@pxref{Specify Location}), but the effect is always to
5933 specify some source line.
5935 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5936 to specify that you only want @value{GDBN} to stop the program when a
5937 particular thread reaches this breakpoint. The @var{threadno} specifier
5938 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
5939 in the first column of the @samp{info threads} display.
5941 If you do not specify @samp{thread @var{threadno}} when you set a
5942 breakpoint, the breakpoint applies to @emph{all} threads of your
5945 You can use the @code{thread} qualifier on conditional breakpoints as
5946 well; in this case, place @samp{thread @var{threadno}} before or
5947 after the breakpoint condition, like this:
5950 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5955 Thread-specific breakpoints are automatically deleted when
5956 @value{GDBN} detects the corresponding thread is no longer in the
5957 thread list. For example:
5961 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5964 There are several ways for a thread to disappear, such as a regular
5965 thread exit, but also when you detach from the process with the
5966 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5967 Process}), or if @value{GDBN} loses the remote connection
5968 (@pxref{Remote Debugging}), etc. Note that with some targets,
5969 @value{GDBN} is only able to detect a thread has exited when the user
5970 explictly asks for the thread list with the @code{info threads}
5973 @node Interrupted System Calls
5974 @subsection Interrupted System Calls
5976 @cindex thread breakpoints and system calls
5977 @cindex system calls and thread breakpoints
5978 @cindex premature return from system calls
5979 There is an unfortunate side effect when using @value{GDBN} to debug
5980 multi-threaded programs. If one thread stops for a
5981 breakpoint, or for some other reason, and another thread is blocked in a
5982 system call, then the system call may return prematurely. This is a
5983 consequence of the interaction between multiple threads and the signals
5984 that @value{GDBN} uses to implement breakpoints and other events that
5987 To handle this problem, your program should check the return value of
5988 each system call and react appropriately. This is good programming
5991 For example, do not write code like this:
5997 The call to @code{sleep} will return early if a different thread stops
5998 at a breakpoint or for some other reason.
6000 Instead, write this:
6005 unslept = sleep (unslept);
6008 A system call is allowed to return early, so the system is still
6009 conforming to its specification. But @value{GDBN} does cause your
6010 multi-threaded program to behave differently than it would without
6013 Also, @value{GDBN} uses internal breakpoints in the thread library to
6014 monitor certain events such as thread creation and thread destruction.
6015 When such an event happens, a system call in another thread may return
6016 prematurely, even though your program does not appear to stop.
6019 @subsection Observer Mode
6021 If you want to build on non-stop mode and observe program behavior
6022 without any chance of disruption by @value{GDBN}, you can set
6023 variables to disable all of the debugger's attempts to modify state,
6024 whether by writing memory, inserting breakpoints, etc. These operate
6025 at a low level, intercepting operations from all commands.
6027 When all of these are set to @code{off}, then @value{GDBN} is said to
6028 be @dfn{observer mode}. As a convenience, the variable
6029 @code{observer} can be set to disable these, plus enable non-stop
6032 Note that @value{GDBN} will not prevent you from making nonsensical
6033 combinations of these settings. For instance, if you have enabled
6034 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6035 then breakpoints that work by writing trap instructions into the code
6036 stream will still not be able to be placed.
6041 @item set observer on
6042 @itemx set observer off
6043 When set to @code{on}, this disables all the permission variables
6044 below (except for @code{insert-fast-tracepoints}), plus enables
6045 non-stop debugging. Setting this to @code{off} switches back to
6046 normal debugging, though remaining in non-stop mode.
6049 Show whether observer mode is on or off.
6051 @kindex may-write-registers
6052 @item set may-write-registers on
6053 @itemx set may-write-registers off
6054 This controls whether @value{GDBN} will attempt to alter the values of
6055 registers, such as with assignment expressions in @code{print}, or the
6056 @code{jump} command. It defaults to @code{on}.
6058 @item show may-write-registers
6059 Show the current permission to write registers.
6061 @kindex may-write-memory
6062 @item set may-write-memory on
6063 @itemx set may-write-memory off
6064 This controls whether @value{GDBN} will attempt to alter the contents
6065 of memory, such as with assignment expressions in @code{print}. It
6066 defaults to @code{on}.
6068 @item show may-write-memory
6069 Show the current permission to write memory.
6071 @kindex may-insert-breakpoints
6072 @item set may-insert-breakpoints on
6073 @itemx set may-insert-breakpoints off
6074 This controls whether @value{GDBN} will attempt to insert breakpoints.
6075 This affects all breakpoints, including internal breakpoints defined
6076 by @value{GDBN}. It defaults to @code{on}.
6078 @item show may-insert-breakpoints
6079 Show the current permission to insert breakpoints.
6081 @kindex may-insert-tracepoints
6082 @item set may-insert-tracepoints on
6083 @itemx set may-insert-tracepoints off
6084 This controls whether @value{GDBN} will attempt to insert (regular)
6085 tracepoints at the beginning of a tracing experiment. It affects only
6086 non-fast tracepoints, fast tracepoints being under the control of
6087 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6089 @item show may-insert-tracepoints
6090 Show the current permission to insert tracepoints.
6092 @kindex may-insert-fast-tracepoints
6093 @item set may-insert-fast-tracepoints on
6094 @itemx set may-insert-fast-tracepoints off
6095 This controls whether @value{GDBN} will attempt to insert fast
6096 tracepoints at the beginning of a tracing experiment. It affects only
6097 fast tracepoints, regular (non-fast) tracepoints being under the
6098 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6100 @item show may-insert-fast-tracepoints
6101 Show the current permission to insert fast tracepoints.
6103 @kindex may-interrupt
6104 @item set may-interrupt on
6105 @itemx set may-interrupt off
6106 This controls whether @value{GDBN} will attempt to interrupt or stop
6107 program execution. When this variable is @code{off}, the
6108 @code{interrupt} command will have no effect, nor will
6109 @kbd{Ctrl-c}. It defaults to @code{on}.
6111 @item show may-interrupt
6112 Show the current permission to interrupt or stop the program.
6116 @node Reverse Execution
6117 @chapter Running programs backward
6118 @cindex reverse execution
6119 @cindex running programs backward
6121 When you are debugging a program, it is not unusual to realize that
6122 you have gone too far, and some event of interest has already happened.
6123 If the target environment supports it, @value{GDBN} can allow you to
6124 ``rewind'' the program by running it backward.
6126 A target environment that supports reverse execution should be able
6127 to ``undo'' the changes in machine state that have taken place as the
6128 program was executing normally. Variables, registers etc.@: should
6129 revert to their previous values. Obviously this requires a great
6130 deal of sophistication on the part of the target environment; not
6131 all target environments can support reverse execution.
6133 When a program is executed in reverse, the instructions that
6134 have most recently been executed are ``un-executed'', in reverse
6135 order. The program counter runs backward, following the previous
6136 thread of execution in reverse. As each instruction is ``un-executed'',
6137 the values of memory and/or registers that were changed by that
6138 instruction are reverted to their previous states. After executing
6139 a piece of source code in reverse, all side effects of that code
6140 should be ``undone'', and all variables should be returned to their
6141 prior values@footnote{
6142 Note that some side effects are easier to undo than others. For instance,
6143 memory and registers are relatively easy, but device I/O is hard. Some
6144 targets may be able undo things like device I/O, and some may not.
6146 The contract between @value{GDBN} and the reverse executing target
6147 requires only that the target do something reasonable when
6148 @value{GDBN} tells it to execute backwards, and then report the
6149 results back to @value{GDBN}. Whatever the target reports back to
6150 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6151 assumes that the memory and registers that the target reports are in a
6152 consistant state, but @value{GDBN} accepts whatever it is given.
6155 If you are debugging in a target environment that supports
6156 reverse execution, @value{GDBN} provides the following commands.
6159 @kindex reverse-continue
6160 @kindex rc @r{(@code{reverse-continue})}
6161 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6162 @itemx rc @r{[}@var{ignore-count}@r{]}
6163 Beginning at the point where your program last stopped, start executing
6164 in reverse. Reverse execution will stop for breakpoints and synchronous
6165 exceptions (signals), just like normal execution. Behavior of
6166 asynchronous signals depends on the target environment.
6168 @kindex reverse-step
6169 @kindex rs @r{(@code{step})}
6170 @item reverse-step @r{[}@var{count}@r{]}
6171 Run the program backward until control reaches the start of a
6172 different source line; then stop it, and return control to @value{GDBN}.
6174 Like the @code{step} command, @code{reverse-step} will only stop
6175 at the beginning of a source line. It ``un-executes'' the previously
6176 executed source line. If the previous source line included calls to
6177 debuggable functions, @code{reverse-step} will step (backward) into
6178 the called function, stopping at the beginning of the @emph{last}
6179 statement in the called function (typically a return statement).
6181 Also, as with the @code{step} command, if non-debuggable functions are
6182 called, @code{reverse-step} will run thru them backward without stopping.
6184 @kindex reverse-stepi
6185 @kindex rsi @r{(@code{reverse-stepi})}
6186 @item reverse-stepi @r{[}@var{count}@r{]}
6187 Reverse-execute one machine instruction. Note that the instruction
6188 to be reverse-executed is @emph{not} the one pointed to by the program
6189 counter, but the instruction executed prior to that one. For instance,
6190 if the last instruction was a jump, @code{reverse-stepi} will take you
6191 back from the destination of the jump to the jump instruction itself.
6193 @kindex reverse-next
6194 @kindex rn @r{(@code{reverse-next})}
6195 @item reverse-next @r{[}@var{count}@r{]}
6196 Run backward to the beginning of the previous line executed in
6197 the current (innermost) stack frame. If the line contains function
6198 calls, they will be ``un-executed'' without stopping. Starting from
6199 the first line of a function, @code{reverse-next} will take you back
6200 to the caller of that function, @emph{before} the function was called,
6201 just as the normal @code{next} command would take you from the last
6202 line of a function back to its return to its caller
6203 @footnote{Unless the code is too heavily optimized.}.
6205 @kindex reverse-nexti
6206 @kindex rni @r{(@code{reverse-nexti})}
6207 @item reverse-nexti @r{[}@var{count}@r{]}
6208 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6209 in reverse, except that called functions are ``un-executed'' atomically.
6210 That is, if the previously executed instruction was a return from
6211 another function, @code{reverse-nexti} will continue to execute
6212 in reverse until the call to that function (from the current stack
6215 @kindex reverse-finish
6216 @item reverse-finish
6217 Just as the @code{finish} command takes you to the point where the
6218 current function returns, @code{reverse-finish} takes you to the point
6219 where it was called. Instead of ending up at the end of the current
6220 function invocation, you end up at the beginning.
6222 @kindex set exec-direction
6223 @item set exec-direction
6224 Set the direction of target execution.
6225 @item set exec-direction reverse
6226 @cindex execute forward or backward in time
6227 @value{GDBN} will perform all execution commands in reverse, until the
6228 exec-direction mode is changed to ``forward''. Affected commands include
6229 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6230 command cannot be used in reverse mode.
6231 @item set exec-direction forward
6232 @value{GDBN} will perform all execution commands in the normal fashion.
6233 This is the default.
6237 @node Process Record and Replay
6238 @chapter Recording Inferior's Execution and Replaying It
6239 @cindex process record and replay
6240 @cindex recording inferior's execution and replaying it
6242 On some platforms, @value{GDBN} provides a special @dfn{process record
6243 and replay} target that can record a log of the process execution, and
6244 replay it later with both forward and reverse execution commands.
6247 When this target is in use, if the execution log includes the record
6248 for the next instruction, @value{GDBN} will debug in @dfn{replay
6249 mode}. In the replay mode, the inferior does not really execute code
6250 instructions. Instead, all the events that normally happen during
6251 code execution are taken from the execution log. While code is not
6252 really executed in replay mode, the values of registers (including the
6253 program counter register) and the memory of the inferior are still
6254 changed as they normally would. Their contents are taken from the
6258 If the record for the next instruction is not in the execution log,
6259 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6260 inferior executes normally, and @value{GDBN} records the execution log
6263 The process record and replay target supports reverse execution
6264 (@pxref{Reverse Execution}), even if the platform on which the
6265 inferior runs does not. However, the reverse execution is limited in
6266 this case by the range of the instructions recorded in the execution
6267 log. In other words, reverse execution on platforms that don't
6268 support it directly can only be done in the replay mode.
6270 When debugging in the reverse direction, @value{GDBN} will work in
6271 replay mode as long as the execution log includes the record for the
6272 previous instruction; otherwise, it will work in record mode, if the
6273 platform supports reverse execution, or stop if not.
6275 For architecture environments that support process record and replay,
6276 @value{GDBN} provides the following commands:
6279 @kindex target record
6280 @kindex target record-full
6281 @kindex target record-btrace
6284 @kindex record btrace
6288 @item record @var{method}
6289 This command starts the process record and replay target. The
6290 recording method can be specified as parameter. Without a parameter
6291 the command uses the @code{full} recording method. The following
6292 recording methods are available:
6296 Full record/replay recording using @value{GDBN}'s software record and
6297 replay implementation. This method allows replaying and reverse
6301 Hardware-supported instruction recording. This method does not record
6302 data. Further, the data is collected in a ring buffer so old data will
6303 be overwritten when the buffer is full. It allows limited replay and
6306 This recording method may not be available on all processors.
6309 The process record and replay target can only debug a process that is
6310 already running. Therefore, you need first to start the process with
6311 the @kbd{run} or @kbd{start} commands, and then start the recording
6312 with the @kbd{record @var{method}} command.
6314 Both @code{record @var{method}} and @code{rec @var{method}} are
6315 aliases of @code{target record-@var{method}}.
6317 @cindex displaced stepping, and process record and replay
6318 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6319 will be automatically disabled when process record and replay target
6320 is started. That's because the process record and replay target
6321 doesn't support displaced stepping.
6323 @cindex non-stop mode, and process record and replay
6324 @cindex asynchronous execution, and process record and replay
6325 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6326 the asynchronous execution mode (@pxref{Background Execution}), not
6327 all recording methods are available. The @code{full} recording method
6328 does not support these two modes.
6333 Stop the process record and replay target. When process record and
6334 replay target stops, the entire execution log will be deleted and the
6335 inferior will either be terminated, or will remain in its final state.
6337 When you stop the process record and replay target in record mode (at
6338 the end of the execution log), the inferior will be stopped at the
6339 next instruction that would have been recorded. In other words, if
6340 you record for a while and then stop recording, the inferior process
6341 will be left in the same state as if the recording never happened.
6343 On the other hand, if the process record and replay target is stopped
6344 while in replay mode (that is, not at the end of the execution log,
6345 but at some earlier point), the inferior process will become ``live''
6346 at that earlier state, and it will then be possible to continue the
6347 usual ``live'' debugging of the process from that state.
6349 When the inferior process exits, or @value{GDBN} detaches from it,
6350 process record and replay target will automatically stop itself.
6354 Go to a specific location in the execution log. There are several
6355 ways to specify the location to go to:
6358 @item record goto begin
6359 @itemx record goto start
6360 Go to the beginning of the execution log.
6362 @item record goto end
6363 Go to the end of the execution log.
6365 @item record goto @var{n}
6366 Go to instruction number @var{n} in the execution log.
6370 @item record save @var{filename}
6371 Save the execution log to a file @file{@var{filename}}.
6372 Default filename is @file{gdb_record.@var{process_id}}, where
6373 @var{process_id} is the process ID of the inferior.
6375 This command may not be available for all recording methods.
6377 @kindex record restore
6378 @item record restore @var{filename}
6379 Restore the execution log from a file @file{@var{filename}}.
6380 File must have been created with @code{record save}.
6382 @kindex set record full
6383 @item set record full insn-number-max @var{limit}
6384 @itemx set record full insn-number-max unlimited
6385 Set the limit of instructions to be recorded for the @code{full}
6386 recording method. Default value is 200000.
6388 If @var{limit} is a positive number, then @value{GDBN} will start
6389 deleting instructions from the log once the number of the record
6390 instructions becomes greater than @var{limit}. For every new recorded
6391 instruction, @value{GDBN} will delete the earliest recorded
6392 instruction to keep the number of recorded instructions at the limit.
6393 (Since deleting recorded instructions loses information, @value{GDBN}
6394 lets you control what happens when the limit is reached, by means of
6395 the @code{stop-at-limit} option, described below.)
6397 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6398 delete recorded instructions from the execution log. The number of
6399 recorded instructions is limited only by the available memory.
6401 @kindex show record full
6402 @item show record full insn-number-max
6403 Show the limit of instructions to be recorded with the @code{full}
6406 @item set record full stop-at-limit
6407 Control the behavior of the @code{full} recording method when the
6408 number of recorded instructions reaches the limit. If ON (the
6409 default), @value{GDBN} will stop when the limit is reached for the
6410 first time and ask you whether you want to stop the inferior or
6411 continue running it and recording the execution log. If you decide
6412 to continue recording, each new recorded instruction will cause the
6413 oldest one to be deleted.
6415 If this option is OFF, @value{GDBN} will automatically delete the
6416 oldest record to make room for each new one, without asking.
6418 @item show record full stop-at-limit
6419 Show the current setting of @code{stop-at-limit}.
6421 @item set record full memory-query
6422 Control the behavior when @value{GDBN} is unable to record memory
6423 changes caused by an instruction for the @code{full} recording method.
6424 If ON, @value{GDBN} will query whether to stop the inferior in that
6427 If this option is OFF (the default), @value{GDBN} will automatically
6428 ignore the effect of such instructions on memory. Later, when
6429 @value{GDBN} replays this execution log, it will mark the log of this
6430 instruction as not accessible, and it will not affect the replay
6433 @item show record full memory-query
6434 Show the current setting of @code{memory-query}.
6436 @kindex set record btrace
6437 The @code{btrace} record target does not trace data. As a
6438 convenience, when replaying, @value{GDBN} reads read-only memory off
6439 the live program directly, assuming that the addresses of the
6440 read-only areas don't change. This for example makes it possible to
6441 disassemble code while replaying, but not to print variables.
6442 In some cases, being able to inspect variables might be useful.
6443 You can use the following command for that:
6445 @item set record btrace replay-memory-access
6446 Control the behavior of the @code{btrace} recording method when
6447 accessing memory during replay. If @code{read-only} (the default),
6448 @value{GDBN} will only allow accesses to read-only memory.
6449 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6450 and to read-write memory. Beware that the accessed memory corresponds
6451 to the live target and not necessarily to the current replay
6454 @kindex show record btrace
6455 @item show record btrace replay-memory-access
6456 Show the current setting of @code{replay-memory-access}.
6460 Show various statistics about the recording depending on the recording
6465 For the @code{full} recording method, it shows the state of process
6466 record and its in-memory execution log buffer, including:
6470 Whether in record mode or replay mode.
6472 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6474 Highest recorded instruction number.
6476 Current instruction about to be replayed (if in replay mode).
6478 Number of instructions contained in the execution log.
6480 Maximum number of instructions that may be contained in the execution log.
6484 For the @code{btrace} recording method, it shows the number of
6485 instructions that have been recorded and the number of blocks of
6486 sequential control-flow that is formed by the recorded instructions.
6489 @kindex record delete
6492 When record target runs in replay mode (``in the past''), delete the
6493 subsequent execution log and begin to record a new execution log starting
6494 from the current address. This means you will abandon the previously
6495 recorded ``future'' and begin recording a new ``future''.
6497 @kindex record instruction-history
6498 @kindex rec instruction-history
6499 @item record instruction-history
6500 Disassembles instructions from the recorded execution log. By
6501 default, ten instructions are disassembled. This can be changed using
6502 the @code{set record instruction-history-size} command. Instructions
6503 are printed in execution order. There are several ways to specify
6504 what part of the execution log to disassemble:
6507 @item record instruction-history @var{insn}
6508 Disassembles ten instructions starting from instruction number
6511 @item record instruction-history @var{insn}, +/-@var{n}
6512 Disassembles @var{n} instructions around instruction number
6513 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6514 @var{n} instructions after instruction number @var{insn}. If
6515 @var{n} is preceded with @code{-}, disassembles @var{n}
6516 instructions before instruction number @var{insn}.
6518 @item record instruction-history
6519 Disassembles ten more instructions after the last disassembly.
6521 @item record instruction-history -
6522 Disassembles ten more instructions before the last disassembly.
6524 @item record instruction-history @var{begin} @var{end}
6525 Disassembles instructions beginning with instruction number
6526 @var{begin} until instruction number @var{end}. The instruction
6527 number @var{end} is included.
6530 This command may not be available for all recording methods.
6533 @item set record instruction-history-size @var{size}
6534 @itemx set record instruction-history-size unlimited
6535 Define how many instructions to disassemble in the @code{record
6536 instruction-history} command. The default value is 10.
6537 A @var{size} of @code{unlimited} means unlimited instructions.
6540 @item show record instruction-history-size
6541 Show how many instructions to disassemble in the @code{record
6542 instruction-history} command.
6544 @kindex record function-call-history
6545 @kindex rec function-call-history
6546 @item record function-call-history
6547 Prints the execution history at function granularity. It prints one
6548 line for each sequence of instructions that belong to the same
6549 function giving the name of that function, the source lines
6550 for this instruction sequence (if the @code{/l} modifier is
6551 specified), and the instructions numbers that form the sequence (if
6552 the @code{/i} modifier is specified). The function names are indented
6553 to reflect the call stack depth if the @code{/c} modifier is
6554 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6558 (@value{GDBP}) @b{list 1, 10}
6569 (@value{GDBP}) @b{record function-call-history /ilc}
6570 1 bar inst 1,4 at foo.c:6,8
6571 2 foo inst 5,10 at foo.c:2,3
6572 3 bar inst 11,13 at foo.c:9,10
6575 By default, ten lines are printed. This can be changed using the
6576 @code{set record function-call-history-size} command. Functions are
6577 printed in execution order. There are several ways to specify what
6581 @item record function-call-history @var{func}
6582 Prints ten functions starting from function number @var{func}.
6584 @item record function-call-history @var{func}, +/-@var{n}
6585 Prints @var{n} functions around function number @var{func}. If
6586 @var{n} is preceded with @code{+}, prints @var{n} functions after
6587 function number @var{func}. If @var{n} is preceded with @code{-},
6588 prints @var{n} functions before function number @var{func}.
6590 @item record function-call-history
6591 Prints ten more functions after the last ten-line print.
6593 @item record function-call-history -
6594 Prints ten more functions before the last ten-line print.
6596 @item record function-call-history @var{begin} @var{end}
6597 Prints functions beginning with function number @var{begin} until
6598 function number @var{end}. The function number @var{end} is included.
6601 This command may not be available for all recording methods.
6603 @item set record function-call-history-size @var{size}
6604 @itemx set record function-call-history-size unlimited
6605 Define how many lines to print in the
6606 @code{record function-call-history} command. The default value is 10.
6607 A size of @code{unlimited} means unlimited lines.
6609 @item show record function-call-history-size
6610 Show how many lines to print in the
6611 @code{record function-call-history} command.
6616 @chapter Examining the Stack
6618 When your program has stopped, the first thing you need to know is where it
6619 stopped and how it got there.
6622 Each time your program performs a function call, information about the call
6624 That information includes the location of the call in your program,
6625 the arguments of the call,
6626 and the local variables of the function being called.
6627 The information is saved in a block of data called a @dfn{stack frame}.
6628 The stack frames are allocated in a region of memory called the @dfn{call
6631 When your program stops, the @value{GDBN} commands for examining the
6632 stack allow you to see all of this information.
6634 @cindex selected frame
6635 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6636 @value{GDBN} commands refer implicitly to the selected frame. In
6637 particular, whenever you ask @value{GDBN} for the value of a variable in
6638 your program, the value is found in the selected frame. There are
6639 special @value{GDBN} commands to select whichever frame you are
6640 interested in. @xref{Selection, ,Selecting a Frame}.
6642 When your program stops, @value{GDBN} automatically selects the
6643 currently executing frame and describes it briefly, similar to the
6644 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6647 * Frames:: Stack frames
6648 * Backtrace:: Backtraces
6649 * Frame Filter Management:: Managing frame filters
6650 * Selection:: Selecting a frame
6651 * Frame Info:: Information on a frame
6656 @section Stack Frames
6658 @cindex frame, definition
6660 The call stack is divided up into contiguous pieces called @dfn{stack
6661 frames}, or @dfn{frames} for short; each frame is the data associated
6662 with one call to one function. The frame contains the arguments given
6663 to the function, the function's local variables, and the address at
6664 which the function is executing.
6666 @cindex initial frame
6667 @cindex outermost frame
6668 @cindex innermost frame
6669 When your program is started, the stack has only one frame, that of the
6670 function @code{main}. This is called the @dfn{initial} frame or the
6671 @dfn{outermost} frame. Each time a function is called, a new frame is
6672 made. Each time a function returns, the frame for that function invocation
6673 is eliminated. If a function is recursive, there can be many frames for
6674 the same function. The frame for the function in which execution is
6675 actually occurring is called the @dfn{innermost} frame. This is the most
6676 recently created of all the stack frames that still exist.
6678 @cindex frame pointer
6679 Inside your program, stack frames are identified by their addresses. A
6680 stack frame consists of many bytes, each of which has its own address; each
6681 kind of computer has a convention for choosing one byte whose
6682 address serves as the address of the frame. Usually this address is kept
6683 in a register called the @dfn{frame pointer register}
6684 (@pxref{Registers, $fp}) while execution is going on in that frame.
6686 @cindex frame number
6687 @value{GDBN} assigns numbers to all existing stack frames, starting with
6688 zero for the innermost frame, one for the frame that called it,
6689 and so on upward. These numbers do not really exist in your program;
6690 they are assigned by @value{GDBN} to give you a way of designating stack
6691 frames in @value{GDBN} commands.
6693 @c The -fomit-frame-pointer below perennially causes hbox overflow
6694 @c underflow problems.
6695 @cindex frameless execution
6696 Some compilers provide a way to compile functions so that they operate
6697 without stack frames. (For example, the @value{NGCC} option
6699 @samp{-fomit-frame-pointer}
6701 generates functions without a frame.)
6702 This is occasionally done with heavily used library functions to save
6703 the frame setup time. @value{GDBN} has limited facilities for dealing
6704 with these function invocations. If the innermost function invocation
6705 has no stack frame, @value{GDBN} nevertheless regards it as though
6706 it had a separate frame, which is numbered zero as usual, allowing
6707 correct tracing of the function call chain. However, @value{GDBN} has
6708 no provision for frameless functions elsewhere in the stack.
6711 @kindex frame@r{, command}
6712 @cindex current stack frame
6713 @item frame @r{[}@var{framespec}@r{]}
6714 The @code{frame} command allows you to move from one stack frame to another,
6715 and to print the stack frame you select. The @var{framespec} may be either the
6716 address of the frame or the stack frame number. Without an argument,
6717 @code{frame} prints the current stack frame.
6719 @kindex select-frame
6720 @cindex selecting frame silently
6722 The @code{select-frame} command allows you to move from one stack frame
6723 to another without printing the frame. This is the silent version of
6731 @cindex call stack traces
6732 A backtrace is a summary of how your program got where it is. It shows one
6733 line per frame, for many frames, starting with the currently executing
6734 frame (frame zero), followed by its caller (frame one), and on up the
6737 @anchor{backtrace-command}
6740 @kindex bt @r{(@code{backtrace})}
6743 Print a backtrace of the entire stack: one line per frame for all
6744 frames in the stack.
6746 You can stop the backtrace at any time by typing the system interrupt
6747 character, normally @kbd{Ctrl-c}.
6749 @item backtrace @var{n}
6751 Similar, but print only the innermost @var{n} frames.
6753 @item backtrace -@var{n}
6755 Similar, but print only the outermost @var{n} frames.
6757 @item backtrace full
6759 @itemx bt full @var{n}
6760 @itemx bt full -@var{n}
6761 Print the values of the local variables also. As described above,
6762 @var{n} specifies the number of frames to print.
6764 @item backtrace no-filters
6765 @itemx bt no-filters
6766 @itemx bt no-filters @var{n}
6767 @itemx bt no-filters -@var{n}
6768 @itemx bt no-filters full
6769 @itemx bt no-filters full @var{n}
6770 @itemx bt no-filters full -@var{n}
6771 Do not run Python frame filters on this backtrace. @xref{Frame
6772 Filter API}, for more information. Additionally use @ref{disable
6773 frame-filter all} to turn off all frame filters. This is only
6774 relevant when @value{GDBN} has been configured with @code{Python}
6780 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6781 are additional aliases for @code{backtrace}.
6783 @cindex multiple threads, backtrace
6784 In a multi-threaded program, @value{GDBN} by default shows the
6785 backtrace only for the current thread. To display the backtrace for
6786 several or all of the threads, use the command @code{thread apply}
6787 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6788 apply all backtrace}, @value{GDBN} will display the backtrace for all
6789 the threads; this is handy when you debug a core dump of a
6790 multi-threaded program.
6792 Each line in the backtrace shows the frame number and the function name.
6793 The program counter value is also shown---unless you use @code{set
6794 print address off}. The backtrace also shows the source file name and
6795 line number, as well as the arguments to the function. The program
6796 counter value is omitted if it is at the beginning of the code for that
6799 Here is an example of a backtrace. It was made with the command
6800 @samp{bt 3}, so it shows the innermost three frames.
6804 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6806 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6807 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6809 (More stack frames follow...)
6814 The display for frame zero does not begin with a program counter
6815 value, indicating that your program has stopped at the beginning of the
6816 code for line @code{993} of @code{builtin.c}.
6819 The value of parameter @code{data} in frame 1 has been replaced by
6820 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6821 only if it is a scalar (integer, pointer, enumeration, etc). See command
6822 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6823 on how to configure the way function parameter values are printed.
6825 @cindex optimized out, in backtrace
6826 @cindex function call arguments, optimized out
6827 If your program was compiled with optimizations, some compilers will
6828 optimize away arguments passed to functions if those arguments are
6829 never used after the call. Such optimizations generate code that
6830 passes arguments through registers, but doesn't store those arguments
6831 in the stack frame. @value{GDBN} has no way of displaying such
6832 arguments in stack frames other than the innermost one. Here's what
6833 such a backtrace might look like:
6837 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6839 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6840 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6842 (More stack frames follow...)
6847 The values of arguments that were not saved in their stack frames are
6848 shown as @samp{<optimized out>}.
6850 If you need to display the values of such optimized-out arguments,
6851 either deduce that from other variables whose values depend on the one
6852 you are interested in, or recompile without optimizations.
6854 @cindex backtrace beyond @code{main} function
6855 @cindex program entry point
6856 @cindex startup code, and backtrace
6857 Most programs have a standard user entry point---a place where system
6858 libraries and startup code transition into user code. For C this is
6859 @code{main}@footnote{
6860 Note that embedded programs (the so-called ``free-standing''
6861 environment) are not required to have a @code{main} function as the
6862 entry point. They could even have multiple entry points.}.
6863 When @value{GDBN} finds the entry function in a backtrace
6864 it will terminate the backtrace, to avoid tracing into highly
6865 system-specific (and generally uninteresting) code.
6867 If you need to examine the startup code, or limit the number of levels
6868 in a backtrace, you can change this behavior:
6871 @item set backtrace past-main
6872 @itemx set backtrace past-main on
6873 @kindex set backtrace
6874 Backtraces will continue past the user entry point.
6876 @item set backtrace past-main off
6877 Backtraces will stop when they encounter the user entry point. This is the
6880 @item show backtrace past-main
6881 @kindex show backtrace
6882 Display the current user entry point backtrace policy.
6884 @item set backtrace past-entry
6885 @itemx set backtrace past-entry on
6886 Backtraces will continue past the internal entry point of an application.
6887 This entry point is encoded by the linker when the application is built,
6888 and is likely before the user entry point @code{main} (or equivalent) is called.
6890 @item set backtrace past-entry off
6891 Backtraces will stop when they encounter the internal entry point of an
6892 application. This is the default.
6894 @item show backtrace past-entry
6895 Display the current internal entry point backtrace policy.
6897 @item set backtrace limit @var{n}
6898 @itemx set backtrace limit 0
6899 @itemx set backtrace limit unlimited
6900 @cindex backtrace limit
6901 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6902 or zero means unlimited levels.
6904 @item show backtrace limit
6905 Display the current limit on backtrace levels.
6908 You can control how file names are displayed.
6911 @item set filename-display
6912 @itemx set filename-display relative
6913 @cindex filename-display
6914 Display file names relative to the compilation directory. This is the default.
6916 @item set filename-display basename
6917 Display only basename of a filename.
6919 @item set filename-display absolute
6920 Display an absolute filename.
6922 @item show filename-display
6923 Show the current way to display filenames.
6926 @node Frame Filter Management
6927 @section Management of Frame Filters.
6928 @cindex managing frame filters
6930 Frame filters are Python based utilities to manage and decorate the
6931 output of frames. @xref{Frame Filter API}, for further information.
6933 Managing frame filters is performed by several commands available
6934 within @value{GDBN}, detailed here.
6937 @kindex info frame-filter
6938 @item info frame-filter
6939 Print a list of installed frame filters from all dictionaries, showing
6940 their name, priority and enabled status.
6942 @kindex disable frame-filter
6943 @anchor{disable frame-filter all}
6944 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6945 Disable a frame filter in the dictionary matching
6946 @var{filter-dictionary} and @var{filter-name}. The
6947 @var{filter-dictionary} may be @code{all}, @code{global},
6948 @code{progspace}, or the name of the object file where the frame filter
6949 dictionary resides. When @code{all} is specified, all frame filters
6950 across all dictionaries are disabled. The @var{filter-name} is the name
6951 of the frame filter and is used when @code{all} is not the option for
6952 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6953 may be enabled again later.
6955 @kindex enable frame-filter
6956 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6957 Enable a frame filter in the dictionary matching
6958 @var{filter-dictionary} and @var{filter-name}. The
6959 @var{filter-dictionary} may be @code{all}, @code{global},
6960 @code{progspace} or the name of the object file where the frame filter
6961 dictionary resides. When @code{all} is specified, all frame filters across
6962 all dictionaries are enabled. The @var{filter-name} is the name of the frame
6963 filter and is used when @code{all} is not the option for
6964 @var{filter-dictionary}.
6969 (gdb) info frame-filter
6971 global frame-filters:
6972 Priority Enabled Name
6973 1000 No PrimaryFunctionFilter
6976 progspace /build/test frame-filters:
6977 Priority Enabled Name
6978 100 Yes ProgspaceFilter
6980 objfile /build/test frame-filters:
6981 Priority Enabled Name
6982 999 Yes BuildProgra Filter
6984 (gdb) disable frame-filter /build/test BuildProgramFilter
6985 (gdb) info frame-filter
6987 global frame-filters:
6988 Priority Enabled Name
6989 1000 No PrimaryFunctionFilter
6992 progspace /build/test frame-filters:
6993 Priority Enabled Name
6994 100 Yes ProgspaceFilter
6996 objfile /build/test frame-filters:
6997 Priority Enabled Name
6998 999 No BuildProgramFilter
7000 (gdb) enable frame-filter global PrimaryFunctionFilter
7001 (gdb) info frame-filter
7003 global frame-filters:
7004 Priority Enabled Name
7005 1000 Yes PrimaryFunctionFilter
7008 progspace /build/test frame-filters:
7009 Priority Enabled Name
7010 100 Yes ProgspaceFilter
7012 objfile /build/test frame-filters:
7013 Priority Enabled Name
7014 999 No BuildProgramFilter
7017 @kindex set frame-filter priority
7018 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7019 Set the @var{priority} of a frame filter in the dictionary matching
7020 @var{filter-dictionary}, and the frame filter name matching
7021 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7022 @code{progspace} or the name of the object file where the frame filter
7023 dictionary resides. The @var{priority} is an integer.
7025 @kindex show frame-filter priority
7026 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7027 Show the @var{priority} of a frame filter in the dictionary matching
7028 @var{filter-dictionary}, and the frame filter name matching
7029 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7030 @code{progspace} or the name of the object file where the frame filter
7036 (gdb) info frame-filter
7038 global frame-filters:
7039 Priority Enabled Name
7040 1000 Yes PrimaryFunctionFilter
7043 progspace /build/test frame-filters:
7044 Priority Enabled Name
7045 100 Yes ProgspaceFilter
7047 objfile /build/test frame-filters:
7048 Priority Enabled Name
7049 999 No BuildProgramFilter
7051 (gdb) set frame-filter priority global Reverse 50
7052 (gdb) info frame-filter
7054 global frame-filters:
7055 Priority Enabled Name
7056 1000 Yes PrimaryFunctionFilter
7059 progspace /build/test frame-filters:
7060 Priority Enabled Name
7061 100 Yes ProgspaceFilter
7063 objfile /build/test frame-filters:
7064 Priority Enabled Name
7065 999 No BuildProgramFilter
7070 @section Selecting a Frame
7072 Most commands for examining the stack and other data in your program work on
7073 whichever stack frame is selected at the moment. Here are the commands for
7074 selecting a stack frame; all of them finish by printing a brief description
7075 of the stack frame just selected.
7078 @kindex frame@r{, selecting}
7079 @kindex f @r{(@code{frame})}
7082 Select frame number @var{n}. Recall that frame zero is the innermost
7083 (currently executing) frame, frame one is the frame that called the
7084 innermost one, and so on. The highest-numbered frame is the one for
7087 @item frame @var{addr}
7089 Select the frame at address @var{addr}. This is useful mainly if the
7090 chaining of stack frames has been damaged by a bug, making it
7091 impossible for @value{GDBN} to assign numbers properly to all frames. In
7092 addition, this can be useful when your program has multiple stacks and
7093 switches between them.
7095 On the SPARC architecture, @code{frame} needs two addresses to
7096 select an arbitrary frame: a frame pointer and a stack pointer.
7098 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7099 pointer and a program counter.
7101 On the 29k architecture, it needs three addresses: a register stack
7102 pointer, a program counter, and a memory stack pointer.
7106 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7107 numbers @var{n}, this advances toward the outermost frame, to higher
7108 frame numbers, to frames that have existed longer.
7111 @kindex do @r{(@code{down})}
7113 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7114 positive numbers @var{n}, this advances toward the innermost frame, to
7115 lower frame numbers, to frames that were created more recently.
7116 You may abbreviate @code{down} as @code{do}.
7119 All of these commands end by printing two lines of output describing the
7120 frame. The first line shows the frame number, the function name, the
7121 arguments, and the source file and line number of execution in that
7122 frame. The second line shows the text of that source line.
7130 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7132 10 read_input_file (argv[i]);
7136 After such a printout, the @code{list} command with no arguments
7137 prints ten lines centered on the point of execution in the frame.
7138 You can also edit the program at the point of execution with your favorite
7139 editing program by typing @code{edit}.
7140 @xref{List, ,Printing Source Lines},
7144 @kindex down-silently
7146 @item up-silently @var{n}
7147 @itemx down-silently @var{n}
7148 These two commands are variants of @code{up} and @code{down},
7149 respectively; they differ in that they do their work silently, without
7150 causing display of the new frame. They are intended primarily for use
7151 in @value{GDBN} command scripts, where the output might be unnecessary and
7156 @section Information About a Frame
7158 There are several other commands to print information about the selected
7164 When used without any argument, this command does not change which
7165 frame is selected, but prints a brief description of the currently
7166 selected stack frame. It can be abbreviated @code{f}. With an
7167 argument, this command is used to select a stack frame.
7168 @xref{Selection, ,Selecting a Frame}.
7171 @kindex info f @r{(@code{info frame})}
7174 This command prints a verbose description of the selected stack frame,
7179 the address of the frame
7181 the address of the next frame down (called by this frame)
7183 the address of the next frame up (caller of this frame)
7185 the language in which the source code corresponding to this frame is written
7187 the address of the frame's arguments
7189 the address of the frame's local variables
7191 the program counter saved in it (the address of execution in the caller frame)
7193 which registers were saved in the frame
7196 @noindent The verbose description is useful when
7197 something has gone wrong that has made the stack format fail to fit
7198 the usual conventions.
7200 @item info frame @var{addr}
7201 @itemx info f @var{addr}
7202 Print a verbose description of the frame at address @var{addr}, without
7203 selecting that frame. The selected frame remains unchanged by this
7204 command. This requires the same kind of address (more than one for some
7205 architectures) that you specify in the @code{frame} command.
7206 @xref{Selection, ,Selecting a Frame}.
7210 Print the arguments of the selected frame, each on a separate line.
7214 Print the local variables of the selected frame, each on a separate
7215 line. These are all variables (declared either static or automatic)
7216 accessible at the point of execution of the selected frame.
7222 @chapter Examining Source Files
7224 @value{GDBN} can print parts of your program's source, since the debugging
7225 information recorded in the program tells @value{GDBN} what source files were
7226 used to build it. When your program stops, @value{GDBN} spontaneously prints
7227 the line where it stopped. Likewise, when you select a stack frame
7228 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7229 execution in that frame has stopped. You can print other portions of
7230 source files by explicit command.
7232 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7233 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7234 @value{GDBN} under @sc{gnu} Emacs}.
7237 * List:: Printing source lines
7238 * Specify Location:: How to specify code locations
7239 * Edit:: Editing source files
7240 * Search:: Searching source files
7241 * Source Path:: Specifying source directories
7242 * Machine Code:: Source and machine code
7246 @section Printing Source Lines
7249 @kindex l @r{(@code{list})}
7250 To print lines from a source file, use the @code{list} command
7251 (abbreviated @code{l}). By default, ten lines are printed.
7252 There are several ways to specify what part of the file you want to
7253 print; see @ref{Specify Location}, for the full list.
7255 Here are the forms of the @code{list} command most commonly used:
7258 @item list @var{linenum}
7259 Print lines centered around line number @var{linenum} in the
7260 current source file.
7262 @item list @var{function}
7263 Print lines centered around the beginning of function
7267 Print more lines. If the last lines printed were printed with a
7268 @code{list} command, this prints lines following the last lines
7269 printed; however, if the last line printed was a solitary line printed
7270 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7271 Stack}), this prints lines centered around that line.
7274 Print lines just before the lines last printed.
7277 @cindex @code{list}, how many lines to display
7278 By default, @value{GDBN} prints ten source lines with any of these forms of
7279 the @code{list} command. You can change this using @code{set listsize}:
7282 @kindex set listsize
7283 @item set listsize @var{count}
7284 @itemx set listsize unlimited
7285 Make the @code{list} command display @var{count} source lines (unless
7286 the @code{list} argument explicitly specifies some other number).
7287 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7289 @kindex show listsize
7291 Display the number of lines that @code{list} prints.
7294 Repeating a @code{list} command with @key{RET} discards the argument,
7295 so it is equivalent to typing just @code{list}. This is more useful
7296 than listing the same lines again. An exception is made for an
7297 argument of @samp{-}; that argument is preserved in repetition so that
7298 each repetition moves up in the source file.
7300 In general, the @code{list} command expects you to supply zero, one or two
7301 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7302 of writing them (@pxref{Specify Location}), but the effect is always
7303 to specify some source line.
7305 Here is a complete description of the possible arguments for @code{list}:
7308 @item list @var{linespec}
7309 Print lines centered around the line specified by @var{linespec}.
7311 @item list @var{first},@var{last}
7312 Print lines from @var{first} to @var{last}. Both arguments are
7313 linespecs. When a @code{list} command has two linespecs, and the
7314 source file of the second linespec is omitted, this refers to
7315 the same source file as the first linespec.
7317 @item list ,@var{last}
7318 Print lines ending with @var{last}.
7320 @item list @var{first},
7321 Print lines starting with @var{first}.
7324 Print lines just after the lines last printed.
7327 Print lines just before the lines last printed.
7330 As described in the preceding table.
7333 @node Specify Location
7334 @section Specifying a Location
7335 @cindex specifying location
7338 Several @value{GDBN} commands accept arguments that specify a location
7339 of your program's code. Since @value{GDBN} is a source-level
7340 debugger, a location usually specifies some line in the source code;
7341 for that reason, locations are also known as @dfn{linespecs}.
7343 Here are all the different ways of specifying a code location that
7344 @value{GDBN} understands:
7348 Specifies the line number @var{linenum} of the current source file.
7351 @itemx +@var{offset}
7352 Specifies the line @var{offset} lines before or after the @dfn{current
7353 line}. For the @code{list} command, the current line is the last one
7354 printed; for the breakpoint commands, this is the line at which
7355 execution stopped in the currently selected @dfn{stack frame}
7356 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7357 used as the second of the two linespecs in a @code{list} command,
7358 this specifies the line @var{offset} lines up or down from the first
7361 @item @var{filename}:@var{linenum}
7362 Specifies the line @var{linenum} in the source file @var{filename}.
7363 If @var{filename} is a relative file name, then it will match any
7364 source file name with the same trailing components. For example, if
7365 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7366 name of @file{/build/trunk/gcc/expr.c}, but not
7367 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7369 @item @var{function}
7370 Specifies the line that begins the body of the function @var{function}.
7371 For example, in C, this is the line with the open brace.
7373 @item @var{function}:@var{label}
7374 Specifies the line where @var{label} appears in @var{function}.
7376 @item @var{filename}:@var{function}
7377 Specifies the line that begins the body of the function @var{function}
7378 in the file @var{filename}. You only need the file name with a
7379 function name to avoid ambiguity when there are identically named
7380 functions in different source files.
7383 Specifies the line at which the label named @var{label} appears.
7384 @value{GDBN} searches for the label in the function corresponding to
7385 the currently selected stack frame. If there is no current selected
7386 stack frame (for instance, if the inferior is not running), then
7387 @value{GDBN} will not search for a label.
7389 @item *@var{address}
7390 Specifies the program address @var{address}. For line-oriented
7391 commands, such as @code{list} and @code{edit}, this specifies a source
7392 line that contains @var{address}. For @code{break} and other
7393 breakpoint oriented commands, this can be used to set breakpoints in
7394 parts of your program which do not have debugging information or
7397 Here @var{address} may be any expression valid in the current working
7398 language (@pxref{Languages, working language}) that specifies a code
7399 address. In addition, as a convenience, @value{GDBN} extends the
7400 semantics of expressions used in locations to cover the situations
7401 that frequently happen during debugging. Here are the various forms
7405 @item @var{expression}
7406 Any expression valid in the current working language.
7408 @item @var{funcaddr}
7409 An address of a function or procedure derived from its name. In C,
7410 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7411 simply the function's name @var{function} (and actually a special case
7412 of a valid expression). In Pascal and Modula-2, this is
7413 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7414 (although the Pascal form also works).
7416 This form specifies the address of the function's first instruction,
7417 before the stack frame and arguments have been set up.
7419 @item '@var{filename}'::@var{funcaddr}
7420 Like @var{funcaddr} above, but also specifies the name of the source
7421 file explicitly. This is useful if the name of the function does not
7422 specify the function unambiguously, e.g., if there are several
7423 functions with identical names in different source files.
7426 @cindex breakpoint at static probe point
7427 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7428 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7429 applications to embed static probes. @xref{Static Probe Points}, for more
7430 information on finding and using static probes. This form of linespec
7431 specifies the location of such a static probe.
7433 If @var{objfile} is given, only probes coming from that shared library
7434 or executable matching @var{objfile} as a regular expression are considered.
7435 If @var{provider} is given, then only probes from that provider are considered.
7436 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7437 each one of those probes.
7443 @section Editing Source Files
7444 @cindex editing source files
7447 @kindex e @r{(@code{edit})}
7448 To edit the lines in a source file, use the @code{edit} command.
7449 The editing program of your choice
7450 is invoked with the current line set to
7451 the active line in the program.
7452 Alternatively, there are several ways to specify what part of the file you
7453 want to print if you want to see other parts of the program:
7456 @item edit @var{location}
7457 Edit the source file specified by @code{location}. Editing starts at
7458 that @var{location}, e.g., at the specified source line of the
7459 specified file. @xref{Specify Location}, for all the possible forms
7460 of the @var{location} argument; here are the forms of the @code{edit}
7461 command most commonly used:
7464 @item edit @var{number}
7465 Edit the current source file with @var{number} as the active line number.
7467 @item edit @var{function}
7468 Edit the file containing @var{function} at the beginning of its definition.
7473 @subsection Choosing your Editor
7474 You can customize @value{GDBN} to use any editor you want
7476 The only restriction is that your editor (say @code{ex}), recognizes the
7477 following command-line syntax:
7479 ex +@var{number} file
7481 The optional numeric value +@var{number} specifies the number of the line in
7482 the file where to start editing.}.
7483 By default, it is @file{@value{EDITOR}}, but you can change this
7484 by setting the environment variable @code{EDITOR} before using
7485 @value{GDBN}. For example, to configure @value{GDBN} to use the
7486 @code{vi} editor, you could use these commands with the @code{sh} shell:
7492 or in the @code{csh} shell,
7494 setenv EDITOR /usr/bin/vi
7499 @section Searching Source Files
7500 @cindex searching source files
7502 There are two commands for searching through the current source file for a
7507 @kindex forward-search
7508 @kindex fo @r{(@code{forward-search})}
7509 @item forward-search @var{regexp}
7510 @itemx search @var{regexp}
7511 The command @samp{forward-search @var{regexp}} checks each line,
7512 starting with the one following the last line listed, for a match for
7513 @var{regexp}. It lists the line that is found. You can use the
7514 synonym @samp{search @var{regexp}} or abbreviate the command name as
7517 @kindex reverse-search
7518 @item reverse-search @var{regexp}
7519 The command @samp{reverse-search @var{regexp}} checks each line, starting
7520 with the one before the last line listed and going backward, for a match
7521 for @var{regexp}. It lists the line that is found. You can abbreviate
7522 this command as @code{rev}.
7526 @section Specifying Source Directories
7529 @cindex directories for source files
7530 Executable programs sometimes do not record the directories of the source
7531 files from which they were compiled, just the names. Even when they do,
7532 the directories could be moved between the compilation and your debugging
7533 session. @value{GDBN} has a list of directories to search for source files;
7534 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7535 it tries all the directories in the list, in the order they are present
7536 in the list, until it finds a file with the desired name.
7538 For example, suppose an executable references the file
7539 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7540 @file{/mnt/cross}. The file is first looked up literally; if this
7541 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7542 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7543 message is printed. @value{GDBN} does not look up the parts of the
7544 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7545 Likewise, the subdirectories of the source path are not searched: if
7546 the source path is @file{/mnt/cross}, and the binary refers to
7547 @file{foo.c}, @value{GDBN} would not find it under
7548 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7550 Plain file names, relative file names with leading directories, file
7551 names containing dots, etc.@: are all treated as described above; for
7552 instance, if the source path is @file{/mnt/cross}, and the source file
7553 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7554 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7555 that---@file{/mnt/cross/foo.c}.
7557 Note that the executable search path is @emph{not} used to locate the
7560 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7561 any information it has cached about where source files are found and where
7562 each line is in the file.
7566 When you start @value{GDBN}, its source path includes only @samp{cdir}
7567 and @samp{cwd}, in that order.
7568 To add other directories, use the @code{directory} command.
7570 The search path is used to find both program source files and @value{GDBN}
7571 script files (read using the @samp{-command} option and @samp{source} command).
7573 In addition to the source path, @value{GDBN} provides a set of commands
7574 that manage a list of source path substitution rules. A @dfn{substitution
7575 rule} specifies how to rewrite source directories stored in the program's
7576 debug information in case the sources were moved to a different
7577 directory between compilation and debugging. A rule is made of
7578 two strings, the first specifying what needs to be rewritten in
7579 the path, and the second specifying how it should be rewritten.
7580 In @ref{set substitute-path}, we name these two parts @var{from} and
7581 @var{to} respectively. @value{GDBN} does a simple string replacement
7582 of @var{from} with @var{to} at the start of the directory part of the
7583 source file name, and uses that result instead of the original file
7584 name to look up the sources.
7586 Using the previous example, suppose the @file{foo-1.0} tree has been
7587 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7588 @value{GDBN} to replace @file{/usr/src} in all source path names with
7589 @file{/mnt/cross}. The first lookup will then be
7590 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7591 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7592 substitution rule, use the @code{set substitute-path} command
7593 (@pxref{set substitute-path}).
7595 To avoid unexpected substitution results, a rule is applied only if the
7596 @var{from} part of the directory name ends at a directory separator.
7597 For instance, a rule substituting @file{/usr/source} into
7598 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7599 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7600 is applied only at the beginning of the directory name, this rule will
7601 not be applied to @file{/root/usr/source/baz.c} either.
7603 In many cases, you can achieve the same result using the @code{directory}
7604 command. However, @code{set substitute-path} can be more efficient in
7605 the case where the sources are organized in a complex tree with multiple
7606 subdirectories. With the @code{directory} command, you need to add each
7607 subdirectory of your project. If you moved the entire tree while
7608 preserving its internal organization, then @code{set substitute-path}
7609 allows you to direct the debugger to all the sources with one single
7612 @code{set substitute-path} is also more than just a shortcut command.
7613 The source path is only used if the file at the original location no
7614 longer exists. On the other hand, @code{set substitute-path} modifies
7615 the debugger behavior to look at the rewritten location instead. So, if
7616 for any reason a source file that is not relevant to your executable is
7617 located at the original location, a substitution rule is the only
7618 method available to point @value{GDBN} at the new location.
7620 @cindex @samp{--with-relocated-sources}
7621 @cindex default source path substitution
7622 You can configure a default source path substitution rule by
7623 configuring @value{GDBN} with the
7624 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7625 should be the name of a directory under @value{GDBN}'s configured
7626 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7627 directory names in debug information under @var{dir} will be adjusted
7628 automatically if the installed @value{GDBN} is moved to a new
7629 location. This is useful if @value{GDBN}, libraries or executables
7630 with debug information and corresponding source code are being moved
7634 @item directory @var{dirname} @dots{}
7635 @item dir @var{dirname} @dots{}
7636 Add directory @var{dirname} to the front of the source path. Several
7637 directory names may be given to this command, separated by @samp{:}
7638 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7639 part of absolute file names) or
7640 whitespace. You may specify a directory that is already in the source
7641 path; this moves it forward, so @value{GDBN} searches it sooner.
7645 @vindex $cdir@r{, convenience variable}
7646 @vindex $cwd@r{, convenience variable}
7647 @cindex compilation directory
7648 @cindex current directory
7649 @cindex working directory
7650 @cindex directory, current
7651 @cindex directory, compilation
7652 You can use the string @samp{$cdir} to refer to the compilation
7653 directory (if one is recorded), and @samp{$cwd} to refer to the current
7654 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7655 tracks the current working directory as it changes during your @value{GDBN}
7656 session, while the latter is immediately expanded to the current
7657 directory at the time you add an entry to the source path.
7660 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7662 @c RET-repeat for @code{directory} is explicitly disabled, but since
7663 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7665 @item set directories @var{path-list}
7666 @kindex set directories
7667 Set the source path to @var{path-list}.
7668 @samp{$cdir:$cwd} are added if missing.
7670 @item show directories
7671 @kindex show directories
7672 Print the source path: show which directories it contains.
7674 @anchor{set substitute-path}
7675 @item set substitute-path @var{from} @var{to}
7676 @kindex set substitute-path
7677 Define a source path substitution rule, and add it at the end of the
7678 current list of existing substitution rules. If a rule with the same
7679 @var{from} was already defined, then the old rule is also deleted.
7681 For example, if the file @file{/foo/bar/baz.c} was moved to
7682 @file{/mnt/cross/baz.c}, then the command
7685 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7689 will tell @value{GDBN} to replace @samp{/usr/src} with
7690 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7691 @file{baz.c} even though it was moved.
7693 In the case when more than one substitution rule have been defined,
7694 the rules are evaluated one by one in the order where they have been
7695 defined. The first one matching, if any, is selected to perform
7698 For instance, if we had entered the following commands:
7701 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7702 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7706 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7707 @file{/mnt/include/defs.h} by using the first rule. However, it would
7708 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7709 @file{/mnt/src/lib/foo.c}.
7712 @item unset substitute-path [path]
7713 @kindex unset substitute-path
7714 If a path is specified, search the current list of substitution rules
7715 for a rule that would rewrite that path. Delete that rule if found.
7716 A warning is emitted by the debugger if no rule could be found.
7718 If no path is specified, then all substitution rules are deleted.
7720 @item show substitute-path [path]
7721 @kindex show substitute-path
7722 If a path is specified, then print the source path substitution rule
7723 which would rewrite that path, if any.
7725 If no path is specified, then print all existing source path substitution
7730 If your source path is cluttered with directories that are no longer of
7731 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7732 versions of source. You can correct the situation as follows:
7736 Use @code{directory} with no argument to reset the source path to its default value.
7739 Use @code{directory} with suitable arguments to reinstall the
7740 directories you want in the source path. You can add all the
7741 directories in one command.
7745 @section Source and Machine Code
7746 @cindex source line and its code address
7748 You can use the command @code{info line} to map source lines to program
7749 addresses (and vice versa), and the command @code{disassemble} to display
7750 a range of addresses as machine instructions. You can use the command
7751 @code{set disassemble-next-line} to set whether to disassemble next
7752 source line when execution stops. When run under @sc{gnu} Emacs
7753 mode, the @code{info line} command causes the arrow to point to the
7754 line specified. Also, @code{info line} prints addresses in symbolic form as
7759 @item info line @var{linespec}
7760 Print the starting and ending addresses of the compiled code for
7761 source line @var{linespec}. You can specify source lines in any of
7762 the ways documented in @ref{Specify Location}.
7765 For example, we can use @code{info line} to discover the location of
7766 the object code for the first line of function
7767 @code{m4_changequote}:
7769 @c FIXME: I think this example should also show the addresses in
7770 @c symbolic form, as they usually would be displayed.
7772 (@value{GDBP}) info line m4_changequote
7773 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7777 @cindex code address and its source line
7778 We can also inquire (using @code{*@var{addr}} as the form for
7779 @var{linespec}) what source line covers a particular address:
7781 (@value{GDBP}) info line *0x63ff
7782 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7785 @cindex @code{$_} and @code{info line}
7786 @cindex @code{x} command, default address
7787 @kindex x@r{(examine), and} info line
7788 After @code{info line}, the default address for the @code{x} command
7789 is changed to the starting address of the line, so that @samp{x/i} is
7790 sufficient to begin examining the machine code (@pxref{Memory,
7791 ,Examining Memory}). Also, this address is saved as the value of the
7792 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7797 @cindex assembly instructions
7798 @cindex instructions, assembly
7799 @cindex machine instructions
7800 @cindex listing machine instructions
7802 @itemx disassemble /m
7803 @itemx disassemble /r
7804 This specialized command dumps a range of memory as machine
7805 instructions. It can also print mixed source+disassembly by specifying
7806 the @code{/m} modifier and print the raw instructions in hex as well as
7807 in symbolic form by specifying the @code{/r}.
7808 The default memory range is the function surrounding the
7809 program counter of the selected frame. A single argument to this
7810 command is a program counter value; @value{GDBN} dumps the function
7811 surrounding this value. When two arguments are given, they should
7812 be separated by a comma, possibly surrounded by whitespace. The
7813 arguments specify a range of addresses to dump, in one of two forms:
7816 @item @var{start},@var{end}
7817 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7818 @item @var{start},+@var{length}
7819 the addresses from @var{start} (inclusive) to
7820 @code{@var{start}+@var{length}} (exclusive).
7824 When 2 arguments are specified, the name of the function is also
7825 printed (since there could be several functions in the given range).
7827 The argument(s) can be any expression yielding a numeric value, such as
7828 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7830 If the range of memory being disassembled contains current program counter,
7831 the instruction at that location is shown with a @code{=>} marker.
7834 The following example shows the disassembly of a range of addresses of
7835 HP PA-RISC 2.0 code:
7838 (@value{GDBP}) disas 0x32c4, 0x32e4
7839 Dump of assembler code from 0x32c4 to 0x32e4:
7840 0x32c4 <main+204>: addil 0,dp
7841 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7842 0x32cc <main+212>: ldil 0x3000,r31
7843 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7844 0x32d4 <main+220>: ldo 0(r31),rp
7845 0x32d8 <main+224>: addil -0x800,dp
7846 0x32dc <main+228>: ldo 0x588(r1),r26
7847 0x32e0 <main+232>: ldil 0x3000,r31
7848 End of assembler dump.
7851 Here is an example showing mixed source+assembly for Intel x86, when the
7852 program is stopped just after function prologue:
7855 (@value{GDBP}) disas /m main
7856 Dump of assembler code for function main:
7858 0x08048330 <+0>: push %ebp
7859 0x08048331 <+1>: mov %esp,%ebp
7860 0x08048333 <+3>: sub $0x8,%esp
7861 0x08048336 <+6>: and $0xfffffff0,%esp
7862 0x08048339 <+9>: sub $0x10,%esp
7864 6 printf ("Hello.\n");
7865 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7866 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7870 0x08048348 <+24>: mov $0x0,%eax
7871 0x0804834d <+29>: leave
7872 0x0804834e <+30>: ret
7874 End of assembler dump.
7877 Here is another example showing raw instructions in hex for AMD x86-64,
7880 (gdb) disas /r 0x400281,+10
7881 Dump of assembler code from 0x400281 to 0x40028b:
7882 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7883 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7884 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7885 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7886 End of assembler dump.
7889 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7890 So, for example, if you want to disassemble function @code{bar}
7891 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7892 and not @samp{disassemble foo.c:bar}.
7894 Some architectures have more than one commonly-used set of instruction
7895 mnemonics or other syntax.
7897 For programs that were dynamically linked and use shared libraries,
7898 instructions that call functions or branch to locations in the shared
7899 libraries might show a seemingly bogus location---it's actually a
7900 location of the relocation table. On some architectures, @value{GDBN}
7901 might be able to resolve these to actual function names.
7904 @kindex set disassembly-flavor
7905 @cindex Intel disassembly flavor
7906 @cindex AT&T disassembly flavor
7907 @item set disassembly-flavor @var{instruction-set}
7908 Select the instruction set to use when disassembling the
7909 program via the @code{disassemble} or @code{x/i} commands.
7911 Currently this command is only defined for the Intel x86 family. You
7912 can set @var{instruction-set} to either @code{intel} or @code{att}.
7913 The default is @code{att}, the AT&T flavor used by default by Unix
7914 assemblers for x86-based targets.
7916 @kindex show disassembly-flavor
7917 @item show disassembly-flavor
7918 Show the current setting of the disassembly flavor.
7922 @kindex set disassemble-next-line
7923 @kindex show disassemble-next-line
7924 @item set disassemble-next-line
7925 @itemx show disassemble-next-line
7926 Control whether or not @value{GDBN} will disassemble the next source
7927 line or instruction when execution stops. If ON, @value{GDBN} will
7928 display disassembly of the next source line when execution of the
7929 program being debugged stops. This is @emph{in addition} to
7930 displaying the source line itself, which @value{GDBN} always does if
7931 possible. If the next source line cannot be displayed for some reason
7932 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7933 info in the debug info), @value{GDBN} will display disassembly of the
7934 next @emph{instruction} instead of showing the next source line. If
7935 AUTO, @value{GDBN} will display disassembly of next instruction only
7936 if the source line cannot be displayed. This setting causes
7937 @value{GDBN} to display some feedback when you step through a function
7938 with no line info or whose source file is unavailable. The default is
7939 OFF, which means never display the disassembly of the next line or
7945 @chapter Examining Data
7947 @cindex printing data
7948 @cindex examining data
7951 The usual way to examine data in your program is with the @code{print}
7952 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7953 evaluates and prints the value of an expression of the language your
7954 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7955 Different Languages}). It may also print the expression using a
7956 Python-based pretty-printer (@pxref{Pretty Printing}).
7959 @item print @var{expr}
7960 @itemx print /@var{f} @var{expr}
7961 @var{expr} is an expression (in the source language). By default the
7962 value of @var{expr} is printed in a format appropriate to its data type;
7963 you can choose a different format by specifying @samp{/@var{f}}, where
7964 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7968 @itemx print /@var{f}
7969 @cindex reprint the last value
7970 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7971 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7972 conveniently inspect the same value in an alternative format.
7975 A more low-level way of examining data is with the @code{x} command.
7976 It examines data in memory at a specified address and prints it in a
7977 specified format. @xref{Memory, ,Examining Memory}.
7979 If you are interested in information about types, or about how the
7980 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7981 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7984 @cindex exploring hierarchical data structures
7986 Another way of examining values of expressions and type information is
7987 through the Python extension command @code{explore} (available only if
7988 the @value{GDBN} build is configured with @code{--with-python}). It
7989 offers an interactive way to start at the highest level (or, the most
7990 abstract level) of the data type of an expression (or, the data type
7991 itself) and explore all the way down to leaf scalar values/fields
7992 embedded in the higher level data types.
7995 @item explore @var{arg}
7996 @var{arg} is either an expression (in the source language), or a type
7997 visible in the current context of the program being debugged.
8000 The working of the @code{explore} command can be illustrated with an
8001 example. If a data type @code{struct ComplexStruct} is defined in your
8011 struct ComplexStruct
8013 struct SimpleStruct *ss_p;
8019 followed by variable declarations as
8022 struct SimpleStruct ss = @{ 10, 1.11 @};
8023 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8027 then, the value of the variable @code{cs} can be explored using the
8028 @code{explore} command as follows.
8032 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8033 the following fields:
8035 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8036 arr = <Enter 1 to explore this field of type `int [10]'>
8038 Enter the field number of choice:
8042 Since the fields of @code{cs} are not scalar values, you are being
8043 prompted to chose the field you want to explore. Let's say you choose
8044 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8045 pointer, you will be asked if it is pointing to a single value. From
8046 the declaration of @code{cs} above, it is indeed pointing to a single
8047 value, hence you enter @code{y}. If you enter @code{n}, then you will
8048 be asked if it were pointing to an array of values, in which case this
8049 field will be explored as if it were an array.
8052 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8053 Continue exploring it as a pointer to a single value [y/n]: y
8054 The value of `*(cs.ss_p)' is a struct/class of type `struct
8055 SimpleStruct' with the following fields:
8057 i = 10 .. (Value of type `int')
8058 d = 1.1100000000000001 .. (Value of type `double')
8060 Press enter to return to parent value:
8064 If the field @code{arr} of @code{cs} was chosen for exploration by
8065 entering @code{1} earlier, then since it is as array, you will be
8066 prompted to enter the index of the element in the array that you want
8070 `cs.arr' is an array of `int'.
8071 Enter the index of the element you want to explore in `cs.arr': 5
8073 `(cs.arr)[5]' is a scalar value of type `int'.
8077 Press enter to return to parent value:
8080 In general, at any stage of exploration, you can go deeper towards the
8081 leaf values by responding to the prompts appropriately, or hit the
8082 return key to return to the enclosing data structure (the @i{higher}
8083 level data structure).
8085 Similar to exploring values, you can use the @code{explore} command to
8086 explore types. Instead of specifying a value (which is typically a
8087 variable name or an expression valid in the current context of the
8088 program being debugged), you specify a type name. If you consider the
8089 same example as above, your can explore the type
8090 @code{struct ComplexStruct} by passing the argument
8091 @code{struct ComplexStruct} to the @code{explore} command.
8094 (gdb) explore struct ComplexStruct
8098 By responding to the prompts appropriately in the subsequent interactive
8099 session, you can explore the type @code{struct ComplexStruct} in a
8100 manner similar to how the value @code{cs} was explored in the above
8103 The @code{explore} command also has two sub-commands,
8104 @code{explore value} and @code{explore type}. The former sub-command is
8105 a way to explicitly specify that value exploration of the argument is
8106 being invoked, while the latter is a way to explicitly specify that type
8107 exploration of the argument is being invoked.
8110 @item explore value @var{expr}
8111 @cindex explore value
8112 This sub-command of @code{explore} explores the value of the
8113 expression @var{expr} (if @var{expr} is an expression valid in the
8114 current context of the program being debugged). The behavior of this
8115 command is identical to that of the behavior of the @code{explore}
8116 command being passed the argument @var{expr}.
8118 @item explore type @var{arg}
8119 @cindex explore type
8120 This sub-command of @code{explore} explores the type of @var{arg} (if
8121 @var{arg} is a type visible in the current context of program being
8122 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8123 is an expression valid in the current context of the program being
8124 debugged). If @var{arg} is a type, then the behavior of this command is
8125 identical to that of the @code{explore} command being passed the
8126 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8127 this command will be identical to that of the @code{explore} command
8128 being passed the type of @var{arg} as the argument.
8132 * Expressions:: Expressions
8133 * Ambiguous Expressions:: Ambiguous Expressions
8134 * Variables:: Program variables
8135 * Arrays:: Artificial arrays
8136 * Output Formats:: Output formats
8137 * Memory:: Examining memory
8138 * Auto Display:: Automatic display
8139 * Print Settings:: Print settings
8140 * Pretty Printing:: Python pretty printing
8141 * Value History:: Value history
8142 * Convenience Vars:: Convenience variables
8143 * Convenience Funs:: Convenience functions
8144 * Registers:: Registers
8145 * Floating Point Hardware:: Floating point hardware
8146 * Vector Unit:: Vector Unit
8147 * OS Information:: Auxiliary data provided by operating system
8148 * Memory Region Attributes:: Memory region attributes
8149 * Dump/Restore Files:: Copy between memory and a file
8150 * Core File Generation:: Cause a program dump its core
8151 * Character Sets:: Debugging programs that use a different
8152 character set than GDB does
8153 * Caching Target Data:: Data caching for targets
8154 * Searching Memory:: Searching memory for a sequence of bytes
8158 @section Expressions
8161 @code{print} and many other @value{GDBN} commands accept an expression and
8162 compute its value. Any kind of constant, variable or operator defined
8163 by the programming language you are using is valid in an expression in
8164 @value{GDBN}. This includes conditional expressions, function calls,
8165 casts, and string constants. It also includes preprocessor macros, if
8166 you compiled your program to include this information; see
8169 @cindex arrays in expressions
8170 @value{GDBN} supports array constants in expressions input by
8171 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8172 you can use the command @code{print @{1, 2, 3@}} to create an array
8173 of three integers. If you pass an array to a function or assign it
8174 to a program variable, @value{GDBN} copies the array to memory that
8175 is @code{malloc}ed in the target program.
8177 Because C is so widespread, most of the expressions shown in examples in
8178 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8179 Languages}, for information on how to use expressions in other
8182 In this section, we discuss operators that you can use in @value{GDBN}
8183 expressions regardless of your programming language.
8185 @cindex casts, in expressions
8186 Casts are supported in all languages, not just in C, because it is so
8187 useful to cast a number into a pointer in order to examine a structure
8188 at that address in memory.
8189 @c FIXME: casts supported---Mod2 true?
8191 @value{GDBN} supports these operators, in addition to those common
8192 to programming languages:
8196 @samp{@@} is a binary operator for treating parts of memory as arrays.
8197 @xref{Arrays, ,Artificial Arrays}, for more information.
8200 @samp{::} allows you to specify a variable in terms of the file or
8201 function where it is defined. @xref{Variables, ,Program Variables}.
8203 @cindex @{@var{type}@}
8204 @cindex type casting memory
8205 @cindex memory, viewing as typed object
8206 @cindex casts, to view memory
8207 @item @{@var{type}@} @var{addr}
8208 Refers to an object of type @var{type} stored at address @var{addr} in
8209 memory. The address @var{addr} may be any expression whose value is
8210 an integer or pointer (but parentheses are required around binary
8211 operators, just as in a cast). This construct is allowed regardless
8212 of what kind of data is normally supposed to reside at @var{addr}.
8215 @node Ambiguous Expressions
8216 @section Ambiguous Expressions
8217 @cindex ambiguous expressions
8219 Expressions can sometimes contain some ambiguous elements. For instance,
8220 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8221 a single function name to be defined several times, for application in
8222 different contexts. This is called @dfn{overloading}. Another example
8223 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8224 templates and is typically instantiated several times, resulting in
8225 the same function name being defined in different contexts.
8227 In some cases and depending on the language, it is possible to adjust
8228 the expression to remove the ambiguity. For instance in C@t{++}, you
8229 can specify the signature of the function you want to break on, as in
8230 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8231 qualified name of your function often makes the expression unambiguous
8234 When an ambiguity that needs to be resolved is detected, the debugger
8235 has the capability to display a menu of numbered choices for each
8236 possibility, and then waits for the selection with the prompt @samp{>}.
8237 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8238 aborts the current command. If the command in which the expression was
8239 used allows more than one choice to be selected, the next option in the
8240 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8243 For example, the following session excerpt shows an attempt to set a
8244 breakpoint at the overloaded symbol @code{String::after}.
8245 We choose three particular definitions of that function name:
8247 @c FIXME! This is likely to change to show arg type lists, at least
8250 (@value{GDBP}) b String::after
8253 [2] file:String.cc; line number:867
8254 [3] file:String.cc; line number:860
8255 [4] file:String.cc; line number:875
8256 [5] file:String.cc; line number:853
8257 [6] file:String.cc; line number:846
8258 [7] file:String.cc; line number:735
8260 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8261 Breakpoint 2 at 0xb344: file String.cc, line 875.
8262 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8263 Multiple breakpoints were set.
8264 Use the "delete" command to delete unwanted
8271 @kindex set multiple-symbols
8272 @item set multiple-symbols @var{mode}
8273 @cindex multiple-symbols menu
8275 This option allows you to adjust the debugger behavior when an expression
8278 By default, @var{mode} is set to @code{all}. If the command with which
8279 the expression is used allows more than one choice, then @value{GDBN}
8280 automatically selects all possible choices. For instance, inserting
8281 a breakpoint on a function using an ambiguous name results in a breakpoint
8282 inserted on each possible match. However, if a unique choice must be made,
8283 then @value{GDBN} uses the menu to help you disambiguate the expression.
8284 For instance, printing the address of an overloaded function will result
8285 in the use of the menu.
8287 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8288 when an ambiguity is detected.
8290 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8291 an error due to the ambiguity and the command is aborted.
8293 @kindex show multiple-symbols
8294 @item show multiple-symbols
8295 Show the current value of the @code{multiple-symbols} setting.
8299 @section Program Variables
8301 The most common kind of expression to use is the name of a variable
8304 Variables in expressions are understood in the selected stack frame
8305 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8309 global (or file-static)
8316 visible according to the scope rules of the
8317 programming language from the point of execution in that frame
8320 @noindent This means that in the function
8335 you can examine and use the variable @code{a} whenever your program is
8336 executing within the function @code{foo}, but you can only use or
8337 examine the variable @code{b} while your program is executing inside
8338 the block where @code{b} is declared.
8340 @cindex variable name conflict
8341 There is an exception: you can refer to a variable or function whose
8342 scope is a single source file even if the current execution point is not
8343 in this file. But it is possible to have more than one such variable or
8344 function with the same name (in different source files). If that
8345 happens, referring to that name has unpredictable effects. If you wish,
8346 you can specify a static variable in a particular function or file by
8347 using the colon-colon (@code{::}) notation:
8349 @cindex colon-colon, context for variables/functions
8351 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8352 @cindex @code{::}, context for variables/functions
8355 @var{file}::@var{variable}
8356 @var{function}::@var{variable}
8360 Here @var{file} or @var{function} is the name of the context for the
8361 static @var{variable}. In the case of file names, you can use quotes to
8362 make sure @value{GDBN} parses the file name as a single word---for example,
8363 to print a global value of @code{x} defined in @file{f2.c}:
8366 (@value{GDBP}) p 'f2.c'::x
8369 The @code{::} notation is normally used for referring to
8370 static variables, since you typically disambiguate uses of local variables
8371 in functions by selecting the appropriate frame and using the
8372 simple name of the variable. However, you may also use this notation
8373 to refer to local variables in frames enclosing the selected frame:
8382 process (a); /* Stop here */
8393 For example, if there is a breakpoint at the commented line,
8394 here is what you might see
8395 when the program stops after executing the call @code{bar(0)}:
8400 (@value{GDBP}) p bar::a
8403 #2 0x080483d0 in foo (a=5) at foobar.c:12
8406 (@value{GDBP}) p bar::a
8410 @cindex C@t{++} scope resolution
8411 These uses of @samp{::} are very rarely in conflict with the very
8412 similar use of the same notation in C@t{++}. When they are in
8413 conflict, the C@t{++} meaning takes precedence; however, this can be
8414 overridden by quoting the file or function name with single quotes.
8416 For example, suppose the program is stopped in a method of a class
8417 that has a field named @code{includefile}, and there is also an
8418 include file named @file{includefile} that defines a variable,
8422 (@value{GDBP}) p includefile
8424 (@value{GDBP}) p includefile::some_global
8425 A syntax error in expression, near `'.
8426 (@value{GDBP}) p 'includefile'::some_global
8430 @cindex wrong values
8431 @cindex variable values, wrong
8432 @cindex function entry/exit, wrong values of variables
8433 @cindex optimized code, wrong values of variables
8435 @emph{Warning:} Occasionally, a local variable may appear to have the
8436 wrong value at certain points in a function---just after entry to a new
8437 scope, and just before exit.
8439 You may see this problem when you are stepping by machine instructions.
8440 This is because, on most machines, it takes more than one instruction to
8441 set up a stack frame (including local variable definitions); if you are
8442 stepping by machine instructions, variables may appear to have the wrong
8443 values until the stack frame is completely built. On exit, it usually
8444 also takes more than one machine instruction to destroy a stack frame;
8445 after you begin stepping through that group of instructions, local
8446 variable definitions may be gone.
8448 This may also happen when the compiler does significant optimizations.
8449 To be sure of always seeing accurate values, turn off all optimization
8452 @cindex ``No symbol "foo" in current context''
8453 Another possible effect of compiler optimizations is to optimize
8454 unused variables out of existence, or assign variables to registers (as
8455 opposed to memory addresses). Depending on the support for such cases
8456 offered by the debug info format used by the compiler, @value{GDBN}
8457 might not be able to display values for such local variables. If that
8458 happens, @value{GDBN} will print a message like this:
8461 No symbol "foo" in current context.
8464 To solve such problems, either recompile without optimizations, or use a
8465 different debug info format, if the compiler supports several such
8466 formats. @xref{Compilation}, for more information on choosing compiler
8467 options. @xref{C, ,C and C@t{++}}, for more information about debug
8468 info formats that are best suited to C@t{++} programs.
8470 If you ask to print an object whose contents are unknown to
8471 @value{GDBN}, e.g., because its data type is not completely specified
8472 by the debug information, @value{GDBN} will say @samp{<incomplete
8473 type>}. @xref{Symbols, incomplete type}, for more about this.
8475 If you append @kbd{@@entry} string to a function parameter name you get its
8476 value at the time the function got called. If the value is not available an
8477 error message is printed. Entry values are available only with some compilers.
8478 Entry values are normally also printed at the function parameter list according
8479 to @ref{set print entry-values}.
8482 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8488 (gdb) print i@@entry
8492 Strings are identified as arrays of @code{char} values without specified
8493 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8494 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8495 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8496 defines literal string type @code{"char"} as @code{char} without a sign.
8501 signed char var1[] = "A";
8504 You get during debugging
8509 $2 = @{65 'A', 0 '\0'@}
8513 @section Artificial Arrays
8515 @cindex artificial array
8517 @kindex @@@r{, referencing memory as an array}
8518 It is often useful to print out several successive objects of the
8519 same type in memory; a section of an array, or an array of
8520 dynamically determined size for which only a pointer exists in the
8523 You can do this by referring to a contiguous span of memory as an
8524 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8525 operand of @samp{@@} should be the first element of the desired array
8526 and be an individual object. The right operand should be the desired length
8527 of the array. The result is an array value whose elements are all of
8528 the type of the left argument. The first element is actually the left
8529 argument; the second element comes from bytes of memory immediately
8530 following those that hold the first element, and so on. Here is an
8531 example. If a program says
8534 int *array = (int *) malloc (len * sizeof (int));
8538 you can print the contents of @code{array} with
8544 The left operand of @samp{@@} must reside in memory. Array values made
8545 with @samp{@@} in this way behave just like other arrays in terms of
8546 subscripting, and are coerced to pointers when used in expressions.
8547 Artificial arrays most often appear in expressions via the value history
8548 (@pxref{Value History, ,Value History}), after printing one out.
8550 Another way to create an artificial array is to use a cast.
8551 This re-interprets a value as if it were an array.
8552 The value need not be in memory:
8554 (@value{GDBP}) p/x (short[2])0x12345678
8555 $1 = @{0x1234, 0x5678@}
8558 As a convenience, if you leave the array length out (as in
8559 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8560 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8562 (@value{GDBP}) p/x (short[])0x12345678
8563 $2 = @{0x1234, 0x5678@}
8566 Sometimes the artificial array mechanism is not quite enough; in
8567 moderately complex data structures, the elements of interest may not
8568 actually be adjacent---for example, if you are interested in the values
8569 of pointers in an array. One useful work-around in this situation is
8570 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8571 Variables}) as a counter in an expression that prints the first
8572 interesting value, and then repeat that expression via @key{RET}. For
8573 instance, suppose you have an array @code{dtab} of pointers to
8574 structures, and you are interested in the values of a field @code{fv}
8575 in each structure. Here is an example of what you might type:
8585 @node Output Formats
8586 @section Output Formats
8588 @cindex formatted output
8589 @cindex output formats
8590 By default, @value{GDBN} prints a value according to its data type. Sometimes
8591 this is not what you want. For example, you might want to print a number
8592 in hex, or a pointer in decimal. Or you might want to view data in memory
8593 at a certain address as a character string or as an instruction. To do
8594 these things, specify an @dfn{output format} when you print a value.
8596 The simplest use of output formats is to say how to print a value
8597 already computed. This is done by starting the arguments of the
8598 @code{print} command with a slash and a format letter. The format
8599 letters supported are:
8603 Regard the bits of the value as an integer, and print the integer in
8607 Print as integer in signed decimal.
8610 Print as integer in unsigned decimal.
8613 Print as integer in octal.
8616 Print as integer in binary. The letter @samp{t} stands for ``two''.
8617 @footnote{@samp{b} cannot be used because these format letters are also
8618 used with the @code{x} command, where @samp{b} stands for ``byte'';
8619 see @ref{Memory,,Examining Memory}.}
8622 @cindex unknown address, locating
8623 @cindex locate address
8624 Print as an address, both absolute in hexadecimal and as an offset from
8625 the nearest preceding symbol. You can use this format used to discover
8626 where (in what function) an unknown address is located:
8629 (@value{GDBP}) p/a 0x54320
8630 $3 = 0x54320 <_initialize_vx+396>
8634 The command @code{info symbol 0x54320} yields similar results.
8635 @xref{Symbols, info symbol}.
8638 Regard as an integer and print it as a character constant. This
8639 prints both the numerical value and its character representation. The
8640 character representation is replaced with the octal escape @samp{\nnn}
8641 for characters outside the 7-bit @sc{ascii} range.
8643 Without this format, @value{GDBN} displays @code{char},
8644 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8645 constants. Single-byte members of vectors are displayed as integer
8649 Regard the bits of the value as a floating point number and print
8650 using typical floating point syntax.
8653 @cindex printing strings
8654 @cindex printing byte arrays
8655 Regard as a string, if possible. With this format, pointers to single-byte
8656 data are displayed as null-terminated strings and arrays of single-byte data
8657 are displayed as fixed-length strings. Other values are displayed in their
8660 Without this format, @value{GDBN} displays pointers to and arrays of
8661 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8662 strings. Single-byte members of a vector are displayed as an integer
8666 Like @samp{x} formatting, the value is treated as an integer and
8667 printed as hexadecimal, but leading zeros are printed to pad the value
8668 to the size of the integer type.
8671 @cindex raw printing
8672 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8673 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8674 Printing}). This typically results in a higher-level display of the
8675 value's contents. The @samp{r} format bypasses any Python
8676 pretty-printer which might exist.
8679 For example, to print the program counter in hex (@pxref{Registers}), type
8686 Note that no space is required before the slash; this is because command
8687 names in @value{GDBN} cannot contain a slash.
8689 To reprint the last value in the value history with a different format,
8690 you can use the @code{print} command with just a format and no
8691 expression. For example, @samp{p/x} reprints the last value in hex.
8694 @section Examining Memory
8696 You can use the command @code{x} (for ``examine'') to examine memory in
8697 any of several formats, independently of your program's data types.
8699 @cindex examining memory
8701 @kindex x @r{(examine memory)}
8702 @item x/@var{nfu} @var{addr}
8705 Use the @code{x} command to examine memory.
8708 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8709 much memory to display and how to format it; @var{addr} is an
8710 expression giving the address where you want to start displaying memory.
8711 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8712 Several commands set convenient defaults for @var{addr}.
8715 @item @var{n}, the repeat count
8716 The repeat count is a decimal integer; the default is 1. It specifies
8717 how much memory (counting by units @var{u}) to display.
8718 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8721 @item @var{f}, the display format
8722 The display format is one of the formats used by @code{print}
8723 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8724 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8725 The default is @samp{x} (hexadecimal) initially. The default changes
8726 each time you use either @code{x} or @code{print}.
8728 @item @var{u}, the unit size
8729 The unit size is any of
8735 Halfwords (two bytes).
8737 Words (four bytes). This is the initial default.
8739 Giant words (eight bytes).
8742 Each time you specify a unit size with @code{x}, that size becomes the
8743 default unit the next time you use @code{x}. For the @samp{i} format,
8744 the unit size is ignored and is normally not written. For the @samp{s} format,
8745 the unit size defaults to @samp{b}, unless it is explicitly given.
8746 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8747 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8748 Note that the results depend on the programming language of the
8749 current compilation unit. If the language is C, the @samp{s}
8750 modifier will use the UTF-16 encoding while @samp{w} will use
8751 UTF-32. The encoding is set by the programming language and cannot
8754 @item @var{addr}, starting display address
8755 @var{addr} is the address where you want @value{GDBN} to begin displaying
8756 memory. The expression need not have a pointer value (though it may);
8757 it is always interpreted as an integer address of a byte of memory.
8758 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8759 @var{addr} is usually just after the last address examined---but several
8760 other commands also set the default address: @code{info breakpoints} (to
8761 the address of the last breakpoint listed), @code{info line} (to the
8762 starting address of a line), and @code{print} (if you use it to display
8763 a value from memory).
8766 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8767 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8768 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8769 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8770 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8772 Since the letters indicating unit sizes are all distinct from the
8773 letters specifying output formats, you do not have to remember whether
8774 unit size or format comes first; either order works. The output
8775 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8776 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8778 Even though the unit size @var{u} is ignored for the formats @samp{s}
8779 and @samp{i}, you might still want to use a count @var{n}; for example,
8780 @samp{3i} specifies that you want to see three machine instructions,
8781 including any operands. For convenience, especially when used with
8782 the @code{display} command, the @samp{i} format also prints branch delay
8783 slot instructions, if any, beyond the count specified, which immediately
8784 follow the last instruction that is within the count. The command
8785 @code{disassemble} gives an alternative way of inspecting machine
8786 instructions; see @ref{Machine Code,,Source and Machine Code}.
8788 All the defaults for the arguments to @code{x} are designed to make it
8789 easy to continue scanning memory with minimal specifications each time
8790 you use @code{x}. For example, after you have inspected three machine
8791 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8792 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8793 the repeat count @var{n} is used again; the other arguments default as
8794 for successive uses of @code{x}.
8796 When examining machine instructions, the instruction at current program
8797 counter is shown with a @code{=>} marker. For example:
8800 (@value{GDBP}) x/5i $pc-6
8801 0x804837f <main+11>: mov %esp,%ebp
8802 0x8048381 <main+13>: push %ecx
8803 0x8048382 <main+14>: sub $0x4,%esp
8804 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8805 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8808 @cindex @code{$_}, @code{$__}, and value history
8809 The addresses and contents printed by the @code{x} command are not saved
8810 in the value history because there is often too much of them and they
8811 would get in the way. Instead, @value{GDBN} makes these values available for
8812 subsequent use in expressions as values of the convenience variables
8813 @code{$_} and @code{$__}. After an @code{x} command, the last address
8814 examined is available for use in expressions in the convenience variable
8815 @code{$_}. The contents of that address, as examined, are available in
8816 the convenience variable @code{$__}.
8818 If the @code{x} command has a repeat count, the address and contents saved
8819 are from the last memory unit printed; this is not the same as the last
8820 address printed if several units were printed on the last line of output.
8822 @cindex remote memory comparison
8823 @cindex target memory comparison
8824 @cindex verify remote memory image
8825 @cindex verify target memory image
8826 When you are debugging a program running on a remote target machine
8827 (@pxref{Remote Debugging}), you may wish to verify the program's image
8828 in the remote machine's memory against the executable file you
8829 downloaded to the target. Or, on any target, you may want to check
8830 whether the program has corrupted its own read-only sections. The
8831 @code{compare-sections} command is provided for such situations.
8834 @kindex compare-sections
8835 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
8836 Compare the data of a loadable section @var{section-name} in the
8837 executable file of the program being debugged with the same section in
8838 the target machine's memory, and report any mismatches. With no
8839 arguments, compares all loadable sections. With an argument of
8840 @code{-r}, compares all loadable read-only sections.
8842 Note: for remote targets, this command can be accelerated if the
8843 target supports computing the CRC checksum of a block of memory
8844 (@pxref{qCRC packet}).
8848 @section Automatic Display
8849 @cindex automatic display
8850 @cindex display of expressions
8852 If you find that you want to print the value of an expression frequently
8853 (to see how it changes), you might want to add it to the @dfn{automatic
8854 display list} so that @value{GDBN} prints its value each time your program stops.
8855 Each expression added to the list is given a number to identify it;
8856 to remove an expression from the list, you specify that number.
8857 The automatic display looks like this:
8861 3: bar[5] = (struct hack *) 0x3804
8865 This display shows item numbers, expressions and their current values. As with
8866 displays you request manually using @code{x} or @code{print}, you can
8867 specify the output format you prefer; in fact, @code{display} decides
8868 whether to use @code{print} or @code{x} depending your format
8869 specification---it uses @code{x} if you specify either the @samp{i}
8870 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8874 @item display @var{expr}
8875 Add the expression @var{expr} to the list of expressions to display
8876 each time your program stops. @xref{Expressions, ,Expressions}.
8878 @code{display} does not repeat if you press @key{RET} again after using it.
8880 @item display/@var{fmt} @var{expr}
8881 For @var{fmt} specifying only a display format and not a size or
8882 count, add the expression @var{expr} to the auto-display list but
8883 arrange to display it each time in the specified format @var{fmt}.
8884 @xref{Output Formats,,Output Formats}.
8886 @item display/@var{fmt} @var{addr}
8887 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8888 number of units, add the expression @var{addr} as a memory address to
8889 be examined each time your program stops. Examining means in effect
8890 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8893 For example, @samp{display/i $pc} can be helpful, to see the machine
8894 instruction about to be executed each time execution stops (@samp{$pc}
8895 is a common name for the program counter; @pxref{Registers, ,Registers}).
8898 @kindex delete display
8900 @item undisplay @var{dnums}@dots{}
8901 @itemx delete display @var{dnums}@dots{}
8902 Remove items from the list of expressions to display. Specify the
8903 numbers of the displays that you want affected with the command
8904 argument @var{dnums}. It can be a single display number, one of the
8905 numbers shown in the first field of the @samp{info display} display;
8906 or it could be a range of display numbers, as in @code{2-4}.
8908 @code{undisplay} does not repeat if you press @key{RET} after using it.
8909 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8911 @kindex disable display
8912 @item disable display @var{dnums}@dots{}
8913 Disable the display of item numbers @var{dnums}. A disabled display
8914 item is not printed automatically, but is not forgotten. It may be
8915 enabled again later. Specify the numbers of the displays that you
8916 want affected with the command argument @var{dnums}. It can be a
8917 single display number, one of the numbers shown in the first field of
8918 the @samp{info display} display; or it could be a range of display
8919 numbers, as in @code{2-4}.
8921 @kindex enable display
8922 @item enable display @var{dnums}@dots{}
8923 Enable display of item numbers @var{dnums}. It becomes effective once
8924 again in auto display of its expression, until you specify otherwise.
8925 Specify the numbers of the displays that you want affected with the
8926 command argument @var{dnums}. It can be a single display number, one
8927 of the numbers shown in the first field of the @samp{info display}
8928 display; or it could be a range of display numbers, as in @code{2-4}.
8931 Display the current values of the expressions on the list, just as is
8932 done when your program stops.
8934 @kindex info display
8936 Print the list of expressions previously set up to display
8937 automatically, each one with its item number, but without showing the
8938 values. This includes disabled expressions, which are marked as such.
8939 It also includes expressions which would not be displayed right now
8940 because they refer to automatic variables not currently available.
8943 @cindex display disabled out of scope
8944 If a display expression refers to local variables, then it does not make
8945 sense outside the lexical context for which it was set up. Such an
8946 expression is disabled when execution enters a context where one of its
8947 variables is not defined. For example, if you give the command
8948 @code{display last_char} while inside a function with an argument
8949 @code{last_char}, @value{GDBN} displays this argument while your program
8950 continues to stop inside that function. When it stops elsewhere---where
8951 there is no variable @code{last_char}---the display is disabled
8952 automatically. The next time your program stops where @code{last_char}
8953 is meaningful, you can enable the display expression once again.
8955 @node Print Settings
8956 @section Print Settings
8958 @cindex format options
8959 @cindex print settings
8960 @value{GDBN} provides the following ways to control how arrays, structures,
8961 and symbols are printed.
8964 These settings are useful for debugging programs in any language:
8968 @item set print address
8969 @itemx set print address on
8970 @cindex print/don't print memory addresses
8971 @value{GDBN} prints memory addresses showing the location of stack
8972 traces, structure values, pointer values, breakpoints, and so forth,
8973 even when it also displays the contents of those addresses. The default
8974 is @code{on}. For example, this is what a stack frame display looks like with
8975 @code{set print address on}:
8980 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8982 530 if (lquote != def_lquote)
8986 @item set print address off
8987 Do not print addresses when displaying their contents. For example,
8988 this is the same stack frame displayed with @code{set print address off}:
8992 (@value{GDBP}) set print addr off
8994 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8995 530 if (lquote != def_lquote)
8999 You can use @samp{set print address off} to eliminate all machine
9000 dependent displays from the @value{GDBN} interface. For example, with
9001 @code{print address off}, you should get the same text for backtraces on
9002 all machines---whether or not they involve pointer arguments.
9005 @item show print address
9006 Show whether or not addresses are to be printed.
9009 When @value{GDBN} prints a symbolic address, it normally prints the
9010 closest earlier symbol plus an offset. If that symbol does not uniquely
9011 identify the address (for example, it is a name whose scope is a single
9012 source file), you may need to clarify. One way to do this is with
9013 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9014 you can set @value{GDBN} to print the source file and line number when
9015 it prints a symbolic address:
9018 @item set print symbol-filename on
9019 @cindex source file and line of a symbol
9020 @cindex symbol, source file and line
9021 Tell @value{GDBN} to print the source file name and line number of a
9022 symbol in the symbolic form of an address.
9024 @item set print symbol-filename off
9025 Do not print source file name and line number of a symbol. This is the
9028 @item show print symbol-filename
9029 Show whether or not @value{GDBN} will print the source file name and
9030 line number of a symbol in the symbolic form of an address.
9033 Another situation where it is helpful to show symbol filenames and line
9034 numbers is when disassembling code; @value{GDBN} shows you the line
9035 number and source file that corresponds to each instruction.
9037 Also, you may wish to see the symbolic form only if the address being
9038 printed is reasonably close to the closest earlier symbol:
9041 @item set print max-symbolic-offset @var{max-offset}
9042 @itemx set print max-symbolic-offset unlimited
9043 @cindex maximum value for offset of closest symbol
9044 Tell @value{GDBN} to only display the symbolic form of an address if the
9045 offset between the closest earlier symbol and the address is less than
9046 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9047 to always print the symbolic form of an address if any symbol precedes
9048 it. Zero is equivalent to @code{unlimited}.
9050 @item show print max-symbolic-offset
9051 Ask how large the maximum offset is that @value{GDBN} prints in a
9055 @cindex wild pointer, interpreting
9056 @cindex pointer, finding referent
9057 If you have a pointer and you are not sure where it points, try
9058 @samp{set print symbol-filename on}. Then you can determine the name
9059 and source file location of the variable where it points, using
9060 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9061 For example, here @value{GDBN} shows that a variable @code{ptt} points
9062 at another variable @code{t}, defined in @file{hi2.c}:
9065 (@value{GDBP}) set print symbol-filename on
9066 (@value{GDBP}) p/a ptt
9067 $4 = 0xe008 <t in hi2.c>
9071 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9072 does not show the symbol name and filename of the referent, even with
9073 the appropriate @code{set print} options turned on.
9076 You can also enable @samp{/a}-like formatting all the time using
9077 @samp{set print symbol on}:
9080 @item set print symbol on
9081 Tell @value{GDBN} to print the symbol corresponding to an address, if
9084 @item set print symbol off
9085 Tell @value{GDBN} not to print the symbol corresponding to an
9086 address. In this mode, @value{GDBN} will still print the symbol
9087 corresponding to pointers to functions. This is the default.
9089 @item show print symbol
9090 Show whether @value{GDBN} will display the symbol corresponding to an
9094 Other settings control how different kinds of objects are printed:
9097 @item set print array
9098 @itemx set print array on
9099 @cindex pretty print arrays
9100 Pretty print arrays. This format is more convenient to read,
9101 but uses more space. The default is off.
9103 @item set print array off
9104 Return to compressed format for arrays.
9106 @item show print array
9107 Show whether compressed or pretty format is selected for displaying
9110 @cindex print array indexes
9111 @item set print array-indexes
9112 @itemx set print array-indexes on
9113 Print the index of each element when displaying arrays. May be more
9114 convenient to locate a given element in the array or quickly find the
9115 index of a given element in that printed array. The default is off.
9117 @item set print array-indexes off
9118 Stop printing element indexes when displaying arrays.
9120 @item show print array-indexes
9121 Show whether the index of each element is printed when displaying
9124 @item set print elements @var{number-of-elements}
9125 @itemx set print elements unlimited
9126 @cindex number of array elements to print
9127 @cindex limit on number of printed array elements
9128 Set a limit on how many elements of an array @value{GDBN} will print.
9129 If @value{GDBN} is printing a large array, it stops printing after it has
9130 printed the number of elements set by the @code{set print elements} command.
9131 This limit also applies to the display of strings.
9132 When @value{GDBN} starts, this limit is set to 200.
9133 Setting @var{number-of-elements} to @code{unlimited} or zero means
9134 that the number of elements to print is unlimited.
9136 @item show print elements
9137 Display the number of elements of a large array that @value{GDBN} will print.
9138 If the number is 0, then the printing is unlimited.
9140 @item set print frame-arguments @var{value}
9141 @kindex set print frame-arguments
9142 @cindex printing frame argument values
9143 @cindex print all frame argument values
9144 @cindex print frame argument values for scalars only
9145 @cindex do not print frame argument values
9146 This command allows to control how the values of arguments are printed
9147 when the debugger prints a frame (@pxref{Frames}). The possible
9152 The values of all arguments are printed.
9155 Print the value of an argument only if it is a scalar. The value of more
9156 complex arguments such as arrays, structures, unions, etc, is replaced
9157 by @code{@dots{}}. This is the default. Here is an example where
9158 only scalar arguments are shown:
9161 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9166 None of the argument values are printed. Instead, the value of each argument
9167 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9170 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9175 By default, only scalar arguments are printed. This command can be used
9176 to configure the debugger to print the value of all arguments, regardless
9177 of their type. However, it is often advantageous to not print the value
9178 of more complex parameters. For instance, it reduces the amount of
9179 information printed in each frame, making the backtrace more readable.
9180 Also, it improves performance when displaying Ada frames, because
9181 the computation of large arguments can sometimes be CPU-intensive,
9182 especially in large applications. Setting @code{print frame-arguments}
9183 to @code{scalars} (the default) or @code{none} avoids this computation,
9184 thus speeding up the display of each Ada frame.
9186 @item show print frame-arguments
9187 Show how the value of arguments should be displayed when printing a frame.
9189 @item set print raw frame-arguments on
9190 Print frame arguments in raw, non pretty-printed, form.
9192 @item set print raw frame-arguments off
9193 Print frame arguments in pretty-printed form, if there is a pretty-printer
9194 for the value (@pxref{Pretty Printing}),
9195 otherwise print the value in raw form.
9196 This is the default.
9198 @item show print raw frame-arguments
9199 Show whether to print frame arguments in raw form.
9201 @anchor{set print entry-values}
9202 @item set print entry-values @var{value}
9203 @kindex set print entry-values
9204 Set printing of frame argument values at function entry. In some cases
9205 @value{GDBN} can determine the value of function argument which was passed by
9206 the function caller, even if the value was modified inside the called function
9207 and therefore is different. With optimized code, the current value could be
9208 unavailable, but the entry value may still be known.
9210 The default value is @code{default} (see below for its description). Older
9211 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9212 this feature will behave in the @code{default} setting the same way as with the
9215 This functionality is currently supported only by DWARF 2 debugging format and
9216 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9217 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9220 The @var{value} parameter can be one of the following:
9224 Print only actual parameter values, never print values from function entry
9228 #0 different (val=6)
9229 #0 lost (val=<optimized out>)
9231 #0 invalid (val=<optimized out>)
9235 Print only parameter values from function entry point. The actual parameter
9236 values are never printed.
9238 #0 equal (val@@entry=5)
9239 #0 different (val@@entry=5)
9240 #0 lost (val@@entry=5)
9241 #0 born (val@@entry=<optimized out>)
9242 #0 invalid (val@@entry=<optimized out>)
9246 Print only parameter values from function entry point. If value from function
9247 entry point is not known while the actual value is known, print the actual
9248 value for such parameter.
9250 #0 equal (val@@entry=5)
9251 #0 different (val@@entry=5)
9252 #0 lost (val@@entry=5)
9254 #0 invalid (val@@entry=<optimized out>)
9258 Print actual parameter values. If actual parameter value is not known while
9259 value from function entry point is known, print the entry point value for such
9263 #0 different (val=6)
9264 #0 lost (val@@entry=5)
9266 #0 invalid (val=<optimized out>)
9270 Always print both the actual parameter value and its value from function entry
9271 point, even if values of one or both are not available due to compiler
9274 #0 equal (val=5, val@@entry=5)
9275 #0 different (val=6, val@@entry=5)
9276 #0 lost (val=<optimized out>, val@@entry=5)
9277 #0 born (val=10, val@@entry=<optimized out>)
9278 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9282 Print the actual parameter value if it is known and also its value from
9283 function entry point if it is known. If neither is known, print for the actual
9284 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9285 values are known and identical, print the shortened
9286 @code{param=param@@entry=VALUE} notation.
9288 #0 equal (val=val@@entry=5)
9289 #0 different (val=6, val@@entry=5)
9290 #0 lost (val@@entry=5)
9292 #0 invalid (val=<optimized out>)
9296 Always print the actual parameter value. Print also its value from function
9297 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9298 if both values are known and identical, print the shortened
9299 @code{param=param@@entry=VALUE} notation.
9301 #0 equal (val=val@@entry=5)
9302 #0 different (val=6, val@@entry=5)
9303 #0 lost (val=<optimized out>, val@@entry=5)
9305 #0 invalid (val=<optimized out>)
9309 For analysis messages on possible failures of frame argument values at function
9310 entry resolution see @ref{set debug entry-values}.
9312 @item show print entry-values
9313 Show the method being used for printing of frame argument values at function
9316 @item set print repeats @var{number-of-repeats}
9317 @itemx set print repeats unlimited
9318 @cindex repeated array elements
9319 Set the threshold for suppressing display of repeated array
9320 elements. When the number of consecutive identical elements of an
9321 array exceeds the threshold, @value{GDBN} prints the string
9322 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9323 identical repetitions, instead of displaying the identical elements
9324 themselves. Setting the threshold to @code{unlimited} or zero will
9325 cause all elements to be individually printed. The default threshold
9328 @item show print repeats
9329 Display the current threshold for printing repeated identical
9332 @item set print null-stop
9333 @cindex @sc{null} elements in arrays
9334 Cause @value{GDBN} to stop printing the characters of an array when the first
9335 @sc{null} is encountered. This is useful when large arrays actually
9336 contain only short strings.
9339 @item show print null-stop
9340 Show whether @value{GDBN} stops printing an array on the first
9341 @sc{null} character.
9343 @item set print pretty on
9344 @cindex print structures in indented form
9345 @cindex indentation in structure display
9346 Cause @value{GDBN} to print structures in an indented format with one member
9347 per line, like this:
9362 @item set print pretty off
9363 Cause @value{GDBN} to print structures in a compact format, like this:
9367 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9368 meat = 0x54 "Pork"@}
9373 This is the default format.
9375 @item show print pretty
9376 Show which format @value{GDBN} is using to print structures.
9378 @item set print sevenbit-strings on
9379 @cindex eight-bit characters in strings
9380 @cindex octal escapes in strings
9381 Print using only seven-bit characters; if this option is set,
9382 @value{GDBN} displays any eight-bit characters (in strings or
9383 character values) using the notation @code{\}@var{nnn}. This setting is
9384 best if you are working in English (@sc{ascii}) and you use the
9385 high-order bit of characters as a marker or ``meta'' bit.
9387 @item set print sevenbit-strings off
9388 Print full eight-bit characters. This allows the use of more
9389 international character sets, and is the default.
9391 @item show print sevenbit-strings
9392 Show whether or not @value{GDBN} is printing only seven-bit characters.
9394 @item set print union on
9395 @cindex unions in structures, printing
9396 Tell @value{GDBN} to print unions which are contained in structures
9397 and other unions. This is the default setting.
9399 @item set print union off
9400 Tell @value{GDBN} not to print unions which are contained in
9401 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9404 @item show print union
9405 Ask @value{GDBN} whether or not it will print unions which are contained in
9406 structures and other unions.
9408 For example, given the declarations
9411 typedef enum @{Tree, Bug@} Species;
9412 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9413 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9424 struct thing foo = @{Tree, @{Acorn@}@};
9428 with @code{set print union on} in effect @samp{p foo} would print
9431 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9435 and with @code{set print union off} in effect it would print
9438 $1 = @{it = Tree, form = @{...@}@}
9442 @code{set print union} affects programs written in C-like languages
9448 These settings are of interest when debugging C@t{++} programs:
9451 @cindex demangling C@t{++} names
9452 @item set print demangle
9453 @itemx set print demangle on
9454 Print C@t{++} names in their source form rather than in the encoded
9455 (``mangled'') form passed to the assembler and linker for type-safe
9456 linkage. The default is on.
9458 @item show print demangle
9459 Show whether C@t{++} names are printed in mangled or demangled form.
9461 @item set print asm-demangle
9462 @itemx set print asm-demangle on
9463 Print C@t{++} names in their source form rather than their mangled form, even
9464 in assembler code printouts such as instruction disassemblies.
9467 @item show print asm-demangle
9468 Show whether C@t{++} names in assembly listings are printed in mangled
9471 @cindex C@t{++} symbol decoding style
9472 @cindex symbol decoding style, C@t{++}
9473 @kindex set demangle-style
9474 @item set demangle-style @var{style}
9475 Choose among several encoding schemes used by different compilers to
9476 represent C@t{++} names. The choices for @var{style} are currently:
9480 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9481 This is the default.
9484 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9487 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9490 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9493 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9494 @strong{Warning:} this setting alone is not sufficient to allow
9495 debugging @code{cfront}-generated executables. @value{GDBN} would
9496 require further enhancement to permit that.
9499 If you omit @var{style}, you will see a list of possible formats.
9501 @item show demangle-style
9502 Display the encoding style currently in use for decoding C@t{++} symbols.
9504 @item set print object
9505 @itemx set print object on
9506 @cindex derived type of an object, printing
9507 @cindex display derived types
9508 When displaying a pointer to an object, identify the @emph{actual}
9509 (derived) type of the object rather than the @emph{declared} type, using
9510 the virtual function table. Note that the virtual function table is
9511 required---this feature can only work for objects that have run-time
9512 type identification; a single virtual method in the object's declared
9513 type is sufficient. Note that this setting is also taken into account when
9514 working with variable objects via MI (@pxref{GDB/MI}).
9516 @item set print object off
9517 Display only the declared type of objects, without reference to the
9518 virtual function table. This is the default setting.
9520 @item show print object
9521 Show whether actual, or declared, object types are displayed.
9523 @item set print static-members
9524 @itemx set print static-members on
9525 @cindex static members of C@t{++} objects
9526 Print static members when displaying a C@t{++} object. The default is on.
9528 @item set print static-members off
9529 Do not print static members when displaying a C@t{++} object.
9531 @item show print static-members
9532 Show whether C@t{++} static members are printed or not.
9534 @item set print pascal_static-members
9535 @itemx set print pascal_static-members on
9536 @cindex static members of Pascal objects
9537 @cindex Pascal objects, static members display
9538 Print static members when displaying a Pascal object. The default is on.
9540 @item set print pascal_static-members off
9541 Do not print static members when displaying a Pascal object.
9543 @item show print pascal_static-members
9544 Show whether Pascal static members are printed or not.
9546 @c These don't work with HP ANSI C++ yet.
9547 @item set print vtbl
9548 @itemx set print vtbl on
9549 @cindex pretty print C@t{++} virtual function tables
9550 @cindex virtual functions (C@t{++}) display
9551 @cindex VTBL display
9552 Pretty print C@t{++} virtual function tables. The default is off.
9553 (The @code{vtbl} commands do not work on programs compiled with the HP
9554 ANSI C@t{++} compiler (@code{aCC}).)
9556 @item set print vtbl off
9557 Do not pretty print C@t{++} virtual function tables.
9559 @item show print vtbl
9560 Show whether C@t{++} virtual function tables are pretty printed, or not.
9563 @node Pretty Printing
9564 @section Pretty Printing
9566 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9567 Python code. It greatly simplifies the display of complex objects. This
9568 mechanism works for both MI and the CLI.
9571 * Pretty-Printer Introduction:: Introduction to pretty-printers
9572 * Pretty-Printer Example:: An example pretty-printer
9573 * Pretty-Printer Commands:: Pretty-printer commands
9576 @node Pretty-Printer Introduction
9577 @subsection Pretty-Printer Introduction
9579 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9580 registered for the value. If there is then @value{GDBN} invokes the
9581 pretty-printer to print the value. Otherwise the value is printed normally.
9583 Pretty-printers are normally named. This makes them easy to manage.
9584 The @samp{info pretty-printer} command will list all the installed
9585 pretty-printers with their names.
9586 If a pretty-printer can handle multiple data types, then its
9587 @dfn{subprinters} are the printers for the individual data types.
9588 Each such subprinter has its own name.
9589 The format of the name is @var{printer-name};@var{subprinter-name}.
9591 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9592 Typically they are automatically loaded and registered when the corresponding
9593 debug information is loaded, thus making them available without having to
9594 do anything special.
9596 There are three places where a pretty-printer can be registered.
9600 Pretty-printers registered globally are available when debugging
9604 Pretty-printers registered with a program space are available only
9605 when debugging that program.
9606 @xref{Progspaces In Python}, for more details on program spaces in Python.
9609 Pretty-printers registered with an objfile are loaded and unloaded
9610 with the corresponding objfile (e.g., shared library).
9611 @xref{Objfiles In Python}, for more details on objfiles in Python.
9614 @xref{Selecting Pretty-Printers}, for further information on how
9615 pretty-printers are selected,
9617 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9620 @node Pretty-Printer Example
9621 @subsection Pretty-Printer Example
9623 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9626 (@value{GDBP}) print s
9628 static npos = 4294967295,
9630 <std::allocator<char>> = @{
9631 <__gnu_cxx::new_allocator<char>> = @{
9632 <No data fields>@}, <No data fields>
9634 members of std::basic_string<char, std::char_traits<char>,
9635 std::allocator<char> >::_Alloc_hider:
9636 _M_p = 0x804a014 "abcd"
9641 With a pretty-printer for @code{std::string} only the contents are printed:
9644 (@value{GDBP}) print s
9648 @node Pretty-Printer Commands
9649 @subsection Pretty-Printer Commands
9650 @cindex pretty-printer commands
9653 @kindex info pretty-printer
9654 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9655 Print the list of installed pretty-printers.
9656 This includes disabled pretty-printers, which are marked as such.
9658 @var{object-regexp} is a regular expression matching the objects
9659 whose pretty-printers to list.
9660 Objects can be @code{global}, the program space's file
9661 (@pxref{Progspaces In Python}),
9662 and the object files within that program space (@pxref{Objfiles In Python}).
9663 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9664 looks up a printer from these three objects.
9666 @var{name-regexp} is a regular expression matching the name of the printers
9669 @kindex disable pretty-printer
9670 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9671 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9672 A disabled pretty-printer is not forgotten, it may be enabled again later.
9674 @kindex enable pretty-printer
9675 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9676 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9681 Suppose we have three pretty-printers installed: one from library1.so
9682 named @code{foo} that prints objects of type @code{foo}, and
9683 another from library2.so named @code{bar} that prints two types of objects,
9684 @code{bar1} and @code{bar2}.
9687 (gdb) info pretty-printer
9694 (gdb) info pretty-printer library2
9699 (gdb) disable pretty-printer library1
9701 2 of 3 printers enabled
9702 (gdb) info pretty-printer
9709 (gdb) disable pretty-printer library2 bar:bar1
9711 1 of 3 printers enabled
9712 (gdb) info pretty-printer library2
9719 (gdb) disable pretty-printer library2 bar
9721 0 of 3 printers enabled
9722 (gdb) info pretty-printer library2
9731 Note that for @code{bar} the entire printer can be disabled,
9732 as can each individual subprinter.
9735 @section Value History
9737 @cindex value history
9738 @cindex history of values printed by @value{GDBN}
9739 Values printed by the @code{print} command are saved in the @value{GDBN}
9740 @dfn{value history}. This allows you to refer to them in other expressions.
9741 Values are kept until the symbol table is re-read or discarded
9742 (for example with the @code{file} or @code{symbol-file} commands).
9743 When the symbol table changes, the value history is discarded,
9744 since the values may contain pointers back to the types defined in the
9749 @cindex history number
9750 The values printed are given @dfn{history numbers} by which you can
9751 refer to them. These are successive integers starting with one.
9752 @code{print} shows you the history number assigned to a value by
9753 printing @samp{$@var{num} = } before the value; here @var{num} is the
9756 To refer to any previous value, use @samp{$} followed by the value's
9757 history number. The way @code{print} labels its output is designed to
9758 remind you of this. Just @code{$} refers to the most recent value in
9759 the history, and @code{$$} refers to the value before that.
9760 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9761 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9762 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9764 For example, suppose you have just printed a pointer to a structure and
9765 want to see the contents of the structure. It suffices to type
9771 If you have a chain of structures where the component @code{next} points
9772 to the next one, you can print the contents of the next one with this:
9779 You can print successive links in the chain by repeating this
9780 command---which you can do by just typing @key{RET}.
9782 Note that the history records values, not expressions. If the value of
9783 @code{x} is 4 and you type these commands:
9791 then the value recorded in the value history by the @code{print} command
9792 remains 4 even though the value of @code{x} has changed.
9797 Print the last ten values in the value history, with their item numbers.
9798 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9799 values} does not change the history.
9801 @item show values @var{n}
9802 Print ten history values centered on history item number @var{n}.
9805 Print ten history values just after the values last printed. If no more
9806 values are available, @code{show values +} produces no display.
9809 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9810 same effect as @samp{show values +}.
9812 @node Convenience Vars
9813 @section Convenience Variables
9815 @cindex convenience variables
9816 @cindex user-defined variables
9817 @value{GDBN} provides @dfn{convenience variables} that you can use within
9818 @value{GDBN} to hold on to a value and refer to it later. These variables
9819 exist entirely within @value{GDBN}; they are not part of your program, and
9820 setting a convenience variable has no direct effect on further execution
9821 of your program. That is why you can use them freely.
9823 Convenience variables are prefixed with @samp{$}. Any name preceded by
9824 @samp{$} can be used for a convenience variable, unless it is one of
9825 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9826 (Value history references, in contrast, are @emph{numbers} preceded
9827 by @samp{$}. @xref{Value History, ,Value History}.)
9829 You can save a value in a convenience variable with an assignment
9830 expression, just as you would set a variable in your program.
9834 set $foo = *object_ptr
9838 would save in @code{$foo} the value contained in the object pointed to by
9841 Using a convenience variable for the first time creates it, but its
9842 value is @code{void} until you assign a new value. You can alter the
9843 value with another assignment at any time.
9845 Convenience variables have no fixed types. You can assign a convenience
9846 variable any type of value, including structures and arrays, even if
9847 that variable already has a value of a different type. The convenience
9848 variable, when used as an expression, has the type of its current value.
9851 @kindex show convenience
9852 @cindex show all user variables and functions
9853 @item show convenience
9854 Print a list of convenience variables used so far, and their values,
9855 as well as a list of the convenience functions.
9856 Abbreviated @code{show conv}.
9858 @kindex init-if-undefined
9859 @cindex convenience variables, initializing
9860 @item init-if-undefined $@var{variable} = @var{expression}
9861 Set a convenience variable if it has not already been set. This is useful
9862 for user-defined commands that keep some state. It is similar, in concept,
9863 to using local static variables with initializers in C (except that
9864 convenience variables are global). It can also be used to allow users to
9865 override default values used in a command script.
9867 If the variable is already defined then the expression is not evaluated so
9868 any side-effects do not occur.
9871 One of the ways to use a convenience variable is as a counter to be
9872 incremented or a pointer to be advanced. For example, to print
9873 a field from successive elements of an array of structures:
9877 print bar[$i++]->contents
9881 Repeat that command by typing @key{RET}.
9883 Some convenience variables are created automatically by @value{GDBN} and given
9884 values likely to be useful.
9887 @vindex $_@r{, convenience variable}
9889 The variable @code{$_} is automatically set by the @code{x} command to
9890 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9891 commands which provide a default address for @code{x} to examine also
9892 set @code{$_} to that address; these commands include @code{info line}
9893 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9894 except when set by the @code{x} command, in which case it is a pointer
9895 to the type of @code{$__}.
9897 @vindex $__@r{, convenience variable}
9899 The variable @code{$__} is automatically set by the @code{x} command
9900 to the value found in the last address examined. Its type is chosen
9901 to match the format in which the data was printed.
9904 @vindex $_exitcode@r{, convenience variable}
9905 When the program being debugged terminates normally, @value{GDBN}
9906 automatically sets this variable to the exit code of the program, and
9907 resets @code{$_exitsignal} to @code{void}.
9910 @vindex $_exitsignal@r{, convenience variable}
9911 When the program being debugged dies due to an uncaught signal,
9912 @value{GDBN} automatically sets this variable to that signal's number,
9913 and resets @code{$_exitcode} to @code{void}.
9915 To distinguish between whether the program being debugged has exited
9916 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9917 @code{$_exitsignal} is not @code{void}), the convenience function
9918 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9919 Functions}). For example, considering the following source code:
9925 main (int argc, char *argv[])
9932 A valid way of telling whether the program being debugged has exited
9933 or signalled would be:
9936 (@value{GDBP}) define has_exited_or_signalled
9937 Type commands for definition of ``has_exited_or_signalled''.
9938 End with a line saying just ``end''.
9939 >if $_isvoid ($_exitsignal)
9940 >echo The program has exited\n
9942 >echo The program has signalled\n
9948 Program terminated with signal SIGALRM, Alarm clock.
9949 The program no longer exists.
9950 (@value{GDBP}) has_exited_or_signalled
9951 The program has signalled
9954 As can be seen, @value{GDBN} correctly informs that the program being
9955 debugged has signalled, since it calls @code{raise} and raises a
9956 @code{SIGALRM} signal. If the program being debugged had not called
9957 @code{raise}, then @value{GDBN} would report a normal exit:
9960 (@value{GDBP}) has_exited_or_signalled
9961 The program has exited
9965 The variable @code{$_exception} is set to the exception object being
9966 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9969 @itemx $_probe_arg0@dots{}$_probe_arg11
9970 Arguments to a static probe. @xref{Static Probe Points}.
9973 @vindex $_sdata@r{, inspect, convenience variable}
9974 The variable @code{$_sdata} contains extra collected static tracepoint
9975 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9976 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9977 if extra static tracepoint data has not been collected.
9980 @vindex $_siginfo@r{, convenience variable}
9981 The variable @code{$_siginfo} contains extra signal information
9982 (@pxref{extra signal information}). Note that @code{$_siginfo}
9983 could be empty, if the application has not yet received any signals.
9984 For example, it will be empty before you execute the @code{run} command.
9987 @vindex $_tlb@r{, convenience variable}
9988 The variable @code{$_tlb} is automatically set when debugging
9989 applications running on MS-Windows in native mode or connected to
9990 gdbserver that supports the @code{qGetTIBAddr} request.
9991 @xref{General Query Packets}.
9992 This variable contains the address of the thread information block.
9996 On HP-UX systems, if you refer to a function or variable name that
9997 begins with a dollar sign, @value{GDBN} searches for a user or system
9998 name first, before it searches for a convenience variable.
10000 @node Convenience Funs
10001 @section Convenience Functions
10003 @cindex convenience functions
10004 @value{GDBN} also supplies some @dfn{convenience functions}. These
10005 have a syntax similar to convenience variables. A convenience
10006 function can be used in an expression just like an ordinary function;
10007 however, a convenience function is implemented internally to
10010 These functions do not require @value{GDBN} to be configured with
10011 @code{Python} support, which means that they are always available.
10015 @item $_isvoid (@var{expr})
10016 @findex $_isvoid@r{, convenience function}
10017 Return one if the expression @var{expr} is @code{void}. Otherwise it
10020 A @code{void} expression is an expression where the type of the result
10021 is @code{void}. For example, you can examine a convenience variable
10022 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10026 (@value{GDBP}) print $_exitcode
10028 (@value{GDBP}) print $_isvoid ($_exitcode)
10031 Starting program: ./a.out
10032 [Inferior 1 (process 29572) exited normally]
10033 (@value{GDBP}) print $_exitcode
10035 (@value{GDBP}) print $_isvoid ($_exitcode)
10039 In the example above, we used @code{$_isvoid} to check whether
10040 @code{$_exitcode} is @code{void} before and after the execution of the
10041 program being debugged. Before the execution there is no exit code to
10042 be examined, therefore @code{$_exitcode} is @code{void}. After the
10043 execution the program being debugged returned zero, therefore
10044 @code{$_exitcode} is zero, which means that it is not @code{void}
10047 The @code{void} expression can also be a call of a function from the
10048 program being debugged. For example, given the following function:
10057 The result of calling it inside @value{GDBN} is @code{void}:
10060 (@value{GDBP}) print foo ()
10062 (@value{GDBP}) print $_isvoid (foo ())
10064 (@value{GDBP}) set $v = foo ()
10065 (@value{GDBP}) print $v
10067 (@value{GDBP}) print $_isvoid ($v)
10073 These functions require @value{GDBN} to be configured with
10074 @code{Python} support.
10078 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10079 @findex $_memeq@r{, convenience function}
10080 Returns one if the @var{length} bytes at the addresses given by
10081 @var{buf1} and @var{buf2} are equal.
10082 Otherwise it returns zero.
10084 @item $_regex(@var{str}, @var{regex})
10085 @findex $_regex@r{, convenience function}
10086 Returns one if the string @var{str} matches the regular expression
10087 @var{regex}. Otherwise it returns zero.
10088 The syntax of the regular expression is that specified by @code{Python}'s
10089 regular expression support.
10091 @item $_streq(@var{str1}, @var{str2})
10092 @findex $_streq@r{, convenience function}
10093 Returns one if the strings @var{str1} and @var{str2} are equal.
10094 Otherwise it returns zero.
10096 @item $_strlen(@var{str})
10097 @findex $_strlen@r{, convenience function}
10098 Returns the length of string @var{str}.
10102 @value{GDBN} provides the ability to list and get help on
10103 convenience functions.
10106 @item help function
10107 @kindex help function
10108 @cindex show all convenience functions
10109 Print a list of all convenience functions.
10116 You can refer to machine register contents, in expressions, as variables
10117 with names starting with @samp{$}. The names of registers are different
10118 for each machine; use @code{info registers} to see the names used on
10122 @kindex info registers
10123 @item info registers
10124 Print the names and values of all registers except floating-point
10125 and vector registers (in the selected stack frame).
10127 @kindex info all-registers
10128 @cindex floating point registers
10129 @item info all-registers
10130 Print the names and values of all registers, including floating-point
10131 and vector registers (in the selected stack frame).
10133 @item info registers @var{regname} @dots{}
10134 Print the @dfn{relativized} value of each specified register @var{regname}.
10135 As discussed in detail below, register values are normally relative to
10136 the selected stack frame. The @var{regname} may be any register name valid on
10137 the machine you are using, with or without the initial @samp{$}.
10140 @cindex stack pointer register
10141 @cindex program counter register
10142 @cindex process status register
10143 @cindex frame pointer register
10144 @cindex standard registers
10145 @value{GDBN} has four ``standard'' register names that are available (in
10146 expressions) on most machines---whenever they do not conflict with an
10147 architecture's canonical mnemonics for registers. The register names
10148 @code{$pc} and @code{$sp} are used for the program counter register and
10149 the stack pointer. @code{$fp} is used for a register that contains a
10150 pointer to the current stack frame, and @code{$ps} is used for a
10151 register that contains the processor status. For example,
10152 you could print the program counter in hex with
10159 or print the instruction to be executed next with
10166 or add four to the stack pointer@footnote{This is a way of removing
10167 one word from the stack, on machines where stacks grow downward in
10168 memory (most machines, nowadays). This assumes that the innermost
10169 stack frame is selected; setting @code{$sp} is not allowed when other
10170 stack frames are selected. To pop entire frames off the stack,
10171 regardless of machine architecture, use @code{return};
10172 see @ref{Returning, ,Returning from a Function}.} with
10178 Whenever possible, these four standard register names are available on
10179 your machine even though the machine has different canonical mnemonics,
10180 so long as there is no conflict. The @code{info registers} command
10181 shows the canonical names. For example, on the SPARC, @code{info
10182 registers} displays the processor status register as @code{$psr} but you
10183 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10184 is an alias for the @sc{eflags} register.
10186 @value{GDBN} always considers the contents of an ordinary register as an
10187 integer when the register is examined in this way. Some machines have
10188 special registers which can hold nothing but floating point; these
10189 registers are considered to have floating point values. There is no way
10190 to refer to the contents of an ordinary register as floating point value
10191 (although you can @emph{print} it as a floating point value with
10192 @samp{print/f $@var{regname}}).
10194 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10195 means that the data format in which the register contents are saved by
10196 the operating system is not the same one that your program normally
10197 sees. For example, the registers of the 68881 floating point
10198 coprocessor are always saved in ``extended'' (raw) format, but all C
10199 programs expect to work with ``double'' (virtual) format. In such
10200 cases, @value{GDBN} normally works with the virtual format only (the format
10201 that makes sense for your program), but the @code{info registers} command
10202 prints the data in both formats.
10204 @cindex SSE registers (x86)
10205 @cindex MMX registers (x86)
10206 Some machines have special registers whose contents can be interpreted
10207 in several different ways. For example, modern x86-based machines
10208 have SSE and MMX registers that can hold several values packed
10209 together in several different formats. @value{GDBN} refers to such
10210 registers in @code{struct} notation:
10213 (@value{GDBP}) print $xmm1
10215 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10216 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10217 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10218 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10219 v4_int32 = @{0, 20657912, 11, 13@},
10220 v2_int64 = @{88725056443645952, 55834574859@},
10221 uint128 = 0x0000000d0000000b013b36f800000000
10226 To set values of such registers, you need to tell @value{GDBN} which
10227 view of the register you wish to change, as if you were assigning
10228 value to a @code{struct} member:
10231 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10234 Normally, register values are relative to the selected stack frame
10235 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10236 value that the register would contain if all stack frames farther in
10237 were exited and their saved registers restored. In order to see the
10238 true contents of hardware registers, you must select the innermost
10239 frame (with @samp{frame 0}).
10241 @cindex caller-saved registers
10242 @cindex call-clobbered registers
10243 @cindex volatile registers
10244 @cindex <not saved> values
10245 Usually ABIs reserve some registers as not needed to be saved by the
10246 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10247 registers). It may therefore not be possible for @value{GDBN} to know
10248 the value a register had before the call (in other words, in the outer
10249 frame), if the register value has since been changed by the callee.
10250 @value{GDBN} tries to deduce where the inner frame saved
10251 (``callee-saved'') registers, from the debug info, unwind info, or the
10252 machine code generated by your compiler. If some register is not
10253 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10254 its own knowledge of the ABI, or because the debug/unwind info
10255 explicitly says the register's value is undefined), @value{GDBN}
10256 displays @w{@samp{<not saved>}} as the register's value. With targets
10257 that @value{GDBN} has no knowledge of the register saving convention,
10258 if a register was not saved by the callee, then its value and location
10259 in the outer frame are assumed to be the same of the inner frame.
10260 This is usually harmless, because if the register is call-clobbered,
10261 the caller either does not care what is in the register after the
10262 call, or has code to restore the value that it does care about. Note,
10263 however, that if you change such a register in the outer frame, you
10264 may also be affecting the inner frame. Also, the more ``outer'' the
10265 frame is you're looking at, the more likely a call-clobbered
10266 register's value is to be wrong, in the sense that it doesn't actually
10267 represent the value the register had just before the call.
10269 @node Floating Point Hardware
10270 @section Floating Point Hardware
10271 @cindex floating point
10273 Depending on the configuration, @value{GDBN} may be able to give
10274 you more information about the status of the floating point hardware.
10279 Display hardware-dependent information about the floating
10280 point unit. The exact contents and layout vary depending on the
10281 floating point chip. Currently, @samp{info float} is supported on
10282 the ARM and x86 machines.
10286 @section Vector Unit
10287 @cindex vector unit
10289 Depending on the configuration, @value{GDBN} may be able to give you
10290 more information about the status of the vector unit.
10293 @kindex info vector
10295 Display information about the vector unit. The exact contents and
10296 layout vary depending on the hardware.
10299 @node OS Information
10300 @section Operating System Auxiliary Information
10301 @cindex OS information
10303 @value{GDBN} provides interfaces to useful OS facilities that can help
10304 you debug your program.
10306 @cindex auxiliary vector
10307 @cindex vector, auxiliary
10308 Some operating systems supply an @dfn{auxiliary vector} to programs at
10309 startup. This is akin to the arguments and environment that you
10310 specify for a program, but contains a system-dependent variety of
10311 binary values that tell system libraries important details about the
10312 hardware, operating system, and process. Each value's purpose is
10313 identified by an integer tag; the meanings are well-known but system-specific.
10314 Depending on the configuration and operating system facilities,
10315 @value{GDBN} may be able to show you this information. For remote
10316 targets, this functionality may further depend on the remote stub's
10317 support of the @samp{qXfer:auxv:read} packet, see
10318 @ref{qXfer auxiliary vector read}.
10323 Display the auxiliary vector of the inferior, which can be either a
10324 live process or a core dump file. @value{GDBN} prints each tag value
10325 numerically, and also shows names and text descriptions for recognized
10326 tags. Some values in the vector are numbers, some bit masks, and some
10327 pointers to strings or other data. @value{GDBN} displays each value in the
10328 most appropriate form for a recognized tag, and in hexadecimal for
10329 an unrecognized tag.
10332 On some targets, @value{GDBN} can access operating system-specific
10333 information and show it to you. The types of information available
10334 will differ depending on the type of operating system running on the
10335 target. The mechanism used to fetch the data is described in
10336 @ref{Operating System Information}. For remote targets, this
10337 functionality depends on the remote stub's support of the
10338 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10342 @item info os @var{infotype}
10344 Display OS information of the requested type.
10346 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10348 @anchor{linux info os infotypes}
10350 @kindex info os processes
10352 Display the list of processes on the target. For each process,
10353 @value{GDBN} prints the process identifier, the name of the user, the
10354 command corresponding to the process, and the list of processor cores
10355 that the process is currently running on. (To understand what these
10356 properties mean, for this and the following info types, please consult
10357 the general @sc{gnu}/Linux documentation.)
10359 @kindex info os procgroups
10361 Display the list of process groups on the target. For each process,
10362 @value{GDBN} prints the identifier of the process group that it belongs
10363 to, the command corresponding to the process group leader, the process
10364 identifier, and the command line of the process. The list is sorted
10365 first by the process group identifier, then by the process identifier,
10366 so that processes belonging to the same process group are grouped together
10367 and the process group leader is listed first.
10369 @kindex info os threads
10371 Display the list of threads running on the target. For each thread,
10372 @value{GDBN} prints the identifier of the process that the thread
10373 belongs to, the command of the process, the thread identifier, and the
10374 processor core that it is currently running on. The main thread of a
10375 process is not listed.
10377 @kindex info os files
10379 Display the list of open file descriptors on the target. For each
10380 file descriptor, @value{GDBN} prints the identifier of the process
10381 owning the descriptor, the command of the owning process, the value
10382 of the descriptor, and the target of the descriptor.
10384 @kindex info os sockets
10386 Display the list of Internet-domain sockets on the target. For each
10387 socket, @value{GDBN} prints the address and port of the local and
10388 remote endpoints, the current state of the connection, the creator of
10389 the socket, the IP address family of the socket, and the type of the
10392 @kindex info os shm
10394 Display the list of all System V shared-memory regions on the target.
10395 For each shared-memory region, @value{GDBN} prints the region key,
10396 the shared-memory identifier, the access permissions, the size of the
10397 region, the process that created the region, the process that last
10398 attached to or detached from the region, the current number of live
10399 attaches to the region, and the times at which the region was last
10400 attached to, detach from, and changed.
10402 @kindex info os semaphores
10404 Display the list of all System V semaphore sets on the target. For each
10405 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10406 set identifier, the access permissions, the number of semaphores in the
10407 set, the user and group of the owner and creator of the semaphore set,
10408 and the times at which the semaphore set was operated upon and changed.
10410 @kindex info os msg
10412 Display the list of all System V message queues on the target. For each
10413 message queue, @value{GDBN} prints the message queue key, the message
10414 queue identifier, the access permissions, the current number of bytes
10415 on the queue, the current number of messages on the queue, the processes
10416 that last sent and received a message on the queue, the user and group
10417 of the owner and creator of the message queue, the times at which a
10418 message was last sent and received on the queue, and the time at which
10419 the message queue was last changed.
10421 @kindex info os modules
10423 Display the list of all loaded kernel modules on the target. For each
10424 module, @value{GDBN} prints the module name, the size of the module in
10425 bytes, the number of times the module is used, the dependencies of the
10426 module, the status of the module, and the address of the loaded module
10431 If @var{infotype} is omitted, then list the possible values for
10432 @var{infotype} and the kind of OS information available for each
10433 @var{infotype}. If the target does not return a list of possible
10434 types, this command will report an error.
10437 @node Memory Region Attributes
10438 @section Memory Region Attributes
10439 @cindex memory region attributes
10441 @dfn{Memory region attributes} allow you to describe special handling
10442 required by regions of your target's memory. @value{GDBN} uses
10443 attributes to determine whether to allow certain types of memory
10444 accesses; whether to use specific width accesses; and whether to cache
10445 target memory. By default the description of memory regions is
10446 fetched from the target (if the current target supports this), but the
10447 user can override the fetched regions.
10449 Defined memory regions can be individually enabled and disabled. When a
10450 memory region is disabled, @value{GDBN} uses the default attributes when
10451 accessing memory in that region. Similarly, if no memory regions have
10452 been defined, @value{GDBN} uses the default attributes when accessing
10455 When a memory region is defined, it is given a number to identify it;
10456 to enable, disable, or remove a memory region, you specify that number.
10460 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10461 Define a memory region bounded by @var{lower} and @var{upper} with
10462 attributes @var{attributes}@dots{}, and add it to the list of regions
10463 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10464 case: it is treated as the target's maximum memory address.
10465 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10468 Discard any user changes to the memory regions and use target-supplied
10469 regions, if available, or no regions if the target does not support.
10472 @item delete mem @var{nums}@dots{}
10473 Remove memory regions @var{nums}@dots{} from the list of regions
10474 monitored by @value{GDBN}.
10476 @kindex disable mem
10477 @item disable mem @var{nums}@dots{}
10478 Disable monitoring of memory regions @var{nums}@dots{}.
10479 A disabled memory region is not forgotten.
10480 It may be enabled again later.
10483 @item enable mem @var{nums}@dots{}
10484 Enable monitoring of memory regions @var{nums}@dots{}.
10488 Print a table of all defined memory regions, with the following columns
10492 @item Memory Region Number
10493 @item Enabled or Disabled.
10494 Enabled memory regions are marked with @samp{y}.
10495 Disabled memory regions are marked with @samp{n}.
10498 The address defining the inclusive lower bound of the memory region.
10501 The address defining the exclusive upper bound of the memory region.
10504 The list of attributes set for this memory region.
10509 @subsection Attributes
10511 @subsubsection Memory Access Mode
10512 The access mode attributes set whether @value{GDBN} may make read or
10513 write accesses to a memory region.
10515 While these attributes prevent @value{GDBN} from performing invalid
10516 memory accesses, they do nothing to prevent the target system, I/O DMA,
10517 etc.@: from accessing memory.
10521 Memory is read only.
10523 Memory is write only.
10525 Memory is read/write. This is the default.
10528 @subsubsection Memory Access Size
10529 The access size attribute tells @value{GDBN} to use specific sized
10530 accesses in the memory region. Often memory mapped device registers
10531 require specific sized accesses. If no access size attribute is
10532 specified, @value{GDBN} may use accesses of any size.
10536 Use 8 bit memory accesses.
10538 Use 16 bit memory accesses.
10540 Use 32 bit memory accesses.
10542 Use 64 bit memory accesses.
10545 @c @subsubsection Hardware/Software Breakpoints
10546 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10547 @c will use hardware or software breakpoints for the internal breakpoints
10548 @c used by the step, next, finish, until, etc. commands.
10552 @c Always use hardware breakpoints
10553 @c @item swbreak (default)
10556 @subsubsection Data Cache
10557 The data cache attributes set whether @value{GDBN} will cache target
10558 memory. While this generally improves performance by reducing debug
10559 protocol overhead, it can lead to incorrect results because @value{GDBN}
10560 does not know about volatile variables or memory mapped device
10565 Enable @value{GDBN} to cache target memory.
10567 Disable @value{GDBN} from caching target memory. This is the default.
10570 @subsection Memory Access Checking
10571 @value{GDBN} can be instructed to refuse accesses to memory that is
10572 not explicitly described. This can be useful if accessing such
10573 regions has undesired effects for a specific target, or to provide
10574 better error checking. The following commands control this behaviour.
10577 @kindex set mem inaccessible-by-default
10578 @item set mem inaccessible-by-default [on|off]
10579 If @code{on} is specified, make @value{GDBN} treat memory not
10580 explicitly described by the memory ranges as non-existent and refuse accesses
10581 to such memory. The checks are only performed if there's at least one
10582 memory range defined. If @code{off} is specified, make @value{GDBN}
10583 treat the memory not explicitly described by the memory ranges as RAM.
10584 The default value is @code{on}.
10585 @kindex show mem inaccessible-by-default
10586 @item show mem inaccessible-by-default
10587 Show the current handling of accesses to unknown memory.
10591 @c @subsubsection Memory Write Verification
10592 @c The memory write verification attributes set whether @value{GDBN}
10593 @c will re-reads data after each write to verify the write was successful.
10597 @c @item noverify (default)
10600 @node Dump/Restore Files
10601 @section Copy Between Memory and a File
10602 @cindex dump/restore files
10603 @cindex append data to a file
10604 @cindex dump data to a file
10605 @cindex restore data from a file
10607 You can use the commands @code{dump}, @code{append}, and
10608 @code{restore} to copy data between target memory and a file. The
10609 @code{dump} and @code{append} commands write data to a file, and the
10610 @code{restore} command reads data from a file back into the inferior's
10611 memory. Files may be in binary, Motorola S-record, Intel hex, or
10612 Tektronix Hex format; however, @value{GDBN} can only append to binary
10618 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10619 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10620 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10621 or the value of @var{expr}, to @var{filename} in the given format.
10623 The @var{format} parameter may be any one of:
10630 Motorola S-record format.
10632 Tektronix Hex format.
10635 @value{GDBN} uses the same definitions of these formats as the
10636 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10637 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10641 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10642 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10643 Append the contents of memory from @var{start_addr} to @var{end_addr},
10644 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10645 (@value{GDBN} can only append data to files in raw binary form.)
10648 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10649 Restore the contents of file @var{filename} into memory. The
10650 @code{restore} command can automatically recognize any known @sc{bfd}
10651 file format, except for raw binary. To restore a raw binary file you
10652 must specify the optional keyword @code{binary} after the filename.
10654 If @var{bias} is non-zero, its value will be added to the addresses
10655 contained in the file. Binary files always start at address zero, so
10656 they will be restored at address @var{bias}. Other bfd files have
10657 a built-in location; they will be restored at offset @var{bias}
10658 from that location.
10660 If @var{start} and/or @var{end} are non-zero, then only data between
10661 file offset @var{start} and file offset @var{end} will be restored.
10662 These offsets are relative to the addresses in the file, before
10663 the @var{bias} argument is applied.
10667 @node Core File Generation
10668 @section How to Produce a Core File from Your Program
10669 @cindex dump core from inferior
10671 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10672 image of a running process and its process status (register values
10673 etc.). Its primary use is post-mortem debugging of a program that
10674 crashed while it ran outside a debugger. A program that crashes
10675 automatically produces a core file, unless this feature is disabled by
10676 the user. @xref{Files}, for information on invoking @value{GDBN} in
10677 the post-mortem debugging mode.
10679 Occasionally, you may wish to produce a core file of the program you
10680 are debugging in order to preserve a snapshot of its state.
10681 @value{GDBN} has a special command for that.
10685 @kindex generate-core-file
10686 @item generate-core-file [@var{file}]
10687 @itemx gcore [@var{file}]
10688 Produce a core dump of the inferior process. The optional argument
10689 @var{file} specifies the file name where to put the core dump. If not
10690 specified, the file name defaults to @file{core.@var{pid}}, where
10691 @var{pid} is the inferior process ID.
10693 Note that this command is implemented only for some systems (as of
10694 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10697 @node Character Sets
10698 @section Character Sets
10699 @cindex character sets
10701 @cindex translating between character sets
10702 @cindex host character set
10703 @cindex target character set
10705 If the program you are debugging uses a different character set to
10706 represent characters and strings than the one @value{GDBN} uses itself,
10707 @value{GDBN} can automatically translate between the character sets for
10708 you. The character set @value{GDBN} uses we call the @dfn{host
10709 character set}; the one the inferior program uses we call the
10710 @dfn{target character set}.
10712 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10713 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10714 remote protocol (@pxref{Remote Debugging}) to debug a program
10715 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10716 then the host character set is Latin-1, and the target character set is
10717 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10718 target-charset EBCDIC-US}, then @value{GDBN} translates between
10719 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10720 character and string literals in expressions.
10722 @value{GDBN} has no way to automatically recognize which character set
10723 the inferior program uses; you must tell it, using the @code{set
10724 target-charset} command, described below.
10726 Here are the commands for controlling @value{GDBN}'s character set
10730 @item set target-charset @var{charset}
10731 @kindex set target-charset
10732 Set the current target character set to @var{charset}. To display the
10733 list of supported target character sets, type
10734 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10736 @item set host-charset @var{charset}
10737 @kindex set host-charset
10738 Set the current host character set to @var{charset}.
10740 By default, @value{GDBN} uses a host character set appropriate to the
10741 system it is running on; you can override that default using the
10742 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10743 automatically determine the appropriate host character set. In this
10744 case, @value{GDBN} uses @samp{UTF-8}.
10746 @value{GDBN} can only use certain character sets as its host character
10747 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10748 @value{GDBN} will list the host character sets it supports.
10750 @item set charset @var{charset}
10751 @kindex set charset
10752 Set the current host and target character sets to @var{charset}. As
10753 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10754 @value{GDBN} will list the names of the character sets that can be used
10755 for both host and target.
10758 @kindex show charset
10759 Show the names of the current host and target character sets.
10761 @item show host-charset
10762 @kindex show host-charset
10763 Show the name of the current host character set.
10765 @item show target-charset
10766 @kindex show target-charset
10767 Show the name of the current target character set.
10769 @item set target-wide-charset @var{charset}
10770 @kindex set target-wide-charset
10771 Set the current target's wide character set to @var{charset}. This is
10772 the character set used by the target's @code{wchar_t} type. To
10773 display the list of supported wide character sets, type
10774 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10776 @item show target-wide-charset
10777 @kindex show target-wide-charset
10778 Show the name of the current target's wide character set.
10781 Here is an example of @value{GDBN}'s character set support in action.
10782 Assume that the following source code has been placed in the file
10783 @file{charset-test.c}:
10789 = @{72, 101, 108, 108, 111, 44, 32, 119,
10790 111, 114, 108, 100, 33, 10, 0@};
10791 char ibm1047_hello[]
10792 = @{200, 133, 147, 147, 150, 107, 64, 166,
10793 150, 153, 147, 132, 90, 37, 0@};
10797 printf ("Hello, world!\n");
10801 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10802 containing the string @samp{Hello, world!} followed by a newline,
10803 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10805 We compile the program, and invoke the debugger on it:
10808 $ gcc -g charset-test.c -o charset-test
10809 $ gdb -nw charset-test
10810 GNU gdb 2001-12-19-cvs
10811 Copyright 2001 Free Software Foundation, Inc.
10816 We can use the @code{show charset} command to see what character sets
10817 @value{GDBN} is currently using to interpret and display characters and
10821 (@value{GDBP}) show charset
10822 The current host and target character set is `ISO-8859-1'.
10826 For the sake of printing this manual, let's use @sc{ascii} as our
10827 initial character set:
10829 (@value{GDBP}) set charset ASCII
10830 (@value{GDBP}) show charset
10831 The current host and target character set is `ASCII'.
10835 Let's assume that @sc{ascii} is indeed the correct character set for our
10836 host system --- in other words, let's assume that if @value{GDBN} prints
10837 characters using the @sc{ascii} character set, our terminal will display
10838 them properly. Since our current target character set is also
10839 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10842 (@value{GDBP}) print ascii_hello
10843 $1 = 0x401698 "Hello, world!\n"
10844 (@value{GDBP}) print ascii_hello[0]
10849 @value{GDBN} uses the target character set for character and string
10850 literals you use in expressions:
10853 (@value{GDBP}) print '+'
10858 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10861 @value{GDBN} relies on the user to tell it which character set the
10862 target program uses. If we print @code{ibm1047_hello} while our target
10863 character set is still @sc{ascii}, we get jibberish:
10866 (@value{GDBP}) print ibm1047_hello
10867 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10868 (@value{GDBP}) print ibm1047_hello[0]
10873 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10874 @value{GDBN} tells us the character sets it supports:
10877 (@value{GDBP}) set target-charset
10878 ASCII EBCDIC-US IBM1047 ISO-8859-1
10879 (@value{GDBP}) set target-charset
10882 We can select @sc{ibm1047} as our target character set, and examine the
10883 program's strings again. Now the @sc{ascii} string is wrong, but
10884 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10885 target character set, @sc{ibm1047}, to the host character set,
10886 @sc{ascii}, and they display correctly:
10889 (@value{GDBP}) set target-charset IBM1047
10890 (@value{GDBP}) show charset
10891 The current host character set is `ASCII'.
10892 The current target character set is `IBM1047'.
10893 (@value{GDBP}) print ascii_hello
10894 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10895 (@value{GDBP}) print ascii_hello[0]
10897 (@value{GDBP}) print ibm1047_hello
10898 $8 = 0x4016a8 "Hello, world!\n"
10899 (@value{GDBP}) print ibm1047_hello[0]
10904 As above, @value{GDBN} uses the target character set for character and
10905 string literals you use in expressions:
10908 (@value{GDBP}) print '+'
10913 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10916 @node Caching Target Data
10917 @section Caching Data of Targets
10918 @cindex caching data of targets
10920 @value{GDBN} caches data exchanged between the debugger and a target.
10921 Each cache is associated with the address space of the inferior.
10922 @xref{Inferiors and Programs}, about inferior and address space.
10923 Such caching generally improves performance in remote debugging
10924 (@pxref{Remote Debugging}), because it reduces the overhead of the
10925 remote protocol by bundling memory reads and writes into large chunks.
10926 Unfortunately, simply caching everything would lead to incorrect results,
10927 since @value{GDBN} does not necessarily know anything about volatile
10928 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10929 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10931 Therefore, by default, @value{GDBN} only caches data
10932 known to be on the stack@footnote{In non-stop mode, it is moderately
10933 rare for a running thread to modify the stack of a stopped thread
10934 in a way that would interfere with a backtrace, and caching of
10935 stack reads provides a significant speed up of remote backtraces.} or
10936 in the code segment.
10937 Other regions of memory can be explicitly marked as
10938 cacheable; @pxref{Memory Region Attributes}.
10941 @kindex set remotecache
10942 @item set remotecache on
10943 @itemx set remotecache off
10944 This option no longer does anything; it exists for compatibility
10947 @kindex show remotecache
10948 @item show remotecache
10949 Show the current state of the obsolete remotecache flag.
10951 @kindex set stack-cache
10952 @item set stack-cache on
10953 @itemx set stack-cache off
10954 Enable or disable caching of stack accesses. When @code{on}, use
10955 caching. By default, this option is @code{on}.
10957 @kindex show stack-cache
10958 @item show stack-cache
10959 Show the current state of data caching for memory accesses.
10961 @kindex set code-cache
10962 @item set code-cache on
10963 @itemx set code-cache off
10964 Enable or disable caching of code segment accesses. When @code{on},
10965 use caching. By default, this option is @code{on}. This improves
10966 performance of disassembly in remote debugging.
10968 @kindex show code-cache
10969 @item show code-cache
10970 Show the current state of target memory cache for code segment
10973 @kindex info dcache
10974 @item info dcache @r{[}line@r{]}
10975 Print the information about the performance of data cache of the
10976 current inferior's address space. The information displayed
10977 includes the dcache width and depth, and for each cache line, its
10978 number, address, and how many times it was referenced. This
10979 command is useful for debugging the data cache operation.
10981 If a line number is specified, the contents of that line will be
10984 @item set dcache size @var{size}
10985 @cindex dcache size
10986 @kindex set dcache size
10987 Set maximum number of entries in dcache (dcache depth above).
10989 @item set dcache line-size @var{line-size}
10990 @cindex dcache line-size
10991 @kindex set dcache line-size
10992 Set number of bytes each dcache entry caches (dcache width above).
10993 Must be a power of 2.
10995 @item show dcache size
10996 @kindex show dcache size
10997 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10999 @item show dcache line-size
11000 @kindex show dcache line-size
11001 Show default size of dcache lines.
11005 @node Searching Memory
11006 @section Search Memory
11007 @cindex searching memory
11009 Memory can be searched for a particular sequence of bytes with the
11010 @code{find} command.
11014 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11015 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11016 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11017 etc. The search begins at address @var{start_addr} and continues for either
11018 @var{len} bytes or through to @var{end_addr} inclusive.
11021 @var{s} and @var{n} are optional parameters.
11022 They may be specified in either order, apart or together.
11025 @item @var{s}, search query size
11026 The size of each search query value.
11032 halfwords (two bytes)
11036 giant words (eight bytes)
11039 All values are interpreted in the current language.
11040 This means, for example, that if the current source language is C/C@t{++}
11041 then searching for the string ``hello'' includes the trailing '\0'.
11043 If the value size is not specified, it is taken from the
11044 value's type in the current language.
11045 This is useful when one wants to specify the search
11046 pattern as a mixture of types.
11047 Note that this means, for example, that in the case of C-like languages
11048 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11049 which is typically four bytes.
11051 @item @var{n}, maximum number of finds
11052 The maximum number of matches to print. The default is to print all finds.
11055 You can use strings as search values. Quote them with double-quotes
11057 The string value is copied into the search pattern byte by byte,
11058 regardless of the endianness of the target and the size specification.
11060 The address of each match found is printed as well as a count of the
11061 number of matches found.
11063 The address of the last value found is stored in convenience variable
11065 A count of the number of matches is stored in @samp{$numfound}.
11067 For example, if stopped at the @code{printf} in this function:
11073 static char hello[] = "hello-hello";
11074 static struct @{ char c; short s; int i; @}
11075 __attribute__ ((packed)) mixed
11076 = @{ 'c', 0x1234, 0x87654321 @};
11077 printf ("%s\n", hello);
11082 you get during debugging:
11085 (gdb) find &hello[0], +sizeof(hello), "hello"
11086 0x804956d <hello.1620+6>
11088 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11089 0x8049567 <hello.1620>
11090 0x804956d <hello.1620+6>
11092 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11093 0x8049567 <hello.1620>
11095 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11096 0x8049560 <mixed.1625>
11098 (gdb) print $numfound
11101 $2 = (void *) 0x8049560
11104 @node Optimized Code
11105 @chapter Debugging Optimized Code
11106 @cindex optimized code, debugging
11107 @cindex debugging optimized code
11109 Almost all compilers support optimization. With optimization
11110 disabled, the compiler generates assembly code that corresponds
11111 directly to your source code, in a simplistic way. As the compiler
11112 applies more powerful optimizations, the generated assembly code
11113 diverges from your original source code. With help from debugging
11114 information generated by the compiler, @value{GDBN} can map from
11115 the running program back to constructs from your original source.
11117 @value{GDBN} is more accurate with optimization disabled. If you
11118 can recompile without optimization, it is easier to follow the
11119 progress of your program during debugging. But, there are many cases
11120 where you may need to debug an optimized version.
11122 When you debug a program compiled with @samp{-g -O}, remember that the
11123 optimizer has rearranged your code; the debugger shows you what is
11124 really there. Do not be too surprised when the execution path does not
11125 exactly match your source file! An extreme example: if you define a
11126 variable, but never use it, @value{GDBN} never sees that
11127 variable---because the compiler optimizes it out of existence.
11129 Some things do not work as well with @samp{-g -O} as with just
11130 @samp{-g}, particularly on machines with instruction scheduling. If in
11131 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11132 please report it to us as a bug (including a test case!).
11133 @xref{Variables}, for more information about debugging optimized code.
11136 * Inline Functions:: How @value{GDBN} presents inlining
11137 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11140 @node Inline Functions
11141 @section Inline Functions
11142 @cindex inline functions, debugging
11144 @dfn{Inlining} is an optimization that inserts a copy of the function
11145 body directly at each call site, instead of jumping to a shared
11146 routine. @value{GDBN} displays inlined functions just like
11147 non-inlined functions. They appear in backtraces. You can view their
11148 arguments and local variables, step into them with @code{step}, skip
11149 them with @code{next}, and escape from them with @code{finish}.
11150 You can check whether a function was inlined by using the
11151 @code{info frame} command.
11153 For @value{GDBN} to support inlined functions, the compiler must
11154 record information about inlining in the debug information ---
11155 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11156 other compilers do also. @value{GDBN} only supports inlined functions
11157 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11158 do not emit two required attributes (@samp{DW_AT_call_file} and
11159 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11160 function calls with earlier versions of @value{NGCC}. It instead
11161 displays the arguments and local variables of inlined functions as
11162 local variables in the caller.
11164 The body of an inlined function is directly included at its call site;
11165 unlike a non-inlined function, there are no instructions devoted to
11166 the call. @value{GDBN} still pretends that the call site and the
11167 start of the inlined function are different instructions. Stepping to
11168 the call site shows the call site, and then stepping again shows
11169 the first line of the inlined function, even though no additional
11170 instructions are executed.
11172 This makes source-level debugging much clearer; you can see both the
11173 context of the call and then the effect of the call. Only stepping by
11174 a single instruction using @code{stepi} or @code{nexti} does not do
11175 this; single instruction steps always show the inlined body.
11177 There are some ways that @value{GDBN} does not pretend that inlined
11178 function calls are the same as normal calls:
11182 Setting breakpoints at the call site of an inlined function may not
11183 work, because the call site does not contain any code. @value{GDBN}
11184 may incorrectly move the breakpoint to the next line of the enclosing
11185 function, after the call. This limitation will be removed in a future
11186 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11187 or inside the inlined function instead.
11190 @value{GDBN} cannot locate the return value of inlined calls after
11191 using the @code{finish} command. This is a limitation of compiler-generated
11192 debugging information; after @code{finish}, you can step to the next line
11193 and print a variable where your program stored the return value.
11197 @node Tail Call Frames
11198 @section Tail Call Frames
11199 @cindex tail call frames, debugging
11201 Function @code{B} can call function @code{C} in its very last statement. In
11202 unoptimized compilation the call of @code{C} is immediately followed by return
11203 instruction at the end of @code{B} code. Optimizing compiler may replace the
11204 call and return in function @code{B} into one jump to function @code{C}
11205 instead. Such use of a jump instruction is called @dfn{tail call}.
11207 During execution of function @code{C}, there will be no indication in the
11208 function call stack frames that it was tail-called from @code{B}. If function
11209 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11210 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11211 some cases @value{GDBN} can determine that @code{C} was tail-called from
11212 @code{B}, and it will then create fictitious call frame for that, with the
11213 return address set up as if @code{B} called @code{C} normally.
11215 This functionality is currently supported only by DWARF 2 debugging format and
11216 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11217 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11220 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11221 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11225 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11227 Stack level 1, frame at 0x7fffffffda30:
11228 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11229 tail call frame, caller of frame at 0x7fffffffda30
11230 source language c++.
11231 Arglist at unknown address.
11232 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11235 The detection of all the possible code path executions can find them ambiguous.
11236 There is no execution history stored (possible @ref{Reverse Execution} is never
11237 used for this purpose) and the last known caller could have reached the known
11238 callee by multiple different jump sequences. In such case @value{GDBN} still
11239 tries to show at least all the unambiguous top tail callers and all the
11240 unambiguous bottom tail calees, if any.
11243 @anchor{set debug entry-values}
11244 @item set debug entry-values
11245 @kindex set debug entry-values
11246 When set to on, enables printing of analysis messages for both frame argument
11247 values at function entry and tail calls. It will show all the possible valid
11248 tail calls code paths it has considered. It will also print the intersection
11249 of them with the final unambiguous (possibly partial or even empty) code path
11252 @item show debug entry-values
11253 @kindex show debug entry-values
11254 Show the current state of analysis messages printing for both frame argument
11255 values at function entry and tail calls.
11258 The analysis messages for tail calls can for example show why the virtual tail
11259 call frame for function @code{c} has not been recognized (due to the indirect
11260 reference by variable @code{x}):
11263 static void __attribute__((noinline, noclone)) c (void);
11264 void (*x) (void) = c;
11265 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11266 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11267 int main (void) @{ x (); return 0; @}
11269 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11270 DW_TAG_GNU_call_site 0x40039a in main
11272 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11275 #1 0x000000000040039a in main () at t.c:5
11278 Another possibility is an ambiguous virtual tail call frames resolution:
11282 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11283 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11284 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11285 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11286 static void __attribute__((noinline, noclone)) b (void)
11287 @{ if (i) c (); else e (); @}
11288 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11289 int main (void) @{ a (); return 0; @}
11291 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11292 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11293 tailcall: reduced: 0x4004d2(a) |
11296 #1 0x00000000004004d2 in a () at t.c:8
11297 #2 0x0000000000400395 in main () at t.c:9
11300 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11301 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11303 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11304 @ifset HAVE_MAKEINFO_CLICK
11305 @set ARROW @click{}
11306 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11307 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11309 @ifclear HAVE_MAKEINFO_CLICK
11311 @set CALLSEQ1B @value{CALLSEQ1A}
11312 @set CALLSEQ2B @value{CALLSEQ2A}
11315 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11316 The code can have possible execution paths @value{CALLSEQ1B} or
11317 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11319 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11320 has found. It then finds another possible calling sequcen - that one is
11321 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11322 printed as the @code{reduced:} calling sequence. That one could have many
11323 futher @code{compare:} and @code{reduced:} statements as long as there remain
11324 any non-ambiguous sequence entries.
11326 For the frame of function @code{b} in both cases there are different possible
11327 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11328 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11329 therefore this one is displayed to the user while the ambiguous frames are
11332 There can be also reasons why printing of frame argument values at function
11337 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11338 static void __attribute__((noinline, noclone)) a (int i);
11339 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11340 static void __attribute__((noinline, noclone)) a (int i)
11341 @{ if (i) b (i - 1); else c (0); @}
11342 int main (void) @{ a (5); return 0; @}
11345 #0 c (i=i@@entry=0) at t.c:2
11346 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11347 function "a" at 0x400420 can call itself via tail calls
11348 i=<optimized out>) at t.c:6
11349 #2 0x000000000040036e in main () at t.c:7
11352 @value{GDBN} cannot find out from the inferior state if and how many times did
11353 function @code{a} call itself (via function @code{b}) as these calls would be
11354 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11355 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11356 prints @code{<optimized out>} instead.
11359 @chapter C Preprocessor Macros
11361 Some languages, such as C and C@t{++}, provide a way to define and invoke
11362 ``preprocessor macros'' which expand into strings of tokens.
11363 @value{GDBN} can evaluate expressions containing macro invocations, show
11364 the result of macro expansion, and show a macro's definition, including
11365 where it was defined.
11367 You may need to compile your program specially to provide @value{GDBN}
11368 with information about preprocessor macros. Most compilers do not
11369 include macros in their debugging information, even when you compile
11370 with the @option{-g} flag. @xref{Compilation}.
11372 A program may define a macro at one point, remove that definition later,
11373 and then provide a different definition after that. Thus, at different
11374 points in the program, a macro may have different definitions, or have
11375 no definition at all. If there is a current stack frame, @value{GDBN}
11376 uses the macros in scope at that frame's source code line. Otherwise,
11377 @value{GDBN} uses the macros in scope at the current listing location;
11380 Whenever @value{GDBN} evaluates an expression, it always expands any
11381 macro invocations present in the expression. @value{GDBN} also provides
11382 the following commands for working with macros explicitly.
11386 @kindex macro expand
11387 @cindex macro expansion, showing the results of preprocessor
11388 @cindex preprocessor macro expansion, showing the results of
11389 @cindex expanding preprocessor macros
11390 @item macro expand @var{expression}
11391 @itemx macro exp @var{expression}
11392 Show the results of expanding all preprocessor macro invocations in
11393 @var{expression}. Since @value{GDBN} simply expands macros, but does
11394 not parse the result, @var{expression} need not be a valid expression;
11395 it can be any string of tokens.
11398 @item macro expand-once @var{expression}
11399 @itemx macro exp1 @var{expression}
11400 @cindex expand macro once
11401 @i{(This command is not yet implemented.)} Show the results of
11402 expanding those preprocessor macro invocations that appear explicitly in
11403 @var{expression}. Macro invocations appearing in that expansion are
11404 left unchanged. This command allows you to see the effect of a
11405 particular macro more clearly, without being confused by further
11406 expansions. Since @value{GDBN} simply expands macros, but does not
11407 parse the result, @var{expression} need not be a valid expression; it
11408 can be any string of tokens.
11411 @cindex macro definition, showing
11412 @cindex definition of a macro, showing
11413 @cindex macros, from debug info
11414 @item info macro [-a|-all] [--] @var{macro}
11415 Show the current definition or all definitions of the named @var{macro},
11416 and describe the source location or compiler command-line where that
11417 definition was established. The optional double dash is to signify the end of
11418 argument processing and the beginning of @var{macro} for non C-like macros where
11419 the macro may begin with a hyphen.
11421 @kindex info macros
11422 @item info macros @var{linespec}
11423 Show all macro definitions that are in effect at the location specified
11424 by @var{linespec}, and describe the source location or compiler
11425 command-line where those definitions were established.
11427 @kindex macro define
11428 @cindex user-defined macros
11429 @cindex defining macros interactively
11430 @cindex macros, user-defined
11431 @item macro define @var{macro} @var{replacement-list}
11432 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11433 Introduce a definition for a preprocessor macro named @var{macro},
11434 invocations of which are replaced by the tokens given in
11435 @var{replacement-list}. The first form of this command defines an
11436 ``object-like'' macro, which takes no arguments; the second form
11437 defines a ``function-like'' macro, which takes the arguments given in
11440 A definition introduced by this command is in scope in every
11441 expression evaluated in @value{GDBN}, until it is removed with the
11442 @code{macro undef} command, described below. The definition overrides
11443 all definitions for @var{macro} present in the program being debugged,
11444 as well as any previous user-supplied definition.
11446 @kindex macro undef
11447 @item macro undef @var{macro}
11448 Remove any user-supplied definition for the macro named @var{macro}.
11449 This command only affects definitions provided with the @code{macro
11450 define} command, described above; it cannot remove definitions present
11451 in the program being debugged.
11455 List all the macros defined using the @code{macro define} command.
11458 @cindex macros, example of debugging with
11459 Here is a transcript showing the above commands in action. First, we
11460 show our source files:
11465 #include "sample.h"
11468 #define ADD(x) (M + x)
11473 printf ("Hello, world!\n");
11475 printf ("We're so creative.\n");
11477 printf ("Goodbye, world!\n");
11484 Now, we compile the program using the @sc{gnu} C compiler,
11485 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11486 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11487 and @option{-gdwarf-4}; we recommend always choosing the most recent
11488 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11489 includes information about preprocessor macros in the debugging
11493 $ gcc -gdwarf-2 -g3 sample.c -o sample
11497 Now, we start @value{GDBN} on our sample program:
11501 GNU gdb 2002-05-06-cvs
11502 Copyright 2002 Free Software Foundation, Inc.
11503 GDB is free software, @dots{}
11507 We can expand macros and examine their definitions, even when the
11508 program is not running. @value{GDBN} uses the current listing position
11509 to decide which macro definitions are in scope:
11512 (@value{GDBP}) list main
11515 5 #define ADD(x) (M + x)
11520 10 printf ("Hello, world!\n");
11522 12 printf ("We're so creative.\n");
11523 (@value{GDBP}) info macro ADD
11524 Defined at /home/jimb/gdb/macros/play/sample.c:5
11525 #define ADD(x) (M + x)
11526 (@value{GDBP}) info macro Q
11527 Defined at /home/jimb/gdb/macros/play/sample.h:1
11528 included at /home/jimb/gdb/macros/play/sample.c:2
11530 (@value{GDBP}) macro expand ADD(1)
11531 expands to: (42 + 1)
11532 (@value{GDBP}) macro expand-once ADD(1)
11533 expands to: once (M + 1)
11537 In the example above, note that @code{macro expand-once} expands only
11538 the macro invocation explicit in the original text --- the invocation of
11539 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11540 which was introduced by @code{ADD}.
11542 Once the program is running, @value{GDBN} uses the macro definitions in
11543 force at the source line of the current stack frame:
11546 (@value{GDBP}) break main
11547 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11549 Starting program: /home/jimb/gdb/macros/play/sample
11551 Breakpoint 1, main () at sample.c:10
11552 10 printf ("Hello, world!\n");
11556 At line 10, the definition of the macro @code{N} at line 9 is in force:
11559 (@value{GDBP}) info macro N
11560 Defined at /home/jimb/gdb/macros/play/sample.c:9
11562 (@value{GDBP}) macro expand N Q M
11563 expands to: 28 < 42
11564 (@value{GDBP}) print N Q M
11569 As we step over directives that remove @code{N}'s definition, and then
11570 give it a new definition, @value{GDBN} finds the definition (or lack
11571 thereof) in force at each point:
11574 (@value{GDBP}) next
11576 12 printf ("We're so creative.\n");
11577 (@value{GDBP}) info macro N
11578 The symbol `N' has no definition as a C/C++ preprocessor macro
11579 at /home/jimb/gdb/macros/play/sample.c:12
11580 (@value{GDBP}) next
11582 14 printf ("Goodbye, world!\n");
11583 (@value{GDBP}) info macro N
11584 Defined at /home/jimb/gdb/macros/play/sample.c:13
11586 (@value{GDBP}) macro expand N Q M
11587 expands to: 1729 < 42
11588 (@value{GDBP}) print N Q M
11593 In addition to source files, macros can be defined on the compilation command
11594 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11595 such a way, @value{GDBN} displays the location of their definition as line zero
11596 of the source file submitted to the compiler.
11599 (@value{GDBP}) info macro __STDC__
11600 Defined at /home/jimb/gdb/macros/play/sample.c:0
11607 @chapter Tracepoints
11608 @c This chapter is based on the documentation written by Michael
11609 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11611 @cindex tracepoints
11612 In some applications, it is not feasible for the debugger to interrupt
11613 the program's execution long enough for the developer to learn
11614 anything helpful about its behavior. If the program's correctness
11615 depends on its real-time behavior, delays introduced by a debugger
11616 might cause the program to change its behavior drastically, or perhaps
11617 fail, even when the code itself is correct. It is useful to be able
11618 to observe the program's behavior without interrupting it.
11620 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11621 specify locations in the program, called @dfn{tracepoints}, and
11622 arbitrary expressions to evaluate when those tracepoints are reached.
11623 Later, using the @code{tfind} command, you can examine the values
11624 those expressions had when the program hit the tracepoints. The
11625 expressions may also denote objects in memory---structures or arrays,
11626 for example---whose values @value{GDBN} should record; while visiting
11627 a particular tracepoint, you may inspect those objects as if they were
11628 in memory at that moment. However, because @value{GDBN} records these
11629 values without interacting with you, it can do so quickly and
11630 unobtrusively, hopefully not disturbing the program's behavior.
11632 The tracepoint facility is currently available only for remote
11633 targets. @xref{Targets}. In addition, your remote target must know
11634 how to collect trace data. This functionality is implemented in the
11635 remote stub; however, none of the stubs distributed with @value{GDBN}
11636 support tracepoints as of this writing. The format of the remote
11637 packets used to implement tracepoints are described in @ref{Tracepoint
11640 It is also possible to get trace data from a file, in a manner reminiscent
11641 of corefiles; you specify the filename, and use @code{tfind} to search
11642 through the file. @xref{Trace Files}, for more details.
11644 This chapter describes the tracepoint commands and features.
11647 * Set Tracepoints::
11648 * Analyze Collected Data::
11649 * Tracepoint Variables::
11653 @node Set Tracepoints
11654 @section Commands to Set Tracepoints
11656 Before running such a @dfn{trace experiment}, an arbitrary number of
11657 tracepoints can be set. A tracepoint is actually a special type of
11658 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11659 standard breakpoint commands. For instance, as with breakpoints,
11660 tracepoint numbers are successive integers starting from one, and many
11661 of the commands associated with tracepoints take the tracepoint number
11662 as their argument, to identify which tracepoint to work on.
11664 For each tracepoint, you can specify, in advance, some arbitrary set
11665 of data that you want the target to collect in the trace buffer when
11666 it hits that tracepoint. The collected data can include registers,
11667 local variables, or global data. Later, you can use @value{GDBN}
11668 commands to examine the values these data had at the time the
11669 tracepoint was hit.
11671 Tracepoints do not support every breakpoint feature. Ignore counts on
11672 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11673 commands when they are hit. Tracepoints may not be thread-specific
11676 @cindex fast tracepoints
11677 Some targets may support @dfn{fast tracepoints}, which are inserted in
11678 a different way (such as with a jump instead of a trap), that is
11679 faster but possibly restricted in where they may be installed.
11681 @cindex static tracepoints
11682 @cindex markers, static tracepoints
11683 @cindex probing markers, static tracepoints
11684 Regular and fast tracepoints are dynamic tracing facilities, meaning
11685 that they can be used to insert tracepoints at (almost) any location
11686 in the target. Some targets may also support controlling @dfn{static
11687 tracepoints} from @value{GDBN}. With static tracing, a set of
11688 instrumentation points, also known as @dfn{markers}, are embedded in
11689 the target program, and can be activated or deactivated by name or
11690 address. These are usually placed at locations which facilitate
11691 investigating what the target is actually doing. @value{GDBN}'s
11692 support for static tracing includes being able to list instrumentation
11693 points, and attach them with @value{GDBN} defined high level
11694 tracepoints that expose the whole range of convenience of
11695 @value{GDBN}'s tracepoints support. Namely, support for collecting
11696 registers values and values of global or local (to the instrumentation
11697 point) variables; tracepoint conditions and trace state variables.
11698 The act of installing a @value{GDBN} static tracepoint on an
11699 instrumentation point, or marker, is referred to as @dfn{probing} a
11700 static tracepoint marker.
11702 @code{gdbserver} supports tracepoints on some target systems.
11703 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11705 This section describes commands to set tracepoints and associated
11706 conditions and actions.
11709 * Create and Delete Tracepoints::
11710 * Enable and Disable Tracepoints::
11711 * Tracepoint Passcounts::
11712 * Tracepoint Conditions::
11713 * Trace State Variables::
11714 * Tracepoint Actions::
11715 * Listing Tracepoints::
11716 * Listing Static Tracepoint Markers::
11717 * Starting and Stopping Trace Experiments::
11718 * Tracepoint Restrictions::
11721 @node Create and Delete Tracepoints
11722 @subsection Create and Delete Tracepoints
11725 @cindex set tracepoint
11727 @item trace @var{location}
11728 The @code{trace} command is very similar to the @code{break} command.
11729 Its argument @var{location} can be a source line, a function name, or
11730 an address in the target program. @xref{Specify Location}. The
11731 @code{trace} command defines a tracepoint, which is a point in the
11732 target program where the debugger will briefly stop, collect some
11733 data, and then allow the program to continue. Setting a tracepoint or
11734 changing its actions takes effect immediately if the remote stub
11735 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11737 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11738 these changes don't take effect until the next @code{tstart}
11739 command, and once a trace experiment is running, further changes will
11740 not have any effect until the next trace experiment starts. In addition,
11741 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11742 address is not yet resolved. (This is similar to pending breakpoints.)
11743 Pending tracepoints are not downloaded to the target and not installed
11744 until they are resolved. The resolution of pending tracepoints requires
11745 @value{GDBN} support---when debugging with the remote target, and
11746 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11747 tracing}), pending tracepoints can not be resolved (and downloaded to
11748 the remote stub) while @value{GDBN} is disconnected.
11750 Here are some examples of using the @code{trace} command:
11753 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11755 (@value{GDBP}) @b{trace +2} // 2 lines forward
11757 (@value{GDBP}) @b{trace my_function} // first source line of function
11759 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11761 (@value{GDBP}) @b{trace *0x2117c4} // an address
11765 You can abbreviate @code{trace} as @code{tr}.
11767 @item trace @var{location} if @var{cond}
11768 Set a tracepoint with condition @var{cond}; evaluate the expression
11769 @var{cond} each time the tracepoint is reached, and collect data only
11770 if the value is nonzero---that is, if @var{cond} evaluates as true.
11771 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11772 information on tracepoint conditions.
11774 @item ftrace @var{location} [ if @var{cond} ]
11775 @cindex set fast tracepoint
11776 @cindex fast tracepoints, setting
11778 The @code{ftrace} command sets a fast tracepoint. For targets that
11779 support them, fast tracepoints will use a more efficient but possibly
11780 less general technique to trigger data collection, such as a jump
11781 instruction instead of a trap, or some sort of hardware support. It
11782 may not be possible to create a fast tracepoint at the desired
11783 location, in which case the command will exit with an explanatory
11786 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11789 On 32-bit x86-architecture systems, fast tracepoints normally need to
11790 be placed at an instruction that is 5 bytes or longer, but can be
11791 placed at 4-byte instructions if the low 64K of memory of the target
11792 program is available to install trampolines. Some Unix-type systems,
11793 such as @sc{gnu}/Linux, exclude low addresses from the program's
11794 address space; but for instance with the Linux kernel it is possible
11795 to let @value{GDBN} use this area by doing a @command{sysctl} command
11796 to set the @code{mmap_min_addr} kernel parameter, as in
11799 sudo sysctl -w vm.mmap_min_addr=32768
11803 which sets the low address to 32K, which leaves plenty of room for
11804 trampolines. The minimum address should be set to a page boundary.
11806 @item strace @var{location} [ if @var{cond} ]
11807 @cindex set static tracepoint
11808 @cindex static tracepoints, setting
11809 @cindex probe static tracepoint marker
11811 The @code{strace} command sets a static tracepoint. For targets that
11812 support it, setting a static tracepoint probes a static
11813 instrumentation point, or marker, found at @var{location}. It may not
11814 be possible to set a static tracepoint at the desired location, in
11815 which case the command will exit with an explanatory message.
11817 @value{GDBN} handles arguments to @code{strace} exactly as for
11818 @code{trace}, with the addition that the user can also specify
11819 @code{-m @var{marker}} as @var{location}. This probes the marker
11820 identified by the @var{marker} string identifier. This identifier
11821 depends on the static tracepoint backend library your program is
11822 using. You can find all the marker identifiers in the @samp{ID} field
11823 of the @code{info static-tracepoint-markers} command output.
11824 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11825 Markers}. For example, in the following small program using the UST
11831 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11836 the marker id is composed of joining the first two arguments to the
11837 @code{trace_mark} call with a slash, which translates to:
11840 (@value{GDBP}) info static-tracepoint-markers
11841 Cnt Enb ID Address What
11842 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11848 so you may probe the marker above with:
11851 (@value{GDBP}) strace -m ust/bar33
11854 Static tracepoints accept an extra collect action --- @code{collect
11855 $_sdata}. This collects arbitrary user data passed in the probe point
11856 call to the tracing library. In the UST example above, you'll see
11857 that the third argument to @code{trace_mark} is a printf-like format
11858 string. The user data is then the result of running that formating
11859 string against the following arguments. Note that @code{info
11860 static-tracepoint-markers} command output lists that format string in
11861 the @samp{Data:} field.
11863 You can inspect this data when analyzing the trace buffer, by printing
11864 the $_sdata variable like any other variable available to
11865 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11868 @cindex last tracepoint number
11869 @cindex recent tracepoint number
11870 @cindex tracepoint number
11871 The convenience variable @code{$tpnum} records the tracepoint number
11872 of the most recently set tracepoint.
11874 @kindex delete tracepoint
11875 @cindex tracepoint deletion
11876 @item delete tracepoint @r{[}@var{num}@r{]}
11877 Permanently delete one or more tracepoints. With no argument, the
11878 default is to delete all tracepoints. Note that the regular
11879 @code{delete} command can remove tracepoints also.
11884 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11886 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11890 You can abbreviate this command as @code{del tr}.
11893 @node Enable and Disable Tracepoints
11894 @subsection Enable and Disable Tracepoints
11896 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11899 @kindex disable tracepoint
11900 @item disable tracepoint @r{[}@var{num}@r{]}
11901 Disable tracepoint @var{num}, or all tracepoints if no argument
11902 @var{num} is given. A disabled tracepoint will have no effect during
11903 a trace experiment, but it is not forgotten. You can re-enable
11904 a disabled tracepoint using the @code{enable tracepoint} command.
11905 If the command is issued during a trace experiment and the debug target
11906 has support for disabling tracepoints during a trace experiment, then the
11907 change will be effective immediately. Otherwise, it will be applied to the
11908 next trace experiment.
11910 @kindex enable tracepoint
11911 @item enable tracepoint @r{[}@var{num}@r{]}
11912 Enable tracepoint @var{num}, or all tracepoints. If this command is
11913 issued during a trace experiment and the debug target supports enabling
11914 tracepoints during a trace experiment, then the enabled tracepoints will
11915 become effective immediately. Otherwise, they will become effective the
11916 next time a trace experiment is run.
11919 @node Tracepoint Passcounts
11920 @subsection Tracepoint Passcounts
11924 @cindex tracepoint pass count
11925 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11926 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11927 automatically stop a trace experiment. If a tracepoint's passcount is
11928 @var{n}, then the trace experiment will be automatically stopped on
11929 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11930 @var{num} is not specified, the @code{passcount} command sets the
11931 passcount of the most recently defined tracepoint. If no passcount is
11932 given, the trace experiment will run until stopped explicitly by the
11938 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11939 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11941 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11942 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11943 (@value{GDBP}) @b{trace foo}
11944 (@value{GDBP}) @b{pass 3}
11945 (@value{GDBP}) @b{trace bar}
11946 (@value{GDBP}) @b{pass 2}
11947 (@value{GDBP}) @b{trace baz}
11948 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11949 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11950 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11951 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11955 @node Tracepoint Conditions
11956 @subsection Tracepoint Conditions
11957 @cindex conditional tracepoints
11958 @cindex tracepoint conditions
11960 The simplest sort of tracepoint collects data every time your program
11961 reaches a specified place. You can also specify a @dfn{condition} for
11962 a tracepoint. A condition is just a Boolean expression in your
11963 programming language (@pxref{Expressions, ,Expressions}). A
11964 tracepoint with a condition evaluates the expression each time your
11965 program reaches it, and data collection happens only if the condition
11968 Tracepoint conditions can be specified when a tracepoint is set, by
11969 using @samp{if} in the arguments to the @code{trace} command.
11970 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11971 also be set or changed at any time with the @code{condition} command,
11972 just as with breakpoints.
11974 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11975 the conditional expression itself. Instead, @value{GDBN} encodes the
11976 expression into an agent expression (@pxref{Agent Expressions})
11977 suitable for execution on the target, independently of @value{GDBN}.
11978 Global variables become raw memory locations, locals become stack
11979 accesses, and so forth.
11981 For instance, suppose you have a function that is usually called
11982 frequently, but should not be called after an error has occurred. You
11983 could use the following tracepoint command to collect data about calls
11984 of that function that happen while the error code is propagating
11985 through the program; an unconditional tracepoint could end up
11986 collecting thousands of useless trace frames that you would have to
11990 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11993 @node Trace State Variables
11994 @subsection Trace State Variables
11995 @cindex trace state variables
11997 A @dfn{trace state variable} is a special type of variable that is
11998 created and managed by target-side code. The syntax is the same as
11999 that for GDB's convenience variables (a string prefixed with ``$''),
12000 but they are stored on the target. They must be created explicitly,
12001 using a @code{tvariable} command. They are always 64-bit signed
12004 Trace state variables are remembered by @value{GDBN}, and downloaded
12005 to the target along with tracepoint information when the trace
12006 experiment starts. There are no intrinsic limits on the number of
12007 trace state variables, beyond memory limitations of the target.
12009 @cindex convenience variables, and trace state variables
12010 Although trace state variables are managed by the target, you can use
12011 them in print commands and expressions as if they were convenience
12012 variables; @value{GDBN} will get the current value from the target
12013 while the trace experiment is running. Trace state variables share
12014 the same namespace as other ``$'' variables, which means that you
12015 cannot have trace state variables with names like @code{$23} or
12016 @code{$pc}, nor can you have a trace state variable and a convenience
12017 variable with the same name.
12021 @item tvariable $@var{name} [ = @var{expression} ]
12023 The @code{tvariable} command creates a new trace state variable named
12024 @code{$@var{name}}, and optionally gives it an initial value of
12025 @var{expression}. The @var{expression} is evaluated when this command is
12026 entered; the result will be converted to an integer if possible,
12027 otherwise @value{GDBN} will report an error. A subsequent
12028 @code{tvariable} command specifying the same name does not create a
12029 variable, but instead assigns the supplied initial value to the
12030 existing variable of that name, overwriting any previous initial
12031 value. The default initial value is 0.
12033 @item info tvariables
12034 @kindex info tvariables
12035 List all the trace state variables along with their initial values.
12036 Their current values may also be displayed, if the trace experiment is
12039 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12040 @kindex delete tvariable
12041 Delete the given trace state variables, or all of them if no arguments
12046 @node Tracepoint Actions
12047 @subsection Tracepoint Action Lists
12051 @cindex tracepoint actions
12052 @item actions @r{[}@var{num}@r{]}
12053 This command will prompt for a list of actions to be taken when the
12054 tracepoint is hit. If the tracepoint number @var{num} is not
12055 specified, this command sets the actions for the one that was most
12056 recently defined (so that you can define a tracepoint and then say
12057 @code{actions} without bothering about its number). You specify the
12058 actions themselves on the following lines, one action at a time, and
12059 terminate the actions list with a line containing just @code{end}. So
12060 far, the only defined actions are @code{collect}, @code{teval}, and
12061 @code{while-stepping}.
12063 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12064 Commands, ,Breakpoint Command Lists}), except that only the defined
12065 actions are allowed; any other @value{GDBN} command is rejected.
12067 @cindex remove actions from a tracepoint
12068 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12069 and follow it immediately with @samp{end}.
12072 (@value{GDBP}) @b{collect @var{data}} // collect some data
12074 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12076 (@value{GDBP}) @b{end} // signals the end of actions.
12079 In the following example, the action list begins with @code{collect}
12080 commands indicating the things to be collected when the tracepoint is
12081 hit. Then, in order to single-step and collect additional data
12082 following the tracepoint, a @code{while-stepping} command is used,
12083 followed by the list of things to be collected after each step in a
12084 sequence of single steps. The @code{while-stepping} command is
12085 terminated by its own separate @code{end} command. Lastly, the action
12086 list is terminated by an @code{end} command.
12089 (@value{GDBP}) @b{trace foo}
12090 (@value{GDBP}) @b{actions}
12091 Enter actions for tracepoint 1, one per line:
12094 > while-stepping 12
12095 > collect $pc, arr[i]
12100 @kindex collect @r{(tracepoints)}
12101 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12102 Collect values of the given expressions when the tracepoint is hit.
12103 This command accepts a comma-separated list of any valid expressions.
12104 In addition to global, static, or local variables, the following
12105 special arguments are supported:
12109 Collect all registers.
12112 Collect all function arguments.
12115 Collect all local variables.
12118 Collect the return address. This is helpful if you want to see more
12122 Collects the number of arguments from the static probe at which the
12123 tracepoint is located.
12124 @xref{Static Probe Points}.
12126 @item $_probe_arg@var{n}
12127 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12128 from the static probe at which the tracepoint is located.
12129 @xref{Static Probe Points}.
12132 @vindex $_sdata@r{, collect}
12133 Collect static tracepoint marker specific data. Only available for
12134 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12135 Lists}. On the UST static tracepoints library backend, an
12136 instrumentation point resembles a @code{printf} function call. The
12137 tracing library is able to collect user specified data formatted to a
12138 character string using the format provided by the programmer that
12139 instrumented the program. Other backends have similar mechanisms.
12140 Here's an example of a UST marker call:
12143 const char master_name[] = "$your_name";
12144 trace_mark(channel1, marker1, "hello %s", master_name)
12147 In this case, collecting @code{$_sdata} collects the string
12148 @samp{hello $yourname}. When analyzing the trace buffer, you can
12149 inspect @samp{$_sdata} like any other variable available to
12153 You can give several consecutive @code{collect} commands, each one
12154 with a single argument, or one @code{collect} command with several
12155 arguments separated by commas; the effect is the same.
12157 The optional @var{mods} changes the usual handling of the arguments.
12158 @code{s} requests that pointers to chars be handled as strings, in
12159 particular collecting the contents of the memory being pointed at, up
12160 to the first zero. The upper bound is by default the value of the
12161 @code{print elements} variable; if @code{s} is followed by a decimal
12162 number, that is the upper bound instead. So for instance
12163 @samp{collect/s25 mystr} collects as many as 25 characters at
12166 The command @code{info scope} (@pxref{Symbols, info scope}) is
12167 particularly useful for figuring out what data to collect.
12169 @kindex teval @r{(tracepoints)}
12170 @item teval @var{expr1}, @var{expr2}, @dots{}
12171 Evaluate the given expressions when the tracepoint is hit. This
12172 command accepts a comma-separated list of expressions. The results
12173 are discarded, so this is mainly useful for assigning values to trace
12174 state variables (@pxref{Trace State Variables}) without adding those
12175 values to the trace buffer, as would be the case if the @code{collect}
12178 @kindex while-stepping @r{(tracepoints)}
12179 @item while-stepping @var{n}
12180 Perform @var{n} single-step instruction traces after the tracepoint,
12181 collecting new data after each step. The @code{while-stepping}
12182 command is followed by the list of what to collect while stepping
12183 (followed by its own @code{end} command):
12186 > while-stepping 12
12187 > collect $regs, myglobal
12193 Note that @code{$pc} is not automatically collected by
12194 @code{while-stepping}; you need to explicitly collect that register if
12195 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12198 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12199 @kindex set default-collect
12200 @cindex default collection action
12201 This variable is a list of expressions to collect at each tracepoint
12202 hit. It is effectively an additional @code{collect} action prepended
12203 to every tracepoint action list. The expressions are parsed
12204 individually for each tracepoint, so for instance a variable named
12205 @code{xyz} may be interpreted as a global for one tracepoint, and a
12206 local for another, as appropriate to the tracepoint's location.
12208 @item show default-collect
12209 @kindex show default-collect
12210 Show the list of expressions that are collected by default at each
12215 @node Listing Tracepoints
12216 @subsection Listing Tracepoints
12219 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12220 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12221 @cindex information about tracepoints
12222 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12223 Display information about the tracepoint @var{num}. If you don't
12224 specify a tracepoint number, displays information about all the
12225 tracepoints defined so far. The format is similar to that used for
12226 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12227 command, simply restricting itself to tracepoints.
12229 A tracepoint's listing may include additional information specific to
12234 its passcount as given by the @code{passcount @var{n}} command
12237 the state about installed on target of each location
12241 (@value{GDBP}) @b{info trace}
12242 Num Type Disp Enb Address What
12243 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12245 collect globfoo, $regs
12250 2 tracepoint keep y <MULTIPLE>
12252 2.1 y 0x0804859c in func4 at change-loc.h:35
12253 installed on target
12254 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12255 installed on target
12256 2.3 y <PENDING> set_tracepoint
12257 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12258 not installed on target
12263 This command can be abbreviated @code{info tp}.
12266 @node Listing Static Tracepoint Markers
12267 @subsection Listing Static Tracepoint Markers
12270 @kindex info static-tracepoint-markers
12271 @cindex information about static tracepoint markers
12272 @item info static-tracepoint-markers
12273 Display information about all static tracepoint markers defined in the
12276 For each marker, the following columns are printed:
12280 An incrementing counter, output to help readability. This is not a
12283 The marker ID, as reported by the target.
12284 @item Enabled or Disabled
12285 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12286 that are not enabled.
12288 Where the marker is in your program, as a memory address.
12290 Where the marker is in the source for your program, as a file and line
12291 number. If the debug information included in the program does not
12292 allow @value{GDBN} to locate the source of the marker, this column
12293 will be left blank.
12297 In addition, the following information may be printed for each marker:
12301 User data passed to the tracing library by the marker call. In the
12302 UST backend, this is the format string passed as argument to the
12304 @item Static tracepoints probing the marker
12305 The list of static tracepoints attached to the marker.
12309 (@value{GDBP}) info static-tracepoint-markers
12310 Cnt ID Enb Address What
12311 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12312 Data: number1 %d number2 %d
12313 Probed by static tracepoints: #2
12314 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12320 @node Starting and Stopping Trace Experiments
12321 @subsection Starting and Stopping Trace Experiments
12324 @kindex tstart [ @var{notes} ]
12325 @cindex start a new trace experiment
12326 @cindex collected data discarded
12328 This command starts the trace experiment, and begins collecting data.
12329 It has the side effect of discarding all the data collected in the
12330 trace buffer during the previous trace experiment. If any arguments
12331 are supplied, they are taken as a note and stored with the trace
12332 experiment's state. The notes may be arbitrary text, and are
12333 especially useful with disconnected tracing in a multi-user context;
12334 the notes can explain what the trace is doing, supply user contact
12335 information, and so forth.
12337 @kindex tstop [ @var{notes} ]
12338 @cindex stop a running trace experiment
12340 This command stops the trace experiment. If any arguments are
12341 supplied, they are recorded with the experiment as a note. This is
12342 useful if you are stopping a trace started by someone else, for
12343 instance if the trace is interfering with the system's behavior and
12344 needs to be stopped quickly.
12346 @strong{Note}: a trace experiment and data collection may stop
12347 automatically if any tracepoint's passcount is reached
12348 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12351 @cindex status of trace data collection
12352 @cindex trace experiment, status of
12354 This command displays the status of the current trace data
12358 Here is an example of the commands we described so far:
12361 (@value{GDBP}) @b{trace gdb_c_test}
12362 (@value{GDBP}) @b{actions}
12363 Enter actions for tracepoint #1, one per line.
12364 > collect $regs,$locals,$args
12365 > while-stepping 11
12369 (@value{GDBP}) @b{tstart}
12370 [time passes @dots{}]
12371 (@value{GDBP}) @b{tstop}
12374 @anchor{disconnected tracing}
12375 @cindex disconnected tracing
12376 You can choose to continue running the trace experiment even if
12377 @value{GDBN} disconnects from the target, voluntarily or
12378 involuntarily. For commands such as @code{detach}, the debugger will
12379 ask what you want to do with the trace. But for unexpected
12380 terminations (@value{GDBN} crash, network outage), it would be
12381 unfortunate to lose hard-won trace data, so the variable
12382 @code{disconnected-tracing} lets you decide whether the trace should
12383 continue running without @value{GDBN}.
12386 @item set disconnected-tracing on
12387 @itemx set disconnected-tracing off
12388 @kindex set disconnected-tracing
12389 Choose whether a tracing run should continue to run if @value{GDBN}
12390 has disconnected from the target. Note that @code{detach} or
12391 @code{quit} will ask you directly what to do about a running trace no
12392 matter what this variable's setting, so the variable is mainly useful
12393 for handling unexpected situations, such as loss of the network.
12395 @item show disconnected-tracing
12396 @kindex show disconnected-tracing
12397 Show the current choice for disconnected tracing.
12401 When you reconnect to the target, the trace experiment may or may not
12402 still be running; it might have filled the trace buffer in the
12403 meantime, or stopped for one of the other reasons. If it is running,
12404 it will continue after reconnection.
12406 Upon reconnection, the target will upload information about the
12407 tracepoints in effect. @value{GDBN} will then compare that
12408 information to the set of tracepoints currently defined, and attempt
12409 to match them up, allowing for the possibility that the numbers may
12410 have changed due to creation and deletion in the meantime. If one of
12411 the target's tracepoints does not match any in @value{GDBN}, the
12412 debugger will create a new tracepoint, so that you have a number with
12413 which to specify that tracepoint. This matching-up process is
12414 necessarily heuristic, and it may result in useless tracepoints being
12415 created; you may simply delete them if they are of no use.
12417 @cindex circular trace buffer
12418 If your target agent supports a @dfn{circular trace buffer}, then you
12419 can run a trace experiment indefinitely without filling the trace
12420 buffer; when space runs out, the agent deletes already-collected trace
12421 frames, oldest first, until there is enough room to continue
12422 collecting. This is especially useful if your tracepoints are being
12423 hit too often, and your trace gets terminated prematurely because the
12424 buffer is full. To ask for a circular trace buffer, simply set
12425 @samp{circular-trace-buffer} to on. You can set this at any time,
12426 including during tracing; if the agent can do it, it will change
12427 buffer handling on the fly, otherwise it will not take effect until
12431 @item set circular-trace-buffer on
12432 @itemx set circular-trace-buffer off
12433 @kindex set circular-trace-buffer
12434 Choose whether a tracing run should use a linear or circular buffer
12435 for trace data. A linear buffer will not lose any trace data, but may
12436 fill up prematurely, while a circular buffer will discard old trace
12437 data, but it will have always room for the latest tracepoint hits.
12439 @item show circular-trace-buffer
12440 @kindex show circular-trace-buffer
12441 Show the current choice for the trace buffer. Note that this may not
12442 match the agent's current buffer handling, nor is it guaranteed to
12443 match the setting that might have been in effect during a past run,
12444 for instance if you are looking at frames from a trace file.
12449 @item set trace-buffer-size @var{n}
12450 @itemx set trace-buffer-size unlimited
12451 @kindex set trace-buffer-size
12452 Request that the target use a trace buffer of @var{n} bytes. Not all
12453 targets will honor the request; they may have a compiled-in size for
12454 the trace buffer, or some other limitation. Set to a value of
12455 @code{unlimited} or @code{-1} to let the target use whatever size it
12456 likes. This is also the default.
12458 @item show trace-buffer-size
12459 @kindex show trace-buffer-size
12460 Show the current requested size for the trace buffer. Note that this
12461 will only match the actual size if the target supports size-setting,
12462 and was able to handle the requested size. For instance, if the
12463 target can only change buffer size between runs, this variable will
12464 not reflect the change until the next run starts. Use @code{tstatus}
12465 to get a report of the actual buffer size.
12469 @item set trace-user @var{text}
12470 @kindex set trace-user
12472 @item show trace-user
12473 @kindex show trace-user
12475 @item set trace-notes @var{text}
12476 @kindex set trace-notes
12477 Set the trace run's notes.
12479 @item show trace-notes
12480 @kindex show trace-notes
12481 Show the trace run's notes.
12483 @item set trace-stop-notes @var{text}
12484 @kindex set trace-stop-notes
12485 Set the trace run's stop notes. The handling of the note is as for
12486 @code{tstop} arguments; the set command is convenient way to fix a
12487 stop note that is mistaken or incomplete.
12489 @item show trace-stop-notes
12490 @kindex show trace-stop-notes
12491 Show the trace run's stop notes.
12495 @node Tracepoint Restrictions
12496 @subsection Tracepoint Restrictions
12498 @cindex tracepoint restrictions
12499 There are a number of restrictions on the use of tracepoints. As
12500 described above, tracepoint data gathering occurs on the target
12501 without interaction from @value{GDBN}. Thus the full capabilities of
12502 the debugger are not available during data gathering, and then at data
12503 examination time, you will be limited by only having what was
12504 collected. The following items describe some common problems, but it
12505 is not exhaustive, and you may run into additional difficulties not
12511 Tracepoint expressions are intended to gather objects (lvalues). Thus
12512 the full flexibility of GDB's expression evaluator is not available.
12513 You cannot call functions, cast objects to aggregate types, access
12514 convenience variables or modify values (except by assignment to trace
12515 state variables). Some language features may implicitly call
12516 functions (for instance Objective-C fields with accessors), and therefore
12517 cannot be collected either.
12520 Collection of local variables, either individually or in bulk with
12521 @code{$locals} or @code{$args}, during @code{while-stepping} may
12522 behave erratically. The stepping action may enter a new scope (for
12523 instance by stepping into a function), or the location of the variable
12524 may change (for instance it is loaded into a register). The
12525 tracepoint data recorded uses the location information for the
12526 variables that is correct for the tracepoint location. When the
12527 tracepoint is created, it is not possible, in general, to determine
12528 where the steps of a @code{while-stepping} sequence will advance the
12529 program---particularly if a conditional branch is stepped.
12532 Collection of an incompletely-initialized or partially-destroyed object
12533 may result in something that @value{GDBN} cannot display, or displays
12534 in a misleading way.
12537 When @value{GDBN} displays a pointer to character it automatically
12538 dereferences the pointer to also display characters of the string
12539 being pointed to. However, collecting the pointer during tracing does
12540 not automatically collect the string. You need to explicitly
12541 dereference the pointer and provide size information if you want to
12542 collect not only the pointer, but the memory pointed to. For example,
12543 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12547 It is not possible to collect a complete stack backtrace at a
12548 tracepoint. Instead, you may collect the registers and a few hundred
12549 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12550 (adjust to use the name of the actual stack pointer register on your
12551 target architecture, and the amount of stack you wish to capture).
12552 Then the @code{backtrace} command will show a partial backtrace when
12553 using a trace frame. The number of stack frames that can be examined
12554 depends on the sizes of the frames in the collected stack. Note that
12555 if you ask for a block so large that it goes past the bottom of the
12556 stack, the target agent may report an error trying to read from an
12560 If you do not collect registers at a tracepoint, @value{GDBN} can
12561 infer that the value of @code{$pc} must be the same as the address of
12562 the tracepoint and use that when you are looking at a trace frame
12563 for that tracepoint. However, this cannot work if the tracepoint has
12564 multiple locations (for instance if it was set in a function that was
12565 inlined), or if it has a @code{while-stepping} loop. In those cases
12566 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12571 @node Analyze Collected Data
12572 @section Using the Collected Data
12574 After the tracepoint experiment ends, you use @value{GDBN} commands
12575 for examining the trace data. The basic idea is that each tracepoint
12576 collects a trace @dfn{snapshot} every time it is hit and another
12577 snapshot every time it single-steps. All these snapshots are
12578 consecutively numbered from zero and go into a buffer, and you can
12579 examine them later. The way you examine them is to @dfn{focus} on a
12580 specific trace snapshot. When the remote stub is focused on a trace
12581 snapshot, it will respond to all @value{GDBN} requests for memory and
12582 registers by reading from the buffer which belongs to that snapshot,
12583 rather than from @emph{real} memory or registers of the program being
12584 debugged. This means that @strong{all} @value{GDBN} commands
12585 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12586 behave as if we were currently debugging the program state as it was
12587 when the tracepoint occurred. Any requests for data that are not in
12588 the buffer will fail.
12591 * tfind:: How to select a trace snapshot
12592 * tdump:: How to display all data for a snapshot
12593 * save tracepoints:: How to save tracepoints for a future run
12597 @subsection @code{tfind @var{n}}
12600 @cindex select trace snapshot
12601 @cindex find trace snapshot
12602 The basic command for selecting a trace snapshot from the buffer is
12603 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12604 counting from zero. If no argument @var{n} is given, the next
12605 snapshot is selected.
12607 Here are the various forms of using the @code{tfind} command.
12611 Find the first snapshot in the buffer. This is a synonym for
12612 @code{tfind 0} (since 0 is the number of the first snapshot).
12615 Stop debugging trace snapshots, resume @emph{live} debugging.
12618 Same as @samp{tfind none}.
12621 No argument means find the next trace snapshot.
12624 Find the previous trace snapshot before the current one. This permits
12625 retracing earlier steps.
12627 @item tfind tracepoint @var{num}
12628 Find the next snapshot associated with tracepoint @var{num}. Search
12629 proceeds forward from the last examined trace snapshot. If no
12630 argument @var{num} is given, it means find the next snapshot collected
12631 for the same tracepoint as the current snapshot.
12633 @item tfind pc @var{addr}
12634 Find the next snapshot associated with the value @var{addr} of the
12635 program counter. Search proceeds forward from the last examined trace
12636 snapshot. If no argument @var{addr} is given, it means find the next
12637 snapshot with the same value of PC as the current snapshot.
12639 @item tfind outside @var{addr1}, @var{addr2}
12640 Find the next snapshot whose PC is outside the given range of
12641 addresses (exclusive).
12643 @item tfind range @var{addr1}, @var{addr2}
12644 Find the next snapshot whose PC is between @var{addr1} and
12645 @var{addr2} (inclusive).
12647 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12648 Find the next snapshot associated with the source line @var{n}. If
12649 the optional argument @var{file} is given, refer to line @var{n} in
12650 that source file. Search proceeds forward from the last examined
12651 trace snapshot. If no argument @var{n} is given, it means find the
12652 next line other than the one currently being examined; thus saying
12653 @code{tfind line} repeatedly can appear to have the same effect as
12654 stepping from line to line in a @emph{live} debugging session.
12657 The default arguments for the @code{tfind} commands are specifically
12658 designed to make it easy to scan through the trace buffer. For
12659 instance, @code{tfind} with no argument selects the next trace
12660 snapshot, and @code{tfind -} with no argument selects the previous
12661 trace snapshot. So, by giving one @code{tfind} command, and then
12662 simply hitting @key{RET} repeatedly you can examine all the trace
12663 snapshots in order. Or, by saying @code{tfind -} and then hitting
12664 @key{RET} repeatedly you can examine the snapshots in reverse order.
12665 The @code{tfind line} command with no argument selects the snapshot
12666 for the next source line executed. The @code{tfind pc} command with
12667 no argument selects the next snapshot with the same program counter
12668 (PC) as the current frame. The @code{tfind tracepoint} command with
12669 no argument selects the next trace snapshot collected by the same
12670 tracepoint as the current one.
12672 In addition to letting you scan through the trace buffer manually,
12673 these commands make it easy to construct @value{GDBN} scripts that
12674 scan through the trace buffer and print out whatever collected data
12675 you are interested in. Thus, if we want to examine the PC, FP, and SP
12676 registers from each trace frame in the buffer, we can say this:
12679 (@value{GDBP}) @b{tfind start}
12680 (@value{GDBP}) @b{while ($trace_frame != -1)}
12681 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12682 $trace_frame, $pc, $sp, $fp
12686 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12687 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12688 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12689 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12690 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12691 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12692 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12693 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12694 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12695 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12696 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12699 Or, if we want to examine the variable @code{X} at each source line in
12703 (@value{GDBP}) @b{tfind start}
12704 (@value{GDBP}) @b{while ($trace_frame != -1)}
12705 > printf "Frame %d, X == %d\n", $trace_frame, X
12715 @subsection @code{tdump}
12717 @cindex dump all data collected at tracepoint
12718 @cindex tracepoint data, display
12720 This command takes no arguments. It prints all the data collected at
12721 the current trace snapshot.
12724 (@value{GDBP}) @b{trace 444}
12725 (@value{GDBP}) @b{actions}
12726 Enter actions for tracepoint #2, one per line:
12727 > collect $regs, $locals, $args, gdb_long_test
12730 (@value{GDBP}) @b{tstart}
12732 (@value{GDBP}) @b{tfind line 444}
12733 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12735 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12737 (@value{GDBP}) @b{tdump}
12738 Data collected at tracepoint 2, trace frame 1:
12739 d0 0xc4aa0085 -995491707
12743 d4 0x71aea3d 119204413
12746 d7 0x380035 3670069
12747 a0 0x19e24a 1696330
12748 a1 0x3000668 50333288
12750 a3 0x322000 3284992
12751 a4 0x3000698 50333336
12752 a5 0x1ad3cc 1758156
12753 fp 0x30bf3c 0x30bf3c
12754 sp 0x30bf34 0x30bf34
12756 pc 0x20b2c8 0x20b2c8
12760 p = 0x20e5b4 "gdb-test"
12767 gdb_long_test = 17 '\021'
12772 @code{tdump} works by scanning the tracepoint's current collection
12773 actions and printing the value of each expression listed. So
12774 @code{tdump} can fail, if after a run, you change the tracepoint's
12775 actions to mention variables that were not collected during the run.
12777 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12778 uses the collected value of @code{$pc} to distinguish between trace
12779 frames that were collected at the tracepoint hit, and frames that were
12780 collected while stepping. This allows it to correctly choose whether
12781 to display the basic list of collections, or the collections from the
12782 body of the while-stepping loop. However, if @code{$pc} was not collected,
12783 then @code{tdump} will always attempt to dump using the basic collection
12784 list, and may fail if a while-stepping frame does not include all the
12785 same data that is collected at the tracepoint hit.
12786 @c This is getting pretty arcane, example would be good.
12788 @node save tracepoints
12789 @subsection @code{save tracepoints @var{filename}}
12790 @kindex save tracepoints
12791 @kindex save-tracepoints
12792 @cindex save tracepoints for future sessions
12794 This command saves all current tracepoint definitions together with
12795 their actions and passcounts, into a file @file{@var{filename}}
12796 suitable for use in a later debugging session. To read the saved
12797 tracepoint definitions, use the @code{source} command (@pxref{Command
12798 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12799 alias for @w{@code{save tracepoints}}
12801 @node Tracepoint Variables
12802 @section Convenience Variables for Tracepoints
12803 @cindex tracepoint variables
12804 @cindex convenience variables for tracepoints
12807 @vindex $trace_frame
12808 @item (int) $trace_frame
12809 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12810 snapshot is selected.
12812 @vindex $tracepoint
12813 @item (int) $tracepoint
12814 The tracepoint for the current trace snapshot.
12816 @vindex $trace_line
12817 @item (int) $trace_line
12818 The line number for the current trace snapshot.
12820 @vindex $trace_file
12821 @item (char []) $trace_file
12822 The source file for the current trace snapshot.
12824 @vindex $trace_func
12825 @item (char []) $trace_func
12826 The name of the function containing @code{$tracepoint}.
12829 Note: @code{$trace_file} is not suitable for use in @code{printf},
12830 use @code{output} instead.
12832 Here's a simple example of using these convenience variables for
12833 stepping through all the trace snapshots and printing some of their
12834 data. Note that these are not the same as trace state variables,
12835 which are managed by the target.
12838 (@value{GDBP}) @b{tfind start}
12840 (@value{GDBP}) @b{while $trace_frame != -1}
12841 > output $trace_file
12842 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12848 @section Using Trace Files
12849 @cindex trace files
12851 In some situations, the target running a trace experiment may no
12852 longer be available; perhaps it crashed, or the hardware was needed
12853 for a different activity. To handle these cases, you can arrange to
12854 dump the trace data into a file, and later use that file as a source
12855 of trace data, via the @code{target tfile} command.
12860 @item tsave [ -r ] @var{filename}
12861 @itemx tsave [-ctf] @var{dirname}
12862 Save the trace data to @var{filename}. By default, this command
12863 assumes that @var{filename} refers to the host filesystem, so if
12864 necessary @value{GDBN} will copy raw trace data up from the target and
12865 then save it. If the target supports it, you can also supply the
12866 optional argument @code{-r} (``remote'') to direct the target to save
12867 the data directly into @var{filename} in its own filesystem, which may be
12868 more efficient if the trace buffer is very large. (Note, however, that
12869 @code{target tfile} can only read from files accessible to the host.)
12870 By default, this command will save trace frame in tfile format.
12871 You can supply the optional argument @code{-ctf} to save date in CTF
12872 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12873 that can be shared by multiple debugging and tracing tools. Please go to
12874 @indicateurl{http://www.efficios.com/ctf} to get more information.
12876 @kindex target tfile
12880 @item target tfile @var{filename}
12881 @itemx target ctf @var{dirname}
12882 Use the file named @var{filename} or directory named @var{dirname} as
12883 a source of trace data. Commands that examine data work as they do with
12884 a live target, but it is not possible to run any new trace experiments.
12885 @code{tstatus} will report the state of the trace run at the moment
12886 the data was saved, as well as the current trace frame you are examining.
12887 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
12891 (@value{GDBP}) target ctf ctf.ctf
12892 (@value{GDBP}) tfind
12893 Found trace frame 0, tracepoint 2
12894 39 ++a; /* set tracepoint 1 here */
12895 (@value{GDBP}) tdump
12896 Data collected at tracepoint 2, trace frame 0:
12900 c = @{"123", "456", "789", "123", "456", "789"@}
12901 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12909 @chapter Debugging Programs That Use Overlays
12912 If your program is too large to fit completely in your target system's
12913 memory, you can sometimes use @dfn{overlays} to work around this
12914 problem. @value{GDBN} provides some support for debugging programs that
12918 * How Overlays Work:: A general explanation of overlays.
12919 * Overlay Commands:: Managing overlays in @value{GDBN}.
12920 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12921 mapped by asking the inferior.
12922 * Overlay Sample Program:: A sample program using overlays.
12925 @node How Overlays Work
12926 @section How Overlays Work
12927 @cindex mapped overlays
12928 @cindex unmapped overlays
12929 @cindex load address, overlay's
12930 @cindex mapped address
12931 @cindex overlay area
12933 Suppose you have a computer whose instruction address space is only 64
12934 kilobytes long, but which has much more memory which can be accessed by
12935 other means: special instructions, segment registers, or memory
12936 management hardware, for example. Suppose further that you want to
12937 adapt a program which is larger than 64 kilobytes to run on this system.
12939 One solution is to identify modules of your program which are relatively
12940 independent, and need not call each other directly; call these modules
12941 @dfn{overlays}. Separate the overlays from the main program, and place
12942 their machine code in the larger memory. Place your main program in
12943 instruction memory, but leave at least enough space there to hold the
12944 largest overlay as well.
12946 Now, to call a function located in an overlay, you must first copy that
12947 overlay's machine code from the large memory into the space set aside
12948 for it in the instruction memory, and then jump to its entry point
12951 @c NB: In the below the mapped area's size is greater or equal to the
12952 @c size of all overlays. This is intentional to remind the developer
12953 @c that overlays don't necessarily need to be the same size.
12957 Data Instruction Larger
12958 Address Space Address Space Address Space
12959 +-----------+ +-----------+ +-----------+
12961 +-----------+ +-----------+ +-----------+<-- overlay 1
12962 | program | | main | .----| overlay 1 | load address
12963 | variables | | program | | +-----------+
12964 | and heap | | | | | |
12965 +-----------+ | | | +-----------+<-- overlay 2
12966 | | +-----------+ | | | load address
12967 +-----------+ | | | .-| overlay 2 |
12969 mapped --->+-----------+ | | +-----------+
12970 address | | | | | |
12971 | overlay | <-' | | |
12972 | area | <---' +-----------+<-- overlay 3
12973 | | <---. | | load address
12974 +-----------+ `--| overlay 3 |
12981 @anchor{A code overlay}A code overlay
12985 The diagram (@pxref{A code overlay}) shows a system with separate data
12986 and instruction address spaces. To map an overlay, the program copies
12987 its code from the larger address space to the instruction address space.
12988 Since the overlays shown here all use the same mapped address, only one
12989 may be mapped at a time. For a system with a single address space for
12990 data and instructions, the diagram would be similar, except that the
12991 program variables and heap would share an address space with the main
12992 program and the overlay area.
12994 An overlay loaded into instruction memory and ready for use is called a
12995 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12996 instruction memory. An overlay not present (or only partially present)
12997 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12998 is its address in the larger memory. The mapped address is also called
12999 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13000 called the @dfn{load memory address}, or @dfn{LMA}.
13002 Unfortunately, overlays are not a completely transparent way to adapt a
13003 program to limited instruction memory. They introduce a new set of
13004 global constraints you must keep in mind as you design your program:
13009 Before calling or returning to a function in an overlay, your program
13010 must make sure that overlay is actually mapped. Otherwise, the call or
13011 return will transfer control to the right address, but in the wrong
13012 overlay, and your program will probably crash.
13015 If the process of mapping an overlay is expensive on your system, you
13016 will need to choose your overlays carefully to minimize their effect on
13017 your program's performance.
13020 The executable file you load onto your system must contain each
13021 overlay's instructions, appearing at the overlay's load address, not its
13022 mapped address. However, each overlay's instructions must be relocated
13023 and its symbols defined as if the overlay were at its mapped address.
13024 You can use GNU linker scripts to specify different load and relocation
13025 addresses for pieces of your program; see @ref{Overlay Description,,,
13026 ld.info, Using ld: the GNU linker}.
13029 The procedure for loading executable files onto your system must be able
13030 to load their contents into the larger address space as well as the
13031 instruction and data spaces.
13035 The overlay system described above is rather simple, and could be
13036 improved in many ways:
13041 If your system has suitable bank switch registers or memory management
13042 hardware, you could use those facilities to make an overlay's load area
13043 contents simply appear at their mapped address in instruction space.
13044 This would probably be faster than copying the overlay to its mapped
13045 area in the usual way.
13048 If your overlays are small enough, you could set aside more than one
13049 overlay area, and have more than one overlay mapped at a time.
13052 You can use overlays to manage data, as well as instructions. In
13053 general, data overlays are even less transparent to your design than
13054 code overlays: whereas code overlays only require care when you call or
13055 return to functions, data overlays require care every time you access
13056 the data. Also, if you change the contents of a data overlay, you
13057 must copy its contents back out to its load address before you can copy a
13058 different data overlay into the same mapped area.
13063 @node Overlay Commands
13064 @section Overlay Commands
13066 To use @value{GDBN}'s overlay support, each overlay in your program must
13067 correspond to a separate section of the executable file. The section's
13068 virtual memory address and load memory address must be the overlay's
13069 mapped and load addresses. Identifying overlays with sections allows
13070 @value{GDBN} to determine the appropriate address of a function or
13071 variable, depending on whether the overlay is mapped or not.
13073 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13074 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13079 Disable @value{GDBN}'s overlay support. When overlay support is
13080 disabled, @value{GDBN} assumes that all functions and variables are
13081 always present at their mapped addresses. By default, @value{GDBN}'s
13082 overlay support is disabled.
13084 @item overlay manual
13085 @cindex manual overlay debugging
13086 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13087 relies on you to tell it which overlays are mapped, and which are not,
13088 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13089 commands described below.
13091 @item overlay map-overlay @var{overlay}
13092 @itemx overlay map @var{overlay}
13093 @cindex map an overlay
13094 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13095 be the name of the object file section containing the overlay. When an
13096 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13097 functions and variables at their mapped addresses. @value{GDBN} assumes
13098 that any other overlays whose mapped ranges overlap that of
13099 @var{overlay} are now unmapped.
13101 @item overlay unmap-overlay @var{overlay}
13102 @itemx overlay unmap @var{overlay}
13103 @cindex unmap an overlay
13104 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13105 must be the name of the object file section containing the overlay.
13106 When an overlay is unmapped, @value{GDBN} assumes it can find the
13107 overlay's functions and variables at their load addresses.
13110 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13111 consults a data structure the overlay manager maintains in the inferior
13112 to see which overlays are mapped. For details, see @ref{Automatic
13113 Overlay Debugging}.
13115 @item overlay load-target
13116 @itemx overlay load
13117 @cindex reloading the overlay table
13118 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13119 re-reads the table @value{GDBN} automatically each time the inferior
13120 stops, so this command should only be necessary if you have changed the
13121 overlay mapping yourself using @value{GDBN}. This command is only
13122 useful when using automatic overlay debugging.
13124 @item overlay list-overlays
13125 @itemx overlay list
13126 @cindex listing mapped overlays
13127 Display a list of the overlays currently mapped, along with their mapped
13128 addresses, load addresses, and sizes.
13132 Normally, when @value{GDBN} prints a code address, it includes the name
13133 of the function the address falls in:
13136 (@value{GDBP}) print main
13137 $3 = @{int ()@} 0x11a0 <main>
13140 When overlay debugging is enabled, @value{GDBN} recognizes code in
13141 unmapped overlays, and prints the names of unmapped functions with
13142 asterisks around them. For example, if @code{foo} is a function in an
13143 unmapped overlay, @value{GDBN} prints it this way:
13146 (@value{GDBP}) overlay list
13147 No sections are mapped.
13148 (@value{GDBP}) print foo
13149 $5 = @{int (int)@} 0x100000 <*foo*>
13152 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13156 (@value{GDBP}) overlay list
13157 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13158 mapped at 0x1016 - 0x104a
13159 (@value{GDBP}) print foo
13160 $6 = @{int (int)@} 0x1016 <foo>
13163 When overlay debugging is enabled, @value{GDBN} can find the correct
13164 address for functions and variables in an overlay, whether or not the
13165 overlay is mapped. This allows most @value{GDBN} commands, like
13166 @code{break} and @code{disassemble}, to work normally, even on unmapped
13167 code. However, @value{GDBN}'s breakpoint support has some limitations:
13171 @cindex breakpoints in overlays
13172 @cindex overlays, setting breakpoints in
13173 You can set breakpoints in functions in unmapped overlays, as long as
13174 @value{GDBN} can write to the overlay at its load address.
13176 @value{GDBN} can not set hardware or simulator-based breakpoints in
13177 unmapped overlays. However, if you set a breakpoint at the end of your
13178 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13179 you are using manual overlay management), @value{GDBN} will re-set its
13180 breakpoints properly.
13184 @node Automatic Overlay Debugging
13185 @section Automatic Overlay Debugging
13186 @cindex automatic overlay debugging
13188 @value{GDBN} can automatically track which overlays are mapped and which
13189 are not, given some simple co-operation from the overlay manager in the
13190 inferior. If you enable automatic overlay debugging with the
13191 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13192 looks in the inferior's memory for certain variables describing the
13193 current state of the overlays.
13195 Here are the variables your overlay manager must define to support
13196 @value{GDBN}'s automatic overlay debugging:
13200 @item @code{_ovly_table}:
13201 This variable must be an array of the following structures:
13206 /* The overlay's mapped address. */
13209 /* The size of the overlay, in bytes. */
13210 unsigned long size;
13212 /* The overlay's load address. */
13215 /* Non-zero if the overlay is currently mapped;
13217 unsigned long mapped;
13221 @item @code{_novlys}:
13222 This variable must be a four-byte signed integer, holding the total
13223 number of elements in @code{_ovly_table}.
13227 To decide whether a particular overlay is mapped or not, @value{GDBN}
13228 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13229 @code{lma} members equal the VMA and LMA of the overlay's section in the
13230 executable file. When @value{GDBN} finds a matching entry, it consults
13231 the entry's @code{mapped} member to determine whether the overlay is
13234 In addition, your overlay manager may define a function called
13235 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13236 will silently set a breakpoint there. If the overlay manager then
13237 calls this function whenever it has changed the overlay table, this
13238 will enable @value{GDBN} to accurately keep track of which overlays
13239 are in program memory, and update any breakpoints that may be set
13240 in overlays. This will allow breakpoints to work even if the
13241 overlays are kept in ROM or other non-writable memory while they
13242 are not being executed.
13244 @node Overlay Sample Program
13245 @section Overlay Sample Program
13246 @cindex overlay example program
13248 When linking a program which uses overlays, you must place the overlays
13249 at their load addresses, while relocating them to run at their mapped
13250 addresses. To do this, you must write a linker script (@pxref{Overlay
13251 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13252 since linker scripts are specific to a particular host system, target
13253 architecture, and target memory layout, this manual cannot provide
13254 portable sample code demonstrating @value{GDBN}'s overlay support.
13256 However, the @value{GDBN} source distribution does contain an overlaid
13257 program, with linker scripts for a few systems, as part of its test
13258 suite. The program consists of the following files from
13259 @file{gdb/testsuite/gdb.base}:
13263 The main program file.
13265 A simple overlay manager, used by @file{overlays.c}.
13270 Overlay modules, loaded and used by @file{overlays.c}.
13273 Linker scripts for linking the test program on the @code{d10v-elf}
13274 and @code{m32r-elf} targets.
13277 You can build the test program using the @code{d10v-elf} GCC
13278 cross-compiler like this:
13281 $ d10v-elf-gcc -g -c overlays.c
13282 $ d10v-elf-gcc -g -c ovlymgr.c
13283 $ d10v-elf-gcc -g -c foo.c
13284 $ d10v-elf-gcc -g -c bar.c
13285 $ d10v-elf-gcc -g -c baz.c
13286 $ d10v-elf-gcc -g -c grbx.c
13287 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13288 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13291 The build process is identical for any other architecture, except that
13292 you must substitute the appropriate compiler and linker script for the
13293 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13297 @chapter Using @value{GDBN} with Different Languages
13300 Although programming languages generally have common aspects, they are
13301 rarely expressed in the same manner. For instance, in ANSI C,
13302 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13303 Modula-2, it is accomplished by @code{p^}. Values can also be
13304 represented (and displayed) differently. Hex numbers in C appear as
13305 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13307 @cindex working language
13308 Language-specific information is built into @value{GDBN} for some languages,
13309 allowing you to express operations like the above in your program's
13310 native language, and allowing @value{GDBN} to output values in a manner
13311 consistent with the syntax of your program's native language. The
13312 language you use to build expressions is called the @dfn{working
13316 * Setting:: Switching between source languages
13317 * Show:: Displaying the language
13318 * Checks:: Type and range checks
13319 * Supported Languages:: Supported languages
13320 * Unsupported Languages:: Unsupported languages
13324 @section Switching Between Source Languages
13326 There are two ways to control the working language---either have @value{GDBN}
13327 set it automatically, or select it manually yourself. You can use the
13328 @code{set language} command for either purpose. On startup, @value{GDBN}
13329 defaults to setting the language automatically. The working language is
13330 used to determine how expressions you type are interpreted, how values
13333 In addition to the working language, every source file that
13334 @value{GDBN} knows about has its own working language. For some object
13335 file formats, the compiler might indicate which language a particular
13336 source file is in. However, most of the time @value{GDBN} infers the
13337 language from the name of the file. The language of a source file
13338 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13339 show each frame appropriately for its own language. There is no way to
13340 set the language of a source file from within @value{GDBN}, but you can
13341 set the language associated with a filename extension. @xref{Show, ,
13342 Displaying the Language}.
13344 This is most commonly a problem when you use a program, such
13345 as @code{cfront} or @code{f2c}, that generates C but is written in
13346 another language. In that case, make the
13347 program use @code{#line} directives in its C output; that way
13348 @value{GDBN} will know the correct language of the source code of the original
13349 program, and will display that source code, not the generated C code.
13352 * Filenames:: Filename extensions and languages.
13353 * Manually:: Setting the working language manually
13354 * Automatically:: Having @value{GDBN} infer the source language
13358 @subsection List of Filename Extensions and Languages
13360 If a source file name ends in one of the following extensions, then
13361 @value{GDBN} infers that its language is the one indicated.
13379 C@t{++} source file
13385 Objective-C source file
13389 Fortran source file
13392 Modula-2 source file
13396 Assembler source file. This actually behaves almost like C, but
13397 @value{GDBN} does not skip over function prologues when stepping.
13400 In addition, you may set the language associated with a filename
13401 extension. @xref{Show, , Displaying the Language}.
13404 @subsection Setting the Working Language
13406 If you allow @value{GDBN} to set the language automatically,
13407 expressions are interpreted the same way in your debugging session and
13410 @kindex set language
13411 If you wish, you may set the language manually. To do this, issue the
13412 command @samp{set language @var{lang}}, where @var{lang} is the name of
13413 a language, such as
13414 @code{c} or @code{modula-2}.
13415 For a list of the supported languages, type @samp{set language}.
13417 Setting the language manually prevents @value{GDBN} from updating the working
13418 language automatically. This can lead to confusion if you try
13419 to debug a program when the working language is not the same as the
13420 source language, when an expression is acceptable to both
13421 languages---but means different things. For instance, if the current
13422 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13430 might not have the effect you intended. In C, this means to add
13431 @code{b} and @code{c} and place the result in @code{a}. The result
13432 printed would be the value of @code{a}. In Modula-2, this means to compare
13433 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13435 @node Automatically
13436 @subsection Having @value{GDBN} Infer the Source Language
13438 To have @value{GDBN} set the working language automatically, use
13439 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13440 then infers the working language. That is, when your program stops in a
13441 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13442 working language to the language recorded for the function in that
13443 frame. If the language for a frame is unknown (that is, if the function
13444 or block corresponding to the frame was defined in a source file that
13445 does not have a recognized extension), the current working language is
13446 not changed, and @value{GDBN} issues a warning.
13448 This may not seem necessary for most programs, which are written
13449 entirely in one source language. However, program modules and libraries
13450 written in one source language can be used by a main program written in
13451 a different source language. Using @samp{set language auto} in this
13452 case frees you from having to set the working language manually.
13455 @section Displaying the Language
13457 The following commands help you find out which language is the
13458 working language, and also what language source files were written in.
13461 @item show language
13462 @anchor{show language}
13463 @kindex show language
13464 Display the current working language. This is the
13465 language you can use with commands such as @code{print} to
13466 build and compute expressions that may involve variables in your program.
13469 @kindex info frame@r{, show the source language}
13470 Display the source language for this frame. This language becomes the
13471 working language if you use an identifier from this frame.
13472 @xref{Frame Info, ,Information about a Frame}, to identify the other
13473 information listed here.
13476 @kindex info source@r{, show the source language}
13477 Display the source language of this source file.
13478 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13479 information listed here.
13482 In unusual circumstances, you may have source files with extensions
13483 not in the standard list. You can then set the extension associated
13484 with a language explicitly:
13487 @item set extension-language @var{ext} @var{language}
13488 @kindex set extension-language
13489 Tell @value{GDBN} that source files with extension @var{ext} are to be
13490 assumed as written in the source language @var{language}.
13492 @item info extensions
13493 @kindex info extensions
13494 List all the filename extensions and the associated languages.
13498 @section Type and Range Checking
13500 Some languages are designed to guard you against making seemingly common
13501 errors through a series of compile- and run-time checks. These include
13502 checking the type of arguments to functions and operators and making
13503 sure mathematical overflows are caught at run time. Checks such as
13504 these help to ensure a program's correctness once it has been compiled
13505 by eliminating type mismatches and providing active checks for range
13506 errors when your program is running.
13508 By default @value{GDBN} checks for these errors according to the
13509 rules of the current source language. Although @value{GDBN} does not check
13510 the statements in your program, it can check expressions entered directly
13511 into @value{GDBN} for evaluation via the @code{print} command, for example.
13514 * Type Checking:: An overview of type checking
13515 * Range Checking:: An overview of range checking
13518 @cindex type checking
13519 @cindex checks, type
13520 @node Type Checking
13521 @subsection An Overview of Type Checking
13523 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13524 arguments to operators and functions have to be of the correct type,
13525 otherwise an error occurs. These checks prevent type mismatch
13526 errors from ever causing any run-time problems. For example,
13529 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13531 (@value{GDBP}) print obj.my_method (0)
13534 (@value{GDBP}) print obj.my_method (0x1234)
13535 Cannot resolve method klass::my_method to any overloaded instance
13538 The second example fails because in C@t{++} the integer constant
13539 @samp{0x1234} is not type-compatible with the pointer parameter type.
13541 For the expressions you use in @value{GDBN} commands, you can tell
13542 @value{GDBN} to not enforce strict type checking or
13543 to treat any mismatches as errors and abandon the expression;
13544 When type checking is disabled, @value{GDBN} successfully evaluates
13545 expressions like the second example above.
13547 Even if type checking is off, there may be other reasons
13548 related to type that prevent @value{GDBN} from evaluating an expression.
13549 For instance, @value{GDBN} does not know how to add an @code{int} and
13550 a @code{struct foo}. These particular type errors have nothing to do
13551 with the language in use and usually arise from expressions which make
13552 little sense to evaluate anyway.
13554 @value{GDBN} provides some additional commands for controlling type checking:
13556 @kindex set check type
13557 @kindex show check type
13559 @item set check type on
13560 @itemx set check type off
13561 Set strict type checking on or off. If any type mismatches occur in
13562 evaluating an expression while type checking is on, @value{GDBN} prints a
13563 message and aborts evaluation of the expression.
13565 @item show check type
13566 Show the current setting of type checking and whether @value{GDBN}
13567 is enforcing strict type checking rules.
13570 @cindex range checking
13571 @cindex checks, range
13572 @node Range Checking
13573 @subsection An Overview of Range Checking
13575 In some languages (such as Modula-2), it is an error to exceed the
13576 bounds of a type; this is enforced with run-time checks. Such range
13577 checking is meant to ensure program correctness by making sure
13578 computations do not overflow, or indices on an array element access do
13579 not exceed the bounds of the array.
13581 For expressions you use in @value{GDBN} commands, you can tell
13582 @value{GDBN} to treat range errors in one of three ways: ignore them,
13583 always treat them as errors and abandon the expression, or issue
13584 warnings but evaluate the expression anyway.
13586 A range error can result from numerical overflow, from exceeding an
13587 array index bound, or when you type a constant that is not a member
13588 of any type. Some languages, however, do not treat overflows as an
13589 error. In many implementations of C, mathematical overflow causes the
13590 result to ``wrap around'' to lower values---for example, if @var{m} is
13591 the largest integer value, and @var{s} is the smallest, then
13594 @var{m} + 1 @result{} @var{s}
13597 This, too, is specific to individual languages, and in some cases
13598 specific to individual compilers or machines. @xref{Supported Languages, ,
13599 Supported Languages}, for further details on specific languages.
13601 @value{GDBN} provides some additional commands for controlling the range checker:
13603 @kindex set check range
13604 @kindex show check range
13606 @item set check range auto
13607 Set range checking on or off based on the current working language.
13608 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13611 @item set check range on
13612 @itemx set check range off
13613 Set range checking on or off, overriding the default setting for the
13614 current working language. A warning is issued if the setting does not
13615 match the language default. If a range error occurs and range checking is on,
13616 then a message is printed and evaluation of the expression is aborted.
13618 @item set check range warn
13619 Output messages when the @value{GDBN} range checker detects a range error,
13620 but attempt to evaluate the expression anyway. Evaluating the
13621 expression may still be impossible for other reasons, such as accessing
13622 memory that the process does not own (a typical example from many Unix
13626 Show the current setting of the range checker, and whether or not it is
13627 being set automatically by @value{GDBN}.
13630 @node Supported Languages
13631 @section Supported Languages
13633 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13634 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13635 @c This is false ...
13636 Some @value{GDBN} features may be used in expressions regardless of the
13637 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13638 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13639 ,Expressions}) can be used with the constructs of any supported
13642 The following sections detail to what degree each source language is
13643 supported by @value{GDBN}. These sections are not meant to be language
13644 tutorials or references, but serve only as a reference guide to what the
13645 @value{GDBN} expression parser accepts, and what input and output
13646 formats should look like for different languages. There are many good
13647 books written on each of these languages; please look to these for a
13648 language reference or tutorial.
13651 * C:: C and C@t{++}
13654 * Objective-C:: Objective-C
13655 * OpenCL C:: OpenCL C
13656 * Fortran:: Fortran
13658 * Modula-2:: Modula-2
13663 @subsection C and C@t{++}
13665 @cindex C and C@t{++}
13666 @cindex expressions in C or C@t{++}
13668 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13669 to both languages. Whenever this is the case, we discuss those languages
13673 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13674 @cindex @sc{gnu} C@t{++}
13675 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13676 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13677 effectively, you must compile your C@t{++} programs with a supported
13678 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13679 compiler (@code{aCC}).
13682 * C Operators:: C and C@t{++} operators
13683 * C Constants:: C and C@t{++} constants
13684 * C Plus Plus Expressions:: C@t{++} expressions
13685 * C Defaults:: Default settings for C and C@t{++}
13686 * C Checks:: C and C@t{++} type and range checks
13687 * Debugging C:: @value{GDBN} and C
13688 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13689 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13693 @subsubsection C and C@t{++} Operators
13695 @cindex C and C@t{++} operators
13697 Operators must be defined on values of specific types. For instance,
13698 @code{+} is defined on numbers, but not on structures. Operators are
13699 often defined on groups of types.
13701 For the purposes of C and C@t{++}, the following definitions hold:
13706 @emph{Integral types} include @code{int} with any of its storage-class
13707 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13710 @emph{Floating-point types} include @code{float}, @code{double}, and
13711 @code{long double} (if supported by the target platform).
13714 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13717 @emph{Scalar types} include all of the above.
13722 The following operators are supported. They are listed here
13723 in order of increasing precedence:
13727 The comma or sequencing operator. Expressions in a comma-separated list
13728 are evaluated from left to right, with the result of the entire
13729 expression being the last expression evaluated.
13732 Assignment. The value of an assignment expression is the value
13733 assigned. Defined on scalar types.
13736 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13737 and translated to @w{@code{@var{a} = @var{a op b}}}.
13738 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
13739 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13740 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13743 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13744 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
13745 should be of an integral type.
13748 Logical @sc{or}. Defined on integral types.
13751 Logical @sc{and}. Defined on integral types.
13754 Bitwise @sc{or}. Defined on integral types.
13757 Bitwise exclusive-@sc{or}. Defined on integral types.
13760 Bitwise @sc{and}. Defined on integral types.
13763 Equality and inequality. Defined on scalar types. The value of these
13764 expressions is 0 for false and non-zero for true.
13766 @item <@r{, }>@r{, }<=@r{, }>=
13767 Less than, greater than, less than or equal, greater than or equal.
13768 Defined on scalar types. The value of these expressions is 0 for false
13769 and non-zero for true.
13772 left shift, and right shift. Defined on integral types.
13775 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13778 Addition and subtraction. Defined on integral types, floating-point types and
13781 @item *@r{, }/@r{, }%
13782 Multiplication, division, and modulus. Multiplication and division are
13783 defined on integral and floating-point types. Modulus is defined on
13787 Increment and decrement. When appearing before a variable, the
13788 operation is performed before the variable is used in an expression;
13789 when appearing after it, the variable's value is used before the
13790 operation takes place.
13793 Pointer dereferencing. Defined on pointer types. Same precedence as
13797 Address operator. Defined on variables. Same precedence as @code{++}.
13799 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13800 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13801 to examine the address
13802 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13806 Negative. Defined on integral and floating-point types. Same
13807 precedence as @code{++}.
13810 Logical negation. Defined on integral types. Same precedence as
13814 Bitwise complement operator. Defined on integral types. Same precedence as
13819 Structure member, and pointer-to-structure member. For convenience,
13820 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13821 pointer based on the stored type information.
13822 Defined on @code{struct} and @code{union} data.
13825 Dereferences of pointers to members.
13828 Array indexing. @code{@var{a}[@var{i}]} is defined as
13829 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13832 Function parameter list. Same precedence as @code{->}.
13835 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13836 and @code{class} types.
13839 Doubled colons also represent the @value{GDBN} scope operator
13840 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13844 If an operator is redefined in the user code, @value{GDBN} usually
13845 attempts to invoke the redefined version instead of using the operator's
13846 predefined meaning.
13849 @subsubsection C and C@t{++} Constants
13851 @cindex C and C@t{++} constants
13853 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13858 Integer constants are a sequence of digits. Octal constants are
13859 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13860 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13861 @samp{l}, specifying that the constant should be treated as a
13865 Floating point constants are a sequence of digits, followed by a decimal
13866 point, followed by a sequence of digits, and optionally followed by an
13867 exponent. An exponent is of the form:
13868 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13869 sequence of digits. The @samp{+} is optional for positive exponents.
13870 A floating-point constant may also end with a letter @samp{f} or
13871 @samp{F}, specifying that the constant should be treated as being of
13872 the @code{float} (as opposed to the default @code{double}) type; or with
13873 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13877 Enumerated constants consist of enumerated identifiers, or their
13878 integral equivalents.
13881 Character constants are a single character surrounded by single quotes
13882 (@code{'}), or a number---the ordinal value of the corresponding character
13883 (usually its @sc{ascii} value). Within quotes, the single character may
13884 be represented by a letter or by @dfn{escape sequences}, which are of
13885 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13886 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13887 @samp{@var{x}} is a predefined special character---for example,
13888 @samp{\n} for newline.
13890 Wide character constants can be written by prefixing a character
13891 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13892 form of @samp{x}. The target wide character set is used when
13893 computing the value of this constant (@pxref{Character Sets}).
13896 String constants are a sequence of character constants surrounded by
13897 double quotes (@code{"}). Any valid character constant (as described
13898 above) may appear. Double quotes within the string must be preceded by
13899 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13902 Wide string constants can be written by prefixing a string constant
13903 with @samp{L}, as in C. The target wide character set is used when
13904 computing the value of this constant (@pxref{Character Sets}).
13907 Pointer constants are an integral value. You can also write pointers
13908 to constants using the C operator @samp{&}.
13911 Array constants are comma-separated lists surrounded by braces @samp{@{}
13912 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13913 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13914 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13917 @node C Plus Plus Expressions
13918 @subsubsection C@t{++} Expressions
13920 @cindex expressions in C@t{++}
13921 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13923 @cindex debugging C@t{++} programs
13924 @cindex C@t{++} compilers
13925 @cindex debug formats and C@t{++}
13926 @cindex @value{NGCC} and C@t{++}
13928 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13929 the proper compiler and the proper debug format. Currently,
13930 @value{GDBN} works best when debugging C@t{++} code that is compiled
13931 with the most recent version of @value{NGCC} possible. The DWARF
13932 debugging format is preferred; @value{NGCC} defaults to this on most
13933 popular platforms. Other compilers and/or debug formats are likely to
13934 work badly or not at all when using @value{GDBN} to debug C@t{++}
13935 code. @xref{Compilation}.
13940 @cindex member functions
13942 Member function calls are allowed; you can use expressions like
13945 count = aml->GetOriginal(x, y)
13948 @vindex this@r{, inside C@t{++} member functions}
13949 @cindex namespace in C@t{++}
13951 While a member function is active (in the selected stack frame), your
13952 expressions have the same namespace available as the member function;
13953 that is, @value{GDBN} allows implicit references to the class instance
13954 pointer @code{this} following the same rules as C@t{++}. @code{using}
13955 declarations in the current scope are also respected by @value{GDBN}.
13957 @cindex call overloaded functions
13958 @cindex overloaded functions, calling
13959 @cindex type conversions in C@t{++}
13961 You can call overloaded functions; @value{GDBN} resolves the function
13962 call to the right definition, with some restrictions. @value{GDBN} does not
13963 perform overload resolution involving user-defined type conversions,
13964 calls to constructors, or instantiations of templates that do not exist
13965 in the program. It also cannot handle ellipsis argument lists or
13968 It does perform integral conversions and promotions, floating-point
13969 promotions, arithmetic conversions, pointer conversions, conversions of
13970 class objects to base classes, and standard conversions such as those of
13971 functions or arrays to pointers; it requires an exact match on the
13972 number of function arguments.
13974 Overload resolution is always performed, unless you have specified
13975 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13976 ,@value{GDBN} Features for C@t{++}}.
13978 You must specify @code{set overload-resolution off} in order to use an
13979 explicit function signature to call an overloaded function, as in
13981 p 'foo(char,int)'('x', 13)
13984 The @value{GDBN} command-completion facility can simplify this;
13985 see @ref{Completion, ,Command Completion}.
13987 @cindex reference declarations
13989 @value{GDBN} understands variables declared as C@t{++} references; you can use
13990 them in expressions just as you do in C@t{++} source---they are automatically
13993 In the parameter list shown when @value{GDBN} displays a frame, the values of
13994 reference variables are not displayed (unlike other variables); this
13995 avoids clutter, since references are often used for large structures.
13996 The @emph{address} of a reference variable is always shown, unless
13997 you have specified @samp{set print address off}.
14000 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14001 expressions can use it just as expressions in your program do. Since
14002 one scope may be defined in another, you can use @code{::} repeatedly if
14003 necessary, for example in an expression like
14004 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14005 resolving name scope by reference to source files, in both C and C@t{++}
14006 debugging (@pxref{Variables, ,Program Variables}).
14009 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14014 @subsubsection C and C@t{++} Defaults
14016 @cindex C and C@t{++} defaults
14018 If you allow @value{GDBN} to set range checking automatically, it
14019 defaults to @code{off} whenever the working language changes to
14020 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14021 selects the working language.
14023 If you allow @value{GDBN} to set the language automatically, it
14024 recognizes source files whose names end with @file{.c}, @file{.C}, or
14025 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14026 these files, it sets the working language to C or C@t{++}.
14027 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14028 for further details.
14031 @subsubsection C and C@t{++} Type and Range Checks
14033 @cindex C and C@t{++} checks
14035 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14036 checking is used. However, if you turn type checking off, @value{GDBN}
14037 will allow certain non-standard conversions, such as promoting integer
14038 constants to pointers.
14040 Range checking, if turned on, is done on mathematical operations. Array
14041 indices are not checked, since they are often used to index a pointer
14042 that is not itself an array.
14045 @subsubsection @value{GDBN} and C
14047 The @code{set print union} and @code{show print union} commands apply to
14048 the @code{union} type. When set to @samp{on}, any @code{union} that is
14049 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14050 appears as @samp{@{...@}}.
14052 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14053 with pointers and a memory allocation function. @xref{Expressions,
14056 @node Debugging C Plus Plus
14057 @subsubsection @value{GDBN} Features for C@t{++}
14059 @cindex commands for C@t{++}
14061 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14062 designed specifically for use with C@t{++}. Here is a summary:
14065 @cindex break in overloaded functions
14066 @item @r{breakpoint menus}
14067 When you want a breakpoint in a function whose name is overloaded,
14068 @value{GDBN} has the capability to display a menu of possible breakpoint
14069 locations to help you specify which function definition you want.
14070 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14072 @cindex overloading in C@t{++}
14073 @item rbreak @var{regex}
14074 Setting breakpoints using regular expressions is helpful for setting
14075 breakpoints on overloaded functions that are not members of any special
14077 @xref{Set Breaks, ,Setting Breakpoints}.
14079 @cindex C@t{++} exception handling
14081 @itemx catch rethrow
14083 Debug C@t{++} exception handling using these commands. @xref{Set
14084 Catchpoints, , Setting Catchpoints}.
14086 @cindex inheritance
14087 @item ptype @var{typename}
14088 Print inheritance relationships as well as other information for type
14090 @xref{Symbols, ,Examining the Symbol Table}.
14092 @item info vtbl @var{expression}.
14093 The @code{info vtbl} command can be used to display the virtual
14094 method tables of the object computed by @var{expression}. This shows
14095 one entry per virtual table; there may be multiple virtual tables when
14096 multiple inheritance is in use.
14098 @cindex C@t{++} symbol display
14099 @item set print demangle
14100 @itemx show print demangle
14101 @itemx set print asm-demangle
14102 @itemx show print asm-demangle
14103 Control whether C@t{++} symbols display in their source form, both when
14104 displaying code as C@t{++} source and when displaying disassemblies.
14105 @xref{Print Settings, ,Print Settings}.
14107 @item set print object
14108 @itemx show print object
14109 Choose whether to print derived (actual) or declared types of objects.
14110 @xref{Print Settings, ,Print Settings}.
14112 @item set print vtbl
14113 @itemx show print vtbl
14114 Control the format for printing virtual function tables.
14115 @xref{Print Settings, ,Print Settings}.
14116 (The @code{vtbl} commands do not work on programs compiled with the HP
14117 ANSI C@t{++} compiler (@code{aCC}).)
14119 @kindex set overload-resolution
14120 @cindex overloaded functions, overload resolution
14121 @item set overload-resolution on
14122 Enable overload resolution for C@t{++} expression evaluation. The default
14123 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14124 and searches for a function whose signature matches the argument types,
14125 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14126 Expressions, ,C@t{++} Expressions}, for details).
14127 If it cannot find a match, it emits a message.
14129 @item set overload-resolution off
14130 Disable overload resolution for C@t{++} expression evaluation. For
14131 overloaded functions that are not class member functions, @value{GDBN}
14132 chooses the first function of the specified name that it finds in the
14133 symbol table, whether or not its arguments are of the correct type. For
14134 overloaded functions that are class member functions, @value{GDBN}
14135 searches for a function whose signature @emph{exactly} matches the
14138 @kindex show overload-resolution
14139 @item show overload-resolution
14140 Show the current setting of overload resolution.
14142 @item @r{Overloaded symbol names}
14143 You can specify a particular definition of an overloaded symbol, using
14144 the same notation that is used to declare such symbols in C@t{++}: type
14145 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14146 also use the @value{GDBN} command-line word completion facilities to list the
14147 available choices, or to finish the type list for you.
14148 @xref{Completion,, Command Completion}, for details on how to do this.
14151 @node Decimal Floating Point
14152 @subsubsection Decimal Floating Point format
14153 @cindex decimal floating point format
14155 @value{GDBN} can examine, set and perform computations with numbers in
14156 decimal floating point format, which in the C language correspond to the
14157 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14158 specified by the extension to support decimal floating-point arithmetic.
14160 There are two encodings in use, depending on the architecture: BID (Binary
14161 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14162 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14165 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14166 to manipulate decimal floating point numbers, it is not possible to convert
14167 (using a cast, for example) integers wider than 32-bit to decimal float.
14169 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14170 point computations, error checking in decimal float operations ignores
14171 underflow, overflow and divide by zero exceptions.
14173 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14174 to inspect @code{_Decimal128} values stored in floating point registers.
14175 See @ref{PowerPC,,PowerPC} for more details.
14181 @value{GDBN} can be used to debug programs written in D and compiled with
14182 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14183 specific feature --- dynamic arrays.
14188 @cindex Go (programming language)
14189 @value{GDBN} can be used to debug programs written in Go and compiled with
14190 @file{gccgo} or @file{6g} compilers.
14192 Here is a summary of the Go-specific features and restrictions:
14195 @cindex current Go package
14196 @item The current Go package
14197 The name of the current package does not need to be specified when
14198 specifying global variables and functions.
14200 For example, given the program:
14204 var myglob = "Shall we?"
14210 When stopped inside @code{main} either of these work:
14214 (gdb) p main.myglob
14217 @cindex builtin Go types
14218 @item Builtin Go types
14219 The @code{string} type is recognized by @value{GDBN} and is printed
14222 @cindex builtin Go functions
14223 @item Builtin Go functions
14224 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14225 function and handles it internally.
14227 @cindex restrictions on Go expressions
14228 @item Restrictions on Go expressions
14229 All Go operators are supported except @code{&^}.
14230 The Go @code{_} ``blank identifier'' is not supported.
14231 Automatic dereferencing of pointers is not supported.
14235 @subsection Objective-C
14237 @cindex Objective-C
14238 This section provides information about some commands and command
14239 options that are useful for debugging Objective-C code. See also
14240 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14241 few more commands specific to Objective-C support.
14244 * Method Names in Commands::
14245 * The Print Command with Objective-C::
14248 @node Method Names in Commands
14249 @subsubsection Method Names in Commands
14251 The following commands have been extended to accept Objective-C method
14252 names as line specifications:
14254 @kindex clear@r{, and Objective-C}
14255 @kindex break@r{, and Objective-C}
14256 @kindex info line@r{, and Objective-C}
14257 @kindex jump@r{, and Objective-C}
14258 @kindex list@r{, and Objective-C}
14262 @item @code{info line}
14267 A fully qualified Objective-C method name is specified as
14270 -[@var{Class} @var{methodName}]
14273 where the minus sign is used to indicate an instance method and a
14274 plus sign (not shown) is used to indicate a class method. The class
14275 name @var{Class} and method name @var{methodName} are enclosed in
14276 brackets, similar to the way messages are specified in Objective-C
14277 source code. For example, to set a breakpoint at the @code{create}
14278 instance method of class @code{Fruit} in the program currently being
14282 break -[Fruit create]
14285 To list ten program lines around the @code{initialize} class method,
14289 list +[NSText initialize]
14292 In the current version of @value{GDBN}, the plus or minus sign is
14293 required. In future versions of @value{GDBN}, the plus or minus
14294 sign will be optional, but you can use it to narrow the search. It
14295 is also possible to specify just a method name:
14301 You must specify the complete method name, including any colons. If
14302 your program's source files contain more than one @code{create} method,
14303 you'll be presented with a numbered list of classes that implement that
14304 method. Indicate your choice by number, or type @samp{0} to exit if
14307 As another example, to clear a breakpoint established at the
14308 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14311 clear -[NSWindow makeKeyAndOrderFront:]
14314 @node The Print Command with Objective-C
14315 @subsubsection The Print Command With Objective-C
14316 @cindex Objective-C, print objects
14317 @kindex print-object
14318 @kindex po @r{(@code{print-object})}
14320 The print command has also been extended to accept methods. For example:
14323 print -[@var{object} hash]
14326 @cindex print an Objective-C object description
14327 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14329 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14330 and print the result. Also, an additional command has been added,
14331 @code{print-object} or @code{po} for short, which is meant to print
14332 the description of an object. However, this command may only work
14333 with certain Objective-C libraries that have a particular hook
14334 function, @code{_NSPrintForDebugger}, defined.
14337 @subsection OpenCL C
14340 This section provides information about @value{GDBN}s OpenCL C support.
14343 * OpenCL C Datatypes::
14344 * OpenCL C Expressions::
14345 * OpenCL C Operators::
14348 @node OpenCL C Datatypes
14349 @subsubsection OpenCL C Datatypes
14351 @cindex OpenCL C Datatypes
14352 @value{GDBN} supports the builtin scalar and vector datatypes specified
14353 by OpenCL 1.1. In addition the half- and double-precision floating point
14354 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14355 extensions are also known to @value{GDBN}.
14357 @node OpenCL C Expressions
14358 @subsubsection OpenCL C Expressions
14360 @cindex OpenCL C Expressions
14361 @value{GDBN} supports accesses to vector components including the access as
14362 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14363 supported by @value{GDBN} can be used as well.
14365 @node OpenCL C Operators
14366 @subsubsection OpenCL C Operators
14368 @cindex OpenCL C Operators
14369 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14373 @subsection Fortran
14374 @cindex Fortran-specific support in @value{GDBN}
14376 @value{GDBN} can be used to debug programs written in Fortran, but it
14377 currently supports only the features of Fortran 77 language.
14379 @cindex trailing underscore, in Fortran symbols
14380 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14381 among them) append an underscore to the names of variables and
14382 functions. When you debug programs compiled by those compilers, you
14383 will need to refer to variables and functions with a trailing
14387 * Fortran Operators:: Fortran operators and expressions
14388 * Fortran Defaults:: Default settings for Fortran
14389 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14392 @node Fortran Operators
14393 @subsubsection Fortran Operators and Expressions
14395 @cindex Fortran operators and expressions
14397 Operators must be defined on values of specific types. For instance,
14398 @code{+} is defined on numbers, but not on characters or other non-
14399 arithmetic types. Operators are often defined on groups of types.
14403 The exponentiation operator. It raises the first operand to the power
14407 The range operator. Normally used in the form of array(low:high) to
14408 represent a section of array.
14411 The access component operator. Normally used to access elements in derived
14412 types. Also suitable for unions. As unions aren't part of regular Fortran,
14413 this can only happen when accessing a register that uses a gdbarch-defined
14417 @node Fortran Defaults
14418 @subsubsection Fortran Defaults
14420 @cindex Fortran Defaults
14422 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14423 default uses case-insensitive matches for Fortran symbols. You can
14424 change that with the @samp{set case-insensitive} command, see
14425 @ref{Symbols}, for the details.
14427 @node Special Fortran Commands
14428 @subsubsection Special Fortran Commands
14430 @cindex Special Fortran commands
14432 @value{GDBN} has some commands to support Fortran-specific features,
14433 such as displaying common blocks.
14436 @cindex @code{COMMON} blocks, Fortran
14437 @kindex info common
14438 @item info common @r{[}@var{common-name}@r{]}
14439 This command prints the values contained in the Fortran @code{COMMON}
14440 block whose name is @var{common-name}. With no argument, the names of
14441 all @code{COMMON} blocks visible at the current program location are
14448 @cindex Pascal support in @value{GDBN}, limitations
14449 Debugging Pascal programs which use sets, subranges, file variables, or
14450 nested functions does not currently work. @value{GDBN} does not support
14451 entering expressions, printing values, or similar features using Pascal
14454 The Pascal-specific command @code{set print pascal_static-members}
14455 controls whether static members of Pascal objects are displayed.
14456 @xref{Print Settings, pascal_static-members}.
14459 @subsection Modula-2
14461 @cindex Modula-2, @value{GDBN} support
14463 The extensions made to @value{GDBN} to support Modula-2 only support
14464 output from the @sc{gnu} Modula-2 compiler (which is currently being
14465 developed). Other Modula-2 compilers are not currently supported, and
14466 attempting to debug executables produced by them is most likely
14467 to give an error as @value{GDBN} reads in the executable's symbol
14470 @cindex expressions in Modula-2
14472 * M2 Operators:: Built-in operators
14473 * Built-In Func/Proc:: Built-in functions and procedures
14474 * M2 Constants:: Modula-2 constants
14475 * M2 Types:: Modula-2 types
14476 * M2 Defaults:: Default settings for Modula-2
14477 * Deviations:: Deviations from standard Modula-2
14478 * M2 Checks:: Modula-2 type and range checks
14479 * M2 Scope:: The scope operators @code{::} and @code{.}
14480 * GDB/M2:: @value{GDBN} and Modula-2
14484 @subsubsection Operators
14485 @cindex Modula-2 operators
14487 Operators must be defined on values of specific types. For instance,
14488 @code{+} is defined on numbers, but not on structures. Operators are
14489 often defined on groups of types. For the purposes of Modula-2, the
14490 following definitions hold:
14495 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14499 @emph{Character types} consist of @code{CHAR} and its subranges.
14502 @emph{Floating-point types} consist of @code{REAL}.
14505 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14509 @emph{Scalar types} consist of all of the above.
14512 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14515 @emph{Boolean types} consist of @code{BOOLEAN}.
14519 The following operators are supported, and appear in order of
14520 increasing precedence:
14524 Function argument or array index separator.
14527 Assignment. The value of @var{var} @code{:=} @var{value} is
14531 Less than, greater than on integral, floating-point, or enumerated
14535 Less than or equal to, greater than or equal to
14536 on integral, floating-point and enumerated types, or set inclusion on
14537 set types. Same precedence as @code{<}.
14539 @item =@r{, }<>@r{, }#
14540 Equality and two ways of expressing inequality, valid on scalar types.
14541 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14542 available for inequality, since @code{#} conflicts with the script
14546 Set membership. Defined on set types and the types of their members.
14547 Same precedence as @code{<}.
14550 Boolean disjunction. Defined on boolean types.
14553 Boolean conjunction. Defined on boolean types.
14556 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14559 Addition and subtraction on integral and floating-point types, or union
14560 and difference on set types.
14563 Multiplication on integral and floating-point types, or set intersection
14567 Division on floating-point types, or symmetric set difference on set
14568 types. Same precedence as @code{*}.
14571 Integer division and remainder. Defined on integral types. Same
14572 precedence as @code{*}.
14575 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14578 Pointer dereferencing. Defined on pointer types.
14581 Boolean negation. Defined on boolean types. Same precedence as
14585 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14586 precedence as @code{^}.
14589 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14592 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14596 @value{GDBN} and Modula-2 scope operators.
14600 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14601 treats the use of the operator @code{IN}, or the use of operators
14602 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14603 @code{<=}, and @code{>=} on sets as an error.
14607 @node Built-In Func/Proc
14608 @subsubsection Built-in Functions and Procedures
14609 @cindex Modula-2 built-ins
14611 Modula-2 also makes available several built-in procedures and functions.
14612 In describing these, the following metavariables are used:
14617 represents an @code{ARRAY} variable.
14620 represents a @code{CHAR} constant or variable.
14623 represents a variable or constant of integral type.
14626 represents an identifier that belongs to a set. Generally used in the
14627 same function with the metavariable @var{s}. The type of @var{s} should
14628 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14631 represents a variable or constant of integral or floating-point type.
14634 represents a variable or constant of floating-point type.
14640 represents a variable.
14643 represents a variable or constant of one of many types. See the
14644 explanation of the function for details.
14647 All Modula-2 built-in procedures also return a result, described below.
14651 Returns the absolute value of @var{n}.
14654 If @var{c} is a lower case letter, it returns its upper case
14655 equivalent, otherwise it returns its argument.
14658 Returns the character whose ordinal value is @var{i}.
14661 Decrements the value in the variable @var{v} by one. Returns the new value.
14663 @item DEC(@var{v},@var{i})
14664 Decrements the value in the variable @var{v} by @var{i}. Returns the
14667 @item EXCL(@var{m},@var{s})
14668 Removes the element @var{m} from the set @var{s}. Returns the new
14671 @item FLOAT(@var{i})
14672 Returns the floating point equivalent of the integer @var{i}.
14674 @item HIGH(@var{a})
14675 Returns the index of the last member of @var{a}.
14678 Increments the value in the variable @var{v} by one. Returns the new value.
14680 @item INC(@var{v},@var{i})
14681 Increments the value in the variable @var{v} by @var{i}. Returns the
14684 @item INCL(@var{m},@var{s})
14685 Adds the element @var{m} to the set @var{s} if it is not already
14686 there. Returns the new set.
14689 Returns the maximum value of the type @var{t}.
14692 Returns the minimum value of the type @var{t}.
14695 Returns boolean TRUE if @var{i} is an odd number.
14698 Returns the ordinal value of its argument. For example, the ordinal
14699 value of a character is its @sc{ascii} value (on machines supporting
14700 the @sc{ascii} character set). The argument @var{x} must be of an
14701 ordered type, which include integral, character and enumerated types.
14703 @item SIZE(@var{x})
14704 Returns the size of its argument. The argument @var{x} can be a
14705 variable or a type.
14707 @item TRUNC(@var{r})
14708 Returns the integral part of @var{r}.
14710 @item TSIZE(@var{x})
14711 Returns the size of its argument. The argument @var{x} can be a
14712 variable or a type.
14714 @item VAL(@var{t},@var{i})
14715 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14719 @emph{Warning:} Sets and their operations are not yet supported, so
14720 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14724 @cindex Modula-2 constants
14726 @subsubsection Constants
14728 @value{GDBN} allows you to express the constants of Modula-2 in the following
14734 Integer constants are simply a sequence of digits. When used in an
14735 expression, a constant is interpreted to be type-compatible with the
14736 rest of the expression. Hexadecimal integers are specified by a
14737 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14740 Floating point constants appear as a sequence of digits, followed by a
14741 decimal point and another sequence of digits. An optional exponent can
14742 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14743 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14744 digits of the floating point constant must be valid decimal (base 10)
14748 Character constants consist of a single character enclosed by a pair of
14749 like quotes, either single (@code{'}) or double (@code{"}). They may
14750 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14751 followed by a @samp{C}.
14754 String constants consist of a sequence of characters enclosed by a
14755 pair of like quotes, either single (@code{'}) or double (@code{"}).
14756 Escape sequences in the style of C are also allowed. @xref{C
14757 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14761 Enumerated constants consist of an enumerated identifier.
14764 Boolean constants consist of the identifiers @code{TRUE} and
14768 Pointer constants consist of integral values only.
14771 Set constants are not yet supported.
14775 @subsubsection Modula-2 Types
14776 @cindex Modula-2 types
14778 Currently @value{GDBN} can print the following data types in Modula-2
14779 syntax: array types, record types, set types, pointer types, procedure
14780 types, enumerated types, subrange types and base types. You can also
14781 print the contents of variables declared using these type.
14782 This section gives a number of simple source code examples together with
14783 sample @value{GDBN} sessions.
14785 The first example contains the following section of code:
14794 and you can request @value{GDBN} to interrogate the type and value of
14795 @code{r} and @code{s}.
14798 (@value{GDBP}) print s
14800 (@value{GDBP}) ptype s
14802 (@value{GDBP}) print r
14804 (@value{GDBP}) ptype r
14809 Likewise if your source code declares @code{s} as:
14813 s: SET ['A'..'Z'] ;
14817 then you may query the type of @code{s} by:
14820 (@value{GDBP}) ptype s
14821 type = SET ['A'..'Z']
14825 Note that at present you cannot interactively manipulate set
14826 expressions using the debugger.
14828 The following example shows how you might declare an array in Modula-2
14829 and how you can interact with @value{GDBN} to print its type and contents:
14833 s: ARRAY [-10..10] OF CHAR ;
14837 (@value{GDBP}) ptype s
14838 ARRAY [-10..10] OF CHAR
14841 Note that the array handling is not yet complete and although the type
14842 is printed correctly, expression handling still assumes that all
14843 arrays have a lower bound of zero and not @code{-10} as in the example
14846 Here are some more type related Modula-2 examples:
14850 colour = (blue, red, yellow, green) ;
14851 t = [blue..yellow] ;
14859 The @value{GDBN} interaction shows how you can query the data type
14860 and value of a variable.
14863 (@value{GDBP}) print s
14865 (@value{GDBP}) ptype t
14866 type = [blue..yellow]
14870 In this example a Modula-2 array is declared and its contents
14871 displayed. Observe that the contents are written in the same way as
14872 their @code{C} counterparts.
14876 s: ARRAY [1..5] OF CARDINAL ;
14882 (@value{GDBP}) print s
14883 $1 = @{1, 0, 0, 0, 0@}
14884 (@value{GDBP}) ptype s
14885 type = ARRAY [1..5] OF CARDINAL
14888 The Modula-2 language interface to @value{GDBN} also understands
14889 pointer types as shown in this example:
14893 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14900 and you can request that @value{GDBN} describes the type of @code{s}.
14903 (@value{GDBP}) ptype s
14904 type = POINTER TO ARRAY [1..5] OF CARDINAL
14907 @value{GDBN} handles compound types as we can see in this example.
14908 Here we combine array types, record types, pointer types and subrange
14919 myarray = ARRAY myrange OF CARDINAL ;
14920 myrange = [-2..2] ;
14922 s: POINTER TO ARRAY myrange OF foo ;
14926 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14930 (@value{GDBP}) ptype s
14931 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14934 f3 : ARRAY [-2..2] OF CARDINAL;
14939 @subsubsection Modula-2 Defaults
14940 @cindex Modula-2 defaults
14942 If type and range checking are set automatically by @value{GDBN}, they
14943 both default to @code{on} whenever the working language changes to
14944 Modula-2. This happens regardless of whether you or @value{GDBN}
14945 selected the working language.
14947 If you allow @value{GDBN} to set the language automatically, then entering
14948 code compiled from a file whose name ends with @file{.mod} sets the
14949 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14950 Infer the Source Language}, for further details.
14953 @subsubsection Deviations from Standard Modula-2
14954 @cindex Modula-2, deviations from
14956 A few changes have been made to make Modula-2 programs easier to debug.
14957 This is done primarily via loosening its type strictness:
14961 Unlike in standard Modula-2, pointer constants can be formed by
14962 integers. This allows you to modify pointer variables during
14963 debugging. (In standard Modula-2, the actual address contained in a
14964 pointer variable is hidden from you; it can only be modified
14965 through direct assignment to another pointer variable or expression that
14966 returned a pointer.)
14969 C escape sequences can be used in strings and characters to represent
14970 non-printable characters. @value{GDBN} prints out strings with these
14971 escape sequences embedded. Single non-printable characters are
14972 printed using the @samp{CHR(@var{nnn})} format.
14975 The assignment operator (@code{:=}) returns the value of its right-hand
14979 All built-in procedures both modify @emph{and} return their argument.
14983 @subsubsection Modula-2 Type and Range Checks
14984 @cindex Modula-2 checks
14987 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14990 @c FIXME remove warning when type/range checks added
14992 @value{GDBN} considers two Modula-2 variables type equivalent if:
14996 They are of types that have been declared equivalent via a @code{TYPE
14997 @var{t1} = @var{t2}} statement
15000 They have been declared on the same line. (Note: This is true of the
15001 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15004 As long as type checking is enabled, any attempt to combine variables
15005 whose types are not equivalent is an error.
15007 Range checking is done on all mathematical operations, assignment, array
15008 index bounds, and all built-in functions and procedures.
15011 @subsubsection The Scope Operators @code{::} and @code{.}
15013 @cindex @code{.}, Modula-2 scope operator
15014 @cindex colon, doubled as scope operator
15016 @vindex colon-colon@r{, in Modula-2}
15017 @c Info cannot handle :: but TeX can.
15020 @vindex ::@r{, in Modula-2}
15023 There are a few subtle differences between the Modula-2 scope operator
15024 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15029 @var{module} . @var{id}
15030 @var{scope} :: @var{id}
15034 where @var{scope} is the name of a module or a procedure,
15035 @var{module} the name of a module, and @var{id} is any declared
15036 identifier within your program, except another module.
15038 Using the @code{::} operator makes @value{GDBN} search the scope
15039 specified by @var{scope} for the identifier @var{id}. If it is not
15040 found in the specified scope, then @value{GDBN} searches all scopes
15041 enclosing the one specified by @var{scope}.
15043 Using the @code{.} operator makes @value{GDBN} search the current scope for
15044 the identifier specified by @var{id} that was imported from the
15045 definition module specified by @var{module}. With this operator, it is
15046 an error if the identifier @var{id} was not imported from definition
15047 module @var{module}, or if @var{id} is not an identifier in
15051 @subsubsection @value{GDBN} and Modula-2
15053 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15054 Five subcommands of @code{set print} and @code{show print} apply
15055 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15056 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15057 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15058 analogue in Modula-2.
15060 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15061 with any language, is not useful with Modula-2. Its
15062 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15063 created in Modula-2 as they can in C or C@t{++}. However, because an
15064 address can be specified by an integral constant, the construct
15065 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15067 @cindex @code{#} in Modula-2
15068 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15069 interpreted as the beginning of a comment. Use @code{<>} instead.
15075 The extensions made to @value{GDBN} for Ada only support
15076 output from the @sc{gnu} Ada (GNAT) compiler.
15077 Other Ada compilers are not currently supported, and
15078 attempting to debug executables produced by them is most likely
15082 @cindex expressions in Ada
15084 * Ada Mode Intro:: General remarks on the Ada syntax
15085 and semantics supported by Ada mode
15087 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15088 * Additions to Ada:: Extensions of the Ada expression syntax.
15089 * Stopping Before Main Program:: Debugging the program during elaboration.
15090 * Ada Exceptions:: Ada Exceptions
15091 * Ada Tasks:: Listing and setting breakpoints in tasks.
15092 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15093 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15095 * Ada Glitches:: Known peculiarities of Ada mode.
15098 @node Ada Mode Intro
15099 @subsubsection Introduction
15100 @cindex Ada mode, general
15102 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15103 syntax, with some extensions.
15104 The philosophy behind the design of this subset is
15108 That @value{GDBN} should provide basic literals and access to operations for
15109 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15110 leaving more sophisticated computations to subprograms written into the
15111 program (which therefore may be called from @value{GDBN}).
15114 That type safety and strict adherence to Ada language restrictions
15115 are not particularly important to the @value{GDBN} user.
15118 That brevity is important to the @value{GDBN} user.
15121 Thus, for brevity, the debugger acts as if all names declared in
15122 user-written packages are directly visible, even if they are not visible
15123 according to Ada rules, thus making it unnecessary to fully qualify most
15124 names with their packages, regardless of context. Where this causes
15125 ambiguity, @value{GDBN} asks the user's intent.
15127 The debugger will start in Ada mode if it detects an Ada main program.
15128 As for other languages, it will enter Ada mode when stopped in a program that
15129 was translated from an Ada source file.
15131 While in Ada mode, you may use `@t{--}' for comments. This is useful
15132 mostly for documenting command files. The standard @value{GDBN} comment
15133 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15134 middle (to allow based literals).
15136 The debugger supports limited overloading. Given a subprogram call in which
15137 the function symbol has multiple definitions, it will use the number of
15138 actual parameters and some information about their types to attempt to narrow
15139 the set of definitions. It also makes very limited use of context, preferring
15140 procedures to functions in the context of the @code{call} command, and
15141 functions to procedures elsewhere.
15143 @node Omissions from Ada
15144 @subsubsection Omissions from Ada
15145 @cindex Ada, omissions from
15147 Here are the notable omissions from the subset:
15151 Only a subset of the attributes are supported:
15155 @t{'First}, @t{'Last}, and @t{'Length}
15156 on array objects (not on types and subtypes).
15159 @t{'Min} and @t{'Max}.
15162 @t{'Pos} and @t{'Val}.
15168 @t{'Range} on array objects (not subtypes), but only as the right
15169 operand of the membership (@code{in}) operator.
15172 @t{'Access}, @t{'Unchecked_Access}, and
15173 @t{'Unrestricted_Access} (a GNAT extension).
15181 @code{Characters.Latin_1} are not available and
15182 concatenation is not implemented. Thus, escape characters in strings are
15183 not currently available.
15186 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15187 equality of representations. They will generally work correctly
15188 for strings and arrays whose elements have integer or enumeration types.
15189 They may not work correctly for arrays whose element
15190 types have user-defined equality, for arrays of real values
15191 (in particular, IEEE-conformant floating point, because of negative
15192 zeroes and NaNs), and for arrays whose elements contain unused bits with
15193 indeterminate values.
15196 The other component-by-component array operations (@code{and}, @code{or},
15197 @code{xor}, @code{not}, and relational tests other than equality)
15198 are not implemented.
15201 @cindex array aggregates (Ada)
15202 @cindex record aggregates (Ada)
15203 @cindex aggregates (Ada)
15204 There is limited support for array and record aggregates. They are
15205 permitted only on the right sides of assignments, as in these examples:
15208 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15209 (@value{GDBP}) set An_Array := (1, others => 0)
15210 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15211 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15212 (@value{GDBP}) set A_Record := (1, "Peter", True);
15213 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15217 discriminant's value by assigning an aggregate has an
15218 undefined effect if that discriminant is used within the record.
15219 However, you can first modify discriminants by directly assigning to
15220 them (which normally would not be allowed in Ada), and then performing an
15221 aggregate assignment. For example, given a variable @code{A_Rec}
15222 declared to have a type such as:
15225 type Rec (Len : Small_Integer := 0) is record
15227 Vals : IntArray (1 .. Len);
15231 you can assign a value with a different size of @code{Vals} with two
15235 (@value{GDBP}) set A_Rec.Len := 4
15236 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15239 As this example also illustrates, @value{GDBN} is very loose about the usual
15240 rules concerning aggregates. You may leave out some of the
15241 components of an array or record aggregate (such as the @code{Len}
15242 component in the assignment to @code{A_Rec} above); they will retain their
15243 original values upon assignment. You may freely use dynamic values as
15244 indices in component associations. You may even use overlapping or
15245 redundant component associations, although which component values are
15246 assigned in such cases is not defined.
15249 Calls to dispatching subprograms are not implemented.
15252 The overloading algorithm is much more limited (i.e., less selective)
15253 than that of real Ada. It makes only limited use of the context in
15254 which a subexpression appears to resolve its meaning, and it is much
15255 looser in its rules for allowing type matches. As a result, some
15256 function calls will be ambiguous, and the user will be asked to choose
15257 the proper resolution.
15260 The @code{new} operator is not implemented.
15263 Entry calls are not implemented.
15266 Aside from printing, arithmetic operations on the native VAX floating-point
15267 formats are not supported.
15270 It is not possible to slice a packed array.
15273 The names @code{True} and @code{False}, when not part of a qualified name,
15274 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15276 Should your program
15277 redefine these names in a package or procedure (at best a dubious practice),
15278 you will have to use fully qualified names to access their new definitions.
15281 @node Additions to Ada
15282 @subsubsection Additions to Ada
15283 @cindex Ada, deviations from
15285 As it does for other languages, @value{GDBN} makes certain generic
15286 extensions to Ada (@pxref{Expressions}):
15290 If the expression @var{E} is a variable residing in memory (typically
15291 a local variable or array element) and @var{N} is a positive integer,
15292 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15293 @var{N}-1 adjacent variables following it in memory as an array. In
15294 Ada, this operator is generally not necessary, since its prime use is
15295 in displaying parts of an array, and slicing will usually do this in
15296 Ada. However, there are occasional uses when debugging programs in
15297 which certain debugging information has been optimized away.
15300 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15301 appears in function or file @var{B}.'' When @var{B} is a file name,
15302 you must typically surround it in single quotes.
15305 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15306 @var{type} that appears at address @var{addr}.''
15309 A name starting with @samp{$} is a convenience variable
15310 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15313 In addition, @value{GDBN} provides a few other shortcuts and outright
15314 additions specific to Ada:
15318 The assignment statement is allowed as an expression, returning
15319 its right-hand operand as its value. Thus, you may enter
15322 (@value{GDBP}) set x := y + 3
15323 (@value{GDBP}) print A(tmp := y + 1)
15327 The semicolon is allowed as an ``operator,'' returning as its value
15328 the value of its right-hand operand.
15329 This allows, for example,
15330 complex conditional breaks:
15333 (@value{GDBP}) break f
15334 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15338 Rather than use catenation and symbolic character names to introduce special
15339 characters into strings, one may instead use a special bracket notation,
15340 which is also used to print strings. A sequence of characters of the form
15341 @samp{["@var{XX}"]} within a string or character literal denotes the
15342 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15343 sequence of characters @samp{["""]} also denotes a single quotation mark
15344 in strings. For example,
15346 "One line.["0a"]Next line.["0a"]"
15349 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15353 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15354 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15358 (@value{GDBP}) print 'max(x, y)
15362 When printing arrays, @value{GDBN} uses positional notation when the
15363 array has a lower bound of 1, and uses a modified named notation otherwise.
15364 For example, a one-dimensional array of three integers with a lower bound
15365 of 3 might print as
15372 That is, in contrast to valid Ada, only the first component has a @code{=>}
15376 You may abbreviate attributes in expressions with any unique,
15377 multi-character subsequence of
15378 their names (an exact match gets preference).
15379 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15380 in place of @t{a'length}.
15383 @cindex quoting Ada internal identifiers
15384 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15385 to lower case. The GNAT compiler uses upper-case characters for
15386 some of its internal identifiers, which are normally of no interest to users.
15387 For the rare occasions when you actually have to look at them,
15388 enclose them in angle brackets to avoid the lower-case mapping.
15391 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15395 Printing an object of class-wide type or dereferencing an
15396 access-to-class-wide value will display all the components of the object's
15397 specific type (as indicated by its run-time tag). Likewise, component
15398 selection on such a value will operate on the specific type of the
15403 @node Stopping Before Main Program
15404 @subsubsection Stopping at the Very Beginning
15406 @cindex breakpointing Ada elaboration code
15407 It is sometimes necessary to debug the program during elaboration, and
15408 before reaching the main procedure.
15409 As defined in the Ada Reference
15410 Manual, the elaboration code is invoked from a procedure called
15411 @code{adainit}. To run your program up to the beginning of
15412 elaboration, simply use the following two commands:
15413 @code{tbreak adainit} and @code{run}.
15415 @node Ada Exceptions
15416 @subsubsection Ada Exceptions
15418 A command is provided to list all Ada exceptions:
15421 @kindex info exceptions
15422 @item info exceptions
15423 @itemx info exceptions @var{regexp}
15424 The @code{info exceptions} command allows you to list all Ada exceptions
15425 defined within the program being debugged, as well as their addresses.
15426 With a regular expression, @var{regexp}, as argument, only those exceptions
15427 whose names match @var{regexp} are listed.
15430 Below is a small example, showing how the command can be used, first
15431 without argument, and next with a regular expression passed as an
15435 (@value{GDBP}) info exceptions
15436 All defined Ada exceptions:
15437 constraint_error: 0x613da0
15438 program_error: 0x613d20
15439 storage_error: 0x613ce0
15440 tasking_error: 0x613ca0
15441 const.aint_global_e: 0x613b00
15442 (@value{GDBP}) info exceptions const.aint
15443 All Ada exceptions matching regular expression "const.aint":
15444 constraint_error: 0x613da0
15445 const.aint_global_e: 0x613b00
15448 It is also possible to ask @value{GDBN} to stop your program's execution
15449 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15452 @subsubsection Extensions for Ada Tasks
15453 @cindex Ada, tasking
15455 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15456 @value{GDBN} provides the following task-related commands:
15461 This command shows a list of current Ada tasks, as in the following example:
15468 (@value{GDBP}) info tasks
15469 ID TID P-ID Pri State Name
15470 1 8088000 0 15 Child Activation Wait main_task
15471 2 80a4000 1 15 Accept Statement b
15472 3 809a800 1 15 Child Activation Wait a
15473 * 4 80ae800 3 15 Runnable c
15478 In this listing, the asterisk before the last task indicates it to be the
15479 task currently being inspected.
15483 Represents @value{GDBN}'s internal task number.
15489 The parent's task ID (@value{GDBN}'s internal task number).
15492 The base priority of the task.
15495 Current state of the task.
15499 The task has been created but has not been activated. It cannot be
15503 The task is not blocked for any reason known to Ada. (It may be waiting
15504 for a mutex, though.) It is conceptually "executing" in normal mode.
15507 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15508 that were waiting on terminate alternatives have been awakened and have
15509 terminated themselves.
15511 @item Child Activation Wait
15512 The task is waiting for created tasks to complete activation.
15514 @item Accept Statement
15515 The task is waiting on an accept or selective wait statement.
15517 @item Waiting on entry call
15518 The task is waiting on an entry call.
15520 @item Async Select Wait
15521 The task is waiting to start the abortable part of an asynchronous
15525 The task is waiting on a select statement with only a delay
15528 @item Child Termination Wait
15529 The task is sleeping having completed a master within itself, and is
15530 waiting for the tasks dependent on that master to become terminated or
15531 waiting on a terminate Phase.
15533 @item Wait Child in Term Alt
15534 The task is sleeping waiting for tasks on terminate alternatives to
15535 finish terminating.
15537 @item Accepting RV with @var{taskno}
15538 The task is accepting a rendez-vous with the task @var{taskno}.
15542 Name of the task in the program.
15546 @kindex info task @var{taskno}
15547 @item info task @var{taskno}
15548 This command shows detailled informations on the specified task, as in
15549 the following example:
15554 (@value{GDBP}) info tasks
15555 ID TID P-ID Pri State Name
15556 1 8077880 0 15 Child Activation Wait main_task
15557 * 2 807c468 1 15 Runnable task_1
15558 (@value{GDBP}) info task 2
15559 Ada Task: 0x807c468
15562 Parent: 1 (main_task)
15568 @kindex task@r{ (Ada)}
15569 @cindex current Ada task ID
15570 This command prints the ID of the current task.
15576 (@value{GDBP}) info tasks
15577 ID TID P-ID Pri State Name
15578 1 8077870 0 15 Child Activation Wait main_task
15579 * 2 807c458 1 15 Runnable t
15580 (@value{GDBP}) task
15581 [Current task is 2]
15584 @item task @var{taskno}
15585 @cindex Ada task switching
15586 This command is like the @code{thread @var{threadno}}
15587 command (@pxref{Threads}). It switches the context of debugging
15588 from the current task to the given task.
15594 (@value{GDBP}) info tasks
15595 ID TID P-ID Pri State Name
15596 1 8077870 0 15 Child Activation Wait main_task
15597 * 2 807c458 1 15 Runnable t
15598 (@value{GDBP}) task 1
15599 [Switching to task 1]
15600 #0 0x8067726 in pthread_cond_wait ()
15602 #0 0x8067726 in pthread_cond_wait ()
15603 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15604 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15605 #3 0x806153e in system.tasking.stages.activate_tasks ()
15606 #4 0x804aacc in un () at un.adb:5
15609 @item break @var{linespec} task @var{taskno}
15610 @itemx break @var{linespec} task @var{taskno} if @dots{}
15611 @cindex breakpoints and tasks, in Ada
15612 @cindex task breakpoints, in Ada
15613 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15614 These commands are like the @code{break @dots{} thread @dots{}}
15615 command (@pxref{Thread Stops}). The
15616 @var{linespec} argument specifies source lines, as described
15617 in @ref{Specify Location}.
15619 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15620 to specify that you only want @value{GDBN} to stop the program when a
15621 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15622 numeric task identifiers assigned by @value{GDBN}, shown in the first
15623 column of the @samp{info tasks} display.
15625 If you do not specify @samp{task @var{taskno}} when you set a
15626 breakpoint, the breakpoint applies to @emph{all} tasks of your
15629 You can use the @code{task} qualifier on conditional breakpoints as
15630 well; in this case, place @samp{task @var{taskno}} before the
15631 breakpoint condition (before the @code{if}).
15639 (@value{GDBP}) info tasks
15640 ID TID P-ID Pri State Name
15641 1 140022020 0 15 Child Activation Wait main_task
15642 2 140045060 1 15 Accept/Select Wait t2
15643 3 140044840 1 15 Runnable t1
15644 * 4 140056040 1 15 Runnable t3
15645 (@value{GDBP}) b 15 task 2
15646 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15647 (@value{GDBP}) cont
15652 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15654 (@value{GDBP}) info tasks
15655 ID TID P-ID Pri State Name
15656 1 140022020 0 15 Child Activation Wait main_task
15657 * 2 140045060 1 15 Runnable t2
15658 3 140044840 1 15 Runnable t1
15659 4 140056040 1 15 Delay Sleep t3
15663 @node Ada Tasks and Core Files
15664 @subsubsection Tasking Support when Debugging Core Files
15665 @cindex Ada tasking and core file debugging
15667 When inspecting a core file, as opposed to debugging a live program,
15668 tasking support may be limited or even unavailable, depending on
15669 the platform being used.
15670 For instance, on x86-linux, the list of tasks is available, but task
15671 switching is not supported. On Tru64, however, task switching will work
15674 On certain platforms, including Tru64, the debugger needs to perform some
15675 memory writes in order to provide Ada tasking support. When inspecting
15676 a core file, this means that the core file must be opened with read-write
15677 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15678 Under these circumstances, you should make a backup copy of the core
15679 file before inspecting it with @value{GDBN}.
15681 @node Ravenscar Profile
15682 @subsubsection Tasking Support when using the Ravenscar Profile
15683 @cindex Ravenscar Profile
15685 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15686 specifically designed for systems with safety-critical real-time
15690 @kindex set ravenscar task-switching on
15691 @cindex task switching with program using Ravenscar Profile
15692 @item set ravenscar task-switching on
15693 Allows task switching when debugging a program that uses the Ravenscar
15694 Profile. This is the default.
15696 @kindex set ravenscar task-switching off
15697 @item set ravenscar task-switching off
15698 Turn off task switching when debugging a program that uses the Ravenscar
15699 Profile. This is mostly intended to disable the code that adds support
15700 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15701 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15702 To be effective, this command should be run before the program is started.
15704 @kindex show ravenscar task-switching
15705 @item show ravenscar task-switching
15706 Show whether it is possible to switch from task to task in a program
15707 using the Ravenscar Profile.
15712 @subsubsection Known Peculiarities of Ada Mode
15713 @cindex Ada, problems
15715 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15716 we know of several problems with and limitations of Ada mode in
15718 some of which will be fixed with planned future releases of the debugger
15719 and the GNU Ada compiler.
15723 Static constants that the compiler chooses not to materialize as objects in
15724 storage are invisible to the debugger.
15727 Named parameter associations in function argument lists are ignored (the
15728 argument lists are treated as positional).
15731 Many useful library packages are currently invisible to the debugger.
15734 Fixed-point arithmetic, conversions, input, and output is carried out using
15735 floating-point arithmetic, and may give results that only approximate those on
15739 The GNAT compiler never generates the prefix @code{Standard} for any of
15740 the standard symbols defined by the Ada language. @value{GDBN} knows about
15741 this: it will strip the prefix from names when you use it, and will never
15742 look for a name you have so qualified among local symbols, nor match against
15743 symbols in other packages or subprograms. If you have
15744 defined entities anywhere in your program other than parameters and
15745 local variables whose simple names match names in @code{Standard},
15746 GNAT's lack of qualification here can cause confusion. When this happens,
15747 you can usually resolve the confusion
15748 by qualifying the problematic names with package
15749 @code{Standard} explicitly.
15752 Older versions of the compiler sometimes generate erroneous debugging
15753 information, resulting in the debugger incorrectly printing the value
15754 of affected entities. In some cases, the debugger is able to work
15755 around an issue automatically. In other cases, the debugger is able
15756 to work around the issue, but the work-around has to be specifically
15759 @kindex set ada trust-PAD-over-XVS
15760 @kindex show ada trust-PAD-over-XVS
15763 @item set ada trust-PAD-over-XVS on
15764 Configure GDB to strictly follow the GNAT encoding when computing the
15765 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15766 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15767 a complete description of the encoding used by the GNAT compiler).
15768 This is the default.
15770 @item set ada trust-PAD-over-XVS off
15771 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15772 sometimes prints the wrong value for certain entities, changing @code{ada
15773 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15774 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15775 @code{off}, but this incurs a slight performance penalty, so it is
15776 recommended to leave this setting to @code{on} unless necessary.
15780 @cindex GNAT descriptive types
15781 @cindex GNAT encoding
15782 Internally, the debugger also relies on the compiler following a number
15783 of conventions known as the @samp{GNAT Encoding}, all documented in
15784 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
15785 how the debugging information should be generated for certain types.
15786 In particular, this convention makes use of @dfn{descriptive types},
15787 which are artificial types generated purely to help the debugger.
15789 These encodings were defined at a time when the debugging information
15790 format used was not powerful enough to describe some of the more complex
15791 types available in Ada. Since DWARF allows us to express nearly all
15792 Ada features, the long-term goal is to slowly replace these descriptive
15793 types by their pure DWARF equivalent. To facilitate that transition,
15794 a new maintenance option is available to force the debugger to ignore
15795 those descriptive types. It allows the user to quickly evaluate how
15796 well @value{GDBN} works without them.
15800 @kindex maint ada set ignore-descriptive-types
15801 @item maintenance ada set ignore-descriptive-types [on|off]
15802 Control whether the debugger should ignore descriptive types.
15803 The default is not to ignore descriptives types (@code{off}).
15805 @kindex maint ada show ignore-descriptive-types
15806 @item maintenance ada show ignore-descriptive-types
15807 Show if descriptive types are ignored by @value{GDBN}.
15811 @node Unsupported Languages
15812 @section Unsupported Languages
15814 @cindex unsupported languages
15815 @cindex minimal language
15816 In addition to the other fully-supported programming languages,
15817 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15818 It does not represent a real programming language, but provides a set
15819 of capabilities close to what the C or assembly languages provide.
15820 This should allow most simple operations to be performed while debugging
15821 an application that uses a language currently not supported by @value{GDBN}.
15823 If the language is set to @code{auto}, @value{GDBN} will automatically
15824 select this language if the current frame corresponds to an unsupported
15828 @chapter Examining the Symbol Table
15830 The commands described in this chapter allow you to inquire about the
15831 symbols (names of variables, functions and types) defined in your
15832 program. This information is inherent in the text of your program and
15833 does not change as your program executes. @value{GDBN} finds it in your
15834 program's symbol table, in the file indicated when you started @value{GDBN}
15835 (@pxref{File Options, ,Choosing Files}), or by one of the
15836 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15838 @cindex symbol names
15839 @cindex names of symbols
15840 @cindex quoting names
15841 Occasionally, you may need to refer to symbols that contain unusual
15842 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15843 most frequent case is in referring to static variables in other
15844 source files (@pxref{Variables,,Program Variables}). File names
15845 are recorded in object files as debugging symbols, but @value{GDBN} would
15846 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15847 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15848 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15855 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15858 @cindex case-insensitive symbol names
15859 @cindex case sensitivity in symbol names
15860 @kindex set case-sensitive
15861 @item set case-sensitive on
15862 @itemx set case-sensitive off
15863 @itemx set case-sensitive auto
15864 Normally, when @value{GDBN} looks up symbols, it matches their names
15865 with case sensitivity determined by the current source language.
15866 Occasionally, you may wish to control that. The command @code{set
15867 case-sensitive} lets you do that by specifying @code{on} for
15868 case-sensitive matches or @code{off} for case-insensitive ones. If
15869 you specify @code{auto}, case sensitivity is reset to the default
15870 suitable for the source language. The default is case-sensitive
15871 matches for all languages except for Fortran, for which the default is
15872 case-insensitive matches.
15874 @kindex show case-sensitive
15875 @item show case-sensitive
15876 This command shows the current setting of case sensitivity for symbols
15879 @kindex set print type methods
15880 @item set print type methods
15881 @itemx set print type methods on
15882 @itemx set print type methods off
15883 Normally, when @value{GDBN} prints a class, it displays any methods
15884 declared in that class. You can control this behavior either by
15885 passing the appropriate flag to @code{ptype}, or using @command{set
15886 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15887 display the methods; this is the default. Specifying @code{off} will
15888 cause @value{GDBN} to omit the methods.
15890 @kindex show print type methods
15891 @item show print type methods
15892 This command shows the current setting of method display when printing
15895 @kindex set print type typedefs
15896 @item set print type typedefs
15897 @itemx set print type typedefs on
15898 @itemx set print type typedefs off
15900 Normally, when @value{GDBN} prints a class, it displays any typedefs
15901 defined in that class. You can control this behavior either by
15902 passing the appropriate flag to @code{ptype}, or using @command{set
15903 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15904 display the typedef definitions; this is the default. Specifying
15905 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15906 Note that this controls whether the typedef definition itself is
15907 printed, not whether typedef names are substituted when printing other
15910 @kindex show print type typedefs
15911 @item show print type typedefs
15912 This command shows the current setting of typedef display when
15915 @kindex info address
15916 @cindex address of a symbol
15917 @item info address @var{symbol}
15918 Describe where the data for @var{symbol} is stored. For a register
15919 variable, this says which register it is kept in. For a non-register
15920 local variable, this prints the stack-frame offset at which the variable
15923 Note the contrast with @samp{print &@var{symbol}}, which does not work
15924 at all for a register variable, and for a stack local variable prints
15925 the exact address of the current instantiation of the variable.
15927 @kindex info symbol
15928 @cindex symbol from address
15929 @cindex closest symbol and offset for an address
15930 @item info symbol @var{addr}
15931 Print the name of a symbol which is stored at the address @var{addr}.
15932 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15933 nearest symbol and an offset from it:
15936 (@value{GDBP}) info symbol 0x54320
15937 _initialize_vx + 396 in section .text
15941 This is the opposite of the @code{info address} command. You can use
15942 it to find out the name of a variable or a function given its address.
15944 For dynamically linked executables, the name of executable or shared
15945 library containing the symbol is also printed:
15948 (@value{GDBP}) info symbol 0x400225
15949 _start + 5 in section .text of /tmp/a.out
15950 (@value{GDBP}) info symbol 0x2aaaac2811cf
15951 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15955 @item whatis[/@var{flags}] [@var{arg}]
15956 Print the data type of @var{arg}, which can be either an expression
15957 or a name of a data type. With no argument, print the data type of
15958 @code{$}, the last value in the value history.
15960 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15961 is not actually evaluated, and any side-effecting operations (such as
15962 assignments or function calls) inside it do not take place.
15964 If @var{arg} is a variable or an expression, @code{whatis} prints its
15965 literal type as it is used in the source code. If the type was
15966 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15967 the data type underlying the @code{typedef}. If the type of the
15968 variable or the expression is a compound data type, such as
15969 @code{struct} or @code{class}, @code{whatis} never prints their
15970 fields or methods. It just prints the @code{struct}/@code{class}
15971 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15972 such a compound data type, use @code{ptype}.
15974 If @var{arg} is a type name that was defined using @code{typedef},
15975 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15976 Unrolling means that @code{whatis} will show the underlying type used
15977 in the @code{typedef} declaration of @var{arg}. However, if that
15978 underlying type is also a @code{typedef}, @code{whatis} will not
15981 For C code, the type names may also have the form @samp{class
15982 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15983 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15985 @var{flags} can be used to modify how the type is displayed.
15986 Available flags are:
15990 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15991 parameters and typedefs defined in a class when printing the class'
15992 members. The @code{/r} flag disables this.
15995 Do not print methods defined in the class.
15998 Print methods defined in the class. This is the default, but the flag
15999 exists in case you change the default with @command{set print type methods}.
16002 Do not print typedefs defined in the class. Note that this controls
16003 whether the typedef definition itself is printed, not whether typedef
16004 names are substituted when printing other types.
16007 Print typedefs defined in the class. This is the default, but the flag
16008 exists in case you change the default with @command{set print type typedefs}.
16012 @item ptype[/@var{flags}] [@var{arg}]
16013 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16014 detailed description of the type, instead of just the name of the type.
16015 @xref{Expressions, ,Expressions}.
16017 Contrary to @code{whatis}, @code{ptype} always unrolls any
16018 @code{typedef}s in its argument declaration, whether the argument is
16019 a variable, expression, or a data type. This means that @code{ptype}
16020 of a variable or an expression will not print literally its type as
16021 present in the source code---use @code{whatis} for that. @code{typedef}s at
16022 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16023 fields, methods and inner @code{class typedef}s of @code{struct}s,
16024 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16026 For example, for this variable declaration:
16029 typedef double real_t;
16030 struct complex @{ real_t real; double imag; @};
16031 typedef struct complex complex_t;
16033 real_t *real_pointer_var;
16037 the two commands give this output:
16041 (@value{GDBP}) whatis var
16043 (@value{GDBP}) ptype var
16044 type = struct complex @{
16048 (@value{GDBP}) whatis complex_t
16049 type = struct complex
16050 (@value{GDBP}) whatis struct complex
16051 type = struct complex
16052 (@value{GDBP}) ptype struct complex
16053 type = struct complex @{
16057 (@value{GDBP}) whatis real_pointer_var
16059 (@value{GDBP}) ptype real_pointer_var
16065 As with @code{whatis}, using @code{ptype} without an argument refers to
16066 the type of @code{$}, the last value in the value history.
16068 @cindex incomplete type
16069 Sometimes, programs use opaque data types or incomplete specifications
16070 of complex data structure. If the debug information included in the
16071 program does not allow @value{GDBN} to display a full declaration of
16072 the data type, it will say @samp{<incomplete type>}. For example,
16073 given these declarations:
16077 struct foo *fooptr;
16081 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16084 (@value{GDBP}) ptype foo
16085 $1 = <incomplete type>
16089 ``Incomplete type'' is C terminology for data types that are not
16090 completely specified.
16093 @item info types @var{regexp}
16095 Print a brief description of all types whose names match the regular
16096 expression @var{regexp} (or all types in your program, if you supply
16097 no argument). Each complete typename is matched as though it were a
16098 complete line; thus, @samp{i type value} gives information on all
16099 types in your program whose names include the string @code{value}, but
16100 @samp{i type ^value$} gives information only on types whose complete
16101 name is @code{value}.
16103 This command differs from @code{ptype} in two ways: first, like
16104 @code{whatis}, it does not print a detailed description; second, it
16105 lists all source files where a type is defined.
16107 @kindex info type-printers
16108 @item info type-printers
16109 Versions of @value{GDBN} that ship with Python scripting enabled may
16110 have ``type printers'' available. When using @command{ptype} or
16111 @command{whatis}, these printers are consulted when the name of a type
16112 is needed. @xref{Type Printing API}, for more information on writing
16115 @code{info type-printers} displays all the available type printers.
16117 @kindex enable type-printer
16118 @kindex disable type-printer
16119 @item enable type-printer @var{name}@dots{}
16120 @item disable type-printer @var{name}@dots{}
16121 These commands can be used to enable or disable type printers.
16124 @cindex local variables
16125 @item info scope @var{location}
16126 List all the variables local to a particular scope. This command
16127 accepts a @var{location} argument---a function name, a source line, or
16128 an address preceded by a @samp{*}, and prints all the variables local
16129 to the scope defined by that location. (@xref{Specify Location}, for
16130 details about supported forms of @var{location}.) For example:
16133 (@value{GDBP}) @b{info scope command_line_handler}
16134 Scope for command_line_handler:
16135 Symbol rl is an argument at stack/frame offset 8, length 4.
16136 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16137 Symbol linelength is in static storage at address 0x150a1c, length 4.
16138 Symbol p is a local variable in register $esi, length 4.
16139 Symbol p1 is a local variable in register $ebx, length 4.
16140 Symbol nline is a local variable in register $edx, length 4.
16141 Symbol repeat is a local variable at frame offset -8, length 4.
16145 This command is especially useful for determining what data to collect
16146 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16149 @kindex info source
16151 Show information about the current source file---that is, the source file for
16152 the function containing the current point of execution:
16155 the name of the source file, and the directory containing it,
16157 the directory it was compiled in,
16159 its length, in lines,
16161 which programming language it is written in,
16163 whether the executable includes debugging information for that file, and
16164 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16166 whether the debugging information includes information about
16167 preprocessor macros.
16171 @kindex info sources
16173 Print the names of all source files in your program for which there is
16174 debugging information, organized into two lists: files whose symbols
16175 have already been read, and files whose symbols will be read when needed.
16177 @kindex info functions
16178 @item info functions
16179 Print the names and data types of all defined functions.
16181 @item info functions @var{regexp}
16182 Print the names and data types of all defined functions
16183 whose names contain a match for regular expression @var{regexp}.
16184 Thus, @samp{info fun step} finds all functions whose names
16185 include @code{step}; @samp{info fun ^step} finds those whose names
16186 start with @code{step}. If a function name contains characters
16187 that conflict with the regular expression language (e.g.@:
16188 @samp{operator*()}), they may be quoted with a backslash.
16190 @kindex info variables
16191 @item info variables
16192 Print the names and data types of all variables that are defined
16193 outside of functions (i.e.@: excluding local variables).
16195 @item info variables @var{regexp}
16196 Print the names and data types of all variables (except for local
16197 variables) whose names contain a match for regular expression
16200 @kindex info classes
16201 @cindex Objective-C, classes and selectors
16203 @itemx info classes @var{regexp}
16204 Display all Objective-C classes in your program, or
16205 (with the @var{regexp} argument) all those matching a particular regular
16208 @kindex info selectors
16209 @item info selectors
16210 @itemx info selectors @var{regexp}
16211 Display all Objective-C selectors in your program, or
16212 (with the @var{regexp} argument) all those matching a particular regular
16216 This was never implemented.
16217 @kindex info methods
16219 @itemx info methods @var{regexp}
16220 The @code{info methods} command permits the user to examine all defined
16221 methods within C@t{++} program, or (with the @var{regexp} argument) a
16222 specific set of methods found in the various C@t{++} classes. Many
16223 C@t{++} classes provide a large number of methods. Thus, the output
16224 from the @code{ptype} command can be overwhelming and hard to use. The
16225 @code{info-methods} command filters the methods, printing only those
16226 which match the regular-expression @var{regexp}.
16229 @cindex opaque data types
16230 @kindex set opaque-type-resolution
16231 @item set opaque-type-resolution on
16232 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16233 declared as a pointer to a @code{struct}, @code{class}, or
16234 @code{union}---for example, @code{struct MyType *}---that is used in one
16235 source file although the full declaration of @code{struct MyType} is in
16236 another source file. The default is on.
16238 A change in the setting of this subcommand will not take effect until
16239 the next time symbols for a file are loaded.
16241 @item set opaque-type-resolution off
16242 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16243 is printed as follows:
16245 @{<no data fields>@}
16248 @kindex show opaque-type-resolution
16249 @item show opaque-type-resolution
16250 Show whether opaque types are resolved or not.
16252 @kindex set print symbol-loading
16253 @cindex print messages when symbols are loaded
16254 @item set print symbol-loading
16255 @itemx set print symbol-loading full
16256 @itemx set print symbol-loading brief
16257 @itemx set print symbol-loading off
16258 The @code{set print symbol-loading} command allows you to control the
16259 printing of messages when @value{GDBN} loads symbol information.
16260 By default a message is printed for the executable and one for each
16261 shared library, and normally this is what you want. However, when
16262 debugging apps with large numbers of shared libraries these messages
16264 When set to @code{brief} a message is printed for each executable,
16265 and when @value{GDBN} loads a collection of shared libraries at once
16266 it will only print one message regardless of the number of shared
16267 libraries. When set to @code{off} no messages are printed.
16269 @kindex show print symbol-loading
16270 @item show print symbol-loading
16271 Show whether messages will be printed when a @value{GDBN} command
16272 entered from the keyboard causes symbol information to be loaded.
16274 @kindex maint print symbols
16275 @cindex symbol dump
16276 @kindex maint print psymbols
16277 @cindex partial symbol dump
16278 @kindex maint print msymbols
16279 @cindex minimal symbol dump
16280 @item maint print symbols @var{filename}
16281 @itemx maint print psymbols @var{filename}
16282 @itemx maint print msymbols @var{filename}
16283 Write a dump of debugging symbol data into the file @var{filename}.
16284 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16285 symbols with debugging data are included. If you use @samp{maint print
16286 symbols}, @value{GDBN} includes all the symbols for which it has already
16287 collected full details: that is, @var{filename} reflects symbols for
16288 only those files whose symbols @value{GDBN} has read. You can use the
16289 command @code{info sources} to find out which files these are. If you
16290 use @samp{maint print psymbols} instead, the dump shows information about
16291 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16292 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16293 @samp{maint print msymbols} dumps just the minimal symbol information
16294 required for each object file from which @value{GDBN} has read some symbols.
16295 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16296 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16298 @kindex maint info symtabs
16299 @kindex maint info psymtabs
16300 @cindex listing @value{GDBN}'s internal symbol tables
16301 @cindex symbol tables, listing @value{GDBN}'s internal
16302 @cindex full symbol tables, listing @value{GDBN}'s internal
16303 @cindex partial symbol tables, listing @value{GDBN}'s internal
16304 @item maint info symtabs @r{[} @var{regexp} @r{]}
16305 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16307 List the @code{struct symtab} or @code{struct partial_symtab}
16308 structures whose names match @var{regexp}. If @var{regexp} is not
16309 given, list them all. The output includes expressions which you can
16310 copy into a @value{GDBN} debugging this one to examine a particular
16311 structure in more detail. For example:
16314 (@value{GDBP}) maint info psymtabs dwarf2read
16315 @{ objfile /home/gnu/build/gdb/gdb
16316 ((struct objfile *) 0x82e69d0)
16317 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16318 ((struct partial_symtab *) 0x8474b10)
16321 text addresses 0x814d3c8 -- 0x8158074
16322 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16323 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16324 dependencies (none)
16327 (@value{GDBP}) maint info symtabs
16331 We see that there is one partial symbol table whose filename contains
16332 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16333 and we see that @value{GDBN} has not read in any symtabs yet at all.
16334 If we set a breakpoint on a function, that will cause @value{GDBN} to
16335 read the symtab for the compilation unit containing that function:
16338 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16339 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16341 (@value{GDBP}) maint info symtabs
16342 @{ objfile /home/gnu/build/gdb/gdb
16343 ((struct objfile *) 0x82e69d0)
16344 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16345 ((struct symtab *) 0x86c1f38)
16348 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16349 linetable ((struct linetable *) 0x8370fa0)
16350 debugformat DWARF 2
16359 @chapter Altering Execution
16361 Once you think you have found an error in your program, you might want to
16362 find out for certain whether correcting the apparent error would lead to
16363 correct results in the rest of the run. You can find the answer by
16364 experiment, using the @value{GDBN} features for altering execution of the
16367 For example, you can store new values into variables or memory
16368 locations, give your program a signal, restart it at a different
16369 address, or even return prematurely from a function.
16372 * Assignment:: Assignment to variables
16373 * Jumping:: Continuing at a different address
16374 * Signaling:: Giving your program a signal
16375 * Returning:: Returning from a function
16376 * Calling:: Calling your program's functions
16377 * Patching:: Patching your program
16381 @section Assignment to Variables
16384 @cindex setting variables
16385 To alter the value of a variable, evaluate an assignment expression.
16386 @xref{Expressions, ,Expressions}. For example,
16393 stores the value 4 into the variable @code{x}, and then prints the
16394 value of the assignment expression (which is 4).
16395 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16396 information on operators in supported languages.
16398 @kindex set variable
16399 @cindex variables, setting
16400 If you are not interested in seeing the value of the assignment, use the
16401 @code{set} command instead of the @code{print} command. @code{set} is
16402 really the same as @code{print} except that the expression's value is
16403 not printed and is not put in the value history (@pxref{Value History,
16404 ,Value History}). The expression is evaluated only for its effects.
16406 If the beginning of the argument string of the @code{set} command
16407 appears identical to a @code{set} subcommand, use the @code{set
16408 variable} command instead of just @code{set}. This command is identical
16409 to @code{set} except for its lack of subcommands. For example, if your
16410 program has a variable @code{width}, you get an error if you try to set
16411 a new value with just @samp{set width=13}, because @value{GDBN} has the
16412 command @code{set width}:
16415 (@value{GDBP}) whatis width
16417 (@value{GDBP}) p width
16419 (@value{GDBP}) set width=47
16420 Invalid syntax in expression.
16424 The invalid expression, of course, is @samp{=47}. In
16425 order to actually set the program's variable @code{width}, use
16428 (@value{GDBP}) set var width=47
16431 Because the @code{set} command has many subcommands that can conflict
16432 with the names of program variables, it is a good idea to use the
16433 @code{set variable} command instead of just @code{set}. For example, if
16434 your program has a variable @code{g}, you run into problems if you try
16435 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16436 the command @code{set gnutarget}, abbreviated @code{set g}:
16440 (@value{GDBP}) whatis g
16444 (@value{GDBP}) set g=4
16448 The program being debugged has been started already.
16449 Start it from the beginning? (y or n) y
16450 Starting program: /home/smith/cc_progs/a.out
16451 "/home/smith/cc_progs/a.out": can't open to read symbols:
16452 Invalid bfd target.
16453 (@value{GDBP}) show g
16454 The current BFD target is "=4".
16459 The program variable @code{g} did not change, and you silently set the
16460 @code{gnutarget} to an invalid value. In order to set the variable
16464 (@value{GDBP}) set var g=4
16467 @value{GDBN} allows more implicit conversions in assignments than C; you can
16468 freely store an integer value into a pointer variable or vice versa,
16469 and you can convert any structure to any other structure that is the
16470 same length or shorter.
16471 @comment FIXME: how do structs align/pad in these conversions?
16472 @comment /doc@cygnus.com 18dec1990
16474 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16475 construct to generate a value of specified type at a specified address
16476 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16477 to memory location @code{0x83040} as an integer (which implies a certain size
16478 and representation in memory), and
16481 set @{int@}0x83040 = 4
16485 stores the value 4 into that memory location.
16488 @section Continuing at a Different Address
16490 Ordinarily, when you continue your program, you do so at the place where
16491 it stopped, with the @code{continue} command. You can instead continue at
16492 an address of your own choosing, with the following commands:
16496 @kindex j @r{(@code{jump})}
16497 @item jump @var{linespec}
16498 @itemx j @var{linespec}
16499 @itemx jump @var{location}
16500 @itemx j @var{location}
16501 Resume execution at line @var{linespec} or at address given by
16502 @var{location}. Execution stops again immediately if there is a
16503 breakpoint there. @xref{Specify Location}, for a description of the
16504 different forms of @var{linespec} and @var{location}. It is common
16505 practice to use the @code{tbreak} command in conjunction with
16506 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16508 The @code{jump} command does not change the current stack frame, or
16509 the stack pointer, or the contents of any memory location or any
16510 register other than the program counter. If line @var{linespec} is in
16511 a different function from the one currently executing, the results may
16512 be bizarre if the two functions expect different patterns of arguments or
16513 of local variables. For this reason, the @code{jump} command requests
16514 confirmation if the specified line is not in the function currently
16515 executing. However, even bizarre results are predictable if you are
16516 well acquainted with the machine-language code of your program.
16519 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16520 On many systems, you can get much the same effect as the @code{jump}
16521 command by storing a new value into the register @code{$pc}. The
16522 difference is that this does not start your program running; it only
16523 changes the address of where it @emph{will} run when you continue. For
16531 makes the next @code{continue} command or stepping command execute at
16532 address @code{0x485}, rather than at the address where your program stopped.
16533 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16535 The most common occasion to use the @code{jump} command is to back
16536 up---perhaps with more breakpoints set---over a portion of a program
16537 that has already executed, in order to examine its execution in more
16542 @section Giving your Program a Signal
16543 @cindex deliver a signal to a program
16547 @item signal @var{signal}
16548 Resume execution where your program stopped, but immediately give it the
16549 signal @var{signal}. The @var{signal} can be the name or the number of a
16550 signal. For example, on many systems @code{signal 2} and @code{signal
16551 SIGINT} are both ways of sending an interrupt signal.
16553 Alternatively, if @var{signal} is zero, continue execution without
16554 giving a signal. This is useful when your program stopped on account of
16555 a signal and would ordinarily see the signal when resumed with the
16556 @code{continue} command; @samp{signal 0} causes it to resume without a
16559 @code{signal} does not repeat when you press @key{RET} a second time
16560 after executing the command.
16564 Invoking the @code{signal} command is not the same as invoking the
16565 @code{kill} utility from the shell. Sending a signal with @code{kill}
16566 causes @value{GDBN} to decide what to do with the signal depending on
16567 the signal handling tables (@pxref{Signals}). The @code{signal} command
16568 passes the signal directly to your program.
16572 @section Returning from a Function
16575 @cindex returning from a function
16578 @itemx return @var{expression}
16579 You can cancel execution of a function call with the @code{return}
16580 command. If you give an
16581 @var{expression} argument, its value is used as the function's return
16585 When you use @code{return}, @value{GDBN} discards the selected stack frame
16586 (and all frames within it). You can think of this as making the
16587 discarded frame return prematurely. If you wish to specify a value to
16588 be returned, give that value as the argument to @code{return}.
16590 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16591 Frame}), and any other frames inside of it, leaving its caller as the
16592 innermost remaining frame. That frame becomes selected. The
16593 specified value is stored in the registers used for returning values
16596 The @code{return} command does not resume execution; it leaves the
16597 program stopped in the state that would exist if the function had just
16598 returned. In contrast, the @code{finish} command (@pxref{Continuing
16599 and Stepping, ,Continuing and Stepping}) resumes execution until the
16600 selected stack frame returns naturally.
16602 @value{GDBN} needs to know how the @var{expression} argument should be set for
16603 the inferior. The concrete registers assignment depends on the OS ABI and the
16604 type being returned by the selected stack frame. For example it is common for
16605 OS ABI to return floating point values in FPU registers while integer values in
16606 CPU registers. Still some ABIs return even floating point values in CPU
16607 registers. Larger integer widths (such as @code{long long int}) also have
16608 specific placement rules. @value{GDBN} already knows the OS ABI from its
16609 current target so it needs to find out also the type being returned to make the
16610 assignment into the right register(s).
16612 Normally, the selected stack frame has debug info. @value{GDBN} will always
16613 use the debug info instead of the implicit type of @var{expression} when the
16614 debug info is available. For example, if you type @kbd{return -1}, and the
16615 function in the current stack frame is declared to return a @code{long long
16616 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16617 into a @code{long long int}:
16620 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16622 (@value{GDBP}) return -1
16623 Make func return now? (y or n) y
16624 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16625 43 printf ("result=%lld\n", func ());
16629 However, if the selected stack frame does not have a debug info, e.g., if the
16630 function was compiled without debug info, @value{GDBN} has to find out the type
16631 to return from user. Specifying a different type by mistake may set the value
16632 in different inferior registers than the caller code expects. For example,
16633 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16634 of a @code{long long int} result for a debug info less function (on 32-bit
16635 architectures). Therefore the user is required to specify the return type by
16636 an appropriate cast explicitly:
16639 Breakpoint 2, 0x0040050b in func ()
16640 (@value{GDBP}) return -1
16641 Return value type not available for selected stack frame.
16642 Please use an explicit cast of the value to return.
16643 (@value{GDBP}) return (long long int) -1
16644 Make selected stack frame return now? (y or n) y
16645 #0 0x00400526 in main ()
16650 @section Calling Program Functions
16653 @cindex calling functions
16654 @cindex inferior functions, calling
16655 @item print @var{expr}
16656 Evaluate the expression @var{expr} and display the resulting value.
16657 The expression may include calls to functions in the program being
16661 @item call @var{expr}
16662 Evaluate the expression @var{expr} without displaying @code{void}
16665 You can use this variant of the @code{print} command if you want to
16666 execute a function from your program that does not return anything
16667 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16668 with @code{void} returned values that @value{GDBN} will otherwise
16669 print. If the result is not void, it is printed and saved in the
16673 It is possible for the function you call via the @code{print} or
16674 @code{call} command to generate a signal (e.g., if there's a bug in
16675 the function, or if you passed it incorrect arguments). What happens
16676 in that case is controlled by the @code{set unwindonsignal} command.
16678 Similarly, with a C@t{++} program it is possible for the function you
16679 call via the @code{print} or @code{call} command to generate an
16680 exception that is not handled due to the constraints of the dummy
16681 frame. In this case, any exception that is raised in the frame, but has
16682 an out-of-frame exception handler will not be found. GDB builds a
16683 dummy-frame for the inferior function call, and the unwinder cannot
16684 seek for exception handlers outside of this dummy-frame. What happens
16685 in that case is controlled by the
16686 @code{set unwind-on-terminating-exception} command.
16689 @item set unwindonsignal
16690 @kindex set unwindonsignal
16691 @cindex unwind stack in called functions
16692 @cindex call dummy stack unwinding
16693 Set unwinding of the stack if a signal is received while in a function
16694 that @value{GDBN} called in the program being debugged. If set to on,
16695 @value{GDBN} unwinds the stack it created for the call and restores
16696 the context to what it was before the call. If set to off (the
16697 default), @value{GDBN} stops in the frame where the signal was
16700 @item show unwindonsignal
16701 @kindex show unwindonsignal
16702 Show the current setting of stack unwinding in the functions called by
16705 @item set unwind-on-terminating-exception
16706 @kindex set unwind-on-terminating-exception
16707 @cindex unwind stack in called functions with unhandled exceptions
16708 @cindex call dummy stack unwinding on unhandled exception.
16709 Set unwinding of the stack if a C@t{++} exception is raised, but left
16710 unhandled while in a function that @value{GDBN} called in the program being
16711 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16712 it created for the call and restores the context to what it was before
16713 the call. If set to off, @value{GDBN} the exception is delivered to
16714 the default C@t{++} exception handler and the inferior terminated.
16716 @item show unwind-on-terminating-exception
16717 @kindex show unwind-on-terminating-exception
16718 Show the current setting of stack unwinding in the functions called by
16723 @cindex weak alias functions
16724 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16725 for another function. In such case, @value{GDBN} might not pick up
16726 the type information, including the types of the function arguments,
16727 which causes @value{GDBN} to call the inferior function incorrectly.
16728 As a result, the called function will function erroneously and may
16729 even crash. A solution to that is to use the name of the aliased
16733 @section Patching Programs
16735 @cindex patching binaries
16736 @cindex writing into executables
16737 @cindex writing into corefiles
16739 By default, @value{GDBN} opens the file containing your program's
16740 executable code (or the corefile) read-only. This prevents accidental
16741 alterations to machine code; but it also prevents you from intentionally
16742 patching your program's binary.
16744 If you'd like to be able to patch the binary, you can specify that
16745 explicitly with the @code{set write} command. For example, you might
16746 want to turn on internal debugging flags, or even to make emergency
16752 @itemx set write off
16753 If you specify @samp{set write on}, @value{GDBN} opens executable and
16754 core files for both reading and writing; if you specify @kbd{set write
16755 off} (the default), @value{GDBN} opens them read-only.
16757 If you have already loaded a file, you must load it again (using the
16758 @code{exec-file} or @code{core-file} command) after changing @code{set
16759 write}, for your new setting to take effect.
16763 Display whether executable files and core files are opened for writing
16764 as well as reading.
16768 @chapter @value{GDBN} Files
16770 @value{GDBN} needs to know the file name of the program to be debugged,
16771 both in order to read its symbol table and in order to start your
16772 program. To debug a core dump of a previous run, you must also tell
16773 @value{GDBN} the name of the core dump file.
16776 * Files:: Commands to specify files
16777 * Separate Debug Files:: Debugging information in separate files
16778 * MiniDebugInfo:: Debugging information in a special section
16779 * Index Files:: Index files speed up GDB
16780 * Symbol Errors:: Errors reading symbol files
16781 * Data Files:: GDB data files
16785 @section Commands to Specify Files
16787 @cindex symbol table
16788 @cindex core dump file
16790 You may want to specify executable and core dump file names. The usual
16791 way to do this is at start-up time, using the arguments to
16792 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16793 Out of @value{GDBN}}).
16795 Occasionally it is necessary to change to a different file during a
16796 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16797 specify a file you want to use. Or you are debugging a remote target
16798 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16799 Program}). In these situations the @value{GDBN} commands to specify
16800 new files are useful.
16803 @cindex executable file
16805 @item file @var{filename}
16806 Use @var{filename} as the program to be debugged. It is read for its
16807 symbols and for the contents of pure memory. It is also the program
16808 executed when you use the @code{run} command. If you do not specify a
16809 directory and the file is not found in the @value{GDBN} working directory,
16810 @value{GDBN} uses the environment variable @code{PATH} as a list of
16811 directories to search, just as the shell does when looking for a program
16812 to run. You can change the value of this variable, for both @value{GDBN}
16813 and your program, using the @code{path} command.
16815 @cindex unlinked object files
16816 @cindex patching object files
16817 You can load unlinked object @file{.o} files into @value{GDBN} using
16818 the @code{file} command. You will not be able to ``run'' an object
16819 file, but you can disassemble functions and inspect variables. Also,
16820 if the underlying BFD functionality supports it, you could use
16821 @kbd{gdb -write} to patch object files using this technique. Note
16822 that @value{GDBN} can neither interpret nor modify relocations in this
16823 case, so branches and some initialized variables will appear to go to
16824 the wrong place. But this feature is still handy from time to time.
16827 @code{file} with no argument makes @value{GDBN} discard any information it
16828 has on both executable file and the symbol table.
16831 @item exec-file @r{[} @var{filename} @r{]}
16832 Specify that the program to be run (but not the symbol table) is found
16833 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16834 if necessary to locate your program. Omitting @var{filename} means to
16835 discard information on the executable file.
16837 @kindex symbol-file
16838 @item symbol-file @r{[} @var{filename} @r{]}
16839 Read symbol table information from file @var{filename}. @code{PATH} is
16840 searched when necessary. Use the @code{file} command to get both symbol
16841 table and program to run from the same file.
16843 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16844 program's symbol table.
16846 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16847 some breakpoints and auto-display expressions. This is because they may
16848 contain pointers to the internal data recording symbols and data types,
16849 which are part of the old symbol table data being discarded inside
16852 @code{symbol-file} does not repeat if you press @key{RET} again after
16855 When @value{GDBN} is configured for a particular environment, it
16856 understands debugging information in whatever format is the standard
16857 generated for that environment; you may use either a @sc{gnu} compiler, or
16858 other compilers that adhere to the local conventions.
16859 Best results are usually obtained from @sc{gnu} compilers; for example,
16860 using @code{@value{NGCC}} you can generate debugging information for
16863 For most kinds of object files, with the exception of old SVR3 systems
16864 using COFF, the @code{symbol-file} command does not normally read the
16865 symbol table in full right away. Instead, it scans the symbol table
16866 quickly to find which source files and which symbols are present. The
16867 details are read later, one source file at a time, as they are needed.
16869 The purpose of this two-stage reading strategy is to make @value{GDBN}
16870 start up faster. For the most part, it is invisible except for
16871 occasional pauses while the symbol table details for a particular source
16872 file are being read. (The @code{set verbose} command can turn these
16873 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16874 Warnings and Messages}.)
16876 We have not implemented the two-stage strategy for COFF yet. When the
16877 symbol table is stored in COFF format, @code{symbol-file} reads the
16878 symbol table data in full right away. Note that ``stabs-in-COFF''
16879 still does the two-stage strategy, since the debug info is actually
16883 @cindex reading symbols immediately
16884 @cindex symbols, reading immediately
16885 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16886 @itemx file @r{[} -readnow @r{]} @var{filename}
16887 You can override the @value{GDBN} two-stage strategy for reading symbol
16888 tables by using the @samp{-readnow} option with any of the commands that
16889 load symbol table information, if you want to be sure @value{GDBN} has the
16890 entire symbol table available.
16892 @c FIXME: for now no mention of directories, since this seems to be in
16893 @c flux. 13mar1992 status is that in theory GDB would look either in
16894 @c current dir or in same dir as myprog; but issues like competing
16895 @c GDB's, or clutter in system dirs, mean that in practice right now
16896 @c only current dir is used. FFish says maybe a special GDB hierarchy
16897 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16901 @item core-file @r{[}@var{filename}@r{]}
16903 Specify the whereabouts of a core dump file to be used as the ``contents
16904 of memory''. Traditionally, core files contain only some parts of the
16905 address space of the process that generated them; @value{GDBN} can access the
16906 executable file itself for other parts.
16908 @code{core-file} with no argument specifies that no core file is
16911 Note that the core file is ignored when your program is actually running
16912 under @value{GDBN}. So, if you have been running your program and you
16913 wish to debug a core file instead, you must kill the subprocess in which
16914 the program is running. To do this, use the @code{kill} command
16915 (@pxref{Kill Process, ,Killing the Child Process}).
16917 @kindex add-symbol-file
16918 @cindex dynamic linking
16919 @item add-symbol-file @var{filename} @var{address}
16920 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16921 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16922 The @code{add-symbol-file} command reads additional symbol table
16923 information from the file @var{filename}. You would use this command
16924 when @var{filename} has been dynamically loaded (by some other means)
16925 into the program that is running. The @var{address} should give the memory
16926 address at which the file has been loaded; @value{GDBN} cannot figure
16927 this out for itself. You can additionally specify an arbitrary number
16928 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16929 section name and base address for that section. You can specify any
16930 @var{address} as an expression.
16932 The symbol table of the file @var{filename} is added to the symbol table
16933 originally read with the @code{symbol-file} command. You can use the
16934 @code{add-symbol-file} command any number of times; the new symbol data
16935 thus read is kept in addition to the old.
16937 Changes can be reverted using the command @code{remove-symbol-file}.
16939 @cindex relocatable object files, reading symbols from
16940 @cindex object files, relocatable, reading symbols from
16941 @cindex reading symbols from relocatable object files
16942 @cindex symbols, reading from relocatable object files
16943 @cindex @file{.o} files, reading symbols from
16944 Although @var{filename} is typically a shared library file, an
16945 executable file, or some other object file which has been fully
16946 relocated for loading into a process, you can also load symbolic
16947 information from relocatable @file{.o} files, as long as:
16951 the file's symbolic information refers only to linker symbols defined in
16952 that file, not to symbols defined by other object files,
16954 every section the file's symbolic information refers to has actually
16955 been loaded into the inferior, as it appears in the file, and
16957 you can determine the address at which every section was loaded, and
16958 provide these to the @code{add-symbol-file} command.
16962 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16963 relocatable files into an already running program; such systems
16964 typically make the requirements above easy to meet. However, it's
16965 important to recognize that many native systems use complex link
16966 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16967 assembly, for example) that make the requirements difficult to meet. In
16968 general, one cannot assume that using @code{add-symbol-file} to read a
16969 relocatable object file's symbolic information will have the same effect
16970 as linking the relocatable object file into the program in the normal
16973 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16975 @kindex remove-symbol-file
16976 @item remove-symbol-file @var{filename}
16977 @item remove-symbol-file -a @var{address}
16978 Remove a symbol file added via the @code{add-symbol-file} command. The
16979 file to remove can be identified by its @var{filename} or by an @var{address}
16980 that lies within the boundaries of this symbol file in memory. Example:
16983 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16984 add symbol table from file "/home/user/gdb/mylib.so" at
16985 .text_addr = 0x7ffff7ff9480
16987 Reading symbols from /home/user/gdb/mylib.so...done.
16988 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16989 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16994 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16996 @kindex add-symbol-file-from-memory
16997 @cindex @code{syscall DSO}
16998 @cindex load symbols from memory
16999 @item add-symbol-file-from-memory @var{address}
17000 Load symbols from the given @var{address} in a dynamically loaded
17001 object file whose image is mapped directly into the inferior's memory.
17002 For example, the Linux kernel maps a @code{syscall DSO} into each
17003 process's address space; this DSO provides kernel-specific code for
17004 some system calls. The argument can be any expression whose
17005 evaluation yields the address of the file's shared object file header.
17006 For this command to work, you must have used @code{symbol-file} or
17007 @code{exec-file} commands in advance.
17009 @kindex add-shared-symbol-files
17011 @item add-shared-symbol-files @var{library-file}
17012 @itemx assf @var{library-file}
17013 This command is deprecated and will be removed in future versions
17014 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
17016 The @code{add-shared-symbol-files} command can currently be used only
17017 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
17018 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
17019 @value{GDBN} automatically looks for shared libraries, however if
17020 @value{GDBN} does not find yours, you can invoke
17021 @code{add-shared-symbol-files}. It takes one argument: the shared
17022 library's file name. @code{assf} is a shorthand alias for
17023 @code{add-shared-symbol-files}.
17026 @item section @var{section} @var{addr}
17027 The @code{section} command changes the base address of the named
17028 @var{section} of the exec file to @var{addr}. This can be used if the
17029 exec file does not contain section addresses, (such as in the
17030 @code{a.out} format), or when the addresses specified in the file
17031 itself are wrong. Each section must be changed separately. The
17032 @code{info files} command, described below, lists all the sections and
17036 @kindex info target
17039 @code{info files} and @code{info target} are synonymous; both print the
17040 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17041 including the names of the executable and core dump files currently in
17042 use by @value{GDBN}, and the files from which symbols were loaded. The
17043 command @code{help target} lists all possible targets rather than
17046 @kindex maint info sections
17047 @item maint info sections
17048 Another command that can give you extra information about program sections
17049 is @code{maint info sections}. In addition to the section information
17050 displayed by @code{info files}, this command displays the flags and file
17051 offset of each section in the executable and core dump files. In addition,
17052 @code{maint info sections} provides the following command options (which
17053 may be arbitrarily combined):
17057 Display sections for all loaded object files, including shared libraries.
17058 @item @var{sections}
17059 Display info only for named @var{sections}.
17060 @item @var{section-flags}
17061 Display info only for sections for which @var{section-flags} are true.
17062 The section flags that @value{GDBN} currently knows about are:
17065 Section will have space allocated in the process when loaded.
17066 Set for all sections except those containing debug information.
17068 Section will be loaded from the file into the child process memory.
17069 Set for pre-initialized code and data, clear for @code{.bss} sections.
17071 Section needs to be relocated before loading.
17073 Section cannot be modified by the child process.
17075 Section contains executable code only.
17077 Section contains data only (no executable code).
17079 Section will reside in ROM.
17081 Section contains data for constructor/destructor lists.
17083 Section is not empty.
17085 An instruction to the linker to not output the section.
17086 @item COFF_SHARED_LIBRARY
17087 A notification to the linker that the section contains
17088 COFF shared library information.
17090 Section contains common symbols.
17093 @kindex set trust-readonly-sections
17094 @cindex read-only sections
17095 @item set trust-readonly-sections on
17096 Tell @value{GDBN} that readonly sections in your object file
17097 really are read-only (i.e.@: that their contents will not change).
17098 In that case, @value{GDBN} can fetch values from these sections
17099 out of the object file, rather than from the target program.
17100 For some targets (notably embedded ones), this can be a significant
17101 enhancement to debugging performance.
17103 The default is off.
17105 @item set trust-readonly-sections off
17106 Tell @value{GDBN} not to trust readonly sections. This means that
17107 the contents of the section might change while the program is running,
17108 and must therefore be fetched from the target when needed.
17110 @item show trust-readonly-sections
17111 Show the current setting of trusting readonly sections.
17114 All file-specifying commands allow both absolute and relative file names
17115 as arguments. @value{GDBN} always converts the file name to an absolute file
17116 name and remembers it that way.
17118 @cindex shared libraries
17119 @anchor{Shared Libraries}
17120 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17121 and IBM RS/6000 AIX shared libraries.
17123 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17124 shared libraries. @xref{Expat}.
17126 @value{GDBN} automatically loads symbol definitions from shared libraries
17127 when you use the @code{run} command, or when you examine a core file.
17128 (Before you issue the @code{run} command, @value{GDBN} does not understand
17129 references to a function in a shared library, however---unless you are
17130 debugging a core file).
17132 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17133 automatically loads the symbols at the time of the @code{shl_load} call.
17135 @c FIXME: some @value{GDBN} release may permit some refs to undef
17136 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17137 @c FIXME...lib; check this from time to time when updating manual
17139 There are times, however, when you may wish to not automatically load
17140 symbol definitions from shared libraries, such as when they are
17141 particularly large or there are many of them.
17143 To control the automatic loading of shared library symbols, use the
17147 @kindex set auto-solib-add
17148 @item set auto-solib-add @var{mode}
17149 If @var{mode} is @code{on}, symbols from all shared object libraries
17150 will be loaded automatically when the inferior begins execution, you
17151 attach to an independently started inferior, or when the dynamic linker
17152 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17153 is @code{off}, symbols must be loaded manually, using the
17154 @code{sharedlibrary} command. The default value is @code{on}.
17156 @cindex memory used for symbol tables
17157 If your program uses lots of shared libraries with debug info that
17158 takes large amounts of memory, you can decrease the @value{GDBN}
17159 memory footprint by preventing it from automatically loading the
17160 symbols from shared libraries. To that end, type @kbd{set
17161 auto-solib-add off} before running the inferior, then load each
17162 library whose debug symbols you do need with @kbd{sharedlibrary
17163 @var{regexp}}, where @var{regexp} is a regular expression that matches
17164 the libraries whose symbols you want to be loaded.
17166 @kindex show auto-solib-add
17167 @item show auto-solib-add
17168 Display the current autoloading mode.
17171 @cindex load shared library
17172 To explicitly load shared library symbols, use the @code{sharedlibrary}
17176 @kindex info sharedlibrary
17178 @item info share @var{regex}
17179 @itemx info sharedlibrary @var{regex}
17180 Print the names of the shared libraries which are currently loaded
17181 that match @var{regex}. If @var{regex} is omitted then print
17182 all shared libraries that are loaded.
17184 @kindex sharedlibrary
17186 @item sharedlibrary @var{regex}
17187 @itemx share @var{regex}
17188 Load shared object library symbols for files matching a
17189 Unix regular expression.
17190 As with files loaded automatically, it only loads shared libraries
17191 required by your program for a core file or after typing @code{run}. If
17192 @var{regex} is omitted all shared libraries required by your program are
17195 @item nosharedlibrary
17196 @kindex nosharedlibrary
17197 @cindex unload symbols from shared libraries
17198 Unload all shared object library symbols. This discards all symbols
17199 that have been loaded from all shared libraries. Symbols from shared
17200 libraries that were loaded by explicit user requests are not
17204 Sometimes you may wish that @value{GDBN} stops and gives you control
17205 when any of shared library events happen. The best way to do this is
17206 to use @code{catch load} and @code{catch unload} (@pxref{Set
17209 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17210 command for this. This command exists for historical reasons. It is
17211 less useful than setting a catchpoint, because it does not allow for
17212 conditions or commands as a catchpoint does.
17215 @item set stop-on-solib-events
17216 @kindex set stop-on-solib-events
17217 This command controls whether @value{GDBN} should give you control
17218 when the dynamic linker notifies it about some shared library event.
17219 The most common event of interest is loading or unloading of a new
17222 @item show stop-on-solib-events
17223 @kindex show stop-on-solib-events
17224 Show whether @value{GDBN} stops and gives you control when shared
17225 library events happen.
17228 Shared libraries are also supported in many cross or remote debugging
17229 configurations. @value{GDBN} needs to have access to the target's libraries;
17230 this can be accomplished either by providing copies of the libraries
17231 on the host system, or by asking @value{GDBN} to automatically retrieve the
17232 libraries from the target. If copies of the target libraries are
17233 provided, they need to be the same as the target libraries, although the
17234 copies on the target can be stripped as long as the copies on the host are
17237 @cindex where to look for shared libraries
17238 For remote debugging, you need to tell @value{GDBN} where the target
17239 libraries are, so that it can load the correct copies---otherwise, it
17240 may try to load the host's libraries. @value{GDBN} has two variables
17241 to specify the search directories for target libraries.
17244 @cindex prefix for shared library file names
17245 @cindex system root, alternate
17246 @kindex set solib-absolute-prefix
17247 @kindex set sysroot
17248 @item set sysroot @var{path}
17249 Use @var{path} as the system root for the program being debugged. Any
17250 absolute shared library paths will be prefixed with @var{path}; many
17251 runtime loaders store the absolute paths to the shared library in the
17252 target program's memory. If you use @code{set sysroot} to find shared
17253 libraries, they need to be laid out in the same way that they are on
17254 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17257 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17258 retrieve the target libraries from the remote system. This is only
17259 supported when using a remote target that supports the @code{remote get}
17260 command (@pxref{File Transfer,,Sending files to a remote system}).
17261 The part of @var{path} following the initial @file{remote:}
17262 (if present) is used as system root prefix on the remote file system.
17263 @footnote{If you want to specify a local system root using a directory
17264 that happens to be named @file{remote:}, you need to use some equivalent
17265 variant of the name like @file{./remote:}.}
17267 For targets with an MS-DOS based filesystem, such as MS-Windows and
17268 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17269 absolute file name with @var{path}. But first, on Unix hosts,
17270 @value{GDBN} converts all backslash directory separators into forward
17271 slashes, because the backslash is not a directory separator on Unix:
17274 c:\foo\bar.dll @result{} c:/foo/bar.dll
17277 Then, @value{GDBN} attempts prefixing the target file name with
17278 @var{path}, and looks for the resulting file name in the host file
17282 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17285 If that does not find the shared library, @value{GDBN} tries removing
17286 the @samp{:} character from the drive spec, both for convenience, and,
17287 for the case of the host file system not supporting file names with
17291 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17294 This makes it possible to have a system root that mirrors a target
17295 with more than one drive. E.g., you may want to setup your local
17296 copies of the target system shared libraries like so (note @samp{c} vs
17300 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17301 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17302 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17306 and point the system root at @file{/path/to/sysroot}, so that
17307 @value{GDBN} can find the correct copies of both
17308 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17310 If that still does not find the shared library, @value{GDBN} tries
17311 removing the whole drive spec from the target file name:
17314 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17317 This last lookup makes it possible to not care about the drive name,
17318 if you don't want or need to.
17320 The @code{set solib-absolute-prefix} command is an alias for @code{set
17323 @cindex default system root
17324 @cindex @samp{--with-sysroot}
17325 You can set the default system root by using the configure-time
17326 @samp{--with-sysroot} option. If the system root is inside
17327 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17328 @samp{--exec-prefix}), then the default system root will be updated
17329 automatically if the installed @value{GDBN} is moved to a new
17332 @kindex show sysroot
17334 Display the current shared library prefix.
17336 @kindex set solib-search-path
17337 @item set solib-search-path @var{path}
17338 If this variable is set, @var{path} is a colon-separated list of
17339 directories to search for shared libraries. @samp{solib-search-path}
17340 is used after @samp{sysroot} fails to locate the library, or if the
17341 path to the library is relative instead of absolute. If you want to
17342 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17343 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17344 finding your host's libraries. @samp{sysroot} is preferred; setting
17345 it to a nonexistent directory may interfere with automatic loading
17346 of shared library symbols.
17348 @kindex show solib-search-path
17349 @item show solib-search-path
17350 Display the current shared library search path.
17352 @cindex DOS file-name semantics of file names.
17353 @kindex set target-file-system-kind (unix|dos-based|auto)
17354 @kindex show target-file-system-kind
17355 @item set target-file-system-kind @var{kind}
17356 Set assumed file system kind for target reported file names.
17358 Shared library file names as reported by the target system may not
17359 make sense as is on the system @value{GDBN} is running on. For
17360 example, when remote debugging a target that has MS-DOS based file
17361 system semantics, from a Unix host, the target may be reporting to
17362 @value{GDBN} a list of loaded shared libraries with file names such as
17363 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17364 drive letters, so the @samp{c:\} prefix is not normally understood as
17365 indicating an absolute file name, and neither is the backslash
17366 normally considered a directory separator character. In that case,
17367 the native file system would interpret this whole absolute file name
17368 as a relative file name with no directory components. This would make
17369 it impossible to point @value{GDBN} at a copy of the remote target's
17370 shared libraries on the host using @code{set sysroot}, and impractical
17371 with @code{set solib-search-path}. Setting
17372 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17373 to interpret such file names similarly to how the target would, and to
17374 map them to file names valid on @value{GDBN}'s native file system
17375 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17376 to one of the supported file system kinds. In that case, @value{GDBN}
17377 tries to determine the appropriate file system variant based on the
17378 current target's operating system (@pxref{ABI, ,Configuring the
17379 Current ABI}). The supported file system settings are:
17383 Instruct @value{GDBN} to assume the target file system is of Unix
17384 kind. Only file names starting the forward slash (@samp{/}) character
17385 are considered absolute, and the directory separator character is also
17389 Instruct @value{GDBN} to assume the target file system is DOS based.
17390 File names starting with either a forward slash, or a drive letter
17391 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17392 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17393 considered directory separators.
17396 Instruct @value{GDBN} to use the file system kind associated with the
17397 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17398 This is the default.
17402 @cindex file name canonicalization
17403 @cindex base name differences
17404 When processing file names provided by the user, @value{GDBN}
17405 frequently needs to compare them to the file names recorded in the
17406 program's debug info. Normally, @value{GDBN} compares just the
17407 @dfn{base names} of the files as strings, which is reasonably fast
17408 even for very large programs. (The base name of a file is the last
17409 portion of its name, after stripping all the leading directories.)
17410 This shortcut in comparison is based upon the assumption that files
17411 cannot have more than one base name. This is usually true, but
17412 references to files that use symlinks or similar filesystem
17413 facilities violate that assumption. If your program records files
17414 using such facilities, or if you provide file names to @value{GDBN}
17415 using symlinks etc., you can set @code{basenames-may-differ} to
17416 @code{true} to instruct @value{GDBN} to completely canonicalize each
17417 pair of file names it needs to compare. This will make file-name
17418 comparisons accurate, but at a price of a significant slowdown.
17421 @item set basenames-may-differ
17422 @kindex set basenames-may-differ
17423 Set whether a source file may have multiple base names.
17425 @item show basenames-may-differ
17426 @kindex show basenames-may-differ
17427 Show whether a source file may have multiple base names.
17430 @node Separate Debug Files
17431 @section Debugging Information in Separate Files
17432 @cindex separate debugging information files
17433 @cindex debugging information in separate files
17434 @cindex @file{.debug} subdirectories
17435 @cindex debugging information directory, global
17436 @cindex global debugging information directories
17437 @cindex build ID, and separate debugging files
17438 @cindex @file{.build-id} directory
17440 @value{GDBN} allows you to put a program's debugging information in a
17441 file separate from the executable itself, in a way that allows
17442 @value{GDBN} to find and load the debugging information automatically.
17443 Since debugging information can be very large---sometimes larger
17444 than the executable code itself---some systems distribute debugging
17445 information for their executables in separate files, which users can
17446 install only when they need to debug a problem.
17448 @value{GDBN} supports two ways of specifying the separate debug info
17453 The executable contains a @dfn{debug link} that specifies the name of
17454 the separate debug info file. The separate debug file's name is
17455 usually @file{@var{executable}.debug}, where @var{executable} is the
17456 name of the corresponding executable file without leading directories
17457 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17458 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17459 checksum for the debug file, which @value{GDBN} uses to validate that
17460 the executable and the debug file came from the same build.
17463 The executable contains a @dfn{build ID}, a unique bit string that is
17464 also present in the corresponding debug info file. (This is supported
17465 only on some operating systems, notably those which use the ELF format
17466 for binary files and the @sc{gnu} Binutils.) For more details about
17467 this feature, see the description of the @option{--build-id}
17468 command-line option in @ref{Options, , Command Line Options, ld.info,
17469 The GNU Linker}. The debug info file's name is not specified
17470 explicitly by the build ID, but can be computed from the build ID, see
17474 Depending on the way the debug info file is specified, @value{GDBN}
17475 uses two different methods of looking for the debug file:
17479 For the ``debug link'' method, @value{GDBN} looks up the named file in
17480 the directory of the executable file, then in a subdirectory of that
17481 directory named @file{.debug}, and finally under each one of the global debug
17482 directories, in a subdirectory whose name is identical to the leading
17483 directories of the executable's absolute file name.
17486 For the ``build ID'' method, @value{GDBN} looks in the
17487 @file{.build-id} subdirectory of each one of the global debug directories for
17488 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17489 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17490 are the rest of the bit string. (Real build ID strings are 32 or more
17491 hex characters, not 10.)
17494 So, for example, suppose you ask @value{GDBN} to debug
17495 @file{/usr/bin/ls}, which has a debug link that specifies the
17496 file @file{ls.debug}, and a build ID whose value in hex is
17497 @code{abcdef1234}. If the list of the global debug directories includes
17498 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17499 debug information files, in the indicated order:
17503 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17505 @file{/usr/bin/ls.debug}
17507 @file{/usr/bin/.debug/ls.debug}
17509 @file{/usr/lib/debug/usr/bin/ls.debug}.
17512 @anchor{debug-file-directory}
17513 Global debugging info directories default to what is set by @value{GDBN}
17514 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17515 you can also set the global debugging info directories, and view the list
17516 @value{GDBN} is currently using.
17520 @kindex set debug-file-directory
17521 @item set debug-file-directory @var{directories}
17522 Set the directories which @value{GDBN} searches for separate debugging
17523 information files to @var{directory}. Multiple path components can be set
17524 concatenating them by a path separator.
17526 @kindex show debug-file-directory
17527 @item show debug-file-directory
17528 Show the directories @value{GDBN} searches for separate debugging
17533 @cindex @code{.gnu_debuglink} sections
17534 @cindex debug link sections
17535 A debug link is a special section of the executable file named
17536 @code{.gnu_debuglink}. The section must contain:
17540 A filename, with any leading directory components removed, followed by
17543 zero to three bytes of padding, as needed to reach the next four-byte
17544 boundary within the section, and
17546 a four-byte CRC checksum, stored in the same endianness used for the
17547 executable file itself. The checksum is computed on the debugging
17548 information file's full contents by the function given below, passing
17549 zero as the @var{crc} argument.
17552 Any executable file format can carry a debug link, as long as it can
17553 contain a section named @code{.gnu_debuglink} with the contents
17556 @cindex @code{.note.gnu.build-id} sections
17557 @cindex build ID sections
17558 The build ID is a special section in the executable file (and in other
17559 ELF binary files that @value{GDBN} may consider). This section is
17560 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17561 It contains unique identification for the built files---the ID remains
17562 the same across multiple builds of the same build tree. The default
17563 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17564 content for the build ID string. The same section with an identical
17565 value is present in the original built binary with symbols, in its
17566 stripped variant, and in the separate debugging information file.
17568 The debugging information file itself should be an ordinary
17569 executable, containing a full set of linker symbols, sections, and
17570 debugging information. The sections of the debugging information file
17571 should have the same names, addresses, and sizes as the original file,
17572 but they need not contain any data---much like a @code{.bss} section
17573 in an ordinary executable.
17575 The @sc{gnu} binary utilities (Binutils) package includes the
17576 @samp{objcopy} utility that can produce
17577 the separated executable / debugging information file pairs using the
17578 following commands:
17581 @kbd{objcopy --only-keep-debug foo foo.debug}
17586 These commands remove the debugging
17587 information from the executable file @file{foo} and place it in the file
17588 @file{foo.debug}. You can use the first, second or both methods to link the
17593 The debug link method needs the following additional command to also leave
17594 behind a debug link in @file{foo}:
17597 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17600 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17601 a version of the @code{strip} command such that the command @kbd{strip foo -f
17602 foo.debug} has the same functionality as the two @code{objcopy} commands and
17603 the @code{ln -s} command above, together.
17606 Build ID gets embedded into the main executable using @code{ld --build-id} or
17607 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17608 compatibility fixes for debug files separation are present in @sc{gnu} binary
17609 utilities (Binutils) package since version 2.18.
17614 @cindex CRC algorithm definition
17615 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17616 IEEE 802.3 using the polynomial:
17618 @c TexInfo requires naked braces for multi-digit exponents for Tex
17619 @c output, but this causes HTML output to barf. HTML has to be set using
17620 @c raw commands. So we end up having to specify this equation in 2
17625 <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>
17626 + <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
17632 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17633 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17637 The function is computed byte at a time, taking the least
17638 significant bit of each byte first. The initial pattern
17639 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17640 the final result is inverted to ensure trailing zeros also affect the
17643 @emph{Note:} This is the same CRC polynomial as used in handling the
17644 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
17645 However in the case of the Remote Serial Protocol, the CRC is computed
17646 @emph{most} significant bit first, and the result is not inverted, so
17647 trailing zeros have no effect on the CRC value.
17649 To complete the description, we show below the code of the function
17650 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17651 initially supplied @code{crc} argument means that an initial call to
17652 this function passing in zero will start computing the CRC using
17655 @kindex gnu_debuglink_crc32
17658 gnu_debuglink_crc32 (unsigned long crc,
17659 unsigned char *buf, size_t len)
17661 static const unsigned long crc32_table[256] =
17663 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17664 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17665 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17666 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17667 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17668 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17669 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17670 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17671 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17672 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17673 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17674 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17675 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17676 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17677 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17678 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17679 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17680 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17681 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17682 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17683 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17684 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17685 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17686 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17687 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17688 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17689 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17690 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17691 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17692 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17693 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17694 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17695 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17696 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17697 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17698 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17699 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17700 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17701 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17702 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17703 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17704 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17705 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17706 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17707 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17708 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17709 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17710 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17711 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17712 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17713 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17716 unsigned char *end;
17718 crc = ~crc & 0xffffffff;
17719 for (end = buf + len; buf < end; ++buf)
17720 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17721 return ~crc & 0xffffffff;
17726 This computation does not apply to the ``build ID'' method.
17728 @node MiniDebugInfo
17729 @section Debugging information in a special section
17730 @cindex separate debug sections
17731 @cindex @samp{.gnu_debugdata} section
17733 Some systems ship pre-built executables and libraries that have a
17734 special @samp{.gnu_debugdata} section. This feature is called
17735 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17736 is used to supply extra symbols for backtraces.
17738 The intent of this section is to provide extra minimal debugging
17739 information for use in simple backtraces. It is not intended to be a
17740 replacement for full separate debugging information (@pxref{Separate
17741 Debug Files}). The example below shows the intended use; however,
17742 @value{GDBN} does not currently put restrictions on what sort of
17743 debugging information might be included in the section.
17745 @value{GDBN} has support for this extension. If the section exists,
17746 then it is used provided that no other source of debugging information
17747 can be found, and that @value{GDBN} was configured with LZMA support.
17749 This section can be easily created using @command{objcopy} and other
17750 standard utilities:
17753 # Extract the dynamic symbols from the main binary, there is no need
17754 # to also have these in the normal symbol table.
17755 nm -D @var{binary} --format=posix --defined-only \
17756 | awk '@{ print $1 @}' | sort > dynsyms
17758 # Extract all the text (i.e. function) symbols from the debuginfo.
17759 # (Note that we actually also accept "D" symbols, for the benefit
17760 # of platforms like PowerPC64 that use function descriptors.)
17761 nm @var{binary} --format=posix --defined-only \
17762 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17765 # Keep all the function symbols not already in the dynamic symbol
17767 comm -13 dynsyms funcsyms > keep_symbols
17769 # Separate full debug info into debug binary.
17770 objcopy --only-keep-debug @var{binary} debug
17772 # Copy the full debuginfo, keeping only a minimal set of symbols and
17773 # removing some unnecessary sections.
17774 objcopy -S --remove-section .gdb_index --remove-section .comment \
17775 --keep-symbols=keep_symbols debug mini_debuginfo
17777 # Drop the full debug info from the original binary.
17778 strip --strip-all -R .comment @var{binary}
17780 # Inject the compressed data into the .gnu_debugdata section of the
17783 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17787 @section Index Files Speed Up @value{GDBN}
17788 @cindex index files
17789 @cindex @samp{.gdb_index} section
17791 When @value{GDBN} finds a symbol file, it scans the symbols in the
17792 file in order to construct an internal symbol table. This lets most
17793 @value{GDBN} operations work quickly---at the cost of a delay early
17794 on. For large programs, this delay can be quite lengthy, so
17795 @value{GDBN} provides a way to build an index, which speeds up
17798 The index is stored as a section in the symbol file. @value{GDBN} can
17799 write the index to a file, then you can put it into the symbol file
17800 using @command{objcopy}.
17802 To create an index file, use the @code{save gdb-index} command:
17805 @item save gdb-index @var{directory}
17806 @kindex save gdb-index
17807 Create an index file for each symbol file currently known by
17808 @value{GDBN}. Each file is named after its corresponding symbol file,
17809 with @samp{.gdb-index} appended, and is written into the given
17813 Once you have created an index file you can merge it into your symbol
17814 file, here named @file{symfile}, using @command{objcopy}:
17817 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17818 --set-section-flags .gdb_index=readonly symfile symfile
17821 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17822 sections that have been deprecated. Usually they are deprecated because
17823 they are missing a new feature or have performance issues.
17824 To tell @value{GDBN} to use a deprecated index section anyway
17825 specify @code{set use-deprecated-index-sections on}.
17826 The default is @code{off}.
17827 This can speed up startup, but may result in some functionality being lost.
17828 @xref{Index Section Format}.
17830 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17831 must be done before gdb reads the file. The following will not work:
17834 $ gdb -ex "set use-deprecated-index-sections on" <program>
17837 Instead you must do, for example,
17840 $ gdb -iex "set use-deprecated-index-sections on" <program>
17843 There are currently some limitation on indices. They only work when
17844 for DWARF debugging information, not stabs. And, they do not
17845 currently work for programs using Ada.
17847 @node Symbol Errors
17848 @section Errors Reading Symbol Files
17850 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17851 such as symbol types it does not recognize, or known bugs in compiler
17852 output. By default, @value{GDBN} does not notify you of such problems, since
17853 they are relatively common and primarily of interest to people
17854 debugging compilers. If you are interested in seeing information
17855 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17856 only one message about each such type of problem, no matter how many
17857 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17858 to see how many times the problems occur, with the @code{set
17859 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17862 The messages currently printed, and their meanings, include:
17865 @item inner block not inside outer block in @var{symbol}
17867 The symbol information shows where symbol scopes begin and end
17868 (such as at the start of a function or a block of statements). This
17869 error indicates that an inner scope block is not fully contained
17870 in its outer scope blocks.
17872 @value{GDBN} circumvents the problem by treating the inner block as if it had
17873 the same scope as the outer block. In the error message, @var{symbol}
17874 may be shown as ``@code{(don't know)}'' if the outer block is not a
17877 @item block at @var{address} out of order
17879 The symbol information for symbol scope blocks should occur in
17880 order of increasing addresses. This error indicates that it does not
17883 @value{GDBN} does not circumvent this problem, and has trouble
17884 locating symbols in the source file whose symbols it is reading. (You
17885 can often determine what source file is affected by specifying
17886 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17889 @item bad block start address patched
17891 The symbol information for a symbol scope block has a start address
17892 smaller than the address of the preceding source line. This is known
17893 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17895 @value{GDBN} circumvents the problem by treating the symbol scope block as
17896 starting on the previous source line.
17898 @item bad string table offset in symbol @var{n}
17901 Symbol number @var{n} contains a pointer into the string table which is
17902 larger than the size of the string table.
17904 @value{GDBN} circumvents the problem by considering the symbol to have the
17905 name @code{foo}, which may cause other problems if many symbols end up
17908 @item unknown symbol type @code{0x@var{nn}}
17910 The symbol information contains new data types that @value{GDBN} does
17911 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17912 uncomprehended information, in hexadecimal.
17914 @value{GDBN} circumvents the error by ignoring this symbol information.
17915 This usually allows you to debug your program, though certain symbols
17916 are not accessible. If you encounter such a problem and feel like
17917 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17918 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17919 and examine @code{*bufp} to see the symbol.
17921 @item stub type has NULL name
17923 @value{GDBN} could not find the full definition for a struct or class.
17925 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17926 The symbol information for a C@t{++} member function is missing some
17927 information that recent versions of the compiler should have output for
17930 @item info mismatch between compiler and debugger
17932 @value{GDBN} could not parse a type specification output by the compiler.
17937 @section GDB Data Files
17939 @cindex prefix for data files
17940 @value{GDBN} will sometimes read an auxiliary data file. These files
17941 are kept in a directory known as the @dfn{data directory}.
17943 You can set the data directory's name, and view the name @value{GDBN}
17944 is currently using.
17947 @kindex set data-directory
17948 @item set data-directory @var{directory}
17949 Set the directory which @value{GDBN} searches for auxiliary data files
17950 to @var{directory}.
17952 @kindex show data-directory
17953 @item show data-directory
17954 Show the directory @value{GDBN} searches for auxiliary data files.
17957 @cindex default data directory
17958 @cindex @samp{--with-gdb-datadir}
17959 You can set the default data directory by using the configure-time
17960 @samp{--with-gdb-datadir} option. If the data directory is inside
17961 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17962 @samp{--exec-prefix}), then the default data directory will be updated
17963 automatically if the installed @value{GDBN} is moved to a new
17966 The data directory may also be specified with the
17967 @code{--data-directory} command line option.
17968 @xref{Mode Options}.
17971 @chapter Specifying a Debugging Target
17973 @cindex debugging target
17974 A @dfn{target} is the execution environment occupied by your program.
17976 Often, @value{GDBN} runs in the same host environment as your program;
17977 in that case, the debugging target is specified as a side effect when
17978 you use the @code{file} or @code{core} commands. When you need more
17979 flexibility---for example, running @value{GDBN} on a physically separate
17980 host, or controlling a standalone system over a serial port or a
17981 realtime system over a TCP/IP connection---you can use the @code{target}
17982 command to specify one of the target types configured for @value{GDBN}
17983 (@pxref{Target Commands, ,Commands for Managing Targets}).
17985 @cindex target architecture
17986 It is possible to build @value{GDBN} for several different @dfn{target
17987 architectures}. When @value{GDBN} is built like that, you can choose
17988 one of the available architectures with the @kbd{set architecture}
17992 @kindex set architecture
17993 @kindex show architecture
17994 @item set architecture @var{arch}
17995 This command sets the current target architecture to @var{arch}. The
17996 value of @var{arch} can be @code{"auto"}, in addition to one of the
17997 supported architectures.
17999 @item show architecture
18000 Show the current target architecture.
18002 @item set processor
18004 @kindex set processor
18005 @kindex show processor
18006 These are alias commands for, respectively, @code{set architecture}
18007 and @code{show architecture}.
18011 * Active Targets:: Active targets
18012 * Target Commands:: Commands for managing targets
18013 * Byte Order:: Choosing target byte order
18016 @node Active Targets
18017 @section Active Targets
18019 @cindex stacking targets
18020 @cindex active targets
18021 @cindex multiple targets
18023 There are multiple classes of targets such as: processes, executable files or
18024 recording sessions. Core files belong to the process class, making core file
18025 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18026 on multiple active targets, one in each class. This allows you to (for
18027 example) start a process and inspect its activity, while still having access to
18028 the executable file after the process finishes. Or if you start process
18029 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18030 presented a virtual layer of the recording target, while the process target
18031 remains stopped at the chronologically last point of the process execution.
18033 Use the @code{core-file} and @code{exec-file} commands to select a new core
18034 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18035 specify as a target a process that is already running, use the @code{attach}
18036 command (@pxref{Attach, ,Debugging an Already-running Process}).
18038 @node Target Commands
18039 @section Commands for Managing Targets
18042 @item target @var{type} @var{parameters}
18043 Connects the @value{GDBN} host environment to a target machine or
18044 process. A target is typically a protocol for talking to debugging
18045 facilities. You use the argument @var{type} to specify the type or
18046 protocol of the target machine.
18048 Further @var{parameters} are interpreted by the target protocol, but
18049 typically include things like device names or host names to connect
18050 with, process numbers, and baud rates.
18052 The @code{target} command does not repeat if you press @key{RET} again
18053 after executing the command.
18055 @kindex help target
18057 Displays the names of all targets available. To display targets
18058 currently selected, use either @code{info target} or @code{info files}
18059 (@pxref{Files, ,Commands to Specify Files}).
18061 @item help target @var{name}
18062 Describe a particular target, including any parameters necessary to
18065 @kindex set gnutarget
18066 @item set gnutarget @var{args}
18067 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18068 knows whether it is reading an @dfn{executable},
18069 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18070 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18071 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18074 @emph{Warning:} To specify a file format with @code{set gnutarget},
18075 you must know the actual BFD name.
18079 @xref{Files, , Commands to Specify Files}.
18081 @kindex show gnutarget
18082 @item show gnutarget
18083 Use the @code{show gnutarget} command to display what file format
18084 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18085 @value{GDBN} will determine the file format for each file automatically,
18086 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18089 @cindex common targets
18090 Here are some common targets (available, or not, depending on the GDB
18095 @item target exec @var{program}
18096 @cindex executable file target
18097 An executable file. @samp{target exec @var{program}} is the same as
18098 @samp{exec-file @var{program}}.
18100 @item target core @var{filename}
18101 @cindex core dump file target
18102 A core dump file. @samp{target core @var{filename}} is the same as
18103 @samp{core-file @var{filename}}.
18105 @item target remote @var{medium}
18106 @cindex remote target
18107 A remote system connected to @value{GDBN} via a serial line or network
18108 connection. This command tells @value{GDBN} to use its own remote
18109 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18111 For example, if you have a board connected to @file{/dev/ttya} on the
18112 machine running @value{GDBN}, you could say:
18115 target remote /dev/ttya
18118 @code{target remote} supports the @code{load} command. This is only
18119 useful if you have some other way of getting the stub to the target
18120 system, and you can put it somewhere in memory where it won't get
18121 clobbered by the download.
18123 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18124 @cindex built-in simulator target
18125 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18133 works; however, you cannot assume that a specific memory map, device
18134 drivers, or even basic I/O is available, although some simulators do
18135 provide these. For info about any processor-specific simulator details,
18136 see the appropriate section in @ref{Embedded Processors, ,Embedded
18139 @item target native
18140 @cindex native target
18141 Setup for local/native process debugging. Useful to make the
18142 @code{run} command spawn native processes (likewise @code{attach},
18143 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18144 (@pxref{set auto-connect-native-target}).
18148 Different targets are available on different configurations of @value{GDBN};
18149 your configuration may have more or fewer targets.
18151 Many remote targets require you to download the executable's code once
18152 you've successfully established a connection. You may wish to control
18153 various aspects of this process.
18158 @kindex set hash@r{, for remote monitors}
18159 @cindex hash mark while downloading
18160 This command controls whether a hash mark @samp{#} is displayed while
18161 downloading a file to the remote monitor. If on, a hash mark is
18162 displayed after each S-record is successfully downloaded to the
18166 @kindex show hash@r{, for remote monitors}
18167 Show the current status of displaying the hash mark.
18169 @item set debug monitor
18170 @kindex set debug monitor
18171 @cindex display remote monitor communications
18172 Enable or disable display of communications messages between
18173 @value{GDBN} and the remote monitor.
18175 @item show debug monitor
18176 @kindex show debug monitor
18177 Show the current status of displaying communications between
18178 @value{GDBN} and the remote monitor.
18183 @kindex load @var{filename}
18184 @item load @var{filename}
18186 Depending on what remote debugging facilities are configured into
18187 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18188 is meant to make @var{filename} (an executable) available for debugging
18189 on the remote system---by downloading, or dynamic linking, for example.
18190 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18191 the @code{add-symbol-file} command.
18193 If your @value{GDBN} does not have a @code{load} command, attempting to
18194 execute it gets the error message ``@code{You can't do that when your
18195 target is @dots{}}''
18197 The file is loaded at whatever address is specified in the executable.
18198 For some object file formats, you can specify the load address when you
18199 link the program; for other formats, like a.out, the object file format
18200 specifies a fixed address.
18201 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18203 Depending on the remote side capabilities, @value{GDBN} may be able to
18204 load programs into flash memory.
18206 @code{load} does not repeat if you press @key{RET} again after using it.
18210 @section Choosing Target Byte Order
18212 @cindex choosing target byte order
18213 @cindex target byte order
18215 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18216 offer the ability to run either big-endian or little-endian byte
18217 orders. Usually the executable or symbol will include a bit to
18218 designate the endian-ness, and you will not need to worry about
18219 which to use. However, you may still find it useful to adjust
18220 @value{GDBN}'s idea of processor endian-ness manually.
18224 @item set endian big
18225 Instruct @value{GDBN} to assume the target is big-endian.
18227 @item set endian little
18228 Instruct @value{GDBN} to assume the target is little-endian.
18230 @item set endian auto
18231 Instruct @value{GDBN} to use the byte order associated with the
18235 Display @value{GDBN}'s current idea of the target byte order.
18239 Note that these commands merely adjust interpretation of symbolic
18240 data on the host, and that they have absolutely no effect on the
18244 @node Remote Debugging
18245 @chapter Debugging Remote Programs
18246 @cindex remote debugging
18248 If you are trying to debug a program running on a machine that cannot run
18249 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18250 For example, you might use remote debugging on an operating system kernel,
18251 or on a small system which does not have a general purpose operating system
18252 powerful enough to run a full-featured debugger.
18254 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18255 to make this work with particular debugging targets. In addition,
18256 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18257 but not specific to any particular target system) which you can use if you
18258 write the remote stubs---the code that runs on the remote system to
18259 communicate with @value{GDBN}.
18261 Other remote targets may be available in your
18262 configuration of @value{GDBN}; use @code{help target} to list them.
18265 * Connecting:: Connecting to a remote target
18266 * File Transfer:: Sending files to a remote system
18267 * Server:: Using the gdbserver program
18268 * Remote Configuration:: Remote configuration
18269 * Remote Stub:: Implementing a remote stub
18273 @section Connecting to a Remote Target
18275 On the @value{GDBN} host machine, you will need an unstripped copy of
18276 your program, since @value{GDBN} needs symbol and debugging information.
18277 Start up @value{GDBN} as usual, using the name of the local copy of your
18278 program as the first argument.
18280 @cindex @code{target remote}
18281 @value{GDBN} can communicate with the target over a serial line, or
18282 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18283 each case, @value{GDBN} uses the same protocol for debugging your
18284 program; only the medium carrying the debugging packets varies. The
18285 @code{target remote} command establishes a connection to the target.
18286 Its arguments indicate which medium to use:
18290 @item target remote @var{serial-device}
18291 @cindex serial line, @code{target remote}
18292 Use @var{serial-device} to communicate with the target. For example,
18293 to use a serial line connected to the device named @file{/dev/ttyb}:
18296 target remote /dev/ttyb
18299 If you're using a serial line, you may want to give @value{GDBN} the
18300 @samp{--baud} option, or use the @code{set serial baud} command
18301 (@pxref{Remote Configuration, set serial baud}) before the
18302 @code{target} command.
18304 @item target remote @code{@var{host}:@var{port}}
18305 @itemx target remote @code{tcp:@var{host}:@var{port}}
18306 @cindex @acronym{TCP} port, @code{target remote}
18307 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18308 The @var{host} may be either a host name or a numeric @acronym{IP}
18309 address; @var{port} must be a decimal number. The @var{host} could be
18310 the target machine itself, if it is directly connected to the net, or
18311 it might be a terminal server which in turn has a serial line to the
18314 For example, to connect to port 2828 on a terminal server named
18318 target remote manyfarms:2828
18321 If your remote target is actually running on the same machine as your
18322 debugger session (e.g.@: a simulator for your target running on the
18323 same host), you can omit the hostname. For example, to connect to
18324 port 1234 on your local machine:
18327 target remote :1234
18331 Note that the colon is still required here.
18333 @item target remote @code{udp:@var{host}:@var{port}}
18334 @cindex @acronym{UDP} port, @code{target remote}
18335 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18336 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18339 target remote udp:manyfarms:2828
18342 When using a @acronym{UDP} connection for remote debugging, you should
18343 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18344 can silently drop packets on busy or unreliable networks, which will
18345 cause havoc with your debugging session.
18347 @item target remote | @var{command}
18348 @cindex pipe, @code{target remote} to
18349 Run @var{command} in the background and communicate with it using a
18350 pipe. The @var{command} is a shell command, to be parsed and expanded
18351 by the system's command shell, @code{/bin/sh}; it should expect remote
18352 protocol packets on its standard input, and send replies on its
18353 standard output. You could use this to run a stand-alone simulator
18354 that speaks the remote debugging protocol, to make net connections
18355 using programs like @code{ssh}, or for other similar tricks.
18357 If @var{command} closes its standard output (perhaps by exiting),
18358 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18359 program has already exited, this will have no effect.)
18363 Once the connection has been established, you can use all the usual
18364 commands to examine and change data. The remote program is already
18365 running; you can use @kbd{step} and @kbd{continue}, and you do not
18366 need to use @kbd{run}.
18368 @cindex interrupting remote programs
18369 @cindex remote programs, interrupting
18370 Whenever @value{GDBN} is waiting for the remote program, if you type the
18371 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18372 program. This may or may not succeed, depending in part on the hardware
18373 and the serial drivers the remote system uses. If you type the
18374 interrupt character once again, @value{GDBN} displays this prompt:
18377 Interrupted while waiting for the program.
18378 Give up (and stop debugging it)? (y or n)
18381 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18382 (If you decide you want to try again later, you can use @samp{target
18383 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18384 goes back to waiting.
18387 @kindex detach (remote)
18389 When you have finished debugging the remote program, you can use the
18390 @code{detach} command to release it from @value{GDBN} control.
18391 Detaching from the target normally resumes its execution, but the results
18392 will depend on your particular remote stub. After the @code{detach}
18393 command, @value{GDBN} is free to connect to another target.
18397 The @code{disconnect} command behaves like @code{detach}, except that
18398 the target is generally not resumed. It will wait for @value{GDBN}
18399 (this instance or another one) to connect and continue debugging. After
18400 the @code{disconnect} command, @value{GDBN} is again free to connect to
18403 @cindex send command to remote monitor
18404 @cindex extend @value{GDBN} for remote targets
18405 @cindex add new commands for external monitor
18407 @item monitor @var{cmd}
18408 This command allows you to send arbitrary commands directly to the
18409 remote monitor. Since @value{GDBN} doesn't care about the commands it
18410 sends like this, this command is the way to extend @value{GDBN}---you
18411 can add new commands that only the external monitor will understand
18415 @node File Transfer
18416 @section Sending files to a remote system
18417 @cindex remote target, file transfer
18418 @cindex file transfer
18419 @cindex sending files to remote systems
18421 Some remote targets offer the ability to transfer files over the same
18422 connection used to communicate with @value{GDBN}. This is convenient
18423 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18424 running @code{gdbserver} over a network interface. For other targets,
18425 e.g.@: embedded devices with only a single serial port, this may be
18426 the only way to upload or download files.
18428 Not all remote targets support these commands.
18432 @item remote put @var{hostfile} @var{targetfile}
18433 Copy file @var{hostfile} from the host system (the machine running
18434 @value{GDBN}) to @var{targetfile} on the target system.
18437 @item remote get @var{targetfile} @var{hostfile}
18438 Copy file @var{targetfile} from the target system to @var{hostfile}
18439 on the host system.
18441 @kindex remote delete
18442 @item remote delete @var{targetfile}
18443 Delete @var{targetfile} from the target system.
18448 @section Using the @code{gdbserver} Program
18451 @cindex remote connection without stubs
18452 @code{gdbserver} is a control program for Unix-like systems, which
18453 allows you to connect your program with a remote @value{GDBN} via
18454 @code{target remote}---but without linking in the usual debugging stub.
18456 @code{gdbserver} is not a complete replacement for the debugging stubs,
18457 because it requires essentially the same operating-system facilities
18458 that @value{GDBN} itself does. In fact, a system that can run
18459 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18460 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18461 because it is a much smaller program than @value{GDBN} itself. It is
18462 also easier to port than all of @value{GDBN}, so you may be able to get
18463 started more quickly on a new system by using @code{gdbserver}.
18464 Finally, if you develop code for real-time systems, you may find that
18465 the tradeoffs involved in real-time operation make it more convenient to
18466 do as much development work as possible on another system, for example
18467 by cross-compiling. You can use @code{gdbserver} to make a similar
18468 choice for debugging.
18470 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18471 or a TCP connection, using the standard @value{GDBN} remote serial
18475 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18476 Do not run @code{gdbserver} connected to any public network; a
18477 @value{GDBN} connection to @code{gdbserver} provides access to the
18478 target system with the same privileges as the user running
18482 @subsection Running @code{gdbserver}
18483 @cindex arguments, to @code{gdbserver}
18484 @cindex @code{gdbserver}, command-line arguments
18486 Run @code{gdbserver} on the target system. You need a copy of the
18487 program you want to debug, including any libraries it requires.
18488 @code{gdbserver} does not need your program's symbol table, so you can
18489 strip the program if necessary to save space. @value{GDBN} on the host
18490 system does all the symbol handling.
18492 To use the server, you must tell it how to communicate with @value{GDBN};
18493 the name of your program; and the arguments for your program. The usual
18497 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18500 @var{comm} is either a device name (to use a serial line), or a TCP
18501 hostname and portnumber, or @code{-} or @code{stdio} to use
18502 stdin/stdout of @code{gdbserver}.
18503 For example, to debug Emacs with the argument
18504 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18508 target> gdbserver /dev/com1 emacs foo.txt
18511 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18514 To use a TCP connection instead of a serial line:
18517 target> gdbserver host:2345 emacs foo.txt
18520 The only difference from the previous example is the first argument,
18521 specifying that you are communicating with the host @value{GDBN} via
18522 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18523 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18524 (Currently, the @samp{host} part is ignored.) You can choose any number
18525 you want for the port number as long as it does not conflict with any
18526 TCP ports already in use on the target system (for example, @code{23} is
18527 reserved for @code{telnet}).@footnote{If you choose a port number that
18528 conflicts with another service, @code{gdbserver} prints an error message
18529 and exits.} You must use the same port number with the host @value{GDBN}
18530 @code{target remote} command.
18532 The @code{stdio} connection is useful when starting @code{gdbserver}
18536 (gdb) target remote | ssh -T hostname gdbserver - hello
18539 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18540 and we don't want escape-character handling. Ssh does this by default when
18541 a command is provided, the flag is provided to make it explicit.
18542 You could elide it if you want to.
18544 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18545 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18546 display through a pipe connected to gdbserver.
18547 Both @code{stdout} and @code{stderr} use the same pipe.
18549 @subsubsection Attaching to a Running Program
18550 @cindex attach to a program, @code{gdbserver}
18551 @cindex @option{--attach}, @code{gdbserver} option
18553 On some targets, @code{gdbserver} can also attach to running programs.
18554 This is accomplished via the @code{--attach} argument. The syntax is:
18557 target> gdbserver --attach @var{comm} @var{pid}
18560 @var{pid} is the process ID of a currently running process. It isn't necessary
18561 to point @code{gdbserver} at a binary for the running process.
18564 You can debug processes by name instead of process ID if your target has the
18565 @code{pidof} utility:
18568 target> gdbserver --attach @var{comm} `pidof @var{program}`
18571 In case more than one copy of @var{program} is running, or @var{program}
18572 has multiple threads, most versions of @code{pidof} support the
18573 @code{-s} option to only return the first process ID.
18575 @subsubsection Multi-Process Mode for @code{gdbserver}
18576 @cindex @code{gdbserver}, multiple processes
18577 @cindex multiple processes with @code{gdbserver}
18579 When you connect to @code{gdbserver} using @code{target remote},
18580 @code{gdbserver} debugs the specified program only once. When the
18581 program exits, or you detach from it, @value{GDBN} closes the connection
18582 and @code{gdbserver} exits.
18584 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18585 enters multi-process mode. When the debugged program exits, or you
18586 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18587 though no program is running. The @code{run} and @code{attach}
18588 commands instruct @code{gdbserver} to run or attach to a new program.
18589 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18590 remote exec-file}) to select the program to run. Command line
18591 arguments are supported, except for wildcard expansion and I/O
18592 redirection (@pxref{Arguments}).
18594 @cindex @option{--multi}, @code{gdbserver} option
18595 To start @code{gdbserver} without supplying an initial command to run
18596 or process ID to attach, use the @option{--multi} command line option.
18597 Then you can connect using @kbd{target extended-remote} and start
18598 the program you want to debug.
18600 In multi-process mode @code{gdbserver} does not automatically exit unless you
18601 use the option @option{--once}. You can terminate it by using
18602 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18603 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18604 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18605 @option{--multi} option to @code{gdbserver} has no influence on that.
18607 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18609 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18611 @code{gdbserver} normally terminates after all of its debugged processes have
18612 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18613 extended-remote}, @code{gdbserver} stays running even with no processes left.
18614 @value{GDBN} normally terminates the spawned debugged process on its exit,
18615 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18616 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18617 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18618 stays running even in the @kbd{target remote} mode.
18620 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18621 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18622 completeness, at most one @value{GDBN} can be connected at a time.
18624 @cindex @option{--once}, @code{gdbserver} option
18625 By default, @code{gdbserver} keeps the listening TCP port open, so that
18626 subsequent connections are possible. However, if you start @code{gdbserver}
18627 with the @option{--once} option, it will stop listening for any further
18628 connection attempts after connecting to the first @value{GDBN} session. This
18629 means no further connections to @code{gdbserver} will be possible after the
18630 first one. It also means @code{gdbserver} will terminate after the first
18631 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18632 connections and even in the @kbd{target extended-remote} mode. The
18633 @option{--once} option allows reusing the same port number for connecting to
18634 multiple instances of @code{gdbserver} running on the same host, since each
18635 instance closes its port after the first connection.
18637 @anchor{Other Command-Line Arguments for gdbserver}
18638 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18640 @cindex @option{--debug}, @code{gdbserver} option
18641 The @option{--debug} option tells @code{gdbserver} to display extra
18642 status information about the debugging process.
18643 @cindex @option{--remote-debug}, @code{gdbserver} option
18644 The @option{--remote-debug} option tells @code{gdbserver} to display
18645 remote protocol debug output. These options are intended for
18646 @code{gdbserver} development and for bug reports to the developers.
18648 @cindex @option{--debug-format}, @code{gdbserver} option
18649 The @option{--debug-format=option1[,option2,...]} option tells
18650 @code{gdbserver} to include additional information in each output.
18651 Possible options are:
18655 Turn off all extra information in debugging output.
18657 Turn on all extra information in debugging output.
18659 Include a timestamp in each line of debugging output.
18662 Options are processed in order. Thus, for example, if @option{none}
18663 appears last then no additional information is added to debugging output.
18665 @cindex @option{--wrapper}, @code{gdbserver} option
18666 The @option{--wrapper} option specifies a wrapper to launch programs
18667 for debugging. The option should be followed by the name of the
18668 wrapper, then any command-line arguments to pass to the wrapper, then
18669 @kbd{--} indicating the end of the wrapper arguments.
18671 @code{gdbserver} runs the specified wrapper program with a combined
18672 command line including the wrapper arguments, then the name of the
18673 program to debug, then any arguments to the program. The wrapper
18674 runs until it executes your program, and then @value{GDBN} gains control.
18676 You can use any program that eventually calls @code{execve} with
18677 its arguments as a wrapper. Several standard Unix utilities do
18678 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18679 with @code{exec "$@@"} will also work.
18681 For example, you can use @code{env} to pass an environment variable to
18682 the debugged program, without setting the variable in @code{gdbserver}'s
18686 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18689 @subsection Connecting to @code{gdbserver}
18691 Run @value{GDBN} on the host system.
18693 First make sure you have the necessary symbol files. Load symbols for
18694 your application using the @code{file} command before you connect. Use
18695 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18696 was compiled with the correct sysroot using @code{--with-sysroot}).
18698 The symbol file and target libraries must exactly match the executable
18699 and libraries on the target, with one exception: the files on the host
18700 system should not be stripped, even if the files on the target system
18701 are. Mismatched or missing files will lead to confusing results
18702 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18703 files may also prevent @code{gdbserver} from debugging multi-threaded
18706 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18707 For TCP connections, you must start up @code{gdbserver} prior to using
18708 the @code{target remote} command. Otherwise you may get an error whose
18709 text depends on the host system, but which usually looks something like
18710 @samp{Connection refused}. Don't use the @code{load}
18711 command in @value{GDBN} when using @code{gdbserver}, since the program is
18712 already on the target.
18714 @subsection Monitor Commands for @code{gdbserver}
18715 @cindex monitor commands, for @code{gdbserver}
18716 @anchor{Monitor Commands for gdbserver}
18718 During a @value{GDBN} session using @code{gdbserver}, you can use the
18719 @code{monitor} command to send special requests to @code{gdbserver}.
18720 Here are the available commands.
18724 List the available monitor commands.
18726 @item monitor set debug 0
18727 @itemx monitor set debug 1
18728 Disable or enable general debugging messages.
18730 @item monitor set remote-debug 0
18731 @itemx monitor set remote-debug 1
18732 Disable or enable specific debugging messages associated with the remote
18733 protocol (@pxref{Remote Protocol}).
18735 @item monitor set debug-format option1@r{[},option2,...@r{]}
18736 Specify additional text to add to debugging messages.
18737 Possible options are:
18741 Turn off all extra information in debugging output.
18743 Turn on all extra information in debugging output.
18745 Include a timestamp in each line of debugging output.
18748 Options are processed in order. Thus, for example, if @option{none}
18749 appears last then no additional information is added to debugging output.
18751 @item monitor set libthread-db-search-path [PATH]
18752 @cindex gdbserver, search path for @code{libthread_db}
18753 When this command is issued, @var{path} is a colon-separated list of
18754 directories to search for @code{libthread_db} (@pxref{Threads,,set
18755 libthread-db-search-path}). If you omit @var{path},
18756 @samp{libthread-db-search-path} will be reset to its default value.
18758 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18759 not supported in @code{gdbserver}.
18762 Tell gdbserver to exit immediately. This command should be followed by
18763 @code{disconnect} to close the debugging session. @code{gdbserver} will
18764 detach from any attached processes and kill any processes it created.
18765 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18766 of a multi-process mode debug session.
18770 @subsection Tracepoints support in @code{gdbserver}
18771 @cindex tracepoints support in @code{gdbserver}
18773 On some targets, @code{gdbserver} supports tracepoints, fast
18774 tracepoints and static tracepoints.
18776 For fast or static tracepoints to work, a special library called the
18777 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18778 This library is built and distributed as an integral part of
18779 @code{gdbserver}. In addition, support for static tracepoints
18780 requires building the in-process agent library with static tracepoints
18781 support. At present, the UST (LTTng Userspace Tracer,
18782 @url{http://lttng.org/ust}) tracing engine is supported. This support
18783 is automatically available if UST development headers are found in the
18784 standard include path when @code{gdbserver} is built, or if
18785 @code{gdbserver} was explicitly configured using @option{--with-ust}
18786 to point at such headers. You can explicitly disable the support
18787 using @option{--with-ust=no}.
18789 There are several ways to load the in-process agent in your program:
18792 @item Specifying it as dependency at link time
18794 You can link your program dynamically with the in-process agent
18795 library. On most systems, this is accomplished by adding
18796 @code{-linproctrace} to the link command.
18798 @item Using the system's preloading mechanisms
18800 You can force loading the in-process agent at startup time by using
18801 your system's support for preloading shared libraries. Many Unixes
18802 support the concept of preloading user defined libraries. In most
18803 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18804 in the environment. See also the description of @code{gdbserver}'s
18805 @option{--wrapper} command line option.
18807 @item Using @value{GDBN} to force loading the agent at run time
18809 On some systems, you can force the inferior to load a shared library,
18810 by calling a dynamic loader function in the inferior that takes care
18811 of dynamically looking up and loading a shared library. On most Unix
18812 systems, the function is @code{dlopen}. You'll use the @code{call}
18813 command for that. For example:
18816 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18819 Note that on most Unix systems, for the @code{dlopen} function to be
18820 available, the program needs to be linked with @code{-ldl}.
18823 On systems that have a userspace dynamic loader, like most Unix
18824 systems, when you connect to @code{gdbserver} using @code{target
18825 remote}, you'll find that the program is stopped at the dynamic
18826 loader's entry point, and no shared library has been loaded in the
18827 program's address space yet, including the in-process agent. In that
18828 case, before being able to use any of the fast or static tracepoints
18829 features, you need to let the loader run and load the shared
18830 libraries. The simplest way to do that is to run the program to the
18831 main procedure. E.g., if debugging a C or C@t{++} program, start
18832 @code{gdbserver} like so:
18835 $ gdbserver :9999 myprogram
18838 Start GDB and connect to @code{gdbserver} like so, and run to main:
18842 (@value{GDBP}) target remote myhost:9999
18843 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18844 (@value{GDBP}) b main
18845 (@value{GDBP}) continue
18848 The in-process tracing agent library should now be loaded into the
18849 process; you can confirm it with the @code{info sharedlibrary}
18850 command, which will list @file{libinproctrace.so} as loaded in the
18851 process. You are now ready to install fast tracepoints, list static
18852 tracepoint markers, probe static tracepoints markers, and start
18855 @node Remote Configuration
18856 @section Remote Configuration
18859 @kindex show remote
18860 This section documents the configuration options available when
18861 debugging remote programs. For the options related to the File I/O
18862 extensions of the remote protocol, see @ref{system,
18863 system-call-allowed}.
18866 @item set remoteaddresssize @var{bits}
18867 @cindex address size for remote targets
18868 @cindex bits in remote address
18869 Set the maximum size of address in a memory packet to the specified
18870 number of bits. @value{GDBN} will mask off the address bits above
18871 that number, when it passes addresses to the remote target. The
18872 default value is the number of bits in the target's address.
18874 @item show remoteaddresssize
18875 Show the current value of remote address size in bits.
18877 @item set serial baud @var{n}
18878 @cindex baud rate for remote targets
18879 Set the baud rate for the remote serial I/O to @var{n} baud. The
18880 value is used to set the speed of the serial port used for debugging
18883 @item show serial baud
18884 Show the current speed of the remote connection.
18886 @item set remotebreak
18887 @cindex interrupt remote programs
18888 @cindex BREAK signal instead of Ctrl-C
18889 @anchor{set remotebreak}
18890 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18891 when you type @kbd{Ctrl-c} to interrupt the program running
18892 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18893 character instead. The default is off, since most remote systems
18894 expect to see @samp{Ctrl-C} as the interrupt signal.
18896 @item show remotebreak
18897 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18898 interrupt the remote program.
18900 @item set remoteflow on
18901 @itemx set remoteflow off
18902 @kindex set remoteflow
18903 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18904 on the serial port used to communicate to the remote target.
18906 @item show remoteflow
18907 @kindex show remoteflow
18908 Show the current setting of hardware flow control.
18910 @item set remotelogbase @var{base}
18911 Set the base (a.k.a.@: radix) of logging serial protocol
18912 communications to @var{base}. Supported values of @var{base} are:
18913 @code{ascii}, @code{octal}, and @code{hex}. The default is
18916 @item show remotelogbase
18917 Show the current setting of the radix for logging remote serial
18920 @item set remotelogfile @var{file}
18921 @cindex record serial communications on file
18922 Record remote serial communications on the named @var{file}. The
18923 default is not to record at all.
18925 @item show remotelogfile.
18926 Show the current setting of the file name on which to record the
18927 serial communications.
18929 @item set remotetimeout @var{num}
18930 @cindex timeout for serial communications
18931 @cindex remote timeout
18932 Set the timeout limit to wait for the remote target to respond to
18933 @var{num} seconds. The default is 2 seconds.
18935 @item show remotetimeout
18936 Show the current number of seconds to wait for the remote target
18939 @cindex limit hardware breakpoints and watchpoints
18940 @cindex remote target, limit break- and watchpoints
18941 @anchor{set remote hardware-watchpoint-limit}
18942 @anchor{set remote hardware-breakpoint-limit}
18943 @item set remote hardware-watchpoint-limit @var{limit}
18944 @itemx set remote hardware-breakpoint-limit @var{limit}
18945 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18946 watchpoints. A limit of -1, the default, is treated as unlimited.
18948 @cindex limit hardware watchpoints length
18949 @cindex remote target, limit watchpoints length
18950 @anchor{set remote hardware-watchpoint-length-limit}
18951 @item set remote hardware-watchpoint-length-limit @var{limit}
18952 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18953 a remote hardware watchpoint. A limit of -1, the default, is treated
18956 @item show remote hardware-watchpoint-length-limit
18957 Show the current limit (in bytes) of the maximum length of
18958 a remote hardware watchpoint.
18960 @item set remote exec-file @var{filename}
18961 @itemx show remote exec-file
18962 @anchor{set remote exec-file}
18963 @cindex executable file, for remote target
18964 Select the file used for @code{run} with @code{target
18965 extended-remote}. This should be set to a filename valid on the
18966 target system. If it is not set, the target will use a default
18967 filename (e.g.@: the last program run).
18969 @item set remote interrupt-sequence
18970 @cindex interrupt remote programs
18971 @cindex select Ctrl-C, BREAK or BREAK-g
18972 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18973 @samp{BREAK-g} as the
18974 sequence to the remote target in order to interrupt the execution.
18975 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18976 is high level of serial line for some certain time.
18977 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18978 It is @code{BREAK} signal followed by character @code{g}.
18980 @item show interrupt-sequence
18981 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18982 is sent by @value{GDBN} to interrupt the remote program.
18983 @code{BREAK-g} is BREAK signal followed by @code{g} and
18984 also known as Magic SysRq g.
18986 @item set remote interrupt-on-connect
18987 @cindex send interrupt-sequence on start
18988 Specify whether interrupt-sequence is sent to remote target when
18989 @value{GDBN} connects to it. This is mostly needed when you debug
18990 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18991 which is known as Magic SysRq g in order to connect @value{GDBN}.
18993 @item show interrupt-on-connect
18994 Show whether interrupt-sequence is sent
18995 to remote target when @value{GDBN} connects to it.
18999 @item set tcp auto-retry on
19000 @cindex auto-retry, for remote TCP target
19001 Enable auto-retry for remote TCP connections. This is useful if the remote
19002 debugging agent is launched in parallel with @value{GDBN}; there is a race
19003 condition because the agent may not become ready to accept the connection
19004 before @value{GDBN} attempts to connect. When auto-retry is
19005 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19006 to establish the connection using the timeout specified by
19007 @code{set tcp connect-timeout}.
19009 @item set tcp auto-retry off
19010 Do not auto-retry failed TCP connections.
19012 @item show tcp auto-retry
19013 Show the current auto-retry setting.
19015 @item set tcp connect-timeout @var{seconds}
19016 @itemx set tcp connect-timeout unlimited
19017 @cindex connection timeout, for remote TCP target
19018 @cindex timeout, for remote target connection
19019 Set the timeout for establishing a TCP connection to the remote target to
19020 @var{seconds}. The timeout affects both polling to retry failed connections
19021 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19022 that are merely slow to complete, and represents an approximate cumulative
19023 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19024 @value{GDBN} will keep attempting to establish a connection forever,
19025 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19027 @item show tcp connect-timeout
19028 Show the current connection timeout setting.
19031 @cindex remote packets, enabling and disabling
19032 The @value{GDBN} remote protocol autodetects the packets supported by
19033 your debugging stub. If you need to override the autodetection, you
19034 can use these commands to enable or disable individual packets. Each
19035 packet can be set to @samp{on} (the remote target supports this
19036 packet), @samp{off} (the remote target does not support this packet),
19037 or @samp{auto} (detect remote target support for this packet). They
19038 all default to @samp{auto}. For more information about each packet,
19039 see @ref{Remote Protocol}.
19041 During normal use, you should not have to use any of these commands.
19042 If you do, that may be a bug in your remote debugging stub, or a bug
19043 in @value{GDBN}. You may want to report the problem to the
19044 @value{GDBN} developers.
19046 For each packet @var{name}, the command to enable or disable the
19047 packet is @code{set remote @var{name}-packet}. The available settings
19050 @multitable @columnfractions 0.28 0.32 0.25
19053 @tab Related Features
19055 @item @code{fetch-register}
19057 @tab @code{info registers}
19059 @item @code{set-register}
19063 @item @code{binary-download}
19065 @tab @code{load}, @code{set}
19067 @item @code{read-aux-vector}
19068 @tab @code{qXfer:auxv:read}
19069 @tab @code{info auxv}
19071 @item @code{symbol-lookup}
19072 @tab @code{qSymbol}
19073 @tab Detecting multiple threads
19075 @item @code{attach}
19076 @tab @code{vAttach}
19079 @item @code{verbose-resume}
19081 @tab Stepping or resuming multiple threads
19087 @item @code{software-breakpoint}
19091 @item @code{hardware-breakpoint}
19095 @item @code{write-watchpoint}
19099 @item @code{read-watchpoint}
19103 @item @code{access-watchpoint}
19107 @item @code{target-features}
19108 @tab @code{qXfer:features:read}
19109 @tab @code{set architecture}
19111 @item @code{library-info}
19112 @tab @code{qXfer:libraries:read}
19113 @tab @code{info sharedlibrary}
19115 @item @code{memory-map}
19116 @tab @code{qXfer:memory-map:read}
19117 @tab @code{info mem}
19119 @item @code{read-sdata-object}
19120 @tab @code{qXfer:sdata:read}
19121 @tab @code{print $_sdata}
19123 @item @code{read-spu-object}
19124 @tab @code{qXfer:spu:read}
19125 @tab @code{info spu}
19127 @item @code{write-spu-object}
19128 @tab @code{qXfer:spu:write}
19129 @tab @code{info spu}
19131 @item @code{read-siginfo-object}
19132 @tab @code{qXfer:siginfo:read}
19133 @tab @code{print $_siginfo}
19135 @item @code{write-siginfo-object}
19136 @tab @code{qXfer:siginfo:write}
19137 @tab @code{set $_siginfo}
19139 @item @code{threads}
19140 @tab @code{qXfer:threads:read}
19141 @tab @code{info threads}
19143 @item @code{get-thread-local-@*storage-address}
19144 @tab @code{qGetTLSAddr}
19145 @tab Displaying @code{__thread} variables
19147 @item @code{get-thread-information-block-address}
19148 @tab @code{qGetTIBAddr}
19149 @tab Display MS-Windows Thread Information Block.
19151 @item @code{search-memory}
19152 @tab @code{qSearch:memory}
19155 @item @code{supported-packets}
19156 @tab @code{qSupported}
19157 @tab Remote communications parameters
19159 @item @code{pass-signals}
19160 @tab @code{QPassSignals}
19161 @tab @code{handle @var{signal}}
19163 @item @code{program-signals}
19164 @tab @code{QProgramSignals}
19165 @tab @code{handle @var{signal}}
19167 @item @code{hostio-close-packet}
19168 @tab @code{vFile:close}
19169 @tab @code{remote get}, @code{remote put}
19171 @item @code{hostio-open-packet}
19172 @tab @code{vFile:open}
19173 @tab @code{remote get}, @code{remote put}
19175 @item @code{hostio-pread-packet}
19176 @tab @code{vFile:pread}
19177 @tab @code{remote get}, @code{remote put}
19179 @item @code{hostio-pwrite-packet}
19180 @tab @code{vFile:pwrite}
19181 @tab @code{remote get}, @code{remote put}
19183 @item @code{hostio-unlink-packet}
19184 @tab @code{vFile:unlink}
19185 @tab @code{remote delete}
19187 @item @code{hostio-readlink-packet}
19188 @tab @code{vFile:readlink}
19191 @item @code{noack-packet}
19192 @tab @code{QStartNoAckMode}
19193 @tab Packet acknowledgment
19195 @item @code{osdata}
19196 @tab @code{qXfer:osdata:read}
19197 @tab @code{info os}
19199 @item @code{query-attached}
19200 @tab @code{qAttached}
19201 @tab Querying remote process attach state.
19203 @item @code{trace-buffer-size}
19204 @tab @code{QTBuffer:size}
19205 @tab @code{set trace-buffer-size}
19207 @item @code{trace-status}
19208 @tab @code{qTStatus}
19209 @tab @code{tstatus}
19211 @item @code{traceframe-info}
19212 @tab @code{qXfer:traceframe-info:read}
19213 @tab Traceframe info
19215 @item @code{install-in-trace}
19216 @tab @code{InstallInTrace}
19217 @tab Install tracepoint in tracing
19219 @item @code{disable-randomization}
19220 @tab @code{QDisableRandomization}
19221 @tab @code{set disable-randomization}
19223 @item @code{conditional-breakpoints-packet}
19224 @tab @code{Z0 and Z1}
19225 @tab @code{Support for target-side breakpoint condition evaluation}
19229 @section Implementing a Remote Stub
19231 @cindex debugging stub, example
19232 @cindex remote stub, example
19233 @cindex stub example, remote debugging
19234 The stub files provided with @value{GDBN} implement the target side of the
19235 communication protocol, and the @value{GDBN} side is implemented in the
19236 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19237 these subroutines to communicate, and ignore the details. (If you're
19238 implementing your own stub file, you can still ignore the details: start
19239 with one of the existing stub files. @file{sparc-stub.c} is the best
19240 organized, and therefore the easiest to read.)
19242 @cindex remote serial debugging, overview
19243 To debug a program running on another machine (the debugging
19244 @dfn{target} machine), you must first arrange for all the usual
19245 prerequisites for the program to run by itself. For example, for a C
19250 A startup routine to set up the C runtime environment; these usually
19251 have a name like @file{crt0}. The startup routine may be supplied by
19252 your hardware supplier, or you may have to write your own.
19255 A C subroutine library to support your program's
19256 subroutine calls, notably managing input and output.
19259 A way of getting your program to the other machine---for example, a
19260 download program. These are often supplied by the hardware
19261 manufacturer, but you may have to write your own from hardware
19265 The next step is to arrange for your program to use a serial port to
19266 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19267 machine). In general terms, the scheme looks like this:
19271 @value{GDBN} already understands how to use this protocol; when everything
19272 else is set up, you can simply use the @samp{target remote} command
19273 (@pxref{Targets,,Specifying a Debugging Target}).
19275 @item On the target,
19276 you must link with your program a few special-purpose subroutines that
19277 implement the @value{GDBN} remote serial protocol. The file containing these
19278 subroutines is called a @dfn{debugging stub}.
19280 On certain remote targets, you can use an auxiliary program
19281 @code{gdbserver} instead of linking a stub into your program.
19282 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19285 The debugging stub is specific to the architecture of the remote
19286 machine; for example, use @file{sparc-stub.c} to debug programs on
19289 @cindex remote serial stub list
19290 These working remote stubs are distributed with @value{GDBN}:
19295 @cindex @file{i386-stub.c}
19298 For Intel 386 and compatible architectures.
19301 @cindex @file{m68k-stub.c}
19302 @cindex Motorola 680x0
19304 For Motorola 680x0 architectures.
19307 @cindex @file{sh-stub.c}
19310 For Renesas SH architectures.
19313 @cindex @file{sparc-stub.c}
19315 For @sc{sparc} architectures.
19317 @item sparcl-stub.c
19318 @cindex @file{sparcl-stub.c}
19321 For Fujitsu @sc{sparclite} architectures.
19325 The @file{README} file in the @value{GDBN} distribution may list other
19326 recently added stubs.
19329 * Stub Contents:: What the stub can do for you
19330 * Bootstrapping:: What you must do for the stub
19331 * Debug Session:: Putting it all together
19334 @node Stub Contents
19335 @subsection What the Stub Can Do for You
19337 @cindex remote serial stub
19338 The debugging stub for your architecture supplies these three
19342 @item set_debug_traps
19343 @findex set_debug_traps
19344 @cindex remote serial stub, initialization
19345 This routine arranges for @code{handle_exception} to run when your
19346 program stops. You must call this subroutine explicitly in your
19347 program's startup code.
19349 @item handle_exception
19350 @findex handle_exception
19351 @cindex remote serial stub, main routine
19352 This is the central workhorse, but your program never calls it
19353 explicitly---the setup code arranges for @code{handle_exception} to
19354 run when a trap is triggered.
19356 @code{handle_exception} takes control when your program stops during
19357 execution (for example, on a breakpoint), and mediates communications
19358 with @value{GDBN} on the host machine. This is where the communications
19359 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19360 representative on the target machine. It begins by sending summary
19361 information on the state of your program, then continues to execute,
19362 retrieving and transmitting any information @value{GDBN} needs, until you
19363 execute a @value{GDBN} command that makes your program resume; at that point,
19364 @code{handle_exception} returns control to your own code on the target
19368 @cindex @code{breakpoint} subroutine, remote
19369 Use this auxiliary subroutine to make your program contain a
19370 breakpoint. Depending on the particular situation, this may be the only
19371 way for @value{GDBN} to get control. For instance, if your target
19372 machine has some sort of interrupt button, you won't need to call this;
19373 pressing the interrupt button transfers control to
19374 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19375 simply receiving characters on the serial port may also trigger a trap;
19376 again, in that situation, you don't need to call @code{breakpoint} from
19377 your own program---simply running @samp{target remote} from the host
19378 @value{GDBN} session gets control.
19380 Call @code{breakpoint} if none of these is true, or if you simply want
19381 to make certain your program stops at a predetermined point for the
19382 start of your debugging session.
19385 @node Bootstrapping
19386 @subsection What You Must Do for the Stub
19388 @cindex remote stub, support routines
19389 The debugging stubs that come with @value{GDBN} are set up for a particular
19390 chip architecture, but they have no information about the rest of your
19391 debugging target machine.
19393 First of all you need to tell the stub how to communicate with the
19397 @item int getDebugChar()
19398 @findex getDebugChar
19399 Write this subroutine to read a single character from the serial port.
19400 It may be identical to @code{getchar} for your target system; a
19401 different name is used to allow you to distinguish the two if you wish.
19403 @item void putDebugChar(int)
19404 @findex putDebugChar
19405 Write this subroutine to write a single character to the serial port.
19406 It may be identical to @code{putchar} for your target system; a
19407 different name is used to allow you to distinguish the two if you wish.
19410 @cindex control C, and remote debugging
19411 @cindex interrupting remote targets
19412 If you want @value{GDBN} to be able to stop your program while it is
19413 running, you need to use an interrupt-driven serial driver, and arrange
19414 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19415 character). That is the character which @value{GDBN} uses to tell the
19416 remote system to stop.
19418 Getting the debugging target to return the proper status to @value{GDBN}
19419 probably requires changes to the standard stub; one quick and dirty way
19420 is to just execute a breakpoint instruction (the ``dirty'' part is that
19421 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19423 Other routines you need to supply are:
19426 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19427 @findex exceptionHandler
19428 Write this function to install @var{exception_address} in the exception
19429 handling tables. You need to do this because the stub does not have any
19430 way of knowing what the exception handling tables on your target system
19431 are like (for example, the processor's table might be in @sc{rom},
19432 containing entries which point to a table in @sc{ram}).
19433 The @var{exception_number} specifies the exception which should be changed;
19434 its meaning is architecture-dependent (for example, different numbers
19435 might represent divide by zero, misaligned access, etc). When this
19436 exception occurs, control should be transferred directly to
19437 @var{exception_address}, and the processor state (stack, registers,
19438 and so on) should be just as it is when a processor exception occurs. So if
19439 you want to use a jump instruction to reach @var{exception_address}, it
19440 should be a simple jump, not a jump to subroutine.
19442 For the 386, @var{exception_address} should be installed as an interrupt
19443 gate so that interrupts are masked while the handler runs. The gate
19444 should be at privilege level 0 (the most privileged level). The
19445 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19446 help from @code{exceptionHandler}.
19448 @item void flush_i_cache()
19449 @findex flush_i_cache
19450 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19451 instruction cache, if any, on your target machine. If there is no
19452 instruction cache, this subroutine may be a no-op.
19454 On target machines that have instruction caches, @value{GDBN} requires this
19455 function to make certain that the state of your program is stable.
19459 You must also make sure this library routine is available:
19462 @item void *memset(void *, int, int)
19464 This is the standard library function @code{memset} that sets an area of
19465 memory to a known value. If you have one of the free versions of
19466 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19467 either obtain it from your hardware manufacturer, or write your own.
19470 If you do not use the GNU C compiler, you may need other standard
19471 library subroutines as well; this varies from one stub to another,
19472 but in general the stubs are likely to use any of the common library
19473 subroutines which @code{@value{NGCC}} generates as inline code.
19476 @node Debug Session
19477 @subsection Putting it All Together
19479 @cindex remote serial debugging summary
19480 In summary, when your program is ready to debug, you must follow these
19485 Make sure you have defined the supporting low-level routines
19486 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19488 @code{getDebugChar}, @code{putDebugChar},
19489 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19493 Insert these lines in your program's startup code, before the main
19494 procedure is called:
19501 On some machines, when a breakpoint trap is raised, the hardware
19502 automatically makes the PC point to the instruction after the
19503 breakpoint. If your machine doesn't do that, you may need to adjust
19504 @code{handle_exception} to arrange for it to return to the instruction
19505 after the breakpoint on this first invocation, so that your program
19506 doesn't keep hitting the initial breakpoint instead of making
19510 For the 680x0 stub only, you need to provide a variable called
19511 @code{exceptionHook}. Normally you just use:
19514 void (*exceptionHook)() = 0;
19518 but if before calling @code{set_debug_traps}, you set it to point to a
19519 function in your program, that function is called when
19520 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19521 error). The function indicated by @code{exceptionHook} is called with
19522 one parameter: an @code{int} which is the exception number.
19525 Compile and link together: your program, the @value{GDBN} debugging stub for
19526 your target architecture, and the supporting subroutines.
19529 Make sure you have a serial connection between your target machine and
19530 the @value{GDBN} host, and identify the serial port on the host.
19533 @c The "remote" target now provides a `load' command, so we should
19534 @c document that. FIXME.
19535 Download your program to your target machine (or get it there by
19536 whatever means the manufacturer provides), and start it.
19539 Start @value{GDBN} on the host, and connect to the target
19540 (@pxref{Connecting,,Connecting to a Remote Target}).
19544 @node Configurations
19545 @chapter Configuration-Specific Information
19547 While nearly all @value{GDBN} commands are available for all native and
19548 cross versions of the debugger, there are some exceptions. This chapter
19549 describes things that are only available in certain configurations.
19551 There are three major categories of configurations: native
19552 configurations, where the host and target are the same, embedded
19553 operating system configurations, which are usually the same for several
19554 different processor architectures, and bare embedded processors, which
19555 are quite different from each other.
19560 * Embedded Processors::
19567 This section describes details specific to particular native
19572 * BSD libkvm Interface:: Debugging BSD kernel memory images
19573 * SVR4 Process Information:: SVR4 process information
19574 * DJGPP Native:: Features specific to the DJGPP port
19575 * Cygwin Native:: Features specific to the Cygwin port
19576 * Hurd Native:: Features specific to @sc{gnu} Hurd
19577 * Darwin:: Features specific to Darwin
19583 On HP-UX systems, if you refer to a function or variable name that
19584 begins with a dollar sign, @value{GDBN} searches for a user or system
19585 name first, before it searches for a convenience variable.
19588 @node BSD libkvm Interface
19589 @subsection BSD libkvm Interface
19592 @cindex kernel memory image
19593 @cindex kernel crash dump
19595 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19596 interface that provides a uniform interface for accessing kernel virtual
19597 memory images, including live systems and crash dumps. @value{GDBN}
19598 uses this interface to allow you to debug live kernels and kernel crash
19599 dumps on many native BSD configurations. This is implemented as a
19600 special @code{kvm} debugging target. For debugging a live system, load
19601 the currently running kernel into @value{GDBN} and connect to the
19605 (@value{GDBP}) @b{target kvm}
19608 For debugging crash dumps, provide the file name of the crash dump as an
19612 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19615 Once connected to the @code{kvm} target, the following commands are
19621 Set current context from the @dfn{Process Control Block} (PCB) address.
19624 Set current context from proc address. This command isn't available on
19625 modern FreeBSD systems.
19628 @node SVR4 Process Information
19629 @subsection SVR4 Process Information
19631 @cindex examine process image
19632 @cindex process info via @file{/proc}
19634 Many versions of SVR4 and compatible systems provide a facility called
19635 @samp{/proc} that can be used to examine the image of a running
19636 process using file-system subroutines.
19638 If @value{GDBN} is configured for an operating system with this
19639 facility, the command @code{info proc} is available to report
19640 information about the process running your program, or about any
19641 process running on your system. This includes, as of this writing,
19642 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19643 not HP-UX, for example.
19645 This command may also work on core files that were created on a system
19646 that has the @samp{/proc} facility.
19652 @itemx info proc @var{process-id}
19653 Summarize available information about any running process. If a
19654 process ID is specified by @var{process-id}, display information about
19655 that process; otherwise display information about the program being
19656 debugged. The summary includes the debugged process ID, the command
19657 line used to invoke it, its current working directory, and its
19658 executable file's absolute file name.
19660 On some systems, @var{process-id} can be of the form
19661 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19662 within a process. If the optional @var{pid} part is missing, it means
19663 a thread from the process being debugged (the leading @samp{/} still
19664 needs to be present, or else @value{GDBN} will interpret the number as
19665 a process ID rather than a thread ID).
19667 @item info proc cmdline
19668 @cindex info proc cmdline
19669 Show the original command line of the process. This command is
19670 specific to @sc{gnu}/Linux.
19672 @item info proc cwd
19673 @cindex info proc cwd
19674 Show the current working directory of the process. This command is
19675 specific to @sc{gnu}/Linux.
19677 @item info proc exe
19678 @cindex info proc exe
19679 Show the name of executable of the process. This command is specific
19682 @item info proc mappings
19683 @cindex memory address space mappings
19684 Report the memory address space ranges accessible in the program, with
19685 information on whether the process has read, write, or execute access
19686 rights to each range. On @sc{gnu}/Linux systems, each memory range
19687 includes the object file which is mapped to that range, instead of the
19688 memory access rights to that range.
19690 @item info proc stat
19691 @itemx info proc status
19692 @cindex process detailed status information
19693 These subcommands are specific to @sc{gnu}/Linux systems. They show
19694 the process-related information, including the user ID and group ID;
19695 how many threads are there in the process; its virtual memory usage;
19696 the signals that are pending, blocked, and ignored; its TTY; its
19697 consumption of system and user time; its stack size; its @samp{nice}
19698 value; etc. For more information, see the @samp{proc} man page
19699 (type @kbd{man 5 proc} from your shell prompt).
19701 @item info proc all
19702 Show all the information about the process described under all of the
19703 above @code{info proc} subcommands.
19706 @comment These sub-options of 'info proc' were not included when
19707 @comment procfs.c was re-written. Keep their descriptions around
19708 @comment against the day when someone finds the time to put them back in.
19709 @kindex info proc times
19710 @item info proc times
19711 Starting time, user CPU time, and system CPU time for your program and
19714 @kindex info proc id
19716 Report on the process IDs related to your program: its own process ID,
19717 the ID of its parent, the process group ID, and the session ID.
19720 @item set procfs-trace
19721 @kindex set procfs-trace
19722 @cindex @code{procfs} API calls
19723 This command enables and disables tracing of @code{procfs} API calls.
19725 @item show procfs-trace
19726 @kindex show procfs-trace
19727 Show the current state of @code{procfs} API call tracing.
19729 @item set procfs-file @var{file}
19730 @kindex set procfs-file
19731 Tell @value{GDBN} to write @code{procfs} API trace to the named
19732 @var{file}. @value{GDBN} appends the trace info to the previous
19733 contents of the file. The default is to display the trace on the
19736 @item show procfs-file
19737 @kindex show procfs-file
19738 Show the file to which @code{procfs} API trace is written.
19740 @item proc-trace-entry
19741 @itemx proc-trace-exit
19742 @itemx proc-untrace-entry
19743 @itemx proc-untrace-exit
19744 @kindex proc-trace-entry
19745 @kindex proc-trace-exit
19746 @kindex proc-untrace-entry
19747 @kindex proc-untrace-exit
19748 These commands enable and disable tracing of entries into and exits
19749 from the @code{syscall} interface.
19752 @kindex info pidlist
19753 @cindex process list, QNX Neutrino
19754 For QNX Neutrino only, this command displays the list of all the
19755 processes and all the threads within each process.
19758 @kindex info meminfo
19759 @cindex mapinfo list, QNX Neutrino
19760 For QNX Neutrino only, this command displays the list of all mapinfos.
19764 @subsection Features for Debugging @sc{djgpp} Programs
19765 @cindex @sc{djgpp} debugging
19766 @cindex native @sc{djgpp} debugging
19767 @cindex MS-DOS-specific commands
19770 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19771 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19772 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19773 top of real-mode DOS systems and their emulations.
19775 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19776 defines a few commands specific to the @sc{djgpp} port. This
19777 subsection describes those commands.
19782 This is a prefix of @sc{djgpp}-specific commands which print
19783 information about the target system and important OS structures.
19786 @cindex MS-DOS system info
19787 @cindex free memory information (MS-DOS)
19788 @item info dos sysinfo
19789 This command displays assorted information about the underlying
19790 platform: the CPU type and features, the OS version and flavor, the
19791 DPMI version, and the available conventional and DPMI memory.
19796 @cindex segment descriptor tables
19797 @cindex descriptor tables display
19799 @itemx info dos ldt
19800 @itemx info dos idt
19801 These 3 commands display entries from, respectively, Global, Local,
19802 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19803 tables are data structures which store a descriptor for each segment
19804 that is currently in use. The segment's selector is an index into a
19805 descriptor table; the table entry for that index holds the
19806 descriptor's base address and limit, and its attributes and access
19809 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19810 segment (used for both data and the stack), and a DOS segment (which
19811 allows access to DOS/BIOS data structures and absolute addresses in
19812 conventional memory). However, the DPMI host will usually define
19813 additional segments in order to support the DPMI environment.
19815 @cindex garbled pointers
19816 These commands allow to display entries from the descriptor tables.
19817 Without an argument, all entries from the specified table are
19818 displayed. An argument, which should be an integer expression, means
19819 display a single entry whose index is given by the argument. For
19820 example, here's a convenient way to display information about the
19821 debugged program's data segment:
19824 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19825 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19829 This comes in handy when you want to see whether a pointer is outside
19830 the data segment's limit (i.e.@: @dfn{garbled}).
19832 @cindex page tables display (MS-DOS)
19834 @itemx info dos pte
19835 These two commands display entries from, respectively, the Page
19836 Directory and the Page Tables. Page Directories and Page Tables are
19837 data structures which control how virtual memory addresses are mapped
19838 into physical addresses. A Page Table includes an entry for every
19839 page of memory that is mapped into the program's address space; there
19840 may be several Page Tables, each one holding up to 4096 entries. A
19841 Page Directory has up to 4096 entries, one each for every Page Table
19842 that is currently in use.
19844 Without an argument, @kbd{info dos pde} displays the entire Page
19845 Directory, and @kbd{info dos pte} displays all the entries in all of
19846 the Page Tables. An argument, an integer expression, given to the
19847 @kbd{info dos pde} command means display only that entry from the Page
19848 Directory table. An argument given to the @kbd{info dos pte} command
19849 means display entries from a single Page Table, the one pointed to by
19850 the specified entry in the Page Directory.
19852 @cindex direct memory access (DMA) on MS-DOS
19853 These commands are useful when your program uses @dfn{DMA} (Direct
19854 Memory Access), which needs physical addresses to program the DMA
19857 These commands are supported only with some DPMI servers.
19859 @cindex physical address from linear address
19860 @item info dos address-pte @var{addr}
19861 This command displays the Page Table entry for a specified linear
19862 address. The argument @var{addr} is a linear address which should
19863 already have the appropriate segment's base address added to it,
19864 because this command accepts addresses which may belong to @emph{any}
19865 segment. For example, here's how to display the Page Table entry for
19866 the page where a variable @code{i} is stored:
19869 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19870 @exdent @code{Page Table entry for address 0x11a00d30:}
19871 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19875 This says that @code{i} is stored at offset @code{0xd30} from the page
19876 whose physical base address is @code{0x02698000}, and shows all the
19877 attributes of that page.
19879 Note that you must cast the addresses of variables to a @code{char *},
19880 since otherwise the value of @code{__djgpp_base_address}, the base
19881 address of all variables and functions in a @sc{djgpp} program, will
19882 be added using the rules of C pointer arithmetics: if @code{i} is
19883 declared an @code{int}, @value{GDBN} will add 4 times the value of
19884 @code{__djgpp_base_address} to the address of @code{i}.
19886 Here's another example, it displays the Page Table entry for the
19890 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19891 @exdent @code{Page Table entry for address 0x29110:}
19892 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19896 (The @code{+ 3} offset is because the transfer buffer's address is the
19897 3rd member of the @code{_go32_info_block} structure.) The output
19898 clearly shows that this DPMI server maps the addresses in conventional
19899 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19900 linear (@code{0x29110}) addresses are identical.
19902 This command is supported only with some DPMI servers.
19905 @cindex DOS serial data link, remote debugging
19906 In addition to native debugging, the DJGPP port supports remote
19907 debugging via a serial data link. The following commands are specific
19908 to remote serial debugging in the DJGPP port of @value{GDBN}.
19911 @kindex set com1base
19912 @kindex set com1irq
19913 @kindex set com2base
19914 @kindex set com2irq
19915 @kindex set com3base
19916 @kindex set com3irq
19917 @kindex set com4base
19918 @kindex set com4irq
19919 @item set com1base @var{addr}
19920 This command sets the base I/O port address of the @file{COM1} serial
19923 @item set com1irq @var{irq}
19924 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19925 for the @file{COM1} serial port.
19927 There are similar commands @samp{set com2base}, @samp{set com3irq},
19928 etc.@: for setting the port address and the @code{IRQ} lines for the
19931 @kindex show com1base
19932 @kindex show com1irq
19933 @kindex show com2base
19934 @kindex show com2irq
19935 @kindex show com3base
19936 @kindex show com3irq
19937 @kindex show com4base
19938 @kindex show com4irq
19939 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19940 display the current settings of the base address and the @code{IRQ}
19941 lines used by the COM ports.
19944 @kindex info serial
19945 @cindex DOS serial port status
19946 This command prints the status of the 4 DOS serial ports. For each
19947 port, it prints whether it's active or not, its I/O base address and
19948 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19949 counts of various errors encountered so far.
19953 @node Cygwin Native
19954 @subsection Features for Debugging MS Windows PE Executables
19955 @cindex MS Windows debugging
19956 @cindex native Cygwin debugging
19957 @cindex Cygwin-specific commands
19959 @value{GDBN} supports native debugging of MS Windows programs, including
19960 DLLs with and without symbolic debugging information.
19962 @cindex Ctrl-BREAK, MS-Windows
19963 @cindex interrupt debuggee on MS-Windows
19964 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19965 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19966 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19967 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19968 sequence, which can be used to interrupt the debuggee even if it
19971 There are various additional Cygwin-specific commands, described in
19972 this section. Working with DLLs that have no debugging symbols is
19973 described in @ref{Non-debug DLL Symbols}.
19978 This is a prefix of MS Windows-specific commands which print
19979 information about the target system and important OS structures.
19981 @item info w32 selector
19982 This command displays information returned by
19983 the Win32 API @code{GetThreadSelectorEntry} function.
19984 It takes an optional argument that is evaluated to
19985 a long value to give the information about this given selector.
19986 Without argument, this command displays information
19987 about the six segment registers.
19989 @item info w32 thread-information-block
19990 This command displays thread specific information stored in the
19991 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19992 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19996 This is a Cygwin-specific alias of @code{info shared}.
19998 @kindex dll-symbols
20000 This command is deprecated and will be removed in future versions
20001 of @value{GDBN}. Use the @code{sharedlibrary} command instead.
20003 This command loads symbols from a dll similarly to
20004 add-sym command but without the need to specify a base address.
20006 @kindex set cygwin-exceptions
20007 @cindex debugging the Cygwin DLL
20008 @cindex Cygwin DLL, debugging
20009 @item set cygwin-exceptions @var{mode}
20010 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20011 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20012 @value{GDBN} will delay recognition of exceptions, and may ignore some
20013 exceptions which seem to be caused by internal Cygwin DLL
20014 ``bookkeeping''. This option is meant primarily for debugging the
20015 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20016 @value{GDBN} users with false @code{SIGSEGV} signals.
20018 @kindex show cygwin-exceptions
20019 @item show cygwin-exceptions
20020 Displays whether @value{GDBN} will break on exceptions that happen
20021 inside the Cygwin DLL itself.
20023 @kindex set new-console
20024 @item set new-console @var{mode}
20025 If @var{mode} is @code{on} the debuggee will
20026 be started in a new console on next start.
20027 If @var{mode} is @code{off}, the debuggee will
20028 be started in the same console as the debugger.
20030 @kindex show new-console
20031 @item show new-console
20032 Displays whether a new console is used
20033 when the debuggee is started.
20035 @kindex set new-group
20036 @item set new-group @var{mode}
20037 This boolean value controls whether the debuggee should
20038 start a new group or stay in the same group as the debugger.
20039 This affects the way the Windows OS handles
20042 @kindex show new-group
20043 @item show new-group
20044 Displays current value of new-group boolean.
20046 @kindex set debugevents
20047 @item set debugevents
20048 This boolean value adds debug output concerning kernel events related
20049 to the debuggee seen by the debugger. This includes events that
20050 signal thread and process creation and exit, DLL loading and
20051 unloading, console interrupts, and debugging messages produced by the
20052 Windows @code{OutputDebugString} API call.
20054 @kindex set debugexec
20055 @item set debugexec
20056 This boolean value adds debug output concerning execute events
20057 (such as resume thread) seen by the debugger.
20059 @kindex set debugexceptions
20060 @item set debugexceptions
20061 This boolean value adds debug output concerning exceptions in the
20062 debuggee seen by the debugger.
20064 @kindex set debugmemory
20065 @item set debugmemory
20066 This boolean value adds debug output concerning debuggee memory reads
20067 and writes by the debugger.
20071 This boolean values specifies whether the debuggee is called
20072 via a shell or directly (default value is on).
20076 Displays if the debuggee will be started with a shell.
20081 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20084 @node Non-debug DLL Symbols
20085 @subsubsection Support for DLLs without Debugging Symbols
20086 @cindex DLLs with no debugging symbols
20087 @cindex Minimal symbols and DLLs
20089 Very often on windows, some of the DLLs that your program relies on do
20090 not include symbolic debugging information (for example,
20091 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20092 symbols in a DLL, it relies on the minimal amount of symbolic
20093 information contained in the DLL's export table. This section
20094 describes working with such symbols, known internally to @value{GDBN} as
20095 ``minimal symbols''.
20097 Note that before the debugged program has started execution, no DLLs
20098 will have been loaded. The easiest way around this problem is simply to
20099 start the program --- either by setting a breakpoint or letting the
20100 program run once to completion.
20102 @subsubsection DLL Name Prefixes
20104 In keeping with the naming conventions used by the Microsoft debugging
20105 tools, DLL export symbols are made available with a prefix based on the
20106 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20107 also entered into the symbol table, so @code{CreateFileA} is often
20108 sufficient. In some cases there will be name clashes within a program
20109 (particularly if the executable itself includes full debugging symbols)
20110 necessitating the use of the fully qualified name when referring to the
20111 contents of the DLL. Use single-quotes around the name to avoid the
20112 exclamation mark (``!'') being interpreted as a language operator.
20114 Note that the internal name of the DLL may be all upper-case, even
20115 though the file name of the DLL is lower-case, or vice-versa. Since
20116 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20117 some confusion. If in doubt, try the @code{info functions} and
20118 @code{info variables} commands or even @code{maint print msymbols}
20119 (@pxref{Symbols}). Here's an example:
20122 (@value{GDBP}) info function CreateFileA
20123 All functions matching regular expression "CreateFileA":
20125 Non-debugging symbols:
20126 0x77e885f4 CreateFileA
20127 0x77e885f4 KERNEL32!CreateFileA
20131 (@value{GDBP}) info function !
20132 All functions matching regular expression "!":
20134 Non-debugging symbols:
20135 0x6100114c cygwin1!__assert
20136 0x61004034 cygwin1!_dll_crt0@@0
20137 0x61004240 cygwin1!dll_crt0(per_process *)
20141 @subsubsection Working with Minimal Symbols
20143 Symbols extracted from a DLL's export table do not contain very much
20144 type information. All that @value{GDBN} can do is guess whether a symbol
20145 refers to a function or variable depending on the linker section that
20146 contains the symbol. Also note that the actual contents of the memory
20147 contained in a DLL are not available unless the program is running. This
20148 means that you cannot examine the contents of a variable or disassemble
20149 a function within a DLL without a running program.
20151 Variables are generally treated as pointers and dereferenced
20152 automatically. For this reason, it is often necessary to prefix a
20153 variable name with the address-of operator (``&'') and provide explicit
20154 type information in the command. Here's an example of the type of
20158 (@value{GDBP}) print 'cygwin1!__argv'
20163 (@value{GDBP}) x 'cygwin1!__argv'
20164 0x10021610: "\230y\""
20167 And two possible solutions:
20170 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20171 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20175 (@value{GDBP}) x/2x &'cygwin1!__argv'
20176 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20177 (@value{GDBP}) x/x 0x10021608
20178 0x10021608: 0x0022fd98
20179 (@value{GDBP}) x/s 0x0022fd98
20180 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20183 Setting a break point within a DLL is possible even before the program
20184 starts execution. However, under these circumstances, @value{GDBN} can't
20185 examine the initial instructions of the function in order to skip the
20186 function's frame set-up code. You can work around this by using ``*&''
20187 to set the breakpoint at a raw memory address:
20190 (@value{GDBP}) break *&'python22!PyOS_Readline'
20191 Breakpoint 1 at 0x1e04eff0
20194 The author of these extensions is not entirely convinced that setting a
20195 break point within a shared DLL like @file{kernel32.dll} is completely
20199 @subsection Commands Specific to @sc{gnu} Hurd Systems
20200 @cindex @sc{gnu} Hurd debugging
20202 This subsection describes @value{GDBN} commands specific to the
20203 @sc{gnu} Hurd native debugging.
20208 @kindex set signals@r{, Hurd command}
20209 @kindex set sigs@r{, Hurd command}
20210 This command toggles the state of inferior signal interception by
20211 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20212 affected by this command. @code{sigs} is a shorthand alias for
20217 @kindex show signals@r{, Hurd command}
20218 @kindex show sigs@r{, Hurd command}
20219 Show the current state of intercepting inferior's signals.
20221 @item set signal-thread
20222 @itemx set sigthread
20223 @kindex set signal-thread
20224 @kindex set sigthread
20225 This command tells @value{GDBN} which thread is the @code{libc} signal
20226 thread. That thread is run when a signal is delivered to a running
20227 process. @code{set sigthread} is the shorthand alias of @code{set
20230 @item show signal-thread
20231 @itemx show sigthread
20232 @kindex show signal-thread
20233 @kindex show sigthread
20234 These two commands show which thread will run when the inferior is
20235 delivered a signal.
20238 @kindex set stopped@r{, Hurd command}
20239 This commands tells @value{GDBN} that the inferior process is stopped,
20240 as with the @code{SIGSTOP} signal. The stopped process can be
20241 continued by delivering a signal to it.
20244 @kindex show stopped@r{, Hurd command}
20245 This command shows whether @value{GDBN} thinks the debuggee is
20248 @item set exceptions
20249 @kindex set exceptions@r{, Hurd command}
20250 Use this command to turn off trapping of exceptions in the inferior.
20251 When exception trapping is off, neither breakpoints nor
20252 single-stepping will work. To restore the default, set exception
20255 @item show exceptions
20256 @kindex show exceptions@r{, Hurd command}
20257 Show the current state of trapping exceptions in the inferior.
20259 @item set task pause
20260 @kindex set task@r{, Hurd commands}
20261 @cindex task attributes (@sc{gnu} Hurd)
20262 @cindex pause current task (@sc{gnu} Hurd)
20263 This command toggles task suspension when @value{GDBN} has control.
20264 Setting it to on takes effect immediately, and the task is suspended
20265 whenever @value{GDBN} gets control. Setting it to off will take
20266 effect the next time the inferior is continued. If this option is set
20267 to off, you can use @code{set thread default pause on} or @code{set
20268 thread pause on} (see below) to pause individual threads.
20270 @item show task pause
20271 @kindex show task@r{, Hurd commands}
20272 Show the current state of task suspension.
20274 @item set task detach-suspend-count
20275 @cindex task suspend count
20276 @cindex detach from task, @sc{gnu} Hurd
20277 This command sets the suspend count the task will be left with when
20278 @value{GDBN} detaches from it.
20280 @item show task detach-suspend-count
20281 Show the suspend count the task will be left with when detaching.
20283 @item set task exception-port
20284 @itemx set task excp
20285 @cindex task exception port, @sc{gnu} Hurd
20286 This command sets the task exception port to which @value{GDBN} will
20287 forward exceptions. The argument should be the value of the @dfn{send
20288 rights} of the task. @code{set task excp} is a shorthand alias.
20290 @item set noninvasive
20291 @cindex noninvasive task options
20292 This command switches @value{GDBN} to a mode that is the least
20293 invasive as far as interfering with the inferior is concerned. This
20294 is the same as using @code{set task pause}, @code{set exceptions}, and
20295 @code{set signals} to values opposite to the defaults.
20297 @item info send-rights
20298 @itemx info receive-rights
20299 @itemx info port-rights
20300 @itemx info port-sets
20301 @itemx info dead-names
20304 @cindex send rights, @sc{gnu} Hurd
20305 @cindex receive rights, @sc{gnu} Hurd
20306 @cindex port rights, @sc{gnu} Hurd
20307 @cindex port sets, @sc{gnu} Hurd
20308 @cindex dead names, @sc{gnu} Hurd
20309 These commands display information about, respectively, send rights,
20310 receive rights, port rights, port sets, and dead names of a task.
20311 There are also shorthand aliases: @code{info ports} for @code{info
20312 port-rights} and @code{info psets} for @code{info port-sets}.
20314 @item set thread pause
20315 @kindex set thread@r{, Hurd command}
20316 @cindex thread properties, @sc{gnu} Hurd
20317 @cindex pause current thread (@sc{gnu} Hurd)
20318 This command toggles current thread suspension when @value{GDBN} has
20319 control. Setting it to on takes effect immediately, and the current
20320 thread is suspended whenever @value{GDBN} gets control. Setting it to
20321 off will take effect the next time the inferior is continued.
20322 Normally, this command has no effect, since when @value{GDBN} has
20323 control, the whole task is suspended. However, if you used @code{set
20324 task pause off} (see above), this command comes in handy to suspend
20325 only the current thread.
20327 @item show thread pause
20328 @kindex show thread@r{, Hurd command}
20329 This command shows the state of current thread suspension.
20331 @item set thread run
20332 This command sets whether the current thread is allowed to run.
20334 @item show thread run
20335 Show whether the current thread is allowed to run.
20337 @item set thread detach-suspend-count
20338 @cindex thread suspend count, @sc{gnu} Hurd
20339 @cindex detach from thread, @sc{gnu} Hurd
20340 This command sets the suspend count @value{GDBN} will leave on a
20341 thread when detaching. This number is relative to the suspend count
20342 found by @value{GDBN} when it notices the thread; use @code{set thread
20343 takeover-suspend-count} to force it to an absolute value.
20345 @item show thread detach-suspend-count
20346 Show the suspend count @value{GDBN} will leave on the thread when
20349 @item set thread exception-port
20350 @itemx set thread excp
20351 Set the thread exception port to which to forward exceptions. This
20352 overrides the port set by @code{set task exception-port} (see above).
20353 @code{set thread excp} is the shorthand alias.
20355 @item set thread takeover-suspend-count
20356 Normally, @value{GDBN}'s thread suspend counts are relative to the
20357 value @value{GDBN} finds when it notices each thread. This command
20358 changes the suspend counts to be absolute instead.
20360 @item set thread default
20361 @itemx show thread default
20362 @cindex thread default settings, @sc{gnu} Hurd
20363 Each of the above @code{set thread} commands has a @code{set thread
20364 default} counterpart (e.g., @code{set thread default pause}, @code{set
20365 thread default exception-port}, etc.). The @code{thread default}
20366 variety of commands sets the default thread properties for all
20367 threads; you can then change the properties of individual threads with
20368 the non-default commands.
20375 @value{GDBN} provides the following commands specific to the Darwin target:
20378 @item set debug darwin @var{num}
20379 @kindex set debug darwin
20380 When set to a non zero value, enables debugging messages specific to
20381 the Darwin support. Higher values produce more verbose output.
20383 @item show debug darwin
20384 @kindex show debug darwin
20385 Show the current state of Darwin messages.
20387 @item set debug mach-o @var{num}
20388 @kindex set debug mach-o
20389 When set to a non zero value, enables debugging messages while
20390 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20391 file format used on Darwin for object and executable files.) Higher
20392 values produce more verbose output. This is a command to diagnose
20393 problems internal to @value{GDBN} and should not be needed in normal
20396 @item show debug mach-o
20397 @kindex show debug mach-o
20398 Show the current state of Mach-O file messages.
20400 @item set mach-exceptions on
20401 @itemx set mach-exceptions off
20402 @kindex set mach-exceptions
20403 On Darwin, faults are first reported as a Mach exception and are then
20404 mapped to a Posix signal. Use this command to turn on trapping of
20405 Mach exceptions in the inferior. This might be sometimes useful to
20406 better understand the cause of a fault. The default is off.
20408 @item show mach-exceptions
20409 @kindex show mach-exceptions
20410 Show the current state of exceptions trapping.
20415 @section Embedded Operating Systems
20417 This section describes configurations involving the debugging of
20418 embedded operating systems that are available for several different
20422 * VxWorks:: Using @value{GDBN} with VxWorks
20425 @value{GDBN} includes the ability to debug programs running on
20426 various real-time operating systems.
20429 @subsection Using @value{GDBN} with VxWorks
20435 @kindex target vxworks
20436 @item target vxworks @var{machinename}
20437 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20438 is the target system's machine name or IP address.
20442 On VxWorks, @code{load} links @var{filename} dynamically on the
20443 current target system as well as adding its symbols in @value{GDBN}.
20445 @value{GDBN} enables developers to spawn and debug tasks running on networked
20446 VxWorks targets from a Unix host. Already-running tasks spawned from
20447 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20448 both the Unix host and on the VxWorks target. The program
20449 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20450 installed with the name @code{vxgdb}, to distinguish it from a
20451 @value{GDBN} for debugging programs on the host itself.)
20454 @item VxWorks-timeout @var{args}
20455 @kindex vxworks-timeout
20456 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20457 This option is set by the user, and @var{args} represents the number of
20458 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20459 your VxWorks target is a slow software simulator or is on the far side
20460 of a thin network line.
20463 The following information on connecting to VxWorks was current when
20464 this manual was produced; newer releases of VxWorks may use revised
20467 @findex INCLUDE_RDB
20468 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20469 to include the remote debugging interface routines in the VxWorks
20470 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20471 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20472 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20473 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20474 information on configuring and remaking VxWorks, see the manufacturer's
20476 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20478 Once you have included @file{rdb.a} in your VxWorks system image and set
20479 your Unix execution search path to find @value{GDBN}, you are ready to
20480 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20481 @code{vxgdb}, depending on your installation).
20483 @value{GDBN} comes up showing the prompt:
20490 * VxWorks Connection:: Connecting to VxWorks
20491 * VxWorks Download:: VxWorks download
20492 * VxWorks Attach:: Running tasks
20495 @node VxWorks Connection
20496 @subsubsection Connecting to VxWorks
20498 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20499 network. To connect to a target whose host name is ``@code{tt}'', type:
20502 (vxgdb) target vxworks tt
20506 @value{GDBN} displays messages like these:
20509 Attaching remote machine across net...
20514 @value{GDBN} then attempts to read the symbol tables of any object modules
20515 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20516 these files by searching the directories listed in the command search
20517 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20518 to find an object file, it displays a message such as:
20521 prog.o: No such file or directory.
20524 When this happens, add the appropriate directory to the search path with
20525 the @value{GDBN} command @code{path}, and execute the @code{target}
20528 @node VxWorks Download
20529 @subsubsection VxWorks Download
20531 @cindex download to VxWorks
20532 If you have connected to the VxWorks target and you want to debug an
20533 object that has not yet been loaded, you can use the @value{GDBN}
20534 @code{load} command to download a file from Unix to VxWorks
20535 incrementally. The object file given as an argument to the @code{load}
20536 command is actually opened twice: first by the VxWorks target in order
20537 to download the code, then by @value{GDBN} in order to read the symbol
20538 table. This can lead to problems if the current working directories on
20539 the two systems differ. If both systems have NFS mounted the same
20540 filesystems, you can avoid these problems by using absolute paths.
20541 Otherwise, it is simplest to set the working directory on both systems
20542 to the directory in which the object file resides, and then to reference
20543 the file by its name, without any path. For instance, a program
20544 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20545 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20546 program, type this on VxWorks:
20549 -> cd "@var{vxpath}/vw/demo/rdb"
20553 Then, in @value{GDBN}, type:
20556 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20557 (vxgdb) load prog.o
20560 @value{GDBN} displays a response similar to this:
20563 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20566 You can also use the @code{load} command to reload an object module
20567 after editing and recompiling the corresponding source file. Note that
20568 this makes @value{GDBN} delete all currently-defined breakpoints,
20569 auto-displays, and convenience variables, and to clear the value
20570 history. (This is necessary in order to preserve the integrity of
20571 debugger's data structures that reference the target system's symbol
20574 @node VxWorks Attach
20575 @subsubsection Running Tasks
20577 @cindex running VxWorks tasks
20578 You can also attach to an existing task using the @code{attach} command as
20582 (vxgdb) attach @var{task}
20586 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20587 or suspended when you attach to it. Running tasks are suspended at
20588 the time of attachment.
20590 @node Embedded Processors
20591 @section Embedded Processors
20593 This section goes into details specific to particular embedded
20596 @cindex send command to simulator
20597 Whenever a specific embedded processor has a simulator, @value{GDBN}
20598 allows to send an arbitrary command to the simulator.
20601 @item sim @var{command}
20602 @kindex sim@r{, a command}
20603 Send an arbitrary @var{command} string to the simulator. Consult the
20604 documentation for the specific simulator in use for information about
20605 acceptable commands.
20611 * M32R/D:: Renesas M32R/D
20612 * M68K:: Motorola M68K
20613 * MicroBlaze:: Xilinx MicroBlaze
20614 * MIPS Embedded:: MIPS Embedded
20615 * PowerPC Embedded:: PowerPC Embedded
20616 * PA:: HP PA Embedded
20617 * Sparclet:: Tsqware Sparclet
20618 * Sparclite:: Fujitsu Sparclite
20619 * Z8000:: Zilog Z8000
20622 * Super-H:: Renesas Super-H
20631 @item target rdi @var{dev}
20632 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20633 use this target to communicate with both boards running the Angel
20634 monitor, or with the EmbeddedICE JTAG debug device.
20637 @item target rdp @var{dev}
20642 @value{GDBN} provides the following ARM-specific commands:
20645 @item set arm disassembler
20647 This commands selects from a list of disassembly styles. The
20648 @code{"std"} style is the standard style.
20650 @item show arm disassembler
20652 Show the current disassembly style.
20654 @item set arm apcs32
20655 @cindex ARM 32-bit mode
20656 This command toggles ARM operation mode between 32-bit and 26-bit.
20658 @item show arm apcs32
20659 Display the current usage of the ARM 32-bit mode.
20661 @item set arm fpu @var{fputype}
20662 This command sets the ARM floating-point unit (FPU) type. The
20663 argument @var{fputype} can be one of these:
20667 Determine the FPU type by querying the OS ABI.
20669 Software FPU, with mixed-endian doubles on little-endian ARM
20672 GCC-compiled FPA co-processor.
20674 Software FPU with pure-endian doubles.
20680 Show the current type of the FPU.
20683 This command forces @value{GDBN} to use the specified ABI.
20686 Show the currently used ABI.
20688 @item set arm fallback-mode (arm|thumb|auto)
20689 @value{GDBN} uses the symbol table, when available, to determine
20690 whether instructions are ARM or Thumb. This command controls
20691 @value{GDBN}'s default behavior when the symbol table is not
20692 available. The default is @samp{auto}, which causes @value{GDBN} to
20693 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20696 @item show arm fallback-mode
20697 Show the current fallback instruction mode.
20699 @item set arm force-mode (arm|thumb|auto)
20700 This command overrides use of the symbol table to determine whether
20701 instructions are ARM or Thumb. The default is @samp{auto}, which
20702 causes @value{GDBN} to use the symbol table and then the setting
20703 of @samp{set arm fallback-mode}.
20705 @item show arm force-mode
20706 Show the current forced instruction mode.
20708 @item set debug arm
20709 Toggle whether to display ARM-specific debugging messages from the ARM
20710 target support subsystem.
20712 @item show debug arm
20713 Show whether ARM-specific debugging messages are enabled.
20716 The following commands are available when an ARM target is debugged
20717 using the RDI interface:
20720 @item rdilogfile @r{[}@var{file}@r{]}
20722 @cindex ADP (Angel Debugger Protocol) logging
20723 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20724 With an argument, sets the log file to the specified @var{file}. With
20725 no argument, show the current log file name. The default log file is
20728 @item rdilogenable @r{[}@var{arg}@r{]}
20729 @kindex rdilogenable
20730 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20731 enables logging, with an argument 0 or @code{"no"} disables it. With
20732 no arguments displays the current setting. When logging is enabled,
20733 ADP packets exchanged between @value{GDBN} and the RDI target device
20734 are logged to a file.
20736 @item set rdiromatzero
20737 @kindex set rdiromatzero
20738 @cindex ROM at zero address, RDI
20739 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20740 vector catching is disabled, so that zero address can be used. If off
20741 (the default), vector catching is enabled. For this command to take
20742 effect, it needs to be invoked prior to the @code{target rdi} command.
20744 @item show rdiromatzero
20745 @kindex show rdiromatzero
20746 Show the current setting of ROM at zero address.
20748 @item set rdiheartbeat
20749 @kindex set rdiheartbeat
20750 @cindex RDI heartbeat
20751 Enable or disable RDI heartbeat packets. It is not recommended to
20752 turn on this option, since it confuses ARM and EPI JTAG interface, as
20753 well as the Angel monitor.
20755 @item show rdiheartbeat
20756 @kindex show rdiheartbeat
20757 Show the setting of RDI heartbeat packets.
20761 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20762 The @value{GDBN} ARM simulator accepts the following optional arguments.
20765 @item --swi-support=@var{type}
20766 Tell the simulator which SWI interfaces to support. The argument
20767 @var{type} may be a comma separated list of the following values.
20768 The default value is @code{all}.
20781 @subsection Renesas M32R/D and M32R/SDI
20784 @kindex target m32r
20785 @item target m32r @var{dev}
20786 Renesas M32R/D ROM monitor.
20788 @kindex target m32rsdi
20789 @item target m32rsdi @var{dev}
20790 Renesas M32R SDI server, connected via parallel port to the board.
20793 The following @value{GDBN} commands are specific to the M32R monitor:
20796 @item set download-path @var{path}
20797 @kindex set download-path
20798 @cindex find downloadable @sc{srec} files (M32R)
20799 Set the default path for finding downloadable @sc{srec} files.
20801 @item show download-path
20802 @kindex show download-path
20803 Show the default path for downloadable @sc{srec} files.
20805 @item set board-address @var{addr}
20806 @kindex set board-address
20807 @cindex M32-EVA target board address
20808 Set the IP address for the M32R-EVA target board.
20810 @item show board-address
20811 @kindex show board-address
20812 Show the current IP address of the target board.
20814 @item set server-address @var{addr}
20815 @kindex set server-address
20816 @cindex download server address (M32R)
20817 Set the IP address for the download server, which is the @value{GDBN}'s
20820 @item show server-address
20821 @kindex show server-address
20822 Display the IP address of the download server.
20824 @item upload @r{[}@var{file}@r{]}
20825 @kindex upload@r{, M32R}
20826 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20827 upload capability. If no @var{file} argument is given, the current
20828 executable file is uploaded.
20830 @item tload @r{[}@var{file}@r{]}
20831 @kindex tload@r{, M32R}
20832 Test the @code{upload} command.
20835 The following commands are available for M32R/SDI:
20840 @cindex reset SDI connection, M32R
20841 This command resets the SDI connection.
20845 This command shows the SDI connection status.
20848 @kindex debug_chaos
20849 @cindex M32R/Chaos debugging
20850 Instructs the remote that M32R/Chaos debugging is to be used.
20852 @item use_debug_dma
20853 @kindex use_debug_dma
20854 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20857 @kindex use_mon_code
20858 Instructs the remote to use the MON_CODE method of accessing memory.
20861 @kindex use_ib_break
20862 Instructs the remote to set breakpoints by IB break.
20864 @item use_dbt_break
20865 @kindex use_dbt_break
20866 Instructs the remote to set breakpoints by DBT.
20872 The Motorola m68k configuration includes ColdFire support, and a
20873 target command for the following ROM monitor.
20877 @kindex target dbug
20878 @item target dbug @var{dev}
20879 dBUG ROM monitor for Motorola ColdFire.
20884 @subsection MicroBlaze
20885 @cindex Xilinx MicroBlaze
20886 @cindex XMD, Xilinx Microprocessor Debugger
20888 The MicroBlaze is a soft-core processor supported on various Xilinx
20889 FPGAs, such as Spartan or Virtex series. Boards with these processors
20890 usually have JTAG ports which connect to a host system running the Xilinx
20891 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20892 This host system is used to download the configuration bitstream to
20893 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20894 communicates with the target board using the JTAG interface and
20895 presents a @code{gdbserver} interface to the board. By default
20896 @code{xmd} uses port @code{1234}. (While it is possible to change
20897 this default port, it requires the use of undocumented @code{xmd}
20898 commands. Contact Xilinx support if you need to do this.)
20900 Use these GDB commands to connect to the MicroBlaze target processor.
20903 @item target remote :1234
20904 Use this command to connect to the target if you are running @value{GDBN}
20905 on the same system as @code{xmd}.
20907 @item target remote @var{xmd-host}:1234
20908 Use this command to connect to the target if it is connected to @code{xmd}
20909 running on a different system named @var{xmd-host}.
20912 Use this command to download a program to the MicroBlaze target.
20914 @item set debug microblaze @var{n}
20915 Enable MicroBlaze-specific debugging messages if non-zero.
20917 @item show debug microblaze @var{n}
20918 Show MicroBlaze-specific debugging level.
20921 @node MIPS Embedded
20922 @subsection @acronym{MIPS} Embedded
20924 @cindex @acronym{MIPS} boards
20925 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20926 @acronym{MIPS} board attached to a serial line. This is available when
20927 you configure @value{GDBN} with @samp{--target=mips-elf}.
20930 Use these @value{GDBN} commands to specify the connection to your target board:
20933 @item target mips @var{port}
20934 @kindex target mips @var{port}
20935 To run a program on the board, start up @code{@value{GDBP}} with the
20936 name of your program as the argument. To connect to the board, use the
20937 command @samp{target mips @var{port}}, where @var{port} is the name of
20938 the serial port connected to the board. If the program has not already
20939 been downloaded to the board, you may use the @code{load} command to
20940 download it. You can then use all the usual @value{GDBN} commands.
20942 For example, this sequence connects to the target board through a serial
20943 port, and loads and runs a program called @var{prog} through the
20947 host$ @value{GDBP} @var{prog}
20948 @value{GDBN} is free software and @dots{}
20949 (@value{GDBP}) target mips /dev/ttyb
20950 (@value{GDBP}) load @var{prog}
20954 @item target mips @var{hostname}:@var{portnumber}
20955 On some @value{GDBN} host configurations, you can specify a TCP
20956 connection (for instance, to a serial line managed by a terminal
20957 concentrator) instead of a serial port, using the syntax
20958 @samp{@var{hostname}:@var{portnumber}}.
20960 @item target pmon @var{port}
20961 @kindex target pmon @var{port}
20964 @item target ddb @var{port}
20965 @kindex target ddb @var{port}
20966 NEC's DDB variant of PMON for Vr4300.
20968 @item target lsi @var{port}
20969 @kindex target lsi @var{port}
20970 LSI variant of PMON.
20972 @kindex target r3900
20973 @item target r3900 @var{dev}
20974 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20976 @kindex target array
20977 @item target array @var{dev}
20978 Array Tech LSI33K RAID controller board.
20984 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20987 @item set mipsfpu double
20988 @itemx set mipsfpu single
20989 @itemx set mipsfpu none
20990 @itemx set mipsfpu auto
20991 @itemx show mipsfpu
20992 @kindex set mipsfpu
20993 @kindex show mipsfpu
20994 @cindex @acronym{MIPS} remote floating point
20995 @cindex floating point, @acronym{MIPS} remote
20996 If your target board does not support the @acronym{MIPS} floating point
20997 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20998 need this, you may wish to put the command in your @value{GDBN} init
20999 file). This tells @value{GDBN} how to find the return value of
21000 functions which return floating point values. It also allows
21001 @value{GDBN} to avoid saving the floating point registers when calling
21002 functions on the board. If you are using a floating point coprocessor
21003 with only single precision floating point support, as on the @sc{r4650}
21004 processor, use the command @samp{set mipsfpu single}. The default
21005 double precision floating point coprocessor may be selected using
21006 @samp{set mipsfpu double}.
21008 In previous versions the only choices were double precision or no
21009 floating point, so @samp{set mipsfpu on} will select double precision
21010 and @samp{set mipsfpu off} will select no floating point.
21012 As usual, you can inquire about the @code{mipsfpu} variable with
21013 @samp{show mipsfpu}.
21015 @item set timeout @var{seconds}
21016 @itemx set retransmit-timeout @var{seconds}
21017 @itemx show timeout
21018 @itemx show retransmit-timeout
21019 @cindex @code{timeout}, @acronym{MIPS} protocol
21020 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21021 @kindex set timeout
21022 @kindex show timeout
21023 @kindex set retransmit-timeout
21024 @kindex show retransmit-timeout
21025 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21026 remote protocol, with the @code{set timeout @var{seconds}} command. The
21027 default is 5 seconds. Similarly, you can control the timeout used while
21028 waiting for an acknowledgment of a packet with the @code{set
21029 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21030 You can inspect both values with @code{show timeout} and @code{show
21031 retransmit-timeout}. (These commands are @emph{only} available when
21032 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21034 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21035 is waiting for your program to stop. In that case, @value{GDBN} waits
21036 forever because it has no way of knowing how long the program is going
21037 to run before stopping.
21039 @item set syn-garbage-limit @var{num}
21040 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21041 @cindex synchronize with remote @acronym{MIPS} target
21042 Limit the maximum number of characters @value{GDBN} should ignore when
21043 it tries to synchronize with the remote target. The default is 10
21044 characters. Setting the limit to -1 means there's no limit.
21046 @item show syn-garbage-limit
21047 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21048 Show the current limit on the number of characters to ignore when
21049 trying to synchronize with the remote system.
21051 @item set monitor-prompt @var{prompt}
21052 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21053 @cindex remote monitor prompt
21054 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21055 remote monitor. The default depends on the target:
21065 @item show monitor-prompt
21066 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21067 Show the current strings @value{GDBN} expects as the prompt from the
21070 @item set monitor-warnings
21071 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21072 Enable or disable monitor warnings about hardware breakpoints. This
21073 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21074 display warning messages whose codes are returned by the @code{lsi}
21075 PMON monitor for breakpoint commands.
21077 @item show monitor-warnings
21078 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21079 Show the current setting of printing monitor warnings.
21081 @item pmon @var{command}
21082 @kindex pmon@r{, @acronym{MIPS} remote}
21083 @cindex send PMON command
21084 This command allows sending an arbitrary @var{command} string to the
21085 monitor. The monitor must be in debug mode for this to work.
21088 @node PowerPC Embedded
21089 @subsection PowerPC Embedded
21091 @cindex DVC register
21092 @value{GDBN} supports using the DVC (Data Value Compare) register to
21093 implement in hardware simple hardware watchpoint conditions of the form:
21096 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21097 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21100 The DVC register will be automatically used when @value{GDBN} detects
21101 such pattern in a condition expression, and the created watchpoint uses one
21102 debug register (either the @code{exact-watchpoints} option is on and the
21103 variable is scalar, or the variable has a length of one byte). This feature
21104 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21107 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21108 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21109 in which case watchpoints using only one debug register are created when
21110 watching variables of scalar types.
21112 You can create an artificial array to watch an arbitrary memory
21113 region using one of the following commands (@pxref{Expressions}):
21116 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21117 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21120 PowerPC embedded processors support masked watchpoints. See the discussion
21121 about the @code{mask} argument in @ref{Set Watchpoints}.
21123 @cindex ranged breakpoint
21124 PowerPC embedded processors support hardware accelerated
21125 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21126 the inferior whenever it executes an instruction at any address within
21127 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21128 use the @code{break-range} command.
21130 @value{GDBN} provides the following PowerPC-specific commands:
21133 @kindex break-range
21134 @item break-range @var{start-location}, @var{end-location}
21135 Set a breakpoint for an address range given by
21136 @var{start-location} and @var{end-location}, which can specify a function name,
21137 a line number, an offset of lines from the current line or from the start
21138 location, or an address of an instruction (see @ref{Specify Location},
21139 for a list of all the possible ways to specify a @var{location}.)
21140 The breakpoint will stop execution of the inferior whenever it
21141 executes an instruction at any address within the specified range,
21142 (including @var{start-location} and @var{end-location}.)
21144 @kindex set powerpc
21145 @item set powerpc soft-float
21146 @itemx show powerpc soft-float
21147 Force @value{GDBN} to use (or not use) a software floating point calling
21148 convention. By default, @value{GDBN} selects the calling convention based
21149 on the selected architecture and the provided executable file.
21151 @item set powerpc vector-abi
21152 @itemx show powerpc vector-abi
21153 Force @value{GDBN} to use the specified calling convention for vector
21154 arguments and return values. The valid options are @samp{auto};
21155 @samp{generic}, to avoid vector registers even if they are present;
21156 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21157 registers. By default, @value{GDBN} selects the calling convention
21158 based on the selected architecture and the provided executable file.
21160 @item set powerpc exact-watchpoints
21161 @itemx show powerpc exact-watchpoints
21162 Allow @value{GDBN} to use only one debug register when watching a variable
21163 of scalar type, thus assuming that the variable is accessed through the
21164 address of its first byte.
21166 @kindex target dink32
21167 @item target dink32 @var{dev}
21168 DINK32 ROM monitor.
21170 @kindex target ppcbug
21171 @item target ppcbug @var{dev}
21172 @kindex target ppcbug1
21173 @item target ppcbug1 @var{dev}
21174 PPCBUG ROM monitor for PowerPC.
21177 @item target sds @var{dev}
21178 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21181 @cindex SDS protocol
21182 The following commands specific to the SDS protocol are supported
21186 @item set sdstimeout @var{nsec}
21187 @kindex set sdstimeout
21188 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21189 default is 2 seconds.
21191 @item show sdstimeout
21192 @kindex show sdstimeout
21193 Show the current value of the SDS timeout.
21195 @item sds @var{command}
21196 @kindex sds@r{, a command}
21197 Send the specified @var{command} string to the SDS monitor.
21202 @subsection HP PA Embedded
21206 @kindex target op50n
21207 @item target op50n @var{dev}
21208 OP50N monitor, running on an OKI HPPA board.
21210 @kindex target w89k
21211 @item target w89k @var{dev}
21212 W89K monitor, running on a Winbond HPPA board.
21217 @subsection Tsqware Sparclet
21221 @value{GDBN} enables developers to debug tasks running on
21222 Sparclet targets from a Unix host.
21223 @value{GDBN} uses code that runs on
21224 both the Unix host and on the Sparclet target. The program
21225 @code{@value{GDBP}} is installed and executed on the Unix host.
21228 @item remotetimeout @var{args}
21229 @kindex remotetimeout
21230 @value{GDBN} supports the option @code{remotetimeout}.
21231 This option is set by the user, and @var{args} represents the number of
21232 seconds @value{GDBN} waits for responses.
21235 @cindex compiling, on Sparclet
21236 When compiling for debugging, include the options @samp{-g} to get debug
21237 information and @samp{-Ttext} to relocate the program to where you wish to
21238 load it on the target. You may also want to add the options @samp{-n} or
21239 @samp{-N} in order to reduce the size of the sections. Example:
21242 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21245 You can use @code{objdump} to verify that the addresses are what you intended:
21248 sparclet-aout-objdump --headers --syms prog
21251 @cindex running, on Sparclet
21253 your Unix execution search path to find @value{GDBN}, you are ready to
21254 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21255 (or @code{sparclet-aout-gdb}, depending on your installation).
21257 @value{GDBN} comes up showing the prompt:
21264 * Sparclet File:: Setting the file to debug
21265 * Sparclet Connection:: Connecting to Sparclet
21266 * Sparclet Download:: Sparclet download
21267 * Sparclet Execution:: Running and debugging
21270 @node Sparclet File
21271 @subsubsection Setting File to Debug
21273 The @value{GDBN} command @code{file} lets you choose with program to debug.
21276 (gdbslet) file prog
21280 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21281 @value{GDBN} locates
21282 the file by searching the directories listed in the command search
21284 If the file was compiled with debug information (option @samp{-g}), source
21285 files will be searched as well.
21286 @value{GDBN} locates
21287 the source files by searching the directories listed in the directory search
21288 path (@pxref{Environment, ,Your Program's Environment}).
21290 to find a file, it displays a message such as:
21293 prog: No such file or directory.
21296 When this happens, add the appropriate directories to the search paths with
21297 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21298 @code{target} command again.
21300 @node Sparclet Connection
21301 @subsubsection Connecting to Sparclet
21303 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21304 To connect to a target on serial port ``@code{ttya}'', type:
21307 (gdbslet) target sparclet /dev/ttya
21308 Remote target sparclet connected to /dev/ttya
21309 main () at ../prog.c:3
21313 @value{GDBN} displays messages like these:
21319 @node Sparclet Download
21320 @subsubsection Sparclet Download
21322 @cindex download to Sparclet
21323 Once connected to the Sparclet target,
21324 you can use the @value{GDBN}
21325 @code{load} command to download the file from the host to the target.
21326 The file name and load offset should be given as arguments to the @code{load}
21328 Since the file format is aout, the program must be loaded to the starting
21329 address. You can use @code{objdump} to find out what this value is. The load
21330 offset is an offset which is added to the VMA (virtual memory address)
21331 of each of the file's sections.
21332 For instance, if the program
21333 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21334 and bss at 0x12010170, in @value{GDBN}, type:
21337 (gdbslet) load prog 0x12010000
21338 Loading section .text, size 0xdb0 vma 0x12010000
21341 If the code is loaded at a different address then what the program was linked
21342 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21343 to tell @value{GDBN} where to map the symbol table.
21345 @node Sparclet Execution
21346 @subsubsection Running and Debugging
21348 @cindex running and debugging Sparclet programs
21349 You can now begin debugging the task using @value{GDBN}'s execution control
21350 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21351 manual for the list of commands.
21355 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21357 Starting program: prog
21358 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21359 3 char *symarg = 0;
21361 4 char *execarg = "hello!";
21366 @subsection Fujitsu Sparclite
21370 @kindex target sparclite
21371 @item target sparclite @var{dev}
21372 Fujitsu sparclite boards, used only for the purpose of loading.
21373 You must use an additional command to debug the program.
21374 For example: target remote @var{dev} using @value{GDBN} standard
21380 @subsection Zilog Z8000
21383 @cindex simulator, Z8000
21384 @cindex Zilog Z8000 simulator
21386 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21389 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21390 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21391 segmented variant). The simulator recognizes which architecture is
21392 appropriate by inspecting the object code.
21395 @item target sim @var{args}
21397 @kindex target sim@r{, with Z8000}
21398 Debug programs on a simulated CPU. If the simulator supports setup
21399 options, specify them via @var{args}.
21403 After specifying this target, you can debug programs for the simulated
21404 CPU in the same style as programs for your host computer; use the
21405 @code{file} command to load a new program image, the @code{run} command
21406 to run your program, and so on.
21408 As well as making available all the usual machine registers
21409 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21410 additional items of information as specially named registers:
21415 Counts clock-ticks in the simulator.
21418 Counts instructions run in the simulator.
21421 Execution time in 60ths of a second.
21425 You can refer to these values in @value{GDBN} expressions with the usual
21426 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21427 conditional breakpoint that suspends only after at least 5000
21428 simulated clock ticks.
21431 @subsection Atmel AVR
21434 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21435 following AVR-specific commands:
21438 @item info io_registers
21439 @kindex info io_registers@r{, AVR}
21440 @cindex I/O registers (Atmel AVR)
21441 This command displays information about the AVR I/O registers. For
21442 each register, @value{GDBN} prints its number and value.
21449 When configured for debugging CRIS, @value{GDBN} provides the
21450 following CRIS-specific commands:
21453 @item set cris-version @var{ver}
21454 @cindex CRIS version
21455 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21456 The CRIS version affects register names and sizes. This command is useful in
21457 case autodetection of the CRIS version fails.
21459 @item show cris-version
21460 Show the current CRIS version.
21462 @item set cris-dwarf2-cfi
21463 @cindex DWARF-2 CFI and CRIS
21464 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21465 Change to @samp{off} when using @code{gcc-cris} whose version is below
21468 @item show cris-dwarf2-cfi
21469 Show the current state of using DWARF-2 CFI.
21471 @item set cris-mode @var{mode}
21473 Set the current CRIS mode to @var{mode}. It should only be changed when
21474 debugging in guru mode, in which case it should be set to
21475 @samp{guru} (the default is @samp{normal}).
21477 @item show cris-mode
21478 Show the current CRIS mode.
21482 @subsection Renesas Super-H
21485 For the Renesas Super-H processor, @value{GDBN} provides these
21489 @item set sh calling-convention @var{convention}
21490 @kindex set sh calling-convention
21491 Set the calling-convention used when calling functions from @value{GDBN}.
21492 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21493 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21494 convention. If the DWARF-2 information of the called function specifies
21495 that the function follows the Renesas calling convention, the function
21496 is called using the Renesas calling convention. If the calling convention
21497 is set to @samp{renesas}, the Renesas calling convention is always used,
21498 regardless of the DWARF-2 information. This can be used to override the
21499 default of @samp{gcc} if debug information is missing, or the compiler
21500 does not emit the DWARF-2 calling convention entry for a function.
21502 @item show sh calling-convention
21503 @kindex show sh calling-convention
21504 Show the current calling convention setting.
21509 @node Architectures
21510 @section Architectures
21512 This section describes characteristics of architectures that affect
21513 all uses of @value{GDBN} with the architecture, both native and cross.
21520 * HPPA:: HP PA architecture
21521 * SPU:: Cell Broadband Engine SPU architecture
21527 @subsection AArch64
21528 @cindex AArch64 support
21530 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21531 following special commands:
21534 @item set debug aarch64
21535 @kindex set debug aarch64
21536 This command determines whether AArch64 architecture-specific debugging
21537 messages are to be displayed.
21539 @item show debug aarch64
21540 Show whether AArch64 debugging messages are displayed.
21545 @subsection x86 Architecture-specific Issues
21548 @item set struct-convention @var{mode}
21549 @kindex set struct-convention
21550 @cindex struct return convention
21551 @cindex struct/union returned in registers
21552 Set the convention used by the inferior to return @code{struct}s and
21553 @code{union}s from functions to @var{mode}. Possible values of
21554 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21555 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21556 are returned on the stack, while @code{"reg"} means that a
21557 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21558 be returned in a register.
21560 @item show struct-convention
21561 @kindex show struct-convention
21562 Show the current setting of the convention to return @code{struct}s
21566 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21567 @cindex Intel(R) Memory Protection Extensions (MPX).
21569 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21570 @footnote{The register named with capital letters represent the architecture
21571 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21572 which are the lower bound and upper bound. Bounds are effective addresses or
21573 memory locations. The upper bounds are architecturally represented in 1's
21574 complement form. A bound having lower bound = 0, and upper bound = 0
21575 (1's complement of all bits set) will allow access to the entire address space.
21577 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21578 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21579 display the upper bound performing the complement of one operation on the
21580 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21581 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21582 can also be noted that the upper bounds are inclusive.
21584 As an example, assume that the register BND0 holds bounds for a pointer having
21585 access allowed for the range between 0x32 and 0x71. The values present on
21586 bnd0raw and bnd registers are presented as follows:
21589 bnd0raw = @{0x32, 0xffffffff8e@}
21590 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21593 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21594 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21595 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21596 Python, the display includes the memory size, in bits, accessible to
21602 See the following section.
21605 @subsection @acronym{MIPS}
21607 @cindex stack on Alpha
21608 @cindex stack on @acronym{MIPS}
21609 @cindex Alpha stack
21610 @cindex @acronym{MIPS} stack
21611 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21612 sometimes requires @value{GDBN} to search backward in the object code to
21613 find the beginning of a function.
21615 @cindex response time, @acronym{MIPS} debugging
21616 To improve response time (especially for embedded applications, where
21617 @value{GDBN} may be restricted to a slow serial line for this search)
21618 you may want to limit the size of this search, using one of these
21622 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21623 @item set heuristic-fence-post @var{limit}
21624 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21625 search for the beginning of a function. A value of @var{0} (the
21626 default) means there is no limit. However, except for @var{0}, the
21627 larger the limit the more bytes @code{heuristic-fence-post} must search
21628 and therefore the longer it takes to run. You should only need to use
21629 this command when debugging a stripped executable.
21631 @item show heuristic-fence-post
21632 Display the current limit.
21636 These commands are available @emph{only} when @value{GDBN} is configured
21637 for debugging programs on Alpha or @acronym{MIPS} processors.
21639 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21643 @item set mips abi @var{arg}
21644 @kindex set mips abi
21645 @cindex set ABI for @acronym{MIPS}
21646 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21647 values of @var{arg} are:
21651 The default ABI associated with the current binary (this is the
21661 @item show mips abi
21662 @kindex show mips abi
21663 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21665 @item set mips compression @var{arg}
21666 @kindex set mips compression
21667 @cindex code compression, @acronym{MIPS}
21668 Tell @value{GDBN} which @acronym{MIPS} compressed
21669 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21670 inferior. @value{GDBN} uses this for code disassembly and other
21671 internal interpretation purposes. This setting is only referred to
21672 when no executable has been associated with the debugging session or
21673 the executable does not provide information about the encoding it uses.
21674 Otherwise this setting is automatically updated from information
21675 provided by the executable.
21677 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21678 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21679 executables containing @acronym{MIPS16} code frequently are not
21680 identified as such.
21682 This setting is ``sticky''; that is, it retains its value across
21683 debugging sessions until reset either explicitly with this command or
21684 implicitly from an executable.
21686 The compiler and/or assembler typically add symbol table annotations to
21687 identify functions compiled for the @acronym{MIPS16} or
21688 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21689 are present, @value{GDBN} uses them in preference to the global
21690 compressed @acronym{ISA} encoding setting.
21692 @item show mips compression
21693 @kindex show mips compression
21694 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21695 @value{GDBN} to debug the inferior.
21698 @itemx show mipsfpu
21699 @xref{MIPS Embedded, set mipsfpu}.
21701 @item set mips mask-address @var{arg}
21702 @kindex set mips mask-address
21703 @cindex @acronym{MIPS} addresses, masking
21704 This command determines whether the most-significant 32 bits of 64-bit
21705 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21706 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21707 setting, which lets @value{GDBN} determine the correct value.
21709 @item show mips mask-address
21710 @kindex show mips mask-address
21711 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21714 @item set remote-mips64-transfers-32bit-regs
21715 @kindex set remote-mips64-transfers-32bit-regs
21716 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21717 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21718 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21719 and 64 bits for other registers, set this option to @samp{on}.
21721 @item show remote-mips64-transfers-32bit-regs
21722 @kindex show remote-mips64-transfers-32bit-regs
21723 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21725 @item set debug mips
21726 @kindex set debug mips
21727 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21728 target code in @value{GDBN}.
21730 @item show debug mips
21731 @kindex show debug mips
21732 Show the current setting of @acronym{MIPS} debugging messages.
21738 @cindex HPPA support
21740 When @value{GDBN} is debugging the HP PA architecture, it provides the
21741 following special commands:
21744 @item set debug hppa
21745 @kindex set debug hppa
21746 This command determines whether HPPA architecture-specific debugging
21747 messages are to be displayed.
21749 @item show debug hppa
21750 Show whether HPPA debugging messages are displayed.
21752 @item maint print unwind @var{address}
21753 @kindex maint print unwind@r{, HPPA}
21754 This command displays the contents of the unwind table entry at the
21755 given @var{address}.
21761 @subsection Cell Broadband Engine SPU architecture
21762 @cindex Cell Broadband Engine
21765 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21766 it provides the following special commands:
21769 @item info spu event
21771 Display SPU event facility status. Shows current event mask
21772 and pending event status.
21774 @item info spu signal
21775 Display SPU signal notification facility status. Shows pending
21776 signal-control word and signal notification mode of both signal
21777 notification channels.
21779 @item info spu mailbox
21780 Display SPU mailbox facility status. Shows all pending entries,
21781 in order of processing, in each of the SPU Write Outbound,
21782 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21785 Display MFC DMA status. Shows all pending commands in the MFC
21786 DMA queue. For each entry, opcode, tag, class IDs, effective
21787 and local store addresses and transfer size are shown.
21789 @item info spu proxydma
21790 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21791 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21792 and local store addresses and transfer size are shown.
21796 When @value{GDBN} is debugging a combined PowerPC/SPU application
21797 on the Cell Broadband Engine, it provides in addition the following
21801 @item set spu stop-on-load @var{arg}
21803 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21804 will give control to the user when a new SPE thread enters its @code{main}
21805 function. The default is @code{off}.
21807 @item show spu stop-on-load
21809 Show whether to stop for new SPE threads.
21811 @item set spu auto-flush-cache @var{arg}
21812 Set whether to automatically flush the software-managed cache. When set to
21813 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21814 cache to be flushed whenever SPE execution stops. This provides a consistent
21815 view of PowerPC memory that is accessed via the cache. If an application
21816 does not use the software-managed cache, this option has no effect.
21818 @item show spu auto-flush-cache
21819 Show whether to automatically flush the software-managed cache.
21824 @subsection PowerPC
21825 @cindex PowerPC architecture
21827 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21828 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21829 numbers stored in the floating point registers. These values must be stored
21830 in two consecutive registers, always starting at an even register like
21831 @code{f0} or @code{f2}.
21833 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21834 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21835 @code{f2} and @code{f3} for @code{$dl1} and so on.
21837 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21838 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21841 @subsection Nios II
21842 @cindex Nios II architecture
21844 When @value{GDBN} is debugging the Nios II architecture,
21845 it provides the following special commands:
21849 @item set debug nios2
21850 @kindex set debug nios2
21851 This command turns on and off debugging messages for the Nios II
21852 target code in @value{GDBN}.
21854 @item show debug nios2
21855 @kindex show debug nios2
21856 Show the current setting of Nios II debugging messages.
21859 @node Controlling GDB
21860 @chapter Controlling @value{GDBN}
21862 You can alter the way @value{GDBN} interacts with you by using the
21863 @code{set} command. For commands controlling how @value{GDBN} displays
21864 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21869 * Editing:: Command editing
21870 * Command History:: Command history
21871 * Screen Size:: Screen size
21872 * Numbers:: Numbers
21873 * ABI:: Configuring the current ABI
21874 * Auto-loading:: Automatically loading associated files
21875 * Messages/Warnings:: Optional warnings and messages
21876 * Debugging Output:: Optional messages about internal happenings
21877 * Other Misc Settings:: Other Miscellaneous Settings
21885 @value{GDBN} indicates its readiness to read a command by printing a string
21886 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21887 can change the prompt string with the @code{set prompt} command. For
21888 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21889 the prompt in one of the @value{GDBN} sessions so that you can always tell
21890 which one you are talking to.
21892 @emph{Note:} @code{set prompt} does not add a space for you after the
21893 prompt you set. This allows you to set a prompt which ends in a space
21894 or a prompt that does not.
21898 @item set prompt @var{newprompt}
21899 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21901 @kindex show prompt
21903 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21906 Versions of @value{GDBN} that ship with Python scripting enabled have
21907 prompt extensions. The commands for interacting with these extensions
21911 @kindex set extended-prompt
21912 @item set extended-prompt @var{prompt}
21913 Set an extended prompt that allows for substitutions.
21914 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21915 substitution. Any escape sequences specified as part of the prompt
21916 string are replaced with the corresponding strings each time the prompt
21922 set extended-prompt Current working directory: \w (gdb)
21925 Note that when an extended-prompt is set, it takes control of the
21926 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21928 @kindex show extended-prompt
21929 @item show extended-prompt
21930 Prints the extended prompt. Any escape sequences specified as part of
21931 the prompt string with @code{set extended-prompt}, are replaced with the
21932 corresponding strings each time the prompt is displayed.
21936 @section Command Editing
21938 @cindex command line editing
21940 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21941 @sc{gnu} library provides consistent behavior for programs which provide a
21942 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21943 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21944 substitution, and a storage and recall of command history across
21945 debugging sessions.
21947 You may control the behavior of command line editing in @value{GDBN} with the
21948 command @code{set}.
21951 @kindex set editing
21954 @itemx set editing on
21955 Enable command line editing (enabled by default).
21957 @item set editing off
21958 Disable command line editing.
21960 @kindex show editing
21962 Show whether command line editing is enabled.
21965 @ifset SYSTEM_READLINE
21966 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21968 @ifclear SYSTEM_READLINE
21969 @xref{Command Line Editing},
21971 for more details about the Readline
21972 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21973 encouraged to read that chapter.
21975 @node Command History
21976 @section Command History
21977 @cindex command history
21979 @value{GDBN} can keep track of the commands you type during your
21980 debugging sessions, so that you can be certain of precisely what
21981 happened. Use these commands to manage the @value{GDBN} command
21984 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21985 package, to provide the history facility.
21986 @ifset SYSTEM_READLINE
21987 @xref{Using History Interactively, , , history, GNU History Library},
21989 @ifclear SYSTEM_READLINE
21990 @xref{Using History Interactively},
21992 for the detailed description of the History library.
21994 To issue a command to @value{GDBN} without affecting certain aspects of
21995 the state which is seen by users, prefix it with @samp{server }
21996 (@pxref{Server Prefix}). This
21997 means that this command will not affect the command history, nor will it
21998 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21999 pressed on a line by itself.
22001 @cindex @code{server}, command prefix
22002 The server prefix does not affect the recording of values into the value
22003 history; to print a value without recording it into the value history,
22004 use the @code{output} command instead of the @code{print} command.
22006 Here is the description of @value{GDBN} commands related to command
22010 @cindex history substitution
22011 @cindex history file
22012 @kindex set history filename
22013 @cindex @env{GDBHISTFILE}, environment variable
22014 @item set history filename @var{fname}
22015 Set the name of the @value{GDBN} command history file to @var{fname}.
22016 This is the file where @value{GDBN} reads an initial command history
22017 list, and where it writes the command history from this session when it
22018 exits. You can access this list through history expansion or through
22019 the history command editing characters listed below. This file defaults
22020 to the value of the environment variable @code{GDBHISTFILE}, or to
22021 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22024 @cindex save command history
22025 @kindex set history save
22026 @item set history save
22027 @itemx set history save on
22028 Record command history in a file, whose name may be specified with the
22029 @code{set history filename} command. By default, this option is disabled.
22031 @item set history save off
22032 Stop recording command history in a file.
22034 @cindex history size
22035 @kindex set history size
22036 @cindex @env{HISTSIZE}, environment variable
22037 @item set history size @var{size}
22038 @itemx set history size unlimited
22039 Set the number of commands which @value{GDBN} keeps in its history list.
22040 This defaults to the value of the environment variable
22041 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22042 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22043 history list is unlimited.
22046 History expansion assigns special meaning to the character @kbd{!}.
22047 @ifset SYSTEM_READLINE
22048 @xref{Event Designators, , , history, GNU History Library},
22050 @ifclear SYSTEM_READLINE
22051 @xref{Event Designators},
22055 @cindex history expansion, turn on/off
22056 Since @kbd{!} is also the logical not operator in C, history expansion
22057 is off by default. If you decide to enable history expansion with the
22058 @code{set history expansion on} command, you may sometimes need to
22059 follow @kbd{!} (when it is used as logical not, in an expression) with
22060 a space or a tab to prevent it from being expanded. The readline
22061 history facilities do not attempt substitution on the strings
22062 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22064 The commands to control history expansion are:
22067 @item set history expansion on
22068 @itemx set history expansion
22069 @kindex set history expansion
22070 Enable history expansion. History expansion is off by default.
22072 @item set history expansion off
22073 Disable history expansion.
22076 @kindex show history
22078 @itemx show history filename
22079 @itemx show history save
22080 @itemx show history size
22081 @itemx show history expansion
22082 These commands display the state of the @value{GDBN} history parameters.
22083 @code{show history} by itself displays all four states.
22088 @kindex show commands
22089 @cindex show last commands
22090 @cindex display command history
22091 @item show commands
22092 Display the last ten commands in the command history.
22094 @item show commands @var{n}
22095 Print ten commands centered on command number @var{n}.
22097 @item show commands +
22098 Print ten commands just after the commands last printed.
22102 @section Screen Size
22103 @cindex size of screen
22104 @cindex pauses in output
22106 Certain commands to @value{GDBN} may produce large amounts of
22107 information output to the screen. To help you read all of it,
22108 @value{GDBN} pauses and asks you for input at the end of each page of
22109 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22110 to discard the remaining output. Also, the screen width setting
22111 determines when to wrap lines of output. Depending on what is being
22112 printed, @value{GDBN} tries to break the line at a readable place,
22113 rather than simply letting it overflow onto the following line.
22115 Normally @value{GDBN} knows the size of the screen from the terminal
22116 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22117 together with the value of the @code{TERM} environment variable and the
22118 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22119 you can override it with the @code{set height} and @code{set
22126 @kindex show height
22127 @item set height @var{lpp}
22128 @itemx set height unlimited
22130 @itemx set width @var{cpl}
22131 @itemx set width unlimited
22133 These @code{set} commands specify a screen height of @var{lpp} lines and
22134 a screen width of @var{cpl} characters. The associated @code{show}
22135 commands display the current settings.
22137 If you specify a height of either @code{unlimited} or zero lines,
22138 @value{GDBN} does not pause during output no matter how long the
22139 output is. This is useful if output is to a file or to an editor
22142 Likewise, you can specify @samp{set width unlimited} or @samp{set
22143 width 0} to prevent @value{GDBN} from wrapping its output.
22145 @item set pagination on
22146 @itemx set pagination off
22147 @kindex set pagination
22148 Turn the output pagination on or off; the default is on. Turning
22149 pagination off is the alternative to @code{set height unlimited}. Note that
22150 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22151 Options, -batch}) also automatically disables pagination.
22153 @item show pagination
22154 @kindex show pagination
22155 Show the current pagination mode.
22160 @cindex number representation
22161 @cindex entering numbers
22163 You can always enter numbers in octal, decimal, or hexadecimal in
22164 @value{GDBN} by the usual conventions: octal numbers begin with
22165 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22166 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22167 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22168 10; likewise, the default display for numbers---when no particular
22169 format is specified---is base 10. You can change the default base for
22170 both input and output with the commands described below.
22173 @kindex set input-radix
22174 @item set input-radix @var{base}
22175 Set the default base for numeric input. Supported choices
22176 for @var{base} are decimal 8, 10, or 16. The base must itself be
22177 specified either unambiguously or using the current input radix; for
22181 set input-radix 012
22182 set input-radix 10.
22183 set input-radix 0xa
22187 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22188 leaves the input radix unchanged, no matter what it was, since
22189 @samp{10}, being without any leading or trailing signs of its base, is
22190 interpreted in the current radix. Thus, if the current radix is 16,
22191 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22194 @kindex set output-radix
22195 @item set output-radix @var{base}
22196 Set the default base for numeric display. Supported choices
22197 for @var{base} are decimal 8, 10, or 16. The base must itself be
22198 specified either unambiguously or using the current input radix.
22200 @kindex show input-radix
22201 @item show input-radix
22202 Display the current default base for numeric input.
22204 @kindex show output-radix
22205 @item show output-radix
22206 Display the current default base for numeric display.
22208 @item set radix @r{[}@var{base}@r{]}
22212 These commands set and show the default base for both input and output
22213 of numbers. @code{set radix} sets the radix of input and output to
22214 the same base; without an argument, it resets the radix back to its
22215 default value of 10.
22220 @section Configuring the Current ABI
22222 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22223 application automatically. However, sometimes you need to override its
22224 conclusions. Use these commands to manage @value{GDBN}'s view of the
22230 @cindex Newlib OS ABI and its influence on the longjmp handling
22232 One @value{GDBN} configuration can debug binaries for multiple operating
22233 system targets, either via remote debugging or native emulation.
22234 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22235 but you can override its conclusion using the @code{set osabi} command.
22236 One example where this is useful is in debugging of binaries which use
22237 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22238 not have the same identifying marks that the standard C library for your
22241 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22242 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22243 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22244 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22248 Show the OS ABI currently in use.
22251 With no argument, show the list of registered available OS ABI's.
22253 @item set osabi @var{abi}
22254 Set the current OS ABI to @var{abi}.
22257 @cindex float promotion
22259 Generally, the way that an argument of type @code{float} is passed to a
22260 function depends on whether the function is prototyped. For a prototyped
22261 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22262 according to the architecture's convention for @code{float}. For unprototyped
22263 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22264 @code{double} and then passed.
22266 Unfortunately, some forms of debug information do not reliably indicate whether
22267 a function is prototyped. If @value{GDBN} calls a function that is not marked
22268 as prototyped, it consults @kbd{set coerce-float-to-double}.
22271 @kindex set coerce-float-to-double
22272 @item set coerce-float-to-double
22273 @itemx set coerce-float-to-double on
22274 Arguments of type @code{float} will be promoted to @code{double} when passed
22275 to an unprototyped function. This is the default setting.
22277 @item set coerce-float-to-double off
22278 Arguments of type @code{float} will be passed directly to unprototyped
22281 @kindex show coerce-float-to-double
22282 @item show coerce-float-to-double
22283 Show the current setting of promoting @code{float} to @code{double}.
22287 @kindex show cp-abi
22288 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22289 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22290 used to build your application. @value{GDBN} only fully supports
22291 programs with a single C@t{++} ABI; if your program contains code using
22292 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22293 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22294 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22295 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22296 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22297 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22302 Show the C@t{++} ABI currently in use.
22305 With no argument, show the list of supported C@t{++} ABI's.
22307 @item set cp-abi @var{abi}
22308 @itemx set cp-abi auto
22309 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22313 @section Automatically loading associated files
22314 @cindex auto-loading
22316 @value{GDBN} sometimes reads files with commands and settings automatically,
22317 without being explicitly told so by the user. We call this feature
22318 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22319 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22320 results or introduce security risks (e.g., if the file comes from untrusted
22324 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22325 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22327 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22328 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22331 There are various kinds of files @value{GDBN} can automatically load.
22332 In addition to these files, @value{GDBN} supports auto-loading code written
22333 in various extension languages. @xref{Auto-loading extensions}.
22335 Note that loading of these associated files (including the local @file{.gdbinit}
22336 file) requires accordingly configured @code{auto-load safe-path}
22337 (@pxref{Auto-loading safe path}).
22339 For these reasons, @value{GDBN} includes commands and options to let you
22340 control when to auto-load files and which files should be auto-loaded.
22343 @anchor{set auto-load off}
22344 @kindex set auto-load off
22345 @item set auto-load off
22346 Globally disable loading of all auto-loaded files.
22347 You may want to use this command with the @samp{-iex} option
22348 (@pxref{Option -init-eval-command}) such as:
22350 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22353 Be aware that system init file (@pxref{System-wide configuration})
22354 and init files from your home directory (@pxref{Home Directory Init File})
22355 still get read (as they come from generally trusted directories).
22356 To prevent @value{GDBN} from auto-loading even those init files, use the
22357 @option{-nx} option (@pxref{Mode Options}), in addition to
22358 @code{set auto-load no}.
22360 @anchor{show auto-load}
22361 @kindex show auto-load
22362 @item show auto-load
22363 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22367 (gdb) show auto-load
22368 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22369 libthread-db: Auto-loading of inferior specific libthread_db is on.
22370 local-gdbinit: Auto-loading of .gdbinit script from current directory
22372 python-scripts: Auto-loading of Python scripts is on.
22373 safe-path: List of directories from which it is safe to auto-load files
22374 is $debugdir:$datadir/auto-load.
22375 scripts-directory: List of directories from which to load auto-loaded scripts
22376 is $debugdir:$datadir/auto-load.
22379 @anchor{info auto-load}
22380 @kindex info auto-load
22381 @item info auto-load
22382 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22386 (gdb) info auto-load
22389 Yes /home/user/gdb/gdb-gdb.gdb
22390 libthread-db: No auto-loaded libthread-db.
22391 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22395 Yes /home/user/gdb/gdb-gdb.py
22399 These are @value{GDBN} control commands for the auto-loading:
22401 @multitable @columnfractions .5 .5
22402 @item @xref{set auto-load off}.
22403 @tab Disable auto-loading globally.
22404 @item @xref{show auto-load}.
22405 @tab Show setting of all kinds of files.
22406 @item @xref{info auto-load}.
22407 @tab Show state of all kinds of files.
22408 @item @xref{set auto-load gdb-scripts}.
22409 @tab Control for @value{GDBN} command scripts.
22410 @item @xref{show auto-load gdb-scripts}.
22411 @tab Show setting of @value{GDBN} command scripts.
22412 @item @xref{info auto-load gdb-scripts}.
22413 @tab Show state of @value{GDBN} command scripts.
22414 @item @xref{set auto-load python-scripts}.
22415 @tab Control for @value{GDBN} Python scripts.
22416 @item @xref{show auto-load python-scripts}.
22417 @tab Show setting of @value{GDBN} Python scripts.
22418 @item @xref{info auto-load python-scripts}.
22419 @tab Show state of @value{GDBN} Python scripts.
22420 @item @xref{set auto-load guile-scripts}.
22421 @tab Control for @value{GDBN} Guile scripts.
22422 @item @xref{show auto-load guile-scripts}.
22423 @tab Show setting of @value{GDBN} Guile scripts.
22424 @item @xref{info auto-load guile-scripts}.
22425 @tab Show state of @value{GDBN} Guile scripts.
22426 @item @xref{set auto-load scripts-directory}.
22427 @tab Control for @value{GDBN} auto-loaded scripts location.
22428 @item @xref{show auto-load scripts-directory}.
22429 @tab Show @value{GDBN} auto-loaded scripts location.
22430 @item @xref{set auto-load local-gdbinit}.
22431 @tab Control for init file in the current directory.
22432 @item @xref{show auto-load local-gdbinit}.
22433 @tab Show setting of init file in the current directory.
22434 @item @xref{info auto-load local-gdbinit}.
22435 @tab Show state of init file in the current directory.
22436 @item @xref{set auto-load libthread-db}.
22437 @tab Control for thread debugging library.
22438 @item @xref{show auto-load libthread-db}.
22439 @tab Show setting of thread debugging library.
22440 @item @xref{info auto-load libthread-db}.
22441 @tab Show state of thread debugging library.
22442 @item @xref{set auto-load safe-path}.
22443 @tab Control directories trusted for automatic loading.
22444 @item @xref{show auto-load safe-path}.
22445 @tab Show directories trusted for automatic loading.
22446 @item @xref{add-auto-load-safe-path}.
22447 @tab Add directory trusted for automatic loading.
22450 @node Init File in the Current Directory
22451 @subsection Automatically loading init file in the current directory
22452 @cindex auto-loading init file in the current directory
22454 By default, @value{GDBN} reads and executes the canned sequences of commands
22455 from init file (if any) in the current working directory,
22456 see @ref{Init File in the Current Directory during Startup}.
22458 Note that loading of this local @file{.gdbinit} file also requires accordingly
22459 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22462 @anchor{set auto-load local-gdbinit}
22463 @kindex set auto-load local-gdbinit
22464 @item set auto-load local-gdbinit [on|off]
22465 Enable or disable the auto-loading of canned sequences of commands
22466 (@pxref{Sequences}) found in init file in the current directory.
22468 @anchor{show auto-load local-gdbinit}
22469 @kindex show auto-load local-gdbinit
22470 @item show auto-load local-gdbinit
22471 Show whether auto-loading of canned sequences of commands from init file in the
22472 current directory is enabled or disabled.
22474 @anchor{info auto-load local-gdbinit}
22475 @kindex info auto-load local-gdbinit
22476 @item info auto-load local-gdbinit
22477 Print whether canned sequences of commands from init file in the
22478 current directory have been auto-loaded.
22481 @node libthread_db.so.1 file
22482 @subsection Automatically loading thread debugging library
22483 @cindex auto-loading libthread_db.so.1
22485 This feature is currently present only on @sc{gnu}/Linux native hosts.
22487 @value{GDBN} reads in some cases thread debugging library from places specific
22488 to the inferior (@pxref{set libthread-db-search-path}).
22490 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22491 without checking this @samp{set auto-load libthread-db} switch as system
22492 libraries have to be trusted in general. In all other cases of
22493 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22494 auto-load libthread-db} is enabled before trying to open such thread debugging
22497 Note that loading of this debugging library also requires accordingly configured
22498 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22501 @anchor{set auto-load libthread-db}
22502 @kindex set auto-load libthread-db
22503 @item set auto-load libthread-db [on|off]
22504 Enable or disable the auto-loading of inferior specific thread debugging library.
22506 @anchor{show auto-load libthread-db}
22507 @kindex show auto-load libthread-db
22508 @item show auto-load libthread-db
22509 Show whether auto-loading of inferior specific thread debugging library is
22510 enabled or disabled.
22512 @anchor{info auto-load libthread-db}
22513 @kindex info auto-load libthread-db
22514 @item info auto-load libthread-db
22515 Print the list of all loaded inferior specific thread debugging libraries and
22516 for each such library print list of inferior @var{pid}s using it.
22519 @node Auto-loading safe path
22520 @subsection Security restriction for auto-loading
22521 @cindex auto-loading safe-path
22523 As the files of inferior can come from untrusted source (such as submitted by
22524 an application user) @value{GDBN} does not always load any files automatically.
22525 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22526 directories trusted for loading files not explicitly requested by user.
22527 Each directory can also be a shell wildcard pattern.
22529 If the path is not set properly you will see a warning and the file will not
22534 Reading symbols from /home/user/gdb/gdb...done.
22535 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22536 declined by your `auto-load safe-path' set
22537 to "$debugdir:$datadir/auto-load".
22538 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22539 declined by your `auto-load safe-path' set
22540 to "$debugdir:$datadir/auto-load".
22544 To instruct @value{GDBN} to go ahead and use the init files anyway,
22545 invoke @value{GDBN} like this:
22548 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22551 The list of trusted directories is controlled by the following commands:
22554 @anchor{set auto-load safe-path}
22555 @kindex set auto-load safe-path
22556 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22557 Set the list of directories (and their subdirectories) trusted for automatic
22558 loading and execution of scripts. You can also enter a specific trusted file.
22559 Each directory can also be a shell wildcard pattern; wildcards do not match
22560 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22561 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22562 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22563 its default value as specified during @value{GDBN} compilation.
22565 The list of directories uses path separator (@samp{:} on GNU and Unix
22566 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22567 to the @env{PATH} environment variable.
22569 @anchor{show auto-load safe-path}
22570 @kindex show auto-load safe-path
22571 @item show auto-load safe-path
22572 Show the list of directories trusted for automatic loading and execution of
22575 @anchor{add-auto-load-safe-path}
22576 @kindex add-auto-load-safe-path
22577 @item add-auto-load-safe-path
22578 Add an entry (or list of entries) the list of directories trusted for automatic
22579 loading and execution of scripts. Multiple entries may be delimited by the
22580 host platform path separator in use.
22583 This variable defaults to what @code{--with-auto-load-dir} has been configured
22584 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22585 substitution applies the same as for @ref{set auto-load scripts-directory}.
22586 The default @code{set auto-load safe-path} value can be also overriden by
22587 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22589 Setting this variable to @file{/} disables this security protection,
22590 corresponding @value{GDBN} configuration option is
22591 @option{--without-auto-load-safe-path}.
22592 This variable is supposed to be set to the system directories writable by the
22593 system superuser only. Users can add their source directories in init files in
22594 their home directories (@pxref{Home Directory Init File}). See also deprecated
22595 init file in the current directory
22596 (@pxref{Init File in the Current Directory during Startup}).
22598 To force @value{GDBN} to load the files it declined to load in the previous
22599 example, you could use one of the following ways:
22602 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22603 Specify this trusted directory (or a file) as additional component of the list.
22604 You have to specify also any existing directories displayed by
22605 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22607 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22608 Specify this directory as in the previous case but just for a single
22609 @value{GDBN} session.
22611 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22612 Disable auto-loading safety for a single @value{GDBN} session.
22613 This assumes all the files you debug during this @value{GDBN} session will come
22614 from trusted sources.
22616 @item @kbd{./configure --without-auto-load-safe-path}
22617 During compilation of @value{GDBN} you may disable any auto-loading safety.
22618 This assumes all the files you will ever debug with this @value{GDBN} come from
22622 On the other hand you can also explicitly forbid automatic files loading which
22623 also suppresses any such warning messages:
22626 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22627 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22629 @item @file{~/.gdbinit}: @samp{set auto-load no}
22630 Disable auto-loading globally for the user
22631 (@pxref{Home Directory Init File}). While it is improbable, you could also
22632 use system init file instead (@pxref{System-wide configuration}).
22635 This setting applies to the file names as entered by user. If no entry matches
22636 @value{GDBN} tries as a last resort to also resolve all the file names into
22637 their canonical form (typically resolving symbolic links) and compare the
22638 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22639 own before starting the comparison so a canonical form of directories is
22640 recommended to be entered.
22642 @node Auto-loading verbose mode
22643 @subsection Displaying files tried for auto-load
22644 @cindex auto-loading verbose mode
22646 For better visibility of all the file locations where you can place scripts to
22647 be auto-loaded with inferior --- or to protect yourself against accidental
22648 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22649 all the files attempted to be loaded. Both existing and non-existing files may
22652 For example the list of directories from which it is safe to auto-load files
22653 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22654 may not be too obvious while setting it up.
22657 (gdb) set debug auto-load on
22658 (gdb) file ~/src/t/true
22659 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22660 for objfile "/tmp/true".
22661 auto-load: Updating directories of "/usr:/opt".
22662 auto-load: Using directory "/usr".
22663 auto-load: Using directory "/opt".
22664 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22665 by your `auto-load safe-path' set to "/usr:/opt".
22669 @anchor{set debug auto-load}
22670 @kindex set debug auto-load
22671 @item set debug auto-load [on|off]
22672 Set whether to print the filenames attempted to be auto-loaded.
22674 @anchor{show debug auto-load}
22675 @kindex show debug auto-load
22676 @item show debug auto-load
22677 Show whether printing of the filenames attempted to be auto-loaded is turned
22681 @node Messages/Warnings
22682 @section Optional Warnings and Messages
22684 @cindex verbose operation
22685 @cindex optional warnings
22686 By default, @value{GDBN} is silent about its inner workings. If you are
22687 running on a slow machine, you may want to use the @code{set verbose}
22688 command. This makes @value{GDBN} tell you when it does a lengthy
22689 internal operation, so you will not think it has crashed.
22691 Currently, the messages controlled by @code{set verbose} are those
22692 which announce that the symbol table for a source file is being read;
22693 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22696 @kindex set verbose
22697 @item set verbose on
22698 Enables @value{GDBN} output of certain informational messages.
22700 @item set verbose off
22701 Disables @value{GDBN} output of certain informational messages.
22703 @kindex show verbose
22705 Displays whether @code{set verbose} is on or off.
22708 By default, if @value{GDBN} encounters bugs in the symbol table of an
22709 object file, it is silent; but if you are debugging a compiler, you may
22710 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22715 @kindex set complaints
22716 @item set complaints @var{limit}
22717 Permits @value{GDBN} to output @var{limit} complaints about each type of
22718 unusual symbols before becoming silent about the problem. Set
22719 @var{limit} to zero to suppress all complaints; set it to a large number
22720 to prevent complaints from being suppressed.
22722 @kindex show complaints
22723 @item show complaints
22724 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22728 @anchor{confirmation requests}
22729 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22730 lot of stupid questions to confirm certain commands. For example, if
22731 you try to run a program which is already running:
22735 The program being debugged has been started already.
22736 Start it from the beginning? (y or n)
22739 If you are willing to unflinchingly face the consequences of your own
22740 commands, you can disable this ``feature'':
22744 @kindex set confirm
22746 @cindex confirmation
22747 @cindex stupid questions
22748 @item set confirm off
22749 Disables confirmation requests. Note that running @value{GDBN} with
22750 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22751 automatically disables confirmation requests.
22753 @item set confirm on
22754 Enables confirmation requests (the default).
22756 @kindex show confirm
22758 Displays state of confirmation requests.
22762 @cindex command tracing
22763 If you need to debug user-defined commands or sourced files you may find it
22764 useful to enable @dfn{command tracing}. In this mode each command will be
22765 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22766 quantity denoting the call depth of each command.
22769 @kindex set trace-commands
22770 @cindex command scripts, debugging
22771 @item set trace-commands on
22772 Enable command tracing.
22773 @item set trace-commands off
22774 Disable command tracing.
22775 @item show trace-commands
22776 Display the current state of command tracing.
22779 @node Debugging Output
22780 @section Optional Messages about Internal Happenings
22781 @cindex optional debugging messages
22783 @value{GDBN} has commands that enable optional debugging messages from
22784 various @value{GDBN} subsystems; normally these commands are of
22785 interest to @value{GDBN} maintainers, or when reporting a bug. This
22786 section documents those commands.
22789 @kindex set exec-done-display
22790 @item set exec-done-display
22791 Turns on or off the notification of asynchronous commands'
22792 completion. When on, @value{GDBN} will print a message when an
22793 asynchronous command finishes its execution. The default is off.
22794 @kindex show exec-done-display
22795 @item show exec-done-display
22796 Displays the current setting of asynchronous command completion
22799 @cindex ARM AArch64
22800 @item set debug aarch64
22801 Turns on or off display of debugging messages related to ARM AArch64.
22802 The default is off.
22804 @item show debug aarch64
22805 Displays the current state of displaying debugging messages related to
22807 @cindex gdbarch debugging info
22808 @cindex architecture debugging info
22809 @item set debug arch
22810 Turns on or off display of gdbarch debugging info. The default is off
22811 @item show debug arch
22812 Displays the current state of displaying gdbarch debugging info.
22813 @item set debug aix-solib
22814 @cindex AIX shared library debugging
22815 Control display of debugging messages from the AIX shared library
22816 support module. The default is off.
22817 @item show debug aix-thread
22818 Show the current state of displaying AIX shared library debugging messages.
22819 @item set debug aix-thread
22820 @cindex AIX threads
22821 Display debugging messages about inner workings of the AIX thread
22823 @item show debug aix-thread
22824 Show the current state of AIX thread debugging info display.
22825 @item set debug check-physname
22827 Check the results of the ``physname'' computation. When reading DWARF
22828 debugging information for C@t{++}, @value{GDBN} attempts to compute
22829 each entity's name. @value{GDBN} can do this computation in two
22830 different ways, depending on exactly what information is present.
22831 When enabled, this setting causes @value{GDBN} to compute the names
22832 both ways and display any discrepancies.
22833 @item show debug check-physname
22834 Show the current state of ``physname'' checking.
22835 @item set debug coff-pe-read
22836 @cindex COFF/PE exported symbols
22837 Control display of debugging messages related to reading of COFF/PE
22838 exported symbols. The default is off.
22839 @item show debug coff-pe-read
22840 Displays the current state of displaying debugging messages related to
22841 reading of COFF/PE exported symbols.
22842 @item set debug dwarf2-die
22843 @cindex DWARF2 DIEs
22844 Dump DWARF2 DIEs after they are read in.
22845 The value is the number of nesting levels to print.
22846 A value of zero turns off the display.
22847 @item show debug dwarf2-die
22848 Show the current state of DWARF2 DIE debugging.
22849 @item set debug dwarf2-read
22850 @cindex DWARF2 Reading
22851 Turns on or off display of debugging messages related to reading
22852 DWARF debug info. The default is 0 (off).
22853 A value of 1 provides basic information.
22854 A value greater than 1 provides more verbose information.
22855 @item show debug dwarf2-read
22856 Show the current state of DWARF2 reader debugging.
22857 @item set debug displaced
22858 @cindex displaced stepping debugging info
22859 Turns on or off display of @value{GDBN} debugging info for the
22860 displaced stepping support. The default is off.
22861 @item show debug displaced
22862 Displays the current state of displaying @value{GDBN} debugging info
22863 related to displaced stepping.
22864 @item set debug event
22865 @cindex event debugging info
22866 Turns on or off display of @value{GDBN} event debugging info. The
22868 @item show debug event
22869 Displays the current state of displaying @value{GDBN} event debugging
22871 @item set debug expression
22872 @cindex expression debugging info
22873 Turns on or off display of debugging info about @value{GDBN}
22874 expression parsing. The default is off.
22875 @item show debug expression
22876 Displays the current state of displaying debugging info about
22877 @value{GDBN} expression parsing.
22878 @item set debug frame
22879 @cindex frame debugging info
22880 Turns on or off display of @value{GDBN} frame debugging info. The
22882 @item show debug frame
22883 Displays the current state of displaying @value{GDBN} frame debugging
22885 @item set debug gnu-nat
22886 @cindex @sc{gnu}/Hurd debug messages
22887 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22888 @item show debug gnu-nat
22889 Show the current state of @sc{gnu}/Hurd debugging messages.
22890 @item set debug infrun
22891 @cindex inferior debugging info
22892 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22893 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22894 for implementing operations such as single-stepping the inferior.
22895 @item show debug infrun
22896 Displays the current state of @value{GDBN} inferior debugging.
22897 @item set debug jit
22898 @cindex just-in-time compilation, debugging messages
22899 Turns on or off debugging messages from JIT debug support.
22900 @item show debug jit
22901 Displays the current state of @value{GDBN} JIT debugging.
22902 @item set debug lin-lwp
22903 @cindex @sc{gnu}/Linux LWP debug messages
22904 @cindex Linux lightweight processes
22905 Turns on or off debugging messages from the Linux LWP debug support.
22906 @item show debug lin-lwp
22907 Show the current state of Linux LWP debugging messages.
22908 @item set debug mach-o
22909 @cindex Mach-O symbols processing
22910 Control display of debugging messages related to Mach-O symbols
22911 processing. The default is off.
22912 @item show debug mach-o
22913 Displays the current state of displaying debugging messages related to
22914 reading of COFF/PE exported symbols.
22915 @item set debug notification
22916 @cindex remote async notification debugging info
22917 Turns on or off debugging messages about remote async notification.
22918 The default is off.
22919 @item show debug notification
22920 Displays the current state of remote async notification debugging messages.
22921 @item set debug observer
22922 @cindex observer debugging info
22923 Turns on or off display of @value{GDBN} observer debugging. This
22924 includes info such as the notification of observable events.
22925 @item show debug observer
22926 Displays the current state of observer debugging.
22927 @item set debug overload
22928 @cindex C@t{++} overload debugging info
22929 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22930 info. This includes info such as ranking of functions, etc. The default
22932 @item show debug overload
22933 Displays the current state of displaying @value{GDBN} C@t{++} overload
22935 @cindex expression parser, debugging info
22936 @cindex debug expression parser
22937 @item set debug parser
22938 Turns on or off the display of expression parser debugging output.
22939 Internally, this sets the @code{yydebug} variable in the expression
22940 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22941 details. The default is off.
22942 @item show debug parser
22943 Show the current state of expression parser debugging.
22944 @cindex packets, reporting on stdout
22945 @cindex serial connections, debugging
22946 @cindex debug remote protocol
22947 @cindex remote protocol debugging
22948 @cindex display remote packets
22949 @item set debug remote
22950 Turns on or off display of reports on all packets sent back and forth across
22951 the serial line to the remote machine. The info is printed on the
22952 @value{GDBN} standard output stream. The default is off.
22953 @item show debug remote
22954 Displays the state of display of remote packets.
22955 @item set debug serial
22956 Turns on or off display of @value{GDBN} serial debugging info. The
22958 @item show debug serial
22959 Displays the current state of displaying @value{GDBN} serial debugging
22961 @item set debug solib-frv
22962 @cindex FR-V shared-library debugging
22963 Turns on or off debugging messages for FR-V shared-library code.
22964 @item show debug solib-frv
22965 Display the current state of FR-V shared-library code debugging
22967 @item set debug symfile
22968 @cindex symbol file functions
22969 Turns on or off display of debugging messages related to symbol file functions.
22970 The default is off. @xref{Files}.
22971 @item show debug symfile
22972 Show the current state of symbol file debugging messages.
22973 @item set debug symtab-create
22974 @cindex symbol table creation
22975 Turns on or off display of debugging messages related to symbol table creation.
22976 The default is 0 (off).
22977 A value of 1 provides basic information.
22978 A value greater than 1 provides more verbose information.
22979 @item show debug symtab-create
22980 Show the current state of symbol table creation debugging.
22981 @item set debug target
22982 @cindex target debugging info
22983 Turns on or off display of @value{GDBN} target debugging info. This info
22984 includes what is going on at the target level of GDB, as it happens. The
22985 default is 0. Set it to 1 to track events, and to 2 to also track the
22986 value of large memory transfers. Changes to this flag do not take effect
22987 until the next time you connect to a target or use the @code{run} command.
22988 @item show debug target
22989 Displays the current state of displaying @value{GDBN} target debugging
22991 @item set debug timestamp
22992 @cindex timestampping debugging info
22993 Turns on or off display of timestamps with @value{GDBN} debugging info.
22994 When enabled, seconds and microseconds are displayed before each debugging
22996 @item show debug timestamp
22997 Displays the current state of displaying timestamps with @value{GDBN}
22999 @item set debug varobj
23000 @cindex variable object debugging info
23001 Turns on or off display of @value{GDBN} variable object debugging
23002 info. The default is off.
23003 @item show debug varobj
23004 Displays the current state of displaying @value{GDBN} variable object
23006 @item set debug xml
23007 @cindex XML parser debugging
23008 Turns on or off debugging messages for built-in XML parsers.
23009 @item show debug xml
23010 Displays the current state of XML debugging messages.
23013 @node Other Misc Settings
23014 @section Other Miscellaneous Settings
23015 @cindex miscellaneous settings
23018 @kindex set interactive-mode
23019 @item set interactive-mode
23020 If @code{on}, forces @value{GDBN} to assume that GDB was started
23021 in a terminal. In practice, this means that @value{GDBN} should wait
23022 for the user to answer queries generated by commands entered at
23023 the command prompt. If @code{off}, forces @value{GDBN} to operate
23024 in the opposite mode, and it uses the default answers to all queries.
23025 If @code{auto} (the default), @value{GDBN} tries to determine whether
23026 its standard input is a terminal, and works in interactive-mode if it
23027 is, non-interactively otherwise.
23029 In the vast majority of cases, the debugger should be able to guess
23030 correctly which mode should be used. But this setting can be useful
23031 in certain specific cases, such as running a MinGW @value{GDBN}
23032 inside a cygwin window.
23034 @kindex show interactive-mode
23035 @item show interactive-mode
23036 Displays whether the debugger is operating in interactive mode or not.
23039 @node Extending GDB
23040 @chapter Extending @value{GDBN}
23041 @cindex extending GDB
23043 @value{GDBN} provides several mechanisms for extension.
23044 @value{GDBN} also provides the ability to automatically load
23045 extensions when it reads a file for debugging. This allows the
23046 user to automatically customize @value{GDBN} for the program
23050 * Sequences:: Canned Sequences of @value{GDBN} Commands
23051 * Python:: Extending @value{GDBN} using Python
23052 * Guile:: Extending @value{GDBN} using Guile
23053 * Auto-loading extensions:: Automatically loading extensions
23054 * Multiple Extension Languages:: Working with multiple extension languages
23055 * Aliases:: Creating new spellings of existing commands
23058 To facilitate the use of extension languages, @value{GDBN} is capable
23059 of evaluating the contents of a file. When doing so, @value{GDBN}
23060 can recognize which extension language is being used by looking at
23061 the filename extension. Files with an unrecognized filename extension
23062 are always treated as a @value{GDBN} Command Files.
23063 @xref{Command Files,, Command files}.
23065 You can control how @value{GDBN} evaluates these files with the following
23069 @kindex set script-extension
23070 @kindex show script-extension
23071 @item set script-extension off
23072 All scripts are always evaluated as @value{GDBN} Command Files.
23074 @item set script-extension soft
23075 The debugger determines the scripting language based on filename
23076 extension. If this scripting language is supported, @value{GDBN}
23077 evaluates the script using that language. Otherwise, it evaluates
23078 the file as a @value{GDBN} Command File.
23080 @item set script-extension strict
23081 The debugger determines the scripting language based on filename
23082 extension, and evaluates the script using that language. If the
23083 language is not supported, then the evaluation fails.
23085 @item show script-extension
23086 Display the current value of the @code{script-extension} option.
23091 @section Canned Sequences of Commands
23093 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23094 Command Lists}), @value{GDBN} provides two ways to store sequences of
23095 commands for execution as a unit: user-defined commands and command
23099 * Define:: How to define your own commands
23100 * Hooks:: Hooks for user-defined commands
23101 * Command Files:: How to write scripts of commands to be stored in a file
23102 * Output:: Commands for controlled output
23103 * Auto-loading sequences:: Controlling auto-loaded command files
23107 @subsection User-defined Commands
23109 @cindex user-defined command
23110 @cindex arguments, to user-defined commands
23111 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23112 which you assign a new name as a command. This is done with the
23113 @code{define} command. User commands may accept up to 10 arguments
23114 separated by whitespace. Arguments are accessed within the user command
23115 via @code{$arg0@dots{}$arg9}. A trivial example:
23119 print $arg0 + $arg1 + $arg2
23124 To execute the command use:
23131 This defines the command @code{adder}, which prints the sum of
23132 its three arguments. Note the arguments are text substitutions, so they may
23133 reference variables, use complex expressions, or even perform inferior
23136 @cindex argument count in user-defined commands
23137 @cindex how many arguments (user-defined commands)
23138 In addition, @code{$argc} may be used to find out how many arguments have
23139 been passed. This expands to a number in the range 0@dots{}10.
23144 print $arg0 + $arg1
23147 print $arg0 + $arg1 + $arg2
23155 @item define @var{commandname}
23156 Define a command named @var{commandname}. If there is already a command
23157 by that name, you are asked to confirm that you want to redefine it.
23158 The argument @var{commandname} may be a bare command name consisting of letters,
23159 numbers, dashes, and underscores. It may also start with any predefined
23160 prefix command. For example, @samp{define target my-target} creates
23161 a user-defined @samp{target my-target} command.
23163 The definition of the command is made up of other @value{GDBN} command lines,
23164 which are given following the @code{define} command. The end of these
23165 commands is marked by a line containing @code{end}.
23168 @kindex end@r{ (user-defined commands)}
23169 @item document @var{commandname}
23170 Document the user-defined command @var{commandname}, so that it can be
23171 accessed by @code{help}. The command @var{commandname} must already be
23172 defined. This command reads lines of documentation just as @code{define}
23173 reads the lines of the command definition, ending with @code{end}.
23174 After the @code{document} command is finished, @code{help} on command
23175 @var{commandname} displays the documentation you have written.
23177 You may use the @code{document} command again to change the
23178 documentation of a command. Redefining the command with @code{define}
23179 does not change the documentation.
23181 @kindex dont-repeat
23182 @cindex don't repeat command
23184 Used inside a user-defined command, this tells @value{GDBN} that this
23185 command should not be repeated when the user hits @key{RET}
23186 (@pxref{Command Syntax, repeat last command}).
23188 @kindex help user-defined
23189 @item help user-defined
23190 List all user-defined commands and all python commands defined in class
23191 COMAND_USER. The first line of the documentation or docstring is
23196 @itemx show user @var{commandname}
23197 Display the @value{GDBN} commands used to define @var{commandname} (but
23198 not its documentation). If no @var{commandname} is given, display the
23199 definitions for all user-defined commands.
23200 This does not work for user-defined python commands.
23202 @cindex infinite recursion in user-defined commands
23203 @kindex show max-user-call-depth
23204 @kindex set max-user-call-depth
23205 @item show max-user-call-depth
23206 @itemx set max-user-call-depth
23207 The value of @code{max-user-call-depth} controls how many recursion
23208 levels are allowed in user-defined commands before @value{GDBN} suspects an
23209 infinite recursion and aborts the command.
23210 This does not apply to user-defined python commands.
23213 In addition to the above commands, user-defined commands frequently
23214 use control flow commands, described in @ref{Command Files}.
23216 When user-defined commands are executed, the
23217 commands of the definition are not printed. An error in any command
23218 stops execution of the user-defined command.
23220 If used interactively, commands that would ask for confirmation proceed
23221 without asking when used inside a user-defined command. Many @value{GDBN}
23222 commands that normally print messages to say what they are doing omit the
23223 messages when used in a user-defined command.
23226 @subsection User-defined Command Hooks
23227 @cindex command hooks
23228 @cindex hooks, for commands
23229 @cindex hooks, pre-command
23232 You may define @dfn{hooks}, which are a special kind of user-defined
23233 command. Whenever you run the command @samp{foo}, if the user-defined
23234 command @samp{hook-foo} exists, it is executed (with no arguments)
23235 before that command.
23237 @cindex hooks, post-command
23239 A hook may also be defined which is run after the command you executed.
23240 Whenever you run the command @samp{foo}, if the user-defined command
23241 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23242 that command. Post-execution hooks may exist simultaneously with
23243 pre-execution hooks, for the same command.
23245 It is valid for a hook to call the command which it hooks. If this
23246 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23248 @c It would be nice if hookpost could be passed a parameter indicating
23249 @c if the command it hooks executed properly or not. FIXME!
23251 @kindex stop@r{, a pseudo-command}
23252 In addition, a pseudo-command, @samp{stop} exists. Defining
23253 (@samp{hook-stop}) makes the associated commands execute every time
23254 execution stops in your program: before breakpoint commands are run,
23255 displays are printed, or the stack frame is printed.
23257 For example, to ignore @code{SIGALRM} signals while
23258 single-stepping, but treat them normally during normal execution,
23263 handle SIGALRM nopass
23267 handle SIGALRM pass
23270 define hook-continue
23271 handle SIGALRM pass
23275 As a further example, to hook at the beginning and end of the @code{echo}
23276 command, and to add extra text to the beginning and end of the message,
23284 define hookpost-echo
23288 (@value{GDBP}) echo Hello World
23289 <<<---Hello World--->>>
23294 You can define a hook for any single-word command in @value{GDBN}, but
23295 not for command aliases; you should define a hook for the basic command
23296 name, e.g.@: @code{backtrace} rather than @code{bt}.
23297 @c FIXME! So how does Joe User discover whether a command is an alias
23299 You can hook a multi-word command by adding @code{hook-} or
23300 @code{hookpost-} to the last word of the command, e.g.@:
23301 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23303 If an error occurs during the execution of your hook, execution of
23304 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23305 (before the command that you actually typed had a chance to run).
23307 If you try to define a hook which does not match any known command, you
23308 get a warning from the @code{define} command.
23310 @node Command Files
23311 @subsection Command Files
23313 @cindex command files
23314 @cindex scripting commands
23315 A command file for @value{GDBN} is a text file made of lines that are
23316 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23317 also be included. An empty line in a command file does nothing; it
23318 does not mean to repeat the last command, as it would from the
23321 You can request the execution of a command file with the @code{source}
23322 command. Note that the @code{source} command is also used to evaluate
23323 scripts that are not Command Files. The exact behavior can be configured
23324 using the @code{script-extension} setting.
23325 @xref{Extending GDB,, Extending GDB}.
23329 @cindex execute commands from a file
23330 @item source [-s] [-v] @var{filename}
23331 Execute the command file @var{filename}.
23334 The lines in a command file are generally executed sequentially,
23335 unless the order of execution is changed by one of the
23336 @emph{flow-control commands} described below. The commands are not
23337 printed as they are executed. An error in any command terminates
23338 execution of the command file and control is returned to the console.
23340 @value{GDBN} first searches for @var{filename} in the current directory.
23341 If the file is not found there, and @var{filename} does not specify a
23342 directory, then @value{GDBN} also looks for the file on the source search path
23343 (specified with the @samp{directory} command);
23344 except that @file{$cdir} is not searched because the compilation directory
23345 is not relevant to scripts.
23347 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23348 on the search path even if @var{filename} specifies a directory.
23349 The search is done by appending @var{filename} to each element of the
23350 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23351 and the search path contains @file{/home/user} then @value{GDBN} will
23352 look for the script @file{/home/user/mylib/myscript}.
23353 The search is also done if @var{filename} is an absolute path.
23354 For example, if @var{filename} is @file{/tmp/myscript} and
23355 the search path contains @file{/home/user} then @value{GDBN} will
23356 look for the script @file{/home/user/tmp/myscript}.
23357 For DOS-like systems, if @var{filename} contains a drive specification,
23358 it is stripped before concatenation. For example, if @var{filename} is
23359 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23360 will look for the script @file{c:/tmp/myscript}.
23362 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23363 each command as it is executed. The option must be given before
23364 @var{filename}, and is interpreted as part of the filename anywhere else.
23366 Commands that would ask for confirmation if used interactively proceed
23367 without asking when used in a command file. Many @value{GDBN} commands that
23368 normally print messages to say what they are doing omit the messages
23369 when called from command files.
23371 @value{GDBN} also accepts command input from standard input. In this
23372 mode, normal output goes to standard output and error output goes to
23373 standard error. Errors in a command file supplied on standard input do
23374 not terminate execution of the command file---execution continues with
23378 gdb < cmds > log 2>&1
23381 (The syntax above will vary depending on the shell used.) This example
23382 will execute commands from the file @file{cmds}. All output and errors
23383 would be directed to @file{log}.
23385 Since commands stored on command files tend to be more general than
23386 commands typed interactively, they frequently need to deal with
23387 complicated situations, such as different or unexpected values of
23388 variables and symbols, changes in how the program being debugged is
23389 built, etc. @value{GDBN} provides a set of flow-control commands to
23390 deal with these complexities. Using these commands, you can write
23391 complex scripts that loop over data structures, execute commands
23392 conditionally, etc.
23399 This command allows to include in your script conditionally executed
23400 commands. The @code{if} command takes a single argument, which is an
23401 expression to evaluate. It is followed by a series of commands that
23402 are executed only if the expression is true (its value is nonzero).
23403 There can then optionally be an @code{else} line, followed by a series
23404 of commands that are only executed if the expression was false. The
23405 end of the list is marked by a line containing @code{end}.
23409 This command allows to write loops. Its syntax is similar to
23410 @code{if}: the command takes a single argument, which is an expression
23411 to evaluate, and must be followed by the commands to execute, one per
23412 line, terminated by an @code{end}. These commands are called the
23413 @dfn{body} of the loop. The commands in the body of @code{while} are
23414 executed repeatedly as long as the expression evaluates to true.
23418 This command exits the @code{while} loop in whose body it is included.
23419 Execution of the script continues after that @code{while}s @code{end}
23422 @kindex loop_continue
23423 @item loop_continue
23424 This command skips the execution of the rest of the body of commands
23425 in the @code{while} loop in whose body it is included. Execution
23426 branches to the beginning of the @code{while} loop, where it evaluates
23427 the controlling expression.
23429 @kindex end@r{ (if/else/while commands)}
23431 Terminate the block of commands that are the body of @code{if},
23432 @code{else}, or @code{while} flow-control commands.
23437 @subsection Commands for Controlled Output
23439 During the execution of a command file or a user-defined command, normal
23440 @value{GDBN} output is suppressed; the only output that appears is what is
23441 explicitly printed by the commands in the definition. This section
23442 describes three commands useful for generating exactly the output you
23447 @item echo @var{text}
23448 @c I do not consider backslash-space a standard C escape sequence
23449 @c because it is not in ANSI.
23450 Print @var{text}. Nonprinting characters can be included in
23451 @var{text} using C escape sequences, such as @samp{\n} to print a
23452 newline. @strong{No newline is printed unless you specify one.}
23453 In addition to the standard C escape sequences, a backslash followed
23454 by a space stands for a space. This is useful for displaying a
23455 string with spaces at the beginning or the end, since leading and
23456 trailing spaces are otherwise trimmed from all arguments.
23457 To print @samp{@w{ }and foo =@w{ }}, use the command
23458 @samp{echo \@w{ }and foo = \@w{ }}.
23460 A backslash at the end of @var{text} can be used, as in C, to continue
23461 the command onto subsequent lines. For example,
23464 echo This is some text\n\
23465 which is continued\n\
23466 onto several lines.\n
23469 produces the same output as
23472 echo This is some text\n
23473 echo which is continued\n
23474 echo onto several lines.\n
23478 @item output @var{expression}
23479 Print the value of @var{expression} and nothing but that value: no
23480 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23481 value history either. @xref{Expressions, ,Expressions}, for more information
23484 @item output/@var{fmt} @var{expression}
23485 Print the value of @var{expression} in format @var{fmt}. You can use
23486 the same formats as for @code{print}. @xref{Output Formats,,Output
23487 Formats}, for more information.
23490 @item printf @var{template}, @var{expressions}@dots{}
23491 Print the values of one or more @var{expressions} under the control of
23492 the string @var{template}. To print several values, make
23493 @var{expressions} be a comma-separated list of individual expressions,
23494 which may be either numbers or pointers. Their values are printed as
23495 specified by @var{template}, exactly as a C program would do by
23496 executing the code below:
23499 printf (@var{template}, @var{expressions}@dots{});
23502 As in @code{C} @code{printf}, ordinary characters in @var{template}
23503 are printed verbatim, while @dfn{conversion specification} introduced
23504 by the @samp{%} character cause subsequent @var{expressions} to be
23505 evaluated, their values converted and formatted according to type and
23506 style information encoded in the conversion specifications, and then
23509 For example, you can print two values in hex like this:
23512 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23515 @code{printf} supports all the standard @code{C} conversion
23516 specifications, including the flags and modifiers between the @samp{%}
23517 character and the conversion letter, with the following exceptions:
23521 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23524 The modifier @samp{*} is not supported for specifying precision or
23528 The @samp{'} flag (for separation of digits into groups according to
23529 @code{LC_NUMERIC'}) is not supported.
23532 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23536 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23539 The conversion letters @samp{a} and @samp{A} are not supported.
23543 Note that the @samp{ll} type modifier is supported only if the
23544 underlying @code{C} implementation used to build @value{GDBN} supports
23545 the @code{long long int} type, and the @samp{L} type modifier is
23546 supported only if @code{long double} type is available.
23548 As in @code{C}, @code{printf} supports simple backslash-escape
23549 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23550 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23551 single character. Octal and hexadecimal escape sequences are not
23554 Additionally, @code{printf} supports conversion specifications for DFP
23555 (@dfn{Decimal Floating Point}) types using the following length modifiers
23556 together with a floating point specifier.
23561 @samp{H} for printing @code{Decimal32} types.
23564 @samp{D} for printing @code{Decimal64} types.
23567 @samp{DD} for printing @code{Decimal128} types.
23570 If the underlying @code{C} implementation used to build @value{GDBN} has
23571 support for the three length modifiers for DFP types, other modifiers
23572 such as width and precision will also be available for @value{GDBN} to use.
23574 In case there is no such @code{C} support, no additional modifiers will be
23575 available and the value will be printed in the standard way.
23577 Here's an example of printing DFP types using the above conversion letters:
23579 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23583 @item eval @var{template}, @var{expressions}@dots{}
23584 Convert the values of one or more @var{expressions} under the control of
23585 the string @var{template} to a command line, and call it.
23589 @node Auto-loading sequences
23590 @subsection Controlling auto-loading native @value{GDBN} scripts
23591 @cindex native script auto-loading
23593 When a new object file is read (for example, due to the @code{file}
23594 command, or because the inferior has loaded a shared library),
23595 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23596 @xref{Auto-loading extensions}.
23598 Auto-loading can be enabled or disabled,
23599 and the list of auto-loaded scripts can be printed.
23602 @anchor{set auto-load gdb-scripts}
23603 @kindex set auto-load gdb-scripts
23604 @item set auto-load gdb-scripts [on|off]
23605 Enable or disable the auto-loading of canned sequences of commands scripts.
23607 @anchor{show auto-load gdb-scripts}
23608 @kindex show auto-load gdb-scripts
23609 @item show auto-load gdb-scripts
23610 Show whether auto-loading of canned sequences of commands scripts is enabled or
23613 @anchor{info auto-load gdb-scripts}
23614 @kindex info auto-load gdb-scripts
23615 @cindex print list of auto-loaded canned sequences of commands scripts
23616 @item info auto-load gdb-scripts [@var{regexp}]
23617 Print the list of all canned sequences of commands scripts that @value{GDBN}
23621 If @var{regexp} is supplied only canned sequences of commands scripts with
23622 matching names are printed.
23624 @c Python docs live in a separate file.
23625 @include python.texi
23627 @c Guile docs live in a separate file.
23628 @include guile.texi
23630 @node Auto-loading extensions
23631 @section Auto-loading extensions
23632 @cindex auto-loading extensions
23634 @value{GDBN} provides two mechanisms for automatically loading extensions
23635 when a new object file is read (for example, due to the @code{file}
23636 command, or because the inferior has loaded a shared library):
23637 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
23638 section of modern file formats like ELF.
23641 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
23642 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
23643 * Which flavor to choose?::
23646 The auto-loading feature is useful for supplying application-specific
23647 debugging commands and features.
23649 Auto-loading can be enabled or disabled,
23650 and the list of auto-loaded scripts can be printed.
23651 See the @samp{auto-loading} section of each extension language
23652 for more information.
23653 For @value{GDBN} command files see @ref{Auto-loading sequences}.
23654 For Python files see @ref{Python Auto-loading}.
23656 Note that loading of this script file also requires accordingly configured
23657 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23659 @node objfile-gdbdotext file
23660 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
23661 @cindex @file{@var{objfile}-gdb.gdb}
23662 @cindex @file{@var{objfile}-gdb.py}
23663 @cindex @file{@var{objfile}-gdb.scm}
23665 When a new object file is read, @value{GDBN} looks for a file named
23666 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
23667 where @var{objfile} is the object file's name and
23668 where @var{ext} is the file extension for the extension language:
23671 @item @file{@var{objfile}-gdb.gdb}
23672 GDB's own command language
23673 @item @file{@var{objfile}-gdb.py}
23675 @item @file{@var{objfile}-gdb.scm}
23679 @var{script-name} is formed by ensuring that the file name of @var{objfile}
23680 is absolute, following all symlinks, and resolving @code{.} and @code{..}
23681 components, and appending the @file{-gdb.@var{ext}} suffix.
23682 If this file exists and is readable, @value{GDBN} will evaluate it as a
23683 script in the specified extension language.
23685 If this file does not exist, then @value{GDBN} will look for
23686 @var{script-name} file in all of the directories as specified below.
23688 Note that loading of these files requires an accordingly configured
23689 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23691 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
23692 scripts normally according to its @file{.exe} filename. But if no scripts are
23693 found @value{GDBN} also tries script filenames matching the object file without
23694 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
23695 is attempted on any platform. This makes the script filenames compatible
23696 between Unix and MS-Windows hosts.
23699 @anchor{set auto-load scripts-directory}
23700 @kindex set auto-load scripts-directory
23701 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
23702 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
23703 may be delimited by the host platform path separator in use
23704 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
23706 Each entry here needs to be covered also by the security setting
23707 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
23709 @anchor{with-auto-load-dir}
23710 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
23711 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
23712 configuration option @option{--with-auto-load-dir}.
23714 Any reference to @file{$debugdir} will get replaced by
23715 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
23716 reference to @file{$datadir} will get replaced by @var{data-directory} which is
23717 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
23718 @file{$datadir} must be placed as a directory component --- either alone or
23719 delimited by @file{/} or @file{\} directory separators, depending on the host
23722 The list of directories uses path separator (@samp{:} on GNU and Unix
23723 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23724 to the @env{PATH} environment variable.
23726 @anchor{show auto-load scripts-directory}
23727 @kindex show auto-load scripts-directory
23728 @item show auto-load scripts-directory
23729 Show @value{GDBN} auto-loaded scripts location.
23732 @value{GDBN} does not track which files it has already auto-loaded this way.
23733 @value{GDBN} will load the associated script every time the corresponding
23734 @var{objfile} is opened.
23735 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
23736 is evaluated more than once.
23738 @node dotdebug_gdb_scripts section
23739 @subsection The @code{.debug_gdb_scripts} section
23740 @cindex @code{.debug_gdb_scripts} section
23742 For systems using file formats like ELF and COFF,
23743 when @value{GDBN} loads a new object file
23744 it will look for a special section named @code{.debug_gdb_scripts}.
23745 If this section exists, its contents is a list of NUL-terminated names
23746 of scripts to load. Each entry begins with a non-NULL prefix byte that
23747 specifies the kind of entry, typically the extension language.
23749 @value{GDBN} will look for each specified script file first in the
23750 current directory and then along the source search path
23751 (@pxref{Source Path, ,Specifying Source Directories}),
23752 except that @file{$cdir} is not searched, since the compilation
23753 directory is not relevant to scripts.
23755 Entries can be placed in section @code{.debug_gdb_scripts} with,
23756 for example, this GCC macro for Python scripts.
23759 /* Note: The "MS" section flags are to remove duplicates. */
23760 #define DEFINE_GDB_PY_SCRIPT(script_name) \
23762 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23763 .byte 1 /* Python */\n\
23764 .asciz \"" script_name "\"\n\
23770 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
23771 Then one can reference the macro in a header or source file like this:
23774 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
23777 The script name may include directories if desired.
23779 Note that loading of this script file also requires accordingly configured
23780 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23782 If the macro invocation is put in a header, any application or library
23783 using this header will get a reference to the specified script,
23784 and with the use of @code{"MS"} attributes on the section, the linker
23785 will remove duplicates.
23787 @node Which flavor to choose?
23788 @subsection Which flavor to choose?
23790 Given the multiple ways of auto-loading extensions, it might not always
23791 be clear which one to choose. This section provides some guidance.
23794 Benefits of the @file{-gdb.@var{ext}} way:
23798 Can be used with file formats that don't support multiple sections.
23801 Ease of finding scripts for public libraries.
23803 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23804 in the source search path.
23805 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23806 isn't a source directory in which to find the script.
23809 Doesn't require source code additions.
23813 Benefits of the @code{.debug_gdb_scripts} way:
23817 Works with static linking.
23819 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
23820 trigger their loading. When an application is statically linked the only
23821 objfile available is the executable, and it is cumbersome to attach all the
23822 scripts from all the input libraries to the executable's
23823 @file{-gdb.@var{ext}} script.
23826 Works with classes that are entirely inlined.
23828 Some classes can be entirely inlined, and thus there may not be an associated
23829 shared library to attach a @file{-gdb.@var{ext}} script to.
23832 Scripts needn't be copied out of the source tree.
23834 In some circumstances, apps can be built out of large collections of internal
23835 libraries, and the build infrastructure necessary to install the
23836 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
23837 cumbersome. It may be easier to specify the scripts in the
23838 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23839 top of the source tree to the source search path.
23842 @node Multiple Extension Languages
23843 @section Multiple Extension Languages
23845 The Guile and Python extension languages do not share any state,
23846 and generally do not interfere with each other.
23847 There are some things to be aware of, however.
23849 @subsection Python comes first
23851 Python was @value{GDBN}'s first extension language, and to avoid breaking
23852 existing behaviour Python comes first. This is generally solved by the
23853 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
23854 extension languages, and when it makes a call to an extension language,
23855 (say to pretty-print a value), it tries each in turn until an extension
23856 language indicates it has performed the request (e.g., has returned the
23857 pretty-printed form of a value).
23858 This extends to errors while performing such requests: If an error happens
23859 while, for example, trying to pretty-print an object then the error is
23860 reported and any following extension languages are not tried.
23863 @section Creating new spellings of existing commands
23864 @cindex aliases for commands
23866 It is often useful to define alternate spellings of existing commands.
23867 For example, if a new @value{GDBN} command defined in Python has
23868 a long name to type, it is handy to have an abbreviated version of it
23869 that involves less typing.
23871 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
23872 of the @samp{step} command even though it is otherwise an ambiguous
23873 abbreviation of other commands like @samp{set} and @samp{show}.
23875 Aliases are also used to provide shortened or more common versions
23876 of multi-word commands. For example, @value{GDBN} provides the
23877 @samp{tty} alias of the @samp{set inferior-tty} command.
23879 You can define a new alias with the @samp{alias} command.
23884 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
23888 @var{ALIAS} specifies the name of the new alias.
23889 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
23892 @var{COMMAND} specifies the name of an existing command
23893 that is being aliased.
23895 The @samp{-a} option specifies that the new alias is an abbreviation
23896 of the command. Abbreviations are not shown in command
23897 lists displayed by the @samp{help} command.
23899 The @samp{--} option specifies the end of options,
23900 and is useful when @var{ALIAS} begins with a dash.
23902 Here is a simple example showing how to make an abbreviation
23903 of a command so that there is less to type.
23904 Suppose you were tired of typing @samp{disas}, the current
23905 shortest unambiguous abbreviation of the @samp{disassemble} command
23906 and you wanted an even shorter version named @samp{di}.
23907 The following will accomplish this.
23910 (gdb) alias -a di = disas
23913 Note that aliases are different from user-defined commands.
23914 With a user-defined command, you also need to write documentation
23915 for it with the @samp{document} command.
23916 An alias automatically picks up the documentation of the existing command.
23918 Here is an example where we make @samp{elms} an abbreviation of
23919 @samp{elements} in the @samp{set print elements} command.
23920 This is to show that you can make an abbreviation of any part
23924 (gdb) alias -a set print elms = set print elements
23925 (gdb) alias -a show print elms = show print elements
23926 (gdb) set p elms 20
23928 Limit on string chars or array elements to print is 200.
23931 Note that if you are defining an alias of a @samp{set} command,
23932 and you want to have an alias for the corresponding @samp{show}
23933 command, then you need to define the latter separately.
23935 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
23936 @var{ALIAS}, just as they are normally.
23939 (gdb) alias -a set pr elms = set p ele
23942 Finally, here is an example showing the creation of a one word
23943 alias for a more complex command.
23944 This creates alias @samp{spe} of the command @samp{set print elements}.
23947 (gdb) alias spe = set print elements
23952 @chapter Command Interpreters
23953 @cindex command interpreters
23955 @value{GDBN} supports multiple command interpreters, and some command
23956 infrastructure to allow users or user interface writers to switch
23957 between interpreters or run commands in other interpreters.
23959 @value{GDBN} currently supports two command interpreters, the console
23960 interpreter (sometimes called the command-line interpreter or @sc{cli})
23961 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23962 describes both of these interfaces in great detail.
23964 By default, @value{GDBN} will start with the console interpreter.
23965 However, the user may choose to start @value{GDBN} with another
23966 interpreter by specifying the @option{-i} or @option{--interpreter}
23967 startup options. Defined interpreters include:
23971 @cindex console interpreter
23972 The traditional console or command-line interpreter. This is the most often
23973 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23974 @value{GDBN} will use this interpreter.
23977 @cindex mi interpreter
23978 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23979 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23980 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23984 @cindex mi2 interpreter
23985 The current @sc{gdb/mi} interface.
23988 @cindex mi1 interpreter
23989 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23993 @cindex invoke another interpreter
23994 The interpreter being used by @value{GDBN} may not be dynamically
23995 switched at runtime. Although possible, this could lead to a very
23996 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23997 enters the command "interpreter-set console" in a console view,
23998 @value{GDBN} would switch to using the console interpreter, rendering
23999 the IDE inoperable!
24001 @kindex interpreter-exec
24002 Although you may only choose a single interpreter at startup, you may execute
24003 commands in any interpreter from the current interpreter using the appropriate
24004 command. If you are running the console interpreter, simply use the
24005 @code{interpreter-exec} command:
24008 interpreter-exec mi "-data-list-register-names"
24011 @sc{gdb/mi} has a similar command, although it is only available in versions of
24012 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24015 @chapter @value{GDBN} Text User Interface
24017 @cindex Text User Interface
24020 * TUI Overview:: TUI overview
24021 * TUI Keys:: TUI key bindings
24022 * TUI Single Key Mode:: TUI single key mode
24023 * TUI Commands:: TUI-specific commands
24024 * TUI Configuration:: TUI configuration variables
24027 The @value{GDBN} Text User Interface (TUI) is a terminal
24028 interface which uses the @code{curses} library to show the source
24029 file, the assembly output, the program registers and @value{GDBN}
24030 commands in separate text windows. The TUI mode is supported only
24031 on platforms where a suitable version of the @code{curses} library
24034 The TUI mode is enabled by default when you invoke @value{GDBN} as
24035 @samp{@value{GDBP} -tui}.
24036 You can also switch in and out of TUI mode while @value{GDBN} runs by
24037 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24038 @xref{TUI Keys, ,TUI Key Bindings}.
24041 @section TUI Overview
24043 In TUI mode, @value{GDBN} can display several text windows:
24047 This window is the @value{GDBN} command window with the @value{GDBN}
24048 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24049 managed using readline.
24052 The source window shows the source file of the program. The current
24053 line and active breakpoints are displayed in this window.
24056 The assembly window shows the disassembly output of the program.
24059 This window shows the processor registers. Registers are highlighted
24060 when their values change.
24063 The source and assembly windows show the current program position
24064 by highlighting the current line and marking it with a @samp{>} marker.
24065 Breakpoints are indicated with two markers. The first marker
24066 indicates the breakpoint type:
24070 Breakpoint which was hit at least once.
24073 Breakpoint which was never hit.
24076 Hardware breakpoint which was hit at least once.
24079 Hardware breakpoint which was never hit.
24082 The second marker indicates whether the breakpoint is enabled or not:
24086 Breakpoint is enabled.
24089 Breakpoint is disabled.
24092 The source, assembly and register windows are updated when the current
24093 thread changes, when the frame changes, or when the program counter
24096 These windows are not all visible at the same time. The command
24097 window is always visible. The others can be arranged in several
24108 source and assembly,
24111 source and registers, or
24114 assembly and registers.
24117 A status line above the command window shows the following information:
24121 Indicates the current @value{GDBN} target.
24122 (@pxref{Targets, ,Specifying a Debugging Target}).
24125 Gives the current process or thread number.
24126 When no process is being debugged, this field is set to @code{No process}.
24129 Gives the current function name for the selected frame.
24130 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24131 When there is no symbol corresponding to the current program counter,
24132 the string @code{??} is displayed.
24135 Indicates the current line number for the selected frame.
24136 When the current line number is not known, the string @code{??} is displayed.
24139 Indicates the current program counter address.
24143 @section TUI Key Bindings
24144 @cindex TUI key bindings
24146 The TUI installs several key bindings in the readline keymaps
24147 @ifset SYSTEM_READLINE
24148 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24150 @ifclear SYSTEM_READLINE
24151 (@pxref{Command Line Editing}).
24153 The following key bindings are installed for both TUI mode and the
24154 @value{GDBN} standard mode.
24163 Enter or leave the TUI mode. When leaving the TUI mode,
24164 the curses window management stops and @value{GDBN} operates using
24165 its standard mode, writing on the terminal directly. When reentering
24166 the TUI mode, control is given back to the curses windows.
24167 The screen is then refreshed.
24171 Use a TUI layout with only one window. The layout will
24172 either be @samp{source} or @samp{assembly}. When the TUI mode
24173 is not active, it will switch to the TUI mode.
24175 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24179 Use a TUI layout with at least two windows. When the current
24180 layout already has two windows, the next layout with two windows is used.
24181 When a new layout is chosen, one window will always be common to the
24182 previous layout and the new one.
24184 Think of it as the Emacs @kbd{C-x 2} binding.
24188 Change the active window. The TUI associates several key bindings
24189 (like scrolling and arrow keys) with the active window. This command
24190 gives the focus to the next TUI window.
24192 Think of it as the Emacs @kbd{C-x o} binding.
24196 Switch in and out of the TUI SingleKey mode that binds single
24197 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24200 The following key bindings only work in the TUI mode:
24205 Scroll the active window one page up.
24209 Scroll the active window one page down.
24213 Scroll the active window one line up.
24217 Scroll the active window one line down.
24221 Scroll the active window one column left.
24225 Scroll the active window one column right.
24229 Refresh the screen.
24232 Because the arrow keys scroll the active window in the TUI mode, they
24233 are not available for their normal use by readline unless the command
24234 window has the focus. When another window is active, you must use
24235 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24236 and @kbd{C-f} to control the command window.
24238 @node TUI Single Key Mode
24239 @section TUI Single Key Mode
24240 @cindex TUI single key mode
24242 The TUI also provides a @dfn{SingleKey} mode, which binds several
24243 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24244 switch into this mode, where the following key bindings are used:
24247 @kindex c @r{(SingleKey TUI key)}
24251 @kindex d @r{(SingleKey TUI key)}
24255 @kindex f @r{(SingleKey TUI key)}
24259 @kindex n @r{(SingleKey TUI key)}
24263 @kindex q @r{(SingleKey TUI key)}
24265 exit the SingleKey mode.
24267 @kindex r @r{(SingleKey TUI key)}
24271 @kindex s @r{(SingleKey TUI key)}
24275 @kindex u @r{(SingleKey TUI key)}
24279 @kindex v @r{(SingleKey TUI key)}
24283 @kindex w @r{(SingleKey TUI key)}
24288 Other keys temporarily switch to the @value{GDBN} command prompt.
24289 The key that was pressed is inserted in the editing buffer so that
24290 it is possible to type most @value{GDBN} commands without interaction
24291 with the TUI SingleKey mode. Once the command is entered the TUI
24292 SingleKey mode is restored. The only way to permanently leave
24293 this mode is by typing @kbd{q} or @kbd{C-x s}.
24297 @section TUI-specific Commands
24298 @cindex TUI commands
24300 The TUI has specific commands to control the text windows.
24301 These commands are always available, even when @value{GDBN} is not in
24302 the TUI mode. When @value{GDBN} is in the standard mode, most
24303 of these commands will automatically switch to the TUI mode.
24305 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24306 terminal, or @value{GDBN} has been started with the machine interface
24307 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24308 these commands will fail with an error, because it would not be
24309 possible or desirable to enable curses window management.
24314 List and give the size of all displayed windows.
24318 Display the next layout.
24321 Display the previous layout.
24324 Display the source window only.
24327 Display the assembly window only.
24330 Display the source and assembly window.
24333 Display the register window together with the source or assembly window.
24337 Make the next window active for scrolling.
24340 Make the previous window active for scrolling.
24343 Make the source window active for scrolling.
24346 Make the assembly window active for scrolling.
24349 Make the register window active for scrolling.
24352 Make the command window active for scrolling.
24356 Refresh the screen. This is similar to typing @kbd{C-L}.
24358 @item tui reg float
24360 Show the floating point registers in the register window.
24362 @item tui reg general
24363 Show the general registers in the register window.
24366 Show the next register group. The list of register groups as well as
24367 their order is target specific. The predefined register groups are the
24368 following: @code{general}, @code{float}, @code{system}, @code{vector},
24369 @code{all}, @code{save}, @code{restore}.
24371 @item tui reg system
24372 Show the system registers in the register window.
24376 Update the source window and the current execution point.
24378 @item winheight @var{name} +@var{count}
24379 @itemx winheight @var{name} -@var{count}
24381 Change the height of the window @var{name} by @var{count}
24382 lines. Positive counts increase the height, while negative counts
24385 @item tabset @var{nchars}
24387 Set the width of tab stops to be @var{nchars} characters.
24390 @node TUI Configuration
24391 @section TUI Configuration Variables
24392 @cindex TUI configuration variables
24394 Several configuration variables control the appearance of TUI windows.
24397 @item set tui border-kind @var{kind}
24398 @kindex set tui border-kind
24399 Select the border appearance for the source, assembly and register windows.
24400 The possible values are the following:
24403 Use a space character to draw the border.
24406 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24409 Use the Alternate Character Set to draw the border. The border is
24410 drawn using character line graphics if the terminal supports them.
24413 @item set tui border-mode @var{mode}
24414 @kindex set tui border-mode
24415 @itemx set tui active-border-mode @var{mode}
24416 @kindex set tui active-border-mode
24417 Select the display attributes for the borders of the inactive windows
24418 or the active window. The @var{mode} can be one of the following:
24421 Use normal attributes to display the border.
24427 Use reverse video mode.
24430 Use half bright mode.
24432 @item half-standout
24433 Use half bright and standout mode.
24436 Use extra bright or bold mode.
24438 @item bold-standout
24439 Use extra bright or bold and standout mode.
24444 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24447 @cindex @sc{gnu} Emacs
24448 A special interface allows you to use @sc{gnu} Emacs to view (and
24449 edit) the source files for the program you are debugging with
24452 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24453 executable file you want to debug as an argument. This command starts
24454 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24455 created Emacs buffer.
24456 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24458 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24463 All ``terminal'' input and output goes through an Emacs buffer, called
24466 This applies both to @value{GDBN} commands and their output, and to the input
24467 and output done by the program you are debugging.
24469 This is useful because it means that you can copy the text of previous
24470 commands and input them again; you can even use parts of the output
24473 All the facilities of Emacs' Shell mode are available for interacting
24474 with your program. In particular, you can send signals the usual
24475 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24479 @value{GDBN} displays source code through Emacs.
24481 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24482 source file for that frame and puts an arrow (@samp{=>}) at the
24483 left margin of the current line. Emacs uses a separate buffer for
24484 source display, and splits the screen to show both your @value{GDBN} session
24487 Explicit @value{GDBN} @code{list} or search commands still produce output as
24488 usual, but you probably have no reason to use them from Emacs.
24491 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24492 a graphical mode, enabled by default, which provides further buffers
24493 that can control the execution and describe the state of your program.
24494 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24496 If you specify an absolute file name when prompted for the @kbd{M-x
24497 gdb} argument, then Emacs sets your current working directory to where
24498 your program resides. If you only specify the file name, then Emacs
24499 sets your current working directory to the directory associated
24500 with the previous buffer. In this case, @value{GDBN} may find your
24501 program by searching your environment's @code{PATH} variable, but on
24502 some operating systems it might not find the source. So, although the
24503 @value{GDBN} input and output session proceeds normally, the auxiliary
24504 buffer does not display the current source and line of execution.
24506 The initial working directory of @value{GDBN} is printed on the top
24507 line of the GUD buffer and this serves as a default for the commands
24508 that specify files for @value{GDBN} to operate on. @xref{Files,
24509 ,Commands to Specify Files}.
24511 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24512 need to call @value{GDBN} by a different name (for example, if you
24513 keep several configurations around, with different names) you can
24514 customize the Emacs variable @code{gud-gdb-command-name} to run the
24517 In the GUD buffer, you can use these special Emacs commands in
24518 addition to the standard Shell mode commands:
24522 Describe the features of Emacs' GUD Mode.
24525 Execute to another source line, like the @value{GDBN} @code{step} command; also
24526 update the display window to show the current file and location.
24529 Execute to next source line in this function, skipping all function
24530 calls, like the @value{GDBN} @code{next} command. Then update the display window
24531 to show the current file and location.
24534 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24535 display window accordingly.
24538 Execute until exit from the selected stack frame, like the @value{GDBN}
24539 @code{finish} command.
24542 Continue execution of your program, like the @value{GDBN} @code{continue}
24546 Go up the number of frames indicated by the numeric argument
24547 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24548 like the @value{GDBN} @code{up} command.
24551 Go down the number of frames indicated by the numeric argument, like the
24552 @value{GDBN} @code{down} command.
24555 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24556 tells @value{GDBN} to set a breakpoint on the source line point is on.
24558 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24559 separate frame which shows a backtrace when the GUD buffer is current.
24560 Move point to any frame in the stack and type @key{RET} to make it
24561 become the current frame and display the associated source in the
24562 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24563 selected frame become the current one. In graphical mode, the
24564 speedbar displays watch expressions.
24566 If you accidentally delete the source-display buffer, an easy way to get
24567 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24568 request a frame display; when you run under Emacs, this recreates
24569 the source buffer if necessary to show you the context of the current
24572 The source files displayed in Emacs are in ordinary Emacs buffers
24573 which are visiting the source files in the usual way. You can edit
24574 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24575 communicates with Emacs in terms of line numbers. If you add or
24576 delete lines from the text, the line numbers that @value{GDBN} knows cease
24577 to correspond properly with the code.
24579 A more detailed description of Emacs' interaction with @value{GDBN} is
24580 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24584 @chapter The @sc{gdb/mi} Interface
24586 @unnumberedsec Function and Purpose
24588 @cindex @sc{gdb/mi}, its purpose
24589 @sc{gdb/mi} is a line based machine oriented text interface to
24590 @value{GDBN} and is activated by specifying using the
24591 @option{--interpreter} command line option (@pxref{Mode Options}). It
24592 is specifically intended to support the development of systems which
24593 use the debugger as just one small component of a larger system.
24595 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24596 in the form of a reference manual.
24598 Note that @sc{gdb/mi} is still under construction, so some of the
24599 features described below are incomplete and subject to change
24600 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24602 @unnumberedsec Notation and Terminology
24604 @cindex notational conventions, for @sc{gdb/mi}
24605 This chapter uses the following notation:
24609 @code{|} separates two alternatives.
24612 @code{[ @var{something} ]} indicates that @var{something} is optional:
24613 it may or may not be given.
24616 @code{( @var{group} )*} means that @var{group} inside the parentheses
24617 may repeat zero or more times.
24620 @code{( @var{group} )+} means that @var{group} inside the parentheses
24621 may repeat one or more times.
24624 @code{"@var{string}"} means a literal @var{string}.
24628 @heading Dependencies
24632 * GDB/MI General Design::
24633 * GDB/MI Command Syntax::
24634 * GDB/MI Compatibility with CLI::
24635 * GDB/MI Development and Front Ends::
24636 * GDB/MI Output Records::
24637 * GDB/MI Simple Examples::
24638 * GDB/MI Command Description Format::
24639 * GDB/MI Breakpoint Commands::
24640 * GDB/MI Catchpoint Commands::
24641 * GDB/MI Program Context::
24642 * GDB/MI Thread Commands::
24643 * GDB/MI Ada Tasking Commands::
24644 * GDB/MI Program Execution::
24645 * GDB/MI Stack Manipulation::
24646 * GDB/MI Variable Objects::
24647 * GDB/MI Data Manipulation::
24648 * GDB/MI Tracepoint Commands::
24649 * GDB/MI Symbol Query::
24650 * GDB/MI File Commands::
24652 * GDB/MI Kod Commands::
24653 * GDB/MI Memory Overlay Commands::
24654 * GDB/MI Signal Handling Commands::
24656 * GDB/MI Target Manipulation::
24657 * GDB/MI File Transfer Commands::
24658 * GDB/MI Ada Exceptions Commands::
24659 * GDB/MI Support Commands::
24660 * GDB/MI Miscellaneous Commands::
24663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24664 @node GDB/MI General Design
24665 @section @sc{gdb/mi} General Design
24666 @cindex GDB/MI General Design
24668 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24669 parts---commands sent to @value{GDBN}, responses to those commands
24670 and notifications. Each command results in exactly one response,
24671 indicating either successful completion of the command, or an error.
24672 For the commands that do not resume the target, the response contains the
24673 requested information. For the commands that resume the target, the
24674 response only indicates whether the target was successfully resumed.
24675 Notifications is the mechanism for reporting changes in the state of the
24676 target, or in @value{GDBN} state, that cannot conveniently be associated with
24677 a command and reported as part of that command response.
24679 The important examples of notifications are:
24683 Exec notifications. These are used to report changes in
24684 target state---when a target is resumed, or stopped. It would not
24685 be feasible to include this information in response of resuming
24686 commands, because one resume commands can result in multiple events in
24687 different threads. Also, quite some time may pass before any event
24688 happens in the target, while a frontend needs to know whether the resuming
24689 command itself was successfully executed.
24692 Console output, and status notifications. Console output
24693 notifications are used to report output of CLI commands, as well as
24694 diagnostics for other commands. Status notifications are used to
24695 report the progress of a long-running operation. Naturally, including
24696 this information in command response would mean no output is produced
24697 until the command is finished, which is undesirable.
24700 General notifications. Commands may have various side effects on
24701 the @value{GDBN} or target state beyond their official purpose. For example,
24702 a command may change the selected thread. Although such changes can
24703 be included in command response, using notification allows for more
24704 orthogonal frontend design.
24708 There's no guarantee that whenever an MI command reports an error,
24709 @value{GDBN} or the target are in any specific state, and especially,
24710 the state is not reverted to the state before the MI command was
24711 processed. Therefore, whenever an MI command results in an error,
24712 we recommend that the frontend refreshes all the information shown in
24713 the user interface.
24717 * Context management::
24718 * Asynchronous and non-stop modes::
24722 @node Context management
24723 @subsection Context management
24725 @subsubsection Threads and Frames
24727 In most cases when @value{GDBN} accesses the target, this access is
24728 done in context of a specific thread and frame (@pxref{Frames}).
24729 Often, even when accessing global data, the target requires that a thread
24730 be specified. The CLI interface maintains the selected thread and frame,
24731 and supplies them to target on each command. This is convenient,
24732 because a command line user would not want to specify that information
24733 explicitly on each command, and because user interacts with
24734 @value{GDBN} via a single terminal, so no confusion is possible as
24735 to what thread and frame are the current ones.
24737 In the case of MI, the concept of selected thread and frame is less
24738 useful. First, a frontend can easily remember this information
24739 itself. Second, a graphical frontend can have more than one window,
24740 each one used for debugging a different thread, and the frontend might
24741 want to access additional threads for internal purposes. This
24742 increases the risk that by relying on implicitly selected thread, the
24743 frontend may be operating on a wrong one. Therefore, each MI command
24744 should explicitly specify which thread and frame to operate on. To
24745 make it possible, each MI command accepts the @samp{--thread} and
24746 @samp{--frame} options, the value to each is @value{GDBN} identifier
24747 for thread and frame to operate on.
24749 Usually, each top-level window in a frontend allows the user to select
24750 a thread and a frame, and remembers the user selection for further
24751 operations. However, in some cases @value{GDBN} may suggest that the
24752 current thread be changed. For example, when stopping on a breakpoint
24753 it is reasonable to switch to the thread where breakpoint is hit. For
24754 another example, if the user issues the CLI @samp{thread} command via
24755 the frontend, it is desirable to change the frontend's selected thread to the
24756 one specified by user. @value{GDBN} communicates the suggestion to
24757 change current thread using the @samp{=thread-selected} notification.
24758 No such notification is available for the selected frame at the moment.
24760 Note that historically, MI shares the selected thread with CLI, so
24761 frontends used the @code{-thread-select} to execute commands in the
24762 right context. However, getting this to work right is cumbersome. The
24763 simplest way is for frontend to emit @code{-thread-select} command
24764 before every command. This doubles the number of commands that need
24765 to be sent. The alternative approach is to suppress @code{-thread-select}
24766 if the selected thread in @value{GDBN} is supposed to be identical to the
24767 thread the frontend wants to operate on. However, getting this
24768 optimization right can be tricky. In particular, if the frontend
24769 sends several commands to @value{GDBN}, and one of the commands changes the
24770 selected thread, then the behaviour of subsequent commands will
24771 change. So, a frontend should either wait for response from such
24772 problematic commands, or explicitly add @code{-thread-select} for
24773 all subsequent commands. No frontend is known to do this exactly
24774 right, so it is suggested to just always pass the @samp{--thread} and
24775 @samp{--frame} options.
24777 @subsubsection Language
24779 The execution of several commands depends on which language is selected.
24780 By default, the current language (@pxref{show language}) is used.
24781 But for commands known to be language-sensitive, it is recommended
24782 to use the @samp{--language} option. This option takes one argument,
24783 which is the name of the language to use while executing the command.
24787 -data-evaluate-expression --language c "sizeof (void*)"
24792 The valid language names are the same names accepted by the
24793 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
24794 @samp{local} or @samp{unknown}.
24796 @node Asynchronous and non-stop modes
24797 @subsection Asynchronous command execution and non-stop mode
24799 On some targets, @value{GDBN} is capable of processing MI commands
24800 even while the target is running. This is called @dfn{asynchronous
24801 command execution} (@pxref{Background Execution}). The frontend may
24802 specify a preferrence for asynchronous execution using the
24803 @code{-gdb-set mi-async 1} command, which should be emitted before
24804 either running the executable or attaching to the target. After the
24805 frontend has started the executable or attached to the target, it can
24806 find if asynchronous execution is enabled using the
24807 @code{-list-target-features} command.
24810 @item -gdb-set mi-async on
24811 @item -gdb-set mi-async off
24812 Set whether MI is in asynchronous mode.
24814 When @code{off}, which is the default, MI execution commands (e.g.,
24815 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
24816 for the program to stop before processing further commands.
24818 When @code{on}, MI execution commands are background execution
24819 commands (e.g., @code{-exec-continue} becomes the equivalent of the
24820 @code{c&} CLI command), and so @value{GDBN} is capable of processing
24821 MI commands even while the target is running.
24823 @item -gdb-show mi-async
24824 Show whether MI asynchronous mode is enabled.
24827 Note: In @value{GDBN} version 7.7 and earlier, this option was called
24828 @code{target-async} instead of @code{mi-async}, and it had the effect
24829 of both putting MI in asynchronous mode and making CLI background
24830 commands possible. CLI background commands are now always possible
24831 ``out of the box'' if the target supports them. The old spelling is
24832 kept as a deprecated alias for backwards compatibility.
24834 Even if @value{GDBN} can accept a command while target is running,
24835 many commands that access the target do not work when the target is
24836 running. Therefore, asynchronous command execution is most useful
24837 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24838 it is possible to examine the state of one thread, while other threads
24841 When a given thread is running, MI commands that try to access the
24842 target in the context of that thread may not work, or may work only on
24843 some targets. In particular, commands that try to operate on thread's
24844 stack will not work, on any target. Commands that read memory, or
24845 modify breakpoints, may work or not work, depending on the target. Note
24846 that even commands that operate on global state, such as @code{print},
24847 @code{set}, and breakpoint commands, still access the target in the
24848 context of a specific thread, so frontend should try to find a
24849 stopped thread and perform the operation on that thread (using the
24850 @samp{--thread} option).
24852 Which commands will work in the context of a running thread is
24853 highly target dependent. However, the two commands
24854 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24855 to find the state of a thread, will always work.
24857 @node Thread groups
24858 @subsection Thread groups
24859 @value{GDBN} may be used to debug several processes at the same time.
24860 On some platfroms, @value{GDBN} may support debugging of several
24861 hardware systems, each one having several cores with several different
24862 processes running on each core. This section describes the MI
24863 mechanism to support such debugging scenarios.
24865 The key observation is that regardless of the structure of the
24866 target, MI can have a global list of threads, because most commands that
24867 accept the @samp{--thread} option do not need to know what process that
24868 thread belongs to. Therefore, it is not necessary to introduce
24869 neither additional @samp{--process} option, nor an notion of the
24870 current process in the MI interface. The only strictly new feature
24871 that is required is the ability to find how the threads are grouped
24874 To allow the user to discover such grouping, and to support arbitrary
24875 hierarchy of machines/cores/processes, MI introduces the concept of a
24876 @dfn{thread group}. Thread group is a collection of threads and other
24877 thread groups. A thread group always has a string identifier, a type,
24878 and may have additional attributes specific to the type. A new
24879 command, @code{-list-thread-groups}, returns the list of top-level
24880 thread groups, which correspond to processes that @value{GDBN} is
24881 debugging at the moment. By passing an identifier of a thread group
24882 to the @code{-list-thread-groups} command, it is possible to obtain
24883 the members of specific thread group.
24885 To allow the user to easily discover processes, and other objects, he
24886 wishes to debug, a concept of @dfn{available thread group} is
24887 introduced. Available thread group is an thread group that
24888 @value{GDBN} is not debugging, but that can be attached to, using the
24889 @code{-target-attach} command. The list of available top-level thread
24890 groups can be obtained using @samp{-list-thread-groups --available}.
24891 In general, the content of a thread group may be only retrieved only
24892 after attaching to that thread group.
24894 Thread groups are related to inferiors (@pxref{Inferiors and
24895 Programs}). Each inferior corresponds to a thread group of a special
24896 type @samp{process}, and some additional operations are permitted on
24897 such thread groups.
24899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24900 @node GDB/MI Command Syntax
24901 @section @sc{gdb/mi} Command Syntax
24904 * GDB/MI Input Syntax::
24905 * GDB/MI Output Syntax::
24908 @node GDB/MI Input Syntax
24909 @subsection @sc{gdb/mi} Input Syntax
24911 @cindex input syntax for @sc{gdb/mi}
24912 @cindex @sc{gdb/mi}, input syntax
24914 @item @var{command} @expansion{}
24915 @code{@var{cli-command} | @var{mi-command}}
24917 @item @var{cli-command} @expansion{}
24918 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24919 @var{cli-command} is any existing @value{GDBN} CLI command.
24921 @item @var{mi-command} @expansion{}
24922 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24923 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24925 @item @var{token} @expansion{}
24926 "any sequence of digits"
24928 @item @var{option} @expansion{}
24929 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24931 @item @var{parameter} @expansion{}
24932 @code{@var{non-blank-sequence} | @var{c-string}}
24934 @item @var{operation} @expansion{}
24935 @emph{any of the operations described in this chapter}
24937 @item @var{non-blank-sequence} @expansion{}
24938 @emph{anything, provided it doesn't contain special characters such as
24939 "-", @var{nl}, """ and of course " "}
24941 @item @var{c-string} @expansion{}
24942 @code{""" @var{seven-bit-iso-c-string-content} """}
24944 @item @var{nl} @expansion{}
24953 The CLI commands are still handled by the @sc{mi} interpreter; their
24954 output is described below.
24957 The @code{@var{token}}, when present, is passed back when the command
24961 Some @sc{mi} commands accept optional arguments as part of the parameter
24962 list. Each option is identified by a leading @samp{-} (dash) and may be
24963 followed by an optional argument parameter. Options occur first in the
24964 parameter list and can be delimited from normal parameters using
24965 @samp{--} (this is useful when some parameters begin with a dash).
24972 We want easy access to the existing CLI syntax (for debugging).
24975 We want it to be easy to spot a @sc{mi} operation.
24978 @node GDB/MI Output Syntax
24979 @subsection @sc{gdb/mi} Output Syntax
24981 @cindex output syntax of @sc{gdb/mi}
24982 @cindex @sc{gdb/mi}, output syntax
24983 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24984 followed, optionally, by a single result record. This result record
24985 is for the most recent command. The sequence of output records is
24986 terminated by @samp{(gdb)}.
24988 If an input command was prefixed with a @code{@var{token}} then the
24989 corresponding output for that command will also be prefixed by that same
24993 @item @var{output} @expansion{}
24994 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24996 @item @var{result-record} @expansion{}
24997 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24999 @item @var{out-of-band-record} @expansion{}
25000 @code{@var{async-record} | @var{stream-record}}
25002 @item @var{async-record} @expansion{}
25003 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25005 @item @var{exec-async-output} @expansion{}
25006 @code{[ @var{token} ] "*" @var{async-output nl}}
25008 @item @var{status-async-output} @expansion{}
25009 @code{[ @var{token} ] "+" @var{async-output nl}}
25011 @item @var{notify-async-output} @expansion{}
25012 @code{[ @var{token} ] "=" @var{async-output nl}}
25014 @item @var{async-output} @expansion{}
25015 @code{@var{async-class} ( "," @var{result} )*}
25017 @item @var{result-class} @expansion{}
25018 @code{"done" | "running" | "connected" | "error" | "exit"}
25020 @item @var{async-class} @expansion{}
25021 @code{"stopped" | @var{others}} (where @var{others} will be added
25022 depending on the needs---this is still in development).
25024 @item @var{result} @expansion{}
25025 @code{ @var{variable} "=" @var{value}}
25027 @item @var{variable} @expansion{}
25028 @code{ @var{string} }
25030 @item @var{value} @expansion{}
25031 @code{ @var{const} | @var{tuple} | @var{list} }
25033 @item @var{const} @expansion{}
25034 @code{@var{c-string}}
25036 @item @var{tuple} @expansion{}
25037 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25039 @item @var{list} @expansion{}
25040 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25041 @var{result} ( "," @var{result} )* "]" }
25043 @item @var{stream-record} @expansion{}
25044 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25046 @item @var{console-stream-output} @expansion{}
25047 @code{"~" @var{c-string nl}}
25049 @item @var{target-stream-output} @expansion{}
25050 @code{"@@" @var{c-string nl}}
25052 @item @var{log-stream-output} @expansion{}
25053 @code{"&" @var{c-string nl}}
25055 @item @var{nl} @expansion{}
25058 @item @var{token} @expansion{}
25059 @emph{any sequence of digits}.
25067 All output sequences end in a single line containing a period.
25070 The @code{@var{token}} is from the corresponding request. Note that
25071 for all async output, while the token is allowed by the grammar and
25072 may be output by future versions of @value{GDBN} for select async
25073 output messages, it is generally omitted. Frontends should treat
25074 all async output as reporting general changes in the state of the
25075 target and there should be no need to associate async output to any
25079 @cindex status output in @sc{gdb/mi}
25080 @var{status-async-output} contains on-going status information about the
25081 progress of a slow operation. It can be discarded. All status output is
25082 prefixed by @samp{+}.
25085 @cindex async output in @sc{gdb/mi}
25086 @var{exec-async-output} contains asynchronous state change on the target
25087 (stopped, started, disappeared). All async output is prefixed by
25091 @cindex notify output in @sc{gdb/mi}
25092 @var{notify-async-output} contains supplementary information that the
25093 client should handle (e.g., a new breakpoint information). All notify
25094 output is prefixed by @samp{=}.
25097 @cindex console output in @sc{gdb/mi}
25098 @var{console-stream-output} is output that should be displayed as is in the
25099 console. It is the textual response to a CLI command. All the console
25100 output is prefixed by @samp{~}.
25103 @cindex target output in @sc{gdb/mi}
25104 @var{target-stream-output} is the output produced by the target program.
25105 All the target output is prefixed by @samp{@@}.
25108 @cindex log output in @sc{gdb/mi}
25109 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25110 instance messages that should be displayed as part of an error log. All
25111 the log output is prefixed by @samp{&}.
25114 @cindex list output in @sc{gdb/mi}
25115 New @sc{gdb/mi} commands should only output @var{lists} containing
25121 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25122 details about the various output records.
25124 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25125 @node GDB/MI Compatibility with CLI
25126 @section @sc{gdb/mi} Compatibility with CLI
25128 @cindex compatibility, @sc{gdb/mi} and CLI
25129 @cindex @sc{gdb/mi}, compatibility with CLI
25131 For the developers convenience CLI commands can be entered directly,
25132 but there may be some unexpected behaviour. For example, commands
25133 that query the user will behave as if the user replied yes, breakpoint
25134 command lists are not executed and some CLI commands, such as
25135 @code{if}, @code{when} and @code{define}, prompt for further input with
25136 @samp{>}, which is not valid MI output.
25138 This feature may be removed at some stage in the future and it is
25139 recommended that front ends use the @code{-interpreter-exec} command
25140 (@pxref{-interpreter-exec}).
25142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25143 @node GDB/MI Development and Front Ends
25144 @section @sc{gdb/mi} Development and Front Ends
25145 @cindex @sc{gdb/mi} development
25147 The application which takes the MI output and presents the state of the
25148 program being debugged to the user is called a @dfn{front end}.
25150 Although @sc{gdb/mi} is still incomplete, it is currently being used
25151 by a variety of front ends to @value{GDBN}. This makes it difficult
25152 to introduce new functionality without breaking existing usage. This
25153 section tries to minimize the problems by describing how the protocol
25156 Some changes in MI need not break a carefully designed front end, and
25157 for these the MI version will remain unchanged. The following is a
25158 list of changes that may occur within one level, so front ends should
25159 parse MI output in a way that can handle them:
25163 New MI commands may be added.
25166 New fields may be added to the output of any MI command.
25169 The range of values for fields with specified values, e.g.,
25170 @code{in_scope} (@pxref{-var-update}) may be extended.
25172 @c The format of field's content e.g type prefix, may change so parse it
25173 @c at your own risk. Yes, in general?
25175 @c The order of fields may change? Shouldn't really matter but it might
25176 @c resolve inconsistencies.
25179 If the changes are likely to break front ends, the MI version level
25180 will be increased by one. This will allow the front end to parse the
25181 output according to the MI version. Apart from mi0, new versions of
25182 @value{GDBN} will not support old versions of MI and it will be the
25183 responsibility of the front end to work with the new one.
25185 @c Starting with mi3, add a new command -mi-version that prints the MI
25188 The best way to avoid unexpected changes in MI that might break your front
25189 end is to make your project known to @value{GDBN} developers and
25190 follow development on @email{gdb@@sourceware.org} and
25191 @email{gdb-patches@@sourceware.org}.
25192 @cindex mailing lists
25194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25195 @node GDB/MI Output Records
25196 @section @sc{gdb/mi} Output Records
25199 * GDB/MI Result Records::
25200 * GDB/MI Stream Records::
25201 * GDB/MI Async Records::
25202 * GDB/MI Breakpoint Information::
25203 * GDB/MI Frame Information::
25204 * GDB/MI Thread Information::
25205 * GDB/MI Ada Exception Information::
25208 @node GDB/MI Result Records
25209 @subsection @sc{gdb/mi} Result Records
25211 @cindex result records in @sc{gdb/mi}
25212 @cindex @sc{gdb/mi}, result records
25213 In addition to a number of out-of-band notifications, the response to a
25214 @sc{gdb/mi} command includes one of the following result indications:
25218 @item "^done" [ "," @var{results} ]
25219 The synchronous operation was successful, @code{@var{results}} are the return
25224 This result record is equivalent to @samp{^done}. Historically, it
25225 was output instead of @samp{^done} if the command has resumed the
25226 target. This behaviour is maintained for backward compatibility, but
25227 all frontends should treat @samp{^done} and @samp{^running}
25228 identically and rely on the @samp{*running} output record to determine
25229 which threads are resumed.
25233 @value{GDBN} has connected to a remote target.
25235 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25237 The operation failed. The @code{msg=@var{c-string}} variable contains
25238 the corresponding error message.
25240 If present, the @code{code=@var{c-string}} variable provides an error
25241 code on which consumers can rely on to detect the corresponding
25242 error condition. At present, only one error code is defined:
25245 @item "undefined-command"
25246 Indicates that the command causing the error does not exist.
25251 @value{GDBN} has terminated.
25255 @node GDB/MI Stream Records
25256 @subsection @sc{gdb/mi} Stream Records
25258 @cindex @sc{gdb/mi}, stream records
25259 @cindex stream records in @sc{gdb/mi}
25260 @value{GDBN} internally maintains a number of output streams: the console, the
25261 target, and the log. The output intended for each of these streams is
25262 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25264 Each stream record begins with a unique @dfn{prefix character} which
25265 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25266 Syntax}). In addition to the prefix, each stream record contains a
25267 @code{@var{string-output}}. This is either raw text (with an implicit new
25268 line) or a quoted C string (which does not contain an implicit newline).
25271 @item "~" @var{string-output}
25272 The console output stream contains text that should be displayed in the
25273 CLI console window. It contains the textual responses to CLI commands.
25275 @item "@@" @var{string-output}
25276 The target output stream contains any textual output from the running
25277 target. This is only present when GDB's event loop is truly
25278 asynchronous, which is currently only the case for remote targets.
25280 @item "&" @var{string-output}
25281 The log stream contains debugging messages being produced by @value{GDBN}'s
25285 @node GDB/MI Async Records
25286 @subsection @sc{gdb/mi} Async Records
25288 @cindex async records in @sc{gdb/mi}
25289 @cindex @sc{gdb/mi}, async records
25290 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25291 additional changes that have occurred. Those changes can either be a
25292 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25293 target activity (e.g., target stopped).
25295 The following is the list of possible async records:
25299 @item *running,thread-id="@var{thread}"
25300 The target is now running. The @var{thread} field tells which
25301 specific thread is now running, and can be @samp{all} if all threads
25302 are running. The frontend should assume that no interaction with a
25303 running thread is possible after this notification is produced.
25304 The frontend should not assume that this notification is output
25305 only once for any command. @value{GDBN} may emit this notification
25306 several times, either for different threads, because it cannot resume
25307 all threads together, or even for a single thread, if the thread must
25308 be stepped though some code before letting it run freely.
25310 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25311 The target has stopped. The @var{reason} field can have one of the
25315 @item breakpoint-hit
25316 A breakpoint was reached.
25317 @item watchpoint-trigger
25318 A watchpoint was triggered.
25319 @item read-watchpoint-trigger
25320 A read watchpoint was triggered.
25321 @item access-watchpoint-trigger
25322 An access watchpoint was triggered.
25323 @item function-finished
25324 An -exec-finish or similar CLI command was accomplished.
25325 @item location-reached
25326 An -exec-until or similar CLI command was accomplished.
25327 @item watchpoint-scope
25328 A watchpoint has gone out of scope.
25329 @item end-stepping-range
25330 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25331 similar CLI command was accomplished.
25332 @item exited-signalled
25333 The inferior exited because of a signal.
25335 The inferior exited.
25336 @item exited-normally
25337 The inferior exited normally.
25338 @item signal-received
25339 A signal was received by the inferior.
25341 The inferior has stopped due to a library being loaded or unloaded.
25342 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25343 set or when a @code{catch load} or @code{catch unload} catchpoint is
25344 in use (@pxref{Set Catchpoints}).
25346 The inferior has forked. This is reported when @code{catch fork}
25347 (@pxref{Set Catchpoints}) has been used.
25349 The inferior has vforked. This is reported in when @code{catch vfork}
25350 (@pxref{Set Catchpoints}) has been used.
25351 @item syscall-entry
25352 The inferior entered a system call. This is reported when @code{catch
25353 syscall} (@pxref{Set Catchpoints}) has been used.
25354 @item syscall-entry
25355 The inferior returned from a system call. This is reported when
25356 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25358 The inferior called @code{exec}. This is reported when @code{catch exec}
25359 (@pxref{Set Catchpoints}) has been used.
25362 The @var{id} field identifies the thread that directly caused the stop
25363 -- for example by hitting a breakpoint. Depending on whether all-stop
25364 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25365 stop all threads, or only the thread that directly triggered the stop.
25366 If all threads are stopped, the @var{stopped} field will have the
25367 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25368 field will be a list of thread identifiers. Presently, this list will
25369 always include a single thread, but frontend should be prepared to see
25370 several threads in the list. The @var{core} field reports the
25371 processor core on which the stop event has happened. This field may be absent
25372 if such information is not available.
25374 @item =thread-group-added,id="@var{id}"
25375 @itemx =thread-group-removed,id="@var{id}"
25376 A thread group was either added or removed. The @var{id} field
25377 contains the @value{GDBN} identifier of the thread group. When a thread
25378 group is added, it generally might not be associated with a running
25379 process. When a thread group is removed, its id becomes invalid and
25380 cannot be used in any way.
25382 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25383 A thread group became associated with a running program,
25384 either because the program was just started or the thread group
25385 was attached to a program. The @var{id} field contains the
25386 @value{GDBN} identifier of the thread group. The @var{pid} field
25387 contains process identifier, specific to the operating system.
25389 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25390 A thread group is no longer associated with a running program,
25391 either because the program has exited, or because it was detached
25392 from. The @var{id} field contains the @value{GDBN} identifier of the
25393 thread group. The @var{code} field is the exit code of the inferior; it exists
25394 only when the inferior exited with some code.
25396 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25397 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25398 A thread either was created, or has exited. The @var{id} field
25399 contains the @value{GDBN} identifier of the thread. The @var{gid}
25400 field identifies the thread group this thread belongs to.
25402 @item =thread-selected,id="@var{id}"
25403 Informs that the selected thread was changed as result of the last
25404 command. This notification is not emitted as result of @code{-thread-select}
25405 command but is emitted whenever an MI command that is not documented
25406 to change the selected thread actually changes it. In particular,
25407 invoking, directly or indirectly (via user-defined command), the CLI
25408 @code{thread} command, will generate this notification.
25410 We suggest that in response to this notification, front ends
25411 highlight the selected thread and cause subsequent commands to apply to
25414 @item =library-loaded,...
25415 Reports that a new library file was loaded by the program. This
25416 notification has 4 fields---@var{id}, @var{target-name},
25417 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25418 opaque identifier of the library. For remote debugging case,
25419 @var{target-name} and @var{host-name} fields give the name of the
25420 library file on the target, and on the host respectively. For native
25421 debugging, both those fields have the same value. The
25422 @var{symbols-loaded} field is emitted only for backward compatibility
25423 and should not be relied on to convey any useful information. The
25424 @var{thread-group} field, if present, specifies the id of the thread
25425 group in whose context the library was loaded. If the field is
25426 absent, it means the library was loaded in the context of all present
25429 @item =library-unloaded,...
25430 Reports that a library was unloaded by the program. This notification
25431 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25432 the same meaning as for the @code{=library-loaded} notification.
25433 The @var{thread-group} field, if present, specifies the id of the
25434 thread group in whose context the library was unloaded. If the field is
25435 absent, it means the library was unloaded in the context of all present
25438 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
25439 @itemx =traceframe-changed,end
25440 Reports that the trace frame was changed and its new number is
25441 @var{tfnum}. The number of the tracepoint associated with this trace
25442 frame is @var{tpnum}.
25444 @item =tsv-created,name=@var{name},initial=@var{initial}
25445 Reports that the new trace state variable @var{name} is created with
25446 initial value @var{initial}.
25448 @item =tsv-deleted,name=@var{name}
25449 @itemx =tsv-deleted
25450 Reports that the trace state variable @var{name} is deleted or all
25451 trace state variables are deleted.
25453 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
25454 Reports that the trace state variable @var{name} is modified with
25455 the initial value @var{initial}. The current value @var{current} of
25456 trace state variable is optional and is reported if the current
25457 value of trace state variable is known.
25459 @item =breakpoint-created,bkpt=@{...@}
25460 @itemx =breakpoint-modified,bkpt=@{...@}
25461 @itemx =breakpoint-deleted,id=@var{number}
25462 Reports that a breakpoint was created, modified, or deleted,
25463 respectively. Only user-visible breakpoints are reported to the MI
25466 The @var{bkpt} argument is of the same form as returned by the various
25467 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
25468 @var{number} is the ordinal number of the breakpoint.
25470 Note that if a breakpoint is emitted in the result record of a
25471 command, then it will not also be emitted in an async record.
25473 @item =record-started,thread-group="@var{id}"
25474 @itemx =record-stopped,thread-group="@var{id}"
25475 Execution log recording was either started or stopped on an
25476 inferior. The @var{id} is the @value{GDBN} identifier of the thread
25477 group corresponding to the affected inferior.
25479 @item =cmd-param-changed,param=@var{param},value=@var{value}
25480 Reports that a parameter of the command @code{set @var{param}} is
25481 changed to @var{value}. In the multi-word @code{set} command,
25482 the @var{param} is the whole parameter list to @code{set} command.
25483 For example, In command @code{set check type on}, @var{param}
25484 is @code{check type} and @var{value} is @code{on}.
25486 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
25487 Reports that bytes from @var{addr} to @var{data} + @var{len} were
25488 written in an inferior. The @var{id} is the identifier of the
25489 thread group corresponding to the affected inferior. The optional
25490 @code{type="code"} part is reported if the memory written to holds
25494 @node GDB/MI Breakpoint Information
25495 @subsection @sc{gdb/mi} Breakpoint Information
25497 When @value{GDBN} reports information about a breakpoint, a
25498 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
25503 The breakpoint number. For a breakpoint that represents one location
25504 of a multi-location breakpoint, this will be a dotted pair, like
25508 The type of the breakpoint. For ordinary breakpoints this will be
25509 @samp{breakpoint}, but many values are possible.
25512 If the type of the breakpoint is @samp{catchpoint}, then this
25513 indicates the exact type of catchpoint.
25516 This is the breakpoint disposition---either @samp{del}, meaning that
25517 the breakpoint will be deleted at the next stop, or @samp{keep},
25518 meaning that the breakpoint will not be deleted.
25521 This indicates whether the breakpoint is enabled, in which case the
25522 value is @samp{y}, or disabled, in which case the value is @samp{n}.
25523 Note that this is not the same as the field @code{enable}.
25526 The address of the breakpoint. This may be a hexidecimal number,
25527 giving the address; or the string @samp{<PENDING>}, for a pending
25528 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
25529 multiple locations. This field will not be present if no address can
25530 be determined. For example, a watchpoint does not have an address.
25533 If known, the function in which the breakpoint appears.
25534 If not known, this field is not present.
25537 The name of the source file which contains this function, if known.
25538 If not known, this field is not present.
25541 The full file name of the source file which contains this function, if
25542 known. If not known, this field is not present.
25545 The line number at which this breakpoint appears, if known.
25546 If not known, this field is not present.
25549 If the source file is not known, this field may be provided. If
25550 provided, this holds the address of the breakpoint, possibly followed
25554 If this breakpoint is pending, this field is present and holds the
25555 text used to set the breakpoint, as entered by the user.
25558 Where this breakpoint's condition is evaluated, either @samp{host} or
25562 If this is a thread-specific breakpoint, then this identifies the
25563 thread in which the breakpoint can trigger.
25566 If this breakpoint is restricted to a particular Ada task, then this
25567 field will hold the task identifier.
25570 If the breakpoint is conditional, this is the condition expression.
25573 The ignore count of the breakpoint.
25576 The enable count of the breakpoint.
25578 @item traceframe-usage
25581 @item static-tracepoint-marker-string-id
25582 For a static tracepoint, the name of the static tracepoint marker.
25585 For a masked watchpoint, this is the mask.
25588 A tracepoint's pass count.
25590 @item original-location
25591 The location of the breakpoint as originally specified by the user.
25592 This field is optional.
25595 The number of times the breakpoint has been hit.
25598 This field is only given for tracepoints. This is either @samp{y},
25599 meaning that the tracepoint is installed, or @samp{n}, meaning that it
25603 Some extra data, the exact contents of which are type-dependent.
25607 For example, here is what the output of @code{-break-insert}
25608 (@pxref{GDB/MI Breakpoint Commands}) might be:
25611 -> -break-insert main
25612 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25613 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25614 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25619 @node GDB/MI Frame Information
25620 @subsection @sc{gdb/mi} Frame Information
25622 Response from many MI commands includes an information about stack
25623 frame. This information is a tuple that may have the following
25628 The level of the stack frame. The innermost frame has the level of
25629 zero. This field is always present.
25632 The name of the function corresponding to the frame. This field may
25633 be absent if @value{GDBN} is unable to determine the function name.
25636 The code address for the frame. This field is always present.
25639 The name of the source files that correspond to the frame's code
25640 address. This field may be absent.
25643 The source line corresponding to the frames' code address. This field
25647 The name of the binary file (either executable or shared library) the
25648 corresponds to the frame's code address. This field may be absent.
25652 @node GDB/MI Thread Information
25653 @subsection @sc{gdb/mi} Thread Information
25655 Whenever @value{GDBN} has to report an information about a thread, it
25656 uses a tuple with the following fields:
25660 The numeric id assigned to the thread by @value{GDBN}. This field is
25664 Target-specific string identifying the thread. This field is always present.
25667 Additional information about the thread provided by the target.
25668 It is supposed to be human-readable and not interpreted by the
25669 frontend. This field is optional.
25672 Either @samp{stopped} or @samp{running}, depending on whether the
25673 thread is presently running. This field is always present.
25676 The value of this field is an integer number of the processor core the
25677 thread was last seen on. This field is optional.
25680 @node GDB/MI Ada Exception Information
25681 @subsection @sc{gdb/mi} Ada Exception Information
25683 Whenever a @code{*stopped} record is emitted because the program
25684 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25685 @value{GDBN} provides the name of the exception that was raised via
25686 the @code{exception-name} field.
25688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25689 @node GDB/MI Simple Examples
25690 @section Simple Examples of @sc{gdb/mi} Interaction
25691 @cindex @sc{gdb/mi}, simple examples
25693 This subsection presents several simple examples of interaction using
25694 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25695 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25696 the output received from @sc{gdb/mi}.
25698 Note the line breaks shown in the examples are here only for
25699 readability, they don't appear in the real output.
25701 @subheading Setting a Breakpoint
25703 Setting a breakpoint generates synchronous output which contains detailed
25704 information of the breakpoint.
25707 -> -break-insert main
25708 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25709 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25710 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
25715 @subheading Program Execution
25717 Program execution generates asynchronous records and MI gives the
25718 reason that execution stopped.
25724 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25725 frame=@{addr="0x08048564",func="main",
25726 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25727 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25732 <- *stopped,reason="exited-normally"
25736 @subheading Quitting @value{GDBN}
25738 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25746 Please note that @samp{^exit} is printed immediately, but it might
25747 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25748 performs necessary cleanups, including killing programs being debugged
25749 or disconnecting from debug hardware, so the frontend should wait till
25750 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25751 fails to exit in reasonable time.
25753 @subheading A Bad Command
25755 Here's what happens if you pass a non-existent command:
25759 <- ^error,msg="Undefined MI command: rubbish"
25764 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25765 @node GDB/MI Command Description Format
25766 @section @sc{gdb/mi} Command Description Format
25768 The remaining sections describe blocks of commands. Each block of
25769 commands is laid out in a fashion similar to this section.
25771 @subheading Motivation
25773 The motivation for this collection of commands.
25775 @subheading Introduction
25777 A brief introduction to this collection of commands as a whole.
25779 @subheading Commands
25781 For each command in the block, the following is described:
25783 @subsubheading Synopsis
25786 -command @var{args}@dots{}
25789 @subsubheading Result
25791 @subsubheading @value{GDBN} Command
25793 The corresponding @value{GDBN} CLI command(s), if any.
25795 @subsubheading Example
25797 Example(s) formatted for readability. Some of the described commands have
25798 not been implemented yet and these are labeled N.A.@: (not available).
25801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25802 @node GDB/MI Breakpoint Commands
25803 @section @sc{gdb/mi} Breakpoint Commands
25805 @cindex breakpoint commands for @sc{gdb/mi}
25806 @cindex @sc{gdb/mi}, breakpoint commands
25807 This section documents @sc{gdb/mi} commands for manipulating
25810 @subheading The @code{-break-after} Command
25811 @findex -break-after
25813 @subsubheading Synopsis
25816 -break-after @var{number} @var{count}
25819 The breakpoint number @var{number} is not in effect until it has been
25820 hit @var{count} times. To see how this is reflected in the output of
25821 the @samp{-break-list} command, see the description of the
25822 @samp{-break-list} command below.
25824 @subsubheading @value{GDBN} Command
25826 The corresponding @value{GDBN} command is @samp{ignore}.
25828 @subsubheading Example
25833 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25834 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25835 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25843 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25844 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25845 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25846 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25847 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25848 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25849 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25850 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25851 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25852 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
25857 @subheading The @code{-break-catch} Command
25858 @findex -break-catch
25861 @subheading The @code{-break-commands} Command
25862 @findex -break-commands
25864 @subsubheading Synopsis
25867 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25870 Specifies the CLI commands that should be executed when breakpoint
25871 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25872 are the commands. If no command is specified, any previously-set
25873 commands are cleared. @xref{Break Commands}. Typical use of this
25874 functionality is tracing a program, that is, printing of values of
25875 some variables whenever breakpoint is hit and then continuing.
25877 @subsubheading @value{GDBN} Command
25879 The corresponding @value{GDBN} command is @samp{commands}.
25881 @subsubheading Example
25886 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25887 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25888 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
25891 -break-commands 1 "print v" "continue"
25896 @subheading The @code{-break-condition} Command
25897 @findex -break-condition
25899 @subsubheading Synopsis
25902 -break-condition @var{number} @var{expr}
25905 Breakpoint @var{number} will stop the program only if the condition in
25906 @var{expr} is true. The condition becomes part of the
25907 @samp{-break-list} output (see the description of the @samp{-break-list}
25910 @subsubheading @value{GDBN} Command
25912 The corresponding @value{GDBN} command is @samp{condition}.
25914 @subsubheading Example
25918 -break-condition 1 1
25922 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25929 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25930 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25931 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
25935 @subheading The @code{-break-delete} Command
25936 @findex -break-delete
25938 @subsubheading Synopsis
25941 -break-delete ( @var{breakpoint} )+
25944 Delete the breakpoint(s) whose number(s) are specified in the argument
25945 list. This is obviously reflected in the breakpoint list.
25947 @subsubheading @value{GDBN} Command
25949 The corresponding @value{GDBN} command is @samp{delete}.
25951 @subsubheading Example
25959 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25960 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25961 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25962 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25963 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25964 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25965 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25970 @subheading The @code{-break-disable} Command
25971 @findex -break-disable
25973 @subsubheading Synopsis
25976 -break-disable ( @var{breakpoint} )+
25979 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25980 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25982 @subsubheading @value{GDBN} Command
25984 The corresponding @value{GDBN} command is @samp{disable}.
25986 @subsubheading Example
25994 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25995 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25996 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25997 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25998 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25999 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26000 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26001 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26002 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26003 line="5",thread-groups=["i1"],times="0"@}]@}
26007 @subheading The @code{-break-enable} Command
26008 @findex -break-enable
26010 @subsubheading Synopsis
26013 -break-enable ( @var{breakpoint} )+
26016 Enable (previously disabled) @var{breakpoint}(s).
26018 @subsubheading @value{GDBN} Command
26020 The corresponding @value{GDBN} command is @samp{enable}.
26022 @subsubheading Example
26030 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26031 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26032 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26033 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26034 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26035 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26036 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26037 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26038 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26039 line="5",thread-groups=["i1"],times="0"@}]@}
26043 @subheading The @code{-break-info} Command
26044 @findex -break-info
26046 @subsubheading Synopsis
26049 -break-info @var{breakpoint}
26053 Get information about a single breakpoint.
26055 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26056 Information}, for details on the format of each breakpoint in the
26059 @subsubheading @value{GDBN} Command
26061 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26063 @subsubheading Example
26066 @subheading The @code{-break-insert} Command
26067 @findex -break-insert
26069 @subsubheading Synopsis
26072 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26073 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26074 [ -p @var{thread-id} ] [ @var{location} ]
26078 If specified, @var{location}, can be one of:
26085 @item filename:linenum
26086 @item filename:function
26090 The possible optional parameters of this command are:
26094 Insert a temporary breakpoint.
26096 Insert a hardware breakpoint.
26098 If @var{location} cannot be parsed (for example if it
26099 refers to unknown files or functions), create a pending
26100 breakpoint. Without this flag, @value{GDBN} will report
26101 an error, and won't create a breakpoint, if @var{location}
26104 Create a disabled breakpoint.
26106 Create a tracepoint. @xref{Tracepoints}. When this parameter
26107 is used together with @samp{-h}, a fast tracepoint is created.
26108 @item -c @var{condition}
26109 Make the breakpoint conditional on @var{condition}.
26110 @item -i @var{ignore-count}
26111 Initialize the @var{ignore-count}.
26112 @item -p @var{thread-id}
26113 Restrict the breakpoint to the specified @var{thread-id}.
26116 @subsubheading Result
26118 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26119 resulting breakpoint.
26121 Note: this format is open to change.
26122 @c An out-of-band breakpoint instead of part of the result?
26124 @subsubheading @value{GDBN} Command
26126 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26127 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26129 @subsubheading Example
26134 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26135 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26138 -break-insert -t foo
26139 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26140 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26144 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26145 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26146 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26147 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26148 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26149 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26150 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26151 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26152 addr="0x0001072c", func="main",file="recursive2.c",
26153 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26155 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26156 addr="0x00010774",func="foo",file="recursive2.c",
26157 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26160 @c -break-insert -r foo.*
26161 @c ~int foo(int, int);
26162 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26163 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26168 @subheading The @code{-dprintf-insert} Command
26169 @findex -dprintf-insert
26171 @subsubheading Synopsis
26174 -dprintf-insert [ -t ] [ -f ] [ -d ]
26175 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26176 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26181 If specified, @var{location}, can be one of:
26184 @item @var{function}
26187 @c @item @var{linenum}
26188 @item @var{filename}:@var{linenum}
26189 @item @var{filename}:function
26190 @item *@var{address}
26193 The possible optional parameters of this command are:
26197 Insert a temporary breakpoint.
26199 If @var{location} cannot be parsed (for example, if it
26200 refers to unknown files or functions), create a pending
26201 breakpoint. Without this flag, @value{GDBN} will report
26202 an error, and won't create a breakpoint, if @var{location}
26205 Create a disabled breakpoint.
26206 @item -c @var{condition}
26207 Make the breakpoint conditional on @var{condition}.
26208 @item -i @var{ignore-count}
26209 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26210 to @var{ignore-count}.
26211 @item -p @var{thread-id}
26212 Restrict the breakpoint to the specified @var{thread-id}.
26215 @subsubheading Result
26217 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26218 resulting breakpoint.
26220 @c An out-of-band breakpoint instead of part of the result?
26222 @subsubheading @value{GDBN} Command
26224 The corresponding @value{GDBN} command is @samp{dprintf}.
26226 @subsubheading Example
26230 4-dprintf-insert foo "At foo entry\n"
26231 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26232 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26233 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26234 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26235 original-location="foo"@}
26237 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26238 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26239 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26240 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26241 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26242 original-location="mi-dprintf.c:26"@}
26246 @subheading The @code{-break-list} Command
26247 @findex -break-list
26249 @subsubheading Synopsis
26255 Displays the list of inserted breakpoints, showing the following fields:
26259 number of the breakpoint
26261 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26263 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26266 is the breakpoint enabled or no: @samp{y} or @samp{n}
26268 memory location at which the breakpoint is set
26270 logical location of the breakpoint, expressed by function name, file
26272 @item Thread-groups
26273 list of thread groups to which this breakpoint applies
26275 number of times the breakpoint has been hit
26278 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26279 @code{body} field is an empty list.
26281 @subsubheading @value{GDBN} Command
26283 The corresponding @value{GDBN} command is @samp{info break}.
26285 @subsubheading Example
26290 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26291 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26292 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26293 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26294 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26295 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26296 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26297 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26298 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26300 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26301 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26302 line="13",thread-groups=["i1"],times="0"@}]@}
26306 Here's an example of the result when there are no breakpoints:
26311 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26312 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26313 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26314 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26315 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26316 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26317 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26322 @subheading The @code{-break-passcount} Command
26323 @findex -break-passcount
26325 @subsubheading Synopsis
26328 -break-passcount @var{tracepoint-number} @var{passcount}
26331 Set the passcount for tracepoint @var{tracepoint-number} to
26332 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26333 is not a tracepoint, error is emitted. This corresponds to CLI
26334 command @samp{passcount}.
26336 @subheading The @code{-break-watch} Command
26337 @findex -break-watch
26339 @subsubheading Synopsis
26342 -break-watch [ -a | -r ]
26345 Create a watchpoint. With the @samp{-a} option it will create an
26346 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26347 read from or on a write to the memory location. With the @samp{-r}
26348 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26349 trigger only when the memory location is accessed for reading. Without
26350 either of the options, the watchpoint created is a regular watchpoint,
26351 i.e., it will trigger when the memory location is accessed for writing.
26352 @xref{Set Watchpoints, , Setting Watchpoints}.
26354 Note that @samp{-break-list} will report a single list of watchpoints and
26355 breakpoints inserted.
26357 @subsubheading @value{GDBN} Command
26359 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26362 @subsubheading Example
26364 Setting a watchpoint on a variable in the @code{main} function:
26369 ^done,wpt=@{number="2",exp="x"@}
26374 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26375 value=@{old="-268439212",new="55"@},
26376 frame=@{func="main",args=[],file="recursive2.c",
26377 fullname="/home/foo/bar/recursive2.c",line="5"@}
26381 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26382 the program execution twice: first for the variable changing value, then
26383 for the watchpoint going out of scope.
26388 ^done,wpt=@{number="5",exp="C"@}
26393 *stopped,reason="watchpoint-trigger",
26394 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26395 frame=@{func="callee4",args=[],
26396 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26397 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26402 *stopped,reason="watchpoint-scope",wpnum="5",
26403 frame=@{func="callee3",args=[@{name="strarg",
26404 value="0x11940 \"A string argument.\""@}],
26405 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26406 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26410 Listing breakpoints and watchpoints, at different points in the program
26411 execution. Note that once the watchpoint goes out of scope, it is
26417 ^done,wpt=@{number="2",exp="C"@}
26420 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26421 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26422 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26423 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26424 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26425 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26426 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26427 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26428 addr="0x00010734",func="callee4",
26429 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26430 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
26432 bkpt=@{number="2",type="watchpoint",disp="keep",
26433 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
26438 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26439 value=@{old="-276895068",new="3"@},
26440 frame=@{func="callee4",args=[],
26441 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26442 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26445 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26446 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26447 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26448 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26449 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26450 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26451 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26452 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26453 addr="0x00010734",func="callee4",
26454 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26455 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
26457 bkpt=@{number="2",type="watchpoint",disp="keep",
26458 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
26462 ^done,reason="watchpoint-scope",wpnum="2",
26463 frame=@{func="callee3",args=[@{name="strarg",
26464 value="0x11940 \"A string argument.\""@}],
26465 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26466 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26469 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26470 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26471 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26472 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26473 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26474 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26475 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26476 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26477 addr="0x00010734",func="callee4",
26478 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26479 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26480 thread-groups=["i1"],times="1"@}]@}
26485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26486 @node GDB/MI Catchpoint Commands
26487 @section @sc{gdb/mi} Catchpoint Commands
26489 This section documents @sc{gdb/mi} commands for manipulating
26493 * Shared Library GDB/MI Catchpoint Commands::
26494 * Ada Exception GDB/MI Catchpoint Commands::
26497 @node Shared Library GDB/MI Catchpoint Commands
26498 @subsection Shared Library @sc{gdb/mi} Catchpoints
26500 @subheading The @code{-catch-load} Command
26501 @findex -catch-load
26503 @subsubheading Synopsis
26506 -catch-load [ -t ] [ -d ] @var{regexp}
26509 Add a catchpoint for library load events. If the @samp{-t} option is used,
26510 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26511 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
26512 in a disabled state. The @samp{regexp} argument is a regular
26513 expression used to match the name of the loaded library.
26516 @subsubheading @value{GDBN} Command
26518 The corresponding @value{GDBN} command is @samp{catch load}.
26520 @subsubheading Example
26523 -catch-load -t foo.so
26524 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
26525 what="load of library matching foo.so",catch-type="load",times="0"@}
26530 @subheading The @code{-catch-unload} Command
26531 @findex -catch-unload
26533 @subsubheading Synopsis
26536 -catch-unload [ -t ] [ -d ] @var{regexp}
26539 Add a catchpoint for library unload events. If the @samp{-t} option is
26540 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
26541 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
26542 created in a disabled state. The @samp{regexp} argument is a regular
26543 expression used to match the name of the unloaded library.
26545 @subsubheading @value{GDBN} Command
26547 The corresponding @value{GDBN} command is @samp{catch unload}.
26549 @subsubheading Example
26552 -catch-unload -d bar.so
26553 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
26554 what="load of library matching bar.so",catch-type="unload",times="0"@}
26558 @node Ada Exception GDB/MI Catchpoint Commands
26559 @subsection Ada Exception @sc{gdb/mi} Catchpoints
26561 The following @sc{gdb/mi} commands can be used to create catchpoints
26562 that stop the execution when Ada exceptions are being raised.
26564 @subheading The @code{-catch-assert} Command
26565 @findex -catch-assert
26567 @subsubheading Synopsis
26570 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
26573 Add a catchpoint for failed Ada assertions.
26575 The possible optional parameters for this command are:
26578 @item -c @var{condition}
26579 Make the catchpoint conditional on @var{condition}.
26581 Create a disabled catchpoint.
26583 Create a temporary catchpoint.
26586 @subsubheading @value{GDBN} Command
26588 The corresponding @value{GDBN} command is @samp{catch assert}.
26590 @subsubheading Example
26594 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
26595 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
26596 thread-groups=["i1"],times="0",
26597 original-location="__gnat_debug_raise_assert_failure"@}
26601 @subheading The @code{-catch-exception} Command
26602 @findex -catch-exception
26604 @subsubheading Synopsis
26607 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
26611 Add a catchpoint stopping when Ada exceptions are raised.
26612 By default, the command stops the program when any Ada exception
26613 gets raised. But it is also possible, by using some of the
26614 optional parameters described below, to create more selective
26617 The possible optional parameters for this command are:
26620 @item -c @var{condition}
26621 Make the catchpoint conditional on @var{condition}.
26623 Create a disabled catchpoint.
26624 @item -e @var{exception-name}
26625 Only stop when @var{exception-name} is raised. This option cannot
26626 be used combined with @samp{-u}.
26628 Create a temporary catchpoint.
26630 Stop only when an unhandled exception gets raised. This option
26631 cannot be used combined with @samp{-e}.
26634 @subsubheading @value{GDBN} Command
26636 The corresponding @value{GDBN} commands are @samp{catch exception}
26637 and @samp{catch exception unhandled}.
26639 @subsubheading Example
26642 -catch-exception -e Program_Error
26643 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
26644 enabled="y",addr="0x0000000000404874",
26645 what="`Program_Error' Ada exception", thread-groups=["i1"],
26646 times="0",original-location="__gnat_debug_raise_exception"@}
26650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26651 @node GDB/MI Program Context
26652 @section @sc{gdb/mi} Program Context
26654 @subheading The @code{-exec-arguments} Command
26655 @findex -exec-arguments
26658 @subsubheading Synopsis
26661 -exec-arguments @var{args}
26664 Set the inferior program arguments, to be used in the next
26667 @subsubheading @value{GDBN} Command
26669 The corresponding @value{GDBN} command is @samp{set args}.
26671 @subsubheading Example
26675 -exec-arguments -v word
26682 @subheading The @code{-exec-show-arguments} Command
26683 @findex -exec-show-arguments
26685 @subsubheading Synopsis
26688 -exec-show-arguments
26691 Print the arguments of the program.
26693 @subsubheading @value{GDBN} Command
26695 The corresponding @value{GDBN} command is @samp{show args}.
26697 @subsubheading Example
26702 @subheading The @code{-environment-cd} Command
26703 @findex -environment-cd
26705 @subsubheading Synopsis
26708 -environment-cd @var{pathdir}
26711 Set @value{GDBN}'s working directory.
26713 @subsubheading @value{GDBN} Command
26715 The corresponding @value{GDBN} command is @samp{cd}.
26717 @subsubheading Example
26721 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26727 @subheading The @code{-environment-directory} Command
26728 @findex -environment-directory
26730 @subsubheading Synopsis
26733 -environment-directory [ -r ] [ @var{pathdir} ]+
26736 Add directories @var{pathdir} to beginning of search path for source files.
26737 If the @samp{-r} option is used, the search path is reset to the default
26738 search path. If directories @var{pathdir} are supplied in addition to the
26739 @samp{-r} option, the search path is first reset and then addition
26741 Multiple directories may be specified, separated by blanks. Specifying
26742 multiple directories in a single command
26743 results in the directories added to the beginning of the
26744 search path in the same order they were presented in the command.
26745 If blanks are needed as
26746 part of a directory name, double-quotes should be used around
26747 the name. In the command output, the path will show up separated
26748 by the system directory-separator character. The directory-separator
26749 character must not be used
26750 in any directory name.
26751 If no directories are specified, the current search path is displayed.
26753 @subsubheading @value{GDBN} Command
26755 The corresponding @value{GDBN} command is @samp{dir}.
26757 @subsubheading Example
26761 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26762 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26764 -environment-directory ""
26765 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26767 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26768 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26770 -environment-directory -r
26771 ^done,source-path="$cdir:$cwd"
26776 @subheading The @code{-environment-path} Command
26777 @findex -environment-path
26779 @subsubheading Synopsis
26782 -environment-path [ -r ] [ @var{pathdir} ]+
26785 Add directories @var{pathdir} to beginning of search path for object files.
26786 If the @samp{-r} option is used, the search path is reset to the original
26787 search path that existed at gdb start-up. If directories @var{pathdir} are
26788 supplied in addition to the
26789 @samp{-r} option, the search path is first reset and then addition
26791 Multiple directories may be specified, separated by blanks. Specifying
26792 multiple directories in a single command
26793 results in the directories added to the beginning of the
26794 search path in the same order they were presented in the command.
26795 If blanks are needed as
26796 part of a directory name, double-quotes should be used around
26797 the name. In the command output, the path will show up separated
26798 by the system directory-separator character. The directory-separator
26799 character must not be used
26800 in any directory name.
26801 If no directories are specified, the current path is displayed.
26804 @subsubheading @value{GDBN} Command
26806 The corresponding @value{GDBN} command is @samp{path}.
26808 @subsubheading Example
26813 ^done,path="/usr/bin"
26815 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26816 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26818 -environment-path -r /usr/local/bin
26819 ^done,path="/usr/local/bin:/usr/bin"
26824 @subheading The @code{-environment-pwd} Command
26825 @findex -environment-pwd
26827 @subsubheading Synopsis
26833 Show the current working directory.
26835 @subsubheading @value{GDBN} Command
26837 The corresponding @value{GDBN} command is @samp{pwd}.
26839 @subsubheading Example
26844 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26848 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26849 @node GDB/MI Thread Commands
26850 @section @sc{gdb/mi} Thread Commands
26853 @subheading The @code{-thread-info} Command
26854 @findex -thread-info
26856 @subsubheading Synopsis
26859 -thread-info [ @var{thread-id} ]
26862 Reports information about either a specific thread, if
26863 the @var{thread-id} parameter is present, or about all
26864 threads. When printing information about all threads,
26865 also reports the current thread.
26867 @subsubheading @value{GDBN} Command
26869 The @samp{info thread} command prints the same information
26872 @subsubheading Result
26874 The result is a list of threads. The following attributes are
26875 defined for a given thread:
26879 This field exists only for the current thread. It has the value @samp{*}.
26882 The identifier that @value{GDBN} uses to refer to the thread.
26885 The identifier that the target uses to refer to the thread.
26888 Extra information about the thread, in a target-specific format. This
26892 The name of the thread. If the user specified a name using the
26893 @code{thread name} command, then this name is given. Otherwise, if
26894 @value{GDBN} can extract the thread name from the target, then that
26895 name is given. If @value{GDBN} cannot find the thread name, then this
26899 The stack frame currently executing in the thread.
26902 The thread's state. The @samp{state} field may have the following
26907 The thread is stopped. Frame information is available for stopped
26911 The thread is running. There's no frame information for running
26917 If @value{GDBN} can find the CPU core on which this thread is running,
26918 then this field is the core identifier. This field is optional.
26922 @subsubheading Example
26927 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26928 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26929 args=[]@},state="running"@},
26930 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26931 frame=@{level="0",addr="0x0804891f",func="foo",
26932 args=[@{name="i",value="10"@}],
26933 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26934 state="running"@}],
26935 current-thread-id="1"
26939 @subheading The @code{-thread-list-ids} Command
26940 @findex -thread-list-ids
26942 @subsubheading Synopsis
26948 Produces a list of the currently known @value{GDBN} thread ids. At the
26949 end of the list it also prints the total number of such threads.
26951 This command is retained for historical reasons, the
26952 @code{-thread-info} command should be used instead.
26954 @subsubheading @value{GDBN} Command
26956 Part of @samp{info threads} supplies the same information.
26958 @subsubheading Example
26963 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26964 current-thread-id="1",number-of-threads="3"
26969 @subheading The @code{-thread-select} Command
26970 @findex -thread-select
26972 @subsubheading Synopsis
26975 -thread-select @var{threadnum}
26978 Make @var{threadnum} the current thread. It prints the number of the new
26979 current thread, and the topmost frame for that thread.
26981 This command is deprecated in favor of explicitly using the
26982 @samp{--thread} option to each command.
26984 @subsubheading @value{GDBN} Command
26986 The corresponding @value{GDBN} command is @samp{thread}.
26988 @subsubheading Example
26995 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26996 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27000 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27001 number-of-threads="3"
27004 ^done,new-thread-id="3",
27005 frame=@{level="0",func="vprintf",
27006 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27007 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27011 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27012 @node GDB/MI Ada Tasking Commands
27013 @section @sc{gdb/mi} Ada Tasking Commands
27015 @subheading The @code{-ada-task-info} Command
27016 @findex -ada-task-info
27018 @subsubheading Synopsis
27021 -ada-task-info [ @var{task-id} ]
27024 Reports information about either a specific Ada task, if the
27025 @var{task-id} parameter is present, or about all Ada tasks.
27027 @subsubheading @value{GDBN} Command
27029 The @samp{info tasks} command prints the same information
27030 about all Ada tasks (@pxref{Ada Tasks}).
27032 @subsubheading Result
27034 The result is a table of Ada tasks. The following columns are
27035 defined for each Ada task:
27039 This field exists only for the current thread. It has the value @samp{*}.
27042 The identifier that @value{GDBN} uses to refer to the Ada task.
27045 The identifier that the target uses to refer to the Ada task.
27048 The identifier of the thread corresponding to the Ada task.
27050 This field should always exist, as Ada tasks are always implemented
27051 on top of a thread. But if @value{GDBN} cannot find this corresponding
27052 thread for any reason, the field is omitted.
27055 This field exists only when the task was created by another task.
27056 In this case, it provides the ID of the parent task.
27059 The base priority of the task.
27062 The current state of the task. For a detailed description of the
27063 possible states, see @ref{Ada Tasks}.
27066 The name of the task.
27070 @subsubheading Example
27074 ^done,tasks=@{nr_rows="3",nr_cols="8",
27075 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27076 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27077 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27078 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27079 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27080 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27081 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27082 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27083 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27084 state="Child Termination Wait",name="main_task"@}]@}
27088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27089 @node GDB/MI Program Execution
27090 @section @sc{gdb/mi} Program Execution
27092 These are the asynchronous commands which generate the out-of-band
27093 record @samp{*stopped}. Currently @value{GDBN} only really executes
27094 asynchronously with remote targets and this interaction is mimicked in
27097 @subheading The @code{-exec-continue} Command
27098 @findex -exec-continue
27100 @subsubheading Synopsis
27103 -exec-continue [--reverse] [--all|--thread-group N]
27106 Resumes the execution of the inferior program, which will continue
27107 to execute until it reaches a debugger stop event. If the
27108 @samp{--reverse} option is specified, execution resumes in reverse until
27109 it reaches a stop event. Stop events may include
27112 breakpoints or watchpoints
27114 signals or exceptions
27116 the end of the process (or its beginning under @samp{--reverse})
27118 the end or beginning of a replay log if one is being used.
27120 In all-stop mode (@pxref{All-Stop
27121 Mode}), may resume only one thread, or all threads, depending on the
27122 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27123 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27124 ignored in all-stop mode. If the @samp{--thread-group} options is
27125 specified, then all threads in that thread group are resumed.
27127 @subsubheading @value{GDBN} Command
27129 The corresponding @value{GDBN} corresponding is @samp{continue}.
27131 @subsubheading Example
27138 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27139 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27145 @subheading The @code{-exec-finish} Command
27146 @findex -exec-finish
27148 @subsubheading Synopsis
27151 -exec-finish [--reverse]
27154 Resumes the execution of the inferior program until the current
27155 function is exited. Displays the results returned by the function.
27156 If the @samp{--reverse} option is specified, resumes the reverse
27157 execution of the inferior program until the point where current
27158 function was called.
27160 @subsubheading @value{GDBN} Command
27162 The corresponding @value{GDBN} command is @samp{finish}.
27164 @subsubheading Example
27166 Function returning @code{void}.
27173 *stopped,reason="function-finished",frame=@{func="main",args=[],
27174 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27178 Function returning other than @code{void}. The name of the internal
27179 @value{GDBN} variable storing the result is printed, together with the
27186 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27187 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27188 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27189 gdb-result-var="$1",return-value="0"
27194 @subheading The @code{-exec-interrupt} Command
27195 @findex -exec-interrupt
27197 @subsubheading Synopsis
27200 -exec-interrupt [--all|--thread-group N]
27203 Interrupts the background execution of the target. Note how the token
27204 associated with the stop message is the one for the execution command
27205 that has been interrupted. The token for the interrupt itself only
27206 appears in the @samp{^done} output. If the user is trying to
27207 interrupt a non-running program, an error message will be printed.
27209 Note that when asynchronous execution is enabled, this command is
27210 asynchronous just like other execution commands. That is, first the
27211 @samp{^done} response will be printed, and the target stop will be
27212 reported after that using the @samp{*stopped} notification.
27214 In non-stop mode, only the context thread is interrupted by default.
27215 All threads (in all inferiors) will be interrupted if the
27216 @samp{--all} option is specified. If the @samp{--thread-group}
27217 option is specified, all threads in that group will be interrupted.
27219 @subsubheading @value{GDBN} Command
27221 The corresponding @value{GDBN} command is @samp{interrupt}.
27223 @subsubheading Example
27234 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27235 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27236 fullname="/home/foo/bar/try.c",line="13"@}
27241 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27245 @subheading The @code{-exec-jump} Command
27248 @subsubheading Synopsis
27251 -exec-jump @var{location}
27254 Resumes execution of the inferior program at the location specified by
27255 parameter. @xref{Specify Location}, for a description of the
27256 different forms of @var{location}.
27258 @subsubheading @value{GDBN} Command
27260 The corresponding @value{GDBN} command is @samp{jump}.
27262 @subsubheading Example
27265 -exec-jump foo.c:10
27266 *running,thread-id="all"
27271 @subheading The @code{-exec-next} Command
27274 @subsubheading Synopsis
27277 -exec-next [--reverse]
27280 Resumes execution of the inferior program, stopping when the beginning
27281 of the next source line is reached.
27283 If the @samp{--reverse} option is specified, resumes reverse execution
27284 of the inferior program, stopping at the beginning of the previous
27285 source line. If you issue this command on the first line of a
27286 function, it will take you back to the caller of that function, to the
27287 source line where the function was called.
27290 @subsubheading @value{GDBN} Command
27292 The corresponding @value{GDBN} command is @samp{next}.
27294 @subsubheading Example
27300 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27305 @subheading The @code{-exec-next-instruction} Command
27306 @findex -exec-next-instruction
27308 @subsubheading Synopsis
27311 -exec-next-instruction [--reverse]
27314 Executes one machine instruction. If the instruction is a function
27315 call, continues until the function returns. If the program stops at an
27316 instruction in the middle of a source line, the address will be
27319 If the @samp{--reverse} option is specified, resumes reverse execution
27320 of the inferior program, stopping at the previous instruction. If the
27321 previously executed instruction was a return from another function,
27322 it will continue to execute in reverse until the call to that function
27323 (from the current stack frame) is reached.
27325 @subsubheading @value{GDBN} Command
27327 The corresponding @value{GDBN} command is @samp{nexti}.
27329 @subsubheading Example
27333 -exec-next-instruction
27337 *stopped,reason="end-stepping-range",
27338 addr="0x000100d4",line="5",file="hello.c"
27343 @subheading The @code{-exec-return} Command
27344 @findex -exec-return
27346 @subsubheading Synopsis
27352 Makes current function return immediately. Doesn't execute the inferior.
27353 Displays the new current frame.
27355 @subsubheading @value{GDBN} Command
27357 The corresponding @value{GDBN} command is @samp{return}.
27359 @subsubheading Example
27363 200-break-insert callee4
27364 200^done,bkpt=@{number="1",addr="0x00010734",
27365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27370 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27371 frame=@{func="callee4",args=[],
27372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27373 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27379 111^done,frame=@{level="0",func="callee3",
27380 args=[@{name="strarg",
27381 value="0x11940 \"A string argument.\""@}],
27382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27388 @subheading The @code{-exec-run} Command
27391 @subsubheading Synopsis
27394 -exec-run [ --all | --thread-group N ] [ --start ]
27397 Starts execution of the inferior from the beginning. The inferior
27398 executes until either a breakpoint is encountered or the program
27399 exits. In the latter case the output will include an exit code, if
27400 the program has exited exceptionally.
27402 When neither the @samp{--all} nor the @samp{--thread-group} option
27403 is specified, the current inferior is started. If the
27404 @samp{--thread-group} option is specified, it should refer to a thread
27405 group of type @samp{process}, and that thread group will be started.
27406 If the @samp{--all} option is specified, then all inferiors will be started.
27408 Using the @samp{--start} option instructs the debugger to stop
27409 the execution at the start of the inferior's main subprogram,
27410 following the same behavior as the @code{start} command
27411 (@pxref{Starting}).
27413 @subsubheading @value{GDBN} Command
27415 The corresponding @value{GDBN} command is @samp{run}.
27417 @subsubheading Examples
27422 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27427 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27428 frame=@{func="main",args=[],file="recursive2.c",
27429 fullname="/home/foo/bar/recursive2.c",line="4"@}
27434 Program exited normally:
27442 *stopped,reason="exited-normally"
27447 Program exited exceptionally:
27455 *stopped,reason="exited",exit-code="01"
27459 Another way the program can terminate is if it receives a signal such as
27460 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27464 *stopped,reason="exited-signalled",signal-name="SIGINT",
27465 signal-meaning="Interrupt"
27469 @c @subheading -exec-signal
27472 @subheading The @code{-exec-step} Command
27475 @subsubheading Synopsis
27478 -exec-step [--reverse]
27481 Resumes execution of the inferior program, stopping when the beginning
27482 of the next source line is reached, if the next source line is not a
27483 function call. If it is, stop at the first instruction of the called
27484 function. If the @samp{--reverse} option is specified, resumes reverse
27485 execution of the inferior program, stopping at the beginning of the
27486 previously executed source line.
27488 @subsubheading @value{GDBN} Command
27490 The corresponding @value{GDBN} command is @samp{step}.
27492 @subsubheading Example
27494 Stepping into a function:
27500 *stopped,reason="end-stepping-range",
27501 frame=@{func="foo",args=[@{name="a",value="10"@},
27502 @{name="b",value="0"@}],file="recursive2.c",
27503 fullname="/home/foo/bar/recursive2.c",line="11"@}
27513 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27518 @subheading The @code{-exec-step-instruction} Command
27519 @findex -exec-step-instruction
27521 @subsubheading Synopsis
27524 -exec-step-instruction [--reverse]
27527 Resumes the inferior which executes one machine instruction. If the
27528 @samp{--reverse} option is specified, resumes reverse execution of the
27529 inferior program, stopping at the previously executed instruction.
27530 The output, once @value{GDBN} has stopped, will vary depending on
27531 whether we have stopped in the middle of a source line or not. In the
27532 former case, the address at which the program stopped will be printed
27535 @subsubheading @value{GDBN} Command
27537 The corresponding @value{GDBN} command is @samp{stepi}.
27539 @subsubheading Example
27543 -exec-step-instruction
27547 *stopped,reason="end-stepping-range",
27548 frame=@{func="foo",args=[],file="try.c",
27549 fullname="/home/foo/bar/try.c",line="10"@}
27551 -exec-step-instruction
27555 *stopped,reason="end-stepping-range",
27556 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27557 fullname="/home/foo/bar/try.c",line="10"@}
27562 @subheading The @code{-exec-until} Command
27563 @findex -exec-until
27565 @subsubheading Synopsis
27568 -exec-until [ @var{location} ]
27571 Executes the inferior until the @var{location} specified in the
27572 argument is reached. If there is no argument, the inferior executes
27573 until a source line greater than the current one is reached. The
27574 reason for stopping in this case will be @samp{location-reached}.
27576 @subsubheading @value{GDBN} Command
27578 The corresponding @value{GDBN} command is @samp{until}.
27580 @subsubheading Example
27584 -exec-until recursive2.c:6
27588 *stopped,reason="location-reached",frame=@{func="main",args=[],
27589 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27594 @subheading -file-clear
27595 Is this going away????
27598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27599 @node GDB/MI Stack Manipulation
27600 @section @sc{gdb/mi} Stack Manipulation Commands
27602 @subheading The @code{-enable-frame-filters} Command
27603 @findex -enable-frame-filters
27606 -enable-frame-filters
27609 @value{GDBN} allows Python-based frame filters to affect the output of
27610 the MI commands relating to stack traces. As there is no way to
27611 implement this in a fully backward-compatible way, a front end must
27612 request that this functionality be enabled.
27614 Once enabled, this feature cannot be disabled.
27616 Note that if Python support has not been compiled into @value{GDBN},
27617 this command will still succeed (and do nothing).
27619 @subheading The @code{-stack-info-frame} Command
27620 @findex -stack-info-frame
27622 @subsubheading Synopsis
27628 Get info on the selected frame.
27630 @subsubheading @value{GDBN} Command
27632 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27633 (without arguments).
27635 @subsubheading Example
27640 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27641 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27642 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27646 @subheading The @code{-stack-info-depth} Command
27647 @findex -stack-info-depth
27649 @subsubheading Synopsis
27652 -stack-info-depth [ @var{max-depth} ]
27655 Return the depth of the stack. If the integer argument @var{max-depth}
27656 is specified, do not count beyond @var{max-depth} frames.
27658 @subsubheading @value{GDBN} Command
27660 There's no equivalent @value{GDBN} command.
27662 @subsubheading Example
27664 For a stack with frame levels 0 through 11:
27671 -stack-info-depth 4
27674 -stack-info-depth 12
27677 -stack-info-depth 11
27680 -stack-info-depth 13
27685 @anchor{-stack-list-arguments}
27686 @subheading The @code{-stack-list-arguments} Command
27687 @findex -stack-list-arguments
27689 @subsubheading Synopsis
27692 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27693 [ @var{low-frame} @var{high-frame} ]
27696 Display a list of the arguments for the frames between @var{low-frame}
27697 and @var{high-frame} (inclusive). If @var{low-frame} and
27698 @var{high-frame} are not provided, list the arguments for the whole
27699 call stack. If the two arguments are equal, show the single frame
27700 at the corresponding level. It is an error if @var{low-frame} is
27701 larger than the actual number of frames. On the other hand,
27702 @var{high-frame} may be larger than the actual number of frames, in
27703 which case only existing frames will be returned.
27705 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27706 the variables; if it is 1 or @code{--all-values}, print also their
27707 values; and if it is 2 or @code{--simple-values}, print the name,
27708 type and value for simple data types, and the name and type for arrays,
27709 structures and unions. If the option @code{--no-frame-filters} is
27710 supplied, then Python frame filters will not be executed.
27712 If the @code{--skip-unavailable} option is specified, arguments that
27713 are not available are not listed. Partially available arguments
27714 are still displayed, however.
27716 Use of this command to obtain arguments in a single frame is
27717 deprecated in favor of the @samp{-stack-list-variables} command.
27719 @subsubheading @value{GDBN} Command
27721 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27722 @samp{gdb_get_args} command which partially overlaps with the
27723 functionality of @samp{-stack-list-arguments}.
27725 @subsubheading Example
27732 frame=@{level="0",addr="0x00010734",func="callee4",
27733 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27734 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27735 frame=@{level="1",addr="0x0001076c",func="callee3",
27736 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27737 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27738 frame=@{level="2",addr="0x0001078c",func="callee2",
27739 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27740 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27741 frame=@{level="3",addr="0x000107b4",func="callee1",
27742 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27743 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27744 frame=@{level="4",addr="0x000107e0",func="main",
27745 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27746 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27748 -stack-list-arguments 0
27751 frame=@{level="0",args=[]@},
27752 frame=@{level="1",args=[name="strarg"]@},
27753 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27754 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27755 frame=@{level="4",args=[]@}]
27757 -stack-list-arguments 1
27760 frame=@{level="0",args=[]@},
27762 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27763 frame=@{level="2",args=[
27764 @{name="intarg",value="2"@},
27765 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27766 @{frame=@{level="3",args=[
27767 @{name="intarg",value="2"@},
27768 @{name="strarg",value="0x11940 \"A string argument.\""@},
27769 @{name="fltarg",value="3.5"@}]@},
27770 frame=@{level="4",args=[]@}]
27772 -stack-list-arguments 0 2 2
27773 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27775 -stack-list-arguments 1 2 2
27776 ^done,stack-args=[frame=@{level="2",
27777 args=[@{name="intarg",value="2"@},
27778 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27782 @c @subheading -stack-list-exception-handlers
27785 @anchor{-stack-list-frames}
27786 @subheading The @code{-stack-list-frames} Command
27787 @findex -stack-list-frames
27789 @subsubheading Synopsis
27792 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
27795 List the frames currently on the stack. For each frame it displays the
27800 The frame number, 0 being the topmost frame, i.e., the innermost function.
27802 The @code{$pc} value for that frame.
27806 File name of the source file where the function lives.
27807 @item @var{fullname}
27808 The full file name of the source file where the function lives.
27810 Line number corresponding to the @code{$pc}.
27812 The shared library where this function is defined. This is only given
27813 if the frame's function is not known.
27816 If invoked without arguments, this command prints a backtrace for the
27817 whole stack. If given two integer arguments, it shows the frames whose
27818 levels are between the two arguments (inclusive). If the two arguments
27819 are equal, it shows the single frame at the corresponding level. It is
27820 an error if @var{low-frame} is larger than the actual number of
27821 frames. On the other hand, @var{high-frame} may be larger than the
27822 actual number of frames, in which case only existing frames will be
27823 returned. If the option @code{--no-frame-filters} is supplied, then
27824 Python frame filters will not be executed.
27826 @subsubheading @value{GDBN} Command
27828 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27830 @subsubheading Example
27832 Full stack backtrace:
27838 [frame=@{level="0",addr="0x0001076c",func="foo",
27839 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27840 frame=@{level="1",addr="0x000107a4",func="foo",
27841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27842 frame=@{level="2",addr="0x000107a4",func="foo",
27843 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27844 frame=@{level="3",addr="0x000107a4",func="foo",
27845 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27846 frame=@{level="4",addr="0x000107a4",func="foo",
27847 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27848 frame=@{level="5",addr="0x000107a4",func="foo",
27849 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27850 frame=@{level="6",addr="0x000107a4",func="foo",
27851 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27852 frame=@{level="7",addr="0x000107a4",func="foo",
27853 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27854 frame=@{level="8",addr="0x000107a4",func="foo",
27855 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27856 frame=@{level="9",addr="0x000107a4",func="foo",
27857 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27858 frame=@{level="10",addr="0x000107a4",func="foo",
27859 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27860 frame=@{level="11",addr="0x00010738",func="main",
27861 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27865 Show frames between @var{low_frame} and @var{high_frame}:
27869 -stack-list-frames 3 5
27871 [frame=@{level="3",addr="0x000107a4",func="foo",
27872 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27873 frame=@{level="4",addr="0x000107a4",func="foo",
27874 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27875 frame=@{level="5",addr="0x000107a4",func="foo",
27876 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27880 Show a single frame:
27884 -stack-list-frames 3 3
27886 [frame=@{level="3",addr="0x000107a4",func="foo",
27887 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27892 @subheading The @code{-stack-list-locals} Command
27893 @findex -stack-list-locals
27894 @anchor{-stack-list-locals}
27896 @subsubheading Synopsis
27899 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27902 Display the local variable names for the selected frame. If
27903 @var{print-values} is 0 or @code{--no-values}, print only the names of
27904 the variables; if it is 1 or @code{--all-values}, print also their
27905 values; and if it is 2 or @code{--simple-values}, print the name,
27906 type and value for simple data types, and the name and type for arrays,
27907 structures and unions. In this last case, a frontend can immediately
27908 display the value of simple data types and create variable objects for
27909 other data types when the user wishes to explore their values in
27910 more detail. If the option @code{--no-frame-filters} is supplied, then
27911 Python frame filters will not be executed.
27913 If the @code{--skip-unavailable} option is specified, local variables
27914 that are not available are not listed. Partially available local
27915 variables are still displayed, however.
27917 This command is deprecated in favor of the
27918 @samp{-stack-list-variables} command.
27920 @subsubheading @value{GDBN} Command
27922 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27924 @subsubheading Example
27928 -stack-list-locals 0
27929 ^done,locals=[name="A",name="B",name="C"]
27931 -stack-list-locals --all-values
27932 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27933 @{name="C",value="@{1, 2, 3@}"@}]
27934 -stack-list-locals --simple-values
27935 ^done,locals=[@{name="A",type="int",value="1"@},
27936 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27940 @anchor{-stack-list-variables}
27941 @subheading The @code{-stack-list-variables} Command
27942 @findex -stack-list-variables
27944 @subsubheading Synopsis
27947 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
27950 Display the names of local variables and function arguments for the selected frame. If
27951 @var{print-values} is 0 or @code{--no-values}, print only the names of
27952 the variables; if it is 1 or @code{--all-values}, print also their
27953 values; and if it is 2 or @code{--simple-values}, print the name,
27954 type and value for simple data types, and the name and type for arrays,
27955 structures and unions. If the option @code{--no-frame-filters} is
27956 supplied, then Python frame filters will not be executed.
27958 If the @code{--skip-unavailable} option is specified, local variables
27959 and arguments that are not available are not listed. Partially
27960 available arguments and local variables are still displayed, however.
27962 @subsubheading Example
27966 -stack-list-variables --thread 1 --frame 0 --all-values
27967 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27972 @subheading The @code{-stack-select-frame} Command
27973 @findex -stack-select-frame
27975 @subsubheading Synopsis
27978 -stack-select-frame @var{framenum}
27981 Change the selected frame. Select a different frame @var{framenum} on
27984 This command in deprecated in favor of passing the @samp{--frame}
27985 option to every command.
27987 @subsubheading @value{GDBN} Command
27989 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27990 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27992 @subsubheading Example
27996 -stack-select-frame 2
28001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28002 @node GDB/MI Variable Objects
28003 @section @sc{gdb/mi} Variable Objects
28007 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28009 For the implementation of a variable debugger window (locals, watched
28010 expressions, etc.), we are proposing the adaptation of the existing code
28011 used by @code{Insight}.
28013 The two main reasons for that are:
28017 It has been proven in practice (it is already on its second generation).
28020 It will shorten development time (needless to say how important it is
28024 The original interface was designed to be used by Tcl code, so it was
28025 slightly changed so it could be used through @sc{gdb/mi}. This section
28026 describes the @sc{gdb/mi} operations that will be available and gives some
28027 hints about their use.
28029 @emph{Note}: In addition to the set of operations described here, we
28030 expect the @sc{gui} implementation of a variable window to require, at
28031 least, the following operations:
28034 @item @code{-gdb-show} @code{output-radix}
28035 @item @code{-stack-list-arguments}
28036 @item @code{-stack-list-locals}
28037 @item @code{-stack-select-frame}
28042 @subheading Introduction to Variable Objects
28044 @cindex variable objects in @sc{gdb/mi}
28046 Variable objects are "object-oriented" MI interface for examining and
28047 changing values of expressions. Unlike some other MI interfaces that
28048 work with expressions, variable objects are specifically designed for
28049 simple and efficient presentation in the frontend. A variable object
28050 is identified by string name. When a variable object is created, the
28051 frontend specifies the expression for that variable object. The
28052 expression can be a simple variable, or it can be an arbitrary complex
28053 expression, and can even involve CPU registers. After creating a
28054 variable object, the frontend can invoke other variable object
28055 operations---for example to obtain or change the value of a variable
28056 object, or to change display format.
28058 Variable objects have hierarchical tree structure. Any variable object
28059 that corresponds to a composite type, such as structure in C, has
28060 a number of child variable objects, for example corresponding to each
28061 element of a structure. A child variable object can itself have
28062 children, recursively. Recursion ends when we reach
28063 leaf variable objects, which always have built-in types. Child variable
28064 objects are created only by explicit request, so if a frontend
28065 is not interested in the children of a particular variable object, no
28066 child will be created.
28068 For a leaf variable object it is possible to obtain its value as a
28069 string, or set the value from a string. String value can be also
28070 obtained for a non-leaf variable object, but it's generally a string
28071 that only indicates the type of the object, and does not list its
28072 contents. Assignment to a non-leaf variable object is not allowed.
28074 A frontend does not need to read the values of all variable objects each time
28075 the program stops. Instead, MI provides an update command that lists all
28076 variable objects whose values has changed since the last update
28077 operation. This considerably reduces the amount of data that must
28078 be transferred to the frontend. As noted above, children variable
28079 objects are created on demand, and only leaf variable objects have a
28080 real value. As result, gdb will read target memory only for leaf
28081 variables that frontend has created.
28083 The automatic update is not always desirable. For example, a frontend
28084 might want to keep a value of some expression for future reference,
28085 and never update it. For another example, fetching memory is
28086 relatively slow for embedded targets, so a frontend might want
28087 to disable automatic update for the variables that are either not
28088 visible on the screen, or ``closed''. This is possible using so
28089 called ``frozen variable objects''. Such variable objects are never
28090 implicitly updated.
28092 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28093 fixed variable object, the expression is parsed when the variable
28094 object is created, including associating identifiers to specific
28095 variables. The meaning of expression never changes. For a floating
28096 variable object the values of variables whose names appear in the
28097 expressions are re-evaluated every time in the context of the current
28098 frame. Consider this example:
28103 struct work_state state;
28110 If a fixed variable object for the @code{state} variable is created in
28111 this function, and we enter the recursive call, the variable
28112 object will report the value of @code{state} in the top-level
28113 @code{do_work} invocation. On the other hand, a floating variable
28114 object will report the value of @code{state} in the current frame.
28116 If an expression specified when creating a fixed variable object
28117 refers to a local variable, the variable object becomes bound to the
28118 thread and frame in which the variable object is created. When such
28119 variable object is updated, @value{GDBN} makes sure that the
28120 thread/frame combination the variable object is bound to still exists,
28121 and re-evaluates the variable object in context of that thread/frame.
28123 The following is the complete set of @sc{gdb/mi} operations defined to
28124 access this functionality:
28126 @multitable @columnfractions .4 .6
28127 @item @strong{Operation}
28128 @tab @strong{Description}
28130 @item @code{-enable-pretty-printing}
28131 @tab enable Python-based pretty-printing
28132 @item @code{-var-create}
28133 @tab create a variable object
28134 @item @code{-var-delete}
28135 @tab delete the variable object and/or its children
28136 @item @code{-var-set-format}
28137 @tab set the display format of this variable
28138 @item @code{-var-show-format}
28139 @tab show the display format of this variable
28140 @item @code{-var-info-num-children}
28141 @tab tells how many children this object has
28142 @item @code{-var-list-children}
28143 @tab return a list of the object's children
28144 @item @code{-var-info-type}
28145 @tab show the type of this variable object
28146 @item @code{-var-info-expression}
28147 @tab print parent-relative expression that this variable object represents
28148 @item @code{-var-info-path-expression}
28149 @tab print full expression that this variable object represents
28150 @item @code{-var-show-attributes}
28151 @tab is this variable editable? does it exist here?
28152 @item @code{-var-evaluate-expression}
28153 @tab get the value of this variable
28154 @item @code{-var-assign}
28155 @tab set the value of this variable
28156 @item @code{-var-update}
28157 @tab update the variable and its children
28158 @item @code{-var-set-frozen}
28159 @tab set frozeness attribute
28160 @item @code{-var-set-update-range}
28161 @tab set range of children to display on update
28164 In the next subsection we describe each operation in detail and suggest
28165 how it can be used.
28167 @subheading Description And Use of Operations on Variable Objects
28169 @subheading The @code{-enable-pretty-printing} Command
28170 @findex -enable-pretty-printing
28173 -enable-pretty-printing
28176 @value{GDBN} allows Python-based visualizers to affect the output of the
28177 MI variable object commands. However, because there was no way to
28178 implement this in a fully backward-compatible way, a front end must
28179 request that this functionality be enabled.
28181 Once enabled, this feature cannot be disabled.
28183 Note that if Python support has not been compiled into @value{GDBN},
28184 this command will still succeed (and do nothing).
28186 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28187 may work differently in future versions of @value{GDBN}.
28189 @subheading The @code{-var-create} Command
28190 @findex -var-create
28192 @subsubheading Synopsis
28195 -var-create @{@var{name} | "-"@}
28196 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28199 This operation creates a variable object, which allows the monitoring of
28200 a variable, the result of an expression, a memory cell or a CPU
28203 The @var{name} parameter is the string by which the object can be
28204 referenced. It must be unique. If @samp{-} is specified, the varobj
28205 system will generate a string ``varNNNNNN'' automatically. It will be
28206 unique provided that one does not specify @var{name} of that format.
28207 The command fails if a duplicate name is found.
28209 The frame under which the expression should be evaluated can be
28210 specified by @var{frame-addr}. A @samp{*} indicates that the current
28211 frame should be used. A @samp{@@} indicates that a floating variable
28212 object must be created.
28214 @var{expression} is any expression valid on the current language set (must not
28215 begin with a @samp{*}), or one of the following:
28219 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28222 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28225 @samp{$@var{regname}} --- a CPU register name
28228 @cindex dynamic varobj
28229 A varobj's contents may be provided by a Python-based pretty-printer. In this
28230 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28231 have slightly different semantics in some cases. If the
28232 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28233 will never create a dynamic varobj. This ensures backward
28234 compatibility for existing clients.
28236 @subsubheading Result
28238 This operation returns attributes of the newly-created varobj. These
28243 The name of the varobj.
28246 The number of children of the varobj. This number is not necessarily
28247 reliable for a dynamic varobj. Instead, you must examine the
28248 @samp{has_more} attribute.
28251 The varobj's scalar value. For a varobj whose type is some sort of
28252 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28253 will not be interesting.
28256 The varobj's type. This is a string representation of the type, as
28257 would be printed by the @value{GDBN} CLI. If @samp{print object}
28258 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28259 @emph{actual} (derived) type of the object is shown rather than the
28260 @emph{declared} one.
28263 If a variable object is bound to a specific thread, then this is the
28264 thread's identifier.
28267 For a dynamic varobj, this indicates whether there appear to be any
28268 children available. For a non-dynamic varobj, this will be 0.
28271 This attribute will be present and have the value @samp{1} if the
28272 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28273 then this attribute will not be present.
28276 A dynamic varobj can supply a display hint to the front end. The
28277 value comes directly from the Python pretty-printer object's
28278 @code{display_hint} method. @xref{Pretty Printing API}.
28281 Typical output will look like this:
28284 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28285 has_more="@var{has_more}"
28289 @subheading The @code{-var-delete} Command
28290 @findex -var-delete
28292 @subsubheading Synopsis
28295 -var-delete [ -c ] @var{name}
28298 Deletes a previously created variable object and all of its children.
28299 With the @samp{-c} option, just deletes the children.
28301 Returns an error if the object @var{name} is not found.
28304 @subheading The @code{-var-set-format} Command
28305 @findex -var-set-format
28307 @subsubheading Synopsis
28310 -var-set-format @var{name} @var{format-spec}
28313 Sets the output format for the value of the object @var{name} to be
28316 @anchor{-var-set-format}
28317 The syntax for the @var{format-spec} is as follows:
28320 @var{format-spec} @expansion{}
28321 @{binary | decimal | hexadecimal | octal | natural@}
28324 The natural format is the default format choosen automatically
28325 based on the variable type (like decimal for an @code{int}, hex
28326 for pointers, etc.).
28328 For a variable with children, the format is set only on the
28329 variable itself, and the children are not affected.
28331 @subheading The @code{-var-show-format} Command
28332 @findex -var-show-format
28334 @subsubheading Synopsis
28337 -var-show-format @var{name}
28340 Returns the format used to display the value of the object @var{name}.
28343 @var{format} @expansion{}
28348 @subheading The @code{-var-info-num-children} Command
28349 @findex -var-info-num-children
28351 @subsubheading Synopsis
28354 -var-info-num-children @var{name}
28357 Returns the number of children of a variable object @var{name}:
28363 Note that this number is not completely reliable for a dynamic varobj.
28364 It will return the current number of children, but more children may
28368 @subheading The @code{-var-list-children} Command
28369 @findex -var-list-children
28371 @subsubheading Synopsis
28374 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28376 @anchor{-var-list-children}
28378 Return a list of the children of the specified variable object and
28379 create variable objects for them, if they do not already exist. With
28380 a single argument or if @var{print-values} has a value of 0 or
28381 @code{--no-values}, print only the names of the variables; if
28382 @var{print-values} is 1 or @code{--all-values}, also print their
28383 values; and if it is 2 or @code{--simple-values} print the name and
28384 value for simple data types and just the name for arrays, structures
28387 @var{from} and @var{to}, if specified, indicate the range of children
28388 to report. If @var{from} or @var{to} is less than zero, the range is
28389 reset and all children will be reported. Otherwise, children starting
28390 at @var{from} (zero-based) and up to and excluding @var{to} will be
28393 If a child range is requested, it will only affect the current call to
28394 @code{-var-list-children}, but not future calls to @code{-var-update}.
28395 For this, you must instead use @code{-var-set-update-range}. The
28396 intent of this approach is to enable a front end to implement any
28397 update approach it likes; for example, scrolling a view may cause the
28398 front end to request more children with @code{-var-list-children}, and
28399 then the front end could call @code{-var-set-update-range} with a
28400 different range to ensure that future updates are restricted to just
28403 For each child the following results are returned:
28408 Name of the variable object created for this child.
28411 The expression to be shown to the user by the front end to designate this child.
28412 For example this may be the name of a structure member.
28414 For a dynamic varobj, this value cannot be used to form an
28415 expression. There is no way to do this at all with a dynamic varobj.
28417 For C/C@t{++} structures there are several pseudo children returned to
28418 designate access qualifiers. For these pseudo children @var{exp} is
28419 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28420 type and value are not present.
28422 A dynamic varobj will not report the access qualifying
28423 pseudo-children, regardless of the language. This information is not
28424 available at all with a dynamic varobj.
28427 Number of children this child has. For a dynamic varobj, this will be
28431 The type of the child. If @samp{print object}
28432 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28433 @emph{actual} (derived) type of the object is shown rather than the
28434 @emph{declared} one.
28437 If values were requested, this is the value.
28440 If this variable object is associated with a thread, this is the thread id.
28441 Otherwise this result is not present.
28444 If the variable object is frozen, this variable will be present with a value of 1.
28447 A dynamic varobj can supply a display hint to the front end. The
28448 value comes directly from the Python pretty-printer object's
28449 @code{display_hint} method. @xref{Pretty Printing API}.
28452 This attribute will be present and have the value @samp{1} if the
28453 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28454 then this attribute will not be present.
28458 The result may have its own attributes:
28462 A dynamic varobj can supply a display hint to the front end. The
28463 value comes directly from the Python pretty-printer object's
28464 @code{display_hint} method. @xref{Pretty Printing API}.
28467 This is an integer attribute which is nonzero if there are children
28468 remaining after the end of the selected range.
28471 @subsubheading Example
28475 -var-list-children n
28476 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28477 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28479 -var-list-children --all-values n
28480 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28481 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28485 @subheading The @code{-var-info-type} Command
28486 @findex -var-info-type
28488 @subsubheading Synopsis
28491 -var-info-type @var{name}
28494 Returns the type of the specified variable @var{name}. The type is
28495 returned as a string in the same format as it is output by the
28499 type=@var{typename}
28503 @subheading The @code{-var-info-expression} Command
28504 @findex -var-info-expression
28506 @subsubheading Synopsis
28509 -var-info-expression @var{name}
28512 Returns a string that is suitable for presenting this
28513 variable object in user interface. The string is generally
28514 not valid expression in the current language, and cannot be evaluated.
28516 For example, if @code{a} is an array, and variable object
28517 @code{A} was created for @code{a}, then we'll get this output:
28520 (gdb) -var-info-expression A.1
28521 ^done,lang="C",exp="1"
28525 Here, the value of @code{lang} is the language name, which can be
28526 found in @ref{Supported Languages}.
28528 Note that the output of the @code{-var-list-children} command also
28529 includes those expressions, so the @code{-var-info-expression} command
28532 @subheading The @code{-var-info-path-expression} Command
28533 @findex -var-info-path-expression
28535 @subsubheading Synopsis
28538 -var-info-path-expression @var{name}
28541 Returns an expression that can be evaluated in the current
28542 context and will yield the same value that a variable object has.
28543 Compare this with the @code{-var-info-expression} command, which
28544 result can be used only for UI presentation. Typical use of
28545 the @code{-var-info-path-expression} command is creating a
28546 watchpoint from a variable object.
28548 This command is currently not valid for children of a dynamic varobj,
28549 and will give an error when invoked on one.
28551 For example, suppose @code{C} is a C@t{++} class, derived from class
28552 @code{Base}, and that the @code{Base} class has a member called
28553 @code{m_size}. Assume a variable @code{c} is has the type of
28554 @code{C} and a variable object @code{C} was created for variable
28555 @code{c}. Then, we'll get this output:
28557 (gdb) -var-info-path-expression C.Base.public.m_size
28558 ^done,path_expr=((Base)c).m_size)
28561 @subheading The @code{-var-show-attributes} Command
28562 @findex -var-show-attributes
28564 @subsubheading Synopsis
28567 -var-show-attributes @var{name}
28570 List attributes of the specified variable object @var{name}:
28573 status=@var{attr} [ ( ,@var{attr} )* ]
28577 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28579 @subheading The @code{-var-evaluate-expression} Command
28580 @findex -var-evaluate-expression
28582 @subsubheading Synopsis
28585 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28588 Evaluates the expression that is represented by the specified variable
28589 object and returns its value as a string. The format of the string
28590 can be specified with the @samp{-f} option. The possible values of
28591 this option are the same as for @code{-var-set-format}
28592 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28593 the current display format will be used. The current display format
28594 can be changed using the @code{-var-set-format} command.
28600 Note that one must invoke @code{-var-list-children} for a variable
28601 before the value of a child variable can be evaluated.
28603 @subheading The @code{-var-assign} Command
28604 @findex -var-assign
28606 @subsubheading Synopsis
28609 -var-assign @var{name} @var{expression}
28612 Assigns the value of @var{expression} to the variable object specified
28613 by @var{name}. The object must be @samp{editable}. If the variable's
28614 value is altered by the assign, the variable will show up in any
28615 subsequent @code{-var-update} list.
28617 @subsubheading Example
28625 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28629 @subheading The @code{-var-update} Command
28630 @findex -var-update
28632 @subsubheading Synopsis
28635 -var-update [@var{print-values}] @{@var{name} | "*"@}
28638 Reevaluate the expressions corresponding to the variable object
28639 @var{name} and all its direct and indirect children, and return the
28640 list of variable objects whose values have changed; @var{name} must
28641 be a root variable object. Here, ``changed'' means that the result of
28642 @code{-var-evaluate-expression} before and after the
28643 @code{-var-update} is different. If @samp{*} is used as the variable
28644 object names, all existing variable objects are updated, except
28645 for frozen ones (@pxref{-var-set-frozen}). The option
28646 @var{print-values} determines whether both names and values, or just
28647 names are printed. The possible values of this option are the same
28648 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28649 recommended to use the @samp{--all-values} option, to reduce the
28650 number of MI commands needed on each program stop.
28652 With the @samp{*} parameter, if a variable object is bound to a
28653 currently running thread, it will not be updated, without any
28656 If @code{-var-set-update-range} was previously used on a varobj, then
28657 only the selected range of children will be reported.
28659 @code{-var-update} reports all the changed varobjs in a tuple named
28662 Each item in the change list is itself a tuple holding:
28666 The name of the varobj.
28669 If values were requested for this update, then this field will be
28670 present and will hold the value of the varobj.
28673 @anchor{-var-update}
28674 This field is a string which may take one of three values:
28678 The variable object's current value is valid.
28681 The variable object does not currently hold a valid value but it may
28682 hold one in the future if its associated expression comes back into
28686 The variable object no longer holds a valid value.
28687 This can occur when the executable file being debugged has changed,
28688 either through recompilation or by using the @value{GDBN} @code{file}
28689 command. The front end should normally choose to delete these variable
28693 In the future new values may be added to this list so the front should
28694 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28697 This is only present if the varobj is still valid. If the type
28698 changed, then this will be the string @samp{true}; otherwise it will
28701 When a varobj's type changes, its children are also likely to have
28702 become incorrect. Therefore, the varobj's children are automatically
28703 deleted when this attribute is @samp{true}. Also, the varobj's update
28704 range, when set using the @code{-var-set-update-range} command, is
28708 If the varobj's type changed, then this field will be present and will
28711 @item new_num_children
28712 For a dynamic varobj, if the number of children changed, or if the
28713 type changed, this will be the new number of children.
28715 The @samp{numchild} field in other varobj responses is generally not
28716 valid for a dynamic varobj -- it will show the number of children that
28717 @value{GDBN} knows about, but because dynamic varobjs lazily
28718 instantiate their children, this will not reflect the number of
28719 children which may be available.
28721 The @samp{new_num_children} attribute only reports changes to the
28722 number of children known by @value{GDBN}. This is the only way to
28723 detect whether an update has removed children (which necessarily can
28724 only happen at the end of the update range).
28727 The display hint, if any.
28730 This is an integer value, which will be 1 if there are more children
28731 available outside the varobj's update range.
28734 This attribute will be present and have the value @samp{1} if the
28735 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28736 then this attribute will not be present.
28739 If new children were added to a dynamic varobj within the selected
28740 update range (as set by @code{-var-set-update-range}), then they will
28741 be listed in this attribute.
28744 @subsubheading Example
28751 -var-update --all-values var1
28752 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28753 type_changed="false"@}]
28757 @subheading The @code{-var-set-frozen} Command
28758 @findex -var-set-frozen
28759 @anchor{-var-set-frozen}
28761 @subsubheading Synopsis
28764 -var-set-frozen @var{name} @var{flag}
28767 Set the frozenness flag on the variable object @var{name}. The
28768 @var{flag} parameter should be either @samp{1} to make the variable
28769 frozen or @samp{0} to make it unfrozen. If a variable object is
28770 frozen, then neither itself, nor any of its children, are
28771 implicitly updated by @code{-var-update} of
28772 a parent variable or by @code{-var-update *}. Only
28773 @code{-var-update} of the variable itself will update its value and
28774 values of its children. After a variable object is unfrozen, it is
28775 implicitly updated by all subsequent @code{-var-update} operations.
28776 Unfreezing a variable does not update it, only subsequent
28777 @code{-var-update} does.
28779 @subsubheading Example
28783 -var-set-frozen V 1
28788 @subheading The @code{-var-set-update-range} command
28789 @findex -var-set-update-range
28790 @anchor{-var-set-update-range}
28792 @subsubheading Synopsis
28795 -var-set-update-range @var{name} @var{from} @var{to}
28798 Set the range of children to be returned by future invocations of
28799 @code{-var-update}.
28801 @var{from} and @var{to} indicate the range of children to report. If
28802 @var{from} or @var{to} is less than zero, the range is reset and all
28803 children will be reported. Otherwise, children starting at @var{from}
28804 (zero-based) and up to and excluding @var{to} will be reported.
28806 @subsubheading Example
28810 -var-set-update-range V 1 2
28814 @subheading The @code{-var-set-visualizer} command
28815 @findex -var-set-visualizer
28816 @anchor{-var-set-visualizer}
28818 @subsubheading Synopsis
28821 -var-set-visualizer @var{name} @var{visualizer}
28824 Set a visualizer for the variable object @var{name}.
28826 @var{visualizer} is the visualizer to use. The special value
28827 @samp{None} means to disable any visualizer in use.
28829 If not @samp{None}, @var{visualizer} must be a Python expression.
28830 This expression must evaluate to a callable object which accepts a
28831 single argument. @value{GDBN} will call this object with the value of
28832 the varobj @var{name} as an argument (this is done so that the same
28833 Python pretty-printing code can be used for both the CLI and MI).
28834 When called, this object must return an object which conforms to the
28835 pretty-printing interface (@pxref{Pretty Printing API}).
28837 The pre-defined function @code{gdb.default_visualizer} may be used to
28838 select a visualizer by following the built-in process
28839 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28840 a varobj is created, and so ordinarily is not needed.
28842 This feature is only available if Python support is enabled. The MI
28843 command @code{-list-features} (@pxref{GDB/MI Support Commands})
28844 can be used to check this.
28846 @subsubheading Example
28848 Resetting the visualizer:
28852 -var-set-visualizer V None
28856 Reselecting the default (type-based) visualizer:
28860 -var-set-visualizer V gdb.default_visualizer
28864 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28865 can be used to instantiate this class for a varobj:
28869 -var-set-visualizer V "lambda val: SomeClass()"
28873 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28874 @node GDB/MI Data Manipulation
28875 @section @sc{gdb/mi} Data Manipulation
28877 @cindex data manipulation, in @sc{gdb/mi}
28878 @cindex @sc{gdb/mi}, data manipulation
28879 This section describes the @sc{gdb/mi} commands that manipulate data:
28880 examine memory and registers, evaluate expressions, etc.
28882 @c REMOVED FROM THE INTERFACE.
28883 @c @subheading -data-assign
28884 @c Change the value of a program variable. Plenty of side effects.
28885 @c @subsubheading GDB Command
28887 @c @subsubheading Example
28890 @subheading The @code{-data-disassemble} Command
28891 @findex -data-disassemble
28893 @subsubheading Synopsis
28897 [ -s @var{start-addr} -e @var{end-addr} ]
28898 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28906 @item @var{start-addr}
28907 is the beginning address (or @code{$pc})
28908 @item @var{end-addr}
28910 @item @var{filename}
28911 is the name of the file to disassemble
28912 @item @var{linenum}
28913 is the line number to disassemble around
28915 is the number of disassembly lines to be produced. If it is -1,
28916 the whole function will be disassembled, in case no @var{end-addr} is
28917 specified. If @var{end-addr} is specified as a non-zero value, and
28918 @var{lines} is lower than the number of disassembly lines between
28919 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28920 displayed; if @var{lines} is higher than the number of lines between
28921 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28924 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28925 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28926 mixed source and disassembly with raw opcodes).
28929 @subsubheading Result
28931 The result of the @code{-data-disassemble} command will be a list named
28932 @samp{asm_insns}, the contents of this list depend on the @var{mode}
28933 used with the @code{-data-disassemble} command.
28935 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
28940 The address at which this instruction was disassembled.
28943 The name of the function this instruction is within.
28946 The decimal offset in bytes from the start of @samp{func-name}.
28949 The text disassembly for this @samp{address}.
28952 This field is only present for mode 2. This contains the raw opcode
28953 bytes for the @samp{inst} field.
28957 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
28958 @samp{src_and_asm_line}, each of which has the following fields:
28962 The line number within @samp{file}.
28965 The file name from the compilation unit. This might be an absolute
28966 file name or a relative file name depending on the compile command
28970 Absolute file name of @samp{file}. It is converted to a canonical form
28971 using the source file search path
28972 (@pxref{Source Path, ,Specifying Source Directories})
28973 and after resolving all the symbolic links.
28975 If the source file is not found this field will contain the path as
28976 present in the debug information.
28978 @item line_asm_insn
28979 This is a list of tuples containing the disassembly for @samp{line} in
28980 @samp{file}. The fields of each tuple are the same as for
28981 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
28982 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
28987 Note that whatever included in the @samp{inst} field, is not
28988 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
28991 @subsubheading @value{GDBN} Command
28993 The corresponding @value{GDBN} command is @samp{disassemble}.
28995 @subsubheading Example
28997 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29001 -data-disassemble -s $pc -e "$pc + 20" -- 0
29004 @{address="0x000107c0",func-name="main",offset="4",
29005 inst="mov 2, %o0"@},
29006 @{address="0x000107c4",func-name="main",offset="8",
29007 inst="sethi %hi(0x11800), %o2"@},
29008 @{address="0x000107c8",func-name="main",offset="12",
29009 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29010 @{address="0x000107cc",func-name="main",offset="16",
29011 inst="sethi %hi(0x11800), %o2"@},
29012 @{address="0x000107d0",func-name="main",offset="20",
29013 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29017 Disassemble the whole @code{main} function. Line 32 is part of
29021 -data-disassemble -f basics.c -l 32 -- 0
29023 @{address="0x000107bc",func-name="main",offset="0",
29024 inst="save %sp, -112, %sp"@},
29025 @{address="0x000107c0",func-name="main",offset="4",
29026 inst="mov 2, %o0"@},
29027 @{address="0x000107c4",func-name="main",offset="8",
29028 inst="sethi %hi(0x11800), %o2"@},
29030 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29031 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29035 Disassemble 3 instructions from the start of @code{main}:
29039 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29041 @{address="0x000107bc",func-name="main",offset="0",
29042 inst="save %sp, -112, %sp"@},
29043 @{address="0x000107c0",func-name="main",offset="4",
29044 inst="mov 2, %o0"@},
29045 @{address="0x000107c4",func-name="main",offset="8",
29046 inst="sethi %hi(0x11800), %o2"@}]
29050 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29054 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29056 src_and_asm_line=@{line="31",
29057 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29058 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29059 line_asm_insn=[@{address="0x000107bc",
29060 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29061 src_and_asm_line=@{line="32",
29062 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29063 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29064 line_asm_insn=[@{address="0x000107c0",
29065 func-name="main",offset="4",inst="mov 2, %o0"@},
29066 @{address="0x000107c4",func-name="main",offset="8",
29067 inst="sethi %hi(0x11800), %o2"@}]@}]
29072 @subheading The @code{-data-evaluate-expression} Command
29073 @findex -data-evaluate-expression
29075 @subsubheading Synopsis
29078 -data-evaluate-expression @var{expr}
29081 Evaluate @var{expr} as an expression. The expression could contain an
29082 inferior function call. The function call will execute synchronously.
29083 If the expression contains spaces, it must be enclosed in double quotes.
29085 @subsubheading @value{GDBN} Command
29087 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29088 @samp{call}. In @code{gdbtk} only, there's a corresponding
29089 @samp{gdb_eval} command.
29091 @subsubheading Example
29093 In the following example, the numbers that precede the commands are the
29094 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29095 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29099 211-data-evaluate-expression A
29102 311-data-evaluate-expression &A
29103 311^done,value="0xefffeb7c"
29105 411-data-evaluate-expression A+3
29108 511-data-evaluate-expression "A + 3"
29114 @subheading The @code{-data-list-changed-registers} Command
29115 @findex -data-list-changed-registers
29117 @subsubheading Synopsis
29120 -data-list-changed-registers
29123 Display a list of the registers that have changed.
29125 @subsubheading @value{GDBN} Command
29127 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29128 has the corresponding command @samp{gdb_changed_register_list}.
29130 @subsubheading Example
29132 On a PPC MBX board:
29140 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29141 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29144 -data-list-changed-registers
29145 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29146 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29147 "24","25","26","27","28","30","31","64","65","66","67","69"]
29152 @subheading The @code{-data-list-register-names} Command
29153 @findex -data-list-register-names
29155 @subsubheading Synopsis
29158 -data-list-register-names [ ( @var{regno} )+ ]
29161 Show a list of register names for the current target. If no arguments
29162 are given, it shows a list of the names of all the registers. If
29163 integer numbers are given as arguments, it will print a list of the
29164 names of the registers corresponding to the arguments. To ensure
29165 consistency between a register name and its number, the output list may
29166 include empty register names.
29168 @subsubheading @value{GDBN} Command
29170 @value{GDBN} does not have a command which corresponds to
29171 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29172 corresponding command @samp{gdb_regnames}.
29174 @subsubheading Example
29176 For the PPC MBX board:
29179 -data-list-register-names
29180 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29181 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29182 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29183 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29184 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29185 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29186 "", "pc","ps","cr","lr","ctr","xer"]
29188 -data-list-register-names 1 2 3
29189 ^done,register-names=["r1","r2","r3"]
29193 @subheading The @code{-data-list-register-values} Command
29194 @findex -data-list-register-values
29196 @subsubheading Synopsis
29199 -data-list-register-values
29200 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29203 Display the registers' contents. The format according to which the
29204 registers' contents are to be returned is given by @var{fmt}, followed
29205 by an optional list of numbers specifying the registers to display. A
29206 missing list of numbers indicates that the contents of all the
29207 registers must be returned. The @code{--skip-unavailable} option
29208 indicates that only the available registers are to be returned.
29210 Allowed formats for @var{fmt} are:
29227 @subsubheading @value{GDBN} Command
29229 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29230 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29232 @subsubheading Example
29234 For a PPC MBX board (note: line breaks are for readability only, they
29235 don't appear in the actual output):
29239 -data-list-register-values r 64 65
29240 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29241 @{number="65",value="0x00029002"@}]
29243 -data-list-register-values x
29244 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29245 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29246 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29247 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29248 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29249 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29250 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29251 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29252 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29253 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29254 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29255 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29256 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29257 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29258 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29259 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29260 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29261 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29262 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29263 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29264 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29265 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29266 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29267 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29268 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29269 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29270 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29271 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29272 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29273 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29274 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29275 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29276 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29277 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29278 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29279 @{number="69",value="0x20002b03"@}]
29284 @subheading The @code{-data-read-memory} Command
29285 @findex -data-read-memory
29287 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29289 @subsubheading Synopsis
29292 -data-read-memory [ -o @var{byte-offset} ]
29293 @var{address} @var{word-format} @var{word-size}
29294 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29301 @item @var{address}
29302 An expression specifying the address of the first memory word to be
29303 read. Complex expressions containing embedded white space should be
29304 quoted using the C convention.
29306 @item @var{word-format}
29307 The format to be used to print the memory words. The notation is the
29308 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29311 @item @var{word-size}
29312 The size of each memory word in bytes.
29314 @item @var{nr-rows}
29315 The number of rows in the output table.
29317 @item @var{nr-cols}
29318 The number of columns in the output table.
29321 If present, indicates that each row should include an @sc{ascii} dump. The
29322 value of @var{aschar} is used as a padding character when a byte is not a
29323 member of the printable @sc{ascii} character set (printable @sc{ascii}
29324 characters are those whose code is between 32 and 126, inclusively).
29326 @item @var{byte-offset}
29327 An offset to add to the @var{address} before fetching memory.
29330 This command displays memory contents as a table of @var{nr-rows} by
29331 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29332 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29333 (returned as @samp{total-bytes}). Should less than the requested number
29334 of bytes be returned by the target, the missing words are identified
29335 using @samp{N/A}. The number of bytes read from the target is returned
29336 in @samp{nr-bytes} and the starting address used to read memory in
29339 The address of the next/previous row or page is available in
29340 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29343 @subsubheading @value{GDBN} Command
29345 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29346 @samp{gdb_get_mem} memory read command.
29348 @subsubheading Example
29350 Read six bytes of memory starting at @code{bytes+6} but then offset by
29351 @code{-6} bytes. Format as three rows of two columns. One byte per
29352 word. Display each word in hex.
29356 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29357 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29358 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29359 prev-page="0x0000138a",memory=[
29360 @{addr="0x00001390",data=["0x00","0x01"]@},
29361 @{addr="0x00001392",data=["0x02","0x03"]@},
29362 @{addr="0x00001394",data=["0x04","0x05"]@}]
29366 Read two bytes of memory starting at address @code{shorts + 64} and
29367 display as a single word formatted in decimal.
29371 5-data-read-memory shorts+64 d 2 1 1
29372 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29373 next-row="0x00001512",prev-row="0x0000150e",
29374 next-page="0x00001512",prev-page="0x0000150e",memory=[
29375 @{addr="0x00001510",data=["128"]@}]
29379 Read thirty two bytes of memory starting at @code{bytes+16} and format
29380 as eight rows of four columns. Include a string encoding with @samp{x}
29381 used as the non-printable character.
29385 4-data-read-memory bytes+16 x 1 8 4 x
29386 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29387 next-row="0x000013c0",prev-row="0x0000139c",
29388 next-page="0x000013c0",prev-page="0x00001380",memory=[
29389 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29390 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29391 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29392 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29393 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29394 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29395 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29396 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29400 @subheading The @code{-data-read-memory-bytes} Command
29401 @findex -data-read-memory-bytes
29403 @subsubheading Synopsis
29406 -data-read-memory-bytes [ -o @var{byte-offset} ]
29407 @var{address} @var{count}
29414 @item @var{address}
29415 An expression specifying the address of the first memory word to be
29416 read. Complex expressions containing embedded white space should be
29417 quoted using the C convention.
29420 The number of bytes to read. This should be an integer literal.
29422 @item @var{byte-offset}
29423 The offsets in bytes relative to @var{address} at which to start
29424 reading. This should be an integer literal. This option is provided
29425 so that a frontend is not required to first evaluate address and then
29426 perform address arithmetics itself.
29430 This command attempts to read all accessible memory regions in the
29431 specified range. First, all regions marked as unreadable in the memory
29432 map (if one is defined) will be skipped. @xref{Memory Region
29433 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29434 regions. For each one, if reading full region results in an errors,
29435 @value{GDBN} will try to read a subset of the region.
29437 In general, every single byte in the region may be readable or not,
29438 and the only way to read every readable byte is to try a read at
29439 every address, which is not practical. Therefore, @value{GDBN} will
29440 attempt to read all accessible bytes at either beginning or the end
29441 of the region, using a binary division scheme. This heuristic works
29442 well for reading accross a memory map boundary. Note that if a region
29443 has a readable range that is neither at the beginning or the end,
29444 @value{GDBN} will not read it.
29446 The result record (@pxref{GDB/MI Result Records}) that is output of
29447 the command includes a field named @samp{memory} whose content is a
29448 list of tuples. Each tuple represent a successfully read memory block
29449 and has the following fields:
29453 The start address of the memory block, as hexadecimal literal.
29456 The end address of the memory block, as hexadecimal literal.
29459 The offset of the memory block, as hexadecimal literal, relative to
29460 the start address passed to @code{-data-read-memory-bytes}.
29463 The contents of the memory block, in hex.
29469 @subsubheading @value{GDBN} Command
29471 The corresponding @value{GDBN} command is @samp{x}.
29473 @subsubheading Example
29477 -data-read-memory-bytes &a 10
29478 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29480 contents="01000000020000000300"@}]
29485 @subheading The @code{-data-write-memory-bytes} Command
29486 @findex -data-write-memory-bytes
29488 @subsubheading Synopsis
29491 -data-write-memory-bytes @var{address} @var{contents}
29492 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
29499 @item @var{address}
29500 An expression specifying the address of the first memory word to be
29501 read. Complex expressions containing embedded white space should be
29502 quoted using the C convention.
29504 @item @var{contents}
29505 The hex-encoded bytes to write.
29508 Optional argument indicating the number of bytes to be written. If @var{count}
29509 is greater than @var{contents}' length, @value{GDBN} will repeatedly
29510 write @var{contents} until it fills @var{count} bytes.
29514 @subsubheading @value{GDBN} Command
29516 There's no corresponding @value{GDBN} command.
29518 @subsubheading Example
29522 -data-write-memory-bytes &a "aabbccdd"
29529 -data-write-memory-bytes &a "aabbccdd" 16e
29534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29535 @node GDB/MI Tracepoint Commands
29536 @section @sc{gdb/mi} Tracepoint Commands
29538 The commands defined in this section implement MI support for
29539 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29541 @subheading The @code{-trace-find} Command
29542 @findex -trace-find
29544 @subsubheading Synopsis
29547 -trace-find @var{mode} [@var{parameters}@dots{}]
29550 Find a trace frame using criteria defined by @var{mode} and
29551 @var{parameters}. The following table lists permissible
29552 modes and their parameters. For details of operation, see @ref{tfind}.
29557 No parameters are required. Stops examining trace frames.
29560 An integer is required as parameter. Selects tracepoint frame with
29563 @item tracepoint-number
29564 An integer is required as parameter. Finds next
29565 trace frame that corresponds to tracepoint with the specified number.
29568 An address is required as parameter. Finds
29569 next trace frame that corresponds to any tracepoint at the specified
29572 @item pc-inside-range
29573 Two addresses are required as parameters. Finds next trace
29574 frame that corresponds to a tracepoint at an address inside the
29575 specified range. Both bounds are considered to be inside the range.
29577 @item pc-outside-range
29578 Two addresses are required as parameters. Finds
29579 next trace frame that corresponds to a tracepoint at an address outside
29580 the specified range. Both bounds are considered to be inside the range.
29583 Line specification is required as parameter. @xref{Specify Location}.
29584 Finds next trace frame that corresponds to a tracepoint at
29585 the specified location.
29589 If @samp{none} was passed as @var{mode}, the response does not
29590 have fields. Otherwise, the response may have the following fields:
29594 This field has either @samp{0} or @samp{1} as the value, depending
29595 on whether a matching tracepoint was found.
29598 The index of the found traceframe. This field is present iff
29599 the @samp{found} field has value of @samp{1}.
29602 The index of the found tracepoint. This field is present iff
29603 the @samp{found} field has value of @samp{1}.
29606 The information about the frame corresponding to the found trace
29607 frame. This field is present only if a trace frame was found.
29608 @xref{GDB/MI Frame Information}, for description of this field.
29612 @subsubheading @value{GDBN} Command
29614 The corresponding @value{GDBN} command is @samp{tfind}.
29616 @subheading -trace-define-variable
29617 @findex -trace-define-variable
29619 @subsubheading Synopsis
29622 -trace-define-variable @var{name} [ @var{value} ]
29625 Create trace variable @var{name} if it does not exist. If
29626 @var{value} is specified, sets the initial value of the specified
29627 trace variable to that value. Note that the @var{name} should start
29628 with the @samp{$} character.
29630 @subsubheading @value{GDBN} Command
29632 The corresponding @value{GDBN} command is @samp{tvariable}.
29634 @subheading The @code{-trace-frame-collected} Command
29635 @findex -trace-frame-collected
29637 @subsubheading Synopsis
29640 -trace-frame-collected
29641 [--var-print-values @var{var_pval}]
29642 [--comp-print-values @var{comp_pval}]
29643 [--registers-format @var{regformat}]
29644 [--memory-contents]
29647 This command returns the set of collected objects, register names,
29648 trace state variable names, memory ranges and computed expressions
29649 that have been collected at a particular trace frame. The optional
29650 parameters to the command affect the output format in different ways.
29651 See the output description table below for more details.
29653 The reported names can be used in the normal manner to create
29654 varobjs and inspect the objects themselves. The items returned by
29655 this command are categorized so that it is clear which is a variable,
29656 which is a register, which is a trace state variable, which is a
29657 memory range and which is a computed expression.
29659 For instance, if the actions were
29661 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
29662 collect *(int*)0xaf02bef0@@40
29666 the object collected in its entirety would be @code{myVar}. The
29667 object @code{myArray} would be partially collected, because only the
29668 element at index @code{myIndex} would be collected. The remaining
29669 objects would be computed expressions.
29671 An example output would be:
29675 -trace-frame-collected
29677 explicit-variables=[@{name="myVar",value="1"@}],
29678 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
29679 @{name="myObj.field",value="0"@},
29680 @{name="myPtr->field",value="1"@},
29681 @{name="myCount + 2",value="3"@},
29682 @{name="$tvar1 + 1",value="43970027"@}],
29683 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
29684 @{number="1",value="0x0"@},
29685 @{number="2",value="0x4"@},
29687 @{number="125",value="0x0"@}],
29688 tvars=[@{name="$tvar1",current="43970026"@}],
29689 memory=[@{address="0x0000000000602264",length="4"@},
29690 @{address="0x0000000000615bc0",length="4"@}]
29697 @item explicit-variables
29698 The set of objects that have been collected in their entirety (as
29699 opposed to collecting just a few elements of an array or a few struct
29700 members). For each object, its name and value are printed.
29701 The @code{--var-print-values} option affects how or whether the value
29702 field is output. If @var{var_pval} is 0, then print only the names;
29703 if it is 1, print also their values; and if it is 2, print the name,
29704 type and value for simple data types, and the name and type for
29705 arrays, structures and unions.
29707 @item computed-expressions
29708 The set of computed expressions that have been collected at the
29709 current trace frame. The @code{--comp-print-values} option affects
29710 this set like the @code{--var-print-values} option affects the
29711 @code{explicit-variables} set. See above.
29714 The registers that have been collected at the current trace frame.
29715 For each register collected, the name and current value are returned.
29716 The value is formatted according to the @code{--registers-format}
29717 option. See the @command{-data-list-register-values} command for a
29718 list of the allowed formats. The default is @samp{x}.
29721 The trace state variables that have been collected at the current
29722 trace frame. For each trace state variable collected, the name and
29723 current value are returned.
29726 The set of memory ranges that have been collected at the current trace
29727 frame. Its content is a list of tuples. Each tuple represents a
29728 collected memory range and has the following fields:
29732 The start address of the memory range, as hexadecimal literal.
29735 The length of the memory range, as decimal literal.
29738 The contents of the memory block, in hex. This field is only present
29739 if the @code{--memory-contents} option is specified.
29745 @subsubheading @value{GDBN} Command
29747 There is no corresponding @value{GDBN} command.
29749 @subsubheading Example
29751 @subheading -trace-list-variables
29752 @findex -trace-list-variables
29754 @subsubheading Synopsis
29757 -trace-list-variables
29760 Return a table of all defined trace variables. Each element of the
29761 table has the following fields:
29765 The name of the trace variable. This field is always present.
29768 The initial value. This is a 64-bit signed integer. This
29769 field is always present.
29772 The value the trace variable has at the moment. This is a 64-bit
29773 signed integer. This field is absent iff current value is
29774 not defined, for example if the trace was never run, or is
29779 @subsubheading @value{GDBN} Command
29781 The corresponding @value{GDBN} command is @samp{tvariables}.
29783 @subsubheading Example
29787 -trace-list-variables
29788 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29789 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29790 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29791 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29792 body=[variable=@{name="$trace_timestamp",initial="0"@}
29793 variable=@{name="$foo",initial="10",current="15"@}]@}
29797 @subheading -trace-save
29798 @findex -trace-save
29800 @subsubheading Synopsis
29803 -trace-save [-r ] @var{filename}
29806 Saves the collected trace data to @var{filename}. Without the
29807 @samp{-r} option, the data is downloaded from the target and saved
29808 in a local file. With the @samp{-r} option the target is asked
29809 to perform the save.
29811 @subsubheading @value{GDBN} Command
29813 The corresponding @value{GDBN} command is @samp{tsave}.
29816 @subheading -trace-start
29817 @findex -trace-start
29819 @subsubheading Synopsis
29825 Starts a tracing experiments. The result of this command does not
29828 @subsubheading @value{GDBN} Command
29830 The corresponding @value{GDBN} command is @samp{tstart}.
29832 @subheading -trace-status
29833 @findex -trace-status
29835 @subsubheading Synopsis
29841 Obtains the status of a tracing experiment. The result may include
29842 the following fields:
29847 May have a value of either @samp{0}, when no tracing operations are
29848 supported, @samp{1}, when all tracing operations are supported, or
29849 @samp{file} when examining trace file. In the latter case, examining
29850 of trace frame is possible but new tracing experiement cannot be
29851 started. This field is always present.
29854 May have a value of either @samp{0} or @samp{1} depending on whether
29855 tracing experiement is in progress on target. This field is present
29856 if @samp{supported} field is not @samp{0}.
29859 Report the reason why the tracing was stopped last time. This field
29860 may be absent iff tracing was never stopped on target yet. The
29861 value of @samp{request} means the tracing was stopped as result of
29862 the @code{-trace-stop} command. The value of @samp{overflow} means
29863 the tracing buffer is full. The value of @samp{disconnection} means
29864 tracing was automatically stopped when @value{GDBN} has disconnected.
29865 The value of @samp{passcount} means tracing was stopped when a
29866 tracepoint was passed a maximal number of times for that tracepoint.
29867 This field is present if @samp{supported} field is not @samp{0}.
29869 @item stopping-tracepoint
29870 The number of tracepoint whose passcount as exceeded. This field is
29871 present iff the @samp{stop-reason} field has the value of
29875 @itemx frames-created
29876 The @samp{frames} field is a count of the total number of trace frames
29877 in the trace buffer, while @samp{frames-created} is the total created
29878 during the run, including ones that were discarded, such as when a
29879 circular trace buffer filled up. Both fields are optional.
29883 These fields tell the current size of the tracing buffer and the
29884 remaining space. These fields are optional.
29887 The value of the circular trace buffer flag. @code{1} means that the
29888 trace buffer is circular and old trace frames will be discarded if
29889 necessary to make room, @code{0} means that the trace buffer is linear
29893 The value of the disconnected tracing flag. @code{1} means that
29894 tracing will continue after @value{GDBN} disconnects, @code{0} means
29895 that the trace run will stop.
29898 The filename of the trace file being examined. This field is
29899 optional, and only present when examining a trace file.
29903 @subsubheading @value{GDBN} Command
29905 The corresponding @value{GDBN} command is @samp{tstatus}.
29907 @subheading -trace-stop
29908 @findex -trace-stop
29910 @subsubheading Synopsis
29916 Stops a tracing experiment. The result of this command has the same
29917 fields as @code{-trace-status}, except that the @samp{supported} and
29918 @samp{running} fields are not output.
29920 @subsubheading @value{GDBN} Command
29922 The corresponding @value{GDBN} command is @samp{tstop}.
29925 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29926 @node GDB/MI Symbol Query
29927 @section @sc{gdb/mi} Symbol Query Commands
29931 @subheading The @code{-symbol-info-address} Command
29932 @findex -symbol-info-address
29934 @subsubheading Synopsis
29937 -symbol-info-address @var{symbol}
29940 Describe where @var{symbol} is stored.
29942 @subsubheading @value{GDBN} Command
29944 The corresponding @value{GDBN} command is @samp{info address}.
29946 @subsubheading Example
29950 @subheading The @code{-symbol-info-file} Command
29951 @findex -symbol-info-file
29953 @subsubheading Synopsis
29959 Show the file for the symbol.
29961 @subsubheading @value{GDBN} Command
29963 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29964 @samp{gdb_find_file}.
29966 @subsubheading Example
29970 @subheading The @code{-symbol-info-function} Command
29971 @findex -symbol-info-function
29973 @subsubheading Synopsis
29976 -symbol-info-function
29979 Show which function the symbol lives in.
29981 @subsubheading @value{GDBN} Command
29983 @samp{gdb_get_function} in @code{gdbtk}.
29985 @subsubheading Example
29989 @subheading The @code{-symbol-info-line} Command
29990 @findex -symbol-info-line
29992 @subsubheading Synopsis
29998 Show the core addresses of the code for a source line.
30000 @subsubheading @value{GDBN} Command
30002 The corresponding @value{GDBN} command is @samp{info line}.
30003 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30005 @subsubheading Example
30009 @subheading The @code{-symbol-info-symbol} Command
30010 @findex -symbol-info-symbol
30012 @subsubheading Synopsis
30015 -symbol-info-symbol @var{addr}
30018 Describe what symbol is at location @var{addr}.
30020 @subsubheading @value{GDBN} Command
30022 The corresponding @value{GDBN} command is @samp{info symbol}.
30024 @subsubheading Example
30028 @subheading The @code{-symbol-list-functions} Command
30029 @findex -symbol-list-functions
30031 @subsubheading Synopsis
30034 -symbol-list-functions
30037 List the functions in the executable.
30039 @subsubheading @value{GDBN} Command
30041 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30042 @samp{gdb_search} in @code{gdbtk}.
30044 @subsubheading Example
30049 @subheading The @code{-symbol-list-lines} Command
30050 @findex -symbol-list-lines
30052 @subsubheading Synopsis
30055 -symbol-list-lines @var{filename}
30058 Print the list of lines that contain code and their associated program
30059 addresses for the given source filename. The entries are sorted in
30060 ascending PC order.
30062 @subsubheading @value{GDBN} Command
30064 There is no corresponding @value{GDBN} command.
30066 @subsubheading Example
30069 -symbol-list-lines basics.c
30070 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30076 @subheading The @code{-symbol-list-types} Command
30077 @findex -symbol-list-types
30079 @subsubheading Synopsis
30085 List all the type names.
30087 @subsubheading @value{GDBN} Command
30089 The corresponding commands are @samp{info types} in @value{GDBN},
30090 @samp{gdb_search} in @code{gdbtk}.
30092 @subsubheading Example
30096 @subheading The @code{-symbol-list-variables} Command
30097 @findex -symbol-list-variables
30099 @subsubheading Synopsis
30102 -symbol-list-variables
30105 List all the global and static variable names.
30107 @subsubheading @value{GDBN} Command
30109 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30111 @subsubheading Example
30115 @subheading The @code{-symbol-locate} Command
30116 @findex -symbol-locate
30118 @subsubheading Synopsis
30124 @subsubheading @value{GDBN} Command
30126 @samp{gdb_loc} in @code{gdbtk}.
30128 @subsubheading Example
30132 @subheading The @code{-symbol-type} Command
30133 @findex -symbol-type
30135 @subsubheading Synopsis
30138 -symbol-type @var{variable}
30141 Show type of @var{variable}.
30143 @subsubheading @value{GDBN} Command
30145 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30146 @samp{gdb_obj_variable}.
30148 @subsubheading Example
30153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30154 @node GDB/MI File Commands
30155 @section @sc{gdb/mi} File Commands
30157 This section describes the GDB/MI commands to specify executable file names
30158 and to read in and obtain symbol table information.
30160 @subheading The @code{-file-exec-and-symbols} Command
30161 @findex -file-exec-and-symbols
30163 @subsubheading Synopsis
30166 -file-exec-and-symbols @var{file}
30169 Specify the executable file to be debugged. This file is the one from
30170 which the symbol table is also read. If no file is specified, the
30171 command clears the executable and symbol information. If breakpoints
30172 are set when using this command with no arguments, @value{GDBN} will produce
30173 error messages. Otherwise, no output is produced, except a completion
30176 @subsubheading @value{GDBN} Command
30178 The corresponding @value{GDBN} command is @samp{file}.
30180 @subsubheading Example
30184 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30190 @subheading The @code{-file-exec-file} Command
30191 @findex -file-exec-file
30193 @subsubheading Synopsis
30196 -file-exec-file @var{file}
30199 Specify the executable file to be debugged. Unlike
30200 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30201 from this file. If used without argument, @value{GDBN} clears the information
30202 about the executable file. No output is produced, except a completion
30205 @subsubheading @value{GDBN} Command
30207 The corresponding @value{GDBN} command is @samp{exec-file}.
30209 @subsubheading Example
30213 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30220 @subheading The @code{-file-list-exec-sections} Command
30221 @findex -file-list-exec-sections
30223 @subsubheading Synopsis
30226 -file-list-exec-sections
30229 List the sections of the current executable file.
30231 @subsubheading @value{GDBN} Command
30233 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30234 information as this command. @code{gdbtk} has a corresponding command
30235 @samp{gdb_load_info}.
30237 @subsubheading Example
30242 @subheading The @code{-file-list-exec-source-file} Command
30243 @findex -file-list-exec-source-file
30245 @subsubheading Synopsis
30248 -file-list-exec-source-file
30251 List the line number, the current source file, and the absolute path
30252 to the current source file for the current executable. The macro
30253 information field has a value of @samp{1} or @samp{0} depending on
30254 whether or not the file includes preprocessor macro information.
30256 @subsubheading @value{GDBN} Command
30258 The @value{GDBN} equivalent is @samp{info source}
30260 @subsubheading Example
30264 123-file-list-exec-source-file
30265 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30270 @subheading The @code{-file-list-exec-source-files} Command
30271 @findex -file-list-exec-source-files
30273 @subsubheading Synopsis
30276 -file-list-exec-source-files
30279 List the source files for the current executable.
30281 It will always output both the filename and fullname (absolute file
30282 name) of a source file.
30284 @subsubheading @value{GDBN} Command
30286 The @value{GDBN} equivalent is @samp{info sources}.
30287 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30289 @subsubheading Example
30292 -file-list-exec-source-files
30294 @{file=foo.c,fullname=/home/foo.c@},
30295 @{file=/home/bar.c,fullname=/home/bar.c@},
30296 @{file=gdb_could_not_find_fullpath.c@}]
30301 @subheading The @code{-file-list-shared-libraries} Command
30302 @findex -file-list-shared-libraries
30304 @subsubheading Synopsis
30307 -file-list-shared-libraries
30310 List the shared libraries in the program.
30312 @subsubheading @value{GDBN} Command
30314 The corresponding @value{GDBN} command is @samp{info shared}.
30316 @subsubheading Example
30320 @subheading The @code{-file-list-symbol-files} Command
30321 @findex -file-list-symbol-files
30323 @subsubheading Synopsis
30326 -file-list-symbol-files
30331 @subsubheading @value{GDBN} Command
30333 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30335 @subsubheading Example
30340 @subheading The @code{-file-symbol-file} Command
30341 @findex -file-symbol-file
30343 @subsubheading Synopsis
30346 -file-symbol-file @var{file}
30349 Read symbol table info from the specified @var{file} argument. When
30350 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30351 produced, except for a completion notification.
30353 @subsubheading @value{GDBN} Command
30355 The corresponding @value{GDBN} command is @samp{symbol-file}.
30357 @subsubheading Example
30361 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30368 @node GDB/MI Memory Overlay Commands
30369 @section @sc{gdb/mi} Memory Overlay Commands
30371 The memory overlay commands are not implemented.
30373 @c @subheading -overlay-auto
30375 @c @subheading -overlay-list-mapping-state
30377 @c @subheading -overlay-list-overlays
30379 @c @subheading -overlay-map
30381 @c @subheading -overlay-off
30383 @c @subheading -overlay-on
30385 @c @subheading -overlay-unmap
30387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30388 @node GDB/MI Signal Handling Commands
30389 @section @sc{gdb/mi} Signal Handling Commands
30391 Signal handling commands are not implemented.
30393 @c @subheading -signal-handle
30395 @c @subheading -signal-list-handle-actions
30397 @c @subheading -signal-list-signal-types
30401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30402 @node GDB/MI Target Manipulation
30403 @section @sc{gdb/mi} Target Manipulation Commands
30406 @subheading The @code{-target-attach} Command
30407 @findex -target-attach
30409 @subsubheading Synopsis
30412 -target-attach @var{pid} | @var{gid} | @var{file}
30415 Attach to a process @var{pid} or a file @var{file} outside of
30416 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30417 group, the id previously returned by
30418 @samp{-list-thread-groups --available} must be used.
30420 @subsubheading @value{GDBN} Command
30422 The corresponding @value{GDBN} command is @samp{attach}.
30424 @subsubheading Example
30428 =thread-created,id="1"
30429 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30435 @subheading The @code{-target-compare-sections} Command
30436 @findex -target-compare-sections
30438 @subsubheading Synopsis
30441 -target-compare-sections [ @var{section} ]
30444 Compare data of section @var{section} on target to the exec file.
30445 Without the argument, all sections are compared.
30447 @subsubheading @value{GDBN} Command
30449 The @value{GDBN} equivalent is @samp{compare-sections}.
30451 @subsubheading Example
30456 @subheading The @code{-target-detach} Command
30457 @findex -target-detach
30459 @subsubheading Synopsis
30462 -target-detach [ @var{pid} | @var{gid} ]
30465 Detach from the remote target which normally resumes its execution.
30466 If either @var{pid} or @var{gid} is specified, detaches from either
30467 the specified process, or specified thread group. There's no output.
30469 @subsubheading @value{GDBN} Command
30471 The corresponding @value{GDBN} command is @samp{detach}.
30473 @subsubheading Example
30483 @subheading The @code{-target-disconnect} Command
30484 @findex -target-disconnect
30486 @subsubheading Synopsis
30492 Disconnect from the remote target. There's no output and the target is
30493 generally not resumed.
30495 @subsubheading @value{GDBN} Command
30497 The corresponding @value{GDBN} command is @samp{disconnect}.
30499 @subsubheading Example
30509 @subheading The @code{-target-download} Command
30510 @findex -target-download
30512 @subsubheading Synopsis
30518 Loads the executable onto the remote target.
30519 It prints out an update message every half second, which includes the fields:
30523 The name of the section.
30525 The size of what has been sent so far for that section.
30527 The size of the section.
30529 The total size of what was sent so far (the current and the previous sections).
30531 The size of the overall executable to download.
30535 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30536 @sc{gdb/mi} Output Syntax}).
30538 In addition, it prints the name and size of the sections, as they are
30539 downloaded. These messages include the following fields:
30543 The name of the section.
30545 The size of the section.
30547 The size of the overall executable to download.
30551 At the end, a summary is printed.
30553 @subsubheading @value{GDBN} Command
30555 The corresponding @value{GDBN} command is @samp{load}.
30557 @subsubheading Example
30559 Note: each status message appears on a single line. Here the messages
30560 have been broken down so that they can fit onto a page.
30565 +download,@{section=".text",section-size="6668",total-size="9880"@}
30566 +download,@{section=".text",section-sent="512",section-size="6668",
30567 total-sent="512",total-size="9880"@}
30568 +download,@{section=".text",section-sent="1024",section-size="6668",
30569 total-sent="1024",total-size="9880"@}
30570 +download,@{section=".text",section-sent="1536",section-size="6668",
30571 total-sent="1536",total-size="9880"@}
30572 +download,@{section=".text",section-sent="2048",section-size="6668",
30573 total-sent="2048",total-size="9880"@}
30574 +download,@{section=".text",section-sent="2560",section-size="6668",
30575 total-sent="2560",total-size="9880"@}
30576 +download,@{section=".text",section-sent="3072",section-size="6668",
30577 total-sent="3072",total-size="9880"@}
30578 +download,@{section=".text",section-sent="3584",section-size="6668",
30579 total-sent="3584",total-size="9880"@}
30580 +download,@{section=".text",section-sent="4096",section-size="6668",
30581 total-sent="4096",total-size="9880"@}
30582 +download,@{section=".text",section-sent="4608",section-size="6668",
30583 total-sent="4608",total-size="9880"@}
30584 +download,@{section=".text",section-sent="5120",section-size="6668",
30585 total-sent="5120",total-size="9880"@}
30586 +download,@{section=".text",section-sent="5632",section-size="6668",
30587 total-sent="5632",total-size="9880"@}
30588 +download,@{section=".text",section-sent="6144",section-size="6668",
30589 total-sent="6144",total-size="9880"@}
30590 +download,@{section=".text",section-sent="6656",section-size="6668",
30591 total-sent="6656",total-size="9880"@}
30592 +download,@{section=".init",section-size="28",total-size="9880"@}
30593 +download,@{section=".fini",section-size="28",total-size="9880"@}
30594 +download,@{section=".data",section-size="3156",total-size="9880"@}
30595 +download,@{section=".data",section-sent="512",section-size="3156",
30596 total-sent="7236",total-size="9880"@}
30597 +download,@{section=".data",section-sent="1024",section-size="3156",
30598 total-sent="7748",total-size="9880"@}
30599 +download,@{section=".data",section-sent="1536",section-size="3156",
30600 total-sent="8260",total-size="9880"@}
30601 +download,@{section=".data",section-sent="2048",section-size="3156",
30602 total-sent="8772",total-size="9880"@}
30603 +download,@{section=".data",section-sent="2560",section-size="3156",
30604 total-sent="9284",total-size="9880"@}
30605 +download,@{section=".data",section-sent="3072",section-size="3156",
30606 total-sent="9796",total-size="9880"@}
30607 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30614 @subheading The @code{-target-exec-status} Command
30615 @findex -target-exec-status
30617 @subsubheading Synopsis
30620 -target-exec-status
30623 Provide information on the state of the target (whether it is running or
30624 not, for instance).
30626 @subsubheading @value{GDBN} Command
30628 There's no equivalent @value{GDBN} command.
30630 @subsubheading Example
30634 @subheading The @code{-target-list-available-targets} Command
30635 @findex -target-list-available-targets
30637 @subsubheading Synopsis
30640 -target-list-available-targets
30643 List the possible targets to connect to.
30645 @subsubheading @value{GDBN} Command
30647 The corresponding @value{GDBN} command is @samp{help target}.
30649 @subsubheading Example
30653 @subheading The @code{-target-list-current-targets} Command
30654 @findex -target-list-current-targets
30656 @subsubheading Synopsis
30659 -target-list-current-targets
30662 Describe the current target.
30664 @subsubheading @value{GDBN} Command
30666 The corresponding information is printed by @samp{info file} (among
30669 @subsubheading Example
30673 @subheading The @code{-target-list-parameters} Command
30674 @findex -target-list-parameters
30676 @subsubheading Synopsis
30679 -target-list-parameters
30685 @subsubheading @value{GDBN} Command
30689 @subsubheading Example
30693 @subheading The @code{-target-select} Command
30694 @findex -target-select
30696 @subsubheading Synopsis
30699 -target-select @var{type} @var{parameters @dots{}}
30702 Connect @value{GDBN} to the remote target. This command takes two args:
30706 The type of target, for instance @samp{remote}, etc.
30707 @item @var{parameters}
30708 Device names, host names and the like. @xref{Target Commands, ,
30709 Commands for Managing Targets}, for more details.
30712 The output is a connection notification, followed by the address at
30713 which the target program is, in the following form:
30716 ^connected,addr="@var{address}",func="@var{function name}",
30717 args=[@var{arg list}]
30720 @subsubheading @value{GDBN} Command
30722 The corresponding @value{GDBN} command is @samp{target}.
30724 @subsubheading Example
30728 -target-select remote /dev/ttya
30729 ^connected,addr="0xfe00a300",func="??",args=[]
30733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30734 @node GDB/MI File Transfer Commands
30735 @section @sc{gdb/mi} File Transfer Commands
30738 @subheading The @code{-target-file-put} Command
30739 @findex -target-file-put
30741 @subsubheading Synopsis
30744 -target-file-put @var{hostfile} @var{targetfile}
30747 Copy file @var{hostfile} from the host system (the machine running
30748 @value{GDBN}) to @var{targetfile} on the target system.
30750 @subsubheading @value{GDBN} Command
30752 The corresponding @value{GDBN} command is @samp{remote put}.
30754 @subsubheading Example
30758 -target-file-put localfile remotefile
30764 @subheading The @code{-target-file-get} Command
30765 @findex -target-file-get
30767 @subsubheading Synopsis
30770 -target-file-get @var{targetfile} @var{hostfile}
30773 Copy file @var{targetfile} from the target system to @var{hostfile}
30774 on the host system.
30776 @subsubheading @value{GDBN} Command
30778 The corresponding @value{GDBN} command is @samp{remote get}.
30780 @subsubheading Example
30784 -target-file-get remotefile localfile
30790 @subheading The @code{-target-file-delete} Command
30791 @findex -target-file-delete
30793 @subsubheading Synopsis
30796 -target-file-delete @var{targetfile}
30799 Delete @var{targetfile} from the target system.
30801 @subsubheading @value{GDBN} Command
30803 The corresponding @value{GDBN} command is @samp{remote delete}.
30805 @subsubheading Example
30809 -target-file-delete remotefile
30815 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30816 @node GDB/MI Ada Exceptions Commands
30817 @section Ada Exceptions @sc{gdb/mi} Commands
30819 @subheading The @code{-info-ada-exceptions} Command
30820 @findex -info-ada-exceptions
30822 @subsubheading Synopsis
30825 -info-ada-exceptions [ @var{regexp}]
30828 List all Ada exceptions defined within the program being debugged.
30829 With a regular expression @var{regexp}, only those exceptions whose
30830 names match @var{regexp} are listed.
30832 @subsubheading @value{GDBN} Command
30834 The corresponding @value{GDBN} command is @samp{info exceptions}.
30836 @subsubheading Result
30838 The result is a table of Ada exceptions. The following columns are
30839 defined for each exception:
30843 The name of the exception.
30846 The address of the exception.
30850 @subsubheading Example
30853 -info-ada-exceptions aint
30854 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
30855 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
30856 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
30857 body=[@{name="constraint_error",address="0x0000000000613da0"@},
30858 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
30861 @subheading Catching Ada Exceptions
30863 The commands describing how to ask @value{GDBN} to stop when a program
30864 raises an exception are described at @ref{Ada Exception GDB/MI
30865 Catchpoint Commands}.
30868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30869 @node GDB/MI Support Commands
30870 @section @sc{gdb/mi} Support Commands
30872 Since new commands and features get regularly added to @sc{gdb/mi},
30873 some commands are available to help front-ends query the debugger
30874 about support for these capabilities. Similarly, it is also possible
30875 to query @value{GDBN} about target support of certain features.
30877 @subheading The @code{-info-gdb-mi-command} Command
30878 @cindex @code{-info-gdb-mi-command}
30879 @findex -info-gdb-mi-command
30881 @subsubheading Synopsis
30884 -info-gdb-mi-command @var{cmd_name}
30887 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
30889 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
30890 is technically not part of the command name (@pxref{GDB/MI Input
30891 Syntax}), and thus should be omitted in @var{cmd_name}. However,
30892 for ease of use, this command also accepts the form with the leading
30895 @subsubheading @value{GDBN} Command
30897 There is no corresponding @value{GDBN} command.
30899 @subsubheading Result
30901 The result is a tuple. There is currently only one field:
30905 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
30906 @code{"false"} otherwise.
30910 @subsubheading Example
30912 Here is an example where the @sc{gdb/mi} command does not exist:
30915 -info-gdb-mi-command unsupported-command
30916 ^done,command=@{exists="false"@}
30920 And here is an example where the @sc{gdb/mi} command is known
30924 -info-gdb-mi-command symbol-list-lines
30925 ^done,command=@{exists="true"@}
30928 @subheading The @code{-list-features} Command
30929 @findex -list-features
30930 @cindex supported @sc{gdb/mi} features, list
30932 Returns a list of particular features of the MI protocol that
30933 this version of gdb implements. A feature can be a command,
30934 or a new field in an output of some command, or even an
30935 important bugfix. While a frontend can sometimes detect presence
30936 of a feature at runtime, it is easier to perform detection at debugger
30939 The command returns a list of strings, with each string naming an
30940 available feature. Each returned string is just a name, it does not
30941 have any internal structure. The list of possible feature names
30947 (gdb) -list-features
30948 ^done,result=["feature1","feature2"]
30951 The current list of features is:
30954 @item frozen-varobjs
30955 Indicates support for the @code{-var-set-frozen} command, as well
30956 as possible presense of the @code{frozen} field in the output
30957 of @code{-varobj-create}.
30958 @item pending-breakpoints
30959 Indicates support for the @option{-f} option to the @code{-break-insert}
30962 Indicates Python scripting support, Python-based
30963 pretty-printing commands, and possible presence of the
30964 @samp{display_hint} field in the output of @code{-var-list-children}
30966 Indicates support for the @code{-thread-info} command.
30967 @item data-read-memory-bytes
30968 Indicates support for the @code{-data-read-memory-bytes} and the
30969 @code{-data-write-memory-bytes} commands.
30970 @item breakpoint-notifications
30971 Indicates that changes to breakpoints and breakpoints created via the
30972 CLI will be announced via async records.
30973 @item ada-task-info
30974 Indicates support for the @code{-ada-task-info} command.
30975 @item language-option
30976 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
30977 option (@pxref{Context management}).
30978 @item info-gdb-mi-command
30979 Indicates support for the @code{-info-gdb-mi-command} command.
30980 @item undefined-command-error-code
30981 Indicates support for the "undefined-command" error code in error result
30982 records, produced when trying to execute an undefined @sc{gdb/mi} command
30983 (@pxref{GDB/MI Result Records}).
30984 @item exec-run-start-option
30985 Indicates that the @code{-exec-run} command supports the @option{--start}
30986 option (@pxref{GDB/MI Program Execution}).
30989 @subheading The @code{-list-target-features} Command
30990 @findex -list-target-features
30992 Returns a list of particular features that are supported by the
30993 target. Those features affect the permitted MI commands, but
30994 unlike the features reported by the @code{-list-features} command, the
30995 features depend on which target GDB is using at the moment. Whenever
30996 a target can change, due to commands such as @code{-target-select},
30997 @code{-target-attach} or @code{-exec-run}, the list of target features
30998 may change, and the frontend should obtain it again.
31002 (gdb) -list-target-features
31003 ^done,result=["async"]
31006 The current list of features is:
31010 Indicates that the target is capable of asynchronous command
31011 execution, which means that @value{GDBN} will accept further commands
31012 while the target is running.
31015 Indicates that the target is capable of reverse execution.
31016 @xref{Reverse Execution}, for more information.
31020 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31021 @node GDB/MI Miscellaneous Commands
31022 @section Miscellaneous @sc{gdb/mi} Commands
31024 @c @subheading -gdb-complete
31026 @subheading The @code{-gdb-exit} Command
31029 @subsubheading Synopsis
31035 Exit @value{GDBN} immediately.
31037 @subsubheading @value{GDBN} Command
31039 Approximately corresponds to @samp{quit}.
31041 @subsubheading Example
31051 @subheading The @code{-exec-abort} Command
31052 @findex -exec-abort
31054 @subsubheading Synopsis
31060 Kill the inferior running program.
31062 @subsubheading @value{GDBN} Command
31064 The corresponding @value{GDBN} command is @samp{kill}.
31066 @subsubheading Example
31071 @subheading The @code{-gdb-set} Command
31074 @subsubheading Synopsis
31080 Set an internal @value{GDBN} variable.
31081 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31083 @subsubheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{set}.
31087 @subsubheading Example
31097 @subheading The @code{-gdb-show} Command
31100 @subsubheading Synopsis
31106 Show the current value of a @value{GDBN} variable.
31108 @subsubheading @value{GDBN} Command
31110 The corresponding @value{GDBN} command is @samp{show}.
31112 @subsubheading Example
31121 @c @subheading -gdb-source
31124 @subheading The @code{-gdb-version} Command
31125 @findex -gdb-version
31127 @subsubheading Synopsis
31133 Show version information for @value{GDBN}. Used mostly in testing.
31135 @subsubheading @value{GDBN} Command
31137 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31138 default shows this information when you start an interactive session.
31140 @subsubheading Example
31142 @c This example modifies the actual output from GDB to avoid overfull
31148 ~Copyright 2000 Free Software Foundation, Inc.
31149 ~GDB is free software, covered by the GNU General Public License, and
31150 ~you are welcome to change it and/or distribute copies of it under
31151 ~ certain conditions.
31152 ~Type "show copying" to see the conditions.
31153 ~There is absolutely no warranty for GDB. Type "show warranty" for
31155 ~This GDB was configured as
31156 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31161 @subheading The @code{-list-thread-groups} Command
31162 @findex -list-thread-groups
31164 @subheading Synopsis
31167 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31170 Lists thread groups (@pxref{Thread groups}). When a single thread
31171 group is passed as the argument, lists the children of that group.
31172 When several thread group are passed, lists information about those
31173 thread groups. Without any parameters, lists information about all
31174 top-level thread groups.
31176 Normally, thread groups that are being debugged are reported.
31177 With the @samp{--available} option, @value{GDBN} reports thread groups
31178 available on the target.
31180 The output of this command may have either a @samp{threads} result or
31181 a @samp{groups} result. The @samp{thread} result has a list of tuples
31182 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31183 Information}). The @samp{groups} result has a list of tuples as value,
31184 each tuple describing a thread group. If top-level groups are
31185 requested (that is, no parameter is passed), or when several groups
31186 are passed, the output always has a @samp{groups} result. The format
31187 of the @samp{group} result is described below.
31189 To reduce the number of roundtrips it's possible to list thread groups
31190 together with their children, by passing the @samp{--recurse} option
31191 and the recursion depth. Presently, only recursion depth of 1 is
31192 permitted. If this option is present, then every reported thread group
31193 will also include its children, either as @samp{group} or
31194 @samp{threads} field.
31196 In general, any combination of option and parameters is permitted, with
31197 the following caveats:
31201 When a single thread group is passed, the output will typically
31202 be the @samp{threads} result. Because threads may not contain
31203 anything, the @samp{recurse} option will be ignored.
31206 When the @samp{--available} option is passed, limited information may
31207 be available. In particular, the list of threads of a process might
31208 be inaccessible. Further, specifying specific thread groups might
31209 not give any performance advantage over listing all thread groups.
31210 The frontend should assume that @samp{-list-thread-groups --available}
31211 is always an expensive operation and cache the results.
31215 The @samp{groups} result is a list of tuples, where each tuple may
31216 have the following fields:
31220 Identifier of the thread group. This field is always present.
31221 The identifier is an opaque string; frontends should not try to
31222 convert it to an integer, even though it might look like one.
31225 The type of the thread group. At present, only @samp{process} is a
31229 The target-specific process identifier. This field is only present
31230 for thread groups of type @samp{process} and only if the process exists.
31233 The number of children this thread group has. This field may be
31234 absent for an available thread group.
31237 This field has a list of tuples as value, each tuple describing a
31238 thread. It may be present if the @samp{--recurse} option is
31239 specified, and it's actually possible to obtain the threads.
31242 This field is a list of integers, each identifying a core that one
31243 thread of the group is running on. This field may be absent if
31244 such information is not available.
31247 The name of the executable file that corresponds to this thread group.
31248 The field is only present for thread groups of type @samp{process},
31249 and only if there is a corresponding executable file.
31253 @subheading Example
31257 -list-thread-groups
31258 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31259 -list-thread-groups 17
31260 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31261 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31262 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31263 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31264 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31265 -list-thread-groups --available
31266 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31267 -list-thread-groups --available --recurse 1
31268 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31269 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31270 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31271 -list-thread-groups --available --recurse 1 17 18
31272 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31273 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31274 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31277 @subheading The @code{-info-os} Command
31280 @subsubheading Synopsis
31283 -info-os [ @var{type} ]
31286 If no argument is supplied, the command returns a table of available
31287 operating-system-specific information types. If one of these types is
31288 supplied as an argument @var{type}, then the command returns a table
31289 of data of that type.
31291 The types of information available depend on the target operating
31294 @subsubheading @value{GDBN} Command
31296 The corresponding @value{GDBN} command is @samp{info os}.
31298 @subsubheading Example
31300 When run on a @sc{gnu}/Linux system, the output will look something
31306 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
31307 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31308 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31309 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31310 body=[item=@{col0="processes",col1="Listing of all processes",
31311 col2="Processes"@},
31312 item=@{col0="procgroups",col1="Listing of all process groups",
31313 col2="Process groups"@},
31314 item=@{col0="threads",col1="Listing of all threads",
31316 item=@{col0="files",col1="Listing of all file descriptors",
31317 col2="File descriptors"@},
31318 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31320 item=@{col0="shm",col1="Listing of all shared-memory regions",
31321 col2="Shared-memory regions"@},
31322 item=@{col0="semaphores",col1="Listing of all semaphores",
31323 col2="Semaphores"@},
31324 item=@{col0="msg",col1="Listing of all message queues",
31325 col2="Message queues"@},
31326 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31327 col2="Kernel modules"@}]@}
31330 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31331 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31332 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31333 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31334 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31335 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31336 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31337 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31339 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31340 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31344 (Note that the MI output here includes a @code{"Title"} column that
31345 does not appear in command-line @code{info os}; this column is useful
31346 for MI clients that want to enumerate the types of data, such as in a
31347 popup menu, but is needless clutter on the command line, and
31348 @code{info os} omits it.)
31350 @subheading The @code{-add-inferior} Command
31351 @findex -add-inferior
31353 @subheading Synopsis
31359 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31360 inferior is not associated with any executable. Such association may
31361 be established with the @samp{-file-exec-and-symbols} command
31362 (@pxref{GDB/MI File Commands}). The command response has a single
31363 field, @samp{inferior}, whose value is the identifier of the
31364 thread group corresponding to the new inferior.
31366 @subheading Example
31371 ^done,inferior="i3"
31374 @subheading The @code{-interpreter-exec} Command
31375 @findex -interpreter-exec
31377 @subheading Synopsis
31380 -interpreter-exec @var{interpreter} @var{command}
31382 @anchor{-interpreter-exec}
31384 Execute the specified @var{command} in the given @var{interpreter}.
31386 @subheading @value{GDBN} Command
31388 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31390 @subheading Example
31394 -interpreter-exec console "break main"
31395 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31396 &"During symbol reading, bad structure-type format.\n"
31397 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31402 @subheading The @code{-inferior-tty-set} Command
31403 @findex -inferior-tty-set
31405 @subheading Synopsis
31408 -inferior-tty-set /dev/pts/1
31411 Set terminal for future runs of the program being debugged.
31413 @subheading @value{GDBN} Command
31415 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31417 @subheading Example
31421 -inferior-tty-set /dev/pts/1
31426 @subheading The @code{-inferior-tty-show} Command
31427 @findex -inferior-tty-show
31429 @subheading Synopsis
31435 Show terminal for future runs of program being debugged.
31437 @subheading @value{GDBN} Command
31439 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31441 @subheading Example
31445 -inferior-tty-set /dev/pts/1
31449 ^done,inferior_tty_terminal="/dev/pts/1"
31453 @subheading The @code{-enable-timings} Command
31454 @findex -enable-timings
31456 @subheading Synopsis
31459 -enable-timings [yes | no]
31462 Toggle the printing of the wallclock, user and system times for an MI
31463 command as a field in its output. This command is to help frontend
31464 developers optimize the performance of their code. No argument is
31465 equivalent to @samp{yes}.
31467 @subheading @value{GDBN} Command
31471 @subheading Example
31479 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31480 addr="0x080484ed",func="main",file="myprog.c",
31481 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
31483 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31491 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31492 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31493 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31494 fullname="/home/nickrob/myprog.c",line="73"@}
31499 @chapter @value{GDBN} Annotations
31501 This chapter describes annotations in @value{GDBN}. Annotations were
31502 designed to interface @value{GDBN} to graphical user interfaces or other
31503 similar programs which want to interact with @value{GDBN} at a
31504 relatively high level.
31506 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31510 This is Edition @value{EDITION}, @value{DATE}.
31514 * Annotations Overview:: What annotations are; the general syntax.
31515 * Server Prefix:: Issuing a command without affecting user state.
31516 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31517 * Errors:: Annotations for error messages.
31518 * Invalidation:: Some annotations describe things now invalid.
31519 * Annotations for Running::
31520 Whether the program is running, how it stopped, etc.
31521 * Source Annotations:: Annotations describing source code.
31524 @node Annotations Overview
31525 @section What is an Annotation?
31526 @cindex annotations
31528 Annotations start with a newline character, two @samp{control-z}
31529 characters, and the name of the annotation. If there is no additional
31530 information associated with this annotation, the name of the annotation
31531 is followed immediately by a newline. If there is additional
31532 information, the name of the annotation is followed by a space, the
31533 additional information, and a newline. The additional information
31534 cannot contain newline characters.
31536 Any output not beginning with a newline and two @samp{control-z}
31537 characters denotes literal output from @value{GDBN}. Currently there is
31538 no need for @value{GDBN} to output a newline followed by two
31539 @samp{control-z} characters, but if there was such a need, the
31540 annotations could be extended with an @samp{escape} annotation which
31541 means those three characters as output.
31543 The annotation @var{level}, which is specified using the
31544 @option{--annotate} command line option (@pxref{Mode Options}), controls
31545 how much information @value{GDBN} prints together with its prompt,
31546 values of expressions, source lines, and other types of output. Level 0
31547 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31548 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31549 for programs that control @value{GDBN}, and level 2 annotations have
31550 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31551 Interface, annotate, GDB's Obsolete Annotations}).
31554 @kindex set annotate
31555 @item set annotate @var{level}
31556 The @value{GDBN} command @code{set annotate} sets the level of
31557 annotations to the specified @var{level}.
31559 @item show annotate
31560 @kindex show annotate
31561 Show the current annotation level.
31564 This chapter describes level 3 annotations.
31566 A simple example of starting up @value{GDBN} with annotations is:
31569 $ @kbd{gdb --annotate=3}
31571 Copyright 2003 Free Software Foundation, Inc.
31572 GDB is free software, covered by the GNU General Public License,
31573 and you are welcome to change it and/or distribute copies of it
31574 under certain conditions.
31575 Type "show copying" to see the conditions.
31576 There is absolutely no warranty for GDB. Type "show warranty"
31578 This GDB was configured as "i386-pc-linux-gnu"
31589 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31590 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31591 denotes a @samp{control-z} character) are annotations; the rest is
31592 output from @value{GDBN}.
31594 @node Server Prefix
31595 @section The Server Prefix
31596 @cindex server prefix
31598 If you prefix a command with @samp{server } then it will not affect
31599 the command history, nor will it affect @value{GDBN}'s notion of which
31600 command to repeat if @key{RET} is pressed on a line by itself. This
31601 means that commands can be run behind a user's back by a front-end in
31602 a transparent manner.
31604 The @code{server } prefix does not affect the recording of values into
31605 the value history; to print a value without recording it into the
31606 value history, use the @code{output} command instead of the
31607 @code{print} command.
31609 Using this prefix also disables confirmation requests
31610 (@pxref{confirmation requests}).
31613 @section Annotation for @value{GDBN} Input
31615 @cindex annotations for prompts
31616 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31617 to know when to send output, when the output from a given command is
31620 Different kinds of input each have a different @dfn{input type}. Each
31621 input type has three annotations: a @code{pre-} annotation, which
31622 denotes the beginning of any prompt which is being output, a plain
31623 annotation, which denotes the end of the prompt, and then a @code{post-}
31624 annotation which denotes the end of any echo which may (or may not) be
31625 associated with the input. For example, the @code{prompt} input type
31626 features the following annotations:
31634 The input types are
31637 @findex pre-prompt annotation
31638 @findex prompt annotation
31639 @findex post-prompt annotation
31641 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31643 @findex pre-commands annotation
31644 @findex commands annotation
31645 @findex post-commands annotation
31647 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31648 command. The annotations are repeated for each command which is input.
31650 @findex pre-overload-choice annotation
31651 @findex overload-choice annotation
31652 @findex post-overload-choice annotation
31653 @item overload-choice
31654 When @value{GDBN} wants the user to select between various overloaded functions.
31656 @findex pre-query annotation
31657 @findex query annotation
31658 @findex post-query annotation
31660 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31662 @findex pre-prompt-for-continue annotation
31663 @findex prompt-for-continue annotation
31664 @findex post-prompt-for-continue annotation
31665 @item prompt-for-continue
31666 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31667 expect this to work well; instead use @code{set height 0} to disable
31668 prompting. This is because the counting of lines is buggy in the
31669 presence of annotations.
31674 @cindex annotations for errors, warnings and interrupts
31676 @findex quit annotation
31681 This annotation occurs right before @value{GDBN} responds to an interrupt.
31683 @findex error annotation
31688 This annotation occurs right before @value{GDBN} responds to an error.
31690 Quit and error annotations indicate that any annotations which @value{GDBN} was
31691 in the middle of may end abruptly. For example, if a
31692 @code{value-history-begin} annotation is followed by a @code{error}, one
31693 cannot expect to receive the matching @code{value-history-end}. One
31694 cannot expect not to receive it either, however; an error annotation
31695 does not necessarily mean that @value{GDBN} is immediately returning all the way
31698 @findex error-begin annotation
31699 A quit or error annotation may be preceded by
31705 Any output between that and the quit or error annotation is the error
31708 Warning messages are not yet annotated.
31709 @c If we want to change that, need to fix warning(), type_error(),
31710 @c range_error(), and possibly other places.
31713 @section Invalidation Notices
31715 @cindex annotations for invalidation messages
31716 The following annotations say that certain pieces of state may have
31720 @findex frames-invalid annotation
31721 @item ^Z^Zframes-invalid
31723 The frames (for example, output from the @code{backtrace} command) may
31726 @findex breakpoints-invalid annotation
31727 @item ^Z^Zbreakpoints-invalid
31729 The breakpoints may have changed. For example, the user just added or
31730 deleted a breakpoint.
31733 @node Annotations for Running
31734 @section Running the Program
31735 @cindex annotations for running programs
31737 @findex starting annotation
31738 @findex stopping annotation
31739 When the program starts executing due to a @value{GDBN} command such as
31740 @code{step} or @code{continue},
31746 is output. When the program stops,
31752 is output. Before the @code{stopped} annotation, a variety of
31753 annotations describe how the program stopped.
31756 @findex exited annotation
31757 @item ^Z^Zexited @var{exit-status}
31758 The program exited, and @var{exit-status} is the exit status (zero for
31759 successful exit, otherwise nonzero).
31761 @findex signalled annotation
31762 @findex signal-name annotation
31763 @findex signal-name-end annotation
31764 @findex signal-string annotation
31765 @findex signal-string-end annotation
31766 @item ^Z^Zsignalled
31767 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31768 annotation continues:
31774 ^Z^Zsignal-name-end
31778 ^Z^Zsignal-string-end
31783 where @var{name} is the name of the signal, such as @code{SIGILL} or
31784 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31785 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
31786 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31787 user's benefit and have no particular format.
31789 @findex signal annotation
31791 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31792 just saying that the program received the signal, not that it was
31793 terminated with it.
31795 @findex breakpoint annotation
31796 @item ^Z^Zbreakpoint @var{number}
31797 The program hit breakpoint number @var{number}.
31799 @findex watchpoint annotation
31800 @item ^Z^Zwatchpoint @var{number}
31801 The program hit watchpoint number @var{number}.
31804 @node Source Annotations
31805 @section Displaying Source
31806 @cindex annotations for source display
31808 @findex source annotation
31809 The following annotation is used instead of displaying source code:
31812 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31815 where @var{filename} is an absolute file name indicating which source
31816 file, @var{line} is the line number within that file (where 1 is the
31817 first line in the file), @var{character} is the character position
31818 within the file (where 0 is the first character in the file) (for most
31819 debug formats this will necessarily point to the beginning of a line),
31820 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31821 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31822 @var{addr} is the address in the target program associated with the
31823 source which is being displayed. The @var{addr} is in the form @samp{0x}
31824 followed by one or more lowercase hex digits (note that this does not
31825 depend on the language).
31827 @node JIT Interface
31828 @chapter JIT Compilation Interface
31829 @cindex just-in-time compilation
31830 @cindex JIT compilation interface
31832 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31833 interface. A JIT compiler is a program or library that generates native
31834 executable code at runtime and executes it, usually in order to achieve good
31835 performance while maintaining platform independence.
31837 Programs that use JIT compilation are normally difficult to debug because
31838 portions of their code are generated at runtime, instead of being loaded from
31839 object files, which is where @value{GDBN} normally finds the program's symbols
31840 and debug information. In order to debug programs that use JIT compilation,
31841 @value{GDBN} has an interface that allows the program to register in-memory
31842 symbol files with @value{GDBN} at runtime.
31844 If you are using @value{GDBN} to debug a program that uses this interface, then
31845 it should work transparently so long as you have not stripped the binary. If
31846 you are developing a JIT compiler, then the interface is documented in the rest
31847 of this chapter. At this time, the only known client of this interface is the
31850 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31851 JIT compiler communicates with @value{GDBN} by writing data into a global
31852 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31853 attaches, it reads a linked list of symbol files from the global variable to
31854 find existing code, and puts a breakpoint in the function so that it can find
31855 out about additional code.
31858 * Declarations:: Relevant C struct declarations
31859 * Registering Code:: Steps to register code
31860 * Unregistering Code:: Steps to unregister code
31861 * Custom Debug Info:: Emit debug information in a custom format
31865 @section JIT Declarations
31867 These are the relevant struct declarations that a C program should include to
31868 implement the interface:
31878 struct jit_code_entry
31880 struct jit_code_entry *next_entry;
31881 struct jit_code_entry *prev_entry;
31882 const char *symfile_addr;
31883 uint64_t symfile_size;
31886 struct jit_descriptor
31889 /* This type should be jit_actions_t, but we use uint32_t
31890 to be explicit about the bitwidth. */
31891 uint32_t action_flag;
31892 struct jit_code_entry *relevant_entry;
31893 struct jit_code_entry *first_entry;
31896 /* GDB puts a breakpoint in this function. */
31897 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31899 /* Make sure to specify the version statically, because the
31900 debugger may check the version before we can set it. */
31901 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31904 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31905 modifications to this global data properly, which can easily be done by putting
31906 a global mutex around modifications to these structures.
31908 @node Registering Code
31909 @section Registering Code
31911 To register code with @value{GDBN}, the JIT should follow this protocol:
31915 Generate an object file in memory with symbols and other desired debug
31916 information. The file must include the virtual addresses of the sections.
31919 Create a code entry for the file, which gives the start and size of the symbol
31923 Add it to the linked list in the JIT descriptor.
31926 Point the relevant_entry field of the descriptor at the entry.
31929 Set @code{action_flag} to @code{JIT_REGISTER} and call
31930 @code{__jit_debug_register_code}.
31933 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31934 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31935 new code. However, the linked list must still be maintained in order to allow
31936 @value{GDBN} to attach to a running process and still find the symbol files.
31938 @node Unregistering Code
31939 @section Unregistering Code
31941 If code is freed, then the JIT should use the following protocol:
31945 Remove the code entry corresponding to the code from the linked list.
31948 Point the @code{relevant_entry} field of the descriptor at the code entry.
31951 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31952 @code{__jit_debug_register_code}.
31955 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31956 and the JIT will leak the memory used for the associated symbol files.
31958 @node Custom Debug Info
31959 @section Custom Debug Info
31960 @cindex custom JIT debug info
31961 @cindex JIT debug info reader
31963 Generating debug information in platform-native file formats (like ELF
31964 or COFF) may be an overkill for JIT compilers; especially if all the
31965 debug info is used for is displaying a meaningful backtrace. The
31966 issue can be resolved by having the JIT writers decide on a debug info
31967 format and also provide a reader that parses the debug info generated
31968 by the JIT compiler. This section gives a brief overview on writing
31969 such a parser. More specific details can be found in the source file
31970 @file{gdb/jit-reader.in}, which is also installed as a header at
31971 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
31973 The reader is implemented as a shared object (so this functionality is
31974 not available on platforms which don't allow loading shared objects at
31975 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
31976 @code{jit-reader-unload} are provided, to be used to load and unload
31977 the readers from a preconfigured directory. Once loaded, the shared
31978 object is used the parse the debug information emitted by the JIT
31982 * Using JIT Debug Info Readers:: How to use supplied readers correctly
31983 * Writing JIT Debug Info Readers:: Creating a debug-info reader
31986 @node Using JIT Debug Info Readers
31987 @subsection Using JIT Debug Info Readers
31988 @kindex jit-reader-load
31989 @kindex jit-reader-unload
31991 Readers can be loaded and unloaded using the @code{jit-reader-load}
31992 and @code{jit-reader-unload} commands.
31995 @item jit-reader-load @var{reader}
31996 Load the JIT reader named @var{reader}, which is a shared
31997 object specified as either an absolute or a relative file name. In
31998 the latter case, @value{GDBN} will try to load the reader from a
31999 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32000 system (here @var{libdir} is the system library directory, often
32001 @file{/usr/local/lib}).
32003 Only one reader can be active at a time; trying to load a second
32004 reader when one is already loaded will result in @value{GDBN}
32005 reporting an error. A new JIT reader can be loaded by first unloading
32006 the current one using @code{jit-reader-unload} and then invoking
32007 @code{jit-reader-load}.
32009 @item jit-reader-unload
32010 Unload the currently loaded JIT reader.
32014 @node Writing JIT Debug Info Readers
32015 @subsection Writing JIT Debug Info Readers
32016 @cindex writing JIT debug info readers
32018 As mentioned, a reader is essentially a shared object conforming to a
32019 certain ABI. This ABI is described in @file{jit-reader.h}.
32021 @file{jit-reader.h} defines the structures, macros and functions
32022 required to write a reader. It is installed (along with
32023 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32024 the system include directory.
32026 Readers need to be released under a GPL compatible license. A reader
32027 can be declared as released under such a license by placing the macro
32028 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32030 The entry point for readers is the symbol @code{gdb_init_reader},
32031 which is expected to be a function with the prototype
32033 @findex gdb_init_reader
32035 extern struct gdb_reader_funcs *gdb_init_reader (void);
32038 @cindex @code{struct gdb_reader_funcs}
32040 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32041 functions. These functions are executed to read the debug info
32042 generated by the JIT compiler (@code{read}), to unwind stack frames
32043 (@code{unwind}) and to create canonical frame IDs
32044 (@code{get_Frame_id}). It also has a callback that is called when the
32045 reader is being unloaded (@code{destroy}). The struct looks like this
32048 struct gdb_reader_funcs
32050 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32051 int reader_version;
32053 /* For use by the reader. */
32056 gdb_read_debug_info *read;
32057 gdb_unwind_frame *unwind;
32058 gdb_get_frame_id *get_frame_id;
32059 gdb_destroy_reader *destroy;
32063 @cindex @code{struct gdb_symbol_callbacks}
32064 @cindex @code{struct gdb_unwind_callbacks}
32066 The callbacks are provided with another set of callbacks by
32067 @value{GDBN} to do their job. For @code{read}, these callbacks are
32068 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32069 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32070 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32071 files and new symbol tables inside those object files. @code{struct
32072 gdb_unwind_callbacks} has callbacks to read registers off the current
32073 frame and to write out the values of the registers in the previous
32074 frame. Both have a callback (@code{target_read}) to read bytes off the
32075 target's address space.
32077 @node In-Process Agent
32078 @chapter In-Process Agent
32079 @cindex debugging agent
32080 The traditional debugging model is conceptually low-speed, but works fine,
32081 because most bugs can be reproduced in debugging-mode execution. However,
32082 as multi-core or many-core processors are becoming mainstream, and
32083 multi-threaded programs become more and more popular, there should be more
32084 and more bugs that only manifest themselves at normal-mode execution, for
32085 example, thread races, because debugger's interference with the program's
32086 timing may conceal the bugs. On the other hand, in some applications,
32087 it is not feasible for the debugger to interrupt the program's execution
32088 long enough for the developer to learn anything helpful about its behavior.
32089 If the program's correctness depends on its real-time behavior, delays
32090 introduced by a debugger might cause the program to fail, even when the
32091 code itself is correct. It is useful to be able to observe the program's
32092 behavior without interrupting it.
32094 Therefore, traditional debugging model is too intrusive to reproduce
32095 some bugs. In order to reduce the interference with the program, we can
32096 reduce the number of operations performed by debugger. The
32097 @dfn{In-Process Agent}, a shared library, is running within the same
32098 process with inferior, and is able to perform some debugging operations
32099 itself. As a result, debugger is only involved when necessary, and
32100 performance of debugging can be improved accordingly. Note that
32101 interference with program can be reduced but can't be removed completely,
32102 because the in-process agent will still stop or slow down the program.
32104 The in-process agent can interpret and execute Agent Expressions
32105 (@pxref{Agent Expressions}) during performing debugging operations. The
32106 agent expressions can be used for different purposes, such as collecting
32107 data in tracepoints, and condition evaluation in breakpoints.
32109 @anchor{Control Agent}
32110 You can control whether the in-process agent is used as an aid for
32111 debugging with the following commands:
32114 @kindex set agent on
32116 Causes the in-process agent to perform some operations on behalf of the
32117 debugger. Just which operations requested by the user will be done
32118 by the in-process agent depends on the its capabilities. For example,
32119 if you request to evaluate breakpoint conditions in the in-process agent,
32120 and the in-process agent has such capability as well, then breakpoint
32121 conditions will be evaluated in the in-process agent.
32123 @kindex set agent off
32124 @item set agent off
32125 Disables execution of debugging operations by the in-process agent. All
32126 of the operations will be performed by @value{GDBN}.
32130 Display the current setting of execution of debugging operations by
32131 the in-process agent.
32135 * In-Process Agent Protocol::
32138 @node In-Process Agent Protocol
32139 @section In-Process Agent Protocol
32140 @cindex in-process agent protocol
32142 The in-process agent is able to communicate with both @value{GDBN} and
32143 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32144 used for communications between @value{GDBN} or GDBserver and the IPA.
32145 In general, @value{GDBN} or GDBserver sends commands
32146 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32147 in-process agent replies back with the return result of the command, or
32148 some other information. The data sent to in-process agent is composed
32149 of primitive data types, such as 4-byte or 8-byte type, and composite
32150 types, which are called objects (@pxref{IPA Protocol Objects}).
32153 * IPA Protocol Objects::
32154 * IPA Protocol Commands::
32157 @node IPA Protocol Objects
32158 @subsection IPA Protocol Objects
32159 @cindex ipa protocol objects
32161 The commands sent to and results received from agent may contain some
32162 complex data types called @dfn{objects}.
32164 The in-process agent is running on the same machine with @value{GDBN}
32165 or GDBserver, so it doesn't have to handle as much differences between
32166 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32167 However, there are still some differences of two ends in two processes:
32171 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32172 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32174 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32175 GDBserver is compiled with one, and in-process agent is compiled with
32179 Here are the IPA Protocol Objects:
32183 agent expression object. It represents an agent expression
32184 (@pxref{Agent Expressions}).
32185 @anchor{agent expression object}
32187 tracepoint action object. It represents a tracepoint action
32188 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32189 memory, static trace data and to evaluate expression.
32190 @anchor{tracepoint action object}
32192 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32193 @anchor{tracepoint object}
32197 The following table describes important attributes of each IPA protocol
32200 @multitable @columnfractions .30 .20 .50
32201 @headitem Name @tab Size @tab Description
32202 @item @emph{agent expression object} @tab @tab
32203 @item length @tab 4 @tab length of bytes code
32204 @item byte code @tab @var{length} @tab contents of byte code
32205 @item @emph{tracepoint action for collecting memory} @tab @tab
32206 @item 'M' @tab 1 @tab type of tracepoint action
32207 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32208 address of the lowest byte to collect, otherwise @var{addr} is the offset
32209 of @var{basereg} for memory collecting.
32210 @item len @tab 8 @tab length of memory for collecting
32211 @item basereg @tab 4 @tab the register number containing the starting
32212 memory address for collecting.
32213 @item @emph{tracepoint action for collecting registers} @tab @tab
32214 @item 'R' @tab 1 @tab type of tracepoint action
32215 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32216 @item 'L' @tab 1 @tab type of tracepoint action
32217 @item @emph{tracepoint action for expression evaluation} @tab @tab
32218 @item 'X' @tab 1 @tab type of tracepoint action
32219 @item agent expression @tab length of @tab @ref{agent expression object}
32220 @item @emph{tracepoint object} @tab @tab
32221 @item number @tab 4 @tab number of tracepoint
32222 @item address @tab 8 @tab address of tracepoint inserted on
32223 @item type @tab 4 @tab type of tracepoint
32224 @item enabled @tab 1 @tab enable or disable of tracepoint
32225 @item step_count @tab 8 @tab step
32226 @item pass_count @tab 8 @tab pass
32227 @item numactions @tab 4 @tab number of tracepoint actions
32228 @item hit count @tab 8 @tab hit count
32229 @item trace frame usage @tab 8 @tab trace frame usage
32230 @item compiled_cond @tab 8 @tab compiled condition
32231 @item orig_size @tab 8 @tab orig size
32232 @item condition @tab 4 if condition is NULL otherwise length of
32233 @ref{agent expression object}
32234 @tab zero if condition is NULL, otherwise is
32235 @ref{agent expression object}
32236 @item actions @tab variable
32237 @tab numactions number of @ref{tracepoint action object}
32240 @node IPA Protocol Commands
32241 @subsection IPA Protocol Commands
32242 @cindex ipa protocol commands
32244 The spaces in each command are delimiters to ease reading this commands
32245 specification. They don't exist in real commands.
32249 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32250 Installs a new fast tracepoint described by @var{tracepoint_object}
32251 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32252 head of @dfn{jumppad}, which is used to jump to data collection routine
32257 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32258 @var{target_address} is address of tracepoint in the inferior.
32259 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32260 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32261 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32262 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32269 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32270 is about to kill inferiors.
32278 @item probe_marker_at:@var{address}
32279 Asks in-process agent to probe the marker at @var{address}.
32286 @item unprobe_marker_at:@var{address}
32287 Asks in-process agent to unprobe the marker at @var{address}.
32291 @chapter Reporting Bugs in @value{GDBN}
32292 @cindex bugs in @value{GDBN}
32293 @cindex reporting bugs in @value{GDBN}
32295 Your bug reports play an essential role in making @value{GDBN} reliable.
32297 Reporting a bug may help you by bringing a solution to your problem, or it
32298 may not. But in any case the principal function of a bug report is to help
32299 the entire community by making the next version of @value{GDBN} work better. Bug
32300 reports are your contribution to the maintenance of @value{GDBN}.
32302 In order for a bug report to serve its purpose, you must include the
32303 information that enables us to fix the bug.
32306 * Bug Criteria:: Have you found a bug?
32307 * Bug Reporting:: How to report bugs
32311 @section Have You Found a Bug?
32312 @cindex bug criteria
32314 If you are not sure whether you have found a bug, here are some guidelines:
32317 @cindex fatal signal
32318 @cindex debugger crash
32319 @cindex crash of debugger
32321 If the debugger gets a fatal signal, for any input whatever, that is a
32322 @value{GDBN} bug. Reliable debuggers never crash.
32324 @cindex error on valid input
32326 If @value{GDBN} produces an error message for valid input, that is a
32327 bug. (Note that if you're cross debugging, the problem may also be
32328 somewhere in the connection to the target.)
32330 @cindex invalid input
32332 If @value{GDBN} does not produce an error message for invalid input,
32333 that is a bug. However, you should note that your idea of
32334 ``invalid input'' might be our idea of ``an extension'' or ``support
32335 for traditional practice''.
32338 If you are an experienced user of debugging tools, your suggestions
32339 for improvement of @value{GDBN} are welcome in any case.
32342 @node Bug Reporting
32343 @section How to Report Bugs
32344 @cindex bug reports
32345 @cindex @value{GDBN} bugs, reporting
32347 A number of companies and individuals offer support for @sc{gnu} products.
32348 If you obtained @value{GDBN} from a support organization, we recommend you
32349 contact that organization first.
32351 You can find contact information for many support companies and
32352 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32354 @c should add a web page ref...
32357 @ifset BUGURL_DEFAULT
32358 In any event, we also recommend that you submit bug reports for
32359 @value{GDBN}. The preferred method is to submit them directly using
32360 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32361 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32364 @strong{Do not send bug reports to @samp{info-gdb}, or to
32365 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32366 not want to receive bug reports. Those that do have arranged to receive
32369 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32370 serves as a repeater. The mailing list and the newsgroup carry exactly
32371 the same messages. Often people think of posting bug reports to the
32372 newsgroup instead of mailing them. This appears to work, but it has one
32373 problem which can be crucial: a newsgroup posting often lacks a mail
32374 path back to the sender. Thus, if we need to ask for more information,
32375 we may be unable to reach you. For this reason, it is better to send
32376 bug reports to the mailing list.
32378 @ifclear BUGURL_DEFAULT
32379 In any event, we also recommend that you submit bug reports for
32380 @value{GDBN} to @value{BUGURL}.
32384 The fundamental principle of reporting bugs usefully is this:
32385 @strong{report all the facts}. If you are not sure whether to state a
32386 fact or leave it out, state it!
32388 Often people omit facts because they think they know what causes the
32389 problem and assume that some details do not matter. Thus, you might
32390 assume that the name of the variable you use in an example does not matter.
32391 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32392 stray memory reference which happens to fetch from the location where that
32393 name is stored in memory; perhaps, if the name were different, the contents
32394 of that location would fool the debugger into doing the right thing despite
32395 the bug. Play it safe and give a specific, complete example. That is the
32396 easiest thing for you to do, and the most helpful.
32398 Keep in mind that the purpose of a bug report is to enable us to fix the
32399 bug. It may be that the bug has been reported previously, but neither
32400 you nor we can know that unless your bug report is complete and
32403 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32404 bell?'' Those bug reports are useless, and we urge everyone to
32405 @emph{refuse to respond to them} except to chide the sender to report
32408 To enable us to fix the bug, you should include all these things:
32412 The version of @value{GDBN}. @value{GDBN} announces it if you start
32413 with no arguments; you can also print it at any time using @code{show
32416 Without this, we will not know whether there is any point in looking for
32417 the bug in the current version of @value{GDBN}.
32420 The type of machine you are using, and the operating system name and
32424 The details of the @value{GDBN} build-time configuration.
32425 @value{GDBN} shows these details if you invoke it with the
32426 @option{--configuration} command-line option, or if you type
32427 @code{show configuration} at @value{GDBN}'s prompt.
32430 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32431 ``@value{GCC}--2.8.1''.
32434 What compiler (and its version) was used to compile the program you are
32435 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32436 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32437 to get this information; for other compilers, see the documentation for
32441 The command arguments you gave the compiler to compile your example and
32442 observe the bug. For example, did you use @samp{-O}? To guarantee
32443 you will not omit something important, list them all. A copy of the
32444 Makefile (or the output from make) is sufficient.
32446 If we were to try to guess the arguments, we would probably guess wrong
32447 and then we might not encounter the bug.
32450 A complete input script, and all necessary source files, that will
32454 A description of what behavior you observe that you believe is
32455 incorrect. For example, ``It gets a fatal signal.''
32457 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32458 will certainly notice it. But if the bug is incorrect output, we might
32459 not notice unless it is glaringly wrong. You might as well not give us
32460 a chance to make a mistake.
32462 Even if the problem you experience is a fatal signal, you should still
32463 say so explicitly. Suppose something strange is going on, such as, your
32464 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32465 the C library on your system. (This has happened!) Your copy might
32466 crash and ours would not. If you told us to expect a crash, then when
32467 ours fails to crash, we would know that the bug was not happening for
32468 us. If you had not told us to expect a crash, then we would not be able
32469 to draw any conclusion from our observations.
32472 @cindex recording a session script
32473 To collect all this information, you can use a session recording program
32474 such as @command{script}, which is available on many Unix systems.
32475 Just run your @value{GDBN} session inside @command{script} and then
32476 include the @file{typescript} file with your bug report.
32478 Another way to record a @value{GDBN} session is to run @value{GDBN}
32479 inside Emacs and then save the entire buffer to a file.
32482 If you wish to suggest changes to the @value{GDBN} source, send us context
32483 diffs. If you even discuss something in the @value{GDBN} source, refer to
32484 it by context, not by line number.
32486 The line numbers in our development sources will not match those in your
32487 sources. Your line numbers would convey no useful information to us.
32491 Here are some things that are not necessary:
32495 A description of the envelope of the bug.
32497 Often people who encounter a bug spend a lot of time investigating
32498 which changes to the input file will make the bug go away and which
32499 changes will not affect it.
32501 This is often time consuming and not very useful, because the way we
32502 will find the bug is by running a single example under the debugger
32503 with breakpoints, not by pure deduction from a series of examples.
32504 We recommend that you save your time for something else.
32506 Of course, if you can find a simpler example to report @emph{instead}
32507 of the original one, that is a convenience for us. Errors in the
32508 output will be easier to spot, running under the debugger will take
32509 less time, and so on.
32511 However, simplification is not vital; if you do not want to do this,
32512 report the bug anyway and send us the entire test case you used.
32515 A patch for the bug.
32517 A patch for the bug does help us if it is a good one. But do not omit
32518 the necessary information, such as the test case, on the assumption that
32519 a patch is all we need. We might see problems with your patch and decide
32520 to fix the problem another way, or we might not understand it at all.
32522 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32523 construct an example that will make the program follow a certain path
32524 through the code. If you do not send us the example, we will not be able
32525 to construct one, so we will not be able to verify that the bug is fixed.
32527 And if we cannot understand what bug you are trying to fix, or why your
32528 patch should be an improvement, we will not install it. A test case will
32529 help us to understand.
32532 A guess about what the bug is or what it depends on.
32534 Such guesses are usually wrong. Even we cannot guess right about such
32535 things without first using the debugger to find the facts.
32538 @c The readline documentation is distributed with the readline code
32539 @c and consists of the two following files:
32542 @c Use -I with makeinfo to point to the appropriate directory,
32543 @c environment var TEXINPUTS with TeX.
32544 @ifclear SYSTEM_READLINE
32545 @include rluser.texi
32546 @include hsuser.texi
32550 @appendix In Memoriam
32552 The @value{GDBN} project mourns the loss of the following long-time
32557 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32558 to Free Software in general. Outside of @value{GDBN}, he was known in
32559 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32561 @item Michael Snyder
32562 Michael was one of the Global Maintainers of the @value{GDBN} project,
32563 with contributions recorded as early as 1996, until 2011. In addition
32564 to his day to day participation, he was a large driving force behind
32565 adding Reverse Debugging to @value{GDBN}.
32568 Beyond their technical contributions to the project, they were also
32569 enjoyable members of the Free Software Community. We will miss them.
32571 @node Formatting Documentation
32572 @appendix Formatting Documentation
32574 @cindex @value{GDBN} reference card
32575 @cindex reference card
32576 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32577 for printing with PostScript or Ghostscript, in the @file{gdb}
32578 subdirectory of the main source directory@footnote{In
32579 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32580 release.}. If you can use PostScript or Ghostscript with your printer,
32581 you can print the reference card immediately with @file{refcard.ps}.
32583 The release also includes the source for the reference card. You
32584 can format it, using @TeX{}, by typing:
32590 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32591 mode on US ``letter'' size paper;
32592 that is, on a sheet 11 inches wide by 8.5 inches
32593 high. You will need to specify this form of printing as an option to
32594 your @sc{dvi} output program.
32596 @cindex documentation
32598 All the documentation for @value{GDBN} comes as part of the machine-readable
32599 distribution. The documentation is written in Texinfo format, which is
32600 a documentation system that uses a single source file to produce both
32601 on-line information and a printed manual. You can use one of the Info
32602 formatting commands to create the on-line version of the documentation
32603 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32605 @value{GDBN} includes an already formatted copy of the on-line Info
32606 version of this manual in the @file{gdb} subdirectory. The main Info
32607 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32608 subordinate files matching @samp{gdb.info*} in the same directory. If
32609 necessary, you can print out these files, or read them with any editor;
32610 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32611 Emacs or the standalone @code{info} program, available as part of the
32612 @sc{gnu} Texinfo distribution.
32614 If you want to format these Info files yourself, you need one of the
32615 Info formatting programs, such as @code{texinfo-format-buffer} or
32618 If you have @code{makeinfo} installed, and are in the top level
32619 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32620 version @value{GDBVN}), you can make the Info file by typing:
32627 If you want to typeset and print copies of this manual, you need @TeX{},
32628 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32629 Texinfo definitions file.
32631 @TeX{} is a typesetting program; it does not print files directly, but
32632 produces output files called @sc{dvi} files. To print a typeset
32633 document, you need a program to print @sc{dvi} files. If your system
32634 has @TeX{} installed, chances are it has such a program. The precise
32635 command to use depends on your system; @kbd{lpr -d} is common; another
32636 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32637 require a file name without any extension or a @samp{.dvi} extension.
32639 @TeX{} also requires a macro definitions file called
32640 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32641 written in Texinfo format. On its own, @TeX{} cannot either read or
32642 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32643 and is located in the @file{gdb-@var{version-number}/texinfo}
32646 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32647 typeset and print this manual. First switch to the @file{gdb}
32648 subdirectory of the main source directory (for example, to
32649 @file{gdb-@value{GDBVN}/gdb}) and type:
32655 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32657 @node Installing GDB
32658 @appendix Installing @value{GDBN}
32659 @cindex installation
32662 * Requirements:: Requirements for building @value{GDBN}
32663 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32664 * Separate Objdir:: Compiling @value{GDBN} in another directory
32665 * Config Names:: Specifying names for hosts and targets
32666 * Configure Options:: Summary of options for configure
32667 * System-wide configuration:: Having a system-wide init file
32671 @section Requirements for Building @value{GDBN}
32672 @cindex building @value{GDBN}, requirements for
32674 Building @value{GDBN} requires various tools and packages to be available.
32675 Other packages will be used only if they are found.
32677 @heading Tools/Packages Necessary for Building @value{GDBN}
32679 @item ISO C90 compiler
32680 @value{GDBN} is written in ISO C90. It should be buildable with any
32681 working C90 compiler, e.g.@: GCC.
32685 @heading Tools/Packages Optional for Building @value{GDBN}
32689 @value{GDBN} can use the Expat XML parsing library. This library may be
32690 included with your operating system distribution; if it is not, you
32691 can get the latest version from @url{http://expat.sourceforge.net}.
32692 The @file{configure} script will search for this library in several
32693 standard locations; if it is installed in an unusual path, you can
32694 use the @option{--with-libexpat-prefix} option to specify its location.
32700 Remote protocol memory maps (@pxref{Memory Map Format})
32702 Target descriptions (@pxref{Target Descriptions})
32704 Remote shared library lists (@xref{Library List Format},
32705 or alternatively @pxref{Library List Format for SVR4 Targets})
32707 MS-Windows shared libraries (@pxref{Shared Libraries})
32709 Traceframe info (@pxref{Traceframe Info Format})
32711 Branch trace (@pxref{Branch Trace Format})
32715 @cindex compressed debug sections
32716 @value{GDBN} will use the @samp{zlib} library, if available, to read
32717 compressed debug sections. Some linkers, such as GNU gold, are capable
32718 of producing binaries with compressed debug sections. If @value{GDBN}
32719 is compiled with @samp{zlib}, it will be able to read the debug
32720 information in such binaries.
32722 The @samp{zlib} library is likely included with your operating system
32723 distribution; if it is not, you can get the latest version from
32724 @url{http://zlib.net}.
32727 @value{GDBN}'s features related to character sets (@pxref{Character
32728 Sets}) require a functioning @code{iconv} implementation. If you are
32729 on a GNU system, then this is provided by the GNU C Library. Some
32730 other systems also provide a working @code{iconv}.
32732 If @value{GDBN} is using the @code{iconv} program which is installed
32733 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32734 This is done with @option{--with-iconv-bin} which specifies the
32735 directory that contains the @code{iconv} program.
32737 On systems without @code{iconv}, you can install GNU Libiconv. If you
32738 have previously installed Libiconv, you can use the
32739 @option{--with-libiconv-prefix} option to configure.
32741 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32742 arrange to build Libiconv if a directory named @file{libiconv} appears
32743 in the top-most source directory. If Libiconv is built this way, and
32744 if the operating system does not provide a suitable @code{iconv}
32745 implementation, then the just-built library will automatically be used
32746 by @value{GDBN}. One easy way to set this up is to download GNU
32747 Libiconv, unpack it, and then rename the directory holding the
32748 Libiconv source code to @samp{libiconv}.
32751 @node Running Configure
32752 @section Invoking the @value{GDBN} @file{configure} Script
32753 @cindex configuring @value{GDBN}
32754 @value{GDBN} comes with a @file{configure} script that automates the process
32755 of preparing @value{GDBN} for installation; you can then use @code{make} to
32756 build the @code{gdb} program.
32758 @c irrelevant in info file; it's as current as the code it lives with.
32759 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32760 look at the @file{README} file in the sources; we may have improved the
32761 installation procedures since publishing this manual.}
32764 The @value{GDBN} distribution includes all the source code you need for
32765 @value{GDBN} in a single directory, whose name is usually composed by
32766 appending the version number to @samp{gdb}.
32768 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32769 @file{gdb-@value{GDBVN}} directory. That directory contains:
32772 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32773 script for configuring @value{GDBN} and all its supporting libraries
32775 @item gdb-@value{GDBVN}/gdb
32776 the source specific to @value{GDBN} itself
32778 @item gdb-@value{GDBVN}/bfd
32779 source for the Binary File Descriptor library
32781 @item gdb-@value{GDBVN}/include
32782 @sc{gnu} include files
32784 @item gdb-@value{GDBVN}/libiberty
32785 source for the @samp{-liberty} free software library
32787 @item gdb-@value{GDBVN}/opcodes
32788 source for the library of opcode tables and disassemblers
32790 @item gdb-@value{GDBVN}/readline
32791 source for the @sc{gnu} command-line interface
32793 @item gdb-@value{GDBVN}/glob
32794 source for the @sc{gnu} filename pattern-matching subroutine
32796 @item gdb-@value{GDBVN}/mmalloc
32797 source for the @sc{gnu} memory-mapped malloc package
32800 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32801 from the @file{gdb-@var{version-number}} source directory, which in
32802 this example is the @file{gdb-@value{GDBVN}} directory.
32804 First switch to the @file{gdb-@var{version-number}} source directory
32805 if you are not already in it; then run @file{configure}. Pass the
32806 identifier for the platform on which @value{GDBN} will run as an
32812 cd gdb-@value{GDBVN}
32813 ./configure @var{host}
32818 where @var{host} is an identifier such as @samp{sun4} or
32819 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32820 (You can often leave off @var{host}; @file{configure} tries to guess the
32821 correct value by examining your system.)
32823 Running @samp{configure @var{host}} and then running @code{make} builds the
32824 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32825 libraries, then @code{gdb} itself. The configured source files, and the
32826 binaries, are left in the corresponding source directories.
32829 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32830 system does not recognize this automatically when you run a different
32831 shell, you may need to run @code{sh} on it explicitly:
32834 sh configure @var{host}
32837 If you run @file{configure} from a directory that contains source
32838 directories for multiple libraries or programs, such as the
32839 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32841 creates configuration files for every directory level underneath (unless
32842 you tell it not to, with the @samp{--norecursion} option).
32844 You should run the @file{configure} script from the top directory in the
32845 source tree, the @file{gdb-@var{version-number}} directory. If you run
32846 @file{configure} from one of the subdirectories, you will configure only
32847 that subdirectory. That is usually not what you want. In particular,
32848 if you run the first @file{configure} from the @file{gdb} subdirectory
32849 of the @file{gdb-@var{version-number}} directory, you will omit the
32850 configuration of @file{bfd}, @file{readline}, and other sibling
32851 directories of the @file{gdb} subdirectory. This leads to build errors
32852 about missing include files such as @file{bfd/bfd.h}.
32854 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32855 However, you should make sure that the shell on your path (named by
32856 the @samp{SHELL} environment variable) is publicly readable. Remember
32857 that @value{GDBN} uses the shell to start your program---some systems refuse to
32858 let @value{GDBN} debug child processes whose programs are not readable.
32860 @node Separate Objdir
32861 @section Compiling @value{GDBN} in Another Directory
32863 If you want to run @value{GDBN} versions for several host or target machines,
32864 you need a different @code{gdb} compiled for each combination of
32865 host and target. @file{configure} is designed to make this easy by
32866 allowing you to generate each configuration in a separate subdirectory,
32867 rather than in the source directory. If your @code{make} program
32868 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32869 @code{make} in each of these directories builds the @code{gdb}
32870 program specified there.
32872 To build @code{gdb} in a separate directory, run @file{configure}
32873 with the @samp{--srcdir} option to specify where to find the source.
32874 (You also need to specify a path to find @file{configure}
32875 itself from your working directory. If the path to @file{configure}
32876 would be the same as the argument to @samp{--srcdir}, you can leave out
32877 the @samp{--srcdir} option; it is assumed.)
32879 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32880 separate directory for a Sun 4 like this:
32884 cd gdb-@value{GDBVN}
32887 ../gdb-@value{GDBVN}/configure sun4
32892 When @file{configure} builds a configuration using a remote source
32893 directory, it creates a tree for the binaries with the same structure
32894 (and using the same names) as the tree under the source directory. In
32895 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32896 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32897 @file{gdb-sun4/gdb}.
32899 Make sure that your path to the @file{configure} script has just one
32900 instance of @file{gdb} in it. If your path to @file{configure} looks
32901 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32902 one subdirectory of @value{GDBN}, not the whole package. This leads to
32903 build errors about missing include files such as @file{bfd/bfd.h}.
32905 One popular reason to build several @value{GDBN} configurations in separate
32906 directories is to configure @value{GDBN} for cross-compiling (where
32907 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32908 programs that run on another machine---the @dfn{target}).
32909 You specify a cross-debugging target by
32910 giving the @samp{--target=@var{target}} option to @file{configure}.
32912 When you run @code{make} to build a program or library, you must run
32913 it in a configured directory---whatever directory you were in when you
32914 called @file{configure} (or one of its subdirectories).
32916 The @code{Makefile} that @file{configure} generates in each source
32917 directory also runs recursively. If you type @code{make} in a source
32918 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32919 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32920 will build all the required libraries, and then build GDB.
32922 When you have multiple hosts or targets configured in separate
32923 directories, you can run @code{make} on them in parallel (for example,
32924 if they are NFS-mounted on each of the hosts); they will not interfere
32928 @section Specifying Names for Hosts and Targets
32930 The specifications used for hosts and targets in the @file{configure}
32931 script are based on a three-part naming scheme, but some short predefined
32932 aliases are also supported. The full naming scheme encodes three pieces
32933 of information in the following pattern:
32936 @var{architecture}-@var{vendor}-@var{os}
32939 For example, you can use the alias @code{sun4} as a @var{host} argument,
32940 or as the value for @var{target} in a @code{--target=@var{target}}
32941 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32943 The @file{configure} script accompanying @value{GDBN} does not provide
32944 any query facility to list all supported host and target names or
32945 aliases. @file{configure} calls the Bourne shell script
32946 @code{config.sub} to map abbreviations to full names; you can read the
32947 script, if you wish, or you can use it to test your guesses on
32948 abbreviations---for example:
32951 % sh config.sub i386-linux
32953 % sh config.sub alpha-linux
32954 alpha-unknown-linux-gnu
32955 % sh config.sub hp9k700
32957 % sh config.sub sun4
32958 sparc-sun-sunos4.1.1
32959 % sh config.sub sun3
32960 m68k-sun-sunos4.1.1
32961 % sh config.sub i986v
32962 Invalid configuration `i986v': machine `i986v' not recognized
32966 @code{config.sub} is also distributed in the @value{GDBN} source
32967 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32969 @node Configure Options
32970 @section @file{configure} Options
32972 Here is a summary of the @file{configure} options and arguments that
32973 are most often useful for building @value{GDBN}. @file{configure} also has
32974 several other options not listed here. @inforef{What Configure
32975 Does,,configure.info}, for a full explanation of @file{configure}.
32978 configure @r{[}--help@r{]}
32979 @r{[}--prefix=@var{dir}@r{]}
32980 @r{[}--exec-prefix=@var{dir}@r{]}
32981 @r{[}--srcdir=@var{dirname}@r{]}
32982 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32983 @r{[}--target=@var{target}@r{]}
32988 You may introduce options with a single @samp{-} rather than
32989 @samp{--} if you prefer; but you may abbreviate option names if you use
32994 Display a quick summary of how to invoke @file{configure}.
32996 @item --prefix=@var{dir}
32997 Configure the source to install programs and files under directory
33000 @item --exec-prefix=@var{dir}
33001 Configure the source to install programs under directory
33004 @c avoid splitting the warning from the explanation:
33006 @item --srcdir=@var{dirname}
33007 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33008 @code{make} that implements the @code{VPATH} feature.}@*
33009 Use this option to make configurations in directories separate from the
33010 @value{GDBN} source directories. Among other things, you can use this to
33011 build (or maintain) several configurations simultaneously, in separate
33012 directories. @file{configure} writes configuration-specific files in
33013 the current directory, but arranges for them to use the source in the
33014 directory @var{dirname}. @file{configure} creates directories under
33015 the working directory in parallel to the source directories below
33018 @item --norecursion
33019 Configure only the directory level where @file{configure} is executed; do not
33020 propagate configuration to subdirectories.
33022 @item --target=@var{target}
33023 Configure @value{GDBN} for cross-debugging programs running on the specified
33024 @var{target}. Without this option, @value{GDBN} is configured to debug
33025 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33027 There is no convenient way to generate a list of all available targets.
33029 @item @var{host} @dots{}
33030 Configure @value{GDBN} to run on the specified @var{host}.
33032 There is no convenient way to generate a list of all available hosts.
33035 There are many other options available as well, but they are generally
33036 needed for special purposes only.
33038 @node System-wide configuration
33039 @section System-wide configuration and settings
33040 @cindex system-wide init file
33042 @value{GDBN} can be configured to have a system-wide init file;
33043 this file will be read and executed at startup (@pxref{Startup, , What
33044 @value{GDBN} does during startup}).
33046 Here is the corresponding configure option:
33049 @item --with-system-gdbinit=@var{file}
33050 Specify that the default location of the system-wide init file is
33054 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33055 it may be subject to relocation. Two possible cases:
33059 If the default location of this init file contains @file{$prefix},
33060 it will be subject to relocation. Suppose that the configure options
33061 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33062 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33063 init file is looked for as @file{$install/etc/gdbinit} instead of
33064 @file{$prefix/etc/gdbinit}.
33067 By contrast, if the default location does not contain the prefix,
33068 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33069 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33070 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33071 wherever @value{GDBN} is installed.
33074 If the configured location of the system-wide init file (as given by the
33075 @option{--with-system-gdbinit} option at configure time) is in the
33076 data-directory (as specified by @option{--with-gdb-datadir} at configure
33077 time) or in one of its subdirectories, then @value{GDBN} will look for the
33078 system-wide init file in the directory specified by the
33079 @option{--data-directory} command-line option.
33080 Note that the system-wide init file is only read once, during @value{GDBN}
33081 initialization. If the data-directory is changed after @value{GDBN} has
33082 started with the @code{set data-directory} command, the file will not be
33086 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33089 @node System-wide Configuration Scripts
33090 @subsection Installed System-wide Configuration Scripts
33091 @cindex system-wide configuration scripts
33093 The @file{system-gdbinit} directory, located inside the data-directory
33094 (as specified by @option{--with-gdb-datadir} at configure time) contains
33095 a number of scripts which can be used as system-wide init files. To
33096 automatically source those scripts at startup, @value{GDBN} should be
33097 configured with @option{--with-system-gdbinit}. Otherwise, any user
33098 should be able to source them by hand as needed.
33100 The following scripts are currently available:
33103 @item @file{elinos.py}
33105 @cindex ELinOS system-wide configuration script
33106 This script is useful when debugging a program on an ELinOS target.
33107 It takes advantage of the environment variables defined in a standard
33108 ELinOS environment in order to determine the location of the system
33109 shared libraries, and then sets the @samp{solib-absolute-prefix}
33110 and @samp{solib-search-path} variables appropriately.
33112 @item @file{wrs-linux.py}
33113 @pindex wrs-linux.py
33114 @cindex Wind River Linux system-wide configuration script
33115 This script is useful when debugging a program on a target running
33116 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33117 the host-side sysroot used by the target system.
33121 @node Maintenance Commands
33122 @appendix Maintenance Commands
33123 @cindex maintenance commands
33124 @cindex internal commands
33126 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33127 includes a number of commands intended for @value{GDBN} developers,
33128 that are not documented elsewhere in this manual. These commands are
33129 provided here for reference. (For commands that turn on debugging
33130 messages, see @ref{Debugging Output}.)
33133 @kindex maint agent
33134 @kindex maint agent-eval
33135 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33136 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33137 Translate the given @var{expression} into remote agent bytecodes.
33138 This command is useful for debugging the Agent Expression mechanism
33139 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33140 expression useful for data collection, such as by tracepoints, while
33141 @samp{maint agent-eval} produces an expression that evaluates directly
33142 to a result. For instance, a collection expression for @code{globa +
33143 globb} will include bytecodes to record four bytes of memory at each
33144 of the addresses of @code{globa} and @code{globb}, while discarding
33145 the result of the addition, while an evaluation expression will do the
33146 addition and return the sum.
33147 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33148 If not, generate remote agent bytecode for current frame PC address.
33150 @kindex maint agent-printf
33151 @item maint agent-printf @var{format},@var{expr},...
33152 Translate the given format string and list of argument expressions
33153 into remote agent bytecodes and display them as a disassembled list.
33154 This command is useful for debugging the agent version of dynamic
33155 printf (@pxref{Dynamic Printf}).
33157 @kindex maint info breakpoints
33158 @item @anchor{maint info breakpoints}maint info breakpoints
33159 Using the same format as @samp{info breakpoints}, display both the
33160 breakpoints you've set explicitly, and those @value{GDBN} is using for
33161 internal purposes. Internal breakpoints are shown with negative
33162 breakpoint numbers. The type column identifies what kind of breakpoint
33167 Normal, explicitly set breakpoint.
33170 Normal, explicitly set watchpoint.
33173 Internal breakpoint, used to handle correctly stepping through
33174 @code{longjmp} calls.
33176 @item longjmp resume
33177 Internal breakpoint at the target of a @code{longjmp}.
33180 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33183 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33186 Shared library events.
33190 @kindex maint info bfds
33191 @item maint info bfds
33192 This prints information about each @code{bfd} object that is known to
33193 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33195 @kindex set displaced-stepping
33196 @kindex show displaced-stepping
33197 @cindex displaced stepping support
33198 @cindex out-of-line single-stepping
33199 @item set displaced-stepping
33200 @itemx show displaced-stepping
33201 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33202 if the target supports it. Displaced stepping is a way to single-step
33203 over breakpoints without removing them from the inferior, by executing
33204 an out-of-line copy of the instruction that was originally at the
33205 breakpoint location. It is also known as out-of-line single-stepping.
33208 @item set displaced-stepping on
33209 If the target architecture supports it, @value{GDBN} will use
33210 displaced stepping to step over breakpoints.
33212 @item set displaced-stepping off
33213 @value{GDBN} will not use displaced stepping to step over breakpoints,
33214 even if such is supported by the target architecture.
33216 @cindex non-stop mode, and @samp{set displaced-stepping}
33217 @item set displaced-stepping auto
33218 This is the default mode. @value{GDBN} will use displaced stepping
33219 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33220 architecture supports displaced stepping.
33223 @kindex maint check-psymtabs
33224 @item maint check-psymtabs
33225 Check the consistency of currently expanded psymtabs versus symtabs.
33226 Use this to check, for example, whether a symbol is in one but not the other.
33228 @kindex maint check-symtabs
33229 @item maint check-symtabs
33230 Check the consistency of currently expanded symtabs.
33232 @kindex maint expand-symtabs
33233 @item maint expand-symtabs [@var{regexp}]
33234 Expand symbol tables.
33235 If @var{regexp} is specified, only expand symbol tables for file
33236 names matching @var{regexp}.
33238 @kindex maint cplus first_component
33239 @item maint cplus first_component @var{name}
33240 Print the first C@t{++} class/namespace component of @var{name}.
33242 @kindex maint cplus namespace
33243 @item maint cplus namespace
33244 Print the list of possible C@t{++} namespaces.
33246 @kindex maint demangle
33247 @item maint demangle @var{name}
33248 Demangle a C@t{++} or Objective-C mangled @var{name}.
33250 @kindex maint deprecate
33251 @kindex maint undeprecate
33252 @cindex deprecated commands
33253 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33254 @itemx maint undeprecate @var{command}
33255 Deprecate or undeprecate the named @var{command}. Deprecated commands
33256 cause @value{GDBN} to issue a warning when you use them. The optional
33257 argument @var{replacement} says which newer command should be used in
33258 favor of the deprecated one; if it is given, @value{GDBN} will mention
33259 the replacement as part of the warning.
33261 @kindex maint dump-me
33262 @item maint dump-me
33263 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33264 Cause a fatal signal in the debugger and force it to dump its core.
33265 This is supported only on systems which support aborting a program
33266 with the @code{SIGQUIT} signal.
33268 @kindex maint internal-error
33269 @kindex maint internal-warning
33270 @item maint internal-error @r{[}@var{message-text}@r{]}
33271 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33272 Cause @value{GDBN} to call the internal function @code{internal_error}
33273 or @code{internal_warning} and hence behave as though an internal error
33274 or internal warning has been detected. In addition to reporting the
33275 internal problem, these functions give the user the opportunity to
33276 either quit @value{GDBN} or create a core file of the current
33277 @value{GDBN} session.
33279 These commands take an optional parameter @var{message-text} that is
33280 used as the text of the error or warning message.
33282 Here's an example of using @code{internal-error}:
33285 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33286 @dots{}/maint.c:121: internal-error: testing, 1, 2
33287 A problem internal to GDB has been detected. Further
33288 debugging may prove unreliable.
33289 Quit this debugging session? (y or n) @kbd{n}
33290 Create a core file? (y or n) @kbd{n}
33294 @cindex @value{GDBN} internal error
33295 @cindex internal errors, control of @value{GDBN} behavior
33297 @kindex maint set internal-error
33298 @kindex maint show internal-error
33299 @kindex maint set internal-warning
33300 @kindex maint show internal-warning
33301 @item maint set internal-error @var{action} [ask|yes|no]
33302 @itemx maint show internal-error @var{action}
33303 @itemx maint set internal-warning @var{action} [ask|yes|no]
33304 @itemx maint show internal-warning @var{action}
33305 When @value{GDBN} reports an internal problem (error or warning) it
33306 gives the user the opportunity to both quit @value{GDBN} and create a
33307 core file of the current @value{GDBN} session. These commands let you
33308 override the default behaviour for each particular @var{action},
33309 described in the table below.
33313 You can specify that @value{GDBN} should always (yes) or never (no)
33314 quit. The default is to ask the user what to do.
33317 You can specify that @value{GDBN} should always (yes) or never (no)
33318 create a core file. The default is to ask the user what to do.
33321 @kindex maint packet
33322 @item maint packet @var{text}
33323 If @value{GDBN} is talking to an inferior via the serial protocol,
33324 then this command sends the string @var{text} to the inferior, and
33325 displays the response packet. @value{GDBN} supplies the initial
33326 @samp{$} character, the terminating @samp{#} character, and the
33329 @kindex maint print architecture
33330 @item maint print architecture @r{[}@var{file}@r{]}
33331 Print the entire architecture configuration. The optional argument
33332 @var{file} names the file where the output goes.
33334 @kindex maint print c-tdesc
33335 @item maint print c-tdesc
33336 Print the current target description (@pxref{Target Descriptions}) as
33337 a C source file. The created source file can be used in @value{GDBN}
33338 when an XML parser is not available to parse the description.
33340 @kindex maint print dummy-frames
33341 @item maint print dummy-frames
33342 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33345 (@value{GDBP}) @kbd{b add}
33347 (@value{GDBP}) @kbd{print add(2,3)}
33348 Breakpoint 2, add (a=2, b=3) at @dots{}
33350 The program being debugged stopped while in a function called from GDB.
33352 (@value{GDBP}) @kbd{maint print dummy-frames}
33353 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33354 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33355 call_lo=0x01014000 call_hi=0x01014001
33359 Takes an optional file parameter.
33361 @kindex maint print registers
33362 @kindex maint print raw-registers
33363 @kindex maint print cooked-registers
33364 @kindex maint print register-groups
33365 @kindex maint print remote-registers
33366 @item maint print registers @r{[}@var{file}@r{]}
33367 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33368 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33369 @itemx maint print register-groups @r{[}@var{file}@r{]}
33370 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33371 Print @value{GDBN}'s internal register data structures.
33373 The command @code{maint print raw-registers} includes the contents of
33374 the raw register cache; the command @code{maint print
33375 cooked-registers} includes the (cooked) value of all registers,
33376 including registers which aren't available on the target nor visible
33377 to user; the command @code{maint print register-groups} includes the
33378 groups that each register is a member of; and the command @code{maint
33379 print remote-registers} includes the remote target's register numbers
33380 and offsets in the `G' packets.
33382 These commands take an optional parameter, a file name to which to
33383 write the information.
33385 @kindex maint print reggroups
33386 @item maint print reggroups @r{[}@var{file}@r{]}
33387 Print @value{GDBN}'s internal register group data structures. The
33388 optional argument @var{file} tells to what file to write the
33391 The register groups info looks like this:
33394 (@value{GDBP}) @kbd{maint print reggroups}
33407 This command forces @value{GDBN} to flush its internal register cache.
33409 @kindex maint print objfiles
33410 @cindex info for known object files
33411 @item maint print objfiles @r{[}@var{regexp}@r{]}
33412 Print a dump of all known object files.
33413 If @var{regexp} is specified, only print object files whose names
33414 match @var{regexp}. For each object file, this command prints its name,
33415 address in memory, and all of its psymtabs and symtabs.
33417 @kindex maint print section-scripts
33418 @cindex info for known .debug_gdb_scripts-loaded scripts
33419 @item maint print section-scripts [@var{regexp}]
33420 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33421 If @var{regexp} is specified, only print scripts loaded by object files
33422 matching @var{regexp}.
33423 For each script, this command prints its name as specified in the objfile,
33424 and the full path if known.
33425 @xref{dotdebug_gdb_scripts section}.
33427 @kindex maint print statistics
33428 @cindex bcache statistics
33429 @item maint print statistics
33430 This command prints, for each object file in the program, various data
33431 about that object file followed by the byte cache (@dfn{bcache})
33432 statistics for the object file. The objfile data includes the number
33433 of minimal, partial, full, and stabs symbols, the number of types
33434 defined by the objfile, the number of as yet unexpanded psym tables,
33435 the number of line tables and string tables, and the amount of memory
33436 used by the various tables. The bcache statistics include the counts,
33437 sizes, and counts of duplicates of all and unique objects, max,
33438 average, and median entry size, total memory used and its overhead and
33439 savings, and various measures of the hash table size and chain
33442 @kindex maint print target-stack
33443 @cindex target stack description
33444 @item maint print target-stack
33445 A @dfn{target} is an interface between the debugger and a particular
33446 kind of file or process. Targets can be stacked in @dfn{strata},
33447 so that more than one target can potentially respond to a request.
33448 In particular, memory accesses will walk down the stack of targets
33449 until they find a target that is interested in handling that particular
33452 This command prints a short description of each layer that was pushed on
33453 the @dfn{target stack}, starting from the top layer down to the bottom one.
33455 @kindex maint print type
33456 @cindex type chain of a data type
33457 @item maint print type @var{expr}
33458 Print the type chain for a type specified by @var{expr}. The argument
33459 can be either a type name or a symbol. If it is a symbol, the type of
33460 that symbol is described. The type chain produced by this command is
33461 a recursive definition of the data type as stored in @value{GDBN}'s
33462 data structures, including its flags and contained types.
33464 @kindex maint set dwarf2 always-disassemble
33465 @kindex maint show dwarf2 always-disassemble
33466 @item maint set dwarf2 always-disassemble
33467 @item maint show dwarf2 always-disassemble
33468 Control the behavior of @code{info address} when using DWARF debugging
33471 The default is @code{off}, which means that @value{GDBN} should try to
33472 describe a variable's location in an easily readable format. When
33473 @code{on}, @value{GDBN} will instead display the DWARF location
33474 expression in an assembly-like format. Note that some locations are
33475 too complex for @value{GDBN} to describe simply; in this case you will
33476 always see the disassembly form.
33478 Here is an example of the resulting disassembly:
33481 (gdb) info addr argc
33482 Symbol "argc" is a complex DWARF expression:
33486 For more information on these expressions, see
33487 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33489 @kindex maint set dwarf2 max-cache-age
33490 @kindex maint show dwarf2 max-cache-age
33491 @item maint set dwarf2 max-cache-age
33492 @itemx maint show dwarf2 max-cache-age
33493 Control the DWARF 2 compilation unit cache.
33495 @cindex DWARF 2 compilation units cache
33496 In object files with inter-compilation-unit references, such as those
33497 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33498 reader needs to frequently refer to previously read compilation units.
33499 This setting controls how long a compilation unit will remain in the
33500 cache if it is not referenced. A higher limit means that cached
33501 compilation units will be stored in memory longer, and more total
33502 memory will be used. Setting it to zero disables caching, which will
33503 slow down @value{GDBN} startup, but reduce memory consumption.
33505 @kindex maint set profile
33506 @kindex maint show profile
33507 @cindex profiling GDB
33508 @item maint set profile
33509 @itemx maint show profile
33510 Control profiling of @value{GDBN}.
33512 Profiling will be disabled until you use the @samp{maint set profile}
33513 command to enable it. When you enable profiling, the system will begin
33514 collecting timing and execution count data; when you disable profiling or
33515 exit @value{GDBN}, the results will be written to a log file. Remember that
33516 if you use profiling, @value{GDBN} will overwrite the profiling log file
33517 (often called @file{gmon.out}). If you have a record of important profiling
33518 data in a @file{gmon.out} file, be sure to move it to a safe location.
33520 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33521 compiled with the @samp{-pg} compiler option.
33523 @kindex maint set show-debug-regs
33524 @kindex maint show show-debug-regs
33525 @cindex hardware debug registers
33526 @item maint set show-debug-regs
33527 @itemx maint show show-debug-regs
33528 Control whether to show variables that mirror the hardware debug
33529 registers. Use @code{on} to enable, @code{off} to disable. If
33530 enabled, the debug registers values are shown when @value{GDBN} inserts or
33531 removes a hardware breakpoint or watchpoint, and when the inferior
33532 triggers a hardware-assisted breakpoint or watchpoint.
33534 @kindex maint set show-all-tib
33535 @kindex maint show show-all-tib
33536 @item maint set show-all-tib
33537 @itemx maint show show-all-tib
33538 Control whether to show all non zero areas within a 1k block starting
33539 at thread local base, when using the @samp{info w32 thread-information-block}
33542 @kindex maint set target-async
33543 @kindex maint show target-async
33544 @item maint set target-async
33545 @itemx maint show target-async
33546 This controls whether @value{GDBN} targets operate in synchronous or
33547 asynchronous mode (@pxref{Background Execution}). Normally the
33548 default is asynchronous, if it is available; but this can be changed
33549 to more easily debug problems occurring only in synchronous mode.
33551 @kindex maint set per-command
33552 @kindex maint show per-command
33553 @item maint set per-command
33554 @itemx maint show per-command
33555 @cindex resources used by commands
33557 @value{GDBN} can display the resources used by each command.
33558 This is useful in debugging performance problems.
33561 @item maint set per-command space [on|off]
33562 @itemx maint show per-command space
33563 Enable or disable the printing of the memory used by GDB for each command.
33564 If enabled, @value{GDBN} will display how much memory each command
33565 took, following the command's own output.
33566 This can also be requested by invoking @value{GDBN} with the
33567 @option{--statistics} command-line switch (@pxref{Mode Options}).
33569 @item maint set per-command time [on|off]
33570 @itemx maint show per-command time
33571 Enable or disable the printing of the execution time of @value{GDBN}
33573 If enabled, @value{GDBN} will display how much time it
33574 took to execute each command, following the command's own output.
33575 Both CPU time and wallclock time are printed.
33576 Printing both is useful when trying to determine whether the cost is
33577 CPU or, e.g., disk/network latency.
33578 Note that the CPU time printed is for @value{GDBN} only, it does not include
33579 the execution time of the inferior because there's no mechanism currently
33580 to compute how much time was spent by @value{GDBN} and how much time was
33581 spent by the program been debugged.
33582 This can also be requested by invoking @value{GDBN} with the
33583 @option{--statistics} command-line switch (@pxref{Mode Options}).
33585 @item maint set per-command symtab [on|off]
33586 @itemx maint show per-command symtab
33587 Enable or disable the printing of basic symbol table statistics
33589 If enabled, @value{GDBN} will display the following information:
33593 number of symbol tables
33595 number of primary symbol tables
33597 number of blocks in the blockvector
33601 @kindex maint space
33602 @cindex memory used by commands
33603 @item maint space @var{value}
33604 An alias for @code{maint set per-command space}.
33605 A non-zero value enables it, zero disables it.
33608 @cindex time of command execution
33609 @item maint time @var{value}
33610 An alias for @code{maint set per-command time}.
33611 A non-zero value enables it, zero disables it.
33613 @kindex maint translate-address
33614 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33615 Find the symbol stored at the location specified by the address
33616 @var{addr} and an optional section name @var{section}. If found,
33617 @value{GDBN} prints the name of the closest symbol and an offset from
33618 the symbol's location to the specified address. This is similar to
33619 the @code{info address} command (@pxref{Symbols}), except that this
33620 command also allows to find symbols in other sections.
33622 If section was not specified, the section in which the symbol was found
33623 is also printed. For dynamically linked executables, the name of
33624 executable or shared library containing the symbol is printed as well.
33628 The following command is useful for non-interactive invocations of
33629 @value{GDBN}, such as in the test suite.
33632 @item set watchdog @var{nsec}
33633 @kindex set watchdog
33634 @cindex watchdog timer
33635 @cindex timeout for commands
33636 Set the maximum number of seconds @value{GDBN} will wait for the
33637 target operation to finish. If this time expires, @value{GDBN}
33638 reports and error and the command is aborted.
33640 @item show watchdog
33641 Show the current setting of the target wait timeout.
33644 @node Remote Protocol
33645 @appendix @value{GDBN} Remote Serial Protocol
33650 * Stop Reply Packets::
33651 * General Query Packets::
33652 * Architecture-Specific Protocol Details::
33653 * Tracepoint Packets::
33654 * Host I/O Packets::
33656 * Notification Packets::
33657 * Remote Non-Stop::
33658 * Packet Acknowledgment::
33660 * File-I/O Remote Protocol Extension::
33661 * Library List Format::
33662 * Library List Format for SVR4 Targets::
33663 * Memory Map Format::
33664 * Thread List Format::
33665 * Traceframe Info Format::
33666 * Branch Trace Format::
33672 There may be occasions when you need to know something about the
33673 protocol---for example, if there is only one serial port to your target
33674 machine, you might want your program to do something special if it
33675 recognizes a packet meant for @value{GDBN}.
33677 In the examples below, @samp{->} and @samp{<-} are used to indicate
33678 transmitted and received data, respectively.
33680 @cindex protocol, @value{GDBN} remote serial
33681 @cindex serial protocol, @value{GDBN} remote
33682 @cindex remote serial protocol
33683 All @value{GDBN} commands and responses (other than acknowledgments
33684 and notifications, see @ref{Notification Packets}) are sent as a
33685 @var{packet}. A @var{packet} is introduced with the character
33686 @samp{$}, the actual @var{packet-data}, and the terminating character
33687 @samp{#} followed by a two-digit @var{checksum}:
33690 @code{$}@var{packet-data}@code{#}@var{checksum}
33694 @cindex checksum, for @value{GDBN} remote
33696 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33697 characters between the leading @samp{$} and the trailing @samp{#} (an
33698 eight bit unsigned checksum).
33700 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33701 specification also included an optional two-digit @var{sequence-id}:
33704 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33707 @cindex sequence-id, for @value{GDBN} remote
33709 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33710 has never output @var{sequence-id}s. Stubs that handle packets added
33711 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33713 When either the host or the target machine receives a packet, the first
33714 response expected is an acknowledgment: either @samp{+} (to indicate
33715 the package was received correctly) or @samp{-} (to request
33719 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33724 The @samp{+}/@samp{-} acknowledgments can be disabled
33725 once a connection is established.
33726 @xref{Packet Acknowledgment}, for details.
33728 The host (@value{GDBN}) sends @var{command}s, and the target (the
33729 debugging stub incorporated in your program) sends a @var{response}. In
33730 the case of step and continue @var{command}s, the response is only sent
33731 when the operation has completed, and the target has again stopped all
33732 threads in all attached processes. This is the default all-stop mode
33733 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33734 execution mode; see @ref{Remote Non-Stop}, for details.
33736 @var{packet-data} consists of a sequence of characters with the
33737 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33740 @cindex remote protocol, field separator
33741 Fields within the packet should be separated using @samp{,} @samp{;} or
33742 @samp{:}. Except where otherwise noted all numbers are represented in
33743 @sc{hex} with leading zeros suppressed.
33745 Implementors should note that prior to @value{GDBN} 5.0, the character
33746 @samp{:} could not appear as the third character in a packet (as it
33747 would potentially conflict with the @var{sequence-id}).
33749 @cindex remote protocol, binary data
33750 @anchor{Binary Data}
33751 Binary data in most packets is encoded either as two hexadecimal
33752 digits per byte of binary data. This allowed the traditional remote
33753 protocol to work over connections which were only seven-bit clean.
33754 Some packets designed more recently assume an eight-bit clean
33755 connection, and use a more efficient encoding to send and receive
33758 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33759 as an escape character. Any escaped byte is transmitted as the escape
33760 character followed by the original character XORed with @code{0x20}.
33761 For example, the byte @code{0x7d} would be transmitted as the two
33762 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33763 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33764 @samp{@}}) must always be escaped. Responses sent by the stub
33765 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33766 is not interpreted as the start of a run-length encoded sequence
33769 Response @var{data} can be run-length encoded to save space.
33770 Run-length encoding replaces runs of identical characters with one
33771 instance of the repeated character, followed by a @samp{*} and a
33772 repeat count. The repeat count is itself sent encoded, to avoid
33773 binary characters in @var{data}: a value of @var{n} is sent as
33774 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33775 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33776 code 32) for a repeat count of 3. (This is because run-length
33777 encoding starts to win for counts 3 or more.) Thus, for example,
33778 @samp{0* } is a run-length encoding of ``0000'': the space character
33779 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33782 The printable characters @samp{#} and @samp{$} or with a numeric value
33783 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33784 seven repeats (@samp{$}) can be expanded using a repeat count of only
33785 five (@samp{"}). For example, @samp{00000000} can be encoded as
33788 The error response returned for some packets includes a two character
33789 error number. That number is not well defined.
33791 @cindex empty response, for unsupported packets
33792 For any @var{command} not supported by the stub, an empty response
33793 (@samp{$#00}) should be returned. That way it is possible to extend the
33794 protocol. A newer @value{GDBN} can tell if a packet is supported based
33797 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33798 commands for register access, and the @samp{m} and @samp{M} commands
33799 for memory access. Stubs that only control single-threaded targets
33800 can implement run control with the @samp{c} (continue), and @samp{s}
33801 (step) commands. Stubs that support multi-threading targets should
33802 support the @samp{vCont} command. All other commands are optional.
33807 The following table provides a complete list of all currently defined
33808 @var{command}s and their corresponding response @var{data}.
33809 @xref{File-I/O Remote Protocol Extension}, for details about the File
33810 I/O extension of the remote protocol.
33812 Each packet's description has a template showing the packet's overall
33813 syntax, followed by an explanation of the packet's meaning. We
33814 include spaces in some of the templates for clarity; these are not
33815 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33816 separate its components. For example, a template like @samp{foo
33817 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33818 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33819 @var{baz}. @value{GDBN} does not transmit a space character between the
33820 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33823 @cindex @var{thread-id}, in remote protocol
33824 @anchor{thread-id syntax}
33825 Several packets and replies include a @var{thread-id} field to identify
33826 a thread. Normally these are positive numbers with a target-specific
33827 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33828 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33831 In addition, the remote protocol supports a multiprocess feature in
33832 which the @var{thread-id} syntax is extended to optionally include both
33833 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33834 The @var{pid} (process) and @var{tid} (thread) components each have the
33835 format described above: a positive number with target-specific
33836 interpretation formatted as a big-endian hex string, literal @samp{-1}
33837 to indicate all processes or threads (respectively), or @samp{0} to
33838 indicate an arbitrary process or thread. Specifying just a process, as
33839 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33840 error to specify all processes but a specific thread, such as
33841 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33842 for those packets and replies explicitly documented to include a process
33843 ID, rather than a @var{thread-id}.
33845 The multiprocess @var{thread-id} syntax extensions are only used if both
33846 @value{GDBN} and the stub report support for the @samp{multiprocess}
33847 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33850 Note that all packet forms beginning with an upper- or lower-case
33851 letter, other than those described here, are reserved for future use.
33853 Here are the packet descriptions.
33858 @cindex @samp{!} packet
33859 @anchor{extended mode}
33860 Enable extended mode. In extended mode, the remote server is made
33861 persistent. The @samp{R} packet is used to restart the program being
33867 The remote target both supports and has enabled extended mode.
33871 @cindex @samp{?} packet
33873 Indicate the reason the target halted. The reply is the same as for
33874 step and continue. This packet has a special interpretation when the
33875 target is in non-stop mode; see @ref{Remote Non-Stop}.
33878 @xref{Stop Reply Packets}, for the reply specifications.
33880 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33881 @cindex @samp{A} packet
33882 Initialized @code{argv[]} array passed into program. @var{arglen}
33883 specifies the number of bytes in the hex encoded byte stream
33884 @var{arg}. See @code{gdbserver} for more details.
33889 The arguments were set.
33895 @cindex @samp{b} packet
33896 (Don't use this packet; its behavior is not well-defined.)
33897 Change the serial line speed to @var{baud}.
33899 JTC: @emph{When does the transport layer state change? When it's
33900 received, or after the ACK is transmitted. In either case, there are
33901 problems if the command or the acknowledgment packet is dropped.}
33903 Stan: @emph{If people really wanted to add something like this, and get
33904 it working for the first time, they ought to modify ser-unix.c to send
33905 some kind of out-of-band message to a specially-setup stub and have the
33906 switch happen "in between" packets, so that from remote protocol's point
33907 of view, nothing actually happened.}
33909 @item B @var{addr},@var{mode}
33910 @cindex @samp{B} packet
33911 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33912 breakpoint at @var{addr}.
33914 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33915 (@pxref{insert breakpoint or watchpoint packet}).
33917 @cindex @samp{bc} packet
33920 Backward continue. Execute the target system in reverse. No parameter.
33921 @xref{Reverse Execution}, for more information.
33924 @xref{Stop Reply Packets}, for the reply specifications.
33926 @cindex @samp{bs} packet
33929 Backward single step. Execute one instruction in reverse. No parameter.
33930 @xref{Reverse Execution}, for more information.
33933 @xref{Stop Reply Packets}, for the reply specifications.
33935 @item c @r{[}@var{addr}@r{]}
33936 @cindex @samp{c} packet
33937 Continue at @var{addr}, which is the address to resume. If @var{addr}
33938 is omitted, resume at current address.
33940 This packet is deprecated for multi-threading support. @xref{vCont
33944 @xref{Stop Reply Packets}, for the reply specifications.
33946 @item C @var{sig}@r{[};@var{addr}@r{]}
33947 @cindex @samp{C} packet
33948 Continue with signal @var{sig} (hex signal number). If
33949 @samp{;@var{addr}} is omitted, resume at same address.
33951 This packet is deprecated for multi-threading support. @xref{vCont
33955 @xref{Stop Reply Packets}, for the reply specifications.
33958 @cindex @samp{d} packet
33961 Don't use this packet; instead, define a general set packet
33962 (@pxref{General Query Packets}).
33966 @cindex @samp{D} packet
33967 The first form of the packet is used to detach @value{GDBN} from the
33968 remote system. It is sent to the remote target
33969 before @value{GDBN} disconnects via the @code{detach} command.
33971 The second form, including a process ID, is used when multiprocess
33972 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33973 detach only a specific process. The @var{pid} is specified as a
33974 big-endian hex string.
33984 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33985 @cindex @samp{F} packet
33986 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33987 This is part of the File-I/O protocol extension. @xref{File-I/O
33988 Remote Protocol Extension}, for the specification.
33991 @anchor{read registers packet}
33992 @cindex @samp{g} packet
33993 Read general registers.
33997 @item @var{XX@dots{}}
33998 Each byte of register data is described by two hex digits. The bytes
33999 with the register are transmitted in target byte order. The size of
34000 each register and their position within the @samp{g} packet are
34001 determined by the @value{GDBN} internal gdbarch functions
34002 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34003 specification of several standard @samp{g} packets is specified below.
34005 When reading registers from a trace frame (@pxref{Analyze Collected
34006 Data,,Using the Collected Data}), the stub may also return a string of
34007 literal @samp{x}'s in place of the register data digits, to indicate
34008 that the corresponding register has not been collected, thus its value
34009 is unavailable. For example, for an architecture with 4 registers of
34010 4 bytes each, the following reply indicates to @value{GDBN} that
34011 registers 0 and 2 have not been collected, while registers 1 and 3
34012 have been collected, and both have zero value:
34016 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34023 @item G @var{XX@dots{}}
34024 @cindex @samp{G} packet
34025 Write general registers. @xref{read registers packet}, for a
34026 description of the @var{XX@dots{}} data.
34036 @item H @var{op} @var{thread-id}
34037 @cindex @samp{H} packet
34038 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34039 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34040 should be @samp{c} for step and continue operations (note that this
34041 is deprecated, supporting the @samp{vCont} command is a better
34042 option), and @samp{g} for other operations. The thread designator
34043 @var{thread-id} has the format and interpretation described in
34044 @ref{thread-id syntax}.
34055 @c 'H': How restrictive (or permissive) is the thread model. If a
34056 @c thread is selected and stopped, are other threads allowed
34057 @c to continue to execute? As I mentioned above, I think the
34058 @c semantics of each command when a thread is selected must be
34059 @c described. For example:
34061 @c 'g': If the stub supports threads and a specific thread is
34062 @c selected, returns the register block from that thread;
34063 @c otherwise returns current registers.
34065 @c 'G' If the stub supports threads and a specific thread is
34066 @c selected, sets the registers of the register block of
34067 @c that thread; otherwise sets current registers.
34069 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34070 @anchor{cycle step packet}
34071 @cindex @samp{i} packet
34072 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34073 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34074 step starting at that address.
34077 @cindex @samp{I} packet
34078 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34082 @cindex @samp{k} packet
34085 The exact effect of this packet is not specified.
34087 For a bare-metal target, it may power cycle or reset the target
34088 system. For that reason, the @samp{k} packet has no reply.
34090 For a single-process target, it may kill that process if possible.
34092 A multiple-process target may choose to kill just one process, or all
34093 that are under @value{GDBN}'s control. For more precise control, use
34094 the vKill packet (@pxref{vKill packet}).
34096 If the target system immediately closes the connection in response to
34097 @samp{k}, @value{GDBN} does not consider the lack of packet
34098 acknowledgment to be an error, and assumes the kill was successful.
34100 If connected using @kbd{target extended-remote}, and the target does
34101 not close the connection in response to a kill request, @value{GDBN}
34102 probes the target state as if a new connection was opened
34103 (@pxref{? packet}).
34105 @item m @var{addr},@var{length}
34106 @cindex @samp{m} packet
34107 Read @var{length} bytes of memory starting at address @var{addr}.
34108 Note that @var{addr} may not be aligned to any particular boundary.
34110 The stub need not use any particular size or alignment when gathering
34111 data from memory for the response; even if @var{addr} is word-aligned
34112 and @var{length} is a multiple of the word size, the stub is free to
34113 use byte accesses, or not. For this reason, this packet may not be
34114 suitable for accessing memory-mapped I/O devices.
34115 @cindex alignment of remote memory accesses
34116 @cindex size of remote memory accesses
34117 @cindex memory, alignment and size of remote accesses
34121 @item @var{XX@dots{}}
34122 Memory contents; each byte is transmitted as a two-digit hexadecimal
34123 number. The reply may contain fewer bytes than requested if the
34124 server was able to read only part of the region of memory.
34129 @item M @var{addr},@var{length}:@var{XX@dots{}}
34130 @cindex @samp{M} packet
34131 Write @var{length} bytes of memory starting at address @var{addr}.
34132 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34133 hexadecimal number.
34140 for an error (this includes the case where only part of the data was
34145 @cindex @samp{p} packet
34146 Read the value of register @var{n}; @var{n} is in hex.
34147 @xref{read registers packet}, for a description of how the returned
34148 register value is encoded.
34152 @item @var{XX@dots{}}
34153 the register's value
34157 Indicating an unrecognized @var{query}.
34160 @item P @var{n@dots{}}=@var{r@dots{}}
34161 @anchor{write register packet}
34162 @cindex @samp{P} packet
34163 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34164 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34165 digits for each byte in the register (target byte order).
34175 @item q @var{name} @var{params}@dots{}
34176 @itemx Q @var{name} @var{params}@dots{}
34177 @cindex @samp{q} packet
34178 @cindex @samp{Q} packet
34179 General query (@samp{q}) and set (@samp{Q}). These packets are
34180 described fully in @ref{General Query Packets}.
34183 @cindex @samp{r} packet
34184 Reset the entire system.
34186 Don't use this packet; use the @samp{R} packet instead.
34189 @cindex @samp{R} packet
34190 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34191 This packet is only available in extended mode (@pxref{extended mode}).
34193 The @samp{R} packet has no reply.
34195 @item s @r{[}@var{addr}@r{]}
34196 @cindex @samp{s} packet
34197 Single step, resuming at @var{addr}. If
34198 @var{addr} is omitted, resume at same address.
34200 This packet is deprecated for multi-threading support. @xref{vCont
34204 @xref{Stop Reply Packets}, for the reply specifications.
34206 @item S @var{sig}@r{[};@var{addr}@r{]}
34207 @anchor{step with signal packet}
34208 @cindex @samp{S} packet
34209 Step with signal. This is analogous to the @samp{C} packet, but
34210 requests a single-step, rather than a normal resumption of execution.
34212 This packet is deprecated for multi-threading support. @xref{vCont
34216 @xref{Stop Reply Packets}, for the reply specifications.
34218 @item t @var{addr}:@var{PP},@var{MM}
34219 @cindex @samp{t} packet
34220 Search backwards starting at address @var{addr} for a match with pattern
34221 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34222 There must be at least 3 digits in @var{addr}.
34224 @item T @var{thread-id}
34225 @cindex @samp{T} packet
34226 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34231 thread is still alive
34237 Packets starting with @samp{v} are identified by a multi-letter name,
34238 up to the first @samp{;} or @samp{?} (or the end of the packet).
34240 @item vAttach;@var{pid}
34241 @cindex @samp{vAttach} packet
34242 Attach to a new process with the specified process ID @var{pid}.
34243 The process ID is a
34244 hexadecimal integer identifying the process. In all-stop mode, all
34245 threads in the attached process are stopped; in non-stop mode, it may be
34246 attached without being stopped if that is supported by the target.
34248 @c In non-stop mode, on a successful vAttach, the stub should set the
34249 @c current thread to a thread of the newly-attached process. After
34250 @c attaching, GDB queries for the attached process's thread ID with qC.
34251 @c Also note that, from a user perspective, whether or not the
34252 @c target is stopped on attach in non-stop mode depends on whether you
34253 @c use the foreground or background version of the attach command, not
34254 @c on what vAttach does; GDB does the right thing with respect to either
34255 @c stopping or restarting threads.
34257 This packet is only available in extended mode (@pxref{extended mode}).
34263 @item @r{Any stop packet}
34264 for success in all-stop mode (@pxref{Stop Reply Packets})
34266 for success in non-stop mode (@pxref{Remote Non-Stop})
34269 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34270 @cindex @samp{vCont} packet
34271 @anchor{vCont packet}
34272 Resume the inferior, specifying different actions for each thread.
34273 If an action is specified with no @var{thread-id}, then it is applied to any
34274 threads that don't have a specific action specified; if no default action is
34275 specified then other threads should remain stopped in all-stop mode and
34276 in their current state in non-stop mode.
34277 Specifying multiple
34278 default actions is an error; specifying no actions is also an error.
34279 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34281 Currently supported actions are:
34287 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34291 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34294 @item r @var{start},@var{end}
34295 Step once, and then keep stepping as long as the thread stops at
34296 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34297 The remote stub reports a stop reply when either the thread goes out
34298 of the range or is stopped due to an unrelated reason, such as hitting
34299 a breakpoint. @xref{range stepping}.
34301 If the range is empty (@var{start} == @var{end}), then the action
34302 becomes equivalent to the @samp{s} action. In other words,
34303 single-step once, and report the stop (even if the stepped instruction
34304 jumps to @var{start}).
34306 (A stop reply may be sent at any point even if the PC is still within
34307 the stepping range; for example, it is valid to implement this packet
34308 in a degenerate way as a single instruction step operation.)
34312 The optional argument @var{addr} normally associated with the
34313 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34314 not supported in @samp{vCont}.
34316 The @samp{t} action is only relevant in non-stop mode
34317 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34318 A stop reply should be generated for any affected thread not already stopped.
34319 When a thread is stopped by means of a @samp{t} action,
34320 the corresponding stop reply should indicate that the thread has stopped with
34321 signal @samp{0}, regardless of whether the target uses some other signal
34322 as an implementation detail.
34324 The stub must support @samp{vCont} if it reports support for
34325 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34326 this case @samp{vCont} actions can be specified to apply to all threads
34327 in a process by using the @samp{p@var{pid}.-1} form of the
34331 @xref{Stop Reply Packets}, for the reply specifications.
34334 @cindex @samp{vCont?} packet
34335 Request a list of actions supported by the @samp{vCont} packet.
34339 @item vCont@r{[};@var{action}@dots{}@r{]}
34340 The @samp{vCont} packet is supported. Each @var{action} is a supported
34341 command in the @samp{vCont} packet.
34343 The @samp{vCont} packet is not supported.
34346 @item vFile:@var{operation}:@var{parameter}@dots{}
34347 @cindex @samp{vFile} packet
34348 Perform a file operation on the target system. For details,
34349 see @ref{Host I/O Packets}.
34351 @item vFlashErase:@var{addr},@var{length}
34352 @cindex @samp{vFlashErase} packet
34353 Direct the stub to erase @var{length} bytes of flash starting at
34354 @var{addr}. The region may enclose any number of flash blocks, but
34355 its start and end must fall on block boundaries, as indicated by the
34356 flash block size appearing in the memory map (@pxref{Memory Map
34357 Format}). @value{GDBN} groups flash memory programming operations
34358 together, and sends a @samp{vFlashDone} request after each group; the
34359 stub is allowed to delay erase operation until the @samp{vFlashDone}
34360 packet is received.
34370 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34371 @cindex @samp{vFlashWrite} packet
34372 Direct the stub to write data to flash address @var{addr}. The data
34373 is passed in binary form using the same encoding as for the @samp{X}
34374 packet (@pxref{Binary Data}). The memory ranges specified by
34375 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34376 not overlap, and must appear in order of increasing addresses
34377 (although @samp{vFlashErase} packets for higher addresses may already
34378 have been received; the ordering is guaranteed only between
34379 @samp{vFlashWrite} packets). If a packet writes to an address that was
34380 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34381 target-specific method, the results are unpredictable.
34389 for vFlashWrite addressing non-flash memory
34395 @cindex @samp{vFlashDone} packet
34396 Indicate to the stub that flash programming operation is finished.
34397 The stub is permitted to delay or batch the effects of a group of
34398 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34399 @samp{vFlashDone} packet is received. The contents of the affected
34400 regions of flash memory are unpredictable until the @samp{vFlashDone}
34401 request is completed.
34403 @item vKill;@var{pid}
34404 @cindex @samp{vKill} packet
34405 @anchor{vKill packet}
34406 Kill the process with the specified process ID @var{pid}, which is a
34407 hexadecimal integer identifying the process. This packet is used in
34408 preference to @samp{k} when multiprocess protocol extensions are
34409 supported; see @ref{multiprocess extensions}.
34419 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34420 @cindex @samp{vRun} packet
34421 Run the program @var{filename}, passing it each @var{argument} on its
34422 command line. The file and arguments are hex-encoded strings. If
34423 @var{filename} is an empty string, the stub may use a default program
34424 (e.g.@: the last program run). The program is created in the stopped
34427 @c FIXME: What about non-stop mode?
34429 This packet is only available in extended mode (@pxref{extended mode}).
34435 @item @r{Any stop packet}
34436 for success (@pxref{Stop Reply Packets})
34440 @cindex @samp{vStopped} packet
34441 @xref{Notification Packets}.
34443 @item X @var{addr},@var{length}:@var{XX@dots{}}
34445 @cindex @samp{X} packet
34446 Write data to memory, where the data is transmitted in binary.
34447 Memory is specified by its address @var{addr} and number of bytes @var{length};
34448 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34458 @item z @var{type},@var{addr},@var{kind}
34459 @itemx Z @var{type},@var{addr},@var{kind}
34460 @anchor{insert breakpoint or watchpoint packet}
34461 @cindex @samp{z} packet
34462 @cindex @samp{Z} packets
34463 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34464 watchpoint starting at address @var{address} of kind @var{kind}.
34466 Each breakpoint and watchpoint packet @var{type} is documented
34469 @emph{Implementation notes: A remote target shall return an empty string
34470 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34471 remote target shall support either both or neither of a given
34472 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34473 avoid potential problems with duplicate packets, the operations should
34474 be implemented in an idempotent way.}
34476 @item z0,@var{addr},@var{kind}
34477 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
34478 @cindex @samp{z0} packet
34479 @cindex @samp{Z0} packet
34480 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34481 @var{addr} of type @var{kind}.
34483 A memory breakpoint is implemented by replacing the instruction at
34484 @var{addr} with a software breakpoint or trap instruction. The
34485 @var{kind} is target-specific and typically indicates the size of
34486 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34487 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34488 architectures have additional meanings for @var{kind};
34489 @var{cond_list} is an optional list of conditional expressions in bytecode
34490 form that should be evaluated on the target's side. These are the
34491 conditions that should be taken into consideration when deciding if
34492 the breakpoint trigger should be reported back to @var{GDBN}.
34494 The @var{cond_list} parameter is comprised of a series of expressions,
34495 concatenated without separators. Each expression has the following form:
34499 @item X @var{len},@var{expr}
34500 @var{len} is the length of the bytecode expression and @var{expr} is the
34501 actual conditional expression in bytecode form.
34505 The optional @var{cmd_list} parameter introduces commands that may be
34506 run on the target, rather than being reported back to @value{GDBN}.
34507 The parameter starts with a numeric flag @var{persist}; if the flag is
34508 nonzero, then the breakpoint may remain active and the commands
34509 continue to be run even when @value{GDBN} disconnects from the target.
34510 Following this flag is a series of expressions concatenated with no
34511 separators. Each expression has the following form:
34515 @item X @var{len},@var{expr}
34516 @var{len} is the length of the bytecode expression and @var{expr} is the
34517 actual conditional expression in bytecode form.
34521 see @ref{Architecture-Specific Protocol Details}.
34523 @emph{Implementation note: It is possible for a target to copy or move
34524 code that contains memory breakpoints (e.g., when implementing
34525 overlays). The behavior of this packet, in the presence of such a
34526 target, is not defined.}
34538 @item z1,@var{addr},@var{kind}
34539 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34540 @cindex @samp{z1} packet
34541 @cindex @samp{Z1} packet
34542 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34543 address @var{addr}.
34545 A hardware breakpoint is implemented using a mechanism that is not
34546 dependant on being able to modify the target's memory. The @var{kind}
34547 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34549 @emph{Implementation note: A hardware breakpoint is not affected by code
34562 @item z2,@var{addr},@var{kind}
34563 @itemx Z2,@var{addr},@var{kind}
34564 @cindex @samp{z2} packet
34565 @cindex @samp{Z2} packet
34566 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34567 The number of bytes to watch is specified by @var{kind}.
34579 @item z3,@var{addr},@var{kind}
34580 @itemx Z3,@var{addr},@var{kind}
34581 @cindex @samp{z3} packet
34582 @cindex @samp{Z3} packet
34583 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34584 The number of bytes to watch is specified by @var{kind}.
34596 @item z4,@var{addr},@var{kind}
34597 @itemx Z4,@var{addr},@var{kind}
34598 @cindex @samp{z4} packet
34599 @cindex @samp{Z4} packet
34600 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34601 The number of bytes to watch is specified by @var{kind}.
34615 @node Stop Reply Packets
34616 @section Stop Reply Packets
34617 @cindex stop reply packets
34619 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34620 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34621 receive any of the below as a reply. Except for @samp{?}
34622 and @samp{vStopped}, that reply is only returned
34623 when the target halts. In the below the exact meaning of @dfn{signal
34624 number} is defined by the header @file{include/gdb/signals.h} in the
34625 @value{GDBN} source code.
34627 As in the description of request packets, we include spaces in the
34628 reply templates for clarity; these are not part of the reply packet's
34629 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34635 The program received signal number @var{AA} (a two-digit hexadecimal
34636 number). This is equivalent to a @samp{T} response with no
34637 @var{n}:@var{r} pairs.
34639 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34640 @cindex @samp{T} packet reply
34641 The program received signal number @var{AA} (a two-digit hexadecimal
34642 number). This is equivalent to an @samp{S} response, except that the
34643 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34644 and other information directly in the stop reply packet, reducing
34645 round-trip latency. Single-step and breakpoint traps are reported
34646 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34650 If @var{n} is a hexadecimal number, it is a register number, and the
34651 corresponding @var{r} gives that register's value. The data @var{r} is a
34652 series of bytes in target byte order, with each byte given by a
34653 two-digit hex number.
34656 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34657 the stopped thread, as specified in @ref{thread-id syntax}.
34660 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34661 the core on which the stop event was detected.
34664 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34665 specific event that stopped the target. The currently defined stop
34666 reasons are listed below. The @var{aa} should be @samp{05}, the trap
34667 signal. At most one stop reason should be present.
34670 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34671 and go on to the next; this allows us to extend the protocol in the
34675 The currently defined stop reasons are:
34681 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34684 @cindex shared library events, remote reply
34686 The packet indicates that the loaded libraries have changed.
34687 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34688 list of loaded libraries. The @var{r} part is ignored.
34690 @cindex replay log events, remote reply
34692 The packet indicates that the target cannot continue replaying
34693 logged execution events, because it has reached the end (or the
34694 beginning when executing backward) of the log. The value of @var{r}
34695 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34696 for more information.
34700 @itemx W @var{AA} ; process:@var{pid}
34701 The process exited, and @var{AA} is the exit status. This is only
34702 applicable to certain targets.
34704 The second form of the response, including the process ID of the exited
34705 process, can be used only when @value{GDBN} has reported support for
34706 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34707 The @var{pid} is formatted as a big-endian hex string.
34710 @itemx X @var{AA} ; process:@var{pid}
34711 The process terminated with signal @var{AA}.
34713 The second form of the response, including the process ID of the
34714 terminated process, can be used only when @value{GDBN} has reported
34715 support for multiprocess protocol extensions; see @ref{multiprocess
34716 extensions}. The @var{pid} is formatted as a big-endian hex string.
34718 @item O @var{XX}@dots{}
34719 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34720 written as the program's console output. This can happen at any time
34721 while the program is running and the debugger should continue to wait
34722 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34724 @item F @var{call-id},@var{parameter}@dots{}
34725 @var{call-id} is the identifier which says which host system call should
34726 be called. This is just the name of the function. Translation into the
34727 correct system call is only applicable as it's defined in @value{GDBN}.
34728 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34731 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34732 this very system call.
34734 The target replies with this packet when it expects @value{GDBN} to
34735 call a host system call on behalf of the target. @value{GDBN} replies
34736 with an appropriate @samp{F} packet and keeps up waiting for the next
34737 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34738 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34739 Protocol Extension}, for more details.
34743 @node General Query Packets
34744 @section General Query Packets
34745 @cindex remote query requests
34747 Packets starting with @samp{q} are @dfn{general query packets};
34748 packets starting with @samp{Q} are @dfn{general set packets}. General
34749 query and set packets are a semi-unified form for retrieving and
34750 sending information to and from the stub.
34752 The initial letter of a query or set packet is followed by a name
34753 indicating what sort of thing the packet applies to. For example,
34754 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34755 definitions with the stub. These packet names follow some
34760 The name must not contain commas, colons or semicolons.
34762 Most @value{GDBN} query and set packets have a leading upper case
34765 The names of custom vendor packets should use a company prefix, in
34766 lower case, followed by a period. For example, packets designed at
34767 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34768 foos) or @samp{Qacme.bar} (for setting bars).
34771 The name of a query or set packet should be separated from any
34772 parameters by a @samp{:}; the parameters themselves should be
34773 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34774 full packet name, and check for a separator or the end of the packet,
34775 in case two packet names share a common prefix. New packets should not begin
34776 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34777 packets predate these conventions, and have arguments without any terminator
34778 for the packet name; we suspect they are in widespread use in places that
34779 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34780 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34783 Like the descriptions of the other packets, each description here
34784 has a template showing the packet's overall syntax, followed by an
34785 explanation of the packet's meaning. We include spaces in some of the
34786 templates for clarity; these are not part of the packet's syntax. No
34787 @value{GDBN} packet uses spaces to separate its components.
34789 Here are the currently defined query and set packets:
34795 Turn on or off the agent as a helper to perform some debugging operations
34796 delegated from @value{GDBN} (@pxref{Control Agent}).
34798 @item QAllow:@var{op}:@var{val}@dots{}
34799 @cindex @samp{QAllow} packet
34800 Specify which operations @value{GDBN} expects to request of the
34801 target, as a semicolon-separated list of operation name and value
34802 pairs. Possible values for @var{op} include @samp{WriteReg},
34803 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34804 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34805 indicating that @value{GDBN} will not request the operation, or 1,
34806 indicating that it may. (The target can then use this to set up its
34807 own internals optimally, for instance if the debugger never expects to
34808 insert breakpoints, it may not need to install its own trap handler.)
34811 @cindex current thread, remote request
34812 @cindex @samp{qC} packet
34813 Return the current thread ID.
34817 @item QC @var{thread-id}
34818 Where @var{thread-id} is a thread ID as documented in
34819 @ref{thread-id syntax}.
34820 @item @r{(anything else)}
34821 Any other reply implies the old thread ID.
34824 @item qCRC:@var{addr},@var{length}
34825 @cindex CRC of memory block, remote request
34826 @cindex @samp{qCRC} packet
34827 @anchor{qCRC packet}
34828 Compute the CRC checksum of a block of memory using CRC-32 defined in
34829 IEEE 802.3. The CRC is computed byte at a time, taking the most
34830 significant bit of each byte first. The initial pattern code
34831 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34833 @emph{Note:} This is the same CRC used in validating separate debug
34834 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34835 Files}). However the algorithm is slightly different. When validating
34836 separate debug files, the CRC is computed taking the @emph{least}
34837 significant bit of each byte first, and the final result is inverted to
34838 detect trailing zeros.
34843 An error (such as memory fault)
34844 @item C @var{crc32}
34845 The specified memory region's checksum is @var{crc32}.
34848 @item QDisableRandomization:@var{value}
34849 @cindex disable address space randomization, remote request
34850 @cindex @samp{QDisableRandomization} packet
34851 Some target operating systems will randomize the virtual address space
34852 of the inferior process as a security feature, but provide a feature
34853 to disable such randomization, e.g.@: to allow for a more deterministic
34854 debugging experience. On such systems, this packet with a @var{value}
34855 of 1 directs the target to disable address space randomization for
34856 processes subsequently started via @samp{vRun} packets, while a packet
34857 with a @var{value} of 0 tells the target to enable address space
34860 This packet is only available in extended mode (@pxref{extended mode}).
34865 The request succeeded.
34868 An error occurred. The error number @var{nn} is given as hex digits.
34871 An empty reply indicates that @samp{QDisableRandomization} is not supported
34875 This packet is not probed by default; the remote stub must request it,
34876 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34877 This should only be done on targets that actually support disabling
34878 address space randomization.
34881 @itemx qsThreadInfo
34882 @cindex list active threads, remote request
34883 @cindex @samp{qfThreadInfo} packet
34884 @cindex @samp{qsThreadInfo} packet
34885 Obtain a list of all active thread IDs from the target (OS). Since there
34886 may be too many active threads to fit into one reply packet, this query
34887 works iteratively: it may require more than one query/reply sequence to
34888 obtain the entire list of threads. The first query of the sequence will
34889 be the @samp{qfThreadInfo} query; subsequent queries in the
34890 sequence will be the @samp{qsThreadInfo} query.
34892 NOTE: This packet replaces the @samp{qL} query (see below).
34896 @item m @var{thread-id}
34898 @item m @var{thread-id},@var{thread-id}@dots{}
34899 a comma-separated list of thread IDs
34901 (lower case letter @samp{L}) denotes end of list.
34904 In response to each query, the target will reply with a list of one or
34905 more thread IDs, separated by commas.
34906 @value{GDBN} will respond to each reply with a request for more thread
34907 ids (using the @samp{qs} form of the query), until the target responds
34908 with @samp{l} (lower-case ell, for @dfn{last}).
34909 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34912 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
34913 initial connection with the remote target, and the very first thread ID
34914 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
34915 message. Therefore, the stub should ensure that the first thread ID in
34916 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
34918 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34919 @cindex get thread-local storage address, remote request
34920 @cindex @samp{qGetTLSAddr} packet
34921 Fetch the address associated with thread local storage specified
34922 by @var{thread-id}, @var{offset}, and @var{lm}.
34924 @var{thread-id} is the thread ID associated with the
34925 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34927 @var{offset} is the (big endian, hex encoded) offset associated with the
34928 thread local variable. (This offset is obtained from the debug
34929 information associated with the variable.)
34931 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34932 load module associated with the thread local storage. For example,
34933 a @sc{gnu}/Linux system will pass the link map address of the shared
34934 object associated with the thread local storage under consideration.
34935 Other operating environments may choose to represent the load module
34936 differently, so the precise meaning of this parameter will vary.
34940 @item @var{XX}@dots{}
34941 Hex encoded (big endian) bytes representing the address of the thread
34942 local storage requested.
34945 An error occurred. The error number @var{nn} is given as hex digits.
34948 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34951 @item qGetTIBAddr:@var{thread-id}
34952 @cindex get thread information block address
34953 @cindex @samp{qGetTIBAddr} packet
34954 Fetch address of the Windows OS specific Thread Information Block.
34956 @var{thread-id} is the thread ID associated with the thread.
34960 @item @var{XX}@dots{}
34961 Hex encoded (big endian) bytes representing the linear address of the
34962 thread information block.
34965 An error occured. This means that either the thread was not found, or the
34966 address could not be retrieved.
34969 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34972 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34973 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34974 digit) is one to indicate the first query and zero to indicate a
34975 subsequent query; @var{threadcount} (two hex digits) is the maximum
34976 number of threads the response packet can contain; and @var{nextthread}
34977 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34978 returned in the response as @var{argthread}.
34980 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34984 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34985 Where: @var{count} (two hex digits) is the number of threads being
34986 returned; @var{done} (one hex digit) is zero to indicate more threads
34987 and one indicates no further threads; @var{argthreadid} (eight hex
34988 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34989 is a sequence of thread IDs, @var{threadid} (eight hex
34990 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
34994 @cindex section offsets, remote request
34995 @cindex @samp{qOffsets} packet
34996 Get section offsets that the target used when relocating the downloaded
35001 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35002 Relocate the @code{Text} section by @var{xxx} from its original address.
35003 Relocate the @code{Data} section by @var{yyy} from its original address.
35004 If the object file format provides segment information (e.g.@: @sc{elf}
35005 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35006 segments by the supplied offsets.
35008 @emph{Note: while a @code{Bss} offset may be included in the response,
35009 @value{GDBN} ignores this and instead applies the @code{Data} offset
35010 to the @code{Bss} section.}
35012 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35013 Relocate the first segment of the object file, which conventionally
35014 contains program code, to a starting address of @var{xxx}. If
35015 @samp{DataSeg} is specified, relocate the second segment, which
35016 conventionally contains modifiable data, to a starting address of
35017 @var{yyy}. @value{GDBN} will report an error if the object file
35018 does not contain segment information, or does not contain at least
35019 as many segments as mentioned in the reply. Extra segments are
35020 kept at fixed offsets relative to the last relocated segment.
35023 @item qP @var{mode} @var{thread-id}
35024 @cindex thread information, remote request
35025 @cindex @samp{qP} packet
35026 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35027 encoded 32 bit mode; @var{thread-id} is a thread ID
35028 (@pxref{thread-id syntax}).
35030 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35033 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35037 @cindex non-stop mode, remote request
35038 @cindex @samp{QNonStop} packet
35040 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35041 @xref{Remote Non-Stop}, for more information.
35046 The request succeeded.
35049 An error occurred. The error number @var{nn} is given as hex digits.
35052 An empty reply indicates that @samp{QNonStop} is not supported by
35056 This packet is not probed by default; the remote stub must request it,
35057 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35058 Use of this packet is controlled by the @code{set non-stop} command;
35059 @pxref{Non-Stop Mode}.
35061 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35062 @cindex pass signals to inferior, remote request
35063 @cindex @samp{QPassSignals} packet
35064 @anchor{QPassSignals}
35065 Each listed @var{signal} should be passed directly to the inferior process.
35066 Signals are numbered identically to continue packets and stop replies
35067 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35068 strictly greater than the previous item. These signals do not need to stop
35069 the inferior, or be reported to @value{GDBN}. All other signals should be
35070 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35071 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35072 new list. This packet improves performance when using @samp{handle
35073 @var{signal} nostop noprint pass}.
35078 The request succeeded.
35081 An error occurred. The error number @var{nn} is given as hex digits.
35084 An empty reply indicates that @samp{QPassSignals} is not supported by
35088 Use of this packet is controlled by the @code{set remote pass-signals}
35089 command (@pxref{Remote Configuration, set remote pass-signals}).
35090 This packet is not probed by default; the remote stub must request it,
35091 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35093 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35094 @cindex signals the inferior may see, remote request
35095 @cindex @samp{QProgramSignals} packet
35096 @anchor{QProgramSignals}
35097 Each listed @var{signal} may be delivered to the inferior process.
35098 Others should be silently discarded.
35100 In some cases, the remote stub may need to decide whether to deliver a
35101 signal to the program or not without @value{GDBN} involvement. One
35102 example of that is while detaching --- the program's threads may have
35103 stopped for signals that haven't yet had a chance of being reported to
35104 @value{GDBN}, and so the remote stub can use the signal list specified
35105 by this packet to know whether to deliver or ignore those pending
35108 This does not influence whether to deliver a signal as requested by a
35109 resumption packet (@pxref{vCont packet}).
35111 Signals are numbered identically to continue packets and stop replies
35112 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35113 strictly greater than the previous item. Multiple
35114 @samp{QProgramSignals} packets do not combine; any earlier
35115 @samp{QProgramSignals} list is completely replaced by the new list.
35120 The request succeeded.
35123 An error occurred. The error number @var{nn} is given as hex digits.
35126 An empty reply indicates that @samp{QProgramSignals} is not supported
35130 Use of this packet is controlled by the @code{set remote program-signals}
35131 command (@pxref{Remote Configuration, set remote program-signals}).
35132 This packet is not probed by default; the remote stub must request it,
35133 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35135 @item qRcmd,@var{command}
35136 @cindex execute remote command, remote request
35137 @cindex @samp{qRcmd} packet
35138 @var{command} (hex encoded) is passed to the local interpreter for
35139 execution. Invalid commands should be reported using the output
35140 string. Before the final result packet, the target may also respond
35141 with a number of intermediate @samp{O@var{output}} console output
35142 packets. @emph{Implementors should note that providing access to a
35143 stubs's interpreter may have security implications}.
35148 A command response with no output.
35150 A command response with the hex encoded output string @var{OUTPUT}.
35152 Indicate a badly formed request.
35154 An empty reply indicates that @samp{qRcmd} is not recognized.
35157 (Note that the @code{qRcmd} packet's name is separated from the
35158 command by a @samp{,}, not a @samp{:}, contrary to the naming
35159 conventions above. Please don't use this packet as a model for new
35162 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35163 @cindex searching memory, in remote debugging
35165 @cindex @samp{qSearch:memory} packet
35167 @cindex @samp{qSearch memory} packet
35168 @anchor{qSearch memory}
35169 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35170 Both @var{address} and @var{length} are encoded in hex;
35171 @var{search-pattern} is a sequence of bytes, also hex encoded.
35176 The pattern was not found.
35178 The pattern was found at @var{address}.
35180 A badly formed request or an error was encountered while searching memory.
35182 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35185 @item QStartNoAckMode
35186 @cindex @samp{QStartNoAckMode} packet
35187 @anchor{QStartNoAckMode}
35188 Request that the remote stub disable the normal @samp{+}/@samp{-}
35189 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35194 The stub has switched to no-acknowledgment mode.
35195 @value{GDBN} acknowledges this reponse,
35196 but neither the stub nor @value{GDBN} shall send or expect further
35197 @samp{+}/@samp{-} acknowledgments in the current connection.
35199 An empty reply indicates that the stub does not support no-acknowledgment mode.
35202 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35203 @cindex supported packets, remote query
35204 @cindex features of the remote protocol
35205 @cindex @samp{qSupported} packet
35206 @anchor{qSupported}
35207 Tell the remote stub about features supported by @value{GDBN}, and
35208 query the stub for features it supports. This packet allows
35209 @value{GDBN} and the remote stub to take advantage of each others'
35210 features. @samp{qSupported} also consolidates multiple feature probes
35211 at startup, to improve @value{GDBN} performance---a single larger
35212 packet performs better than multiple smaller probe packets on
35213 high-latency links. Some features may enable behavior which must not
35214 be on by default, e.g.@: because it would confuse older clients or
35215 stubs. Other features may describe packets which could be
35216 automatically probed for, but are not. These features must be
35217 reported before @value{GDBN} will use them. This ``default
35218 unsupported'' behavior is not appropriate for all packets, but it
35219 helps to keep the initial connection time under control with new
35220 versions of @value{GDBN} which support increasing numbers of packets.
35224 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35225 The stub supports or does not support each returned @var{stubfeature},
35226 depending on the form of each @var{stubfeature} (see below for the
35229 An empty reply indicates that @samp{qSupported} is not recognized,
35230 or that no features needed to be reported to @value{GDBN}.
35233 The allowed forms for each feature (either a @var{gdbfeature} in the
35234 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35238 @item @var{name}=@var{value}
35239 The remote protocol feature @var{name} is supported, and associated
35240 with the specified @var{value}. The format of @var{value} depends
35241 on the feature, but it must not include a semicolon.
35243 The remote protocol feature @var{name} is supported, and does not
35244 need an associated value.
35246 The remote protocol feature @var{name} is not supported.
35248 The remote protocol feature @var{name} may be supported, and
35249 @value{GDBN} should auto-detect support in some other way when it is
35250 needed. This form will not be used for @var{gdbfeature} notifications,
35251 but may be used for @var{stubfeature} responses.
35254 Whenever the stub receives a @samp{qSupported} request, the
35255 supplied set of @value{GDBN} features should override any previous
35256 request. This allows @value{GDBN} to put the stub in a known
35257 state, even if the stub had previously been communicating with
35258 a different version of @value{GDBN}.
35260 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35265 This feature indicates whether @value{GDBN} supports multiprocess
35266 extensions to the remote protocol. @value{GDBN} does not use such
35267 extensions unless the stub also reports that it supports them by
35268 including @samp{multiprocess+} in its @samp{qSupported} reply.
35269 @xref{multiprocess extensions}, for details.
35272 This feature indicates that @value{GDBN} supports the XML target
35273 description. If the stub sees @samp{xmlRegisters=} with target
35274 specific strings separated by a comma, it will report register
35278 This feature indicates whether @value{GDBN} supports the
35279 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35280 instruction reply packet}).
35283 Stubs should ignore any unknown values for
35284 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35285 packet supports receiving packets of unlimited length (earlier
35286 versions of @value{GDBN} may reject overly long responses). Additional values
35287 for @var{gdbfeature} may be defined in the future to let the stub take
35288 advantage of new features in @value{GDBN}, e.g.@: incompatible
35289 improvements in the remote protocol---the @samp{multiprocess} feature is
35290 an example of such a feature. The stub's reply should be independent
35291 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35292 describes all the features it supports, and then the stub replies with
35293 all the features it supports.
35295 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35296 responses, as long as each response uses one of the standard forms.
35298 Some features are flags. A stub which supports a flag feature
35299 should respond with a @samp{+} form response. Other features
35300 require values, and the stub should respond with an @samp{=}
35303 Each feature has a default value, which @value{GDBN} will use if
35304 @samp{qSupported} is not available or if the feature is not mentioned
35305 in the @samp{qSupported} response. The default values are fixed; a
35306 stub is free to omit any feature responses that match the defaults.
35308 Not all features can be probed, but for those which can, the probing
35309 mechanism is useful: in some cases, a stub's internal
35310 architecture may not allow the protocol layer to know some information
35311 about the underlying target in advance. This is especially common in
35312 stubs which may be configured for multiple targets.
35314 These are the currently defined stub features and their properties:
35316 @multitable @columnfractions 0.35 0.2 0.12 0.2
35317 @c NOTE: The first row should be @headitem, but we do not yet require
35318 @c a new enough version of Texinfo (4.7) to use @headitem.
35320 @tab Value Required
35324 @item @samp{PacketSize}
35329 @item @samp{qXfer:auxv:read}
35334 @item @samp{qXfer:btrace:read}
35339 @item @samp{qXfer:features:read}
35344 @item @samp{qXfer:libraries:read}
35349 @item @samp{qXfer:libraries-svr4:read}
35354 @item @samp{augmented-libraries-svr4-read}
35359 @item @samp{qXfer:memory-map:read}
35364 @item @samp{qXfer:sdata:read}
35369 @item @samp{qXfer:spu:read}
35374 @item @samp{qXfer:spu:write}
35379 @item @samp{qXfer:siginfo:read}
35384 @item @samp{qXfer:siginfo:write}
35389 @item @samp{qXfer:threads:read}
35394 @item @samp{qXfer:traceframe-info:read}
35399 @item @samp{qXfer:uib:read}
35404 @item @samp{qXfer:fdpic:read}
35409 @item @samp{Qbtrace:off}
35414 @item @samp{Qbtrace:bts}
35419 @item @samp{QNonStop}
35424 @item @samp{QPassSignals}
35429 @item @samp{QStartNoAckMode}
35434 @item @samp{multiprocess}
35439 @item @samp{ConditionalBreakpoints}
35444 @item @samp{ConditionalTracepoints}
35449 @item @samp{ReverseContinue}
35454 @item @samp{ReverseStep}
35459 @item @samp{TracepointSource}
35464 @item @samp{QAgent}
35469 @item @samp{QAllow}
35474 @item @samp{QDisableRandomization}
35479 @item @samp{EnableDisableTracepoints}
35484 @item @samp{QTBuffer:size}
35489 @item @samp{tracenz}
35494 @item @samp{BreakpointCommands}
35501 These are the currently defined stub features, in more detail:
35504 @cindex packet size, remote protocol
35505 @item PacketSize=@var{bytes}
35506 The remote stub can accept packets up to at least @var{bytes} in
35507 length. @value{GDBN} will send packets up to this size for bulk
35508 transfers, and will never send larger packets. This is a limit on the
35509 data characters in the packet, including the frame and checksum.
35510 There is no trailing NUL byte in a remote protocol packet; if the stub
35511 stores packets in a NUL-terminated format, it should allow an extra
35512 byte in its buffer for the NUL. If this stub feature is not supported,
35513 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35515 @item qXfer:auxv:read
35516 The remote stub understands the @samp{qXfer:auxv:read} packet
35517 (@pxref{qXfer auxiliary vector read}).
35519 @item qXfer:btrace:read
35520 The remote stub understands the @samp{qXfer:btrace:read}
35521 packet (@pxref{qXfer btrace read}).
35523 @item qXfer:features:read
35524 The remote stub understands the @samp{qXfer:features:read} packet
35525 (@pxref{qXfer target description read}).
35527 @item qXfer:libraries:read
35528 The remote stub understands the @samp{qXfer:libraries:read} packet
35529 (@pxref{qXfer library list read}).
35531 @item qXfer:libraries-svr4:read
35532 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35533 (@pxref{qXfer svr4 library list read}).
35535 @item augmented-libraries-svr4-read
35536 The remote stub understands the augmented form of the
35537 @samp{qXfer:libraries-svr4:read} packet
35538 (@pxref{qXfer svr4 library list read}).
35540 @item qXfer:memory-map:read
35541 The remote stub understands the @samp{qXfer:memory-map:read} packet
35542 (@pxref{qXfer memory map read}).
35544 @item qXfer:sdata:read
35545 The remote stub understands the @samp{qXfer:sdata:read} packet
35546 (@pxref{qXfer sdata read}).
35548 @item qXfer:spu:read
35549 The remote stub understands the @samp{qXfer:spu:read} packet
35550 (@pxref{qXfer spu read}).
35552 @item qXfer:spu:write
35553 The remote stub understands the @samp{qXfer:spu:write} packet
35554 (@pxref{qXfer spu write}).
35556 @item qXfer:siginfo:read
35557 The remote stub understands the @samp{qXfer:siginfo:read} packet
35558 (@pxref{qXfer siginfo read}).
35560 @item qXfer:siginfo:write
35561 The remote stub understands the @samp{qXfer:siginfo:write} packet
35562 (@pxref{qXfer siginfo write}).
35564 @item qXfer:threads:read
35565 The remote stub understands the @samp{qXfer:threads:read} packet
35566 (@pxref{qXfer threads read}).
35568 @item qXfer:traceframe-info:read
35569 The remote stub understands the @samp{qXfer:traceframe-info:read}
35570 packet (@pxref{qXfer traceframe info read}).
35572 @item qXfer:uib:read
35573 The remote stub understands the @samp{qXfer:uib:read}
35574 packet (@pxref{qXfer unwind info block}).
35576 @item qXfer:fdpic:read
35577 The remote stub understands the @samp{qXfer:fdpic:read}
35578 packet (@pxref{qXfer fdpic loadmap read}).
35581 The remote stub understands the @samp{QNonStop} packet
35582 (@pxref{QNonStop}).
35585 The remote stub understands the @samp{QPassSignals} packet
35586 (@pxref{QPassSignals}).
35588 @item QStartNoAckMode
35589 The remote stub understands the @samp{QStartNoAckMode} packet and
35590 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35593 @anchor{multiprocess extensions}
35594 @cindex multiprocess extensions, in remote protocol
35595 The remote stub understands the multiprocess extensions to the remote
35596 protocol syntax. The multiprocess extensions affect the syntax of
35597 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35598 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35599 replies. Note that reporting this feature indicates support for the
35600 syntactic extensions only, not that the stub necessarily supports
35601 debugging of more than one process at a time. The stub must not use
35602 multiprocess extensions in packet replies unless @value{GDBN} has also
35603 indicated it supports them in its @samp{qSupported} request.
35605 @item qXfer:osdata:read
35606 The remote stub understands the @samp{qXfer:osdata:read} packet
35607 ((@pxref{qXfer osdata read}).
35609 @item ConditionalBreakpoints
35610 The target accepts and implements evaluation of conditional expressions
35611 defined for breakpoints. The target will only report breakpoint triggers
35612 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35614 @item ConditionalTracepoints
35615 The remote stub accepts and implements conditional expressions defined
35616 for tracepoints (@pxref{Tracepoint Conditions}).
35618 @item ReverseContinue
35619 The remote stub accepts and implements the reverse continue packet
35623 The remote stub accepts and implements the reverse step packet
35626 @item TracepointSource
35627 The remote stub understands the @samp{QTDPsrc} packet that supplies
35628 the source form of tracepoint definitions.
35631 The remote stub understands the @samp{QAgent} packet.
35634 The remote stub understands the @samp{QAllow} packet.
35636 @item QDisableRandomization
35637 The remote stub understands the @samp{QDisableRandomization} packet.
35639 @item StaticTracepoint
35640 @cindex static tracepoints, in remote protocol
35641 The remote stub supports static tracepoints.
35643 @item InstallInTrace
35644 @anchor{install tracepoint in tracing}
35645 The remote stub supports installing tracepoint in tracing.
35647 @item EnableDisableTracepoints
35648 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35649 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35650 to be enabled and disabled while a trace experiment is running.
35652 @item QTBuffer:size
35653 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
35654 packet that allows to change the size of the trace buffer.
35657 @cindex string tracing, in remote protocol
35658 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35659 See @ref{Bytecode Descriptions} for details about the bytecode.
35661 @item BreakpointCommands
35662 @cindex breakpoint commands, in remote protocol
35663 The remote stub supports running a breakpoint's command list itself,
35664 rather than reporting the hit to @value{GDBN}.
35667 The remote stub understands the @samp{Qbtrace:off} packet.
35670 The remote stub understands the @samp{Qbtrace:bts} packet.
35675 @cindex symbol lookup, remote request
35676 @cindex @samp{qSymbol} packet
35677 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35678 requests. Accept requests from the target for the values of symbols.
35683 The target does not need to look up any (more) symbols.
35684 @item qSymbol:@var{sym_name}
35685 The target requests the value of symbol @var{sym_name} (hex encoded).
35686 @value{GDBN} may provide the value by using the
35687 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35691 @item qSymbol:@var{sym_value}:@var{sym_name}
35692 Set the value of @var{sym_name} to @var{sym_value}.
35694 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35695 target has previously requested.
35697 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35698 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35704 The target does not need to look up any (more) symbols.
35705 @item qSymbol:@var{sym_name}
35706 The target requests the value of a new symbol @var{sym_name} (hex
35707 encoded). @value{GDBN} will continue to supply the values of symbols
35708 (if available), until the target ceases to request them.
35713 @itemx QTDisconnected
35720 @itemx qTMinFTPILen
35722 @xref{Tracepoint Packets}.
35724 @item qThreadExtraInfo,@var{thread-id}
35725 @cindex thread attributes info, remote request
35726 @cindex @samp{qThreadExtraInfo} packet
35727 Obtain from the target OS a printable string description of thread
35728 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
35729 for the forms of @var{thread-id}. This
35730 string may contain anything that the target OS thinks is interesting
35731 for @value{GDBN} to tell the user about the thread. The string is
35732 displayed in @value{GDBN}'s @code{info threads} display. Some
35733 examples of possible thread extra info strings are @samp{Runnable}, or
35734 @samp{Blocked on Mutex}.
35738 @item @var{XX}@dots{}
35739 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35740 comprising the printable string containing the extra information about
35741 the thread's attributes.
35744 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35745 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35746 conventions above. Please don't use this packet as a model for new
35765 @xref{Tracepoint Packets}.
35767 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35768 @cindex read special object, remote request
35769 @cindex @samp{qXfer} packet
35770 @anchor{qXfer read}
35771 Read uninterpreted bytes from the target's special data area
35772 identified by the keyword @var{object}. Request @var{length} bytes
35773 starting at @var{offset} bytes into the data. The content and
35774 encoding of @var{annex} is specific to @var{object}; it can supply
35775 additional details about what data to access.
35777 Here are the specific requests of this form defined so far. All
35778 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35779 formats, listed below.
35782 @item qXfer:auxv:read::@var{offset},@var{length}
35783 @anchor{qXfer auxiliary vector read}
35784 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35785 auxiliary vector}. Note @var{annex} must be empty.
35787 This packet is not probed by default; the remote stub must request it,
35788 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35790 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
35791 @anchor{qXfer btrace read}
35793 Return a description of the current branch trace.
35794 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
35795 packet may have one of the following values:
35799 Returns all available branch trace.
35802 Returns all available branch trace if the branch trace changed since
35803 the last read request.
35806 Returns the new branch trace since the last read request. Adds a new
35807 block to the end of the trace that begins at zero and ends at the source
35808 location of the first branch in the trace buffer. This extra block is
35809 used to stitch traces together.
35811 If the trace buffer overflowed, returns an error indicating the overflow.
35814 This packet is not probed by default; the remote stub must request it
35815 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35817 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35818 @anchor{qXfer target description read}
35819 Access the @dfn{target description}. @xref{Target Descriptions}. The
35820 annex specifies which XML document to access. The main description is
35821 always loaded from the @samp{target.xml} annex.
35823 This packet is not probed by default; the remote stub must request it,
35824 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35826 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35827 @anchor{qXfer library list read}
35828 Access the target's list of loaded libraries. @xref{Library List Format}.
35829 The annex part of the generic @samp{qXfer} packet must be empty
35830 (@pxref{qXfer read}).
35832 Targets which maintain a list of libraries in the program's memory do
35833 not need to implement this packet; it is designed for platforms where
35834 the operating system manages the list of loaded libraries.
35836 This packet is not probed by default; the remote stub must request it,
35837 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35839 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35840 @anchor{qXfer svr4 library list read}
35841 Access the target's list of loaded libraries when the target is an SVR4
35842 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35843 of the generic @samp{qXfer} packet must be empty unless the remote
35844 stub indicated it supports the augmented form of this packet
35845 by supplying an appropriate @samp{qSupported} response
35846 (@pxref{qXfer read}, @ref{qSupported}).
35848 This packet is optional for better performance on SVR4 targets.
35849 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35851 This packet is not probed by default; the remote stub must request it,
35852 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35854 If the remote stub indicates it supports the augmented form of this
35855 packet then the annex part of the generic @samp{qXfer} packet may
35856 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
35857 arguments. The currently supported arguments are:
35860 @item start=@var{address}
35861 A hexadecimal number specifying the address of the @samp{struct
35862 link_map} to start reading the library list from. If unset or zero
35863 then the first @samp{struct link_map} in the library list will be
35864 chosen as the starting point.
35866 @item prev=@var{address}
35867 A hexadecimal number specifying the address of the @samp{struct
35868 link_map} immediately preceding the @samp{struct link_map}
35869 specified by the @samp{start} argument. If unset or zero then
35870 the remote stub will expect that no @samp{struct link_map}
35871 exists prior to the starting point.
35875 Arguments that are not understood by the remote stub will be silently
35878 @item qXfer:memory-map:read::@var{offset},@var{length}
35879 @anchor{qXfer memory map read}
35880 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35881 annex part of the generic @samp{qXfer} packet must be empty
35882 (@pxref{qXfer read}).
35884 This packet is not probed by default; the remote stub must request it,
35885 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35887 @item qXfer:sdata:read::@var{offset},@var{length}
35888 @anchor{qXfer sdata read}
35890 Read contents of the extra collected static tracepoint marker
35891 information. The annex part of the generic @samp{qXfer} packet must
35892 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35895 This packet is not probed by default; the remote stub must request it,
35896 by supplying an appropriate @samp{qSupported} response
35897 (@pxref{qSupported}).
35899 @item qXfer:siginfo:read::@var{offset},@var{length}
35900 @anchor{qXfer siginfo read}
35901 Read contents of the extra signal information on the target
35902 system. The annex part of the generic @samp{qXfer} packet must be
35903 empty (@pxref{qXfer read}).
35905 This packet is not probed by default; the remote stub must request it,
35906 by supplying an appropriate @samp{qSupported} response
35907 (@pxref{qSupported}).
35909 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35910 @anchor{qXfer spu read}
35911 Read contents of an @code{spufs} file on the target system. The
35912 annex specifies which file to read; it must be of the form
35913 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35914 in the target process, and @var{name} identifes the @code{spufs} file
35915 in that context to be accessed.
35917 This packet is not probed by default; the remote stub must request it,
35918 by supplying an appropriate @samp{qSupported} response
35919 (@pxref{qSupported}).
35921 @item qXfer:threads:read::@var{offset},@var{length}
35922 @anchor{qXfer threads read}
35923 Access the list of threads on target. @xref{Thread List Format}. The
35924 annex part of the generic @samp{qXfer} packet must be empty
35925 (@pxref{qXfer read}).
35927 This packet is not probed by default; the remote stub must request it,
35928 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35930 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35931 @anchor{qXfer traceframe info read}
35933 Return a description of the current traceframe's contents.
35934 @xref{Traceframe Info Format}. The annex part of the generic
35935 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35937 This packet is not probed by default; the remote stub must request it,
35938 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35940 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35941 @anchor{qXfer unwind info block}
35943 Return the unwind information block for @var{pc}. This packet is used
35944 on OpenVMS/ia64 to ask the kernel unwind information.
35946 This packet is not probed by default.
35948 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35949 @anchor{qXfer fdpic loadmap read}
35950 Read contents of @code{loadmap}s on the target system. The
35951 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35952 executable @code{loadmap} or interpreter @code{loadmap} to read.
35954 This packet is not probed by default; the remote stub must request it,
35955 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35957 @item qXfer:osdata:read::@var{offset},@var{length}
35958 @anchor{qXfer osdata read}
35959 Access the target's @dfn{operating system information}.
35960 @xref{Operating System Information}.
35967 Data @var{data} (@pxref{Binary Data}) has been read from the
35968 target. There may be more data at a higher address (although
35969 it is permitted to return @samp{m} even for the last valid
35970 block of data, as long as at least one byte of data was read).
35971 It is possible for @var{data} to have fewer bytes than the @var{length} in the
35975 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35976 There is no more data to be read. It is possible for @var{data} to
35977 have fewer bytes than the @var{length} in the request.
35980 The @var{offset} in the request is at the end of the data.
35981 There is no more data to be read.
35984 The request was malformed, or @var{annex} was invalid.
35987 The offset was invalid, or there was an error encountered reading the data.
35988 The @var{nn} part is a hex-encoded @code{errno} value.
35991 An empty reply indicates the @var{object} string was not recognized by
35992 the stub, or that the object does not support reading.
35995 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35996 @cindex write data into object, remote request
35997 @anchor{qXfer write}
35998 Write uninterpreted bytes into the target's special data area
35999 identified by the keyword @var{object}, starting at @var{offset} bytes
36000 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36001 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36002 is specific to @var{object}; it can supply additional details about what data
36005 Here are the specific requests of this form defined so far. All
36006 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36007 formats, listed below.
36010 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36011 @anchor{qXfer siginfo write}
36012 Write @var{data} to the extra signal information on the target system.
36013 The annex part of the generic @samp{qXfer} packet must be
36014 empty (@pxref{qXfer write}).
36016 This packet is not probed by default; the remote stub must request it,
36017 by supplying an appropriate @samp{qSupported} response
36018 (@pxref{qSupported}).
36020 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36021 @anchor{qXfer spu write}
36022 Write @var{data} to an @code{spufs} file on the target system. The
36023 annex specifies which file to write; it must be of the form
36024 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36025 in the target process, and @var{name} identifes the @code{spufs} file
36026 in that context to be accessed.
36028 This packet is not probed by default; the remote stub must request it,
36029 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36035 @var{nn} (hex encoded) is the number of bytes written.
36036 This may be fewer bytes than supplied in the request.
36039 The request was malformed, or @var{annex} was invalid.
36042 The offset was invalid, or there was an error encountered writing the data.
36043 The @var{nn} part is a hex-encoded @code{errno} value.
36046 An empty reply indicates the @var{object} string was not
36047 recognized by the stub, or that the object does not support writing.
36050 @item qXfer:@var{object}:@var{operation}:@dots{}
36051 Requests of this form may be added in the future. When a stub does
36052 not recognize the @var{object} keyword, or its support for
36053 @var{object} does not recognize the @var{operation} keyword, the stub
36054 must respond with an empty packet.
36056 @item qAttached:@var{pid}
36057 @cindex query attached, remote request
36058 @cindex @samp{qAttached} packet
36059 Return an indication of whether the remote server attached to an
36060 existing process or created a new process. When the multiprocess
36061 protocol extensions are supported (@pxref{multiprocess extensions}),
36062 @var{pid} is an integer in hexadecimal format identifying the target
36063 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36064 the query packet will be simplified as @samp{qAttached}.
36066 This query is used, for example, to know whether the remote process
36067 should be detached or killed when a @value{GDBN} session is ended with
36068 the @code{quit} command.
36073 The remote server attached to an existing process.
36075 The remote server created a new process.
36077 A badly formed request or an error was encountered.
36081 Enable branch tracing for the current thread using bts tracing.
36086 Branch tracing has been enabled.
36088 A badly formed request or an error was encountered.
36092 Disable branch tracing for the current thread.
36097 Branch tracing has been disabled.
36099 A badly formed request or an error was encountered.
36104 @node Architecture-Specific Protocol Details
36105 @section Architecture-Specific Protocol Details
36107 This section describes how the remote protocol is applied to specific
36108 target architectures. Also see @ref{Standard Target Features}, for
36109 details of XML target descriptions for each architecture.
36112 * ARM-Specific Protocol Details::
36113 * MIPS-Specific Protocol Details::
36116 @node ARM-Specific Protocol Details
36117 @subsection @acronym{ARM}-specific Protocol Details
36120 * ARM Breakpoint Kinds::
36123 @node ARM Breakpoint Kinds
36124 @subsubsection @acronym{ARM} Breakpoint Kinds
36125 @cindex breakpoint kinds, @acronym{ARM}
36127 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36132 16-bit Thumb mode breakpoint.
36135 32-bit Thumb mode (Thumb-2) breakpoint.
36138 32-bit @acronym{ARM} mode breakpoint.
36142 @node MIPS-Specific Protocol Details
36143 @subsection @acronym{MIPS}-specific Protocol Details
36146 * MIPS Register packet Format::
36147 * MIPS Breakpoint Kinds::
36150 @node MIPS Register packet Format
36151 @subsubsection @acronym{MIPS} Register Packet Format
36152 @cindex register packet format, @acronym{MIPS}
36154 The following @code{g}/@code{G} packets have previously been defined.
36155 In the below, some thirty-two bit registers are transferred as
36156 sixty-four bits. Those registers should be zero/sign extended (which?)
36157 to fill the space allocated. Register bytes are transferred in target
36158 byte order. The two nibbles within a register byte are transferred
36159 most-significant -- least-significant.
36164 All registers are transferred as thirty-two bit quantities in the order:
36165 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36166 registers; fsr; fir; fp.
36169 All registers are transferred as sixty-four bit quantities (including
36170 thirty-two bit registers such as @code{sr}). The ordering is the same
36175 @node MIPS Breakpoint Kinds
36176 @subsubsection @acronym{MIPS} Breakpoint Kinds
36177 @cindex breakpoint kinds, @acronym{MIPS}
36179 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36184 16-bit @acronym{MIPS16} mode breakpoint.
36187 16-bit @acronym{microMIPS} mode breakpoint.
36190 32-bit standard @acronym{MIPS} mode breakpoint.
36193 32-bit @acronym{microMIPS} mode breakpoint.
36197 @node Tracepoint Packets
36198 @section Tracepoint Packets
36199 @cindex tracepoint packets
36200 @cindex packets, tracepoint
36202 Here we describe the packets @value{GDBN} uses to implement
36203 tracepoints (@pxref{Tracepoints}).
36207 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36208 @cindex @samp{QTDP} packet
36209 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36210 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36211 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36212 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36213 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36214 the number of bytes that the target should copy elsewhere to make room
36215 for the tracepoint. If an @samp{X} is present, it introduces a
36216 tracepoint condition, which consists of a hexadecimal length, followed
36217 by a comma and hex-encoded bytes, in a manner similar to action
36218 encodings as described below. If the trailing @samp{-} is present,
36219 further @samp{QTDP} packets will follow to specify this tracepoint's
36225 The packet was understood and carried out.
36227 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36229 The packet was not recognized.
36232 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36233 Define actions to be taken when a tracepoint is hit. The @var{n} and
36234 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36235 this tracepoint. This packet may only be sent immediately after
36236 another @samp{QTDP} packet that ended with a @samp{-}. If the
36237 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36238 specifying more actions for this tracepoint.
36240 In the series of action packets for a given tracepoint, at most one
36241 can have an @samp{S} before its first @var{action}. If such a packet
36242 is sent, it and the following packets define ``while-stepping''
36243 actions. Any prior packets define ordinary actions --- that is, those
36244 taken when the tracepoint is first hit. If no action packet has an
36245 @samp{S}, then all the packets in the series specify ordinary
36246 tracepoint actions.
36248 The @samp{@var{action}@dots{}} portion of the packet is a series of
36249 actions, concatenated without separators. Each action has one of the
36255 Collect the registers whose bits are set in @var{mask},
36256 a hexadecimal number whose @var{i}'th bit is set if register number
36257 @var{i} should be collected. (The least significant bit is numbered
36258 zero.) Note that @var{mask} may be any number of digits long; it may
36259 not fit in a 32-bit word.
36261 @item M @var{basereg},@var{offset},@var{len}
36262 Collect @var{len} bytes of memory starting at the address in register
36263 number @var{basereg}, plus @var{offset}. If @var{basereg} is
36264 @samp{-1}, then the range has a fixed address: @var{offset} is the
36265 address of the lowest byte to collect. The @var{basereg},
36266 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
36267 values (the @samp{-1} value for @var{basereg} is a special case).
36269 @item X @var{len},@var{expr}
36270 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
36271 it directs. The agent expression @var{expr} is as described in
36272 @ref{Agent Expressions}. Each byte of the expression is encoded as a
36273 two-digit hex number in the packet; @var{len} is the number of bytes
36274 in the expression (and thus one-half the number of hex digits in the
36279 Any number of actions may be packed together in a single @samp{QTDP}
36280 packet, as long as the packet does not exceed the maximum packet
36281 length (400 bytes, for many stubs). There may be only one @samp{R}
36282 action per tracepoint, and it must precede any @samp{M} or @samp{X}
36283 actions. Any registers referred to by @samp{M} and @samp{X} actions
36284 must be collected by a preceding @samp{R} action. (The
36285 ``while-stepping'' actions are treated as if they were attached to a
36286 separate tracepoint, as far as these restrictions are concerned.)
36291 The packet was understood and carried out.
36293 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36295 The packet was not recognized.
36298 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36299 @cindex @samp{QTDPsrc} packet
36300 Specify a source string of tracepoint @var{n} at address @var{addr}.
36301 This is useful to get accurate reproduction of the tracepoints
36302 originally downloaded at the beginning of the trace run. The @var{type}
36303 is the name of the tracepoint part, such as @samp{cond} for the
36304 tracepoint's conditional expression (see below for a list of types), while
36305 @var{bytes} is the string, encoded in hexadecimal.
36307 @var{start} is the offset of the @var{bytes} within the overall source
36308 string, while @var{slen} is the total length of the source string.
36309 This is intended for handling source strings that are longer than will
36310 fit in a single packet.
36311 @c Add detailed example when this info is moved into a dedicated
36312 @c tracepoint descriptions section.
36314 The available string types are @samp{at} for the location,
36315 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36316 @value{GDBN} sends a separate packet for each command in the action
36317 list, in the same order in which the commands are stored in the list.
36319 The target does not need to do anything with source strings except
36320 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36323 Although this packet is optional, and @value{GDBN} will only send it
36324 if the target replies with @samp{TracepointSource} @xref{General
36325 Query Packets}, it makes both disconnected tracing and trace files
36326 much easier to use. Otherwise the user must be careful that the
36327 tracepoints in effect while looking at trace frames are identical to
36328 the ones in effect during the trace run; even a small discrepancy
36329 could cause @samp{tdump} not to work, or a particular trace frame not
36332 @item QTDV:@var{n}:@var{value}
36333 @cindex define trace state variable, remote request
36334 @cindex @samp{QTDV} packet
36335 Create a new trace state variable, number @var{n}, with an initial
36336 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36337 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36338 the option of not using this packet for initial values of zero; the
36339 target should simply create the trace state variables as they are
36340 mentioned in expressions.
36342 @item QTFrame:@var{n}
36343 @cindex @samp{QTFrame} packet
36344 Select the @var{n}'th tracepoint frame from the buffer, and use the
36345 register and memory contents recorded there to answer subsequent
36346 request packets from @value{GDBN}.
36348 A successful reply from the stub indicates that the stub has found the
36349 requested frame. The response is a series of parts, concatenated
36350 without separators, describing the frame we selected. Each part has
36351 one of the following forms:
36355 The selected frame is number @var{n} in the trace frame buffer;
36356 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36357 was no frame matching the criteria in the request packet.
36360 The selected trace frame records a hit of tracepoint number @var{t};
36361 @var{t} is a hexadecimal number.
36365 @item QTFrame:pc:@var{addr}
36366 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36367 currently selected frame whose PC is @var{addr};
36368 @var{addr} is a hexadecimal number.
36370 @item QTFrame:tdp:@var{t}
36371 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36372 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36373 is a hexadecimal number.
36375 @item QTFrame:range:@var{start}:@var{end}
36376 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36377 currently selected frame whose PC is between @var{start} (inclusive)
36378 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36381 @item QTFrame:outside:@var{start}:@var{end}
36382 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36383 frame @emph{outside} the given range of addresses (exclusive).
36386 @cindex @samp{qTMinFTPILen} packet
36387 This packet requests the minimum length of instruction at which a fast
36388 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36389 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36390 it depends on the target system being able to create trampolines in
36391 the first 64K of memory, which might or might not be possible for that
36392 system. So the reply to this packet will be 4 if it is able to
36399 The minimum instruction length is currently unknown.
36401 The minimum instruction length is @var{length}, where @var{length}
36402 is a hexadecimal number greater or equal to 1. A reply
36403 of 1 means that a fast tracepoint may be placed on any instruction
36404 regardless of size.
36406 An error has occurred.
36408 An empty reply indicates that the request is not supported by the stub.
36412 @cindex @samp{QTStart} packet
36413 Begin the tracepoint experiment. Begin collecting data from
36414 tracepoint hits in the trace frame buffer. This packet supports the
36415 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36416 instruction reply packet}).
36419 @cindex @samp{QTStop} packet
36420 End the tracepoint experiment. Stop collecting trace frames.
36422 @item QTEnable:@var{n}:@var{addr}
36424 @cindex @samp{QTEnable} packet
36425 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36426 experiment. If the tracepoint was previously disabled, then collection
36427 of data from it will resume.
36429 @item QTDisable:@var{n}:@var{addr}
36431 @cindex @samp{QTDisable} packet
36432 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36433 experiment. No more data will be collected from the tracepoint unless
36434 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36437 @cindex @samp{QTinit} packet
36438 Clear the table of tracepoints, and empty the trace frame buffer.
36440 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36441 @cindex @samp{QTro} packet
36442 Establish the given ranges of memory as ``transparent''. The stub
36443 will answer requests for these ranges from memory's current contents,
36444 if they were not collected as part of the tracepoint hit.
36446 @value{GDBN} uses this to mark read-only regions of memory, like those
36447 containing program code. Since these areas never change, they should
36448 still have the same contents they did when the tracepoint was hit, so
36449 there's no reason for the stub to refuse to provide their contents.
36451 @item QTDisconnected:@var{value}
36452 @cindex @samp{QTDisconnected} packet
36453 Set the choice to what to do with the tracing run when @value{GDBN}
36454 disconnects from the target. A @var{value} of 1 directs the target to
36455 continue the tracing run, while 0 tells the target to stop tracing if
36456 @value{GDBN} is no longer in the picture.
36459 @cindex @samp{qTStatus} packet
36460 Ask the stub if there is a trace experiment running right now.
36462 The reply has the form:
36466 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36467 @var{running} is a single digit @code{1} if the trace is presently
36468 running, or @code{0} if not. It is followed by semicolon-separated
36469 optional fields that an agent may use to report additional status.
36473 If the trace is not running, the agent may report any of several
36474 explanations as one of the optional fields:
36479 No trace has been run yet.
36481 @item tstop[:@var{text}]:0
36482 The trace was stopped by a user-originated stop command. The optional
36483 @var{text} field is a user-supplied string supplied as part of the
36484 stop command (for instance, an explanation of why the trace was
36485 stopped manually). It is hex-encoded.
36488 The trace stopped because the trace buffer filled up.
36490 @item tdisconnected:0
36491 The trace stopped because @value{GDBN} disconnected from the target.
36493 @item tpasscount:@var{tpnum}
36494 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36496 @item terror:@var{text}:@var{tpnum}
36497 The trace stopped because tracepoint @var{tpnum} had an error. The
36498 string @var{text} is available to describe the nature of the error
36499 (for instance, a divide by zero in the condition expression); it
36503 The trace stopped for some other reason.
36507 Additional optional fields supply statistical and other information.
36508 Although not required, they are extremely useful for users monitoring
36509 the progress of a trace run. If a trace has stopped, and these
36510 numbers are reported, they must reflect the state of the just-stopped
36515 @item tframes:@var{n}
36516 The number of trace frames in the buffer.
36518 @item tcreated:@var{n}
36519 The total number of trace frames created during the run. This may
36520 be larger than the trace frame count, if the buffer is circular.
36522 @item tsize:@var{n}
36523 The total size of the trace buffer, in bytes.
36525 @item tfree:@var{n}
36526 The number of bytes still unused in the buffer.
36528 @item circular:@var{n}
36529 The value of the circular trace buffer flag. @code{1} means that the
36530 trace buffer is circular and old trace frames will be discarded if
36531 necessary to make room, @code{0} means that the trace buffer is linear
36534 @item disconn:@var{n}
36535 The value of the disconnected tracing flag. @code{1} means that
36536 tracing will continue after @value{GDBN} disconnects, @code{0} means
36537 that the trace run will stop.
36541 @item qTP:@var{tp}:@var{addr}
36542 @cindex tracepoint status, remote request
36543 @cindex @samp{qTP} packet
36544 Ask the stub for the current state of tracepoint number @var{tp} at
36545 address @var{addr}.
36549 @item V@var{hits}:@var{usage}
36550 The tracepoint has been hit @var{hits} times so far during the trace
36551 run, and accounts for @var{usage} in the trace buffer. Note that
36552 @code{while-stepping} steps are not counted as separate hits, but the
36553 steps' space consumption is added into the usage number.
36557 @item qTV:@var{var}
36558 @cindex trace state variable value, remote request
36559 @cindex @samp{qTV} packet
36560 Ask the stub for the value of the trace state variable number @var{var}.
36565 The value of the variable is @var{value}. This will be the current
36566 value of the variable if the user is examining a running target, or a
36567 saved value if the variable was collected in the trace frame that the
36568 user is looking at. Note that multiple requests may result in
36569 different reply values, such as when requesting values while the
36570 program is running.
36573 The value of the variable is unknown. This would occur, for example,
36574 if the user is examining a trace frame in which the requested variable
36579 @cindex @samp{qTfP} packet
36581 @cindex @samp{qTsP} packet
36582 These packets request data about tracepoints that are being used by
36583 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36584 of data, and multiple @code{qTsP} to get additional pieces. Replies
36585 to these packets generally take the form of the @code{QTDP} packets
36586 that define tracepoints. (FIXME add detailed syntax)
36589 @cindex @samp{qTfV} packet
36591 @cindex @samp{qTsV} packet
36592 These packets request data about trace state variables that are on the
36593 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36594 and multiple @code{qTsV} to get additional variables. Replies to
36595 these packets follow the syntax of the @code{QTDV} packets that define
36596 trace state variables.
36602 @cindex @samp{qTfSTM} packet
36603 @cindex @samp{qTsSTM} packet
36604 These packets request data about static tracepoint markers that exist
36605 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36606 first piece of data, and multiple @code{qTsSTM} to get additional
36607 pieces. Replies to these packets take the following form:
36611 @item m @var{address}:@var{id}:@var{extra}
36613 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36614 a comma-separated list of markers
36616 (lower case letter @samp{L}) denotes end of list.
36618 An error occurred. The error number @var{nn} is given as hex digits.
36620 An empty reply indicates that the request is not supported by the
36624 The @var{address} is encoded in hex;
36625 @var{id} and @var{extra} are strings encoded in hex.
36627 In response to each query, the target will reply with a list of one or
36628 more markers, separated by commas. @value{GDBN} will respond to each
36629 reply with a request for more markers (using the @samp{qs} form of the
36630 query), until the target responds with @samp{l} (lower-case ell, for
36633 @item qTSTMat:@var{address}
36635 @cindex @samp{qTSTMat} packet
36636 This packets requests data about static tracepoint markers in the
36637 target program at @var{address}. Replies to this packet follow the
36638 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36639 tracepoint markers.
36641 @item QTSave:@var{filename}
36642 @cindex @samp{QTSave} packet
36643 This packet directs the target to save trace data to the file name
36644 @var{filename} in the target's filesystem. The @var{filename} is encoded
36645 as a hex string; the interpretation of the file name (relative vs
36646 absolute, wild cards, etc) is up to the target.
36648 @item qTBuffer:@var{offset},@var{len}
36649 @cindex @samp{qTBuffer} packet
36650 Return up to @var{len} bytes of the current contents of trace buffer,
36651 starting at @var{offset}. The trace buffer is treated as if it were
36652 a contiguous collection of traceframes, as per the trace file format.
36653 The reply consists as many hex-encoded bytes as the target can deliver
36654 in a packet; it is not an error to return fewer than were asked for.
36655 A reply consisting of just @code{l} indicates that no bytes are
36658 @item QTBuffer:circular:@var{value}
36659 This packet directs the target to use a circular trace buffer if
36660 @var{value} is 1, or a linear buffer if the value is 0.
36662 @item QTBuffer:size:@var{size}
36663 @anchor{QTBuffer-size}
36664 @cindex @samp{QTBuffer size} packet
36665 This packet directs the target to make the trace buffer be of size
36666 @var{size} if possible. A value of @code{-1} tells the target to
36667 use whatever size it prefers.
36669 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36670 @cindex @samp{QTNotes} packet
36671 This packet adds optional textual notes to the trace run. Allowable
36672 types include @code{user}, @code{notes}, and @code{tstop}, the
36673 @var{text} fields are arbitrary strings, hex-encoded.
36677 @subsection Relocate instruction reply packet
36678 When installing fast tracepoints in memory, the target may need to
36679 relocate the instruction currently at the tracepoint address to a
36680 different address in memory. For most instructions, a simple copy is
36681 enough, but, for example, call instructions that implicitly push the
36682 return address on the stack, and relative branches or other
36683 PC-relative instructions require offset adjustment, so that the effect
36684 of executing the instruction at a different address is the same as if
36685 it had executed in the original location.
36687 In response to several of the tracepoint packets, the target may also
36688 respond with a number of intermediate @samp{qRelocInsn} request
36689 packets before the final result packet, to have @value{GDBN} handle
36690 this relocation operation. If a packet supports this mechanism, its
36691 documentation will explicitly say so. See for example the above
36692 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36693 format of the request is:
36696 @item qRelocInsn:@var{from};@var{to}
36698 This requests @value{GDBN} to copy instruction at address @var{from}
36699 to address @var{to}, possibly adjusted so that executing the
36700 instruction at @var{to} has the same effect as executing it at
36701 @var{from}. @value{GDBN} writes the adjusted instruction to target
36702 memory starting at @var{to}.
36707 @item qRelocInsn:@var{adjusted_size}
36708 Informs the stub the relocation is complete. The @var{adjusted_size} is
36709 the length in bytes of resulting relocated instruction sequence.
36711 A badly formed request was detected, or an error was encountered while
36712 relocating the instruction.
36715 @node Host I/O Packets
36716 @section Host I/O Packets
36717 @cindex Host I/O, remote protocol
36718 @cindex file transfer, remote protocol
36720 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36721 operations on the far side of a remote link. For example, Host I/O is
36722 used to upload and download files to a remote target with its own
36723 filesystem. Host I/O uses the same constant values and data structure
36724 layout as the target-initiated File-I/O protocol. However, the
36725 Host I/O packets are structured differently. The target-initiated
36726 protocol relies on target memory to store parameters and buffers.
36727 Host I/O requests are initiated by @value{GDBN}, and the
36728 target's memory is not involved. @xref{File-I/O Remote Protocol
36729 Extension}, for more details on the target-initiated protocol.
36731 The Host I/O request packets all encode a single operation along with
36732 its arguments. They have this format:
36736 @item vFile:@var{operation}: @var{parameter}@dots{}
36737 @var{operation} is the name of the particular request; the target
36738 should compare the entire packet name up to the second colon when checking
36739 for a supported operation. The format of @var{parameter} depends on
36740 the operation. Numbers are always passed in hexadecimal. Negative
36741 numbers have an explicit minus sign (i.e.@: two's complement is not
36742 used). Strings (e.g.@: filenames) are encoded as a series of
36743 hexadecimal bytes. The last argument to a system call may be a
36744 buffer of escaped binary data (@pxref{Binary Data}).
36748 The valid responses to Host I/O packets are:
36752 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36753 @var{result} is the integer value returned by this operation, usually
36754 non-negative for success and -1 for errors. If an error has occured,
36755 @var{errno} will be included in the result specifying a
36756 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36757 operations which return data, @var{attachment} supplies the data as a
36758 binary buffer. Binary buffers in response packets are escaped in the
36759 normal way (@pxref{Binary Data}). See the individual packet
36760 documentation for the interpretation of @var{result} and
36764 An empty response indicates that this operation is not recognized.
36768 These are the supported Host I/O operations:
36771 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
36772 Open a file at @var{filename} and return a file descriptor for it, or
36773 return -1 if an error occurs. The @var{filename} is a string,
36774 @var{flags} is an integer indicating a mask of open flags
36775 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36776 of mode bits to use if the file is created (@pxref{mode_t Values}).
36777 @xref{open}, for details of the open flags and mode values.
36779 @item vFile:close: @var{fd}
36780 Close the open file corresponding to @var{fd} and return 0, or
36781 -1 if an error occurs.
36783 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36784 Read data from the open file corresponding to @var{fd}. Up to
36785 @var{count} bytes will be read from the file, starting at @var{offset}
36786 relative to the start of the file. The target may read fewer bytes;
36787 common reasons include packet size limits and an end-of-file
36788 condition. The number of bytes read is returned. Zero should only be
36789 returned for a successful read at the end of the file, or if
36790 @var{count} was zero.
36792 The data read should be returned as a binary attachment on success.
36793 If zero bytes were read, the response should include an empty binary
36794 attachment (i.e.@: a trailing semicolon). The return value is the
36795 number of target bytes read; the binary attachment may be longer if
36796 some characters were escaped.
36798 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36799 Write @var{data} (a binary buffer) to the open file corresponding
36800 to @var{fd}. Start the write at @var{offset} from the start of the
36801 file. Unlike many @code{write} system calls, there is no
36802 separate @var{count} argument; the length of @var{data} in the
36803 packet is used. @samp{vFile:write} returns the number of bytes written,
36804 which may be shorter than the length of @var{data}, or -1 if an
36807 @item vFile:unlink: @var{filename}
36808 Delete the file at @var{filename} on the target. Return 0,
36809 or -1 if an error occurs. The @var{filename} is a string.
36811 @item vFile:readlink: @var{filename}
36812 Read value of symbolic link @var{filename} on the target. Return
36813 the number of bytes read, or -1 if an error occurs.
36815 The data read should be returned as a binary attachment on success.
36816 If zero bytes were read, the response should include an empty binary
36817 attachment (i.e.@: a trailing semicolon). The return value is the
36818 number of target bytes read; the binary attachment may be longer if
36819 some characters were escaped.
36824 @section Interrupts
36825 @cindex interrupts (remote protocol)
36827 When a program on the remote target is running, @value{GDBN} may
36828 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36829 a @code{BREAK} followed by @code{g},
36830 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36832 The precise meaning of @code{BREAK} is defined by the transport
36833 mechanism and may, in fact, be undefined. @value{GDBN} does not
36834 currently define a @code{BREAK} mechanism for any of the network
36835 interfaces except for TCP, in which case @value{GDBN} sends the
36836 @code{telnet} BREAK sequence.
36838 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36839 transport mechanisms. It is represented by sending the single byte
36840 @code{0x03} without any of the usual packet overhead described in
36841 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36842 transmitted as part of a packet, it is considered to be packet data
36843 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36844 (@pxref{X packet}), used for binary downloads, may include an unescaped
36845 @code{0x03} as part of its packet.
36847 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36848 When Linux kernel receives this sequence from serial port,
36849 it stops execution and connects to gdb.
36851 Stubs are not required to recognize these interrupt mechanisms and the
36852 precise meaning associated with receipt of the interrupt is
36853 implementation defined. If the target supports debugging of multiple
36854 threads and/or processes, it should attempt to interrupt all
36855 currently-executing threads and processes.
36856 If the stub is successful at interrupting the
36857 running program, it should send one of the stop
36858 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36859 of successfully stopping the program in all-stop mode, and a stop reply
36860 for each stopped thread in non-stop mode.
36861 Interrupts received while the
36862 program is stopped are discarded.
36864 @node Notification Packets
36865 @section Notification Packets
36866 @cindex notification packets
36867 @cindex packets, notification
36869 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36870 packets that require no acknowledgment. Both the GDB and the stub
36871 may send notifications (although the only notifications defined at
36872 present are sent by the stub). Notifications carry information
36873 without incurring the round-trip latency of an acknowledgment, and so
36874 are useful for low-impact communications where occasional packet loss
36877 A notification packet has the form @samp{% @var{data} #
36878 @var{checksum}}, where @var{data} is the content of the notification,
36879 and @var{checksum} is a checksum of @var{data}, computed and formatted
36880 as for ordinary @value{GDBN} packets. A notification's @var{data}
36881 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36882 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36883 to acknowledge the notification's receipt or to report its corruption.
36885 Every notification's @var{data} begins with a name, which contains no
36886 colon characters, followed by a colon character.
36888 Recipients should silently ignore corrupted notifications and
36889 notifications they do not understand. Recipients should restart
36890 timeout periods on receipt of a well-formed notification, whether or
36891 not they understand it.
36893 Senders should only send the notifications described here when this
36894 protocol description specifies that they are permitted. In the
36895 future, we may extend the protocol to permit existing notifications in
36896 new contexts; this rule helps older senders avoid confusing newer
36899 (Older versions of @value{GDBN} ignore bytes received until they see
36900 the @samp{$} byte that begins an ordinary packet, so new stubs may
36901 transmit notifications without fear of confusing older clients. There
36902 are no notifications defined for @value{GDBN} to send at the moment, but we
36903 assume that most older stubs would ignore them, as well.)
36905 Each notification is comprised of three parts:
36907 @item @var{name}:@var{event}
36908 The notification packet is sent by the side that initiates the
36909 exchange (currently, only the stub does that), with @var{event}
36910 carrying the specific information about the notification, and
36911 @var{name} specifying the name of the notification.
36913 The acknowledge sent by the other side, usually @value{GDBN}, to
36914 acknowledge the exchange and request the event.
36917 The purpose of an asynchronous notification mechanism is to report to
36918 @value{GDBN} that something interesting happened in the remote stub.
36920 The remote stub may send notification @var{name}:@var{event}
36921 at any time, but @value{GDBN} acknowledges the notification when
36922 appropriate. The notification event is pending before @value{GDBN}
36923 acknowledges. Only one notification at a time may be pending; if
36924 additional events occur before @value{GDBN} has acknowledged the
36925 previous notification, they must be queued by the stub for later
36926 synchronous transmission in response to @var{ack} packets from
36927 @value{GDBN}. Because the notification mechanism is unreliable,
36928 the stub is permitted to resend a notification if it believes
36929 @value{GDBN} may not have received it.
36931 Specifically, notifications may appear when @value{GDBN} is not
36932 otherwise reading input from the stub, or when @value{GDBN} is
36933 expecting to read a normal synchronous response or a
36934 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36935 Notification packets are distinct from any other communication from
36936 the stub so there is no ambiguity.
36938 After receiving a notification, @value{GDBN} shall acknowledge it by
36939 sending a @var{ack} packet as a regular, synchronous request to the
36940 stub. Such acknowledgment is not required to happen immediately, as
36941 @value{GDBN} is permitted to send other, unrelated packets to the
36942 stub first, which the stub should process normally.
36944 Upon receiving a @var{ack} packet, if the stub has other queued
36945 events to report to @value{GDBN}, it shall respond by sending a
36946 normal @var{event}. @value{GDBN} shall then send another @var{ack}
36947 packet to solicit further responses; again, it is permitted to send
36948 other, unrelated packets as well which the stub should process
36951 If the stub receives a @var{ack} packet and there are no additional
36952 @var{event} to report, the stub shall return an @samp{OK} response.
36953 At this point, @value{GDBN} has finished processing a notification
36954 and the stub has completed sending any queued events. @value{GDBN}
36955 won't accept any new notifications until the final @samp{OK} is
36956 received . If further notification events occur, the stub shall send
36957 a new notification, @value{GDBN} shall accept the notification, and
36958 the process shall be repeated.
36960 The process of asynchronous notification can be illustrated by the
36963 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
36966 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
36968 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
36973 The following notifications are defined:
36974 @multitable @columnfractions 0.12 0.12 0.38 0.38
36983 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
36984 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36985 for information on how these notifications are acknowledged by
36987 @tab Report an asynchronous stop event in non-stop mode.
36991 @node Remote Non-Stop
36992 @section Remote Protocol Support for Non-Stop Mode
36994 @value{GDBN}'s remote protocol supports non-stop debugging of
36995 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36996 supports non-stop mode, it should report that to @value{GDBN} by including
36997 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36999 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37000 establishing a new connection with the stub. Entering non-stop mode
37001 does not alter the state of any currently-running threads, but targets
37002 must stop all threads in any already-attached processes when entering
37003 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37004 probe the target state after a mode change.
37006 In non-stop mode, when an attached process encounters an event that
37007 would otherwise be reported with a stop reply, it uses the
37008 asynchronous notification mechanism (@pxref{Notification Packets}) to
37009 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37010 in all processes are stopped when a stop reply is sent, in non-stop
37011 mode only the thread reporting the stop event is stopped. That is,
37012 when reporting a @samp{S} or @samp{T} response to indicate completion
37013 of a step operation, hitting a breakpoint, or a fault, only the
37014 affected thread is stopped; any other still-running threads continue
37015 to run. When reporting a @samp{W} or @samp{X} response, all running
37016 threads belonging to other attached processes continue to run.
37018 In non-stop mode, the target shall respond to the @samp{?} packet as
37019 follows. First, any incomplete stop reply notification/@samp{vStopped}
37020 sequence in progress is abandoned. The target must begin a new
37021 sequence reporting stop events for all stopped threads, whether or not
37022 it has previously reported those events to @value{GDBN}. The first
37023 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37024 subsequent stop replies are sent as responses to @samp{vStopped} packets
37025 using the mechanism described above. The target must not send
37026 asynchronous stop reply notifications until the sequence is complete.
37027 If all threads are running when the target receives the @samp{?} packet,
37028 or if the target is not attached to any process, it shall respond
37031 @node Packet Acknowledgment
37032 @section Packet Acknowledgment
37034 @cindex acknowledgment, for @value{GDBN} remote
37035 @cindex packet acknowledgment, for @value{GDBN} remote
37036 By default, when either the host or the target machine receives a packet,
37037 the first response expected is an acknowledgment: either @samp{+} (to indicate
37038 the package was received correctly) or @samp{-} (to request retransmission).
37039 This mechanism allows the @value{GDBN} remote protocol to operate over
37040 unreliable transport mechanisms, such as a serial line.
37042 In cases where the transport mechanism is itself reliable (such as a pipe or
37043 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37044 It may be desirable to disable them in that case to reduce communication
37045 overhead, or for other reasons. This can be accomplished by means of the
37046 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37048 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37049 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37050 and response format still includes the normal checksum, as described in
37051 @ref{Overview}, but the checksum may be ignored by the receiver.
37053 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37054 no-acknowledgment mode, it should report that to @value{GDBN}
37055 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37056 @pxref{qSupported}.
37057 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37058 disabled via the @code{set remote noack-packet off} command
37059 (@pxref{Remote Configuration}),
37060 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37061 Only then may the stub actually turn off packet acknowledgments.
37062 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37063 response, which can be safely ignored by the stub.
37065 Note that @code{set remote noack-packet} command only affects negotiation
37066 between @value{GDBN} and the stub when subsequent connections are made;
37067 it does not affect the protocol acknowledgment state for any current
37069 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37070 new connection is established,
37071 there is also no protocol request to re-enable the acknowledgments
37072 for the current connection, once disabled.
37077 Example sequence of a target being re-started. Notice how the restart
37078 does not get any direct output:
37083 @emph{target restarts}
37086 <- @code{T001:1234123412341234}
37090 Example sequence of a target being stepped by a single instruction:
37093 -> @code{G1445@dots{}}
37098 <- @code{T001:1234123412341234}
37102 <- @code{1455@dots{}}
37106 @node File-I/O Remote Protocol Extension
37107 @section File-I/O Remote Protocol Extension
37108 @cindex File-I/O remote protocol extension
37111 * File-I/O Overview::
37112 * Protocol Basics::
37113 * The F Request Packet::
37114 * The F Reply Packet::
37115 * The Ctrl-C Message::
37117 * List of Supported Calls::
37118 * Protocol-specific Representation of Datatypes::
37120 * File-I/O Examples::
37123 @node File-I/O Overview
37124 @subsection File-I/O Overview
37125 @cindex file-i/o overview
37127 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37128 target to use the host's file system and console I/O to perform various
37129 system calls. System calls on the target system are translated into a
37130 remote protocol packet to the host system, which then performs the needed
37131 actions and returns a response packet to the target system.
37132 This simulates file system operations even on targets that lack file systems.
37134 The protocol is defined to be independent of both the host and target systems.
37135 It uses its own internal representation of datatypes and values. Both
37136 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37137 translating the system-dependent value representations into the internal
37138 protocol representations when data is transmitted.
37140 The communication is synchronous. A system call is possible only when
37141 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37142 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37143 the target is stopped to allow deterministic access to the target's
37144 memory. Therefore File-I/O is not interruptible by target signals. On
37145 the other hand, it is possible to interrupt File-I/O by a user interrupt
37146 (@samp{Ctrl-C}) within @value{GDBN}.
37148 The target's request to perform a host system call does not finish
37149 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37150 after finishing the system call, the target returns to continuing the
37151 previous activity (continue, step). No additional continue or step
37152 request from @value{GDBN} is required.
37155 (@value{GDBP}) continue
37156 <- target requests 'system call X'
37157 target is stopped, @value{GDBN} executes system call
37158 -> @value{GDBN} returns result
37159 ... target continues, @value{GDBN} returns to wait for the target
37160 <- target hits breakpoint and sends a Txx packet
37163 The protocol only supports I/O on the console and to regular files on
37164 the host file system. Character or block special devices, pipes,
37165 named pipes, sockets or any other communication method on the host
37166 system are not supported by this protocol.
37168 File I/O is not supported in non-stop mode.
37170 @node Protocol Basics
37171 @subsection Protocol Basics
37172 @cindex protocol basics, file-i/o
37174 The File-I/O protocol uses the @code{F} packet as the request as well
37175 as reply packet. Since a File-I/O system call can only occur when
37176 @value{GDBN} is waiting for a response from the continuing or stepping target,
37177 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37178 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37179 This @code{F} packet contains all information needed to allow @value{GDBN}
37180 to call the appropriate host system call:
37184 A unique identifier for the requested system call.
37187 All parameters to the system call. Pointers are given as addresses
37188 in the target memory address space. Pointers to strings are given as
37189 pointer/length pair. Numerical values are given as they are.
37190 Numerical control flags are given in a protocol-specific representation.
37194 At this point, @value{GDBN} has to perform the following actions.
37198 If the parameters include pointer values to data needed as input to a
37199 system call, @value{GDBN} requests this data from the target with a
37200 standard @code{m} packet request. This additional communication has to be
37201 expected by the target implementation and is handled as any other @code{m}
37205 @value{GDBN} translates all value from protocol representation to host
37206 representation as needed. Datatypes are coerced into the host types.
37209 @value{GDBN} calls the system call.
37212 It then coerces datatypes back to protocol representation.
37215 If the system call is expected to return data in buffer space specified
37216 by pointer parameters to the call, the data is transmitted to the
37217 target using a @code{M} or @code{X} packet. This packet has to be expected
37218 by the target implementation and is handled as any other @code{M} or @code{X}
37223 Eventually @value{GDBN} replies with another @code{F} packet which contains all
37224 necessary information for the target to continue. This at least contains
37231 @code{errno}, if has been changed by the system call.
37238 After having done the needed type and value coercion, the target continues
37239 the latest continue or step action.
37241 @node The F Request Packet
37242 @subsection The @code{F} Request Packet
37243 @cindex file-i/o request packet
37244 @cindex @code{F} request packet
37246 The @code{F} request packet has the following format:
37249 @item F@var{call-id},@var{parameter@dots{}}
37251 @var{call-id} is the identifier to indicate the host system call to be called.
37252 This is just the name of the function.
37254 @var{parameter@dots{}} are the parameters to the system call.
37255 Parameters are hexadecimal integer values, either the actual values in case
37256 of scalar datatypes, pointers to target buffer space in case of compound
37257 datatypes and unspecified memory areas, or pointer/length pairs in case
37258 of string parameters. These are appended to the @var{call-id} as a
37259 comma-delimited list. All values are transmitted in ASCII
37260 string representation, pointer/length pairs separated by a slash.
37266 @node The F Reply Packet
37267 @subsection The @code{F} Reply Packet
37268 @cindex file-i/o reply packet
37269 @cindex @code{F} reply packet
37271 The @code{F} reply packet has the following format:
37275 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
37277 @var{retcode} is the return code of the system call as hexadecimal value.
37279 @var{errno} is the @code{errno} set by the call, in protocol-specific
37281 This parameter can be omitted if the call was successful.
37283 @var{Ctrl-C flag} is only sent if the user requested a break. In this
37284 case, @var{errno} must be sent as well, even if the call was successful.
37285 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
37292 or, if the call was interrupted before the host call has been performed:
37299 assuming 4 is the protocol-specific representation of @code{EINTR}.
37304 @node The Ctrl-C Message
37305 @subsection The @samp{Ctrl-C} Message
37306 @cindex ctrl-c message, in file-i/o protocol
37308 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
37309 reply packet (@pxref{The F Reply Packet}),
37310 the target should behave as if it had
37311 gotten a break message. The meaning for the target is ``system call
37312 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
37313 (as with a break message) and return to @value{GDBN} with a @code{T02}
37316 It's important for the target to know in which
37317 state the system call was interrupted. There are two possible cases:
37321 The system call hasn't been performed on the host yet.
37324 The system call on the host has been finished.
37328 These two states can be distinguished by the target by the value of the
37329 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
37330 call hasn't been performed. This is equivalent to the @code{EINTR} handling
37331 on POSIX systems. In any other case, the target may presume that the
37332 system call has been finished --- successfully or not --- and should behave
37333 as if the break message arrived right after the system call.
37335 @value{GDBN} must behave reliably. If the system call has not been called
37336 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
37337 @code{errno} in the packet. If the system call on the host has been finished
37338 before the user requests a break, the full action must be finished by
37339 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
37340 The @code{F} packet may only be sent when either nothing has happened
37341 or the full action has been completed.
37344 @subsection Console I/O
37345 @cindex console i/o as part of file-i/o
37347 By default and if not explicitly closed by the target system, the file
37348 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
37349 on the @value{GDBN} console is handled as any other file output operation
37350 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
37351 by @value{GDBN} so that after the target read request from file descriptor
37352 0 all following typing is buffered until either one of the following
37357 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37359 system call is treated as finished.
37362 The user presses @key{RET}. This is treated as end of input with a trailing
37366 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37367 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37371 If the user has typed more characters than fit in the buffer given to
37372 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37373 either another @code{read(0, @dots{})} is requested by the target, or debugging
37374 is stopped at the user's request.
37377 @node List of Supported Calls
37378 @subsection List of Supported Calls
37379 @cindex list of supported file-i/o calls
37396 @unnumberedsubsubsec open
37397 @cindex open, file-i/o system call
37402 int open(const char *pathname, int flags);
37403 int open(const char *pathname, int flags, mode_t mode);
37407 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37410 @var{flags} is the bitwise @code{OR} of the following values:
37414 If the file does not exist it will be created. The host
37415 rules apply as far as file ownership and time stamps
37419 When used with @code{O_CREAT}, if the file already exists it is
37420 an error and open() fails.
37423 If the file already exists and the open mode allows
37424 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37425 truncated to zero length.
37428 The file is opened in append mode.
37431 The file is opened for reading only.
37434 The file is opened for writing only.
37437 The file is opened for reading and writing.
37441 Other bits are silently ignored.
37445 @var{mode} is the bitwise @code{OR} of the following values:
37449 User has read permission.
37452 User has write permission.
37455 Group has read permission.
37458 Group has write permission.
37461 Others have read permission.
37464 Others have write permission.
37468 Other bits are silently ignored.
37471 @item Return value:
37472 @code{open} returns the new file descriptor or -1 if an error
37479 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37482 @var{pathname} refers to a directory.
37485 The requested access is not allowed.
37488 @var{pathname} was too long.
37491 A directory component in @var{pathname} does not exist.
37494 @var{pathname} refers to a device, pipe, named pipe or socket.
37497 @var{pathname} refers to a file on a read-only filesystem and
37498 write access was requested.
37501 @var{pathname} is an invalid pointer value.
37504 No space on device to create the file.
37507 The process already has the maximum number of files open.
37510 The limit on the total number of files open on the system
37514 The call was interrupted by the user.
37520 @unnumberedsubsubsec close
37521 @cindex close, file-i/o system call
37530 @samp{Fclose,@var{fd}}
37532 @item Return value:
37533 @code{close} returns zero on success, or -1 if an error occurred.
37539 @var{fd} isn't a valid open file descriptor.
37542 The call was interrupted by the user.
37548 @unnumberedsubsubsec read
37549 @cindex read, file-i/o system call
37554 int read(int fd, void *buf, unsigned int count);
37558 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37560 @item Return value:
37561 On success, the number of bytes read is returned.
37562 Zero indicates end of file. If count is zero, read
37563 returns zero as well. On error, -1 is returned.
37569 @var{fd} is not a valid file descriptor or is not open for
37573 @var{bufptr} is an invalid pointer value.
37576 The call was interrupted by the user.
37582 @unnumberedsubsubsec write
37583 @cindex write, file-i/o system call
37588 int write(int fd, const void *buf, unsigned int count);
37592 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37594 @item Return value:
37595 On success, the number of bytes written are returned.
37596 Zero indicates nothing was written. On error, -1
37603 @var{fd} is not a valid file descriptor or is not open for
37607 @var{bufptr} is an invalid pointer value.
37610 An attempt was made to write a file that exceeds the
37611 host-specific maximum file size allowed.
37614 No space on device to write the data.
37617 The call was interrupted by the user.
37623 @unnumberedsubsubsec lseek
37624 @cindex lseek, file-i/o system call
37629 long lseek (int fd, long offset, int flag);
37633 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37635 @var{flag} is one of:
37639 The offset is set to @var{offset} bytes.
37642 The offset is set to its current location plus @var{offset}
37646 The offset is set to the size of the file plus @var{offset}
37650 @item Return value:
37651 On success, the resulting unsigned offset in bytes from
37652 the beginning of the file is returned. Otherwise, a
37653 value of -1 is returned.
37659 @var{fd} is not a valid open file descriptor.
37662 @var{fd} is associated with the @value{GDBN} console.
37665 @var{flag} is not a proper value.
37668 The call was interrupted by the user.
37674 @unnumberedsubsubsec rename
37675 @cindex rename, file-i/o system call
37680 int rename(const char *oldpath, const char *newpath);
37684 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37686 @item Return value:
37687 On success, zero is returned. On error, -1 is returned.
37693 @var{newpath} is an existing directory, but @var{oldpath} is not a
37697 @var{newpath} is a non-empty directory.
37700 @var{oldpath} or @var{newpath} is a directory that is in use by some
37704 An attempt was made to make a directory a subdirectory
37708 A component used as a directory in @var{oldpath} or new
37709 path is not a directory. Or @var{oldpath} is a directory
37710 and @var{newpath} exists but is not a directory.
37713 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37716 No access to the file or the path of the file.
37720 @var{oldpath} or @var{newpath} was too long.
37723 A directory component in @var{oldpath} or @var{newpath} does not exist.
37726 The file is on a read-only filesystem.
37729 The device containing the file has no room for the new
37733 The call was interrupted by the user.
37739 @unnumberedsubsubsec unlink
37740 @cindex unlink, file-i/o system call
37745 int unlink(const char *pathname);
37749 @samp{Funlink,@var{pathnameptr}/@var{len}}
37751 @item Return value:
37752 On success, zero is returned. On error, -1 is returned.
37758 No access to the file or the path of the file.
37761 The system does not allow unlinking of directories.
37764 The file @var{pathname} cannot be unlinked because it's
37765 being used by another process.
37768 @var{pathnameptr} is an invalid pointer value.
37771 @var{pathname} was too long.
37774 A directory component in @var{pathname} does not exist.
37777 A component of the path is not a directory.
37780 The file is on a read-only filesystem.
37783 The call was interrupted by the user.
37789 @unnumberedsubsubsec stat/fstat
37790 @cindex fstat, file-i/o system call
37791 @cindex stat, file-i/o system call
37796 int stat(const char *pathname, struct stat *buf);
37797 int fstat(int fd, struct stat *buf);
37801 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37802 @samp{Ffstat,@var{fd},@var{bufptr}}
37804 @item Return value:
37805 On success, zero is returned. On error, -1 is returned.
37811 @var{fd} is not a valid open file.
37814 A directory component in @var{pathname} does not exist or the
37815 path is an empty string.
37818 A component of the path is not a directory.
37821 @var{pathnameptr} is an invalid pointer value.
37824 No access to the file or the path of the file.
37827 @var{pathname} was too long.
37830 The call was interrupted by the user.
37836 @unnumberedsubsubsec gettimeofday
37837 @cindex gettimeofday, file-i/o system call
37842 int gettimeofday(struct timeval *tv, void *tz);
37846 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37848 @item Return value:
37849 On success, 0 is returned, -1 otherwise.
37855 @var{tz} is a non-NULL pointer.
37858 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37864 @unnumberedsubsubsec isatty
37865 @cindex isatty, file-i/o system call
37870 int isatty(int fd);
37874 @samp{Fisatty,@var{fd}}
37876 @item Return value:
37877 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37883 The call was interrupted by the user.
37888 Note that the @code{isatty} call is treated as a special case: it returns
37889 1 to the target if the file descriptor is attached
37890 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37891 would require implementing @code{ioctl} and would be more complex than
37896 @unnumberedsubsubsec system
37897 @cindex system, file-i/o system call
37902 int system(const char *command);
37906 @samp{Fsystem,@var{commandptr}/@var{len}}
37908 @item Return value:
37909 If @var{len} is zero, the return value indicates whether a shell is
37910 available. A zero return value indicates a shell is not available.
37911 For non-zero @var{len}, the value returned is -1 on error and the
37912 return status of the command otherwise. Only the exit status of the
37913 command is returned, which is extracted from the host's @code{system}
37914 return value by calling @code{WEXITSTATUS(retval)}. In case
37915 @file{/bin/sh} could not be executed, 127 is returned.
37921 The call was interrupted by the user.
37926 @value{GDBN} takes over the full task of calling the necessary host calls
37927 to perform the @code{system} call. The return value of @code{system} on
37928 the host is simplified before it's returned
37929 to the target. Any termination signal information from the child process
37930 is discarded, and the return value consists
37931 entirely of the exit status of the called command.
37933 Due to security concerns, the @code{system} call is by default refused
37934 by @value{GDBN}. The user has to allow this call explicitly with the
37935 @code{set remote system-call-allowed 1} command.
37938 @item set remote system-call-allowed
37939 @kindex set remote system-call-allowed
37940 Control whether to allow the @code{system} calls in the File I/O
37941 protocol for the remote target. The default is zero (disabled).
37943 @item show remote system-call-allowed
37944 @kindex show remote system-call-allowed
37945 Show whether the @code{system} calls are allowed in the File I/O
37949 @node Protocol-specific Representation of Datatypes
37950 @subsection Protocol-specific Representation of Datatypes
37951 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37954 * Integral Datatypes::
37956 * Memory Transfer::
37961 @node Integral Datatypes
37962 @unnumberedsubsubsec Integral Datatypes
37963 @cindex integral datatypes, in file-i/o protocol
37965 The integral datatypes used in the system calls are @code{int},
37966 @code{unsigned int}, @code{long}, @code{unsigned long},
37967 @code{mode_t}, and @code{time_t}.
37969 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37970 implemented as 32 bit values in this protocol.
37972 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37974 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37975 in @file{limits.h}) to allow range checking on host and target.
37977 @code{time_t} datatypes are defined as seconds since the Epoch.
37979 All integral datatypes transferred as part of a memory read or write of a
37980 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37983 @node Pointer Values
37984 @unnumberedsubsubsec Pointer Values
37985 @cindex pointer values, in file-i/o protocol
37987 Pointers to target data are transmitted as they are. An exception
37988 is made for pointers to buffers for which the length isn't
37989 transmitted as part of the function call, namely strings. Strings
37990 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37997 which is a pointer to data of length 18 bytes at position 0x1aaf.
37998 The length is defined as the full string length in bytes, including
37999 the trailing null byte. For example, the string @code{"hello world"}
38000 at address 0x123456 is transmitted as
38006 @node Memory Transfer
38007 @unnumberedsubsubsec Memory Transfer
38008 @cindex memory transfer, in file-i/o protocol
38010 Structured data which is transferred using a memory read or write (for
38011 example, a @code{struct stat}) is expected to be in a protocol-specific format
38012 with all scalar multibyte datatypes being big endian. Translation to
38013 this representation needs to be done both by the target before the @code{F}
38014 packet is sent, and by @value{GDBN} before
38015 it transfers memory to the target. Transferred pointers to structured
38016 data should point to the already-coerced data at any time.
38020 @unnumberedsubsubsec struct stat
38021 @cindex struct stat, in file-i/o protocol
38023 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38024 is defined as follows:
38028 unsigned int st_dev; /* device */
38029 unsigned int st_ino; /* inode */
38030 mode_t st_mode; /* protection */
38031 unsigned int st_nlink; /* number of hard links */
38032 unsigned int st_uid; /* user ID of owner */
38033 unsigned int st_gid; /* group ID of owner */
38034 unsigned int st_rdev; /* device type (if inode device) */
38035 unsigned long st_size; /* total size, in bytes */
38036 unsigned long st_blksize; /* blocksize for filesystem I/O */
38037 unsigned long st_blocks; /* number of blocks allocated */
38038 time_t st_atime; /* time of last access */
38039 time_t st_mtime; /* time of last modification */
38040 time_t st_ctime; /* time of last change */
38044 The integral datatypes conform to the definitions given in the
38045 appropriate section (see @ref{Integral Datatypes}, for details) so this
38046 structure is of size 64 bytes.
38048 The values of several fields have a restricted meaning and/or
38054 A value of 0 represents a file, 1 the console.
38057 No valid meaning for the target. Transmitted unchanged.
38060 Valid mode bits are described in @ref{Constants}. Any other
38061 bits have currently no meaning for the target.
38066 No valid meaning for the target. Transmitted unchanged.
38071 These values have a host and file system dependent
38072 accuracy. Especially on Windows hosts, the file system may not
38073 support exact timing values.
38076 The target gets a @code{struct stat} of the above representation and is
38077 responsible for coercing it to the target representation before
38080 Note that due to size differences between the host, target, and protocol
38081 representations of @code{struct stat} members, these members could eventually
38082 get truncated on the target.
38084 @node struct timeval
38085 @unnumberedsubsubsec struct timeval
38086 @cindex struct timeval, in file-i/o protocol
38088 The buffer of type @code{struct timeval} used by the File-I/O protocol
38089 is defined as follows:
38093 time_t tv_sec; /* second */
38094 long tv_usec; /* microsecond */
38098 The integral datatypes conform to the definitions given in the
38099 appropriate section (see @ref{Integral Datatypes}, for details) so this
38100 structure is of size 8 bytes.
38103 @subsection Constants
38104 @cindex constants, in file-i/o protocol
38106 The following values are used for the constants inside of the
38107 protocol. @value{GDBN} and target are responsible for translating these
38108 values before and after the call as needed.
38119 @unnumberedsubsubsec Open Flags
38120 @cindex open flags, in file-i/o protocol
38122 All values are given in hexadecimal representation.
38134 @node mode_t Values
38135 @unnumberedsubsubsec mode_t Values
38136 @cindex mode_t values, in file-i/o protocol
38138 All values are given in octal representation.
38155 @unnumberedsubsubsec Errno Values
38156 @cindex errno values, in file-i/o protocol
38158 All values are given in decimal representation.
38183 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38184 any error value not in the list of supported error numbers.
38187 @unnumberedsubsubsec Lseek Flags
38188 @cindex lseek flags, in file-i/o protocol
38197 @unnumberedsubsubsec Limits
38198 @cindex limits, in file-i/o protocol
38200 All values are given in decimal representation.
38203 INT_MIN -2147483648
38205 UINT_MAX 4294967295
38206 LONG_MIN -9223372036854775808
38207 LONG_MAX 9223372036854775807
38208 ULONG_MAX 18446744073709551615
38211 @node File-I/O Examples
38212 @subsection File-I/O Examples
38213 @cindex file-i/o examples
38215 Example sequence of a write call, file descriptor 3, buffer is at target
38216 address 0x1234, 6 bytes should be written:
38219 <- @code{Fwrite,3,1234,6}
38220 @emph{request memory read from target}
38223 @emph{return "6 bytes written"}
38227 Example sequence of a read call, file descriptor 3, buffer is at target
38228 address 0x1234, 6 bytes should be read:
38231 <- @code{Fread,3,1234,6}
38232 @emph{request memory write to target}
38233 -> @code{X1234,6:XXXXXX}
38234 @emph{return "6 bytes read"}
38238 Example sequence of a read call, call fails on the host due to invalid
38239 file descriptor (@code{EBADF}):
38242 <- @code{Fread,3,1234,6}
38246 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
38250 <- @code{Fread,3,1234,6}
38255 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
38259 <- @code{Fread,3,1234,6}
38260 -> @code{X1234,6:XXXXXX}
38264 @node Library List Format
38265 @section Library List Format
38266 @cindex library list format, remote protocol
38268 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
38269 same process as your application to manage libraries. In this case,
38270 @value{GDBN} can use the loader's symbol table and normal memory
38271 operations to maintain a list of shared libraries. On other
38272 platforms, the operating system manages loaded libraries.
38273 @value{GDBN} can not retrieve the list of currently loaded libraries
38274 through memory operations, so it uses the @samp{qXfer:libraries:read}
38275 packet (@pxref{qXfer library list read}) instead. The remote stub
38276 queries the target's operating system and reports which libraries
38279 The @samp{qXfer:libraries:read} packet returns an XML document which
38280 lists loaded libraries and their offsets. Each library has an
38281 associated name and one or more segment or section base addresses,
38282 which report where the library was loaded in memory.
38284 For the common case of libraries that are fully linked binaries, the
38285 library should have a list of segments. If the target supports
38286 dynamic linking of a relocatable object file, its library XML element
38287 should instead include a list of allocated sections. The segment or
38288 section bases are start addresses, not relocation offsets; they do not
38289 depend on the library's link-time base addresses.
38291 @value{GDBN} must be linked with the Expat library to support XML
38292 library lists. @xref{Expat}.
38294 A simple memory map, with one loaded library relocated by a single
38295 offset, looks like this:
38299 <library name="/lib/libc.so.6">
38300 <segment address="0x10000000"/>
38305 Another simple memory map, with one loaded library with three
38306 allocated sections (.text, .data, .bss), looks like this:
38310 <library name="sharedlib.o">
38311 <section address="0x10000000"/>
38312 <section address="0x20000000"/>
38313 <section address="0x30000000"/>
38318 The format of a library list is described by this DTD:
38321 <!-- library-list: Root element with versioning -->
38322 <!ELEMENT library-list (library)*>
38323 <!ATTLIST library-list version CDATA #FIXED "1.0">
38324 <!ELEMENT library (segment*, section*)>
38325 <!ATTLIST library name CDATA #REQUIRED>
38326 <!ELEMENT segment EMPTY>
38327 <!ATTLIST segment address CDATA #REQUIRED>
38328 <!ELEMENT section EMPTY>
38329 <!ATTLIST section address CDATA #REQUIRED>
38332 In addition, segments and section descriptors cannot be mixed within a
38333 single library element, and you must supply at least one segment or
38334 section for each library.
38336 @node Library List Format for SVR4 Targets
38337 @section Library List Format for SVR4 Targets
38338 @cindex library list format, remote protocol
38340 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
38341 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
38342 shared libraries. Still a special library list provided by this packet is
38343 more efficient for the @value{GDBN} remote protocol.
38345 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
38346 loaded libraries and their SVR4 linker parameters. For each library on SVR4
38347 target, the following parameters are reported:
38351 @code{name}, the absolute file name from the @code{l_name} field of
38352 @code{struct link_map}.
38354 @code{lm} with address of @code{struct link_map} used for TLS
38355 (Thread Local Storage) access.
38357 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38358 @code{struct link_map}. For prelinked libraries this is not an absolute
38359 memory address. It is a displacement of absolute memory address against
38360 address the file was prelinked to during the library load.
38362 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38365 Additionally the single @code{main-lm} attribute specifies address of
38366 @code{struct link_map} used for the main executable. This parameter is used
38367 for TLS access and its presence is optional.
38369 @value{GDBN} must be linked with the Expat library to support XML
38370 SVR4 library lists. @xref{Expat}.
38372 A simple memory map, with two loaded libraries (which do not use prelink),
38376 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38377 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38379 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38381 </library-list-svr>
38384 The format of an SVR4 library list is described by this DTD:
38387 <!-- library-list-svr4: Root element with versioning -->
38388 <!ELEMENT library-list-svr4 (library)*>
38389 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38390 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38391 <!ELEMENT library EMPTY>
38392 <!ATTLIST library name CDATA #REQUIRED>
38393 <!ATTLIST library lm CDATA #REQUIRED>
38394 <!ATTLIST library l_addr CDATA #REQUIRED>
38395 <!ATTLIST library l_ld CDATA #REQUIRED>
38398 @node Memory Map Format
38399 @section Memory Map Format
38400 @cindex memory map format
38402 To be able to write into flash memory, @value{GDBN} needs to obtain a
38403 memory map from the target. This section describes the format of the
38406 The memory map is obtained using the @samp{qXfer:memory-map:read}
38407 (@pxref{qXfer memory map read}) packet and is an XML document that
38408 lists memory regions.
38410 @value{GDBN} must be linked with the Expat library to support XML
38411 memory maps. @xref{Expat}.
38413 The top-level structure of the document is shown below:
38416 <?xml version="1.0"?>
38417 <!DOCTYPE memory-map
38418 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38419 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38425 Each region can be either:
38430 A region of RAM starting at @var{addr} and extending for @var{length}
38434 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38439 A region of read-only memory:
38442 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38447 A region of flash memory, with erasure blocks @var{blocksize}
38451 <memory type="flash" start="@var{addr}" length="@var{length}">
38452 <property name="blocksize">@var{blocksize}</property>
38458 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38459 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38460 packets to write to addresses in such ranges.
38462 The formal DTD for memory map format is given below:
38465 <!-- ................................................... -->
38466 <!-- Memory Map XML DTD ................................ -->
38467 <!-- File: memory-map.dtd .............................. -->
38468 <!-- .................................... .............. -->
38469 <!-- memory-map.dtd -->
38470 <!-- memory-map: Root element with versioning -->
38471 <!ELEMENT memory-map (memory | property)>
38472 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38473 <!ELEMENT memory (property)>
38474 <!-- memory: Specifies a memory region,
38475 and its type, or device. -->
38476 <!ATTLIST memory type CDATA #REQUIRED
38477 start CDATA #REQUIRED
38478 length CDATA #REQUIRED
38479 device CDATA #IMPLIED>
38480 <!-- property: Generic attribute tag -->
38481 <!ELEMENT property (#PCDATA | property)*>
38482 <!ATTLIST property name CDATA #REQUIRED>
38485 @node Thread List Format
38486 @section Thread List Format
38487 @cindex thread list format
38489 To efficiently update the list of threads and their attributes,
38490 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38491 (@pxref{qXfer threads read}) and obtains the XML document with
38492 the following structure:
38495 <?xml version="1.0"?>
38497 <thread id="id" core="0">
38498 ... description ...
38503 Each @samp{thread} element must have the @samp{id} attribute that
38504 identifies the thread (@pxref{thread-id syntax}). The
38505 @samp{core} attribute, if present, specifies which processor core
38506 the thread was last executing on. The content of the of @samp{thread}
38507 element is interpreted as human-readable auxilliary information.
38509 @node Traceframe Info Format
38510 @section Traceframe Info Format
38511 @cindex traceframe info format
38513 To be able to know which objects in the inferior can be examined when
38514 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38515 memory ranges, registers and trace state variables that have been
38516 collected in a traceframe.
38518 This list is obtained using the @samp{qXfer:traceframe-info:read}
38519 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38521 @value{GDBN} must be linked with the Expat library to support XML
38522 traceframe info discovery. @xref{Expat}.
38524 The top-level structure of the document is shown below:
38527 <?xml version="1.0"?>
38528 <!DOCTYPE traceframe-info
38529 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38530 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38536 Each traceframe block can be either:
38541 A region of collected memory starting at @var{addr} and extending for
38542 @var{length} bytes from there:
38545 <memory start="@var{addr}" length="@var{length}"/>
38549 A block indicating trace state variable numbered @var{number} has been
38553 <tvar id="@var{number}"/>
38558 The formal DTD for the traceframe info format is given below:
38561 <!ELEMENT traceframe-info (memory | tvar)* >
38562 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38564 <!ELEMENT memory EMPTY>
38565 <!ATTLIST memory start CDATA #REQUIRED
38566 length CDATA #REQUIRED>
38568 <!ATTLIST tvar id CDATA #REQUIRED>
38571 @node Branch Trace Format
38572 @section Branch Trace Format
38573 @cindex branch trace format
38575 In order to display the branch trace of an inferior thread,
38576 @value{GDBN} needs to obtain the list of branches. This list is
38577 represented as list of sequential code blocks that are connected via
38578 branches. The code in each block has been executed sequentially.
38580 This list is obtained using the @samp{qXfer:btrace:read}
38581 (@pxref{qXfer btrace read}) packet and is an XML document.
38583 @value{GDBN} must be linked with the Expat library to support XML
38584 traceframe info discovery. @xref{Expat}.
38586 The top-level structure of the document is shown below:
38589 <?xml version="1.0"?>
38591 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
38592 "http://sourceware.org/gdb/gdb-btrace.dtd">
38601 A block of sequentially executed instructions starting at @var{begin}
38602 and ending at @var{end}:
38605 <block begin="@var{begin}" end="@var{end}"/>
38610 The formal DTD for the branch trace format is given below:
38613 <!ELEMENT btrace (block)* >
38614 <!ATTLIST btrace version CDATA #FIXED "1.0">
38616 <!ELEMENT block EMPTY>
38617 <!ATTLIST block begin CDATA #REQUIRED
38618 end CDATA #REQUIRED>
38621 @include agentexpr.texi
38623 @node Target Descriptions
38624 @appendix Target Descriptions
38625 @cindex target descriptions
38627 One of the challenges of using @value{GDBN} to debug embedded systems
38628 is that there are so many minor variants of each processor
38629 architecture in use. It is common practice for vendors to start with
38630 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
38631 and then make changes to adapt it to a particular market niche. Some
38632 architectures have hundreds of variants, available from dozens of
38633 vendors. This leads to a number of problems:
38637 With so many different customized processors, it is difficult for
38638 the @value{GDBN} maintainers to keep up with the changes.
38640 Since individual variants may have short lifetimes or limited
38641 audiences, it may not be worthwhile to carry information about every
38642 variant in the @value{GDBN} source tree.
38644 When @value{GDBN} does support the architecture of the embedded system
38645 at hand, the task of finding the correct architecture name to give the
38646 @command{set architecture} command can be error-prone.
38649 To address these problems, the @value{GDBN} remote protocol allows a
38650 target system to not only identify itself to @value{GDBN}, but to
38651 actually describe its own features. This lets @value{GDBN} support
38652 processor variants it has never seen before --- to the extent that the
38653 descriptions are accurate, and that @value{GDBN} understands them.
38655 @value{GDBN} must be linked with the Expat library to support XML
38656 target descriptions. @xref{Expat}.
38659 * Retrieving Descriptions:: How descriptions are fetched from a target.
38660 * Target Description Format:: The contents of a target description.
38661 * Predefined Target Types:: Standard types available for target
38663 * Standard Target Features:: Features @value{GDBN} knows about.
38666 @node Retrieving Descriptions
38667 @section Retrieving Descriptions
38669 Target descriptions can be read from the target automatically, or
38670 specified by the user manually. The default behavior is to read the
38671 description from the target. @value{GDBN} retrieves it via the remote
38672 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38673 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38674 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38675 XML document, of the form described in @ref{Target Description
38678 Alternatively, you can specify a file to read for the target description.
38679 If a file is set, the target will not be queried. The commands to
38680 specify a file are:
38683 @cindex set tdesc filename
38684 @item set tdesc filename @var{path}
38685 Read the target description from @var{path}.
38687 @cindex unset tdesc filename
38688 @item unset tdesc filename
38689 Do not read the XML target description from a file. @value{GDBN}
38690 will use the description supplied by the current target.
38692 @cindex show tdesc filename
38693 @item show tdesc filename
38694 Show the filename to read for a target description, if any.
38698 @node Target Description Format
38699 @section Target Description Format
38700 @cindex target descriptions, XML format
38702 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38703 document which complies with the Document Type Definition provided in
38704 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38705 means you can use generally available tools like @command{xmllint} to
38706 check that your feature descriptions are well-formed and valid.
38707 However, to help people unfamiliar with XML write descriptions for
38708 their targets, we also describe the grammar here.
38710 Target descriptions can identify the architecture of the remote target
38711 and (for some architectures) provide information about custom register
38712 sets. They can also identify the OS ABI of the remote target.
38713 @value{GDBN} can use this information to autoconfigure for your
38714 target, or to warn you if you connect to an unsupported target.
38716 Here is a simple target description:
38719 <target version="1.0">
38720 <architecture>i386:x86-64</architecture>
38725 This minimal description only says that the target uses
38726 the x86-64 architecture.
38728 A target description has the following overall form, with [ ] marking
38729 optional elements and @dots{} marking repeatable elements. The elements
38730 are explained further below.
38733 <?xml version="1.0"?>
38734 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38735 <target version="1.0">
38736 @r{[}@var{architecture}@r{]}
38737 @r{[}@var{osabi}@r{]}
38738 @r{[}@var{compatible}@r{]}
38739 @r{[}@var{feature}@dots{}@r{]}
38744 The description is generally insensitive to whitespace and line
38745 breaks, under the usual common-sense rules. The XML version
38746 declaration and document type declaration can generally be omitted
38747 (@value{GDBN} does not require them), but specifying them may be
38748 useful for XML validation tools. The @samp{version} attribute for
38749 @samp{<target>} may also be omitted, but we recommend
38750 including it; if future versions of @value{GDBN} use an incompatible
38751 revision of @file{gdb-target.dtd}, they will detect and report
38752 the version mismatch.
38754 @subsection Inclusion
38755 @cindex target descriptions, inclusion
38758 @cindex <xi:include>
38761 It can sometimes be valuable to split a target description up into
38762 several different annexes, either for organizational purposes, or to
38763 share files between different possible target descriptions. You can
38764 divide a description into multiple files by replacing any element of
38765 the target description with an inclusion directive of the form:
38768 <xi:include href="@var{document}"/>
38772 When @value{GDBN} encounters an element of this form, it will retrieve
38773 the named XML @var{document}, and replace the inclusion directive with
38774 the contents of that document. If the current description was read
38775 using @samp{qXfer}, then so will be the included document;
38776 @var{document} will be interpreted as the name of an annex. If the
38777 current description was read from a file, @value{GDBN} will look for
38778 @var{document} as a file in the same directory where it found the
38779 original description.
38781 @subsection Architecture
38782 @cindex <architecture>
38784 An @samp{<architecture>} element has this form:
38787 <architecture>@var{arch}</architecture>
38790 @var{arch} is one of the architectures from the set accepted by
38791 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38794 @cindex @code{<osabi>}
38796 This optional field was introduced in @value{GDBN} version 7.0.
38797 Previous versions of @value{GDBN} ignore it.
38799 An @samp{<osabi>} element has this form:
38802 <osabi>@var{abi-name}</osabi>
38805 @var{abi-name} is an OS ABI name from the same selection accepted by
38806 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38808 @subsection Compatible Architecture
38809 @cindex @code{<compatible>}
38811 This optional field was introduced in @value{GDBN} version 7.0.
38812 Previous versions of @value{GDBN} ignore it.
38814 A @samp{<compatible>} element has this form:
38817 <compatible>@var{arch}</compatible>
38820 @var{arch} is one of the architectures from the set accepted by
38821 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38823 A @samp{<compatible>} element is used to specify that the target
38824 is able to run binaries in some other than the main target architecture
38825 given by the @samp{<architecture>} element. For example, on the
38826 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38827 or @code{powerpc:common64}, but the system is able to run binaries
38828 in the @code{spu} architecture as well. The way to describe this
38829 capability with @samp{<compatible>} is as follows:
38832 <architecture>powerpc:common</architecture>
38833 <compatible>spu</compatible>
38836 @subsection Features
38839 Each @samp{<feature>} describes some logical portion of the target
38840 system. Features are currently used to describe available CPU
38841 registers and the types of their contents. A @samp{<feature>} element
38845 <feature name="@var{name}">
38846 @r{[}@var{type}@dots{}@r{]}
38852 Each feature's name should be unique within the description. The name
38853 of a feature does not matter unless @value{GDBN} has some special
38854 knowledge of the contents of that feature; if it does, the feature
38855 should have its standard name. @xref{Standard Target Features}.
38859 Any register's value is a collection of bits which @value{GDBN} must
38860 interpret. The default interpretation is a two's complement integer,
38861 but other types can be requested by name in the register description.
38862 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38863 Target Types}), and the description can define additional composite types.
38865 Each type element must have an @samp{id} attribute, which gives
38866 a unique (within the containing @samp{<feature>}) name to the type.
38867 Types must be defined before they are used.
38870 Some targets offer vector registers, which can be treated as arrays
38871 of scalar elements. These types are written as @samp{<vector>} elements,
38872 specifying the array element type, @var{type}, and the number of elements,
38876 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38880 If a register's value is usefully viewed in multiple ways, define it
38881 with a union type containing the useful representations. The
38882 @samp{<union>} element contains one or more @samp{<field>} elements,
38883 each of which has a @var{name} and a @var{type}:
38886 <union id="@var{id}">
38887 <field name="@var{name}" type="@var{type}"/>
38893 If a register's value is composed from several separate values, define
38894 it with a structure type. There are two forms of the @samp{<struct>}
38895 element; a @samp{<struct>} element must either contain only bitfields
38896 or contain no bitfields. If the structure contains only bitfields,
38897 its total size in bytes must be specified, each bitfield must have an
38898 explicit start and end, and bitfields are automatically assigned an
38899 integer type. The field's @var{start} should be less than or
38900 equal to its @var{end}, and zero represents the least significant bit.
38903 <struct id="@var{id}" size="@var{size}">
38904 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38909 If the structure contains no bitfields, then each field has an
38910 explicit type, and no implicit padding is added.
38913 <struct id="@var{id}">
38914 <field name="@var{name}" type="@var{type}"/>
38920 If a register's value is a series of single-bit flags, define it with
38921 a flags type. The @samp{<flags>} element has an explicit @var{size}
38922 and contains one or more @samp{<field>} elements. Each field has a
38923 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38927 <flags id="@var{id}" size="@var{size}">
38928 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38933 @subsection Registers
38936 Each register is represented as an element with this form:
38939 <reg name="@var{name}"
38940 bitsize="@var{size}"
38941 @r{[}regnum="@var{num}"@r{]}
38942 @r{[}save-restore="@var{save-restore}"@r{]}
38943 @r{[}type="@var{type}"@r{]}
38944 @r{[}group="@var{group}"@r{]}/>
38948 The components are as follows:
38953 The register's name; it must be unique within the target description.
38956 The register's size, in bits.
38959 The register's number. If omitted, a register's number is one greater
38960 than that of the previous register (either in the current feature or in
38961 a preceding feature); the first register in the target description
38962 defaults to zero. This register number is used to read or write
38963 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38964 packets, and registers appear in the @code{g} and @code{G} packets
38965 in order of increasing register number.
38968 Whether the register should be preserved across inferior function
38969 calls; this must be either @code{yes} or @code{no}. The default is
38970 @code{yes}, which is appropriate for most registers except for
38971 some system control registers; this is not related to the target's
38975 The type of the register. It may be a predefined type, a type
38976 defined in the current feature, or one of the special types @code{int}
38977 and @code{float}. @code{int} is an integer type of the correct size
38978 for @var{bitsize}, and @code{float} is a floating point type (in the
38979 architecture's normal floating point format) of the correct size for
38980 @var{bitsize}. The default is @code{int}.
38983 The register group to which this register belongs. It must
38984 be either @code{general}, @code{float}, or @code{vector}. If no
38985 @var{group} is specified, @value{GDBN} will not display the register
38986 in @code{info registers}.
38990 @node Predefined Target Types
38991 @section Predefined Target Types
38992 @cindex target descriptions, predefined types
38994 Type definitions in the self-description can build up composite types
38995 from basic building blocks, but can not define fundamental types. Instead,
38996 standard identifiers are provided by @value{GDBN} for the fundamental
38997 types. The currently supported types are:
39006 Signed integer types holding the specified number of bits.
39013 Unsigned integer types holding the specified number of bits.
39017 Pointers to unspecified code and data. The program counter and
39018 any dedicated return address register may be marked as code
39019 pointers; printing a code pointer converts it into a symbolic
39020 address. The stack pointer and any dedicated address registers
39021 may be marked as data pointers.
39024 Single precision IEEE floating point.
39027 Double precision IEEE floating point.
39030 The 12-byte extended precision format used by ARM FPA registers.
39033 The 10-byte extended precision format used by x87 registers.
39036 32bit @sc{eflags} register used by x86.
39039 32bit @sc{mxcsr} register used by x86.
39043 @node Standard Target Features
39044 @section Standard Target Features
39045 @cindex target descriptions, standard features
39047 A target description must contain either no registers or all the
39048 target's registers. If the description contains no registers, then
39049 @value{GDBN} will assume a default register layout, selected based on
39050 the architecture. If the description contains any registers, the
39051 default layout will not be used; the standard registers must be
39052 described in the target description, in such a way that @value{GDBN}
39053 can recognize them.
39055 This is accomplished by giving specific names to feature elements
39056 which contain standard registers. @value{GDBN} will look for features
39057 with those names and verify that they contain the expected registers;
39058 if any known feature is missing required registers, or if any required
39059 feature is missing, @value{GDBN} will reject the target
39060 description. You can add additional registers to any of the
39061 standard features --- @value{GDBN} will display them just as if
39062 they were added to an unrecognized feature.
39064 This section lists the known features and their expected contents.
39065 Sample XML documents for these features are included in the
39066 @value{GDBN} source tree, in the directory @file{gdb/features}.
39068 Names recognized by @value{GDBN} should include the name of the
39069 company or organization which selected the name, and the overall
39070 architecture to which the feature applies; so e.g.@: the feature
39071 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39073 The names of registers are not case sensitive for the purpose
39074 of recognizing standard features, but @value{GDBN} will only display
39075 registers using the capitalization used in the description.
39078 * AArch64 Features::
39083 * Nios II Features::
39084 * PowerPC Features::
39085 * S/390 and System z Features::
39090 @node AArch64 Features
39091 @subsection AArch64 Features
39092 @cindex target descriptions, AArch64 features
39094 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39095 targets. It should contain registers @samp{x0} through @samp{x30},
39096 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39098 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39099 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39103 @subsection ARM Features
39104 @cindex target descriptions, ARM features
39106 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39108 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39109 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39111 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39112 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39113 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39116 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39117 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39119 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39120 it should contain at least registers @samp{wR0} through @samp{wR15} and
39121 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39122 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39124 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39125 should contain at least registers @samp{d0} through @samp{d15}. If
39126 they are present, @samp{d16} through @samp{d31} should also be included.
39127 @value{GDBN} will synthesize the single-precision registers from
39128 halves of the double-precision registers.
39130 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39131 need to contain registers; it instructs @value{GDBN} to display the
39132 VFP double-precision registers as vectors and to synthesize the
39133 quad-precision registers from pairs of double-precision registers.
39134 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39135 be present and include 32 double-precision registers.
39137 @node i386 Features
39138 @subsection i386 Features
39139 @cindex target descriptions, i386 features
39141 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39142 targets. It should describe the following registers:
39146 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39148 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39150 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39151 @samp{fs}, @samp{gs}
39153 @samp{st0} through @samp{st7}
39155 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39156 @samp{foseg}, @samp{fooff} and @samp{fop}
39159 The register sets may be different, depending on the target.
39161 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39162 describe registers:
39166 @samp{xmm0} through @samp{xmm7} for i386
39168 @samp{xmm0} through @samp{xmm15} for amd64
39173 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39174 @samp{org.gnu.gdb.i386.sse} feature. It should
39175 describe the upper 128 bits of @sc{ymm} registers:
39179 @samp{ymm0h} through @samp{ymm7h} for i386
39181 @samp{ymm0h} through @samp{ymm15h} for amd64
39184 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
39185 Memory Protection Extension (MPX). It should describe the following registers:
39189 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
39191 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
39194 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
39195 describe a single register, @samp{orig_eax}.
39197 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
39198 @samp{org.gnu.gdb.i386.avx} feature. It should
39199 describe additional @sc{xmm} registers:
39203 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
39206 It should describe the upper 128 bits of additional @sc{ymm} registers:
39210 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
39214 describe the upper 256 bits of @sc{zmm} registers:
39218 @samp{zmm0h} through @samp{zmm7h} for i386.
39220 @samp{zmm0h} through @samp{zmm15h} for amd64.
39224 describe the additional @sc{zmm} registers:
39228 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
39231 @node MIPS Features
39232 @subsection @acronym{MIPS} Features
39233 @cindex target descriptions, @acronym{MIPS} features
39235 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
39236 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
39237 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
39240 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
39241 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
39242 registers. They may be 32-bit or 64-bit depending on the target.
39244 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
39245 it may be optional in a future version of @value{GDBN}. It should
39246 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
39247 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
39249 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
39250 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
39251 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
39252 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
39254 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
39255 contain a single register, @samp{restart}, which is used by the
39256 Linux kernel to control restartable syscalls.
39258 @node M68K Features
39259 @subsection M68K Features
39260 @cindex target descriptions, M68K features
39263 @item @samp{org.gnu.gdb.m68k.core}
39264 @itemx @samp{org.gnu.gdb.coldfire.core}
39265 @itemx @samp{org.gnu.gdb.fido.core}
39266 One of those features must be always present.
39267 The feature that is present determines which flavor of m68k is
39268 used. The feature that is present should contain registers
39269 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
39270 @samp{sp}, @samp{ps} and @samp{pc}.
39272 @item @samp{org.gnu.gdb.coldfire.fp}
39273 This feature is optional. If present, it should contain registers
39274 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
39278 @node Nios II Features
39279 @subsection Nios II Features
39280 @cindex target descriptions, Nios II features
39282 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
39283 targets. It should contain the 32 core registers (@samp{zero},
39284 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
39285 @samp{pc}, and the 16 control registers (@samp{status} through
39288 @node PowerPC Features
39289 @subsection PowerPC Features
39290 @cindex target descriptions, PowerPC features
39292 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
39293 targets. It should contain registers @samp{r0} through @samp{r31},
39294 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
39295 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
39297 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
39298 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
39300 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
39301 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
39304 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
39305 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
39306 will combine these registers with the floating point registers
39307 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
39308 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
39309 through @samp{vs63}, the set of vector registers for POWER7.
39311 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
39312 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
39313 @samp{spefscr}. SPE targets should provide 32-bit registers in
39314 @samp{org.gnu.gdb.power.core} and provide the upper halves in
39315 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
39316 these to present registers @samp{ev0} through @samp{ev31} to the
39319 @node S/390 and System z Features
39320 @subsection S/390 and System z Features
39321 @cindex target descriptions, S/390 features
39322 @cindex target descriptions, System z features
39324 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
39325 System z targets. It should contain the PSW and the 16 general
39326 registers. In particular, System z targets should provide the 64-bit
39327 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
39328 S/390 targets should provide the 32-bit versions of these registers.
39329 A System z target that runs in 31-bit addressing mode should provide
39330 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
39331 register's upper halves @samp{r0h} through @samp{r15h}, and their
39332 lower halves @samp{r0l} through @samp{r15l}.
39334 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
39335 contain the 64-bit registers @samp{f0} through @samp{f15}, and
39338 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
39339 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
39341 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
39342 contain the register @samp{orig_r2}, which is 64-bit wide on System z
39343 targets and 32-bit otherwise. In addition, the feature may contain
39344 the @samp{last_break} register, whose width depends on the addressing
39345 mode, as well as the @samp{system_call} register, which is always
39348 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
39349 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
39350 @samp{atia}, and @samp{tr0} through @samp{tr15}.
39352 @node TIC6x Features
39353 @subsection TMS320C6x Features
39354 @cindex target descriptions, TIC6x features
39355 @cindex target descriptions, TMS320C6x features
39356 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
39357 targets. It should contain registers @samp{A0} through @samp{A15},
39358 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
39360 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
39361 contain registers @samp{A16} through @samp{A31} and @samp{B16}
39362 through @samp{B31}.
39364 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
39365 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
39367 @node Operating System Information
39368 @appendix Operating System Information
39369 @cindex operating system information
39375 Users of @value{GDBN} often wish to obtain information about the state of
39376 the operating system running on the target---for example the list of
39377 processes, or the list of open files. This section describes the
39378 mechanism that makes it possible. This mechanism is similar to the
39379 target features mechanism (@pxref{Target Descriptions}), but focuses
39380 on a different aspect of target.
39382 Operating system information is retrived from the target via the
39383 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
39384 read}). The object name in the request should be @samp{osdata}, and
39385 the @var{annex} identifies the data to be fetched.
39388 @appendixsection Process list
39389 @cindex operating system information, process list
39391 When requesting the process list, the @var{annex} field in the
39392 @samp{qXfer} request should be @samp{processes}. The returned data is
39393 an XML document. The formal syntax of this document is defined in
39394 @file{gdb/features/osdata.dtd}.
39396 An example document is:
39399 <?xml version="1.0"?>
39400 <!DOCTYPE target SYSTEM "osdata.dtd">
39401 <osdata type="processes">
39403 <column name="pid">1</column>
39404 <column name="user">root</column>
39405 <column name="command">/sbin/init</column>
39406 <column name="cores">1,2,3</column>
39411 Each item should include a column whose name is @samp{pid}. The value
39412 of that column should identify the process on the target. The
39413 @samp{user} and @samp{command} columns are optional, and will be
39414 displayed by @value{GDBN}. The @samp{cores} column, if present,
39415 should contain a comma-separated list of cores that this process
39416 is running on. Target may provide additional columns,
39417 which @value{GDBN} currently ignores.
39419 @node Trace File Format
39420 @appendix Trace File Format
39421 @cindex trace file format
39423 The trace file comes in three parts: a header, a textual description
39424 section, and a trace frame section with binary data.
39426 The header has the form @code{\x7fTRACE0\n}. The first byte is
39427 @code{0x7f} so as to indicate that the file contains binary data,
39428 while the @code{0} is a version number that may have different values
39431 The description section consists of multiple lines of @sc{ascii} text
39432 separated by newline characters (@code{0xa}). The lines may include a
39433 variety of optional descriptive or context-setting information, such
39434 as tracepoint definitions or register set size. @value{GDBN} will
39435 ignore any line that it does not recognize. An empty line marks the end
39438 @c FIXME add some specific types of data
39440 The trace frame section consists of a number of consecutive frames.
39441 Each frame begins with a two-byte tracepoint number, followed by a
39442 four-byte size giving the amount of data in the frame. The data in
39443 the frame consists of a number of blocks, each introduced by a
39444 character indicating its type (at least register, memory, and trace
39445 state variable). The data in this section is raw binary, not a
39446 hexadecimal or other encoding; its endianness matches the target's
39449 @c FIXME bi-arch may require endianness/arch info in description section
39452 @item R @var{bytes}
39453 Register block. The number and ordering of bytes matches that of a
39454 @code{g} packet in the remote protocol. Note that these are the
39455 actual bytes, in target order and @value{GDBN} register order, not a
39456 hexadecimal encoding.
39458 @item M @var{address} @var{length} @var{bytes}...
39459 Memory block. This is a contiguous block of memory, at the 8-byte
39460 address @var{address}, with a 2-byte length @var{length}, followed by
39461 @var{length} bytes.
39463 @item V @var{number} @var{value}
39464 Trace state variable block. This records the 8-byte signed value
39465 @var{value} of trace state variable numbered @var{number}.
39469 Future enhancements of the trace file format may include additional types
39472 @node Index Section Format
39473 @appendix @code{.gdb_index} section format
39474 @cindex .gdb_index section format
39475 @cindex index section format
39477 This section documents the index section that is created by @code{save
39478 gdb-index} (@pxref{Index Files}). The index section is
39479 DWARF-specific; some knowledge of DWARF is assumed in this
39482 The mapped index file format is designed to be directly
39483 @code{mmap}able on any architecture. In most cases, a datum is
39484 represented using a little-endian 32-bit integer value, called an
39485 @code{offset_type}. Big endian machines must byte-swap the values
39486 before using them. Exceptions to this rule are noted. The data is
39487 laid out such that alignment is always respected.
39489 A mapped index consists of several areas, laid out in order.
39493 The file header. This is a sequence of values, of @code{offset_type}
39494 unless otherwise noted:
39498 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
39499 Version 4 uses a different hashing function from versions 5 and 6.
39500 Version 6 includes symbols for inlined functions, whereas versions 4
39501 and 5 do not. Version 7 adds attributes to the CU indices in the
39502 symbol table. Version 8 specifies that symbols from DWARF type units
39503 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
39504 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
39506 @value{GDBN} will only read version 4, 5, or 6 indices
39507 by specifying @code{set use-deprecated-index-sections on}.
39508 GDB has a workaround for potentially broken version 7 indices so it is
39509 currently not flagged as deprecated.
39512 The offset, from the start of the file, of the CU list.
39515 The offset, from the start of the file, of the types CU list. Note
39516 that this area can be empty, in which case this offset will be equal
39517 to the next offset.
39520 The offset, from the start of the file, of the address area.
39523 The offset, from the start of the file, of the symbol table.
39526 The offset, from the start of the file, of the constant pool.
39530 The CU list. This is a sequence of pairs of 64-bit little-endian
39531 values, sorted by the CU offset. The first element in each pair is
39532 the offset of a CU in the @code{.debug_info} section. The second
39533 element in each pair is the length of that CU. References to a CU
39534 elsewhere in the map are done using a CU index, which is just the
39535 0-based index into this table. Note that if there are type CUs, then
39536 conceptually CUs and type CUs form a single list for the purposes of
39540 The types CU list. This is a sequence of triplets of 64-bit
39541 little-endian values. In a triplet, the first value is the CU offset,
39542 the second value is the type offset in the CU, and the third value is
39543 the type signature. The types CU list is not sorted.
39546 The address area. The address area consists of a sequence of address
39547 entries. Each address entry has three elements:
39551 The low address. This is a 64-bit little-endian value.
39554 The high address. This is a 64-bit little-endian value. Like
39555 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39558 The CU index. This is an @code{offset_type} value.
39562 The symbol table. This is an open-addressed hash table. The size of
39563 the hash table is always a power of 2.
39565 Each slot in the hash table consists of a pair of @code{offset_type}
39566 values. The first value is the offset of the symbol's name in the
39567 constant pool. The second value is the offset of the CU vector in the
39570 If both values are 0, then this slot in the hash table is empty. This
39571 is ok because while 0 is a valid constant pool index, it cannot be a
39572 valid index for both a string and a CU vector.
39574 The hash value for a table entry is computed by applying an
39575 iterative hash function to the symbol's name. Starting with an
39576 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39577 the string is incorporated into the hash using the formula depending on the
39582 The formula is @code{r = r * 67 + c - 113}.
39584 @item Versions 5 to 7
39585 The formula is @code{r = r * 67 + tolower (c) - 113}.
39588 The terminating @samp{\0} is not incorporated into the hash.
39590 The step size used in the hash table is computed via
39591 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39592 value, and @samp{size} is the size of the hash table. The step size
39593 is used to find the next candidate slot when handling a hash
39596 The names of C@t{++} symbols in the hash table are canonicalized. We
39597 don't currently have a simple description of the canonicalization
39598 algorithm; if you intend to create new index sections, you must read
39602 The constant pool. This is simply a bunch of bytes. It is organized
39603 so that alignment is correct: CU vectors are stored first, followed by
39606 A CU vector in the constant pool is a sequence of @code{offset_type}
39607 values. The first value is the number of CU indices in the vector.
39608 Each subsequent value is the index and symbol attributes of a CU in
39609 the CU list. This element in the hash table is used to indicate which
39610 CUs define the symbol and how the symbol is used.
39611 See below for the format of each CU index+attributes entry.
39613 A string in the constant pool is zero-terminated.
39616 Attributes were added to CU index values in @code{.gdb_index} version 7.
39617 If a symbol has multiple uses within a CU then there is one
39618 CU index+attributes value for each use.
39620 The format of each CU index+attributes entry is as follows
39626 This is the index of the CU in the CU list.
39628 These bits are reserved for future purposes and must be zero.
39630 The kind of the symbol in the CU.
39634 This value is reserved and should not be used.
39635 By reserving zero the full @code{offset_type} value is backwards compatible
39636 with previous versions of the index.
39638 The symbol is a type.
39640 The symbol is a variable or an enum value.
39642 The symbol is a function.
39644 Any other kind of symbol.
39646 These values are reserved.
39650 This bit is zero if the value is global and one if it is static.
39652 The determination of whether a symbol is global or static is complicated.
39653 The authorative reference is the file @file{dwarf2read.c} in
39654 @value{GDBN} sources.
39658 This pseudo-code describes the computation of a symbol's kind and
39659 global/static attributes in the index.
39662 is_external = get_attribute (die, DW_AT_external);
39663 language = get_attribute (cu_die, DW_AT_language);
39666 case DW_TAG_typedef:
39667 case DW_TAG_base_type:
39668 case DW_TAG_subrange_type:
39672 case DW_TAG_enumerator:
39674 is_static = (language != CPLUS && language != JAVA);
39676 case DW_TAG_subprogram:
39678 is_static = ! (is_external || language == ADA);
39680 case DW_TAG_constant:
39682 is_static = ! is_external;
39684 case DW_TAG_variable:
39686 is_static = ! is_external;
39688 case DW_TAG_namespace:
39692 case DW_TAG_class_type:
39693 case DW_TAG_interface_type:
39694 case DW_TAG_structure_type:
39695 case DW_TAG_union_type:
39696 case DW_TAG_enumeration_type:
39698 is_static = (language != CPLUS && language != JAVA);
39706 @appendix Manual pages
39710 * gdb man:: The GNU Debugger man page
39711 * gdbserver man:: Remote Server for the GNU Debugger man page
39712 * gcore man:: Generate a core file of a running program
39713 * gdbinit man:: gdbinit scripts
39719 @c man title gdb The GNU Debugger
39721 @c man begin SYNOPSIS gdb
39722 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
39723 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
39724 [@option{-b}@w{ }@var{bps}]
39725 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
39726 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
39727 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
39728 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
39729 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
39732 @c man begin DESCRIPTION gdb
39733 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
39734 going on ``inside'' another program while it executes -- or what another
39735 program was doing at the moment it crashed.
39737 @value{GDBN} can do four main kinds of things (plus other things in support of
39738 these) to help you catch bugs in the act:
39742 Start your program, specifying anything that might affect its behavior.
39745 Make your program stop on specified conditions.
39748 Examine what has happened, when your program has stopped.
39751 Change things in your program, so you can experiment with correcting the
39752 effects of one bug and go on to learn about another.
39755 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
39758 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
39759 commands from the terminal until you tell it to exit with the @value{GDBN}
39760 command @code{quit}. You can get online help from @value{GDBN} itself
39761 by using the command @code{help}.
39763 You can run @code{gdb} with no arguments or options; but the most
39764 usual way to start @value{GDBN} is with one argument or two, specifying an
39765 executable program as the argument:
39771 You can also start with both an executable program and a core file specified:
39777 You can, instead, specify a process ID as a second argument, if you want
39778 to debug a running process:
39786 would attach @value{GDBN} to process @code{1234} (unless you also have a file
39787 named @file{1234}; @value{GDBN} does check for a core file first).
39788 With option @option{-p} you can omit the @var{program} filename.
39790 Here are some of the most frequently needed @value{GDBN} commands:
39792 @c pod2man highlights the right hand side of the @item lines.
39794 @item break [@var{file}:]@var{functiop}
39795 Set a breakpoint at @var{function} (in @var{file}).
39797 @item run [@var{arglist}]
39798 Start your program (with @var{arglist}, if specified).
39801 Backtrace: display the program stack.
39803 @item print @var{expr}
39804 Display the value of an expression.
39807 Continue running your program (after stopping, e.g. at a breakpoint).
39810 Execute next program line (after stopping); step @emph{over} any
39811 function calls in the line.
39813 @item edit [@var{file}:]@var{function}
39814 look at the program line where it is presently stopped.
39816 @item list [@var{file}:]@var{function}
39817 type the text of the program in the vicinity of where it is presently stopped.
39820 Execute next program line (after stopping); step @emph{into} any
39821 function calls in the line.
39823 @item help [@var{name}]
39824 Show information about @value{GDBN} command @var{name}, or general information
39825 about using @value{GDBN}.
39828 Exit from @value{GDBN}.
39832 For full details on @value{GDBN},
39833 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39834 by Richard M. Stallman and Roland H. Pesch. The same text is available online
39835 as the @code{gdb} entry in the @code{info} program.
39839 @c man begin OPTIONS gdb
39840 Any arguments other than options specify an executable
39841 file and core file (or process ID); that is, the first argument
39842 encountered with no
39843 associated option flag is equivalent to a @option{-se} option, and the second,
39844 if any, is equivalent to a @option{-c} option if it's the name of a file.
39846 both long and short forms; both are shown here. The long forms are also
39847 recognized if you truncate them, so long as enough of the option is
39848 present to be unambiguous. (If you prefer, you can flag option
39849 arguments with @option{+} rather than @option{-}, though we illustrate the
39850 more usual convention.)
39852 All the options and command line arguments you give are processed
39853 in sequential order. The order makes a difference when the @option{-x}
39859 List all options, with brief explanations.
39861 @item -symbols=@var{file}
39862 @itemx -s @var{file}
39863 Read symbol table from file @var{file}.
39866 Enable writing into executable and core files.
39868 @item -exec=@var{file}
39869 @itemx -e @var{file}
39870 Use file @var{file} as the executable file to execute when
39871 appropriate, and for examining pure data in conjunction with a core
39874 @item -se=@var{file}
39875 Read symbol table from file @var{file} and use it as the executable
39878 @item -core=@var{file}
39879 @itemx -c @var{file}
39880 Use file @var{file} as a core dump to examine.
39882 @item -command=@var{file}
39883 @itemx -x @var{file}
39884 Execute @value{GDBN} commands from file @var{file}.
39886 @item -ex @var{command}
39887 Execute given @value{GDBN} @var{command}.
39889 @item -directory=@var{directory}
39890 @itemx -d @var{directory}
39891 Add @var{directory} to the path to search for source files.
39894 Do not execute commands from @file{~/.gdbinit}.
39898 Do not execute commands from any @file{.gdbinit} initialization files.
39902 ``Quiet''. Do not print the introductory and copyright messages. These
39903 messages are also suppressed in batch mode.
39906 Run in batch mode. Exit with status @code{0} after processing all the command
39907 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
39908 Exit with nonzero status if an error occurs in executing the @value{GDBN}
39909 commands in the command files.
39911 Batch mode may be useful for running @value{GDBN} as a filter, for example to
39912 download and run a program on another computer; in order to make this
39913 more useful, the message
39916 Program exited normally.
39920 (which is ordinarily issued whenever a program running under @value{GDBN} control
39921 terminates) is not issued when running in batch mode.
39923 @item -cd=@var{directory}
39924 Run @value{GDBN} using @var{directory} as its working directory,
39925 instead of the current directory.
39929 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
39930 @value{GDBN} to output the full file name and line number in a standard,
39931 recognizable fashion each time a stack frame is displayed (which
39932 includes each time the program stops). This recognizable format looks
39933 like two @samp{\032} characters, followed by the file name, line number
39934 and character position separated by colons, and a newline. The
39935 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
39936 characters as a signal to display the source code for the frame.
39939 Set the line speed (baud rate or bits per second) of any serial
39940 interface used by @value{GDBN} for remote debugging.
39942 @item -tty=@var{device}
39943 Run using @var{device} for your program's standard input and output.
39947 @c man begin SEEALSO gdb
39949 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
39950 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
39951 documentation are properly installed at your site, the command
39958 should give you access to the complete manual.
39960 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
39961 Richard M. Stallman and Roland H. Pesch, July 1991.
39965 @node gdbserver man
39966 @heading gdbserver man
39968 @c man title gdbserver Remote Server for the GNU Debugger
39970 @c man begin SYNOPSIS gdbserver
39971 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
39973 gdbserver --attach @var{comm} @var{pid}
39975 gdbserver --multi @var{comm}
39979 @c man begin DESCRIPTION gdbserver
39980 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
39981 than the one which is running the program being debugged.
39984 @subheading Usage (server (target) side)
39987 Usage (server (target) side):
39990 First, you need to have a copy of the program you want to debug put onto
39991 the target system. The program can be stripped to save space if needed, as
39992 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
39993 the @value{GDBN} running on the host system.
39995 To use the server, you log on to the target system, and run the @command{gdbserver}
39996 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
39997 your program, and (c) its arguments. The general syntax is:
40000 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40003 For example, using a serial port, you might say:
40007 @c @file would wrap it as F</dev/com1>.
40008 target> gdbserver /dev/com1 emacs foo.txt
40011 target> gdbserver @file{/dev/com1} emacs foo.txt
40015 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40016 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40017 waits patiently for the host @value{GDBN} to communicate with it.
40019 To use a TCP connection, you could say:
40022 target> gdbserver host:2345 emacs foo.txt
40025 This says pretty much the same thing as the last example, except that we are
40026 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40027 that we are expecting to see a TCP connection from @code{host} to local TCP port
40028 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40029 want for the port number as long as it does not conflict with any existing TCP
40030 ports on the target system. This same port number must be used in the host
40031 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40032 you chose a port number that conflicts with another service, @command{gdbserver} will
40033 print an error message and exit.
40035 @command{gdbserver} can also attach to running programs.
40036 This is accomplished via the @option{--attach} argument. The syntax is:
40039 target> gdbserver --attach @var{comm} @var{pid}
40042 @var{pid} is the process ID of a currently running process. It isn't
40043 necessary to point @command{gdbserver} at a binary for the running process.
40045 To start @code{gdbserver} without supplying an initial command to run
40046 or process ID to attach, use the @option{--multi} command line option.
40047 In such case you should connect using @kbd{target extended-remote} to start
40048 the program you want to debug.
40051 target> gdbserver --multi @var{comm}
40055 @subheading Usage (host side)
40061 You need an unstripped copy of the target program on your host system, since
40062 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40063 would, with the target program as the first argument. (You may need to use the
40064 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40065 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40066 new command you need to know about is @code{target remote}
40067 (or @code{target extended-remote}). Its argument is either
40068 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40069 descriptor. For example:
40073 @c @file would wrap it as F</dev/ttyb>.
40074 (gdb) target remote /dev/ttyb
40077 (gdb) target remote @file{/dev/ttyb}
40082 communicates with the server via serial line @file{/dev/ttyb}, and:
40085 (gdb) target remote the-target:2345
40089 communicates via a TCP connection to port 2345 on host `the-target', where
40090 you previously started up @command{gdbserver} with the same port number. Note that for
40091 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40092 command, otherwise you may get an error that looks something like
40093 `Connection refused'.
40095 @command{gdbserver} can also debug multiple inferiors at once,
40098 the @value{GDBN} manual in node @code{Inferiors and Programs}
40099 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40102 @ref{Inferiors and Programs}.
40104 In such case use the @code{extended-remote} @value{GDBN} command variant:
40107 (gdb) target extended-remote the-target:2345
40110 The @command{gdbserver} option @option{--multi} may or may not be used in such
40114 @c man begin OPTIONS gdbserver
40115 There are three different modes for invoking @command{gdbserver}:
40120 Debug a specific program specified by its program name:
40123 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40126 The @var{comm} parameter specifies how should the server communicate
40127 with @value{GDBN}; it is either a device name (to use a serial line),
40128 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40129 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40130 debug in @var{prog}. Any remaining arguments will be passed to the
40131 program verbatim. When the program exits, @value{GDBN} will close the
40132 connection, and @code{gdbserver} will exit.
40135 Debug a specific program by specifying the process ID of a running
40139 gdbserver --attach @var{comm} @var{pid}
40142 The @var{comm} parameter is as described above. Supply the process ID
40143 of a running program in @var{pid}; @value{GDBN} will do everything
40144 else. Like with the previous mode, when the process @var{pid} exits,
40145 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40148 Multi-process mode -- debug more than one program/process:
40151 gdbserver --multi @var{comm}
40154 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40155 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40156 close the connection when a process being debugged exits, so you can
40157 debug several processes in the same session.
40160 In each of the modes you may specify these options:
40165 List all options, with brief explanations.
40168 This option causes @command{gdbserver} to print its version number and exit.
40171 @command{gdbserver} will attach to a running program. The syntax is:
40174 target> gdbserver --attach @var{comm} @var{pid}
40177 @var{pid} is the process ID of a currently running process. It isn't
40178 necessary to point @command{gdbserver} at a binary for the running process.
40181 To start @code{gdbserver} without supplying an initial command to run
40182 or process ID to attach, use this command line option.
40183 Then you can connect using @kbd{target extended-remote} and start
40184 the program you want to debug. The syntax is:
40187 target> gdbserver --multi @var{comm}
40191 Instruct @code{gdbserver} to display extra status information about the debugging
40193 This option is intended for @code{gdbserver} development and for bug reports to
40196 @item --remote-debug
40197 Instruct @code{gdbserver} to display remote protocol debug output.
40198 This option is intended for @code{gdbserver} development and for bug reports to
40201 @item --debug-format=option1@r{[},option2,...@r{]}
40202 Instruct @code{gdbserver} to include extra information in each line
40203 of debugging output.
40204 @xref{Other Command-Line Arguments for gdbserver}.
40207 Specify a wrapper to launch programs
40208 for debugging. The option should be followed by the name of the
40209 wrapper, then any command-line arguments to pass to the wrapper, then
40210 @kbd{--} indicating the end of the wrapper arguments.
40213 By default, @command{gdbserver} keeps the listening TCP port open, so that
40214 additional connections are possible. However, if you start @code{gdbserver}
40215 with the @option{--once} option, it will stop listening for any further
40216 connection attempts after connecting to the first @value{GDBN} session.
40218 @c --disable-packet is not documented for users.
40220 @c --disable-randomization and --no-disable-randomization are superseded by
40221 @c QDisableRandomization.
40226 @c man begin SEEALSO gdbserver
40228 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40229 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40230 documentation are properly installed at your site, the command
40236 should give you access to the complete manual.
40238 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40239 Richard M. Stallman and Roland H. Pesch, July 1991.
40246 @c man title gcore Generate a core file of a running program
40249 @c man begin SYNOPSIS gcore
40250 gcore [-o @var{filename}] @var{pid}
40254 @c man begin DESCRIPTION gcore
40255 Generate a core dump of a running program with process ID @var{pid}.
40256 Produced file is equivalent to a kernel produced core file as if the process
40257 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
40258 limit). Unlike after a crash, after @command{gcore} the program remains
40259 running without any change.
40262 @c man begin OPTIONS gcore
40264 @item -o @var{filename}
40265 The optional argument
40266 @var{filename} specifies the file name where to put the core dump.
40267 If not specified, the file name defaults to @file{core.@var{pid}},
40268 where @var{pid} is the running program process ID.
40272 @c man begin SEEALSO gcore
40274 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40275 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40276 documentation are properly installed at your site, the command
40283 should give you access to the complete manual.
40285 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40286 Richard M. Stallman and Roland H. Pesch, July 1991.
40293 @c man title gdbinit GDB initialization scripts
40296 @c man begin SYNOPSIS gdbinit
40297 @ifset SYSTEM_GDBINIT
40298 @value{SYSTEM_GDBINIT}
40307 @c man begin DESCRIPTION gdbinit
40308 These files contain @value{GDBN} commands to automatically execute during
40309 @value{GDBN} startup. The lines of contents are canned sequences of commands,
40312 the @value{GDBN} manual in node @code{Sequences}
40313 -- shell command @code{info -f gdb -n Sequences}.
40319 Please read more in
40321 the @value{GDBN} manual in node @code{Startup}
40322 -- shell command @code{info -f gdb -n Startup}.
40329 @ifset SYSTEM_GDBINIT
40330 @item @value{SYSTEM_GDBINIT}
40332 @ifclear SYSTEM_GDBINIT
40333 @item (not enabled with @code{--with-system-gdbinit} during compilation)
40335 System-wide initialization file. It is executed unless user specified
40336 @value{GDBN} option @code{-nx} or @code{-n}.
40339 the @value{GDBN} manual in node @code{System-wide configuration}
40340 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
40343 @ref{System-wide configuration}.
40347 User initialization file. It is executed unless user specified
40348 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
40351 Initialization file for current directory. It may need to be enabled with
40352 @value{GDBN} security command @code{set auto-load local-gdbinit}.
40355 the @value{GDBN} manual in node @code{Init File in the Current Directory}
40356 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
40359 @ref{Init File in the Current Directory}.
40364 @c man begin SEEALSO gdbinit
40366 gdb(1), @code{info -f gdb -n Startup}
40368 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40369 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40370 documentation are properly installed at your site, the command
40376 should give you access to the complete manual.
40378 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40379 Richard M. Stallman and Roland H. Pesch, July 1991.
40385 @node GNU Free Documentation License
40386 @appendix GNU Free Documentation License
40389 @node Concept Index
40390 @unnumbered Concept Index
40394 @node Command and Variable Index
40395 @unnumbered Command, Variable, and Function Index
40400 % I think something like @@colophon should be in texinfo. In the
40402 \long\def\colophon{\hbox to0pt{}\vfill
40403 \centerline{The body of this manual is set in}
40404 \centerline{\fontname\tenrm,}
40405 \centerline{with headings in {\bf\fontname\tenbf}}
40406 \centerline{and examples in {\tt\fontname\tentt}.}
40407 \centerline{{\it\fontname\tenit\/},}
40408 \centerline{{\bf\fontname\tenbf}, and}
40409 \centerline{{\sl\fontname\tensl\/}}
40410 \centerline{are used for emphasis.}\vfill}
40412 % Blame: doc@@cygnus.com, 1991.